JPH07304145A - Film for metal laminating and forming - Google Patents

Abstract

PURPOSE:To obtain a film which is superior in moldability of deep drawing processing and shock resistance and adhesion after retort treatment. CONSTITUTION:The title film is comprised of a copolymer polyester film whose melt peak temperature of a polymer is 210-245 deg.C, face orientation properties are 0.100-0.125, crystalline size is 35-80 angstroms and concentration of a terminal carboxyl group of the polymer is not exceeding 35 equivalent/ton.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for metal laminating and forming. More specifically, a film for metal laminating and forming, which can be attached to a metal plate and subjected to drawing, folding, etc., particularly a beverage can,
The present invention relates to a metal laminating and forming film that can be used for a can body such as a food can, a can bottom, and a can lid.

[0002]

2. Description of the Related Art Conventionally, a metal is generally coated to prevent corrosion, but a method for obtaining a rust preventive property without using an organic solvent has been developed. That is, (1) a method of laminating a biaxially oriented polyethylene terephthalate film via an adhesive layer of low melting point polyester and using it as a can-making material (JP-A-56-10451, JP-B-1-192).
No. 546, etc.), (2) A method of laminating an amorphous or low crystalline aromatic polyester film on a metal plate and using it as a can-making material (JP-A-1-192545, JP-A-2-192545).
-57339), and (3) a method of laminating a low orientation polyethylene terephthalate film on a metal plate and using it as a can-making material (Japanese Patent Laid-Open No. 64-22530).
Have been proposed.

However, the above method (1) is in terms of molding processability, the method (2) is in terms of aroma retention and embrittlement over time, and the method (3) is in method (1). Similarly, it is insufficient in terms of molding processability and has not been put into practical use.

In view of such a situation, Japanese Patent Laid-Open No. 5-339.
Japanese Patent No. 348 discloses that the amount of carboxyl end groups is 35 equivalents /
A metal laminating and forming film made of a polyester film having a capacity of not less than ton has been proposed.

[0005]

However, the film proposed in the above-mentioned Japanese Patent Laid-Open No. 5-339348 has excellent adhesiveness to metal and molding processability,
There is a problem that the impact resistance, particularly after the retort treatment, is poor.

The present invention focuses on such problems and provides a film for metal-bonding molding which is excellent in molding processability (can-making property) and particularly excellent in impact resistance before and after retort treatment. With the goal.

[0007]

A film for metal laminating and forming according to the present invention which meets the above object has a polymer melting peak temperature of 210 to 245 ° C. and a plane orientation of 0.100 to 100.
0.125, the crystal size is 35 to 80 angstroms, and the terminal carboxyl group concentration of the polymer is 35 equivalents /
Ton or less of a copolyester.

[0008] In this metal laminating and forming film, it is preferable that the surface wetting tension be 46 dyne / cm or more by performing an electric discharge treatment in order to secure good adhesiveness.

Further, the film of the present invention has a basic structure of a single layer film, but may have a laminated film structure. That is, on one side of the above-mentioned copolyester layer,
It has a copolymerized polyester layer having a polymer melting peak temperature of 1 ° C. or higher, a plane orientation of 0.105 to 0.115, and a terminal carboxyl group concentration of 35 equivalents / ton or less than the polyester layer. A film for laminating and forming a metal having a laminated structure, which serves as a heat-bonding layer. In other words, it is a form in which layers whose main purpose is thermal bonding are laminated.

Typical examples of the copolymerized polyester in the film of the present invention include copolymerized polyethylene terephthalate. As a typical example of copolymerized polyethylene terephthalate, as a copolymerization component, an acid component is an aliphatic dicarboxylic acid such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, or isophthalic acid, phthalic acid, 2,6- Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,5′-naphthalenedicarboxylic acid, and aliphatic diols such as diethylene glycol, propylene glycol, neopentyl glycol, butanediol, and hexanediol as alcohol components. , Polyethylene glycol, polypropylene glycol, and other polyalkylene glycols. These are single or 2
It is possible to use more than one kind. It is also possible to blend with the various copolymerized polyethylene terephthalates shown here.
The polymer viscosity (intrinsic viscosity) is preferably 0.45 to 1.5, more preferably 0.5 to 0.8.

Examples of transesterification catalysts for these copolyesters include Mg, Mn, Zn, Ca, Li and Ti, with Ti being preferred. Examples of the polymerization catalyst include antimony compounds, titanium compounds, germanium compounds and the like, and among them, germanium compounds are preferable. Further, as a polymerization method, a transesterification method (DM
Although the T method) can be used, the esterification method (direct weight method) is also preferably applied.

Further, the above-mentioned copolyester layer may contain particles as a lubricant, if necessary. Either inorganic particles or organic particles can be used, and examples of the inorganic particles include true spherical silica, agglomerated silica, synthetic / natural calcium carbonate, true spherical calcium carbonate, titanium dioxide, and barium sulfate. Examples thereof include crosslinked / non-crosslinked acrylic, polyethylene, imide, amide, silicone, fluorine and olefin particles. The organic particles may be crosslinked or non-crosslinked. It is also possible to use internal protrusion particles. Further, these particles can be used alone or in a mixed form of two or more kinds.

The average particle size of these particles is not particularly limited, but is preferably 2.5 μm or less. When two or more types of particles are combined, a combination of particles having an average particle size of 0.5 μm or less and particles having an average particle size of more than 0.5 μm is suitable.

In the film for metal laminating and forming according to the present invention, the polymer melting peak temperature of the copolyester needs to be in the range of 210 to 245 ° C. If the melting peak temperature is less than 210 ° C, heat resistance is insufficient, and if it exceeds 245 ° C, moldability is insufficient.

The copolyester has a surface orientation of 0.100 to 0.1 in the copolyester layer.
The range is 25. When the plane orientation is less than 0.100,
The impact resistance after molding is insufficient, and when it exceeds 0.125, the moldability is insufficient.

The crystal size of the copolyester layer is in the range of 35 to 80 angstroms. If the crystal size is less than 35 Å, heat resistance will be insufficient, and if it exceeds 80 Å, moldability will be insufficient.

Further, the terminal carboxyl group concentration of the polymer in this copolymerized polyester is adjusted to 35 equivalents / ton or less. Those of 35 equivalents / ton or less can exhibit excellent adhesiveness and impact resistance after retort treatment. If it exceeds 35 equivalents / ton, the impact resistance after retort treatment may be insufficient.

As described above, in the metal laminating and forming film according to the present invention, the polymer melting peak temperature,
By controlling the surface orientation, crystal size, and terminal carboxyl group concentration within a specific range, the adhesiveness,
It becomes possible to maintain good properties in a well-balanced can-making property and impact resistance after retort treatment.

Further, in the film according to the present invention, it is preferable that the wetting tension of the surface thereof is 46 dyne / cm or more in order to secure good adhesiveness. Such a wetting tension can be achieved by subjecting the surface of the film made of the above-mentioned copolymerized polyester to an electric discharge treatment.

In the film according to the present invention,
If necessary, additives other than those mentioned above, for example, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, colorants, pigments, whitening agents and the like may be added.

The thickness of the film of the present invention is 2
A range of up to 150 μm is suitable. Preferably 8 to 60
μm, and more preferably 12 to 40 μm.

Typical examples of the metal plate to which the film of the present invention is attached include tin plate, tin-free steel, aluminum, and the like. The surface of these metal plates may be appropriately subjected to organic or inorganic treatment.

Next, a typical method for producing the film of the present invention will be illustrated. Specified viscosity (usually 0.45 at limiting viscosity)
To 1.50), the resin A and B having the same is appropriately lubricated, and then dried to 400 ppm or less, preferably 80 ppm or less. The dry raw materials A and B are melt mixed using an extruder. When an extruder having degassed holes is used, drying may be omitted, or various additives may be added during the extruder. A blend of the resins A and B in a molten state is discharged from a die in a sheet form, cooled once on a cooling roll, and then,
In the range of 60 to 135 ° C, the film is stretched in the longitudinal direction 2.0 to 6.0 times, then in the range of 60 to 140 ° C in the transverse direction 2.0 to 6.0 times, and in the range of 120 to 240 ° C. Heat treatment is performed while relaxing as necessary to obtain a biaxially stretched film. After biaxial stretching, it is preferable to subject the film surface to corona discharge treatment in various atmospheres if necessary.

[Measurement method] (1) Deep drawing workability (canning property) After a predetermined film was attached to tin-free steel heated to 245 ° C, it was cooled with a cooling roll from the film side and then water-cooled. . The film-bonded metal plate thus obtained is cut into a disk shape having a diameter of 180 mm, and then the film surface is formed into an inner surface using a heat molding machine to form a drawing ratio of 1.25. The can thus obtained is subjected to a visual judgment and a rust prevention test. Rust resistance is 1%
NaCl water was put into a can, the can body was used as an anode, and the cathode was inserted in NaCl. There was no appearance abnormality, and the current value was determined to be “◯” when the current value was 0.25 mA or less, and was determined to be “x” otherwise. ○ was judged to be practically usable.

(2) Impact resistance A deep-drawing can made under the conditions of (1) is filled with water and then sealed. 30 pieces of canned products, which had been dried at 220 ° C. for 3 minutes and then subjected to retort treatment at 125 ° C. for 3 hours, were dropped on a floor inclined at 15 ° from a height of 1.4 m for each 30 pieces. After that, the rust preventive property is evaluated according to the following criteria under the condition described in (1). Total number 0.20 mA or less: ○ Other than that: ×

(3) Melting peak temperature Using a DSC (Differential Scanning Calorimeter) manufactured by Perkin Elmer, the temperature was measured at a heating rate of 10 ° C./min.

(4) Terminal carboxyl group concentration HIRANUMA COMMITITE-7 REPORT
Using the ING TITRETOR, a silver chloride composite electrode is used, a supersaturated potassium chloride aqueous solution is filled, and calculation is performed based on the following formula. COOH (equivalent / ton) = [(A−B) × C × F] / S where A: NaOH titer of sample (ml) (normality = N / 50−NaOH / methanol) B: NaOH of blank Titration amount (ml) C: 20 (20 = N / 50 × 1/1000 × 1)
0 ⁰ ) F: Factor (determined by a benzoic acid / methanol solution) S: Sampling amount (g)

(5) Plane Orientation The measurement was carried out in an atmosphere of 25 ° C. using an Abbe refractometer, a monochromatic sodium D ray as a light source, and methylene iodide as a mount solution. It was determined by subtracting the refractive index in the thickness direction from 1/2 of the sum of refractive indices in the surface direction (vertical and horizontal directions).

(6) Crystal size Measured by wide-angle X-ray diffraction. Obtained by the reflection method,
(01) of polyester observed near 2θ = 26 °
It was calculated from the full width at half maximum of the peak on the 0) plane using the Scherrer's formula below. L (hkl) = Kλ / (β ₀ cos θ _B ) where L (hkl): average size in the direction perpendicular to the (hkl) plane of the crystallites λ: X-ray wavelength β ₀ = (β _E ² − β _I ² ) ^1/2 β _E : Apparent half width (measured value) β _I : 2.093 × 10 ⁻³ rad. θ _B : Bragg angle

(7) Wetting tension It was measured according to JIS-6768.

[0031]

【Example】

Examples 1 to 3 and Comparative Examples 1 to 4 As the resin A, the acid component is terephthalic acid (TPA) and isophthalic acid (IPA), and the alcohol component is ethylene glycol (EG) and diethylene glycol (DE).
G), which comprises 0.1 of aggregated silica having an average particle size of 0.4 μm
A polyester (IV = 0.75) added with 0% by weight is used.

The above resin A was supplied to an extruder, melt-extruded at 270 ° C., and cast as a sheet. This unstretched sheet was longitudinally stretched at the stretching temperature and the stretching ratio shown in Table 1, and the obtained uniaxially stretched film was introduced into a tenter,
The film was transversely stretched at the stretching temperature and the stretching ratio shown in. The biaxially stretched film was once cooled and then heat-set while being subjected to a relaxation treatment at the temperature and the relaxation rate shown in Table 1. The treatment strength of the film thus obtained is changed in air and CO
_The discharge treatment was performed in ₂ (only in Example 3).

Table 2 shows the characteristics of the obtained film and the evaluation results of the molded product laminated with the metal plate. Films satisfying the relationships specified in the present invention were excellent in can-making property and impact resistance (Examples 1 to 3), but films out of the relationship of the present invention satisfied impact resistance. Could not be made (Comparative Examples 1 to 4).

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As described above, the film for metal laminating and forming process of the present invention has a melting peak temperature, a plane orientation and a crystal size in a specific range and a terminal carboxyl group concentration of 35 equivalents / Since the film is made of a copolymerized polyester having a ton or less, it is possible to improve adhesiveness and impact resistance, particularly impact resistance after retort treatment, while ensuring excellent moldability such as deep drawing.

Claims (3)

[Claims] 1. A polymer melting peak temperature of 210 to 245.
C., a plane orientation of 0.100 to 0.125, a crystal size of 35 to 80 angstroms, and a terminal carboxyl group concentration of the polymer is 35 equivalents / ton or less. Film for combined molding. 2. The film for metal laminating and forming process according to claim 1, wherein the wetting tension of the surface is 46 dyne / cm or more. 3. One side of the copolyester layer has a polymer melting peak temperature of 1 ° C. or more higher than that of the polyester layer, a plane orientation of 0.105 to 0.115, and a terminal carboxyl group concentration of 35 equivalents / ton or less. The film for metal laminating and forming according to claim 1 or 2, wherein the film has a copolyester layer as described above, and the polyester layer is a heat-bonding layer.