JP3094749B2 - Film for bonding metal - Google Patents

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 bonding. More specifically, a polyester film for metal bonding, which can be subjected to drawing, folding, etc. by bonding to a metal plate, particularly a beverage can,
The present invention relates to a polyester film for bonding metal, 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, metals are 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 in which a biaxially oriented polyethylene terephthalate film is laminated via a low-melting polyester adhesive layer and used as a can-making material (Japanese Patent Application Laid-Open No. Sho 56-10451, Tokuho 1-19)
(2546) and (2) a method in which an amorphous or low-crystalline aromatic polyester film is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 1-192545, Japanese Patent Laid-Open No. 2-57339). (3) A method of laminating a low-orientation polyethylene terephthalate film on a metal plate and using it as a can-making material (JP-A-64-22530) has been proposed.

However, the method (1) is advantageous in terms of moldability, the method (2) is advantageous in terms of fragrance retention and embrittlement with time, and the method (3) is effective in the method (1). Similarly, it is inadequate in terms of moldability and is not practically used.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and in particular, has excellent moldability, fragrance retention, and impact resistance, and can be used sufficiently for metal bonding. The purpose is to provide a film.

[0005]

According to the present invention, there is provided a film for bonding metal according to the present invention, which is a biaxially stretched laminated film comprising resins A and B, wherein resins A and B are both polyester-based resins, 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 coefficients of the A and B layers composed of resins A and B are represented by S _A ,
S _B , the birefringence index of layer _A is n _A , the average of the center lines of layer A and layer B
When the roughness is R _A and R _B , respectively , 0.20 ≧ S _A > S _B ≧ 0.020 0 ≦ n _A ≦ 8 × 10 ⁻³ R _A <R _B is satisfied, and the resin A layer is It is composed of a protective layer and a resin B layer as an adhesive layer.

The resins A and B in the present invention are both made of a polyester resin, and among them, the resin A is preferably made of a polyester copolymer. The copolymerized polyester is not particularly limited, but typical examples include the following. As the acid component,
Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, dodecadionic acid, dimer acid, and cyclohexanedicarboxylic acid Acids and the like can be exemplified. Examples of the alcohol component include aliphatic diols such as ethylene glycol, diethylene glycol, butanediol, and hexanediol. One or more of these may be used in combination. For example, as a preferred example, a polyester copolymer composed of 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 exemplified. The carboxyl group in the polyester is 50 eq / t or less, preferably 40 eq / t or less.
When it is eq / t or less, more preferably 30 eq / t or less, the impact resistance after retorting is good, which is preferable. In particular, the carboxyl group of the resin B is preferably 35 eq / t or less. 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 suitable in terms of heat resistance after the heat treatment.

In the present invention, the melting peak temperatures T _A and T _B of the resin A and the resin B need to satisfy a relationship of T _A ≧ T _B +1, and preferably, T _B + 1 ≦ T _A.
<T _B +8 is satisfied. This is because if T _A is not in the above range, the balance between adhesion and impact resistance is deteriorated, which is not preferable. Here, the melting peak temperature of the resin was measured at a heating rate of 10 ° C./min using a DSC manufactured by Perkin Elmer. In addition, two or more
If a melting peak occurs, the melting energy
The weighted average is used as the melting peak. The resin B may contain the resin A in an amount not exceeding 50% by weight, preferably not exceeding 20% by weight.

In the present invention, the plane orientation coefficients S _A and S _B of the layers A and B made of the resins A and B need to be in a relationship of 0.02 ≦ S _B <S _A ≦ 0.20. This is the value of S _B 0.0
If it is smaller than 2, the impact resistance after lamination and molding is deteriorated, which is not preferable. If S _B = S _A , it is not preferable because adhesion and impact resistance are hardly compatible. On the other hand, S
_{If A} is greater than 0.20, moldability is impaired, which is not preferred. The term "plane orientation coefficient" used herein means Abbe's refractometer, and monochromatic sodium D
The measurement was carried out in a 25 ° C. atmosphere using methylene iodide as a mounting solution using a line.

In the present invention, the birefringence n _{A of the} layer A composed of the resin A must be 8 × 10 ⁻³ or less;
Preferably it is 4.5 × 10 ⁻³ or less. This is because if the birefringence n _A is too high, the moldability is impaired, which is not preferable. The birefringence is also measured using an Abbe refractometer as in the case of the above-mentioned plane 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. Examples of suitable inorganic particles include aggregated silica, spherical silica, alumina, titanium dioxide, calcium carbonate,
Barium sulfate and zirconia can be mentioned. Examples of the 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 mentioned, more preferably 1.2 μm or less, and most preferably 0.8 μm or less.

[0011] In the present invention, A layer, the center line average roughness R _A of the layer B, is R _B, which satisfies R _A <R _B the relationship this
Thereby, excellent workability can be obtained. In addition, R _A is 0.
The case of 05 or less 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 particle-free. Layer B: Agglomerated silica is added in the range of 0.03 to 1.0% by weight. A layer: Only particles selected from alumina, zirconia, and spherical silica in a bead shape selected from δ, γ, and θ types are added. Layer B: Agglomerated silica is added in the range of 0.03 to 1.0% by weight. In the formula (1), the aggregated silica is added to the layer A in a range not to reach 0.03% by weight.

The method for producing the polyester resin of the present invention is not particularly limited. However, when the metal-laminated product is used as a container, a resin synthesized by a direct weight method is more preferable in terms of taste and flavor retention. . When the amount of aldehydes is reduced by a method such as solid phase polymerization, it is more preferable from the viewpoint of taste and flavor retention. Examples of the polymerization catalyst include antimony and germanium, and germanium is preferred from the viewpoint of taste and aroma retention. If necessary, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, a coloring agent, a pigment, a whitening agent and the like may be added.

The thickness of the polyester film of the present invention is suitably in the range of 2 to 150 μm. It is preferably from 8 to 60 μm, more preferably from 12 to 40 μm. As the thickness ratio of the A and B layers, 1/50 to 50/1 can be mentioned as a typical example.

As a metal plate to which the film of the present invention is bonded, tin, tin-free steel, aluminum and the like can be mentioned as typical examples. These metal plates may be appropriately subjected to an organic or inorganic treatment on the surface.

Next, a typical production method of the present invention will be described.
It is not limited to this. After appropriately applying a lubricant formulation to resins A and B having a predetermined viscosity (usually 0.45 to 1.50 in intrinsic viscosity), the resin is 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 using an extruder having deaerated pores, drying may be omitted, or various additives may be added in the middle of the extruder. After laminating the resins A and B in a molten state, they are once cooled on a cooling roll, and then stretched 2.0 to 6.0 times in the longitudinal direction in the range of 60 to 135 ° C. The film is stretched 2.0 to 6.0 times in the transverse direction within the range, and heat-treated while relaxing as needed in the range of 120 to 240 ° C. The lamination of the resins A and B may be performed as described above, or after forming a laminated laminated film layer in a molten state on a vertically uniaxially stretched film, the film may be horizontally stretched. After the lamination, simultaneous biaxial stretching may be performed.

In order to obtain the film of the present invention, resin A,
Preferably, at least one roll is brought into contact with B immediately before stretching, and a temperature difference is provided between each roll. Specifically, it is preferable that the surface temperature of the roll in contact with the resin B is higher than the surface temperature of the roll in contact with the resin A within a temperature difference of 1 to 5 ° C. In making the temperature difference, a radiation heater, hot air or the like may be used as necessary.

[Measurement Method] (1) Using a carboxyl group HIRANUMA COMTITE-7 REPORTING TITRETOR, a supersaturated potassium chloride aqueous solution is filled using a silver chloride composite electrode, and the calculation is performed based on the following equation. COOH (eq / t) = [(AB) × C × F] / SA A: NaOH titer for sample (normality = N / 50-NaOH / methanol) B: NaOH titer for 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 After a predetermined film is bonded to tin free steel heated to 265 ° C., the film is cooled with a cooling roll from the film side and then water-cooled. The thus-obtained film-bonded metal plate is cut into a 250 mm-diameter disk, and then formed into a drawing ratio of 1.3 using a heat forming machine with the film surface as the inner surface. The thus obtained can is subjected to a visual judgment and a rust prevention test. 1% rust prevention
An aqueous solution of NaCl was placed in a can, the can was inserted into the anode, the cathode was inserted into NaCl, and the current was determined when a voltage of 6 V was applied. “O” was determined when the current value was 0.25 mA or less without any abnormal appearance, and “X” was determined otherwise.

(3) Impact resistance A deep drawn can made under the conditions of (1) is filled with water and sealed. After dropping 50 pieces of canned products and those subjected to a retort treatment at 120 ° C. for 8 hours on a floor inclined at 15 ° from a height of 1.2 m, the rust prevention was evaluated under the conditions described in (1). I do. Total number 0.10 mA or less: 全 Total number 0.25 mA or less: Eight or more 0.25 mA or less: そ れ Other: ×, it was determined that ◎, △, and Δ could be put to practical use.

(4) Taste perfume preservation Orange drink and coffee were sealed and left for one week, and the flavor was evaluated. What felt equivalent to the coffee before enclosing: ○ Somewhat felt inferior in incense: △ Significantly inferior: ×, and determined that ○ and △ could be used for practical use.

[0022]

【Example】

Examples 1 to 8 and Comparative Examples 1 to 3 As resin A, the acid component was composed of terephthalic acid (TPA) and isophthalic acid (IPA), and the alcohol components were ethylene glycol (EG) and diethylene glycol (DE).
G), a substantially particle-free polyester (IV =
0.72), and as the resin B, a polyester similarly containing an acid component of terephthalic acid, isophthalic acid, an alcohol component of ethylene glycol and diethylene glycol, and adding 0.12% by weight of aggregated silica having an average particle size of 1.8 μm. (IV = 0.67) was used. However, in Example 5, 0.3% by weight of gaze silica having an average particle size of 1.8 μm was added to Resin A, and the amount of the aggregated silica in Resin B was changed to 0.20% by weight.

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

Table 1 shows the properties of the obtained film. As shown in Table 1, those in which T _A , T _B , S _A , S _B , and n _A satisfy the relationship specified in the present invention were excellent in both deep drawing workability, impact resistance, and fragrance retention. (Examples 1 to 8), ones out of the relationship of the present invention, could not particularly satisfy the deep drawability and the impact resistance (Comparative Examples 1 to 3).

[0025]

[Table 1]

[0026]

As described above, when the film for metal bonding according to the present invention is used, the laminated structure of the polyester resins A and B, the melting peak temperatures T _A and T _B , the plane orientation coefficients S _A and S _B is a specific relationship, the birefringence n _A of the A layer is a specific range , and the magnitude relationship between R _A and R _B is
Since it has been specified, it is possible to obtain a film having excellent moldability such as deep drawing, impact resistance, and fragrance retention.

Continuation of the front page (72) Inventor Kunio Shibatsuji 1-1-1 Sonoyama, Otsu City, Shiga Prefecture Toray Industries, Inc. Shiga Works (56) References JP-A-6-320669 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (5)

(57) [Claims] 1. A biaxially stretched laminated film comprising resins A and B, wherein the resins A and B are both polyester-based resins,
And melting peak temperatures T _A (° C.) and T of the resins A and B.
_B (° C.) such that T _A ≧ T _B +1.
The plane orientation coefficients of the A and B layers are S _A and S _B , the birefringence of the A layer is n _A , and the center line average roughness of the A and B layers is, respectively.
When R _A and R _B are satisfied, 0.20 ≧ S _A > S _B ≧ 0.020 0 ≦ n _A ≦ 8 × 10 ⁻³ R _A <R _B is satisfied, and the resin A layer is formed of a protective layer and a resin. A film for metal bonding, wherein the layer B serves as an adhesive layer. 2. The film for metal bonding according to claim 1, wherein said resin A is a polyester copolymer comprising terephthalic acid as an acid component at 75 mol% or more and an alcohol component at at least 85 mol% ethylene glycol. 3. The melting peak temperature T of the resins A and B.
_{A (℃), T B (} ℃) is _{T B + 1 ≦ T A ≦} T B +8 claim 1 or 2 metal bonding for film satisfying. 4. The resin A, B having a carboxyl group of 50 eq.
The film for bonding metal according to any one of claims 1 to 3 , wherein the ratio is not more than / t . 5. A resin B having a carboxyl group of 35 eq / t.
The film for bonding metal according to any one of claims 1 to 3 , wherein: