JPH07101010A - Laminated film for laminating and molding metal plates - Google Patents

Abstract

PURPOSE:To provide a laminated film which has excellent molding processability in the case of can making such as drawing by laminating with a metal plate, impact resistance after can making, and perfume retentivity of a content. CONSTITUTION:The laminated film is formed by laminating a copolymer polyester layer (A) having a melting point of 210 245 deg.C and a glass transition temperature exceeding 60 deg.C and a copolymer polyamide layer (B) containing a ubricant having a mean particle size of 2.5mum or less, a melting point of 210-245 deg.C and a glass transition temperature exceeding 60 deg.C in such a manner that, when the layer (B) is laminated on a metal plate, it is disposed at the side to be adhered to the plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film for laminating and forming metal plates, and more specifically, it shows excellent forming processability when it is laminated with a metal plate to perform can manufacturing such as drawing.
Further, the present invention relates to a laminated film for metal plate laminating and forming, which is resistant to cracking from the outside of the can even when subjected to a heat treatment such as retort sterilization after the can is made, and has excellent aroma retaining property of the contents.

[0002]

2. Description of the Related Art Metal cans are generally painted to prevent corrosion on the inside and outside, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention without the use of organic solvents The development of a method for obtaining the property has been advanced, and as one of them, coating with a thermoplastic resin film has been attempted. That is,
A method of making a can by laminating a thermoplastic resin film on a metal plate such as tin plate, tin-free steel, aluminum or the like and then making a can is under study. Polyolefin films and the like have been tried as the thermoplastic resin films, but they do not satisfy the molding processability, heat resistance and impact resistance.

On the other hand, a polyester film, particularly a polyethylene terephthalate film, has attracted attention as having balanced properties, and several proposals based on this have been made. That is, (A) Biaxially oriented polyethylene terephthalate film is laminated on a metal plate via an adhesive layer of low melting point polyester and used as a can-making material. (JP-A-56-104
No. 51, JP-A-1-192546) (B) An amorphous or extremely low crystalline aromatic polyester film is laminated on a metal plate and used as a can-making material. (JP-A-1-192545, JP-A-2-5
No. 7339) (C) A biaxially oriented polyethylene terephthalate film having a low orientation and heat set is laminated on a metal plate and used as a can-making material. (Japanese Patent Laid-Open No. 64-22530)

However, none of these methods provided sufficient characteristics, and it became clear that each of the methods had the following problems. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance, but the moldability is insufficient, and whitening (generation of microcracks) and breakage of the film occur in can manufacturing with large deformation. .
Regarding (B), since it is an amorphous or extremely low crystalline aromatic polyester film, it has good moldability, but it is easily embrittled by post-processing such as printing after can-making and retort sterilization treatment, and It is transformed into a film that is easily cracked by the impact from the outside. Regarding (C), the effect is not exerted in the intermediate region between (A) and (B), but since the film surface isotropicity is not guaranteed, it seems to be a can-making process (deep drawing process). However, when the film is deformed in all directions, the workability of the film may be insufficient in a specific direction of the film. Further, since polyethylene terephthalate film is inherently hydrophobic, it does not adhere sufficiently to a hydrophilic metal plate such as tin-free steel, and it may be unusable due to delamination during can manufacturing.

[0005]

DISCLOSURE OF THE INVENTION As a result of studies to develop a film for can-making processing which does not have these problems, the present inventors have found that a layer of copolyester and a layer of copolyamide are laminated and By laminating it with the metal plate so that the layer of the polymerized polyamide is on the side in contact with the metal plate, it is possible to obtain a laminated film for can manufacturing that is excellent in moldability, heat resistance, impact resistance, and aroma retention. Heading, arrived at the present invention.

[0006]

That is, according to the present invention, a layer (A) of a copolyester having a melting point of 210 to 245 ° C. and a glass transition temperature of more than 60 ° C. and an average particle diameter of 2.5 μm.
A layer of a copolyamide (B) containing the following lubricant, having a melting point of 210 to 245 ° C. and a glass transition temperature of 60 ° C. or less, is laminated, and the layer (B) of the copolyamide is a metal plate. It is a laminated film for metal plate laminating and forming, characterized by forming a layer on the side which comes into contact with the metal plate at the time of laminating with.

The layer (A) in the present invention is composed of a copolyester having a polymer melting point of 210 to 245 ° C. and a glass transition temperature of more than 60 ° C., and isophthalic acid-copolymerized polyethylene terephthalate is particularly preferable from the viewpoint of aroma retention.

The polymer melting point of the copolyester is 21.
If it is less than 0, the heat resistance is inferior, so that it cannot withstand heating in printing after can making, while if the polymer melting point exceeds 245 ° C., the crystallinity of the polymer is too high and the molding processability is impaired. Here, the melting point of the copolyester is measured by Du Pont Instruments 91.
According to a method of obtaining a melting peak at a temperature rising rate of 20 ° C./min using 0 DSC. The sample amount is about 20 mg.

When the glass transition temperature of the copolyester is 60 ° C. or lower, the aroma retaining property of the film deteriorates. Here, the second-order transition point of the polyester is "Vibron direct reading dynamic viscoelasticity measuring instrument DDV-II" manufactured by Toyo Baldwin Co., Ltd.
The temperature distribution and tan δ are measured by the “type”, the dynamic loss elastic modulus (E ″) is obtained based on the measured value of tan δ, and the temperature at which the E ″ value becomes maximum is obtained as the second-order transition point. The measurement condition at this time is a driving frequency of 110 cps, and the temperature rising rate is 1 ° C./minute, and the temperature is started from room temperature. The measurement sample is prepared by preparing a thin film having a width of 5 mm, a length of 20 mm and a thickness of 0.2 mm from the molten polymer, cooling immediately after forming the film, and allowing it to stand at room temperature for 3 days or more. At this time, when the film has a thickness unevenness, the measured values are slightly different. Therefore, each of the five sample films prepared separately is measured, and the average value of the five measured values is determined as the second-order transition point.

The catalyst used in the polycondensation reaction of the copolyester in the present invention is not particularly limited, but antimony compounds, titanium compounds, germanium compounds and the like are preferable.

The layer (B) in the present invention contains a lubricant having an average particle size of 2.5 μm or less and has a melting point of 210 to 24.
It is composed of a copolyamide having a glass transition temperature of 5 ° C. and a glass transition temperature of 60 ° C. or less, and a copolymer polycapramide or a copolymer polyhexamethylene adipamide is particularly preferable from the viewpoint of the polymer melting point. If the glass transition temperature of the polymer exceeds 60 ° C., the impact resistance deteriorates. The kinds and amounts of the components to be copolymerized with polycapramide or polyhexamethylene adipamide are preferably selected so that the melting point of the polymer and the glass transition temperature are within a predetermined range.

The layer (B) of the copolyamide in the present invention contains a lubricant having an average particle size of 2.5 μm or less.
This lubricant may be inorganic or organic, but is preferably inorganic. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate, and the like, and examples of the organic lubricant include silicone resin particles. Both require that the average particle size is 2.5 μm or less. If the average particle size of the lubricant exceeds 2.5 μm,
Coarse lubricant particles (for example, particles having a particle size of 10 μm or more) in a portion deformed by processing such as deep-drawing can are used as a starting point to generate pinholes or, in some cases, break, which is not preferable.

The amount of the lubricant in the copolyamide may be determined depending on the winding property and the deep drawing processability in the film manufacturing process. Generally, it is preferable to add a small amount of particles having a large particle size and a large amount of particles having a small particle size. For example, it is preferable to add about 0.05% by weight in the case of silica having an average particle size of 2.0 μm, and about 0.3% by weight in the case of titanium dioxide having an average particle size of 0.3 μm. Further, the film can be made opaque by intentionally adjusting the content of the lubricant. For example, a white film can be obtained by adding 10 to 15% by weight of titanium dioxide.

In the laminated film of the present invention, it is necessary that the layer (B) of the copolyamide is placed on the side in contact with the metal plate when it is attached to the metal plate. On the contrary, when the layer (A) of the copolyester is attached to the metal plate so that the layer (A) is in contact with the metal plate, the impact resistance and aroma retention after the can-making process are significantly deteriorated. Excellent impact resistance and aroma retention can be exhibited only by laminating the layer (B) of the copolyamide with the metal plate so that the layer is in contact with the metal plate.

The lubricant is a layer of copolyamide (B).
It is necessary to add only to. When a lubricant is added to the layer (A) of the copolyester in contact with the contents of the can, the surface of the layer (A) of the copolyester becomes rough and the aroma component in the contents of the can is easily adsorbed. The aroma is deteriorated.

The laminated film of the present invention comprises a layer (A) of the above-mentioned copolyester and a layer (B) of the copolyamide.
Is a laminated film in which As a method of stacking,
Examples include a method in which the polyester resin (A) and the polyamide resin (B) are independently melted and coextruded from an adjacent die, a method in which the copolymerized polyester film (A) and the copolymerized polyamide film (B) are laminated, and the like. To be

The laminated film of the present invention preferably has a thickness of 6 to 75 μm. 10 to 75 μm, especially 1
It is preferably 5 to 50 μm. This thickness is 6 μm
If it is less than 75 μm, tearing is likely to occur during processing, while 75μ
Those exceeding m are excessive quality and are uneconomical.

In the laminated film of the present invention, the ratio (T _B / T _A ) of the thickness T _A of the layer (A) of the copolyester and the thickness T _B of the layer (B) of the copolyamide is 0.
1-5 are preferable and 0.3-2 are especially preferable.

A tin plate, tin-free steel, aluminum plate or the like is suitable as a can-making metal plate to which the laminated film of the present invention is laminated. The laminating film can be attached to the metal plate by the following method, for example.

The metal plate is heated above the melting point of the film and the laminated film is laminated so that the copolyamide layer is in contact with the metal plate and then cooled, and the surface layer (thin layer) of the copolyamide layer in contact with the metal plate is cooled. Part) is made amorphous and adheres closely.

An adhesive layer is preliminarily coated with a primer on the copolyamide layer (B) side of the laminated film,
The metal plate is attached to this surface. As the adhesive layer, a known resin adhesive such as an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used.

[0022]

EXAMPLES The present invention will be further described below with reference to examples. In addition, "part" in an Example means a weight part. Moreover, the measurement of each characteristic value followed the following method.

The film was heated to 260 ° C. to obtain a plate thickness of 0.
The layer (B) of the copolyamide is attached to 25 mm tin-free steel, water-cooled, cut into a disc shape with a diameter of 150 mm, and deep-drawn in two steps using a drawing die and punch, and with a diameter of 55 mm. A side seamless container (hereinafter abbreviated as a can) was created. The following observations and tests were performed on this can, and the following standards were used for evaluation.

(1) Deep drawing workability-1 ○: The inner and outer surfaces of the film were processed without any abnormality, and no whitening or breakage was found on the inner and outer surfaces of the can. Δ: Whitening is observed on the inside of the can and on the top of the can of the film. X: Film rupture is recognized in a part of the film inside and outside the can.

(2) Deep drawing workability-2 ○: Both the inner and outer surfaces were processed without abnormality, and the rust prevention test of the film surface inside the can (1% NaCl water was put in the can, the electrode was inserted, and the can body was The current value is measured when a voltage of 6 V is applied as an anode, which is 0.1 mA in the ERV test.
The following is shown. X: There is no abnormality in the film on both the inner and outer surfaces, but the current value is 0.1 mA or more in the ERV test, and pinhole-like cracks originating from the coarse lubricant are observed in the film when the energized portion is enlarged and observed.

(3) Impact crack resistance With respect to cans with good deep drawing, water was fully poured, and 10 bottles were dropped from the height of 1 m to the PVC tile floor for each test. As a result, ◯: 0.1 mA or less for all 10 pieces. (Triangle | delta): It was 0.1 mA or more about 1-5 pieces. X: 0.1 mA or more for 6 or more, or cracks of the film were already observed after dropping.

(4) Heat embrittlement resistance After the cans that had been well-formed by deep drawing were heated and held at 210 ° C. for 5 minutes, the above impact resistance was evaluated. ◯: 0.1 mA for all 10 It was below. (Triangle | delta): It was 0.1 mA or more about 1-5 pieces. ×: 0.1 mA or more for 6 or more, or cracks were already observed in the film after heating at 210 ° C. for 5 minutes.

(5) Resistance to retort The cans, which were well formed by deep drawing, were refilled with water and subjected to retort treatment at 130 ° C. for 1 hour in a steam sterilizer, and then stored at 50 ° C. for 30 days. After dropping 10 of the obtained cans from the height of 1 m on the PVC tile floor surface for each test, an ERV test in the cans was performed. ◯: 0.1 mA or less for all 10 cans. (Triangle | delta): It was 0.1 mA or more about 1-5 pieces. X: 0.1 mA or more for 6 or more, or cracks of the film were already observed after dropping.

(6) Anticorrosion A can of good deep-drawing was filled with 5% acetic acid aqueous solution, kept at 50 ° C. for 7 days, and then evaluated for rust generation on the metal plate. Occurrence of rust was observed for 10 pieces. Δ: Rust generation was observed for 1 to 5 pieces. X: Rust generation was observed for 6 or more pieces.

(7) Aroma Retaining Property A can having good deep drawing was filled with 10 ciders or 10 bottles of mineral water and sealed. After keeping at 37 ° C. for 4 months, it was opened and sensory-tested for changes in aroma and taste. ⊚: There was no change in aroma and taste. ◯: There were 1-2 scents and tastes that were slightly changed. Δ: There were 5 to 6 fragrances / tastes that were slightly changed. X: Changes in fragrance and taste were recognized in all 10.

[0031]

Examples 1 to 3 Copolyester (A) shown in Table 1
The copolyamide (B) and the copolyamide (B) were independently dried and melted, and then coextruded through an adjacent die and rapidly solidified to obtain an unstretched laminated film.

The unstretched film was then heated at 115 ° C. for 3 hours.
After longitudinally stretching twice, it was laterally stretched three times at 130 ° C. and then heat-set at 180 ° C. to obtain a biaxially oriented laminated film. The thickness of the film was 25 μm, and the thicknesses of the copolyester layer (A) and the copolyamide layer (B) were 10 μm and 15 μm, respectively. The above-mentioned various evaluations were carried out on this laminated film. The results are shown in Table 2, which were all good.

[0033]

Comparative Example 1 The procedure of Example 1 was repeated except that the copolymerization component of the copolyester (A) was changed to sebacic acid. The results are shown in Table 2.

[0034]

Comparative Examples 2 to 3 The procedure of Example 1 was repeated except that the composition of the copolyester (A) was changed as shown in Table 1.
The results are shown in Table 2.

[0035]

Comparative Example 4 The procedure of Example 1 was repeated except that the isophthalic acid copolymerized polyethylene terephthalate shown in Table 1 was used instead of the copolymerized polyamide (B). The results are shown in Table 2.

[0036]

[Comparative Example 5] The same procedure as in Example 1 was repeated except that 0.1% by weight of spherical monodisperse silica having an average particle diameter of 2.8 μm was used in place of the spherical monodisperse silica having an average particle diameter of 1.5 μm as a lubricant. It was The results are shown in Table 2.

[0037]

Comparative Example 6 Copolyester (A) has an average particle size of 1.
Example 1 was repeated except that 0.2% by weight of 5 μm spherical monodisperse silica was added. The results are shown in Table 2.

[0038]

Comparative Example 7 The procedure of Example 1 was repeated except that the layer (A) of the copolyester was bonded to tin-free steel. The results are shown in Table 2.

[0039]

[Table 1]

[0040]

[Table 2]

However, the symbols in the table are as follows.

PET Polyethylene terephthalate IA Isophthalic acid SA Sebacic acid Ge Germanium catalyst Ti Titanium catalyst Sb Antimony catalyst PC Polycapramide PHMA Polyhexamethylene adipamide

[0043]

INDUSTRIAL APPLICABILITY The laminated film for laminating and forming metal plates according to the present invention has a deep drawing workability and a can forming property in forming a metal can by forming a can, for example, by deep drawing after laminating with a metal plate. It is excellent in impact resistance, heat resistance, retort resistance, rust resistance, aroma retention, etc., and is extremely useful for metal containers.

Claims (3)

[Claims] 1. A layer comprising a copolymerized polyester (A) having a melting point of 210 to 245 ° C. and a glass transition temperature of more than 60 ° C. and a lubricant having an average particle size of 2.5 μm or less, and having a melting point of 210 to 210.
A side which is formed by laminating a layer (B) of a copolyamide having a glass transition temperature of 245 ° C. and a glass transition temperature of 60 ° C. or lower, and the layer (B) of the copolyamide is in contact with the metal plate when it is attached to the metal plate. A laminated film for laminating and forming metal plates, which is characterized by the following layers. 2. The laminated film for laminating and molding metal plates according to claim 1, wherein the layer (A) of the copolyester is made of isophthalic acid copolyethylene terephthalate. 3. The laminated film for metal sheet laminating and forming according to claim 1, wherein the layer (B) of the copolyamide comprises a copolycapramide or a polyhexamethylene adipamide.