JP3329052B2 - White polyester film for metal plate lamination and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester film for laminating a metal plate. More specifically, after lamination with metal, when forming by drawing or ironing, it has good lamination workability, adhesion, moldability, impact, and slipperiness, and is excellent in white hiding. In particular, the present invention relates to a white polyester film for metal plate lamination suitable for a metal can produced by molding.

[0002]

2. Description of the Related Art Conventionally, the inner and outer surfaces of a metal can are coated with various thermosetting resins, such as epoxy and phenol, dissolved or dispersed in a solvent to prevent corrosion. Has been widely practiced. However, such a method of coating the thermosetting resin requires a long time for drying the paint, and has unfavorable problems such as a decrease in productivity and environmental pollution due to a large amount of an organic solvent.

[0003] As a method of solving these problems, a polyester film is laminated on a steel plate, an aluminum plate, or a metal plate which has been subjected to various surface treatments such as plating, which is a material for a metal can. When a metal can is manufactured by drawing or ironing a plate, the polyester film is required to have the following characteristics.

(1) The adhesiveness to a metal plate is excellent.

(2) It is excellent in moldability.

(3) The polyester film does not peel off, crack or pinhole due to impact on the metal can.

(4) The scent component of the contents of the can is not adsorbed on the film or the film does not impair the flavor of the contents (hereinafter referred to as taste characteristics).

(5) The film for coating the outer surface of a can has a sufficient concealing property comparable to a white coating which is an undercoat of a white pigment.

Many proposals have been made to solve these demands. For example, Japanese Patent Application Laid-Open No. 64-22530 discloses a polyester film having a specific density and plane orientation coefficient, and Japanese Patent Application Laid-Open No. 2-57339 discloses a polyester film. Discloses a copolymerized polyester film having specific crystallinity. However, these proposals do not comprehensively satisfy the above-described various required properties, and cannot be said to be at a level that can sufficiently satisfy particularly impact resistance and taste properties.

[0010] Particularly, in the case of a white film for coating the outer surface, for example, Japanese Patent Application Laid-Open Nos. Hei 5-170942 and Hei 5
JP-A-331301 discloses a white pigment-containing biaxially oriented film having a crystal orientation in a specific thickness direction. However, these proposals still do not provide sufficient hiding power, and if the white pigment content is increased to increase the white hiding power, the film has a large Young's modulus. There is a problem of lowering, and in order to improve the concealment property, it is necessary to further perform white printing as an overcoat. Such a problem is a problem that becomes more prominent as the thickness of the film is reduced in consideration of cost.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, including workability and adhesion during lamination with a metal plate, moldability during can making, and the like. An object of the present invention is to provide a white polyester film for laminating a metal plate which is excellent in heat resistance and impact resistance and has a sufficient concealing property and is suitable for a metal can produced by molding.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester (I) mainly comprising ethylene terephthalate.
And polyester (II) mainly comprising butylene terephthalate in a weight ratio of 50:50 to 90:10, containing a colorant in an amount of 20 to 50% by weight, and having a Young's modulus of the film of 50 to 350 kg / mm. ² , which can be achieved by a white polyester film for laminating a metal plate.

Preferably, it can be achieved by a white polyester film for laminating a metal plate, wherein the intrinsic viscosity [η] of the polymer component constituting the film is 0.65 or more.

According to the present invention, it is possible to obtain, for the first time, the above-mentioned constitution, which has excellent formability even in draw forming and ironing under severe forming conditions, and provides good white hiding properties. It is.

The polyester (I) mainly comprising ethylene terephthalate in the present invention may be either a homopolyester or a copolyester.
In the case of a copolyester, the rigidity of the film is high when at least 80 mol% is an ethylene terephthalate unit,
It is preferable from the viewpoint of workability at the time of lamination, moldability at the time of can-making, heat resistance, impact resistance and other mechanical properties, and more preferably at least 90 mol%. As the copolymer component, an acid component or a glycol component may be used, but as the acid component, for example,
Isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, aromatic dicarboxylic acids such as phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, Dimer acid,
Examples thereof include aliphatic dicarboxylic acids such as maleic acid and fumaric acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and oxycarboxylic acids such as p-oxybenzoic acid. Of these, isophthalic acid and naphthalenedicarboxylic acid are preferred from the viewpoint of mechanical properties such as processability and impact resistance. On the other hand, examples of the glycol component to be copolymerized include aliphatic glycols such as propanediol, pentanediol, hexanediol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, and aromatic compounds such as bisphenol A and bisphenol S. Glycol and the like. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination.

As long as the effects of the present invention are not impaired, a polyester (I) obtained by copolymerizing a polyfunctional compound such as trimellitic acid, trimesic acid or trimethylolpropane may be used.

In the present invention, in order to improve the impact resistance, the diethylene glycol component is preferably used in an amount of 0.1 to 0.1.
The content of the polyester by heat history in a can-making process or the like may be from 0.01 to 1% by weight, more preferably from 0.01 to 0.8% by weight, and particularly preferably from 0.01 to 0.6% by weight. This is preferable because deterioration can be suppressed.

The polyester (II) mainly comprising butylene terephthalate in the present invention is preferably such that at least 80 mol% is a butylene terephthalate unit, more preferably 90 mol%, in view of heat resistance and mechanical properties.
That is all. The acid component to be copolymerized is the same as the polyester (I), and the glycol component is
Examples thereof include aliphatic glycols such as propanediol, pentanediol, hexanediol, and neopentyl glycol; alicyclic glycols such as cyclohexanedimethanol; and aromatic glycols such as bisphenol A and bisphenol S. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination.

The polyester film of the present invention is mainly composed of the polyester (I) and the polyester (II). The composition ratio of the polyester (I) and the polyester (II) is 50:50 to 90 by weight. : 10
It is. From the viewpoint of workability and mechanical properties, preferably 55:
The ratio is from 45 to 85:15, and such a ratio can be appropriately set within the above range from the colorant concentration of a high-concentration master using polyester (II) described later and the colorant content of a desired film.

Incidentally, the polyester film of the present invention comprises:
The intrinsic viscosity [η] is preferably 0.65 or more from the viewpoint of processability during lamination, moldability during can making, and mechanical properties such as impact resistance. It is more preferably at least 0.70, further preferably at least 0.75. If the intrinsic viscosity [η] is too low, the strength of the film itself is not sufficient, resulting in poor mechanical properties such as workability during lamination, moldability during can-making, and impact resistance. Such intrinsic viscosity [η]
Has a high molecular weight of 0.65 or more, because the coloring agent can be contained at a higher concentration, which is preferable.

The content of the colorant in the film is preferably 20 to 5 with respect to the polyester component from the viewpoint of concealing properties.
It must be contained in the range of 0% by weight, but preferably 2% by weight.
The content is preferably 5 to 50% by weight, more preferably 30 to 50% by weight. In general, as the content of the colorant increases, the concealing property increases, but conversely, mechanical properties such as film strength and workability greatly decrease. It is now possible to achieve both mechanical properties and mechanical properties.

As such a coloring agent, as white inorganic particles, titanium oxide, zinc white, zinc sulfate, lithopone, lead white,
White pigments such as basic lead sulfate, basic lead silicate and lead zinc white can be mentioned. Among them, titanium oxide having a high refractive index, especially rutile type titanium oxide, zinc white, zinc sulfate, lithopone, etc. It can be preferably used. The average particle size of the white inorganic particles is preferably in the range of 0.01 to 8 μm, but is preferably in the range of 0.1 to 0.5 μm because more excellent hiding properties can be obtained. In addition, inorganic particles such as wet and dry silica, colloidal silica, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, magresium carbonate, calcium silicate, alumina, mica, kaolin, clay, and styrene, silicone, acrylic acids, etc. Organic particles and the like as constituent components may be used in combination, if necessary, in order to improve the handleability (slidability) of the film and the molding process of the metal can. These inorganic and / or organic particles are 2
More than one species may be used in combination. Further, a pinking agent, a bluing agent and the like may be used in combination.

The colorant-containing polyester in the present invention can be obtained by mixing the polyester (I), the polyester (II) and the colorant in the above-mentioned range and then melt-kneading them. The kneading method includes a so-called masterbatch method of mixing and kneading a kneaded product composed of a polyester (II) containing a high concentration of a coloring agent and a polyester (I) in advance.
Alternatively, a dry coloring method in which the amounts of the polyester (I), polyester (II) and the colorant in the above range are directly mixed and kneaded can be mentioned, but the dispersibility, the concealing property, the handling, and the like of the colorant are excellent. Further, the masterbatch method is preferable also from the viewpoint of production cost. In such a masterbatch method, it is preferable to use polyester (II) as the base polymer in terms of dispersibility and polymer stability. The concentration of the colorant in the masterbatch method is preferably 60:40 to 25:75 in terms of the weight ratio of polyester (II): colorant from the viewpoint of dispersibility, polymer quality, cost, and the like. In particular, when potybutylene terephthalate is used, a pre-drying of the polymer is not required, and a master batch having a colorant concentration of more than 70% can be kneaded with good dispersibility without significantly lowering the polymer molecular weight. Is preferred.

As a preferred embodiment of the present invention, a polyester (III) mainly composed of ethylene terephthalate having a melting point of 150 to 230 ° C. is added to the film A layer composed of the polyesters (I) and (II) containing the above colorant. ) Is preferably a laminated film in which the layer B composed of With such a laminated structure, without impairing mechanical properties and heat resistance such as rigidity, without interposing an adhesive primer layer such as an epoxy-based adhesive, an epoxy-ester-based adhesive, and an alkyd-based adhesive, It can be easily thermally bonded to a metal plate. The polyester (III) is a polyester comprising 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% or more of ethylene terephthalate units, and the copolymerization component is the same as the polyester (I). Among them, isophthalic acid is particularly preferable.

Further, as another preferred embodiment of the present invention, polyesters (I), (I)
Polyester (I) having a melting point of 220 ° C. or more based on ethylene terephthalate
It is also preferable to form a laminated film in which the C layer composed of V) is laminated. By adopting such a laminated structure and making the C layer the outer surface (the surface opposite to the surface in direct contact with the metal plate), impact resistance and taste characteristics can be improved. The polyester (IV) is a polyester comprising ethylene terephthalate units preferably in an amount of 85 mol% or more, and the same copolymer component as that of the polyester (I) can be used. preferable. In addition, inorganic particles and / or organic particles may be added to the C layer as needed in order to improve the handleability and the molding process.

In the production of the polyester film of the present invention, additives such as an antioxidant, a plasticizer, an antistatic agent, a weathering agent, and a terminal blocking agent can be used as needed. In particular, the combined use of an antioxidant is preferable because deterioration of the polyester due to heat history in the can-making process is prevented.

The polyester film of the present invention is required to have a Young's modulus of the film in the range of 50 to 350 kg / mm ² . Here, the Young's modulus is an average value in the MD direction (longitudinal direction) and TD direction (width direction) of the film. If either one is out of this range, it is difficult to handle or has excellent can-making properties. And the mechanical properties after can making are inferior. Young's modulus is 100-3
The range of 00 kg / mm ² is preferable, and 150 to 300 k
It is more preferably in the range of g / mm ² . Especially 60 ° C
In this case, the Young's modulus is preferably in the range of 100 to 300 kg / mm ² .

The polyester film of the present invention may be in the form of an unstretched sheet such as a cast film, or, if necessary, in the case of a stretched film in which the cast film is stretched uniaxially or biaxially, orientated by heat treatment in a subsequent step. May be deleted, and the Young's modulus may be set in the above range. Preferably, it is an unstretched sheet such as a cast film.

Although the thickness of the polyester film of the present invention is not particularly limited, it is preferably 5 to 50 μm, more preferably 8 to 40 μm, in consideration of moldability, impact resistance and white hiding property of the metal can. Is 10-35
μm.

In the case of the laminated film, the ratio of the thickness of the layer A to the thickness of the layer B is 20: 1 to 1: 1 (A
Layer: B layer) is preferable in terms of adhesiveness, workability, and impact resistance, and especially 15: 1 to 4: 1 (A layer: B layer) in terms of workability and impact resistance. Is more preferable.

The polyester film of the present invention can be formed by any conventionally known method.

Next, the method for producing the film of the present invention will be described, but is not limited thereto. First, using high molecular weight polyester (II) as the base polymer,
A titanium oxide having an average particle size of 0.25 μm is used as a coloring agent, and a fixed amount is supplied to a twin-screw vented extruder to prepare a master having a high concentration of titanium oxide (for example, 70% by weight). In preparing the masterbatch, the base polymer or the colorant may be preliminarily dried and kneaded, but may be formed into a masterbatch without drying in advance. As described above, by using the polyester (II), the quality of the polymer before and after kneading is stable.

Next, the high-concentration master chip and the high molecular weight polyester (I) are mixed at a desired weight ratio to obtain a polymer composition for the layer A.

On the other hand, a high molecular weight polyester (III) is prepared for the layer B, and the polymer composition for the layer A and the polymer for the layer B are supplied to separate extruders of a biaxial vent type and melted.
Thereafter, two layers are laminated by a feed block, discharged from a normal die, and then cooled and solidified by a mirror drum or a cooling drum having a roughened surface to obtain a cast film. The two-layer laminated film thus obtained is subjected to heat aging or surface activation treatment as required, and then wound up. The heat aging treatment and the surface activation treatment are performed by dissolving gas in the film,
For example, this is an effective process for scattering a gas such as tetrahydrofuran.

If necessary, the polyester cast film may be biaxially stretched simultaneously or sequentially. However, when the film is stretched, the Young's modulus of the film may be reduced to 50 by heat treatment after stretching. ~ 350k
It is important to set it in the range of g / mm ² .

The metal plate in the present invention is not particularly limited, but is preferably a metal plate made of iron, aluminum or the like in view of formability. Further, in the case of a metal plate made of iron, an inorganic oxide coating layer on the surface thereof for improving adhesion and corrosion resistance, for example, chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment , Chromate treatment,
A chemical conversion coating layer represented by chromium chromate treatment may be provided. In particular, a chromium hydrated oxide having a chromium equivalent of 6.5 to 150 mg / m ^{2 in} terms of chromium is preferable, and a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gunmetal, or brass may be provided. Good. It is preferable that tin plating has a plating amount of 0.5 to 15 mg / m ² , and nickel or aluminum has a plating amount of 1.8 to 20 g / m ² .

The white polyester film for metal lamination of the present invention is suitably used for coating the inner and outer surfaces of a two-piece metal can produced by drawing or ironing, particularly for the outer surface where good white concealability is required. can do. Further, it can be preferably used for covering a lid portion of a two-piece can or a body, a lid, and a bottom of a three-piece can because it has good metal adhesion and moldability.

[0038]

[Method for measuring and evaluating characteristics] The characteristics of the polyester film were measured and evaluated by the following methods.

(1) Intrinsic Viscosity of Polyester Polyester is dissolved in orthochlorophenol,
Measured in ° C. The unit is dl / g.

(2) Melting Point of Polyester A polyester chip was crystallized, and subjected to 10 ° C./C with a differential scanning calorimeter (DSC-2, manufactured by Perkin-Elmer Co.).
The measurement was performed at a heating rate of min.

(3) Young's modulus of film Measured according to ASTM-D-882-81 (Method A) (tensile speed: 300 mm / min). The values were obtained as average values in the MD direction (longitudinal direction) and TD (width direction) of the film.

(4) Adhesiveness The polyester film of the present invention and TFS were placed between a metal roll and a silicon rubber roll heated to 180 to 230 ° C.
(Tin Free Steel) plates were joined together, and pressure-bonded at a pressure of 30 kg / cm, and cooled in air after bonding. The adhesive strength of the laminate was determined by a peel test at an angle of 180 °, and a laminate having an adhesive strength of 250 g / cm or more was rated as good.

(5) Formability The bonding surface of the polyester film and the TFS plate are laminated under heat and pressure, and deep-drawn using a drawing die and a punch. The drawing ratio is 100 mm in diameter D and 130 mm in depth h. A (h / D) 1.0 cup (side seamless can) was obtained. A 1% saline solution was put in the cup, the whole was heated to 80 ° C., left for 24 hours, and moldability was judged from the condition of rust generated in the can.

Class A: No rust generated Class B: Less than 3 rusts of 1 mm or less C class: Many rusts generated

(6) Impact resistance After the can is made in the above (5), a heat treatment is performed at 200 ° C. for 10 minutes. After being left in the heated saline for 24 hours, rust was observed on the portion that was impacted with the punch, and (5)
The same evaluation was performed.

[0046]

The present invention will be described in detail with reference to the following examples.

Example 1 First, as the polyester (II), the intrinsic viscosity [η] 1.
No. 0 polybutylene terephthalate (melting point: 221 ° C.) was used as a base polymer for a masterbatch, and rutile-type titanium oxide (average particle size: 0.25 μm) was quantitatively supplied to a twin-screw vented extruder without preliminary drying. Then, a high-concentration master chip containing 70% by weight of titanium oxide was prepared. In forming such a master batch, the intrinsic viscosity of the polymer hardly changed before and after kneading. Thereafter, as the master chip and the polyester (I), 17.5 mol% copolymerized polyethylene terephthalate ([η] = 0.85, melting point: 213 ° C.) was used in a weight ratio of 4: 3.
And fed to a twin-screw vented extruder to melt,
After discharging from a normal die, it is cooled and solidified by a cooling drum and
A 0 μm cast film was obtained. The obtained film had a titanium oxide content of 40% by weight and an intrinsic viscosity [η] =
0.80, and the Young's modulus of the film is 260 kg / m.
m ² . The Young's modulus of the film at 60 ° C. was 160 kg / mm ² .

The cast film thus obtained was treated with TF
It was laminated with an S (Tin Free Steel) plate, but the film could be processed well without stretching and wrinkling during lamination. Using a drawing die and a punch,
Although a cup (can) was formed by deep drawing, the film had a good appearance without cracks or pinholes in the film. In addition, it had good white opacity, no blackness of the TFS as the base was recognized, and had whiteness that did not need to be supplemented by white printing at all.

Example 2 Polybutylene terephthalate having an intrinsic viscosity [η] of 1.0 (melting point: 221 ° C.) was used as a base polymer for a masterbatch as a polyester (II), and rutile-type titanium oxide (average particle size: 0.25 μm) was used. ) Was supplied quantitatively to a twin-screw vented extruder, and a high-concentration master chip containing 70% by weight of titanium oxide was prepared in the same manner as in Example 1. As the master chip and polyester (I), polyethylene terephthalate ([η] = 1.0, melting point: 263 ° C.) was blended at a weight ratio of 4: 3 to obtain a polymer composition for layer A. On the other hand, as the polyester (III) for the layer B, isophthalic acid 17.5 mol% copolymerized polyethylene terephthalate ([η] = 0.85, melting point 213 ° C.) was separately prepared, and separately extruded by a biaxial venting method. It is supplied to the machine and melted. After that, it is laminated in a feed block into two layers (layer A / layer B = 5/1), discharged from a normal die, cooled and solidified by a cooling drum, and cast into a 30 μm cast film. I got The obtained film had a titanium oxide content of 33% by weight (A layer content of 40% by weight), an intrinsic viscosity [η] = 0.90, and a Young's modulus of the film of 255 kg / mm ² .

The cast film thus obtained was subjected to TFS (Tin Free Steel) in the same manner as in Example 1.
It was laminated with a board, but the film was not stretched and wrinkled during lamination, had good adhesiveness, and could be processed well. A cup (can) was formed by deep drawing using a drawing die and a punch, but a film having a good appearance was obtained without breakage of the film, cracks or pinholes. In addition, it has good white hiding properties,
The blackness of S was not recognized, and it had whiteness that did not require any supplementation of the hiding power by white printing.

Example 3 As a polyester (I) having a high concentration of 70% by weight of titanium oxide obtained in Example 1 and polyester (I), isophthalic acid 1
7.5 mol% copolymerized polyethylene terephthalate ([η] = 0.85, melting point 213 ° C.) in a weight ratio of 5: 9
To prepare a polymer composition (A) having a titanium oxide content of 25% by weight. Separately, as a polymer (C), isophthalic acid 5 mol% copolymerized polyethylene terephthalate ([η] = 0.90, melting point 240 ° C.,
(Diethylene glycol content: 0.9% by weight) was supplied to a separate extruder of a twin-screw vent type and melted, and then laminated into two layers (layer A / layer C = 9/1) using a feed block. After discharging from a normal die, the mixture was cooled and solidified by a cooling drum to obtain a cast film of 30 μm. The titanium oxide content of the film was 22.5% by weight (A layer content was 25% by weight), the intrinsic viscosity [η] was 0.80, and the Young's modulus of the film was 250 kg / mm ² .

The thus obtained film was treated with TF on the layer A side.
It was arranged so as to adhere to the S plate and laminated on both sides of the TFS plate. Thereafter, a cup (sideless seamless can) was formed by deep drawing using a drawing die and a punch.

The cast film thus obtained has very good laminating processability and adhesiveness, and is excellent in the moldability in can making and the impact resistance after can making in class A without any problem. The white hiding power was also good.

Comparative Example 1 A masterbatch was prepared in the same manner as in Example 1 except that polyethylene terephthalate having an intrinsic viscosity [η] of 0.8 was used as a base polymer for the masterbatch as polyester (II). The dispersibility was poor, and the intrinsic viscosity was greatly reduced due to hydrolysis of the polymer.
It was difficult to prepare a high concentration master of 0% by weight. Although the concentration was reduced to 50% by weight and mastering was performed, the dispersibility was still poor, and only those with [η] = 0.55 were obtained. Using such a master chip, polyester (I)
17.5 mol% of isophthalic acid copolymerized polyethylene terephthalate ([η] = 0.75, melting point: 213 ° C.)
Was blended at a weight ratio of 4: 1 to obtain a 30 μm cast film having the same titanium oxide content as in Example 1. [Η] = 0.50 of the obtained film, which was inferior in mechanical properties and was extremely brittle, and did not reach a film deserving of evaluation of adhesiveness, moldability and the like.

Comparative Example 2 As polyester (I), intrinsic viscosity [η] = 0.65
17.5 mol% of isophthalic acid copolymerized polyethylene terephthalate, polyester (II), polybutylene terephthalate with intrinsic viscosity [η] = 0.7, and titanium oxide (average particle diameter = 0.15 μm) as a white pigment. The mixture was melt-kneaded at a weight ratio of 14:61:25 to prepare a polymer composition (A) having a titanium oxide content of 25% by weight. On the other hand, separately from this, as a polymer (C), copolymerized polyethylene terephthalate of 5 mol% of isophthalic acid ([η] =
0.65, melting point 240 ° C., diethylene glycol content 1.5% by weight) were supplied to separate extruders of a twin-screw vent type and melted.
Layer / C layer = 9/1) and discharge from a normal die,
It was cooled and solidified by a cooling drum to obtain an unstretched film. Thereafter, the film was stretched and heat-set to obtain a biaxially oriented film. However, the film was frequently broken during stretching and was very difficult to stretch.

The titanium oxide content of the obtained film was 2
2.5 wt%, intrinsic viscosity [η] = 0.55, and Young's modulus of the film was 400 kg / mm ² .

The film thus obtained was placed on the A layer side with TF
Arranged so as to adhere to the S plate, and the TFS
Laminates were made on both sides of the plate, and then a cup was formed by deep drawing using a drawing die and a punch.

The film thus obtained was inferior in adhesiveness to that of Example 3, and had a moldability and impact resistance of class C, and had cracks in the film. Also, since the film had fine cracks on the outer surface, the appearance quality was poor and the white concealing property was not good.

[0059]

[Table 1]

[Table 2]

[0060]

The polyester film for laminating a metal sheet of the present invention is excellent in adhesiveness, moldability, impact resistance and white hiding property, and can be suitably used for a metal can produced by molding.

────────────────────────────────────────────────── (5) References JP-A-5-156040 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 C08L 67/00-67 / 02

Claims (5)

(57) [Claims] 1. A polyester (I) mainly composed of ethylene terephthalate and a polyester (II) mainly composed of butylene terephthalate in a weight ratio of 50:50 to 50:50.
90:10 and the colorant is 20-50
% By weight, Young's modulus of the film is 50-350kg
/ Mm ² , a white polyester film for metal plate lamination. 2. A polyester (I) mainly composed of ethylene terephthalate and a polyester (II) mainly composed of butylene terephthalate in a weight ratio of 50:50.
90:10 and the colorant is 20-50
The melting point of the film containing 150 wt.
A white polyester film for laminating a metal plate, wherein a layer composed of a polyester (III) mainly composed of ethylene terephthalate at a temperature of ° C. is laminated, and the Young's modulus of the film is 50 to 350 kg / mm ² . 3. The white polyester film for a metal plate laminate according to claim 1, wherein the intrinsic viscosity [η] is 0.65 or more. 4. The white color for a metal plate laminate according to claim 1, wherein the colorant is white inorganic particles selected from titanium oxide, zinc white, zinc sulfate, and lithopone. Polyester film. 5. A kneaded product composed of a polyester (II) mainly containing butylene terephthalate containing a high concentration of a coloring agent in advance by a masterbatch method, and thereafter the kneaded material and ethylene terephthalate are mainly used. By mixing and kneading with the polyester (I), the colorant is contained in an amount of 20 to 50% by weight, and the Young's modulus is 5%.
A method for producing a white polyester film for metal plate lamination, comprising obtaining a film of 0 to 350 kg / mm ² .