JPH08311213A - Film for lamination with metallic sheet - Google Patents

Abstract

PURPOSE: To obtain a film used for lamination with a metallic sheet and being excellent in moldability such as deep drawability and impact resistance. CONSTITUTION: The film for lamination with a metallic sheet, mainly made from a copolyester having a polymer melting peak temperature of 210-257 deg.C and two subpeak temperatures of 100-210 deg.C and having a face orientation of 0.100-0.165, an intrinsic viscosity of 0.45-1.5, a centerline average roughness on at least one surface of 0.01-0.15μm, and a difference of the maximum and minimum values of a refractive index in the in-plane direction of 0.04 or below is provided.

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, it is a film for metal laminating and forming which can be attached to a metal plate and subjected to drawing and / or ironing, folding, etc., especially for can bodies such as beverage cans, food cans, can bottoms, can lids. The present invention relates to a metal laminating and forming film capable of being laminated, and a metal-film laminate obtained by drawing and / or ironing.

[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 a 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.

[0004]

SUMMARY OF THE INVENTION The present invention focuses on such problems, and is excellent in forming processability (can-making property), and in particular, metal bonding forming process excellent in impact resistance before and after retort treatment. The purpose is to provide a film for use.

[0005]

The 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 257 ° C. and a sub peak temperature of 10 ° C.
The main component is a copolyester having two peak temperatures in the range of 0 to 240 ° C., and the plane orientation is 0.100 to
0.165, intrinsic viscosity 0.45 to 1.5, center line average roughness of at least one surface of 0.01 to 0.15 μm, difference between maximum and minimum in-plane refractive index of 0.04 It is characterized by the following.

Examples of the polyester in the film of the present invention include homopolyester and various copolyesters. A typical example is copolymerized polyethylene terephthalate. As a typical example of copolymerization polyethylene terephthalate, as a copolymerization component,
Acid component is an aliphatic dicarboxylic acid such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, or
Aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,5′-naphthalenedicarboxylic acid, and alcohol components such as diethylene glycol, propylene glycol, neopentyl glycol, Butanediol,
It is composed of an aliphatic diol such as hexanediol and a polyalkylene glycol such as polyethylene glycol and polypropylene glycol. These may be used alone or in combination of two or more. It is also possible to blend with the various copolymerized polyethylene terephthalates shown here. The polymer viscosity (intrinsic viscosity) is 0.45 to 1.
5 and preferably 0.60 to 0.8.

Examples of transesterification catalysts for these copolyesters include Mg, Mn, Zn, Ca, Li and Ti, among which Ti is 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 (DMT method) can be used, but an esterification method (direct weight method) is more preferable.

Further, the above-mentioned copolyester layer may contain particles as a lubricant within the scope of the present invention. Both inorganic particles and organic particles can be used. Examples of the inorganic particles include zeolite, true spherical silica, agglomerated silica, synthetic / natural calcium carbonate, true spherical calcium carbonate, titanium dioxide, barium sulfate, and the like. Examples of the particles 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. In addition, examples of the poorly compatible resin that can be mixed include polyethylene, polypropylene, polyvinyl alcohol, acryl, polycarbonate, 4 methylpeniran-1, polyphenylene sulfide and the like.

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 molding according to the present invention, a copolyester having a polyethylene terephthalate / isophthalate copolymer as a main component is suitable, and a polymer melting peak temperature is 210.
It is necessary to be in the range of ˜257 ° C. If the melting peak temperature is less than 210 ° C, heat resistance is insufficient, and if it exceeds 257 ° C, moldability is insufficient.

Further, in the present invention, the sub-peak temperature Ts (° C.) generated by the transformation of the quasicrystal, which occurs when the melting characteristics of the above-mentioned polymer is measured, is also defined, and it is 100-
It is necessary to have two peaks in the range of 240 ° C. In this way, by defining the sub-peak temperature Ts in the specific range and the specific peak number,
The target heat resistance and moldability can be secured more reliably.

Further, in the film of the present invention, the center line average roughness of at least one surface, that is, the drawing and / or ironing surface is 0.01 to 0.15 μm. This surface is a surface forming the inner surface of the can when the film of the present invention is applied to a beverage can or the like, for example. By giving this surface a specific range of surface roughness, it has good formability in drawing and / or ironing, and when the contents of the can are, for example, carbonated beverages, bubbles are formed on the fine protrusions on the inner surface of the can. It can be finely dispersed and adhered uniformly.

More specifically, regarding the surface roughness of the film, the film is heat-laminated with a steel sheet to form a metal film.
When forming a film laminate, the non-thermal laminating side forming the inner surface of the can has a center line average roughness R _{1A in} the range of 0.01 to 0.15 μm as described above, and the center of the opposite thermal laminating surface. The average roughness R _2A is not particularly limited, but is 0.0
The range of 1 to 0.50 μm is preferable. However, at this time, R
It is also preferable that _1A <R _2A , in addition to improving the film processability, and that the surface on the non-thermal laminating side satisfies the moldability and the required properties for the content after the molding as described above.

The plane orientation of the film layer made of this copolyester is in the range of 0.100 to 0.165. If the surface orientation is less than 0.100, the impact resistance after molding is insufficient, and if it exceeds 0.165, the moldability deteriorates. 0.120-0.1 from the viewpoint of stability of impact resistance
A range of 45 is more preferable.

Further, in the present invention, the difference between the maximum value and the minimum value of the in-plane direction refractive index is 0.04 or less. That is, the film has a good in-plane isotropic property even after the orientation, so that a good molding processability can be exhibited.

Further, the film of the present invention basically has a single-layer film, but a laminated film (composite film).
It can also be configured.

For example, a layer containing a polybutylene terephthalate resin on at least one surface (thermally laminated surface) of the above single-layer film (for example, polybutylene /
By laminating a layer made of an isophthalate copolymer), it is possible to improve the thermal laminating property on the surface of the steel sheet. In addition, by stacking layers made of two or more types of polymers having poor compatibility with each other, the presence of polymer particles having poor compatibility forms voids around the particles to whiten the film, or Surface protrusions can be formed, and characteristics corresponding to required characteristics can be exhibited.

Further, in the film of the present invention, when the carboxyl group concentration is 35 equivalents / ton or less, it is suitable from the standpoint of improving impact resistance, particularly impact resistance after retort treatment. It is also possible to exhibit excellent molding processability for use.

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.

Further, the film of the present invention can be made into a metal-film laminate by laminating it to a steel plate (metal plate) by thermal lamination. Representative examples of the metal plate to which the film of the present invention is attached include tin plate, tin-free steel, and aluminum. The surface of these metal plates may be appropriately subjected to organic or inorganic treatment. In this laminated body,
The degree of film surface orientation on the non-steel side of the film is 0.8 to
After setting to 2.0, it is preferable to perform predetermined drawing and / or ironing.

Next, a typical method for producing the film of the present invention will be illustrated. Specified viscosity (typically 0.45 at intrinsic viscosity)
~ 1.50) to the resin having a suitable lubricant formulation,
Dry to 400 ppm or less, preferably 80 ppm or less. The dry raw material is melted using an extruder. When an extruder having degassed holes is used, drying may be omitted, or various additives may be added during the extruder. The resin is discharged in a molten state in a sheet form from a die, cooled once on a cooling roll, and then 2.0 to 2.0 at 60 to 135 ° C.
After stretching 6.0 times in the longitudinal direction, it is stretched in the transverse direction in the range of 60 to 140 ° C in the range of 2.0 to 6.0 times, once cooled if necessary, and in the range of 120 to 240 ° C. Heat treatment is performed while relaxing accordingly to obtain a biaxially stretched film. After biaxial stretching, it is preferable to subject the film surface to corona discharge treatment, if necessary.

[Measurement method] (1) Deep drawing workability (canning property) After a predetermined film was attached to tin-free steel heated to 231 ° 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 with a drawing ratio of 1.42 using a heat molding machine. However, at the time of molding, the laminated plate molding part is heated to 160 ° C. by the radiation heater RH, and
The molding punch is also heated to 120 ° C. The can thus obtained is subjected to a visual judgment and a rust prevention test. The rust-preventive property was determined by putting 1% NaCl water in a can, inserting the can as an anode, and inserting the cathode in NaCl, and by judging the current value when a voltage of 6 V was applied. There is no appearance abnormality and the current value is 0.
It was determined that 25 mA or less was "O", and other than that was "X".
A part of the appearance that was whitened was marked with "△". It was judged that ◯ to Δ were practically usable.

(2) Impact resistance A deep drawn can made under the conditions of (1) is filled with water and then sealed. Thirty canned products and 30 minutes each subjected to a drying treatment at 220 ° C. for 3 minutes and then subjected to a retort treatment at 125 ° C. for 3 hours were dropped on a floor inclined at 15 ° from a height of 1.0 m. After that, the rust preventive property is evaluated according to the following criteria under the condition described in (1). Total number 0.13 mA or less: ◎ Total number 0.25 mA or less: ○ Other than: ×

(3) Melting peak temperature, sub-peak temperature T
s Using a DSC (Differential Scanning Calorimeter) manufactured by Perkin Elmer, 10 mg of sample was melted and measured at a temperature rising rate of 10 ° C./min to determine the melting peak temperature. Further, the sub-peak temperature generated by the transformation of the quasicrystal generated during this measurement was defined as Ts. Both units are ° C.

(4) Carboxyl group concentration HIRANUMA COMMITTE-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 This is measured in an atmosphere of 25 ° C. using an Abbe refractometer, a monochromatic sodium D line 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) Orientation degree measuring device: FTS-15E / D (FT-IR manufactured by Bio Rad Digilab) Light source: Special ceramics detector: MCT auxiliary device: micro-ATR measuring auxiliary device (WILKS)
Incident angle: 45 ° IRE: KRS-5, using a polarizer Measurement conditions: Decomposition ability = 4 cm ⁻¹ Cumulative number of times = 500 times As orientation degree, (νC—O trans band) and absorption ratio of benzene ring (970 cm ⁻¹ / 790 cm ⁻¹ ) was obtained and used as the degree of orientation. Further, in the metal-film laminate,
The degree of film surface orientation on the non-steel plate side was measured in a laminated state, and the degree of orientation on the steel sheet side was evaluated by the same method after confirming the thickness on the steel sheet side in the thickness direction by scraping the film with a grindstone.

(7) Central average roughness Measured according to JIS-B0601.

(8) Intrinsic viscosity Measured in orthochlorophenol at 25 ° C.

(9) Difference between maximum and minimum in-plane refractive index (in-plane maximum-minimum refractive index) An Abbe refractometer was used, a monochromatic sodium D line was used as a light source, and a mount solution was used. As methylene iodide, the in-plane refractive index was measured in steps of 5 ° in an atmosphere of 25 ° C., the maximum and minimum values were calculated, and the difference between them was calculated.

(10) Adhesion to Laminate Melting peak temperature (if two or more peaks appear, arithmetical average of melting energy ratio) + 0.3 mm thick tin-free steel heated to 8 ° C. and then rapidly cooled to 210 ° C. After drying for 5 minutes, a 250g weight was dropped from a height of 6cm to give an impact, and then 6V under 1% NaCl water.
A voltage of 0.2 mA or less is applied as a good “◯”, and other than that is a bad “x”.

[0033]

【Example】

Examples 1 to 4, Comparative Examples 1 to 3 As main layer resin A, polyethylene terephthalate / isophthalate (PET / I) (88/12 mol%) 0.10 aggregated silica having an average particle size of 0.40 weight%
Was used. In Example 4, a composite film (laminated film) was used, and the resin B for the composite layer was polybutylene terephthalate / isophthalate (P
A copolymer composed of BT / I) (90/10 mol%) was used.

The above resins A and B are supplied to an extruder, and 270
It was melt extruded at ℃ and cast as a sheet. The unstretched sheet was sequentially stretched biaxially in the longitudinal and transverse directions under the conditions shown in Table 1 to obtain a film having a thickness of 25 μm.

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 relationship specified in the present invention were excellent in both can-making property and impact resistance (Examples 1 to 4), but at least one of them was out of the relationship of the present invention. Could not be satisfied.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

As described above, in the case of the metal laminating and forming film of the present invention, the melting peak temperature, the subpeak temperature range and the number of peaks, the plane orientation,
Since the film has an intrinsic viscosity, a surface roughness, and a maximum-minimum refractive index in the in-plane direction in a specific range, it is possible to improve impact resistance while ensuring excellent moldability such as deep drawing.

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Claims (5)

[Claims] 1. A polymer melting peak temperature of 210 to 257.
℃, its sub-peak temperature in the range of 100 ~ 240 ℃ 2
Main component is a copolyester having one peak temperature, plane orientation is 0.100 to 0.165, intrinsic viscosity is 0.45 to 1.5, and center line average roughness of at least one side is 0.01 to 0. A film for metal-bonding forming process, characterized in that the difference between the maximum value and the minimum value of the in-plane refractive index is 0.04 or less. 2. The center line average roughness R _{1A of} one side is 0.01.
˜0.15 μm, center line average roughness R _{2A of the other surface} is 0.01
The film for metal laminating and forming according to claim 1, which has a thickness of 0.50 μm. 3. The metal laminating and forming film according to claim 1, wherein a layer containing a polybutylene terephthalate resin is laminated on at least one surface of the metal laminating and forming film. 4. A layer made of two or more kinds of polymers having poor compatibility with each other is laminated on at least one surface of the metal laminating and forming film.
A film for metal laminating and forming according to any one of 1. 5. The metal laminating and forming film according to claim 1, which is heat-laminated with a steel plate, and the film surface orientation degree on the non-steel plate side of the film is 0.8 to 2. A metal-film laminate characterized by being drawn and / or ironed after being set to 0.