TW201928118A - Organic-resin-coated two-piece aluminum can - Google Patents

Abstract

The present invention addresses the problem of suppressing discoloration produced by hot water sterilization performed with part of the outer surface side of a can in contact with the water. Provided is a two-piece aluminum can formed from an aluminum sheet comprising, on at least one side of an aluminum alloy substrate, an inorganic surface treatment coating that contains zirconium, fluorine, and oxygen and contains substantially no phosphorus, an organic surface treatment coating that contains a water-soluble phenolic resin, and a resin layer that contains a thermoplastic polyester resin, in that order starting from the aluminum alloy substrate; the deposited amount of the organic surface treatment coating being 3 mg/m2 to 20 mg/m2 in terms of carbon per unit of area; the two-piece aluminum can comprising the inorganic surface treatment coating, the organic surface treatment coating, and the resin layer on at least the outer surface side of the can; the resin layer disposed on the outer surface side of the can being a resin blend of polyethylene terephthalate resin and polybutylene terephthalate resin; and the polybutylene terephthalate resin content of the resin layer being 20 wt.% to 50 wt.%.

Description

Organic resin coated two-piece aluminum can

The present invention relates to metal cans for various beverages and foods, and more particularly to two-piece aluminum cans.

In order to maintain the flavor of the contents and prevent the corrosion of metal cans, the two-piece aluminum cans used as packaging containers for various beverages and foods are made of a thermoplastic resin such as a polyester film laminated on the surface of a metal plate. The aluminum metal sheet is processed into a can. When the two-piece aluminum cans made into cans are used in various beverages and food applications such as coffee, black tea, tea, etc., a steam retort sterilization treatment of 110 to 140 ° C is usually performed. During this distillation and sterilization treatment, water droplets adhere to the bottom of the tank, and the resin that melts to become amorphous during lamination is crystallized at the water droplet adhesion portion, causing the problem of retort brushing (white spots). And someone has proposed a technique to solve this problem.

For example, Patent Document 1 proposes a metal laminate, which is a metal laminate by thermally pressing a resin film having two melting point peaks to a metal plate, and the resin film is blended with a weight of 10 to 70 % Of polyethylene terephthalate resin and 90-30% by weight of polybutylene terephthalate resin.
In addition, Patent Document 2 proposes an organic resin-coated metal plate coated with a polyester resin, which is based on a copolymerized polyester mainly composed of a polyethylene terephthalate resin, and the blending amount is 20 Under the condition of ~ 45% by weight, a crystalline polyester mainly composed of a polybutylene terephthalate resin is mixed.

[Prior technical literature]
[Patent Literature]
[Patent Document 1] Japanese Patent Laid-Open No. 2008-143184
[Patent Document 2] International Publication No. 2015/012222

[Problems to be solved by the invention]
The technology proposed to solve the above-mentioned distillation and painting is a mixed resin in which polyethylene terephthalate is blended with a certain amount of polybutylene terephthalate.
The present inventors have found a new problem that hot water sterilization treatment is performed on a part of the outer surface side of the iron body of a can body in contact with water in a two-piece aluminum can covered with the mixed resin. In the gas-liquid interface existing on the outer surface side of the tank, a boehmite film is formed on the surface of the aluminum alloy substrate where the aluminum alloy substrate reacts with water vapor, and the color of the surface of the aluminum alloy substrate causes a color tone on the outside of the tank body Abnormal, and even worse, because of the volume expansion of the boehmite film, the polyester resin was peeled from the aluminum alloy substrate.
The present invention is to solve such a new problem.

[Means to solve the problem]
The inventors of the present invention, while discussing and solving the above-mentioned problems, found that the surface of the two-piece aluminum can substrate on the outer surface side of the tank has an inorganic surface treatment film and an organic surface treatment film, and the amount of adhesion of the organic surface treatment film is controlled to a very low The above-mentioned problems can be solved within a small number of specific ranges, and the present invention has been completed.

The present invention includes the following:
[1] A two-piece aluminum can, comprising: the aforementioned two-piece aluminum can is formed by containing an aluminum plate on at least one side of an aluminum alloy substrate, and the aluminum plate sequentially has: an inorganic surface treatment from the aluminum alloy substrate side Films that contain zirconium, fluorine, and oxygen, and do not substantially contain phosphorus; organic surface treatment films that contain water-soluble phenolic resins; resin layers that contain thermoplastic polyester resins; In terms of carbon conversion mass, the adhesion amount of the organic surface treatment film is 3 mg / m ² or more and 20 mg / m ² or less. The two-piece aluminum can system has the inorganic surface treatment film and the organic surface treatment at least on the outer surface side of the can. The film and the resin layer are mixed resins of a resin layer-based polyethylene terephthalate-based resin and a polybutylene terephthalate-based resin disposed on the outer surface side of the tank. The content of the butyl phthalate resin is 20% by weight or more and 50% by weight or less.
[2] The two-piece aluminum can according to [1], wherein the adhesion amount of the inorganic surface treatment film is 3 mg / m ² or more and 25 mg / m ² or less in terms of zirconium atom-equivalent mass per unit area.
[3] The two-piece aluminum can according to [1] or [2], wherein the organic surface treatment film is a polymer having a repeating structure represented by the following formula (I), and the formula (I) is:
[Chemical 1]


[In formula (I), X is a hydrogen atom or a Z group represented by the following formula (II), and formula (II) is:
[Chemical 2]

(In the formula (II), R ¹ and R ² are each independently an alkyl group having 10 or less carbon atoms or a hydroxyalkyl group having 10 or less carbon atoms), and the introduction rate of the Z group per benzene Ring 0.3 to 1.0]; When X in the formula (1) is a hydrogen atom, the weight average molecular weight of the polymer is in the range of 1,000 to 100,000.
[4] The two-piece aluminum can according to any one of [1] to [3], wherein the aluminum alloy located on the resin layer is disposed on the resin layer disposed on the outer surface side of the can of the aluminum alloy base The melting point of the resin on the substrate side is higher than the melting point of the resin on the surface layer side.
[5] The two-piece aluminum can according to any one of [1] to [4], wherein the aluminum plate is provided with an inorganic surface-treated film, an organic surface-treated film, and a resin layer on both sides; in the resin layer, For the resin layer disposed on the inner surface side of the can of the aluminum alloy substrate, the melting point of the resin on the content side of the resin layer is higher than the melting point of the resin on the aluminum alloy substrate side.
[6] The two-piece aluminum can according to any one of [1] to [5], wherein the two-piece aluminum can is formed by drawing and ironing.

[Inventive effect]
According to the present invention, it is possible to provide a two-piece aluminum can that can suppress abnormal color tone even when hot water sterilization is performed while a part of the outer surface side of the can is in contact with water.
Furthermore, in a preferred aspect, the adhesion between the aluminum alloy substrate and the inorganic surface treatment film can be improved by selecting the zirconium amount of the inorganic surface treatment film within a specific range.
In a preferred aspect, in the resin layer disposed on the outer surface side of the can of the aluminum alloy substrate, the melting point of the resin on the aluminum alloy substrate side of the resin layer is higher than the melting point of the resin on the surface layer side. Therefore, it can improve the crystallinity of polyethylene terephthalate and suppress the abnormal color tone on the outer surface side of the can; and in the resin layer disposed on the inner surface side of the can of the aluminum alloy substrate, because it is located on the content side of the resin layer The melting point of the resin is higher than the melting point of the resin located on the aluminum alloy substrate side, so it can improve flavor retention, damage resistance, release properties when making cans, and trimming properties.

The two-piece aluminum can according to an embodiment of the present invention is formed by including an aluminum plate on at least one side of the aluminum alloy substrate, and the aluminum plate has an inorganic surface treatment film in order from the aluminum alloy substrate side, which contains zirconium, Fluorine and oxygen, and substantially no phosphorus; organic surface treatment film, which contains water-soluble phenol resin; resin layer, which contains thermoplastic polyester resin.

(Inorganic surface treatment film)
The inorganic surface treatment film contains zirconium, fluorine, and oxygen, and does not substantially contain phosphorus. The inclusion of zirconium, fluorine, and oxygen in the inorganic surface-treated film can improve corrosion resistance and adhesion. An inorganic surface treatment film can be formed by contacting the inorganic surface treatment agent containing the above-mentioned zirconium, fluorine, and oxygen with the surface of the aluminum alloy substrate.

The supply source for supplying zirconium to the inorganic surface treatment agent is not particularly limited as long as it is a component capable of supplying zirconium ions, zirconium-containing ions, or ion ions to the surface treatment agent. For example, zirconium oxide, zirconium hydroxide, zirconium nitrate, zirconium fluoride such as hexafluorozirconic acid, its alkali metal salt or ammonium salt, and the like can be used. These ingredients may be used alone or in combination of two or more.
The mass mole concentration of zirconium in the inorganic surface-treating agent is not particularly limited, and generally, a good film can be formed by setting it within a range of 3.2 mmol / kg or more and 33.0 mmol / kg or less. The mass molar concentration of the zirconium may be in a range of 3.2 mmol / kg or more and 11.0 mmol / kg or less.

The supply source for supplying fluorine to the inorganic surface treatment agent is not particularly limited as long as it can provide components such as fluorine ions, fluorine-containing ions, or counter ions in the surface treatment agent. For example, acids such as hydrofluoric acid, ammonium fluoride, acid ammonium fluoride, hexafluorozirconic acid, hexafluorosilicic acid, tetrafluoroboric acid, and the salts of these acids can be used. These ingredients may be used alone or in combination of two or more.
The mass mole concentration of fluorine in the inorganic surface-treating agent is not particularly limited. Generally, a good film can be formed by setting it to a range of 52.6 mmol / kg or more and 526.3 mmol / kg or less.

By treating the aluminum alloy substrate with the above-mentioned inorganic surface treatment agent, the surface of the aluminum alloy substrate passes through the dissolution of the matrix aluminum and alumina film, the hydrolysis of fluoride ions and zirconium ions, or the supply source of fluorine or zirconium. As a result of reactions such as hydrolysis of the supply source, as a result, ZrO ₂ , ZrO _x (OH) _y F _z , AlOF, AlF _3, etc. are formed, and an inorganic surface treatment film containing zirconium, fluorine and oxygen is formed on the aluminum alloy substrate.

The inorganic surface treatment agent may further include Bi (element), Co (element), Fe (element), Ni (element), Mg (element), and the like. These elements can be contained in the inorganic surface treatment agent in various forms, such as an ionic form and a mision form. The supply source of these ions or ions is not particularly limited, and for example, metal compounds such as Bi, Co, Fe, Ni, or Mg can be used: nitrates, sulfates, oxides, hydroxides, and fluorides. . These ingredients may be used alone or in combination of two or more. By using an inorganic surface treatment agent mixed with the aforementioned metal compound, an inorganic surface treatment film is formed on or on the surface of the aluminum alloy substrate, and the adhesion between the resin layer formed on the inorganic surface treatment film and the aluminum alloy substrate can be improved. Sex.

When the aforementioned metal compound is blended, the content of the aforementioned metal compound in the inorganic surface treatment agent is usually 0.1 mmol / kg or more in terms of the molar molar equivalent of the blended metal atom. Moreover, it is preferably 62.0 mmol / kg or less, and more preferably 41.0 mmol / kg or less. By using an inorganic surface treatment agent having a metal compound content within the above range and forming an inorganic surface treatment film on or on the surface of the aluminum alloy substrate, the resin layer formed on the inorganic surface treatment film and the aluminum alloy substrate can be improved. Of adhesion.

The inorganic surface treatment agent preferably does not substantially contain Sn (element). By using an inorganic surface treatment agent that does not substantially contain Sn (elements), an inorganic surface treatment film is formed on the surface or the surface of the aluminum alloy substrate, and the deterioration of the corrosion resistance of the formed inorganic surface treatment film can be suppressed. The fact that Sn (element) is not substantially contained means that the mass mole concentration of Sn (element) in the inorganic surface treatment agent is 0.1 mmol / kg or less, or 0.05 mmol / kg or less, and 0.01 mmol / kg or less. It is more preferable that Sn (element) is not contained at all.

The inorganic surface treatment agent may contain Zn (element). Zn (element) may be contained in the inorganic surface treatment agent in any form, and may be, for example, an ionic form or a mision form. The supply source of these ions or ions is not particularly limited, and examples thereof include nitrate, sulfate, oxide, hydroxide, and fluoride of Zn. When Zn (element) is contained, the molar mole concentration of Zn (element) in the inorganic surface treatment agent is preferably 1.5 mmol / kg or less, and more preferably 0.8 mmol / kg or less. By using an inorganic surface treatment agent having a mass mole concentration of Zn (element) within the above range, and forming an inorganic surface treatment film on the surface or surface of the aluminum alloy substrate, the corrosion resistance of the formed inorganic surface treatment film can be improved. Sex. The inorganic surface treatment agent may not contain Zn (element) at all.

Although the inorganic surface treatment agent may contain components other than the components described above, it is preferable that it does not substantially contain organic matter. By using an inorganic surface treatment agent that does not substantially contain an organic substance, an inorganic surface treatment film is formed on the surface or surface of the aluminum alloy substrate, and the deterioration of the solubility of the inorganic surface treatment film against an acidic aqueous solution can be suppressed. In addition, the term "substantially free of organic substances" means that the mass molar concentration of the organic substance in the inorganic surface treatment agent (meaning the total mass molar concentration when plural organic substances are present) is 0.1 mmol / kg or less and may be 0.05 mmol / kg or less It may also be 0.01 mmol / kg or less, and preferably does not contain organic matter at all.

On the other hand, the inorganic surface treatment agent does not substantially contain phosphorus. The fact that phosphorus is not substantially contained means that the mass molar concentration of phosphorus in the inorganic surface treatment agent is 0.1 mmol / kg or less, or 0.05 mmol / kg or less, or 0.01 mmol / kg or less. Contains phosphorus. In other words, the inorganic surface-treated film does not substantially contain phosphorus.

In order to dissolve or disperse the component forming the inorganic surface treatment film and / or adjust the concentration of the component in the inorganic surface treatment, the inorganic surface treatment agent may contain a solvent. For a typical solvent, it is water.

By contacting the inorganic surface treatment agent described above with the aluminum alloy substrate, an inorganic surface treatment film can be obtained. After the inorganic surface treatment agent is brought into contact with the aluminum alloy substrate, the inorganic surface treatment agent may be dried.
The contact method between the inorganic surface treatment agent and the aluminum alloy substrate is not particularly limited, and examples thereof include a dipping method, a spray treatment method, and a curtain method. The contact time can be appropriately set, usually between 1 and 20 seconds, and in the case of spraying the inorganic surface treatment agent on the aluminum alloy substrate, the contact time is preferably within the range of 2 to 10 seconds. The contact temperature between the inorganic surface treatment agent and the aluminum alloy substrate is not particularly limited, but is usually in the range of 40 to 70 ° C.

In terms of the adhesion amount of the inorganic surface treatment film formed on the surface of the aluminum alloy substrate, it is usually 3 mg / m ² or more, preferably 5 mg / m ² or more, in terms of the zirconium atom conversion mass per unit area; or usually It is 25 mg / m ² or less, and preferably 20 mg / m ² or less. When the adhesion amount of the inorganic surface treatment film is within the above range, the adhesion between the resin layer formed on the inorganic surface treatment film and the aluminum alloy substrate can be further improved.

(Organic surface treatment film)
The organic surface treatment film system contains a water-soluble phenol resin, and the phenol resin is preferably a polymer (hereinafter, simply referred to as a polymer) having a repeating structure represented by the following formula (I).
[Chemical 3]

[In formula (I), X is a hydrogen atom or a Z group represented by the following formula (II), and the introduction rate of the aforementioned Z group is 0.3 to 1.0 per benzene ring, and formula (II) is:
[Chemical 4]

(In the formula (II), R ¹ and R ² are each independently an alkyl group having 10 or less carbon atoms or a hydroxyalkyl group having 10 or less carbon atoms)].

The calculation method of the introduction rate of the Z group can be, for example, that the polymer is completely burned by CHNS-O elemental analysis, and the generated gas (CO ₂ , H ₂ O, N ₂ , SO ₂ ) is measured to quantify each element It is measured and calculated based on the result of quantitative measurement.
When all X are hydrogen atoms, the weight average molecular weight of the polymer is in the range of 1,000 to 100,000. The method for obtaining the weight average molecular weight can be obtained, for example, as a molecular weight equivalent to polystyrene measured by a gel permeation chromatography.

The organic surface treatment agent may include a water-soluble phenol resin and water, and preferably includes the above-mentioned polymer and water, and may further include other components such as an acid component. The production method is not particularly limited, and for example, it can be prepared by mixing a polymer, water, and an acid-based compound added as necessary.

The concentration of the water-soluble phenol resin in the organic surface treatment agent is not particularly limited, but is usually 0.01 g / L or more, and preferably 0.05 g / L or more. It is usually 30 g / L or less, and preferably 10 g / L or less.
Although the pH value of the organic surface treatment agent is not particularly limited, the pH value of the temperature when in contact with the surface of the aluminum alloy substrate is preferably in the range of 3.0 to 6.0.

By contacting the organic surface treatment agent with an aluminum alloy substrate having an inorganic surface treatment film, an organic surface treatment film can be obtained. The contacted organic surface treatment agent may also be dried. The contact method, contact time, and contact temperature are not particularly limited, and a contact method, contact time, and contact temperature when an inorganic surface treatment agent is brought into contact with an aluminum alloy substrate may also be applied.

In terms of the adhesion amount of the organic surface treatment film formed on the aluminum alloy substrate having the inorganic surface treatment film, it is usually 3 mg / m ² or more, preferably 4 mg / m ² , in terms of the mass of carbon per unit area. The above is generally 20 mg / m ² or less, preferably 15 mg / m ² or less, and more preferably 10 mg / m ² or less. When the amount of the organic surface-treated film is within the above range, that is, when the organic surface-treated film has a thin film thickness, even if a part of the outer surface side of the tank is in contact with water, hot water sterilization treatment is performed, It is also possible to suppress the abnormal color tone generated on the outer surface of the tank.
In the organic surface treatment film, the amount of adhesion is approximately related to the thickness of the film, and when the carbon-converted mass per unit area is 10 mg / m ² as the film thickness, it can be considered as a film thickness of about 10 nm.

(Resin layer)
The resin layer contains a thermoplastic polyester resin. More specifically, a resin layer-based polyethylene terephthalate (hereinafter referred to as PET) -based resin and a polybutylene terephthalate (hereinafter referred to as PBT) are arranged on the outer surface side of the can of the aluminum alloy substrate. ) Series resin, and the content of polybutylene terephthalate resin in the resin layer is 20% by weight or more, preferably 25% by weight or more; more preferably 50% by weight or less, more preferably It is 45% by weight or less. By using the above-mentioned mixed resin, the problem of distillation painting can be solved.

Polyethylene terephthalate resin refers to the resin whose main component is polyester terephthalate, and polybutylene terephthalate resin refers to the polyester component. The main component is a resin of polybutylene terephthalate. Here, the main component system may be 50 mol% or more, may be 70 mol% or more, and may be 80 mol% or more.
Among the dicarboxylic acid component and the diol component constituting the polyester, acid components other than terephthalic acid are not particularly limited, and examples thereof include isophthalic acid, phthalic acid, and p-β-oxygen. Ethoxybenzoic acid, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, sodium 5-sulfoisophthalate, hexahydroterephthalic acid, adipic acid , Sebacic acid, trimellitic acid, pyromellitic acid, etc.
Examples of the diol component other than ethylene glycol and butanediol include propylene glycol, diethylene glycol, 1,6-hexanediol, and an ethylene oxide adduct of bisphenol A.

The shape of the resin layer is not particularly limited, and typical examples include a lamellar shape and a film shape.

When the resin layer is a laminated film, the bonding method is not particularly limited, and a conventional method can be applied. Specific examples include a dry lamination method and an extrusion lamination method. In addition, a resin adhesive may be applied to the bonding surface of the laminated film for bonding.

In this embodiment, the resin layer disposed on the outer surface side of the can of the aluminum alloy substrate may have almost the same melting point on the aluminum alloy substrate side and the surface layer side, but the resin on the aluminum alloy substrate side has a better melting point. It is higher than the melting point of the resin on the surface layer side. By having such a structure that the resin layer arrange | positioned on the outer surface side of a can of an aluminum alloy base body is made like this, the crystallinity of polyethylene terephthalate can be improved and the color tone abnormality of an outer surface side of a can can be suppressed.
Further, for the resin layer disposed on the inner surface side of the can of the aluminum alloy substrate, the melting point of the resin on the content side is preferably higher than the melting point of the resin on the aluminum alloy substrate side. By having such a structure that the resin layer arrange | positioned on the inner surface side of the can of an aluminum alloy base body is carried out, the flavor retention property, abrasion resistance, the release property at the time of making a can, and the trimming property can be improved.

As a means for differentiating the melting points of the resins on the surface layer side and the aluminum alloy substrate side of the resin layer, for example, the following methods can be mentioned: by preparing two resin layers having different melting points and laminating these resins Layer method; by preparing two kinds of resins having different melting points and making the two kinds of resins have a concentration gradient, these resins are made into a resin composition, and then the aforementioned resin composition is extruded using an extruder.

When there is a difference between the melting points of the resins on the surface layer side of the resin layer and the aluminum alloy substrate side, the difference is not particularly limited, but it is usually higher than 0 ° C, preferably 8 ° C or higher; The temperature is 40 ° C or lower, preferably 30 ° C or lower.

The thickness of the resin layer formed on the aluminum alloy substrate is not particularly limited, and is usually 5 μm or more, preferably 7 μm or more; and usually 30 μm or less, and preferably 20 μm or less. In the state of the resin-coated aluminum alloy plate (before can-making), the thickness of the surface layer resin layer and the aluminum alloy substrate side resin layer is preferably 1: 9 ~ 6: 4, more preferably 2: 8 ~ 5: 5. .

(Aluminum alloy substrate)
The raw material of the aluminum alloy substrate used in this embodiment is not particularly limited as long as it is a material for aluminum cans, and examples thereof include an aluminum-manganese alloy material (A3000 series) and aluminum-magnesium Alloy materials (A5000 series), pure aluminum materials (A1000 series), etc.

As for the aluminum alloy substrate, it is preferable that the surface of the aluminum alloy substrate is cleaned before the inorganic surface treatment film is formed. The method for cleaning the surface is not particularly limited, and examples thereof include a degreasing method. The degreasing agent used in the degreasing method is not particularly limited, and examples thereof include organic solvents, alkaline degreasing agents, and acidic degreasing agents that are generally used. In addition, for the purpose of removing the aluminum oxide film, it is more desirable to perform an acid treatment after degreasing, which is preferable.

Although the thickness of the aluminum alloy substrate is not particularly limited, when it is used as a can, it is usually 0.15 mm or more, preferably 0.20 mm or more; and usually 0.50 mm or less, and preferably 0.35 mm or less.

(Production of aluminum cans)
An aluminum alloy substrate having an inorganic surface treatment film, an organic surface treatment film, and a resin layer in order on the surface can be formed into an aluminum can. Forming into a tank system can use conventional methods, such as deep drawing forming, deep drawing and deep drawing forming, stretch draw forming, stretch ironing forming, and deep drawing iron forming. In particular, even under severe processing conditions in which the reduction ratio (reduction ratio) of the thickness of the can body portion accompanying drawing and ironing is 50% or more, by applying the present invention, even on the outer surface side of the can It is also possible to suppress abnormal color tone by performing hot water sterilization while a part of the contact with water is in contact.

[Example]
Although the present invention will be described in more detail below based on examples, it goes without saying that the scope of the present invention is not necessarily limited to specific examples.

(Preparation of inorganic surface treatment agent)
The preparation of the inorganic surface treatment agent is made up of eight components of water. The following components (A) to (D) are added in the order of (D), (C), (B), (A), and finally prepared with water. Quantitate and stir for 10 minutes at room temperature.
(A) Hexafluorozirconic acid
(B) Aluminum hydroxide
(C) Hydrofluoric acid
(D) nitrate Thus, the modulation having a content of Zr: 5.5mmol / kg, Al: 37.0mmol / kg, F: 136.6mmol / kg, NO 3: 24.1mmol / kg of the inorganic surface-treating agent.

(Preparation of organic surface treatment agent)
As for the polymer used for the substrate treatment agent, the Z group in the structural unit represented by the formula (I) is CH ₂ N (CH ₃ ) ₂ , wherein the introduction rate of the Z group is 0.5 per benzene ring, and X When the weight average molecular weight is 1000 each of the hydrogen atoms.
Ion-exchanged water was charged into a vessel with a stirring function, and 85% phosphoric acid (concentration: 15 g / L) and the polymer (concentration: 40 g / L) were added and dissolved while stirring at normal temperature. After that, the ion-exchanged water was diluted so that the concentration of the polymer was 0.6 g / L to prepare an organic surface treatment agent.

(Surface treatment of aluminum alloy substrate)
As the aluminum alloy substrate for the can, an Al-Mn-based aluminum alloy plate having a thickness of 0.260 mm was used as the A3104P H19 material in JIS H 4000. Using the inorganic surface-treating agent and organic surface-treating agent prepared as described above, surface treatment was performed as described below to form a film.
In order to adjust the pH, the inorganic surface treatment agent is heated to 55 ° C, and then adjusted to a pH value of 3.0 using ammonium hydroxide. After that, the inorganic surface treatment agent is sprayed by a sprayer and brought into contact with the use. The conventional method sequentially performs degreasing, water washing, acid washing, and water washing on both sides of the aluminum alloy plate, and forms an inorganic surface-treated film so that the amount of zirconium (Zr) adheres to the values shown in Table 1.
Next, the organic surface treatment agent was applied to both sides of the aluminum alloy plate on which the inorganic surface treatment film was formed by a coating roller (Coater Roll), and then dried at 160 ° C. to make carbon (C An organic surface treatment film was formed so that the adhesion amount of) became the value of Table 1.

(Measurement of Zr adhesion amount and C adhesion amount)
A scanning fluorescent X-ray analyzer ("Scanning fluorescent X-ray analyzer ZSX PrimusII" manufactured by Rigaku Corporation) was used for the aluminum alloy plate on which the inorganic surface-treated film and the organic surface-treated film were formed on the Zr adhesion amount in the film And the amount of C adhesion was quantified.

(Production of resin-coated aluminum alloy plate)
The polyethylene terephthalate-based resin (I) and the polybutylene terephthalate-based resin (II) were mixed so that the mixing ratio of PBT was the value shown in Table 1, to prepare a resin layer on the surface side. Of resin. First, chips of the polyethylene terephthalate resin (I) and the polybutylene terephthalate resin (II) are mixed, and the mixed chips are placed in an extruder and melted and kneaded. . The kneading conditions are: the kneading temperature is 255 ° C, the ratio of the discharge amount Q (kg / h) to the screw rotation speed N (rpm) of the extruder is Q / N = 1.0, and the residence time in the extruder is 20 minutes.

The polyethylene terephthalate-based resin (III) and the polybutylene terephthalate-based resin (II) can also be used to produce an aluminum alloy substrate-side resin in the same manner as the surface layer-side resin layer described above. Layer of resin. The resins used are as follows.
Polyethylene terephthalate resin (I): isophthalic acid copolymer, intrinsic viscosity (IV) is 0.87
Polybutylene terephthalate resin (III): homopolymer, intrinsic viscosity (IV) is 1.14
Polyethylene terephthalate-based resin (III): an isophthalic acid copolymer having an intrinsic viscosity (IV) of 0.85.

The resin as the surface layer resin layer and the resin as the aluminum alloy substrate side resin layer were melted so that the aluminum alloy substrate side resin layer was in contact with the aluminum alloy plate on which the inorganic surface treatment film and the organic surface treatment film were formed. In the state, a T die is used to extrude through a pre-roll; a laminate roll is used to nip to form an aluminum alloy substrate-side resin layer on the aluminum alloy substrate. Next, a surface layer resin layer is formed on the aluminum alloy substrate side resin layer, and an aluminum alloy plate coated with two resin films is produced.
In addition, the thickness ratio of the surface-layer resin layer to the aluminum alloy substrate-side resin layer is 3: 7, and the thickness of the two resin films is 10 μm in the state of the resin-coated aluminum alloy plate (before can-making). Production.
As for Example 9 in Table 1, a two-layered polyester resin having a structure in which an aluminum alloy substrate-side resin layer and a surface-layer side resin layer were inverted was used as the resin on the outer surface side of the tank. Regarding Example 12 in Table 1, a polyester resin having a two-layer structure is used. The polyester resin having the two-layer structure is a mixture of the above-mentioned PET (I), PBT (II), PET ( III), and a resin layer manufactured in the same manner as the surface layer side resin layer described above will be used as the surface layer side resin layer and the aluminum alloy substrate side resin so as to have a thickness ratio of 3: 7 and two resin film thicknesses of 10 μm. Layer to layer.

In Examples 1 to 12 and Comparative Examples 1 to 3, polyethylene terephthalate resin (isophthalic acid copolymerized) was copolymerized by the same method as that of forming the resin layer on the outer surface side of the tank. Material, a two-layer resin film made of an intrinsic viscosity (IV) of 0.83) and a polyethylene terephthalate resin (isophthalic acid copolymer, an intrinsic viscosity (IV) of 0.90) is coated on a container Face on the inner surface side. In addition, the thickness ratio between the content-side resin layer and the aluminum alloy substrate-side resin layer was 5: 5, and the thickness of the two resin films was 10 μm in the state of the resin-coated aluminum alloy plate (before can-making). Way to make it.

(Measurement of melting point of resin layer)
From the obtained resin-coated aluminum alloy plates, the surface-side resin layer and the aluminum-alloy base-side resin layer on the outer surface side of the can, and the content-side resin layer and the aluminum-alloy base-side resin on the inner surface side of the can were cut out respectively. The layer was measured using a DSC6000 model, differential scanning calorimeter (DSC) from Yamato Chemical Co., Ltd., Awa Chemical Corporation. From 0 to 290 ° C, the temperature was raised at a rate of 10 ° C / min, and the melting points were determined from the melting peaks. The results are shown in Table 1. In addition, in the measurement of the melting point of the resin layer formed on the outer surface side of the can, although there are a peak derived from PBT and a peak derived from PET, in this specification, the temperature of the higher peak temperature is used as the melting point of each resin layer. .

(Manufacture of two-piece aluminum cans)
A resin-coated aluminum alloy plate obtained as described above was coated with a wax-based lubricant, and a disc (blank) was punched and manufactured so that the aluminum alloy base resin layer and the surface layer resin layer became the outer surface of the tank. Make a can.

The canning process is performed in the following order. First, deep drawing is performed on the stamped disc (blank) to produce a shallow drawn cup. Next, an ironing process was performed on this shallow drawn cup to produce a seamless cup (reduction rate (reduction rate of the thickness of the side wall portion with respect to the original plate thickness)) of 60%.

For this seamless cup, the can body and the bottom of the can were formed according to a conventional method, and heat treatment was performed at 220 ° C. for 60 seconds. Next, after trimming the open end portion, neck processing and flange processing were performed to produce a tank body with an inner diameter of 202 (JIS (Japan Industry Standards)) and a neck diameter of 200 (JIS Specifications) 250ml seamless cans. Trimming refers to clamping the side wall of the tank with a circular cutter on the outside of the tank and a circular cutter on the inside of the tank, and rotating the cutter to cut around the entire circumference of the tank.

(Evaluation of abnormal color tone and resin voids)
The evaluation of abnormal color tone was performed by the following method after the two-piece aluminum can was produced. First, the two pieces of cans obtained were filled with 235 g of water, and the lids were tightened according to a conventional method to become filled packaging cans. The obtained filled packaging can was placed upright in a metal bucket (Vat), and the water level (gas-liquid interface) of the water was brought into contact with the side wall of the can 50 mm away from the bottom of the can, and stretched in water. In a state, in a sealed distillation kettle, a pressure heating sterilization treatment was performed at 140 ° C. for 5 minutes with steam. Water was used for rapid cooling after the pressure heating sterilization treatment. After that, the filled packaging can in the retort was taken out, and the abnormality in the color of the side wall of the can body on the outer surface of the can and the presence or absence of voids in the organic resin coating layer were evaluated visually.
S: There is almost no abnormal color tone, and no voids are generated, and it can be used practically.
A: Although there are some abnormal color tones, no voids are generated, which can be used practically.
B: Although there are many abnormal color tones, almost no voids are generated, and it can be used practically.
C: Significant tonal anomalies and voids are generated, and cannot be practically used.

(Evaluation of white spots)
The evaluation of white spots was performed by the following method after a two-piece aluminum can was produced. First, the two pieces of cans obtained were filled with 235 g of water, and the lids were tightened according to a conventional method to become filled packaging cans. The obtained packed packaging can was placed upside down in a retort so that the bottom surface of the can body could be evaluated. The sealed retort was subjected to pressure heating and sterilization treatment at 125 ° C by steam. 30 minutes. Water was used for rapid cooling after the pressure heating sterilization treatment. After that, the filled packaging can in the retort was taken out, and the presence or absence of white spots on the surface of the bottom portion of the can was evaluated visually.
A: The occurrence of white spots has not been confirmed, and it can be used practically.
C: The occurrence of white spots was confirmed, and it was not practically used.

[Table 1]

no.

Claims (6)

A two-piece aluminum can comprises: the two-piece aluminum can is formed by containing an aluminum plate on at least one side of an aluminum alloy substrate, and the aluminum plate sequentially has from the aluminum alloy substrate side: an inorganic surface treatment film, The system contains zirconium, fluorine and oxygen, and does not substantially contain phosphorus; the organic surface treatment film contains a water-soluble phenol resin; the resin layer contains a thermoplastic polyester resin; wherein, the mass is converted to carbon per unit area The amount of the organic surface treatment film is 3 mg / m ² or more and 20 mg / m ² or less. The two-piece aluminum can has the inorganic surface treatment film, the organic surface treatment film, and the at least the outer surface of the can. The resin layer is a mixed resin of a resin layer-based polyethylene terephthalate-based resin and a polybutylene terephthalate-based resin arranged on the outer surface side of the tank, and the polyterephthalic acid in the resin layer The content of the succinic resin is 20% by weight or more and 50% by weight or less. The two-piece aluminum can according to claim 1, wherein the adhesion amount of the inorganic surface treatment film is 3 mg / m ² or more and 25 mg / m ² or less in terms of zirconium atom-equivalent mass per unit area. The two-piece aluminum can according to claim 1 or 2, wherein the organic surface treatment film is a polymer having a repeating structure represented by the following formula (I), and the formula (I) is: [化 1] [In the formula (I), X is a hydrogen atom or a Z group represented by the following formula (II), and the formula (II) is: [Chem 2] (In the formula (II), R ¹ and R ² are each independently an alkyl group having 10 or less carbon atoms or a hydroxyalkyl group having 10 or less carbon atoms), and the introduction rate of the Z group per benzene Ring 0.3 to 1.0]; When X in the formula (I) is a hydrogen atom, the weight average molecular weight of the polymer is in the range of 1,000 to 100,000. The two-piece aluminum can according to any one of claims 1 to 3, wherein the melting point of the resin on the aluminum alloy substrate side of the resin layer is for the resin layer disposed on the outer surface side of the can of the aluminum alloy substrate It is higher than the melting point of the resin on the surface layer side. The two-piece aluminum can according to any one of claims 1 to 4, wherein the aluminum plate has an inorganic surface treatment film, an organic surface treatment film, and a resin layer on both sides; In the resin layer, the melting point of the resin on the content side of the resin layer is higher than the melting point of the resin on the inner surface side of the can of the aluminum alloy substrate. The two-piece aluminum can according to any one of claims 1 to 5, wherein the two-piece aluminum can is formed by drawing and ironing.