JP2011101952A - Resin-coated metal sheet for container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin-coated metal sheet for a container which is excellent in processability, adhesion, and wounded part corrosion resistance. <P>SOLUTION: The resin-coated metal sheet adheres to a metal sheet and has a resin coating layer (A) having a resin layer (a1) containing a polyester resin containing components (1)-(3): (1) a block-free isocyanate compound: a content in which the ratio (α)/(β) between the mole number (α) of an NCO group in the block-free isocyanate compound and the mole number (β) of an OH group in the polyester resin and an epoxy resin in the resin layer (a1) is 0.5-5.0, (2) the epoxy resin: the softening point is at least 80°C, and a content to be 1-20 mass% to the resin layer (a1), and (3) metal ion exchange silica: a content to be 1-25 mass% to the resin layer (a1) as a main component on at least one surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

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, 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, a film laminated steel sheet obtained by laminating a thermoplastic resin film on a heated steel sheet has been developed instead of a coated steel sheet, and is currently used industrially as a food canning material. 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, areas where remarkable economic development is occurring, such as BRIC countries, are attracting attention as markets where demand is expected to expand. The future increase in demand is certain. In view of this global market, film laminated steel 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 steel sheet needs further performance improvement for the following reasons. Specifically, it is necessary to greatly improve the corrosion resistance, particularly the corrosion resistance of the scratched part.
Since the corrosion resistance of the film-laminated steel sheet depends on the insulating properties of the film, it is essential to ensure the coverage. 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 steel sheets 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 steel sheets in the canning line (for example, slipping of transport rolls) occur. do not do. Therefore, the film-laminated steel plate is hardly damaged so as to penetrate the film, and the film continues to cover the steel plate after can molding, and maintains excellent corrosion resistance. 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 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-makers around the world, we will become a global standard without the need to improve the corrosion resistance of film-laminated steel sheets. Cannot 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 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. In addition, since the technique is merely an increase in the film thickness, the industrial utility value is extremely low.

Japanese Patent Laid-Open No. 7-256819 Japanese Patent Laid-Open No. 10-264305

  In view of such circumstances, an object of the present invention is to provide a resin-coated metal plate for a container that is compatible with many 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, the following findings were obtained.
The resin layer (a1) in close contact with the metal plate contains specific block-free isocyanate and epoxy resin to ensure deep drawability, adhesion after processing and retorting, impact resistance, and metal ion exchange. By including silica in a certain range, it is possible to have excellent scratch corrosion resistance.
The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A resin coating layer (A) having a multilayer structure mainly composed of a polyester resin is provided on at least one surface of a metal plate, and the resin coating layer (A) is in close contact with the metal plate surface and is A resin-coated metal sheet for containers, comprising a resin layer (a1) mainly composed of a polyester resin containing the component (c).
(A) Block-free isocyanate compound: ratio of mole number (α) of NCO groups in the block-free isocyanate compound to mole number (β) of OH groups in the polyester resin and epoxy resin in the resin layer (a1) (Α) / (β) content of 0.5 to 5.0 (b) Epoxy resin: softening point is 80 ° C. or higher, and is 1 to 20 mass% with respect to the resin layer (a1). Content (c) Metal ion exchanged silica: Content of 1 to 25 mass% with respect to the resin layer (a1) [2] In the above [1], the resin coating layer (A) is mainly composed of a polyester resin. A resin-coated metal sheet for containers, comprising: the resin layer (a1) to be formed; and a polyester film (a2) formed on the upper layer of the resin layer (a1).
[3] The resin-coated metal plate for containers according to [1] or [2], wherein the amount of the resin layer (a1) attached is 0.1 to 5.0 g / m ² .
[4] The resin-coated metal plate for containers according to any one of [1] to [3], wherein the epoxy resin in the resin layer (a1) is a novolac type epoxy resin.
[5] In any one of [1] to [4], the metal ion exchange silica contained in the resin layer (a1) is one or two selected from zinc ion exchange silica and calcium ion exchange silica. A resin-coated metal plate for containers.
[6] In any one of [1] to [5], the resin layer (a1) contains a hydrophobic polyol in a range of 5 to 20 mass% with respect to the polyester resin. Coated metal plate.
[7] In any one of the above [2] to [6], the polyester film (a2) is a biaxially stretched polyester in which 93 mass% or more of the constituent units of the polyester resin are ethylene terephthalate units and / or ethylene naphthalate units. A resin-coated metal sheet for containers, which is a film, and the biaxially stretched polyester film contains inorganic particles and / or organic particles.

  ADVANTAGE OF THE INVENTION According to this invention, the resin-coated metal plate for containers excellent in the workability and adhesiveness which are the basic performances required for food canning, and also excellent in scratch corrosion resistance can be obtained. And since the resin-coated metal plate for containers of the present invention has such characteristics, it can be used as a container material not only in the domestic market but also in every market in the world, mainly for canned foods and lids. It is.

It is a figure which shows the principal part of the lamination apparatus of a steel plate. (Example) It is a figure which shows the cross-section of a film laminated steel plate. (Example) It is a figure which shows the position of the crosscut damage | wound provided to the can trunk | drum. (Example) It is a figure which shows the method of measuring the maximum corrosion width from a crosscut damage | wound. (Example)

Hereinafter, the present invention will be described in detail.
The resin-coated metal plate for containers of the present invention has a resin coating layer (A) having a multilayer structure mainly composed of a polyester resin on at least one surface of the metal plate. The resin coating layer (A) is in close contact with the surface of the metal plate, and comprises a resin layer (a1) mainly composed of a polyester resin, and preferably a polyester film (a2) as an upper layer thereof. The resin layer (a1) contains the following specific components.
(A) Block-free isocyanate compound: ratio of mole number (α) of NCO groups in the block-free isocyanate compound to mole number (β) of OH groups in the polyester resin and epoxy resin in the resin layer (a1) (Α) / (β) content of 0.5 to 5.0 (b) Epoxy resin: softening point is 80 ° C. or higher, and is 1 to 20 mass% with respect to the resin layer (a1). Content (c) Metal ion exchanged silica: Content of 1 to 25 mass% with respect to the resin layer (a1) First, the resin-coated metal plate for containers of the present invention will be described.
As the metal plate that is the original plate of the resin-coated metal plate for containers of the present invention, aluminum plates and mild steel plates that are widely used as can materials can be used, and in particular, low-carbon steel cold-rolled steel plates are suitable. It is. And in this invention, since a rust prevention function of a plating film is fully obtained using a metal plate without using a plated steel plate, TFS (tin free steel), etc. as an original plate, plating processing can be omitted. Thus, the resin-coated steel sheet for containers according to the present invention can greatly contribute to the reduction of the risk of depletion of resources such as zinc and tin, which is one of the effects brought about by the present invention. However, the use of plating is not limited. For example, a surface-treated steel sheet such as TFS or tin-plated steel sheet can be used.

Next, the resin layer (a1) which adheres to the metal plate surface and has a polyester resin as a main component will be described.
The resin layer (a1) contains a polyester resin as a main component.
The resin layer (a1) is a resin layer containing 50 mass% or more of a polyester resin in a proportion of the components, and examples of the resin other than the polyester include a polyolefin resin.
The composition of the polyester resin layer which is the main component of the resin layer (a1) is typified by polyethylene terephthalate comprising terephthalic acid as the carboxylic acid component and ethylene glycol as the glycol component, but isophthalic acid and phthalic acid as other carboxylic acid components In addition, naphthalenedicarboxylic acid, adipic acid, and the like, and diethylene glycol, propanediol, propylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, and the like as other glycol components may be used.

  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 to 60 mol%, it becomes easy to secure preferable physical properties of the polyester resin as described later, and deep drawability and post-processing adhesion are improved. It is preferable because it functions as follows.

  As the glycol component, a low Tg (Tg = glass transition temperature) component having excellent flexibility such as ethylene glycol and propanediol and a rigid high Tg component having a ring structure such as neopentyl glycol and cyclohexanedimethanol are copolymerized. It is desirable to make it. This is because it is easy to ensure preferable thermophysical properties of the polyester resin described below, and the strength and flexibility 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.

Thermal properties (glass transition point, softening point) (preferred conditions)
As a thermophysical property of the polyester resin layer which is a main component of the resin layer (a1), a glass transition point of 30 ° C. to 85 ° C. and a softening point of 80 ° C. to 200 ° C. are preferable.
When the container-coated resin-coated metal plate is stored and transported, the glass transition point may be kept at a temperature of about 20 ° C. for a long time. Therefore, 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.
In addition, the retort sterilization treatment for food cans may take 1 hour or more at a high temperature of 80 ° C. or higher, and is required to have heat resistance in a temperature range of 80 ° C. or higher. For this reason, it is preferable that the softening point defined in JIS K2425 is 80 ° C. or higher, desirably 150 ° C. or higher. On the other hand, when the softening point exceeds 200 ° C., the fluidity of the resin is deteriorated, and the flexibility of the resin is insufficient in processes such as laminating with a steel plate and can manufacturing. Insufficient flexibility at the time of laminating deteriorates the adhesion to the steel sheet, and insufficient flexibility at the time of can manufacturing suppresses elongation deformation in the can height direction and causes the can body to rupture.

Molecular weight (preferred conditions)
The mass average molecular weight of the polyester resin is preferably 10,000 to 40,000, and particularly preferably 15,000 to 20,000. A polyester resin having such a mass average molecular weight is excellent in balance between workability and strength, and has good deep drawability and adhesion after forming. 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 treatment, the resin layer (a2) formed in the upper layer: against the heat shrinkage of the polyester film, the delamination (resin of the resin) from the trim end or the like (the upper end of the container before attaching the lid after forming the container) Peeling) can be suppressed. 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.

Next, the following (A), (B), and (C) contained in the resin layer (a1) will be described.
(A) Block-free isocyanate compound: ratio of mole number (α) of NCO groups in the block-free isocyanate compound to mole number (β) of OH groups in the polyester resin and epoxy resin in the resin layer (a1) ( Content (α) / (β) is 0.5 to 5.0 (b) Epoxy resin: Content (softening point is 80 ° C. or higher and 1 to 20 mass% with respect to the resin layer (a1)) C) Metal ion-exchanged silica: Content component (A): 1 to 25 mass% with respect to the resin layer (a1): Block-free isocyanate compound
In the present invention, the component (A) block-free isocyanate compound, that is, an isocyanate compound not blocked with a blocking agent is used. This is due to the following reason.
By not using the blocking agent, the free isocyanate group can react quickly with the functional group at the end of the polyester resin, the functional group at the end of the epoxy resin, or the functional group on the surface of the polyester film (a2). This makes it possible to polymerize by an isocyanate cross-linking reaction using a short heat treatment during lamination, greatly improving the strength and workability of the resin layer (a1), and being strong with the polyester film (a2). Good adhesion can be obtained. Examples of the isocyanate compound to be applied include hexamethylene diisocyanate, methylcyclohexane diisocyanate, and xylylene diisocyanate. Among these, the xylylene diisocyanate compound is most preferable from the viewpoints of adhesion and durability.
Here, the block free isocyanate compound includes the number of moles (α) of NCO groups (isocyanate groups) in the block free isocyanate compound and the number of moles of OH groups in the polyester resin and epoxy resin in the resin layer (a1) (β ) And the content (α) / (β) is 0.5 to 5.0. If it is less than 0.5, either the crosslinking reaction with the terminal functional group of the polyester resin and the epoxy resin or the crosslinking reaction with the functional group on the surface of the polyester film (a2) becomes insufficient, and the film peels off during can manufacturing. Or the material will tear. On the other hand, if (α) / (β) exceeds 5.0, the water resistance of the resin layer (a1) is lowered, and the polyester film (a2) may be peeled off from the can during the retort treatment. More preferable (α) / (β) is 1.0 to 3.0, and in this case, film peeling during the retort treatment can be particularly effectively suppressed.

Component (b): Epoxy resin By using the epoxy resin of the component (b), it is possible to improve adhesion to the metal plate and chemical stability in a corrosive environment. This is because the hydroxyl group in the epoxy resin forms a hydrogen bond with water adsorbing molecules existing on the surface of the metal plate, so that strong adhesion can be secured and the bond of the main chain is an ether bond. This is thought to be due to the stability to the base. As the epoxy resin, a novolac type epoxy resin and this modified epoxy resin are preferably used. In the production of the modified epoxy resin, the modification time is not limited, and it may be modified during the production of the epoxy resin or may be modified after the production of the epoxy resin.

  Here, as a thermophysical property of an epoxy resin, it is essential that the softening point defined in JIS K2425 is 80 ° C. or higher. As described above, the retort sterilization treatment for food cans may take 1 hour or more at a high temperature of 80 ° C. or higher, and heat resistance in this temperature range is required.

  Preferably it is 120 degreeC or more. On the other hand, when the temperature exceeds 200 ° C., the fluidity of the resin deteriorates, and the flexibility of the resin is insufficient at the time of laminating with a steel plate or at the time of can manufacturing. preferable.

  The content of the epoxy resin is in the range of 1 to 20 mass% with respect to the resin layer (a1). If the content is less than 1 mass%, almost no improvement in adhesion and corrosion resistance can be expected. On the other hand, when the content exceeds 20 mass%, the flexibility of the resin layer (a1) is lowered, and the film is peeled or the material is torn during canning. The content range of a preferable epoxy resin is 5-15 mass%. By setting it as the range of 5-15 mass%, polyester and an epoxy resin are moderately blended, and the outstanding performance (adhesion property, workability, corrosion resistance) can be obtained.

Examples of the novolac type epoxy resin include a phenol novolac type epoxy resin and a cresol novolac type epoxy resin. Of these, the cresol novolac type epoxy resin can be most suitably used. The cresol novolac type epoxy resin is characterized by being capable of increasing the crosslinking density as compared with the bisphenol type epoxy resin by being polyfunctionalized and being excellent in heat resistance and chemical stability.
As a commercial item of a cresol novolac epoxy resin, for example, Epicron N-680, 690, 695 manufactured by DIC Corporation can be exemplified.

Component (c): Metal ion exchange silica Metal ion exchange silica is silica particles in which metal ions are introduced into a fine porous silica carrier by ion exchange. Among these, calcium ion exchange silica and zinc ion exchange silica are preferable, and it is desirable to use a mixture of these. Calcium ions released from calcium ion-exchanged silica have an electrochemical action and a salt-forming action, and therefore have a function of forming a protective film and suppressing the progress of corrosion. Zinc ion-exchanged silica is also suitable because zinc ions have the same anticorrosive ability.
As content of a metal ion exchange silica, it is set as the range of 1-25 mass% with respect to the resin layer (a1). If the content is less than 1 mass%, a sufficient anticorrosive effect cannot be obtained. On the other hand, if it exceeds 25 mass%, the resin layer becomes stiff, the workability is greatly deteriorated, and the resin layer may be torn during can processing.
In addition, as the metal ion exchange silica used in the present invention, a generally known type in which calcium ions or zinc ions are ion exchanged with silanol groups on the silica surface can be used, and commercially available products can also be used. It is. As a commercial product, “SHIELDEX (registered trademark)” by WR Grace & Co. incorporates.

In order to improve the water resistance of the resin layer (a1) containing a hydrophobic polyol polyester resin as a main component, it is effective to contain a fatty acid-derived hydrophobic polyol in the polyester resin. Examples of hydrophobic polyols 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, the ester bond portion can be shielded from water, and film peeling in a humid environment such as retort treatment can be effectively prevented.
When the hydrophobic polyol is contained, the content thereof is preferably in the range of 5 to 20 mass% with respect to the polyester resin which is the main component of the resin layer (a1). If the content is less than 5 mass%, the effect of improving the water resistance cannot be sufficiently obtained. On the other hand, if the content exceeds 20 mass%, the surface free energy of the polyester resin is excessively reduced, so that the polyester film (a2) and the steel sheet are in close contact with each other. Sex may be inhibited. Moreover, from a viewpoint of making water resistance and adhesiveness compatible, a more preferable content is 7-15 mass%. Moreover, polyester polyol can be contained in the range which does not inhibit hydrophobicity. In this case, the hydrophobic polyol is preferably in the range of 50 mass% 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.

Additives: Colorant, carbon black 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 in the range of 5 to 40 mass% as a ratio in the resin layer (a1). If the addition amount is less than 5 mass%, the blackness is insufficient and the color tone of the base steel sheet cannot be concealed, and a high-quality design cannot be imparted. On the other hand, even if the added amount exceeds 40 mass%, 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 can manufacturing. There is a risk of it. By making the addition amount in the range of 5 to 40 mass%, 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.

Additives: In addition to colorants and white / brilliant black pigments, for example, white pigments can be added to conceal the metallic luster of the base and the printed surface can be sharpened to obtain a good appearance. be able to. 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 (a1). If it is 5 mass% or more, sufficient whiteness can be obtained and good design properties can be secured. On the other hand, even if added over 30 mass%, the whiteness is saturated, so it is desirable to make it 30 mass% or less for economic reasons. A more preferable addition amount is 10 to 20 mass%.

  In addition, when a bright color is desired on the container surface, an azo pigment may be added. Since azo pigments are excellent in transparency, they have strong coloring power and are excellent in spreadability, so that a bright appearance can be obtained even after molding of the container. Examples of the azo pigment include those having a color index (CI registered name) of Pigment Yellow 12, 13, 14, 16, 17, 55, 81, 83, 139, 180, 181 and the like. The above 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, C.I. Pigment Yellow 180 having a molecular weight of 700 or more and having a benzimidazolone structure is particularly preferable.

  The added amount of the azo pigment is preferably 10 to 40% by mass in the resin layer (a1). If the addition amount is 10 mass% or more, good color development can be obtained. Moreover, when the addition amount is 40 mass% or less, the transparency becomes higher and the color tone is rich.

Adhesion amount of the resin layer consisting of deposited amount or more (a1) (coating weight of the total ingredients) is preferably 0.1 to 5.0 g / m ^2, more preferably, 0.5 g / m ² to 2.5 g / m ² . If the adhesion amount is less than 0.1 g / m ² , the surface of the metal plate cannot be uniformly coated, and the film thickness may be non-uniform. An isocyanate compound, a π-conjugated polymer, and the like are unevenly distributed, and a stable function cannot 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 (a1) may be reduced. 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 (a2) that forms the upper layer of the resin layer (a1) will be described.
The polyester film composition polyester film (a2) is mainly composed of ethylene terephthalate and / or ethylene naphthalate from the viewpoint of improving the taste characteristics after retort and suppressing the generation of abrasion powder in the can making process. It is desirable. 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 resin contains ethylene terephthalate and / or ethylene naphthalate as a constituent. If it is 95 mass% or more, the taste characteristics are good even if the beverage is filled in a metal can for a long period of time, which is more preferable. 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, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, p-oxybenzoic acid and other oxycarboxylics An acid etc. can be mentioned.

  Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentylglycol, alicyclic glycols such as cyclohexanedimethanol, and aromatics such as bisphenol A and bisphenol S. Examples include glycol, diethylene glycol, and polyethylene glycol.

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.

The particle polyester film (a2) may contain particles for the purpose of improving moldability and adhesion. The particles may be organic particles or inorganic particles, but preferably have a volume average particle diameter of 0.005 to 5.0 μm from the viewpoint of wear resistance, workability, taste characteristics, etc. It is especially preferable that it is 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. Furthermore, 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 necessary to contain 0.005-10 mass% of the 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. Among these, those in which the functional group on the particle surface reacts with the polyester to form a carboxylic acid metal salt are preferred. Specifically, the one having 10 ⁻⁵ mol or more of the carboxylic acid metal salt with respect to 1 g of particles is polyester. It is preferable at points, such as an affinity 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, and 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. 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 may be used alone, but it is preferable to use two or more kinds in combination, and by combining particles having different physical properties such as particle size distribution and particle strength, further functionality can be obtained. A high polyester film can be obtained.

  In addition, other particles such as various amorphous external addition particles and internal precipitation particles, various surface treatment agents, and the like may be added as long as the effects of the present invention are not hindered.

Furthermore, from the viewpoint of heat resistance and taste characteristics, the polyester film (a2) 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, the plane orientation coefficient is controlled within a specific range in order to achieve both formability and impact resistance even if there is some variation during lamination. This is preferable because it can be performed.
In addition, the biaxially stretched polyester film is 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. It is desirable that the relaxation time of the carbonyl moiety in the structural analysis is 270 msec or more, more preferably 280 msec or more, and particularly preferably 300 msec or more.

The thickness of the polyester film (a2)
The thickness of the polyester film (a2) is preferably 5 to 100 μm. When the thickness of the polyester film (a2) 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, the above properties are saturated and an improvement effect matching the thickness of the polyester film cannot be obtained. Moreover, since the heat energy required for heat fusion to the metal plate surface increases, there is a risk of impairing the economy. From such a viewpoint, the more preferable thickness of the polyester film (a2) 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.
As an example of the method for forming the resin layer (a1), a method for forming the resin layer (a1) in close contact with the metal plate surface on the surface of the upper polyester film (a2) will be described. The polyester resin, which is the main component of the resin layer (a1), is dissolved in an organic solvent, and the additive component and optional additive component defined by the present invention are dissolved or dispersed to prepare a coating liquid (resin solution). The liquid is applied to the film surface during or after the formation of the polyester film (a2) and dried to form the resin layer (a1).
Examples of the organic solvent for dissolving the polyester resin 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.
Addition of block-free isocyanate compounds, epoxy resins and metal ion-exchanged silica as defined in the present invention, and hydrophobic polyols and colorants (for example, carbon black, azo pigments, etc.) added as necessary The agent is also used dispersed 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.
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 method of laminating the polyester film (a2) after coating the resin layer (a1) on the surface of the metal plate The polyester film (a2) in which the resin layer (a1) is formed as described above, the resin layer (a1) is a metal Laminate on the surface of the metal plate so that it is in close contact with the plate. As the laminating method, for example, a metal plate is heated to a temperature exceeding the melting point of the polyester film, and a polyester film (a2) coated with a resin layer (a1) on the surface of the heated metal plate is laminated roll (compression roll). The polyester film (a2) coated with the resin layer and coated with the resin layer (a1) can be heat-sealed. At this time, as described above, the surface of the polyester film (a2) coated with the resin layer (a1) is pressure-bonded to the cold-rolled steel sheet and thermally fused.
Regarding the lamination conditions, for example, the temperature at the start of lamination is at least the melting point of the polyester film (a2), and the temperature history received by the polyester film (a2) at the time of lamination is the temperature at or above the melting point of the polyester film (a2). It is preferable that the time during which the time is 1 to 20 msec. In order to achieve such lamination conditions, in addition to high-speed lamination, cooling during fusion is also necessary. The pressure during lamination is preferably 9.8 to 294 N / cm ² (1 to 30 kgf / cm ² ) as the surface pressure. 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, and the equipment strength is required, resulting in an increase in the size of the apparatus, which is uneconomical.

Production of Metal Sheet (Cold Rolled Steel Sheet) After cold rolling on low carbon steel, annealing and temper rolling were performed to produce a cold rolled steel sheet having a thickness of 0.18 mm and a width of 977 mm.

Production of resin coating film on inner surface of can The polyester resin obtained by polymerizing an acid component and a glycol component blended as shown in Table 1 is blended with the particles shown in Table 1 to obtain a resin composition. This resin composition According to a conventional method, the mixture was melt-extruded, cooled and solidified on a cooling drum to obtain an unstretched film, and then biaxially stretched and heat-fixed to obtain a biaxially stretched oriented film (a2).
Various additives such as isocyanate compounds, epoxy resins, and metal ion exchange silica shown in Table 2 are added to the polyester resin obtained by polymerizing the acid component and glycol component shown in Table 2, and this is added to toluene. A coating solution (resin solution) for the resin layer (a1) was prepared by dissolving and dispersing in a mixed solvent of methyl ethyl ketone. This coating solution is applied to one side of the biaxially stretched polyester film (a2) by a gravure roll coater so as to have a predetermined dry adhesion amount, dried (drying temperature: 80 to 120 ° C.), and resin on the inner surface side of the can A coating layer (A1) was obtained. In some comparative examples, a polypropylene film was used as the film, and epoxyphenol was used as the resin for the coating solution.

Production of a resin coating film on the outer surface of the can The polyester resin obtained by polymerizing an acid component and a glycol component blended as shown in Table 3 was blended with the particles shown in Table 3 to obtain a resin composition. This resin composition According to a conventional method, the mixture was melt-extruded and cooled and solidified on a cooling drum to obtain an unstretched film, and then biaxially stretched and heat-fixed to obtain a biaxially oriented film (a2).
Various additives such as isocyanate compounds, epoxy resins, and metal ion exchange silica shown in Table 4 are added to the polyester resin obtained by polymerizing the acid component and the glycol component of the formulation shown in Table 4, and this is added to toluene. A coating solution (resin solution) for the resin layer (a1) was prepared by dissolving and dispersing in a mixed solvent of methyl ethyl ketone. This coating solution is applied to one side of the biaxially stretched polyester film (a2), dried with a gravure roll coater so as to have a predetermined dry adhesion amount, dried (drying temperature: 80 to 120 ° C.), and the outer side of the can The resin coating layer (A2) was obtained.
In some comparative examples, a polypropylene film was used as the film, and epoxyphenol was used as the resin for the coating solution.

Production of Resin-Coated Metal Sheet for Container In the laminating equipment shown in FIG. 1, the cold-rolled steel sheet 1 obtained above is heated with a metal band heating device 2, and the laminate roll 3 is applied to one surface of the cold-rolled steel sheet. The resin coating layer (A1) 4a on the inner surface side of the can obtained in (1) was laminated (heat fusion), and the resin coating layer (A2) 4b on the outer surface side of the can obtained above was laminated (heat fusion) on the other surface. And then water-cooled with a metal band cooling device 5 to produce a resin-coated metal plate for containers. 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 was 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 metal plate for containers (invention example) produced as described above.

Evaluation of Resin Coated Metal Plate The following performance was evaluated for the resin coated metal plate produced as described above.
A wax was applied to a resin-coated metal plate for a moldable container, and then 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. About the neck-in part of the deep-drawn can thus obtained, the degree of damage of the resin coating layers (A1 and A2) on the can inner surface side and the can outer surface side was visually observed and evaluated according to the following evaluation criteria.
(About the score)
◎: No damage is observed on the film after molding. ○: No damage is observed on the film after molding, but partial whitening is observed.
Adhesion after molding (1)
Cans that were moldable in the moldability evaluation (evaluation of ◯ or higher) 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 a direction opposite to the peeled direction (angle: 180 °), and a peel test is performed using a tensile tester at a tensile speed of 30 mm / min. Evaluation was made based on the following evaluation criteria.
(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)
Adhesion after molding (2)
Cans that were moldable in the moldability evaluation (evaluation of ◯ or higher) were targeted. After filling the inside of the can with tap water, the lid was wrapped and sealed. Subsequently, retort sterilization was performed at 130 ° C. for 90 minutes, and a peel test sample (width 15 mm, length 120 mm) was cut out from the can body. A part of the film is peeled off from the long side end 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 an adhesive force per 15 mm width is measured. And evaluated according to the following evaluation criteria.
(Score)
A: 8.0 (N) / 15 (mm) or more B: 3.0 (N) / 15 (mm) or more, less than 8.0 (N) / 15 (mm) x: 3.0 (N) / Less than 15 (mm) Evaluation of scratch corrosion resistance (1)
Cans that were moldable in the moldability evaluation (evaluation of ◯ or higher) were targeted. As shown in FIG. 3, crosscut scratches that reach the base steel plate are made in two places on the can body portion on the outer surface side of the can.
A salt spray test according to JISZ2371 was performed for 3 hours on the can with the cross-cut scratches, and then allowed to age for 300 hours in a constant temperature and humidity chamber having a relative humidity of 85% and a temperature of 45 ° C. Then, the one-side maximum corrosion width from a wound part was measured, and the following evaluation criteria evaluated. In addition, the measuring method of the one-side maximum corrosion width from a damage | wound part is shown in FIG.
(About the score)
◎: One side maximum corrosion width less than 1.0 mm ○: One side maximum corrosion width 1.0 mm or more to less than 2.0 mm ×: One side maximum corrosion width 2.0 mm or more Scratch corrosion resistance evaluation (2)
Cans that were moldable in the moldability evaluation (evaluation of ◯ or higher) were targeted. As shown in FIG. 3, crosscut scratches reaching the base steel plate were made at two locations on the can body on the inner surface of the can. The can provided with the cross-cut wound was filled with a 1.5% NaCl + 1.5% sodium citrate mixed solution, and then the lid was wound and sealed. Subsequently, the retort sterilization treatment was performed at 130 ° C. for 90 minutes, and then aged for 5 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.
(About the score)
◎: Maximum corrosion width on one side of less than 2.0 mm ○: Maximum corrosion width on one side of 2.0 mm to less than 4.0 mm ×: Results of performance evaluation test obtained by the maximum corrosion width on one side of 4.0 mm or more It is shown in FIG.

According to Tables 5 and 6, the examples of the present invention are excellent in all of moldability, post-mold adhesion, and scratch corrosion resistance required for container materials. In contrast, the comparative example is inferior in performance.

  It is a container material and packaging material that can be used in all markets around the world, mainly for canned foods and lids.

DESCRIPTION OF SYMBOLS 1 Cold-rolled steel plate 2 Metal band heating apparatus 3 Laminate roll 4a Resin coating layer (A1)
4b Resin coating layer (A2)
5 Metal band cooling device

Claims (7)

At least one surface of the metal plate has a multi-layered resin coating layer (A) mainly composed of polyester resin, and the resin coating layer (A) is in close contact with the metal plate surface and includes the following (a) to (c) And a resin layer (a1) containing a polyester resin as a main component.
(A) Block-free isocyanate compound: ratio of mole number (α) of NCO groups in the block-free isocyanate compound to mole number (β) of OH groups in the polyester resin and epoxy resin in the resin layer (a1) (Α) / (β) content of 0.5 to 5.0 (b) Epoxy resin: softening point is 80 ° C. or higher, and is 1 to 20 mass% with respect to the resin layer (a1). Content (c) Metal ion exchanged silica: Content of 1 to 25 mass% with respect to the resin layer (a1)   The resin coating layer (A) is composed of the resin layer (a1) mainly composed of a polyester resin and a polyester film (a2) formed on the upper layer of the resin layer (a1). The resin-coated metal plate for containers according to 1. The adhered amount of the resin layer (a1) is a container for resin-coated metal plate according to claim 1 or 2, characterized in that a 0.1 to 5.0 g / m ^2.   The resin-coated metal sheet for containers according to any one of claims 1 to 3, wherein the epoxy resin in the resin layer (a1) is a novolac type epoxy resin.   The metal ion exchange silica contained in the resin layer (a1) is one or two selected from zinc ion exchange silica and calcium ion exchange silica. The resin-coated metal plate for containers as described.   The resin-coated metal sheet for containers according to any one of claims 1 to 5, wherein the resin layer (a1) contains a hydrophobic polyol in a range of 5 to 20 mass% with respect to the polyester resin.   The polyester film (a2) is a biaxially stretched polyester film in which 93 mass% or more of the structural unit of the polyester resin is an ethylene terephthalate unit and / or an ethylene naphthalate unit, and the biaxially stretched polyester film comprises inorganic particles and / or Or the organic resin is contained, The resin-coated metal plate for containers in any one of Claims 2-6 characterized by the above-mentioned.