JPH07117120A - Metal sticking film - Google Patents

Abstract

PURPOSE:To obtain excellent moldability, aroma-preservative property, and impact resistance by setting specified values for a fusion peak temperature face orientation coefficient, an average refraction factor, and a double refraction factor of a biaxially oriented film of a polyester resin A. CONSTITUTION:A metal sticking film is made of a biaxially oriented film consisting of a polyester resin A, where a fusion peak temperature of the film TA, a face orientation coefficient SA, an average refraction factor n, and a double refraction factor DELTAnA are made to be 200 deg.C<=TA<=240 deg.C 0.12<=SA<=0.14 1.585<=nA<=1.620 and DELTAnA<=12X10<-3>. It 15 desirable that the resin A is made of a polyester copolymer. For acid component, an aromatic dibasic acid, an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid or the like are suitable. For alcohol component, an aliphatic diol is suitable. The thickness of the polyester film is made to be 2-150mum. For metal plate, a tin plate, a tin-free steel, an aluminum and the like are exemplary.

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 applied to a metal plate and subjected to drawing, folding, etc., particularly metal laminating that can be used for can bodies such as beverage cans, food cans, can bottoms, can lids. The present invention relates to a polyester film for laminating.

[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 molding processability, 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 comprises a biaxially stretched film made of a polyester resin A, and has a melting peak temperature T _A and a plane orientation coefficient S _{A of the} film. , Average refractive index n _A , birefringence Δn _A are 200 ° C. ≦ T _A ≦ 240 ° C., 0.12 ≦ S _A ≦ 0.14, 1.585 ≦ n _A ≦ 1.620, Δn _A ≦ 12 × It is characterized by satisfying 10 ^-3 .

The metal laminating film according to the present invention may be composed of a laminated film. That is, it is composed of a biaxially stretched laminated film composed of a polyester resin A and a polyester resin B, the melting peak temperature T _B and the plane orientation coefficient S of a film layer composed of the resin B.
_B , the birefringence Δn _B is T _B ≧ T _A +1 (T _A : melting peak temperature of the film layer made of the resin A), 0.09 ≦ S _B ≦ 0.118, Δn _B ≦ 12 × 10 ⁻³ A film for laminating metal, which satisfies the following conditions.

Both of the resins A and B in the present invention are made of polyester resin, and the resin A is preferably made of polyester copolymer. The copolymerized polyester is not particularly limited, but the following examples can be given as typical ones. Examples of acid components include aromatic dibasic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid and dodecadioic acid, dimer acid and cyclohexanedicarboxylic acid. Examples thereof include alicyclic dicarboxylic acid. 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.

As for the polymer intrinsic viscosity, both resins A and B are
0.64 or more, preferably 0.68 or more is suitable.
In particular, the case where the intrinsic viscosity of the resin A is 0.70 or more is more preferable. As the particles to be added, inorganic particles, organic particles, agglomerated particles, true spherical particles and various deformed particles can be used. Among them, the case where the resin B is substantially particle-free is more preferable from the viewpoint of impact resistance.

In the present invention, when the resin A is a single layer film, its melting peak temperature T _A is 200 ° C.
When ≦ T _A ≦ 240 ° C. is satisfied and the film is a laminated film of resin A and resin B, its melting peak temperature T _A , T
_B needs to satisfy the relationship of T _B ≧ T _A +1. This is because when T _A and T _B are not within the above range, the balance between adhesiveness and impact resistance becomes unfavorable, 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 B 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 A and B layers made of the resins A and _B are 0.12 ≦ S _A ≦ 0.14, preferably 0.125 ≦
S _A ≦ 0.130, 0.09 ≦ S _B ≦ 0.118, preferably 0.105 ≦
It is necessary that S _B ≦ 0.114. This is not preferable if the values of S _A and S _B are smaller than the above lower limit values, because the impact resistance after bonding and molding deteriorates, and if S _B = S _A , the adhesion and impact resistance are low. It is not preferable because it is difficult to achieve compatibility.
On the other hand, when S _A and S _B are larger than the above upper limits, the moldability is impaired, which is not preferable. The plane orientation coefficient as used herein is measured 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. .

Further, in the present invention, the average refractive index n _A of the layer A made of the resin _A is 1.585 ≦ n _A ≦ 1.62.
Must be in the 0 range. When the average refractive index of the A layer is larger than the average refractive index of the B layer, it is more preferable in view of moldability. This is because if the average refractive index n _A is higher or lower than the above range, the moldability is impaired, which is not preferable. The average refractive index is also measured using an Abbe refractometer like the above surface orientation coefficient.

Further, in the present invention, the birefringence Δn _A of the A layer must be 12 × 10 ⁻³ or less, preferably 7 × 10 ⁻³ or less, and the B layer in the case of a laminated film is required. The birefringence Δn _{B is} also 12 × 10 ⁻³ or less, preferably 6 × 1.
It must be 0 ^-3 or less. This is because if the birefringence is too high, the moldability is impaired, which is not preferable. The birefringence is also measured using the Abbe refractometer described above.

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 surfaces of the A layer and the B layer satisfy the relation of R _A > R _B because the workability is excellent. Also,
More preferably, R _B is 0.05 or less. 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: Aggregated silica of 0.03 to
Add in the range of 1.0% by weight. Layer B: Substantially free of particles. Layer A: Aggregated silica is added in the range of 0.03 to 1.0% by weight. Layer B: Only particles selected from one or more kinds of silica selected from δ, γ, θ type alumina, zirconia, and spherical silica in a beaded shape are added. In the following formula, the aggregated silica is added to the B layer in a range not reaching 0.03% by weight.

In the present invention, the resin A preferably has a diethylene glycol amount of 1.2% by weight or less and a carboxylic acid terminal group amount of 50 eq / t or less.
By doing so, further excellent moldability is secured.

The method for producing the polyester resin of the present invention is not particularly limited, but when the metal-bonded product of the present invention is used as a container, the resin synthesized by the direct weight method has a taste aroma-preserving property. More preferable. 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 polyester film of the present invention preferably has a thickness 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. Especially 1 / 23-1
/ 1, more preferably 2/25 to 1/4, the moldability is good, which is preferable.

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, the case where the typical production method of the present invention is a laminated film of resin A and resin B will be explained, but the invention 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,
In the range of 60 to 135 ° C, the film is stretched in the longitudinal direction by 2.0 to 6.0 times, then in the range of 60 to 140 ° C in the transverse direction of 2.0 to 6.0 times, and in the range of 120 to 240 ° C. Heat treatment is performed while relaxing if 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 to provide at least one roll in contact with B immediately before stretching with a temperature difference of, for example, 1 to 5 ° C. Radiation heaters, hot air, etc. may be utilized as necessary in making the temperature difference.

[Measurement Method] (1) Deep Drawability 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 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 deep drawn can made under the conditions of (1) is filled with water and then sealed. 50 pieces of grown cans and retort-treated at 125 ° C for 8 hours and dry heat-treated at 218 ° C for 10 minutes were dropped on the floor inclined from the height of 1.3m to 15 °, and then to (1). The corrosion resistance is evaluated under the stated conditions. Total number of 0.25 mA or less and average value of 0.10 mA or less: ◎ Total number of 0.25 mA or less and average value of 0.10 to 0.18 mA: ○ to ◎ Total number of 0.25 mA or less: ○ Others: ×

(3) Taste-preserving aroma Orange drinks and coffee 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.

[0025]

【Example】

Examples 1 to 5 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 agglomerated silica 0.1 having an average particle size of 1.5 μm
3% by weight of polyester (IV = 0.72) was used, and as the resin B, the acid component was similarly composed of terephthalic acid and isophthalic acid, and the alcohol component was ethylene glycol and diethylene glycol. IV = 0.74) was used. In Example 5, resin B was added with true spherical crosslinked polystyrene particles having an average particle diameter of 0.8 μm.

The above resin A or B is fed to an extruder, and 2
Melt extrude at 80 ° C. In the case of compounding, they were laminated with a two-layer spinneret and cast as a laminated sheet. This unstretched sheet was longitudinally stretched at a stretching temperature of 105 ° C. and a stretching ratio of 3.1 times. The obtained uniaxially stretched film is guided to a tenter,
The film was transversely stretched at a stretching temperature of 110 ° C. and a stretching ratio of 3.1 times.
The biaxially stretched film is once cooled, then at 183 ° C.,
It was heat-set while performing a relaxation treatment at a lateral relaxation rate of 3%. However, in Example 2, the longitudinal stretching temperature was 101 ° C, the longitudinal stretching ratio was 3.2 times, and the heat treatment temperature was 179 ° C. In Comparative Example 2, the longitudinal stretching temperature was 106 ° C, the longitudinal stretching ratio was 2.95 times, and the heat treatment temperature was 188 ° C. In Comparative Examples 3 and 4, the longitudinal stretching temperature was 9
The temperature was 9 ° C., the longitudinal stretching ratio was 3.35, and the heat treatment temperature was 177 ° C.

The characteristics of the obtained film are shown in Table 1. As shown in Table 1, T _A , T _B , S _A , S _B , n _A , Δn
Those in which _A and Δn _B satisfy the relationship specified in the present invention were excellent in deep drawability, impact resistance, and aroma retention (Examples 1 to 5), but any one of them is out of the relationship of the present invention. In particular, the products could not satisfy the deep drawability and impact resistance (Comparative Examples 1 to 4).

[0028]

[Table 1]

[0029]

As described above, when the metal laminating film of the present invention is used, the polyester resin A
Or a laminated structure of resins A and B, and the melting peak temperatures T _A , T _B , plane orientation coefficients S _A and S _B , average refractive index n _A , birefringence Δn _A and Δn _B are specified. Since the range is set, it is possible to obtain a film having excellent formability such as deep drawing, 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 (5)

[Claims] 1. A biaxially stretched film made of polyester resin A, having a melting peak temperature T _{A of} the film,
The surface orientation coefficient S _A , the average refractive index n _A , and the birefringence Δn _A are 200 ° C. ≦ T _A ≦ 240 ° C., 0.12 ≦ S _A ≦ 0.14, 1.585 ≦ n _A ≦ 1.620, _A film for metal bonding, which satisfies Δn _A ≦ 12 × 10 ⁻³ . 2. The metal laminating film according to claim 1, wherein the resin A is a polyethylene terephthalate / isophthalate copolymer resin. 3. The resin A has a diethylene glycol content of 1.2% by weight or less and a carboxylic acid end group content of 50 eq / t.
The metal laminating film according to claim 1 or 2, which is as follows. 4. A biaxially stretched laminated film comprising a polyester resin A and a polyester resin B, wherein a film layer comprising the resin B has a melting peak temperature T _B , a plane orientation coefficient S _B and a birefringence Δn _B. , T _B ≧ T _A +1 (T _A : melting peak temperature of the film layer made of the resin A), 0.09 ≦ S _B ≦ 0.118, and Δn _B ≦ 12 × 10 ⁻³ . A film for metal bonding. 5. Surface roughness R _A , R _{B of the} resin A and resin B layers
The film for metal bonding according to claim 4, wherein R _A <R _B.