JPH09249755A - Polyester film, laminated metal board and metal vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal vessel having an excellent impact resistance, especially even after a treatment like baked paint, and a laminate film and a laminated metal board used for the vessel. SOLUTION: This is an amorphous non-oriented polyester film contg. a copolymer of polyethylene terephthalate. The polyester film to laminate a metal board is a copolymer having a group derived from naphthalene dicarboxylic acid and the components forming the film satisfy the following conditions,(1)-(3), and, moreover, the m.p. of the film is 200-250 deg.C. A laminated metal board is made by laminating the film over the metal board and a metal vessel is made using the laminated metal. (1) 3-12mol% of the dicarboxylic acid component is naphthalene dicarboxylic acid. (2) 75-97mol% of the dicarboxylic acid component is terephthalic acid. (3) Not less than 75mol% of a diol component is ethylene glycol.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminating film used for a metal material, a metal plate laminated with the film, and a metal container formed by molding the laminated metal plate into a can shape. For more details,
In particular, the present invention relates to a metal container in which a laminated film is less likely to be cracked even when dropped after baking and coating a curable resin layer, and a laminating film and a laminated metal plate used therefor.

[0002]

2. Description of the Related Art Generally, at least the inner surface of a metal can is coated with a thermosetting resin paint for the purpose of corrosion protection. This coating is performed in a can-by-can manner by a spray coating method or the like after can making, which is inefficient and requires a large amount of energy to bake the paint at a high temperature. Furthermore, there is a problem of environmental deterioration due to scattering of the organic solvent.

In recent years, in order to solve such disadvantages, a technique of pre-coating a metal plate with a paint (pre-coat technique) and a technique of laminating a film (pre-laminate technique) before forming a can have been developed. Is being done. However, these coated and laminated organic resin layers are subjected to severe deformation and heat history in the can-making process, so that defects are likely to occur after can-making. Therefore, it is difficult to exhibit sufficient corrosion resistance.

[0004] In the prelaminating technique, a polyester film mainly made of polyethylene terephthalate is used from the viewpoint of hygiene and fragrance retention. If the polyester-based film used here is stretched and oriented in advance, it cannot follow the deformation during can-making, the film will crack, the corrosion resistance will deteriorate, and the appearance of the can will also be poor. On the other hand, when the film is amorphous and non-oriented, the film does not crack even after can-making because it can easily follow the deformation during can-making, and good corrosion resistance is obtained, but the impact resistance is poor, When the can is dropped, cracks are easily formed and the corrosion resistance cannot be maintained. In particular, embrittlement due to heat history is remarkable, printing,
Further, the laminated film of the can after baking the thermosetting paint or after high-temperature sterilization treatment (retort treatment or the like) is embrittled. Therefore, when an impact is applied, the film is easily cracked.

[0005] Therefore, methods for controlling the degree of plane orientation and the degree of crystallinity of a polyester-based film to be lower have been studied. However, when a low-face orientation film is subjected to a can-making process that involves a large amount of deformation, cracks occur in the film.
In addition to this, methods such as multilayering the film to absorb impact and modifying polyester resin have been developed,
The above problem has not been solved yet.

An object of the present invention is to provide a metal container having excellent impact resistance, particularly good impact resistance even after treatment such as baking coating, and a film for lamination and a laminated metal plate used therefor. .

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a polyethylene terephthalate copolymer having a specific amount of a site derived from naphthalenedicarboxylic acid is contained, and A metal container using a metal plate laminated with an amorphous non-oriented polyester film, found that the film does not crack even when dropped, and there are few exposed metal parts, leading to the completion of the present invention. It was

That is, the present invention is as follows. (1) An amorphous non-oriented polyester film containing a polyethylene terephthalate copolymer, wherein the copolymer has a group derived from naphthalenedicarboxylic acid, and the components forming the film are the following: And the melting point of the film is 200 to 250 ° C. A polyester film for metal plate lamination. 3 to 12 mol% of the dicarboxylic acid component is naphthalenedicarboxylic acid. 75 to 97 mol% of the dicarboxylic acid component is terephthalic acid. 75 mol% or more of the diol component is ethylene glycol. (2) A laminated metal plate obtained by laminating the polyester film according to (1) on at least one side of a metal plate. (3) A laminated metal plate obtained by biaxially stretching the polyester film as described in (1), laminating it on at least one surface of a metal plate, further melting, and then rapidly solidifying. (4) The laminated metal plate according to (2), wherein the metal plate is an aluminum plate. (5) A metal container formed by using the laminated metal plate according to any one of (2) to (4). (6) The metal container according to (5), which is further coated with at least one thermosetting resin layer. (7) A metal container obtained by drawing and ironing using the laminated metal plate according to any one of (2) to (4).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester film of the present invention comprises a polyethylene terephthalate copolymer having a group derived from naphthalenedicarboxylic acid. The group derived from naphthalenedicarboxylic acid contained in the copolymer is contained in the range in which 3 to 12 mol% of the dicarboxylic acid component forming the polyester film of the present invention becomes naphthalenedicarboxylic acid, and further contains 75 to 5 of the dicarboxylic acid component. 97 mol% is terephthalic acid, and 75 mol% or more of the diol component is ethylene glycol. The polyester film of the present invention is amorphous and non-oriented and has a melting point of 200 to 2
50 ° C.

The polyethylene terephthalate copolymer has ethylene glycol as a diol component and naphthalene dicarboxylic acid and terephthalic acid as dicarboxylic acid components. Examples of naphthalenedicarboxylic acid include 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid is preferable from the viewpoint of economical availability.

The above-mentioned components in the polyethylene terephthalate copolymer may be blended within a range that does not impair the characteristics of the polyester film described later.

The polyethylene terephthalate copolymer is produced by a method known per se using terephthalic acid, naphthalenedicarboxylic acid and ethylene glycol. For example, it can be obtained by polycondensation under melting by a transesterification method or a direct polymerization method. The step of incorporating a group derived from naphthalenedicarboxylic acid into the polyethylene terephthalate copolymer is as follows:
It may be at any stage such as in the extruder after the polymerization.

The polyethylene terephthalate copolymer may further contain groups derived from other dicarboxylic acids, other diols, oxycarboxylic acids and tricarboxylic acids as long as the characteristics of the polyester film described later are not impaired.

Other dicarboxylic acids include oxalic acid, succinic acid, adipic acid, sebacic acid, maleic acid,
Examples thereof include dimer acid, indandicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, and sulfoisophthalic acid metal salt.

Other diols include propanediol, butanediol, pentanediol, neopentyl glycol, hexanediol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol S, polyethylene glycol, polytetradiol. Examples thereof include methylene glycol.

Examples of the oxycarboxylic acid component include oxybenzoic acid.

Examples of the tricarboxylic acid component include trimellitic acid and trimethylolpropane.

The polyester film of the present invention may be a film made of the above polyethylene terephthalate copolymer, or may be a blend of two or more kinds of polyesters containing the same. However, it is necessary that the contents and melting points of naphthalenedicarboxylic acid, terephthalic acid and ethylene glycol are within the ranges described below.

In the polyester film of the present invention, 3 to 12 mol% of the dicarboxylic acid component forming the film is naphthalenedicarboxylic acid. If the naphthalene dicarboxylic acid content exceeds 12 mol% based on the total dicarboxylic acid components, it is not economical. In addition, the biaxially stretched film may have a bad film forming property. Furthermore, since the glass transition temperature rises, if the can manufacturing temperature is low, the film followability during can manufacturing may be poor. On the other hand, if it is less than 3 mol%, the impact resistance after can making is not sufficient.

The naphthalenedicarboxylic acid content in the dicarboxylic acid component forming the film is preferably 5 to 10 mol%.

In the polyester film, 75 to 97 mol% of the dicarboxylic acid component forming the film is terephthalic acid, and 75 mol% or more of the diol component is ethylene glycol. If these are less than 75 mol%, the melting point of the polyester film is lowered and the heat resistance to heat treatment such as baking coating tends to be insufficient. In addition, the film-forming property when obtaining a biaxially stretched film tends to deteriorate.

In the dicarboxylic acid component forming the film, terephthalic acid is preferably 85 to 95 mol%. In the diol component forming the film, ethylene glycol is preferably 90 mol% or more.

The melting point of the polyester film of the present invention is in the range of 200 to 250 ° C. The melting point is preferably 250 ° C. or lower from the viewpoint of workability and energy saving when the film is fused to a metal plate or when the film is melted. On the other hand, the melting point thereof needs to be 200 ° C. or higher from the viewpoint of heat resistance against heat treatment such as baking coating and film-forming properties when producing a biaxially stretched film. It is preferably 210 to 235 ° C.

In the present invention, the melting point is determined by using a differential scanning calorimeter (DSC) with a sample amount of 10 mg and a heating rate of 20.
Measured in ° C / min.

The melting point of the polyester film of the present invention is adjusted mainly by the contents of the groups derived from terephthalic acid and the groups derived from ethylene glycol.

The polyester constituting the polyester film of the present invention has a reduced viscosity of 0.40 to 1.0 d.
1 / g, particularly 0.5 to 0.8 dl / g is preferable. If the reduced viscosity is less than 0.4 dl / g, the impact resistance of the metal container tends to be insufficient. Reduced viscosity is 1.0d
If it exceeds 1 / g, the costs of polymerizing raw materials, forming a film, producing a laminated metal plate, etc. tend to increase.

In the present invention, the reduced viscosity is a value measured at a solution concentration of 0.4 g / dl and a temperature of 30 ° C. using a mixed solvent of phenol / tetrachloroethane in a weight ratio of 6/4.

The reduced viscosity of the polyester constituting the polyester film of the present invention is the degree of polymerization of each polyester used as a raw material, the moisture content of the raw material, the temperature and time of extrusion, and the temperature at which the polyester is remelted on a metal plate. It is adjusted by time etc.

Further, the polyester film used for the laminated metal plate of the present invention is amorphous and non-oriented.
In the present invention, amorphous means a film having a density of 1.3.
It means a film having a low crystallinity of 5 g / cm ³ or less. Non-oriented means that the plane orientation coefficient obtained from the refractive index is 0.
It means a film of 01 or less.

The density of the film was measured using a density gradient tube of carbon tetrachloride and heptane.

The surface orientation coefficient was determined from the following formula by measuring the refractive index (Nx, Ny and Nz) in the film flow direction, width direction and thickness direction using a refractometer with a polarizing plate. The filling liquid is diiodomethane, and the light source is a sodium lamp. Plane orientation coefficient = (Nx + Ny) / 2-Nz

The amorphous non-orientation of the polyester film of the present invention is adjusted by setting the cooling rate when the molten film is solidified to 10 ° C./sec or more, preferably 50 ° C./sec or more.

The polyester film of the present invention may be a single layer or multiple layers. The thickness of the film is usually 8 to 50.
μm, preferably 10 to 20 μm.

The polyester film of the present invention may be subjected to corona treatment, coating treatment, flame treatment or the like in order to improve the adhesiveness and wettability depending on the use.

The polyester film of the present invention contains, for example, a white pigment, a lubricant, an antiblocking agent, and
Known additives such as a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent and an impact resistance improver may be blended.

The laminated metal plate of the present invention comprises the above polyester film laminated on at least one surface of the metal plate.

The material of the metal plate is not particularly limited, and examples thereof include iron, steel, tin plate, tin-free steel, brass, copper,
Aluminum, an aluminum alloy and the like can be mentioned. The metal plate used in the present invention may be surface-treated. The surface treatment includes electrochemical treatment, inorganic chemical treatment, organic chemical treatment, etc., for example, chromate treatment,
Examples include phosphoric acid chromate treatment, zinc chromate treatment, and alumite treatment.

The at least one surface of the metal plate may be the can inner surface side, the can outer surface side, or both the inner and outer surfaces after can making. In particular, it is preferable to laminate a film on the inner surface side of the can which is strongly required to have corrosion resistance.

The method for producing the laminated metal plate of the present invention, that is, the method for laminating the polyester film on the metal plate, includes, for example, (1) fusing or adhering a biaxially stretched film to the metal plate, then melting and rapidly solidifying Method, (2) a method of fusing or adhering an unstretched film, and (3) a method of directly fusing to a metal plate by an extrusion laminating method. In particular, the method (1) is preferable because a thin film with less unevenness in thickness can be laminated on the metal plate. Here, the laminated metal plate with less thickness unevenness is particularly suitable for the drawing and ironing process described later.

Examples of the method of fusing or adhering the biaxially stretched film to the metal plate include a method of pressure-bonding the film to the metal plate warmed to the softening point of the film or higher.
Since the film laminated on the metal plate remains biaxially oriented, an amorphous non-oriented polyester layer can be obtained by further melting the film to eliminate the orientation and then rapidly solidifying.

Examples of the heating method for completely melting the film include hot air heating, roll heating, electric current heating, dielectric heating and high frequency heating. For example, in the case of hot air heating, it is usually 15 to 120 at the melting point of the film to the melting point + 40 ° C.
30 to 60 seconds, preferably at melting point +5 to melting point + 20 ° C.
Heated for seconds.

Further, as the method for rapid solidification, there may be mentioned a method such as immersion in water, spraying with cold air or the like. Here, the rapid cooling is a cooling operation having a cooling rate sufficient to prevent the formation of crystals when the molten film is solidified, and is usually 10 ° C./sec or more, preferably 50 ° C./sec or more. .

Here, the biaxially stretched film is produced by forming and stretching by a known method. For example,
(1) A method in which an unstretched sheet melt-extruded from a T-die is stretched in the machine direction by a roll type stretching machine, and then stretched in the transverse direction by a tenter type stretching machine (sequential biaxial stretching method), (2) unstretched Examples of the method include a method of simultaneously stretching the sheet in the longitudinal and transverse directions with a tenter type simultaneous biaxial stretching machine (simultaneous biaxial stretching method), (3) a method of expanding a sheet melt-extruded into a tube shape by gas pressure and stretching (inflation method), and the like. To be

The metal container of the present invention is formed by using the above-mentioned laminated metal plate, and is, for example, a three-piece can having a lid, a body and a bottom separate from each other, a two-piece can having a can body and a lid integrated with the bottom, and the like. Molded. Examples of the two-piece can include a shallow drawn can made by a drawing method, a redrawn can made by a drawing redrawing method, a thinned drawn can made by a drawing stretching and stretching method, and a drawing ironing method (DI
Method) and a drawn ironing can (DI can). For example, a drawing and ironing method (DI method), that is, a metal plate is punched out into a blank, drawing is performed between a drawing die and a punch to form a cup, and the can body wall of the cup is punched into the cup and the cup. By forming a gap smaller than the plate thickness between the ironing rings provided on the outer periphery by ironing and ironing, the can body wall is gradually thinned and at the same time formed into a high can body.

Particularly, a metal container suitable for use with the laminated metal plate of the present invention undergoes a large deformation during processing, and therefore when the oriented films are laminated, the film cannot follow the deformation. It is a squeezed and squeezed aluminum can (DI can).

The metal container of the present invention may be coated with at least one thermosetting resin layer by a conventional method in order to improve the scratch resistance of the surface. As the thermosetting resin,
Epoxy resins, melamine resins, alkyd resins and the like can be mentioned. For example, a thermosetting top clear paint or the like may be baked.

[0047]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The methods for evaluating physical properties in the following examples and comparative examples are as follows.

(1) Melting Point The melting point of the polyester film peeled off from the laminated metal plate is measured by the external heating type differential scanning calorimeter (D
SC), sample amount 10 mg, heating rate 20 ° C /
Measured in minutes. Here, the melting endothermic peak temperature was defined as the melting point.

(2) Density The polyester film peeled from the laminated metal plate was measured using a density gradient tube of carbon tetrachloride and heptane.

(3) Plane orientation coefficient Using a refractometer with a polarizing plate manufactured by Atago Co., Ltd., the flow direction of the polyester film peeled from the laminated metal plate,
Refractive index in the width and thickness directions (Nx, Ny, respectively)
And Nz) were measured, and the plane orientation coefficient was determined from the following equation.
Diiodomethane was used as the filling liquid, and a sodium lamp was used as the light source. Plane orientation coefficient = (Nx + Ny) / 2-Nz

(4) Reduced viscosity A polyester film peeled from a laminated metal plate was dissolved in a mixed solvent of phenol / tetrachloroethane in a weight ratio of 6/4 to a solution concentration of 0.4 g / dl, and an Ubbelohde viscosity was obtained. The reduced viscosity was measured at a temperature of 30 ° C. using a tube.

(5) ERV of can immediately after production The prepared DI can was filled with 350 ml of 1% by weight saline and the ERV (enamel rating value) was measured with an enamel meter. The voltage is 6 V DC, the exposed metal part is made on the outside of the bottom of the can, and it is connected to the anode.
The current value after 30 seconds was measured.

(6) ERV of can after drop impact (before heat treatment) The prepared DI can was filled with 350 ml of water and dropped from a height of 1 m with the bottom of the can facing downward, and then the water was removed (5) The ERV was measured in the same manner as above, except that the saline solution was filled.

(7) ERV of can after drop impact (after heat treatment) The prepared DI can is heated to 200 according to the baking treatment condition.
After heat treatment at 15 ° C. for 15 minutes, ERV after drop impact was applied in the same manner as in (6).

Production Examples 1 to 7 Dicarboxylic acid components and diol components were polycondensed under melting by the transesterification method or the direct polymerization method in the proportions shown in Table 1. Here, as Production Example 6, Kodar (manufactured by Eastman Chemicals), which is polyethylene terephthalate copolymerized with 35% by mole of cyclohexanedimethanol, was used.

[0056]

[Table 1]

Examples 1 to 4 and Comparative Examples 1 to 9 (Preparation of Biaxially Stretched Film) The polyester chips obtained in Production Examples 1 to 7 and polyethylene terephthalate chips having a reduced viscosity of 0.65 dl / g were used. The ingredients were blended in the amounts shown in Table 2 and vacuum dried to a water content of 0.01% by weight or less. Here, in Example 2 and Comparative Example 1, the polyester chips of Production Example 7 were used. To all the polyesters, silica gel fine powder having an average particle diameter of 1.8 μm was added and dispersed so as to be contained in the film in an amount of 0.6% by weight in order to prevent the film from blocking and to impart slipperiness. This was melt extruded from a T-die with an extruder at 270 ° C. and taken up on a cooling roll at 30 ° C. to obtain an unstretched sheet. The sheet was immediately stretched 3.2 times at 90 ° C. in the machine direction by a roll type stretching machine, and further stretched at 100 ° C. by 4 times in the transverse direction by a tenter type stretching machine. Furthermore, the film
While being relaxed by 10%, heat setting was performed at (melting point -30) ° C to obtain a stretched film having a thickness of 12 µm.

(Production of laminated metal plate) Thickness 0.3 m
The biaxially stretched film was fused with a roll laminator on both surfaces of a phosphoric acid chromate-treated aluminum plate having a width of m and a width of 20 cm. Here, the aluminum plate is supplied at room temperature, the rubber roll temperature is 180 to 250 ° C., the passing speed is 25 to 100 cm / min, and the gauge pressure is 6 kg / cm ^2.
It is. The aluminum plate having the biaxially stretched film fused thereto was heated in a hot air oven at 200 to 270 ° C. for 30 to 90 seconds to completely melt the film. This was taken out of the oven, immersed in water at 15 to 25 ° C. within 5 seconds, and the film was solidified to obtain a laminated metal plate. However, in Comparative Example 1, a laminated metal plate was prepared by fusion-bonding a biaxially stretched film to an aluminum plate without performing the amorphous non-orientation treatment of melting and quenching.

(Production of DI Can) The laminated metal plate was cut into a circle having a diameter of 150 mm, drawn and ironed,
Diameter 66mm, height 125mm, wall thickness 0.12m
m DI cans were prepared.

Tables 2 and 3 show the characteristics of the polyester film laminated on the laminated metal plate and the characteristics of the DI can using the same.

[0061]

[Table 2]

[0062]

[Table 3]

As shown in the table, the can according to the present invention has few film defects and a low ERV value. Moreover, the ERV value was low even when a drop impact was applied, and it was difficult for the film to have cracks or defects. Furthermore, even if a drop impact is applied after receiving a heat history equivalent to baking coating, ERV
The value is low, and the film is less prone to cracks and defects. ERV
In the value measurement, the more the current flows, the more defective the film that is an insulator is, and the metal is exposed, so that corrosion is likely to occur. Therefore, the ERV value immediately after can making and the ERV value after the can drop impact before heat treatment. The ERV value after the drop impact of the can after heat treatment is preferably 20 mA or less. On the other hand, in Comparative Examples 3 to 8 in which a copolymerization component other than naphthalene dicarboxylic acid was used, the ERV value when the drop impact was applied to the can after heat treatment was high, and the impact resistance of the can after treatment such as baking coating was high. Considered inferior. Also, in the case of Comparative Example 2 in which the content of naphthalene dicarboxylic acid is small, it is considered that the ERV value when the drop impact is applied to the can after the heat treatment is high, and the impact resistance of the can after the treatment such as baking coating is poor. To be In Comparative Example 1, after the biaxially stretched film was fused to the aluminum plate, the aluminum plate was melted,
A DI can was obtained by performing squeezing and ironing without performing the amorphous non-oriented process of quenching. The obtained can had a large amount of peeling of the film, and had a high ERV value immediately after making the can. Comparative Example 9
In the case of No. 2, after the heat treatment, avatar-like unevenness was generated on the film surface, and the film had no commercial value.

[0064]

According to the present invention, it is possible to provide a metal container which is excellent in can processability, impact resistance and corrosion resistance, and a laminating film and a laminated metal plate used therefor. In particular, embrittlement due to heat treatment such as baking coating and retort treatment is unlikely to occur, and occurrence of film cracks and the like can be suppressed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B32B 27/36 B32B 27/36 B65D 25/36 B65D 25/36 65/40 65/40 A C08G 63 / 189 NMZ C08G 63/189 NMZ // B29K 67:00 B29L 7:00 (72) Inventor Yoshinori Takekawa 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. (72) Inventor Shinji Suzuki 2-1-1 Katata, Otsu City, Shiga Prefecture, Toyobo Co., Ltd. Research Institute (72) Inventor Toru, 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Institute

Claims (7)

[Claims] 1. An amorphous non-oriented polyester film comprising a polyethylene terephthalate copolymer, wherein the copolymer has a group derived from naphthalene dicarboxylic acid, and the component forming the film is The following conditions are satisfied, and the melting point of the film is 200 to 250.
A polyester film for laminating metal plates, which is characterized by being at a temperature of ℃. 3 to 12 mol% of the dicarboxylic acid component is naphthalenedicarboxylic acid. 75 to 97 mol% of the dicarboxylic acid component is terephthalic acid. 75 mol% or more of the diol component is ethylene glycol. 2. A laminated metal plate obtained by laminating the polyester film according to claim 1 on at least one side of a metal plate. 3. A laminated metal plate obtained by biaxially stretching the polyester film according to claim 1, laminating it on at least one side of a metal plate, further melting and then rapidly solidifying. 4. The metal plate is an aluminum plate.
Laminated metal plate described. 5. A metal container formed by using the laminated metal plate according to claim 2. 6. The metal container according to claim 5, which is further coated with at least one thermosetting resin layer. 7. A metal container obtained by drawing and ironing using the laminated metal plate according to claim 2.