JPH06286055A - Laminate - Google Patents

Abstract

PURPOSE:To obtain a laminate of metal and film which has excellent molding processability and impact resistance and sufficient practical use by thermally a polyester biaxially oriented film in which orientation degrees in all directions are specified on a base material of a metal plate. CONSTITUTION:A laminate comprises a polyester biaxially oriented film thermally adhered to a metal plate base material, wherein formulae are satisfied, where lateral orientation degrees of the film perpendicular to a film flowing direction at a thermal adherence side are AMD, ATD, lateral orientation degrees of the film to the film flowing direction at a center in a film thickness direction are CMD, CTD and lateral orientation degrees of the film in the film flowing direction at a non-thermal adherence side are BMD, BTD, and a difference of orientation degrees between lateral directions to the film flowing direction at all positions of the film is 0.5 or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate in which a polyester film is attached to a metal. More specifically, the present invention relates to a laminate that can be drawn and folded by laminating a polyester film on a metal plate, and more particularly to a laminate that can be used for can bodies such as beverage cans and food cans, can lids, and can bottoms.

[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 touch 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, regarding the method (1), in terms of forming workability, particularly deep drawing workability in can making,
The method (2) is insufficient in impact resistance of the laminated films, and the method (3) is insufficient in impact resistance as in the method (2), and is not put to practical use. Is the reality.

[0004]

In view of the above-mentioned problems of the present invention, therefore, the present invention is a laminate in which a metal and a film are adhered, which is particularly excellent in molding processability and impact resistance and can be sufficiently put to practical use. The purpose is to provide.

[0005]

The laminate of the present invention for this purpose is a laminate in which a polyester-based biaxially stretched film is heat-bonded to a base material made of a metal plate. , A _MD , A _TD , the film flow direction on the heat-bonding side and the lateral orientation degree orthogonal to the film flow direction, and C _MD , C _{TD the} film flow direction and the lateral orientation degree in the central portion of the film thickness direction. , Where B _MD and B _TD are the degree of orientation in the film flow direction and the transverse direction on the non-heat-bonded side, 0.2 ≦ A _MD × 2 ≦ B _MD ≦ 3.0 0.2 ≦ A _TD × 2 ≦ B _TD ≤ 3.0 0.35 x (A _MD + B _MD ) ≤ C _MD ≤ (A _MD + B _MD ) x
0.65 0.35 × (A _TD + B _TD ) ≦ C _TD ≦ (A _TD + B _TD ) ×
In addition to satisfying the requirement of 0.65, the difference in orientation degree between the film flow direction and the lateral direction is 0.5 or less in all parts of the film.

The polyester biaxially stretched film in the present invention is made of a polyester resin, and particularly preferably made of a polyester copolymer. The copolymerized polyester is not particularly limited, but the following examples can be given as typical ones. Examples of the acid component include aromatic dibasic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid and dodecadioic acid. Also, as the alcohol component,
Aliphatic diols such as ethylene glycol, diethylene glycol, butanediol, hexanediol can be mentioned. These are used in combination of one or more. For example, as a preferable example, a polyester copolymer having 65 mol% or more of terephthalic acid as a polyester acid component and 85 mol% or more of ethylene glycol as an alcohol component can be mentioned. The amount of acetaldehyde in the polyester is preferably 0.3% by weight or less, more preferably 30 ppm or less. Also, the amount of diethylene glycol in the polyester is 1.5% by weight.
If it is less than 0.85% by weight, preferably 0.65% by weight or less, the impact resistance is good, which is preferable. Furthermore, when the carboxyl group in the polyester is less than 50 eq / t, preferably 40 eq / t or less, more preferably 30 eq / t or less, the impact resistance after retort is good, which is preferable.

In the laminated body of the present invention, a polyester biaxially stretched film made of the polyester resin as described above is thermally adhered to a base material made of a metal plate such as a steel plate. The polyester flume is biaxially oriented by biaxial stretching, but in the present invention, the degree of orientation satisfies a specific relationship with respect to the heat-bonded side, non-heat-bonded side of the film, and the central portion in the film thickness direction. To be controlled. As a result, the target satisfactory values can be obtained with respect to both the formability, particularly the deep drawability, and the impact resistance of the laminated body to which the films are attached.

That is, the film flow direction of the polyester-based biaxially stretched film on the heat-bonding side with the substrate and the degree of orientation in the transverse direction orthogonal to the film flow direction are A _MD , A
_TD , the degree of orientation in the film flow direction and the lateral direction at the central portion in the film thickness direction is C _MD , C _TD , and the degree of orientation in the film flow direction and the lateral direction on the non-heat-bonded side is B _MD , B _TD . 2 ≤ A _MD x 2 ≤ B _MD ≤ 3.0 0.2 ≤ A _TD x 2 ≤ B _TD ≤ 3.0 0.35 x (A _MD + B _MD ) ≤ C _MD ≤ (A _MD + B _MD ) x
0.65 0.35 × (A _TD + B _TD ) ≦ C _TD ≦ (A _TD + B _TD ) ×
In addition to satisfying 0.65, the difference in orientation degree between the film flow direction and the lateral direction is controlled to be 0.5 or less in all parts of the film.

That is, in the laminate of the present invention, the heat-bonding side of the polyester-based biaxially stretched film has a lower degree of orientation to improve the adhesiveness to the substrate to improve the deep drawing workability, The non-heat-bonding side has a higher degree of orientation to improve the impact resistance of the film, and the central portion in the thickness direction has an intermediate degree of orientation so that the degree of orientation changes smoothly in the film thickness direction.

Various lubricants may be added to the polyester biaxially stretched film of the present invention. The type of lubricant may be inorganic or organic. Suitable inorganic particles include agglomerated silica, spherical silica, alumina, titanium dioxide, calcium carbonate, barium sulfate, and zirconia. Examples of organic particles include silicone particles, crosslinked styrene particles, imide particles, and amide particles.

The method for producing the polyester resin in the present invention is not particularly limited, but when the present metal-bonded product is used as a container, a resin synthesized by the direct weight method is more preferable in terms of taste-maintaining aroma. . Further, when the aldehydes are reduced by a method such as solid phase polymerization, it is more preferable in terms of taste-maintaining aroma. Examples of the polymerization catalyst include antimony and germanium, and germanium is preferable from the viewpoint of taste-maintaining aroma. If desired, other additives such as antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, colorants, pigments, whitening agents and the like may be added.

The thickness of the polyester film of the present invention is preferably in the range of 2 to 150 μm. The thickness is preferably 8 to 60 μm, 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, aminium, and the like. The surface of these metal plates may be subjected to organic or inorganic treatment as appropriate.

Next, a typical method for producing the laminate of the present invention will be described, but the invention is not limited thereto. 400 p after applying a lubricant formulation to a polyester resin having a predetermined viscosity (usually an intrinsic viscosity of 0.45 to 1.50)
Dry to pm or less, preferably 80 ppm or less. The dry raw materials 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. After discharging the resin in a molten state from the die, it is once cooled on a cooling roll, and then stretched in the longitudinal direction in the range of 60 to 135 ° C. by 2.0 to 6.0 times, and then in the range of 60 to 140 ° C. 2.0 to 6.0
The film is stretched in the transverse direction twice and heat-treated while relaxing in the range of 120 to 240 ° C as needed.

The polyester biaxially stretched film obtained as described above is laminated to a metal plate as a base material, for example, a tin-free steel plate. The bonding conditions are, for example, heating a metal plate at 200 to 300 ° C.,
50-150 with the heating roll on the bonding surface of the film
Heat to 0 ° C. and laminate to the heated metal plate. Then, the non-heat-bonded surface of the film is removed by 15 to 50
It is cooled with a cooling roll at ℃ to increase the degree of orientation on the non-heat-bonded side. By such a manufacturing method, as described above, a laminated body obtained by laminating films whose orientation degree changes in the film thickness direction is obtained.

[Measurement Method] (1) Deep Drawing Workability A predetermined film is attached to tin-free steel heated to 265 ° C., then cooled from the film side with a cooling roll and then water-cooled. The film-bonded metal plate thus obtained is cut into a disk shape having a diameter of 250 mm, and then the film surface is formed into an inner surface using a heat molding machine to form a drawing ratio of 1.3. The can thus obtained is subjected to a visual judgment and a rust prevention test. Rust resistance is 1%
NaCl water was placed in a can, the can was used as an anode, and the cathode was inserted in NaCl. The current value was applied when a voltage of 6 V was applied. 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.

(2) Impact resistance-A 50 deep-drawn cans made under the conditions of (1) are filled with water and then sealed. The canned product and the product subjected to retort treatment at 120 ° C. for 8 hours were dropped on a floor inclined at 15 ° from a height of 1.2 m, and then the rust preventive property was evaluated under the condition described in (1). Total number 0.10 mA or less: ◎ Total number 0.25 mA or less: ○ 8 or more and 0.25 mA or less: △ Other than that: ×, and it was determined that ◎, ○, and △ could be put to practical use.

(3) Impact resistance-B A deep drawn can made under the conditions of (1) is filled with water and then sealed. The canned product and the one that was heat-treated at 220 ° C. for 10 minutes were dropped on a floor inclined at 15 ° from a height of 1.2 m, and then evaluated according to the same criteria as described in (2).

(4) Orientation degree measuring device: FTS-15E / D (FT-IR manufactured by Bio Rad Digilab) Light source: Special ceramics detector: MCT auxiliary device: auxiliary device for micro-ATR measurement (WILKS)
Incident angle: 45 ° IRE: KRS-5, using polarizer Measurement conditions: Decomposition ability = 4 cm ⁻¹ Cumulative number of times = 500 times As the degree of orientation, the absorption ratio of (νC—O trans band) and benzene ring (970 cm ⁻¹ / 790 cm ⁻¹ ) was obtained and used as the degree of orientation. In addition, the degree of orientation of the central portion is shaving the film with a grindstone, and after confirming that it is the central portion in the thickness direction,
It evaluated by the same method.

(5) Carboxyl group Using HIRANUMA COMTITE-7 REPORTING TITRETOR, a silver chloride composite electrode is used, and a supersaturated potassium chloride aqueous solution is filled, and the calculation is carried out based on the following formula. COOH (eq / t) = [(A−B) × C × F] / S A: NaOH titer of sample (ml) (normality = N / 50−NaOH / methanol) B: NaOH titer of blank ( ml) C: 20 (20 = N / 50 × 1/1000 × 1)
0 ° F: Factor (determined by benzoic acid / methanol solution) S: Sampling amount (g)

[0021]

【Example】

Examples 1 to 6 and Comparative Examples 1 to 4 As a polyester resin, the acid component is terephthalic acid (T
PA) and isophthalic acid (IPA) (Example 4 is terephthalic acid and sebacic acid (SA)), and the alcohol component is ethylene glycol (EG) and diethylene glycol (DEG). Polyester (IV = 0.73) was used.

The above resin was supplied to an extruder, melt-extruded at 285 ° C., discharged in a sheet form from a die, and cast onto a cooling drum. This unstretched sheet is stretched at a stretching temperature of 10
Longitudinal stretching was performed at 8 ° C. and a stretching ratio of 3.0 times. The obtained uniaxially stretched film is introduced into a tenter, and the stretching temperature is 104 ° C.
The film was transversely stretched at a stretch ratio of 2.9 times. The biaxially stretched film was once cooled and then heat-set while being subjected to a relaxation treatment at 185 ° C. and a relaxation rate of 4%. However, in Comparative Example 4, the unstretched film formed by casting on a cooling drum at 40 ° C. was used.

The obtained film was heat-bonded on tin-free steel as a substrate as follows to obtain a laminate. First, tin-free steel was heated to 265 ° C., and the laminated surface of the film was heated with a heating roll at a temperature of x ° C. as shown in Table 1 and then laminated. After that,
As shown in Table 1, the film was cooled from the non-heat-bonded surface side of the film with a cooling roll at y ° C.

With respect to the obtained laminate, the degree of orientation of the film was measured, and the deep drawing workability and impact resistance were evaluated. The results shown in Table 2 were obtained. As shown in Table 2, when each orientation degree of the film was within the range specified in the present invention, good results were obtained in both deep drawability and impact resistance, but each orientation degree was When the value is out of the range specified in the invention, both properties could not be satisfied.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

As described above, in the case of the laminated body of the present invention, the orientation degree of the polyester-based biaxially stretched film to be bonded to the base material can be adjusted to the heat-bonding side, the non-heat-bonding side, or an intermediate portion thereof. Since the above conditions are controlled so as to satisfy specific relationships, it is possible to obtain a laminate which is excellent in moldability such as deep drawing and has excellent impact resistance and which is optimal for can manufacturing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Shibatsuji 1-1-1, Sonoyama, Otsu City, Shiga Toray Co., Ltd. Shiga Plant

Claims (5)

[Claims] 1. A laminate in which a polyester-based biaxially stretched film is heat-bonded on a base material made of a metal plate, and a film flow direction and a film flow direction of the polyester-based biaxially-stretched film on the heat-bonding side. The orthogonal orientation in the transverse direction is A _MD , A _TD , the orientation in the film flow direction and the transverse direction at the central portion in the film thickness direction is C _MD ,
C _TD , where the degree of orientation in the film flow direction and the transverse direction on the non-heat-bonded side is B _MD and B _TD , 0.2 ≦ A _MD × 2 ≦ B _MD ≦ 3.0 0.2 ≦ A _TD × 2 ≤ B _TD ≤ 3.0 0.35 x (A _MD + B _MD ) ≤ C _MD ≤ (A _MD + B _MD ) x
0.65 0.35 × (A _TD + B _TD ) ≦ C _TD ≦ (A _TD + B _TD ) ×
A laminated body which satisfies 0.65 and has a difference in orientation degree between the film flow direction and the lateral direction of all the film portions of 0.5 or less. 2. The laminate according to claim 1, wherein the polyester biaxially stretched film comprises terephthalic acid in an amount of 65 mol% or more of the polyester acid component. 3. The laminate according to claim 1, wherein the amount of acetaldehyde in the polyester of the polyester biaxially stretched film is 0.3% by weight or less. 4. The laminate according to claim 1, wherein the amount of diethylene glycol in the polyester of the polyester biaxially stretched film is less than 1.5% by weight. 5. The laminate according to claim 1, wherein the polyester of the polyester-based biaxially stretched film has a carboxyl group of less than 50 (eq / t).