JPH06286091A - Metal laminating film - Google Patents

Abstract

PURPOSE:To obtain a film having excellent moldability of deep drawing, etc., impact resistance, perfume retentivity by laminating polyester resin films A, B, specifying a melting peak temperature, a surface orientation coefficient to special relationship, and setting a double refractive index of the layer A to a specific range. CONSTITUTION:This metal laminating film comprises biaxially oriented laminated film of polyester resins A, B, wherein melting peak temperatures TA, TB ( deg.C) of the resin A, B, have a relationship of TA>=tb+1, when surface orientation coefficients of the layers A, B are SA, SB, and a double refractive index of the layer A is nA, 0.20>=SA>SB>=0.02, 0>=nA<=8X10<-3> are satisfied, and the layer A is a protective layer and the layer B is an adhesive layer. In this case, when the TA does not fall within the range, a balance between the adhesive properties and impact resistance is deteriorated. When a value of the SB is smaller than 0.02, an impact resistance after laminating is deteriorated. At the time of SB=SA, the adhesive properties and the impact resistance do not compatible. When the SA is larger than 0.20, or when the index nA is excessively high, moldability is impaired.

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. More specifically, a polyester film for metal laminating that can be laminated to a metal plate and subjected to drawing, folding, etc., particularly a beverage can,
The present invention relates to a polyester film for metal bonding which 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 rust prevention 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-1-19).
2546), and (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-2-57339, etc.). (3) A method of laminating a low-oriented polyethylene terephthalate film on a metal plate and using it as a can-making material (Japanese Patent Laid-Open No. 64-22530, etc.) has 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 In view of the above-mentioned problems of the present invention, therefore, the present invention is particularly excellent in moldability, aroma retention, and impact resistance, and can be sufficiently put to practical use for metal bonding. The purpose is to provide a film.

[0005]

A metal laminating film of the present invention for this purpose is a biaxially stretched laminated film composed of resins A and B, and is a polyester-based resin of resins A and B, and Melting peak temperature T of resins A and B
_A (° C.) and T _B (° C.) have a relationship of T _A ≧ T _B +1 and the plane orientation coefficient of the A and B layers made of the resins A and B is S _A ,
When the birefringence of the S _B and A layers is n _A , 0.20 ≧ S _A > S _B ≧ 0.02 0 ≦ n _A ≦ 8 × 10 ⁻³ , and the resin A layer is a protective layer. , Resin B layer as an adhesive layer.

The resins A and B in the present invention are both made of a polyester resin, and the resin A is preferably made of a polyester copolymer. The copolymerized polyester is not particularly limited, but the following examples can be given as typical ones. As the acid component,
Aromatic dibasic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, dodecadioic acid, alicyclic dicarboxylic acids such as dimer acid, cyclohexanedicarboxylic acid Examples thereof include acids. Examples of the alcohol component include aliphatic diols such as ethylene glycol, diethylene glycol, butanediol, and hexanediol. These are used in combination of one or more. For example, as a preferred example, a polyester copolymer having 75 mol% or more of terephthalic acid as an acid component and 85 mol% or more of ethylene glycol as an alcohol component can be mentioned. The carboxyl group in the polyester is 50 eq / t or less, preferably 40
When it is eq / t or less, more preferably 30 eq / t or less, the impact resistance after retort is good, which is preferable. Particularly, the carboxyl group of the resin B is preferably 35 eq / t or less. Further, when the amount of diethylene glycol in the polyester is less than 1.5% by weight, preferably less than 0.85% by weight, it is preferable in terms of heat resistance after heat treatment.

In the present invention, the melting peak temperatures T _A and T _B of the resin A and the resin B must satisfy the relationship of T _A ≧ T _B +1 and preferably T _B + 1 ≦ T _A.
The relationship of ≦ T _B +8 is satisfied. This is because when T _A is not within the above range, the balance between the adhesiveness and the impact resistance becomes poor, which is not preferable. Here, the melting peak temperature of the resin is measured at a temperature rising rate of 10 ° C./min using DSC manufactured by Perkin Elmer. Further, the resin B may contain the resin A in an amount not exceeding 50% by weight, preferably 20% by weight.

In the present invention, the plane orientation coefficients S _A and S _B of the layers A and B composed of the resins A and B need to satisfy the relationship of 0.02 ≦ S _B <S _A ≦ 0.20. This is because the value of S _B is 0.0
Becomes smaller than 2, the bonding is not preferable since the impact resistance is deteriorated after molding, also S _B = For S _A, undesirably difficult both adhesion and impact resistance. On the other hand, S
_{When A} is larger than 0.20, moldability is impaired, which is not preferable. The plane orientation coefficient used here is an Abbe refractometer and the light source is monochromatic sodium D.
A line is used, and methylene iodide is used as a mount solution, and the measurement is performed in an atmosphere at 25 ° C.

In the present invention, the birefringence n _{A of the} A layer made of the resin A must be 8 × 10 ^-3 or less,
It is preferably 4.5 × 10 ⁻³ or less. This is because if the birefringence n _A is too high, the formability is impaired, which is not preferable. The birefringence is also measured using an Abbe refractometer like the above surface orientation coefficient.

Various lubricants may be added to the resins A and B 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,
Examples thereof include barium sulfate and zirconia. Examples of organic particles include silicone particles, crosslinked styrene particles, imide particles, and amide particles. The average particle size (by the sedimentation method) is 2.0 μm.
The following can be more preferably 1.2 μm or less, and most preferably 0.8 μm or less.

In the present invention, it is preferable that the center line average roughnesses R _A and R _B of the A layer and the B layer satisfy the relationship of R _A <R _B because the workability is more excellent. Further, when R _A is 0.05 or less, it is more preferable. There are various methods for achieving this relationship, and the method is not particularly limited. For example, the following method is preferable from the viewpoint of moldability.

<Method> Layer A: Substantially no particles. Layer B: Aggregated silica is added in the range of 0.03 to 1.0% by weight. Layer A: Only particles selected from one or more types of alumina selected from δ, γ, and θ types, zirconia, and silica in which spherical silica is connected in a beaded shape are added. Layer B: Aggregated silica is added in the range of 0.03 to 1.0% by weight. With the formulation of :, aggregated silica is added to the layer A in a range not reaching 0.03% by weight.

The method for producing the polyester resin of 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 from the viewpoint 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. As a typical example of the A / B layer thickness ratio, 1/50 to 50/1 can be mentioned.

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 production method of the present invention will be explained.
It is not limited to this. Resins A and B having a predetermined viscosity (usually an intrinsic viscosity of 0.45 to 1.50) are appropriately lubricated and then dried to 400 ppm or less, preferably 80 ppm or less. The dry raw materials A and B are each melt-mixed using two extruders. When an extruder having degassed holes is used, drying may be omitted, or various additives may be added during the extruder. After laminating the resins A and B in a molten state, they are 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 at 60 to 140 ° C. The film is stretched in the transverse direction by 2.0 to 6.0 times in the range and heat-treated in the range of 120 to 240 ° C. while relaxing as necessary. The resins A and B may be laminated as described above, or the laminated laminated film layer may be formed in a molten state on the longitudinal uniaxially stretched film and then stretched in the transverse direction. Moreover, you may perform biaxial stretching simultaneously after lamination.

To obtain the film of the present invention, resin A,
It is preferable that at least one roll that comes into contact with B immediately before stretching has a temperature difference. Specifically, the surface temperature of the roll in contact with the resin B is preferably higher than the surface temperature of the roll in contact with the resin A within a temperature difference range of 1 to 5 ° C. Radiation heaters, hot air, etc. may be utilized as necessary in making the temperature difference.

[Measurement Method] (1) Carboxyl Group Using HIRANUMA COMTITE-7 REPORTING TITRETOR, a silver chloride composite electrode is filled with a supersaturated potassium chloride aqueous solution, and the calculation is performed 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)

(2) 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.

(3) Impact resistance A deep drawn can made under the conditions of (1) is filled with water and then sealed. After aging the canned goods and 50 pieces subjected to retort treatment at 120 ° C for 8 hours, drop them on the floor inclined at 15 ° from a height of 1.2 m, and then evaluate the rust-preventive property under the conditions described in (1). To do. 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 ◎, ○, and △ were determined to be practical.

(4) Taste-maintaining aroma Orange drinks and coffees were enclosed, left for 1 week, and their aromas were evaluated. What feels equivalent to the coffee before inclusion: ◯ Feels a little inferior in aroma: △ Significantly inferior: Poor, and it was judged that ○ and △ could be put to practical use.

[0022]

【Example】

Examples 1 to 8 and Comparative Examples 1 to 3 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) consisting essentially of particle-free polyester (IV =
0.72) and a resin B in which the acid component is terephthalic acid and isophthalic acid, the alcohol component is ethylene glycol and diethylene glycol, and 0.12% by weight of aggregated silica having an average particle size of 1.8 μm is added. (IV = 0.67) was used. However, in Example 5, 0.3% by weight of staring silica having an average particle size of 1.8 μm was added to the resin A, and the addition amount of the above aggregated silica in the resin B was changed to 0.20% by weight.

The above resins A and B were supplied to different extruders, melt-extruded at 280 ° C., laminated by a two-layer die, and cast as a laminated sheet. This unstretched sheet was longitudinally stretched at a stretching temperature of 102 ° C. and a stretching ratio of 3.0 times. However, the temperatures of the two rolls in contact with the surface on the resin B side immediately before longitudinal stretching were 105 ° C and 106 ° C. The obtained uniaxially stretched film is introduced into a tenter and stretched at a temperature of 110 ° C.
The film was transversely stretched at a stretching ratio of 3.1 times. The biaxially stretched film was once cooled, and then heat-fixed while being subjected to a relaxation treatment at 190 ° C., a transverse relaxation rate of 3% and a longitudinal relaxation rate of 1.2%. However, in Comparative Example 2, the longitudinal stretching temperature was 98.
C, the longitudinal stretching ratio was 3.2 times, the transverse stretching temperature was 108 ° C., and the transverse stretching ratio was 3.5 times. In Example 4, the longitudinal stretching temperature was 98 ° C, the longitudinal stretching ratio was 3.4 times, the transverse stretching temperature was 107 ° C,
The transverse stretching ratio was 3.5 times.

The characteristics of the obtained film are shown in Table 1. As shown in Table 1, those having T _A , T _B , S _A , S _B , and n _A satisfying the relationships specified in the present invention were excellent in deep drawing workability, impact resistance, and aroma retention. In any of (Examples 1 to 8) out of the relationship of the present invention, deep drawability and impact resistance could not be particularly satisfied (Comparative Examples 1 to 3).

[0025]

[Table 1]

[0026]

As described above, in the case of the metal laminating film of the present invention, the polyester resins A and B are laminated, and the melting peak temperatures T _A , T _B , the plane orientation coefficients S _A , S. _{Since B} has a specific relationship and the birefringence n _A of the A layer is within a specific range, formability such as deep drawing,
It is possible to obtain a film excellent in impact resistance and aroma retention.

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

Claims (6)

[Claims] 1. A biaxially stretched laminated film composed of resins A and B, wherein both resins A and B are polyester resins.
And the melting peak temperatures T _A (° C.) and T of the resins A and B,
_B (° C.) has a relationship of T _A ≧ T _B +1 and the resin A, B
When the plane orientation coefficients of the A and B layers are S _A and S _B , and the birefringence of the A layer is n _A , then 0.20 ≧ S _A > S _B ≧ 0.02 0 ≦ n _A ≦ 8 × A film for metal bonding which satisfies 10 ^{-3 and} has a resin A layer as a protective layer and a resin B layer as an adhesive layer. 2. The film for metal bonding according to claim 1, wherein the resin A is a polyester copolymer comprising 75 mol% or more of terephthalic acid as an acid component and 85 mol% or more of ethylene glycol as an alcohol component. 3. The center line average roughness R _{A of} the layers A and B,
R _B is R _A <claim 1 or 2 metal bonding for film satisfies R _B. 4. The melting peak temperature T of the resins A and B
The metal laminating film according to claim 1, wherein _A (° C.) and T _B (° C.) satisfy T _B + 1 + ≦ T _A ≦ T _B +8. 5. The resin A and B has a carboxyl group of 50 eq.
It is below / t, The film for metal bonding in any one of Claim 1 thru | or 4 characterized by the above-mentioned. 6. The resin B has a carboxyl group of 35 eq / t.
The film for metal bonding according to any one of claims 1 to 4, wherein: