JP2003127307A - Laminated white polyester film for metal laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated white polyester film for metal laminate which is excellent in laminating properties, wear resistance and molding processability, and also has a beautiful surface after being bonded with metal plates, particularly an aluminum plate and molded, and is suitable for metal cans, particularly an aluminum can. SOLUTION: The polyester film is obtained by laminating a layer (B-layer) made of polyester 3 using ethylene terephthalate and/or butylene terephthalate as a main repeating unit on at least one surface of a polyester layer (A-layer) which is prepared by mixing 80 to 20 wt.% of polyester 1 using ethylene terephthalate of a melting point at 246 to 270 deg.C as a main repeating unit and 20 to 80 wt.% of polyester 2 using butylene terephthalate of a melting point at 180 to 240 deg.C as a main repeating unit. The film has 30 to 55 mmol/kg of COOH terminal group amount and the laminated white polyester film for metal laminate is prepared by mixing the A-layer and/or the B-layer with a white pigment.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a white laminated polyester film for metal laminating. More specifically, the present invention relates to a white laminated polyester film for metal lamination, which is suitable for being formed on a metal plate, particularly an aluminum plate, and then processed into a container for food or beverage.

[0002]

2. Description of the Related Art Conventionally, for the purpose of preventing corrosion, the inner and outer surfaces of a metal can are coated with various thermosetting resins such as epoxy-based or phenol-based resins dissolved or dispersed in a solvent to coat the metal surface. Was widely practiced. However, such a coating method using a thermosetting resin has a problem that it takes a long time to dry the coating material, productivity is reduced, and environmental pollution is caused by a large amount of organic solvent.

As a method for solving these problems, there is a method of laminating a film on an aluminum plate, a steel plate, or a metal plate which has been subjected to various surface treatments such as plating, which is a material for the metal can.

When a metal can is manufactured by drawing or ironing a laminated metal plate of a film, the film is required to have the following characteristics. (1) Excellent in laminating property on a metal plate. (2) Excellent adhesion to the metal plate. (3) It has excellent moldability and does not cause defects such as peeling, cracks and pinholes after molding. (4) The impact of the metal can does not cause the polyester film to peel off, crack, or pinhole. (5) Excellent hiding power, printability, and beauty. (6) It has excellent wear resistance and does not cause mold scraping during molding.

Many proposals have been made to solve these requirements. For example, JP-A-7-238176 discloses a film having a specific Young's modulus by blending polyethylene terephthalate with polybutylene terephthalate and adding a coloring agent. Also, Japanese Patent No. 31815
Japanese Patent No. 65 discloses a film in which polyethylene terephthalate is blended with polybutylene terephthalate and which has a specific melting point difference and specific crystallization characteristics.

However, none of the conventional methods can comprehensively satisfy the above-mentioned various required characteristics, and in particular, in a can manufactured through a step of amorphizing at a temperature at which a film melts and relaxing orientation, There was a problem that the excellent moldability and impact resistance could not be satisfied, and particularly when aluminum was used as the metal plate, the adhesion after lamination was insufficient and the film peeled off.

[0007]

The object of the present invention is to have excellent laminating properties, wear resistance, and moldability, and to be excellent in beauty after being bonded and processed with a metal plate, particularly an aluminum plate, Another object of the present invention is to provide a white laminated polyester film for metal laminating, which is suitable for metal cans, particularly aluminum cans.

[0008]

[Means for Solving the Problems] The above-mentioned problem is that the melting point is 24.
80 to 20% by weight of polyester 1 having 6 to 270 ° C. as a main repeating unit of ethylene terephthalate, and 20 to 80% by weight of polyester 2 having a melting point of 180 to 230 ° C. as a main repeating unit of polyester 2 A polyester film (B layer) comprising polyester 3 having ethylene terephthalate and / or butylene terephthalate as a main repeating unit, which is laminated on at least one side of the polyester layer (A layer). 30 to 55 mmo
1 / kg and can be achieved by mixing white pigments in layers A and / or B.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below along with preferred embodiments.

The polyester constituting the white laminated polyester film for metal laminating of the present invention is a general term for polymer compounds having an ester bond as a main bond in the main chain, and usually comprises a dicarboxylic acid component and a glycol component. It can be obtained by a condensation reaction. Here, as the dicarboxylic acid component, for example, terephthalic acid, 2,
Aromatic dicarboxylic acids such as 6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid and phthalic acid,
Aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, and fumaric acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and oxycarboxylic acids such as paraoxybenzoic acid. You can Examples of the glycol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and neopentyl glycol. Examples thereof include polyoxyalkylene glycols such as aliphatic glycol, diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, alicyclic glycols such as cyclohexanedimethanol, and aromatic glycols such as bisphenol A and bisphenol S. Among these, terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid and the like are preferably used as the acid component, and ethylene glycol, 1,3-butanediol, 1,4-butanediol and the like are preferably used as the glycol component. You can

The polyester 1 constituting the layer A of the polyester film of the present invention is required to contain ethylene terephthalate as a main repeating unit in view of productivity and heat resistance. Here, ethylene terephthalate is a condensate using terephthalic acid as a dicarboxylic acid component and ethylene glycol as a glycol component.

The main repeating unit means that the polyethylene terephthalate unit is more than 94 mol% and the dicarboxylic acid component other than terephthalic acid and ethylene glycol and the glycol component are less than 6 mol%. You may copolymerize in the range. Examples of the copolymerization component include the above-mentioned dicarboxylic acid component and glycol component, and, as long as they do not impair the effects of the present invention, copolymerize a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane. May be.

The polyester 1 of the present invention must have a melting point of 246 to 270 ° C. from the viewpoint of heat resistance and productivity. From the viewpoint of heat resistance, the melting point is 250 to 270.
It is more preferable that the temperature is ° C.

The polyester 2 constituting the layer A of the polyester film of the present invention is required to contain butylene terephthalate as a main repeating unit from the viewpoint of impact resistance.
Here, butylene terephthalate is a condensate using terephthalic acid as a dicarboxylic acid component and 1,4-butanediol as a glycol component.

Here, the main repeating unit specifically means that the polybutylene terephthalate unit is 7 units.
Terephthalic acid, 1,4
-A dicarboxylic acid component other than butanediol and a glycol component may be copolymerized as long as the effects of the present invention are not impaired. Examples of the copolymerization component include the above-mentioned dicarboxylic acid component and glycol component.

Polyester 2 is terephthalic acid and 1,4
It is preferably polybutylene terephthalate composed of butanediol.

The polyester 2 of the present invention must have a melting point of 180 to 240 ° C. from the viewpoint of heat resistance and productivity. From the viewpoint of heat resistance, the melting point is 185 to 236.
It is more preferable that the temperature is ° C.

From the viewpoints of productivity, laminating property, moldability and impact resistance, the polyester film of the present invention may be mixed with the above polyester 1 as 80 to 20% by weight and polyester 2 as 20 to 80% by weight. is necessary. When the mixing ratio of polyester 2 exceeds 80% by weight, the crystallinity becomes high, and the film-forming property, moldability, and spherulites are formed when the film is heat-treated to a non-oriented state after laminating the film, resulting in impact resistance. Getting worse. Further, even if the mixing ratio of the polyester 2 is less than 20% by weight, spherulites are similarly generated and the impact resistance is deteriorated. The mixing ratio of polyester 2 is more preferably 30 to 80% by weight, and further preferably the mixing ratio of polyester 2 is 40 to 80% by weight. Also,
A third component other than polyesters 1 and 2 may be mixed as long as the effect of the present invention is not impaired.

The method for mixing the polyester 1 and the polyester 2 is not particularly limited, but from the viewpoint of suppressing the progress of the transesterification reaction, the polyesters 1 and 2 mixed at a predetermined mixing ratio are supplied to the extruder. Then
A method in which the film of the present invention is obtained by melt-kneading and then directly undergoing extrusion, casting and stretching steps is preferably used.

The polyester 3 constituting the B layer of the polyester film of the present invention must contain ethylene terephthalate and / or butylene terephthalate as a main repeating unit in terms of affinity with the A layer.

The term "main repeating unit" means that the dicarboxylic acid component other than terephthalic acid, ethylene glycol and butanediol and the copolymerization component other than the glycol component are less than 40 mol%, more preferably. , Less than 30 mol%. Examples of the copolymerization component include the above-mentioned dicarboxylic acid component and glycol component.

The polyester used as the polyester 3 is preferably polyethylene terephthalate composed of terephthalic acid and ethylene glycol and / or polybutylene terephthalate composed of terephthalic acid and 1,4-butanediol.

The polyester film of the present invention must be a laminated film from the viewpoint of adhesiveness, impact resistance and abrasion resistance. As the laminated constitution, A / B two-layer laminated,
Examples thereof include A / B / A three-layer lamination and B / A / B three-layer lamination, but the B / A / B three-layer lamination is preferable from the viewpoint of impact resistance and abrasion resistance.

The polyester film of the present invention has heat resistance,
From the viewpoint of impact resistance, the amount of COOH end groups of the film is 30
It is necessary to be ~ 55 mmol / kg. More preferably 30-52 mmol / kg, 30-50
More preferably, it is mmol / kg. Film C
When the amount of the OOH terminal group is 55 mmol / kg or more, the moldability and the impact resistance are deteriorated due to hydrolysis or the like in the lamination, the heat treatment after the lamination and the molding.

The amount of COOH end groups of the film is set to 55 mmo.
There is no particular limitation on the method for controlling the amount to be less than 1 / kg, but for example, the amount of COOH terminal groups of polyesters 1, 2 and 3 is each within the above-mentioned preferable range, and the molecular weight is reduced during the film film melt extrusion, and transesterification is performed. Suppressing the reaction is the preferred method.

As a method for suppressing the molecular weight reduction and the transesterification reaction during melt extrusion, it is needless to say that the polyester is not exposed to an air atmosphere after drying, and is heated to 100 ° C. or higher and further under an inert atmosphere such as nitrogen or A method of supplying to the extruder from inside the hopper under vacuum is preferably used.

In the polyester film of the present invention, it is necessary to mix a white pigment in the A layer and / or the B layer from the viewpoints of hiding property, printability and beauty.

In the present invention, the amount of the white pigment added to the layer A is preferably 5 to 30% by weight, more preferably 10 to 28% by weight, and more preferably 15 to 30% by weight from the viewpoint of hiding properties. It is particularly preferably 25% by weight.

The amount of the white pigment added to the layer B is preferably less than 5% by weight, more preferably less than 3% by weight, and more preferably 1% by weight from the viewpoint of abrasion resistance and the like.
It is particularly preferable that it is less than.

In the polyester film of the present invention,
The amount of the white pigment added to the entire film is preferably 10 to 25% by weight from the viewpoint of hiding properties and the like, and 13 to 2 is preferable.
It is more preferably 5% by weight.

Examples of the white pigment to be added to the polyester film of the present invention include titanium oxide, calcium carbonate, alumina, zinc sulfide, white carbon and the like, but titanium oxide is preferable from the viewpoint of hiding power and beauty. . Particularly, from the viewpoint of hiding property, the average particle size of titanium oxide is preferably 0.1 to 0.3 μm, and 0.2
More preferably, it is ˜0.25 μm. Further, the titanium oxide particles may be subjected to various surface treatments from the viewpoint of suppressing aggregation in polyester and suppressing pinholes and coarse protrusions of the film, and in particular, organic alcohol treatment, alumina, and silica treatment may be performed. preferable.

From the viewpoints of moldability and productivity, the polyester film of the present invention preferably has an all-direction average value of transconformation orientation parameters obtained from infrared absorption spectrum of 0.5 to 3.0. 1.
It is more preferably 0 to 2.5 and even more preferably 1.0 to 2.0. If the orientation parameter is less than 0.5, spherulites may be formed in the laminate, resulting in embrittlement, and conversely, if it exceeds 3.0, the film formability may deteriorate. Here, the trans-conformation orientation parameter is the peak intensity at 1,340 cm ⁻¹ observed in the total reflection Fourier transform infrared absorption spectrum measurement of 1,
It is the value divided by the peak intensity at 408 cm ^-1 . The peak at 1,340 cm ^-1 is assigned to ωCH2 (trans band), and the peak at 1,408 cm ^-1 is assigned to the benzene ring.

The omnidirectional average value of the orientation parameter means the average value of the values obtained when the above measurement is performed using polarized light at 360 ° intervals of 30 ° with respect to the longitudinal direction of the film.

In polymerizing the polyester used in the present invention, conventionally known polymerization catalysts and anti-coloring agents can be used. These are not particularly limited, but as the polymerization catalyst, alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, etc. And a phosphorus compound or the like can be used as the anti-coloring agent.

Regarding the addition of the polymerization catalyst, antimony compound, germanium compound and /
Alternatively, it is preferable to add a titanium compound. As such a method, for example, when a germanium compound is taken as an example, a method of adding a germanium compound powder as it is, a method of adding a germanium compound by dissolving it in a glycol component which is a starting material of polyester, and the like are used. be able to.

Here, examples of the germanium compound include germanium dioxide, germanium hydroxide hydrate, germanium alkoxide compounds such as germanium tetramethoxide and germanium ethyleneglycoxide, germanium phenoxide compounds, germanium phosphate, germanium phosphite. Phosphoric acid-containing germanium compounds such as, germanium acetate and the like can be used.

As the antimony compound, for example, oxides such as antimony trioxide, antimony acetate and the like are used.

As the titanium compound, monobutyl titanate, dibutyl titanate and the like, and titanium tetraalkoxide such as titanium tetraethoxide and titanium tetrabutoxide are preferably used.

Among these, antimony trioxide is preferably used for polymerizing polyethylene terephthalate, and monobutyl titanate is preferably used for polymerizing polybutylene terephthalate.

For example, when germanium dioxide is added as a catalyst in the production of polyethylene terephthalate, a terephthalic acid component and an ethylene glycol component are transesterified or esterified, and then germanium dioxide and a phosphorus compound are added, A method for obtaining a germanium element-containing polymer by subsequently polycondensing at a high temperature and reduced pressure until a constant diethylene glycol content is obtained is preferably used. As a more preferable method, the obtained polymer is subjected to solid-phase polymerization reaction under a reduced pressure or in an inert gas atmosphere at a temperature below its melting point, to reduce the content of acetaldehyde, to give a predetermined intrinsic viscosity and a carboxy terminal group. The method of obtaining is used.

In the present invention, a lubricant may be added to the A layer and / or the B layer, if necessary. For example, calcium phosphate, kaolin, talc, zirconia, spinel, wet or dry silica, colloidal silica and the like. Inorganic particles, external particles such as acrylic acid-based polymers, and organic particles having polystyrene as a constituent component, so-called internal particles formed by deactivating catalysts added during the polyester polymerization reaction, and the like are preferable lubricants. To be

When inorganic particles, organic particles, etc. are added as the lubricant, the addition amount is preferably 0.05 to 30 parts by weight with respect to 100 parts by weight of the mixture of polyester 1 and polyester 2 or polyester 3. It is more preferably 0.1 to 3 parts by weight. The weight average particle diameter of the particles to be added is preferably 0.01 to 10 μm,
More preferably, it is 0.1 to 5 μm. A plurality of such particles having different types and particle sizes may be used in combination.

Next, a method for producing the polyester film of the present invention will be described.

The method for producing the laminated polyester film of the present invention from the polyester 1, polyester 2 and polyester 3 used in the present invention is not particularly limited, but for example, it can be produced by the following method.

That is, polyester 1, polyester 2 and polyester 3 are dried if necessary, then fed to a single-screw or twin-screw extruder, extruded in a sheet form from a slit die and extruded on a cast drum. To obtain an unstretched film.

The method for laminating the A layer and the B layer is not particularly limited. For example, the A layer made of polyester 1 and polyester 2 and the B layer made of polyester 3 are supplied to different extruders and melted. A method of extruding and laminating with a feed block installed on the die manifold portion or the upper portion of the die, or by separately preliminarily forming a film consisting of only an A layer made of polyester 1 and polyester 2 or a B layer made of polyester 3,
Examples thereof include a method of laminating by stacking on a heating roll, but from the viewpoint of productivity, a method of laminating in a feed block installed above the die is preferable.

Here, when the sheet is extruded onto the cast drum, the method of adhering the sheet to the cast drum includes electrostatic application method, adhering method utilizing surface tension of water or the like, air knife method, nip roll casting method. It is preferable to use any one of the above methods or a method in which two or more methods are combined. Among them, the electrostatic application method is preferable in terms of productivity.

Then, the unstretched film is stretched. The method for stretching the unstretched film is not particularly limited, but after stretching in the longitudinal direction, stretching in the width direction, or after stretching in the width direction, a sequential biaxial stretching method of stretching in the longitudinal direction, the longitudinal direction of the film, A simultaneous biaxial stretching method in which the width direction is stretched substantially simultaneously is preferably used.

In such a stretching method, the stretching ratio is preferably 1.6 to 4.2 times, more preferably 1.7 to 4.0 times in each direction.

The stretching speed is 1,000 to 200,000.
It is preferably 0% / min.

The stretching temperature is from the glass transition point of polyester to
The temperature range of (glass transition point + 100 ° C.) is preferable, more preferably 50 to 140 ° C., particularly preferably 60 to 125 ° C. in the longitudinal direction, and 50 in the width direction.
It is preferable to set the temperature to 130 ° C. Further, the stretching may be performed plural times in each direction.

Further, the film is subjected to a heat treatment after the biaxial stretching, and this heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature is preferably any temperature not lower than 100 ° C. and not higher than the melting point of polyester, and more preferably 100 to 250 ° C. from the viewpoint of moldability and impact resistance. If the temperature is lower than 100 ° C, impact resistance may deteriorate, and if the temperature exceeds 250 ° C, moldability may deteriorate. From the viewpoint of impact resistance after molding, it is more preferably 120 to 240 ° C,
The range of 150 to 240 ° C. is even more preferable. The heat treatment time may be any time as long as it does not deteriorate other properties, but it is usually preferably 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction.

The white laminated polyester film for metal laminating of the present invention is used as a film for metal laminating. The target metal is not particularly limited, and examples thereof include pure metals such as aluminum, iron, and titanium, as well as alloys such as steel, stainless steel, tinplate, and magnesium alloys. Aluminum plates, steel plates, and tin plates are more preferable, and even if they are used by laminating them on an aluminum plate, which has a poor adhesion in the case of conventional films, a sufficient adhesion can be obtained and can be preferably used.

The polyester film of the present invention can be suitably used for an outer surface coating of a metal container produced by drawing or ironing after it is attached to a metal plate. Further, good moldability and impact resistance can both be achieved even after a step of making the film substantially non-oriented by heat treatment before and after molding. Further, it can be preferably used as a film for the body, lid and bottom of a metal container which is not subjected to drawing or ironing, because it has good metal adhesion, moldability and impact resistance.

[0055]

The present invention will be described in detail below with reference to examples. The characteristics were measured and evaluated by the following methods.

(1) Intrinsic viscosity A polyester film was dissolved in orthochlorophenol and measured at 25 ° C.

(2) About 10 m of melting point polyester or polyester film
g Precisely weighed, differential scanning calorimeter (Perkin-Elmer D
(SC2 type), the temperature was raised at 20 ° C./min, and the melting point was determined from the peak position of the endothermic peak associated with melting.

(3) COOH end group amount The polyester film is dissolved in orthochlorophenol / chloroform (weight ratio 7/3) at 90 to 100 ° C. for 20 minutes, and the potential difference is titrated with an alkali to adjust the COOH end group amount. I asked.

(4) Residual amount of metallic element The total pigment concentration of titanium oxide and calcium carbonate in the film was determined by fluorescent X-ray measurement as the residual amount of metallic element. Note that the quantification was performed using a calibration curve of the intensity and each element content prepared using a sample of known metal content, which was previously quantified by the atomic absorption method or the like.

(5) The optical density of the film was measured with a masking optical densitometer (Macbeth TR-927) and evaluated according to the following criteria. ◯: 0.6 or more. X: less than 0.6.

(6) Orientation parameter The orientation parameter was measured by FT-IR. Set the film in the reflection ATR accessory device once, and set S polarization A
The TR spectrum was measured. The orientation distribution is 30, 60, 9 by rotating in 30 ° increments starting from the longitudinal direction of the film.
It was obtained by measuring the spectrum at 0, 120, and 150 °. Recognized from the obtained spectrum peak at 1342 cm ^-1 OmegaCH2 peak intensity of (trans band) 1410 cm the intensity of the peak attributed to ^-1 was oriented parameter performs normalization with. The main measurement conditions of FT-IR were as follows. Spectrometer: FTS-55A (BioRad DIGILA
B) Auxiliary device: 1-time reflection ATR auxiliary device Light source: Special ceramics Detector: MCT (HgCdTe) Resolution: 4 cm-1 Accumulation frequency: 256 times IRE: Ge Incident angle: 45 ° Polarizer: Wire grid, S-polarized light .

(7) An aluminum plate (thickness: 0.29 mm) and a film are superposed and inserted into a laminating press machine, and the film is inserted at 190 ° C. and 2.0 MPa for 10 minutes.
After pressing for 2 seconds, it was rapidly cooled in a water bath at 40 ° C. Then, the film-laminated aluminum plate is added to the film having a melting point of + 15 ° C. for a film having one melting point, and the melting point at the highest temperature +1 for films having two or more melting points.
After heat treatment at 5 ° C. for 120 seconds, it was rapidly cooled again in a water tank. Length 50 mm, width 1 from the laminated aluminum plate
A rectangular sample piece of 5 mm was cut out. A film having an edge of 10 mm of the sample piece was peeled from the aluminum plate, and then the peel strength was measured at a speed of 300 mm / min using a tensile tester. The average value after 10 measurements was evaluated according to the following criteria. Grades A and B were accepted. In the laminated film, the B layer side was used as the bonding surface to the steel plate. Class A: 0.6 kg / 15 mm or more Class B: 0.6 to 0.3 kg / 15 mm Class C: less than 0.3 kg / 15 mm.

(8) Abrasion resistance The above laminated aluminum plate was cut into 2 cm × 10 cm, and a single blade was pressed against the film surface with a force of 20 kg weight,
The surface was strongly squeezed and scraped, and the amount of change in the film weight before and after that was measured. The average value of the amount of change was determined for each sample with n = 10, and evaluated according to the criteria below. A grade: less than 5 mg B grade: 5 to 10 mg C grade: 10 mg or more.

(9) Formability After re-heat treatment of the above laminated sample at a melting point of + 15 ° C.,
Quenched again. Then, after heating with warm water of 90 ° C. for 30 minutes, it was cooled to 5 ° C. The laminated aluminum plate was bent at 360 degrees with the film surface as the outside, and the bent part was observed with an optical microscope at a magnification of 200 times, and evaluated according to the following criteria. Grades A and B were accepted. Grade A: No cracks or fractures are observed. Class B: Cracks with a width of less than 20 μm are recognized, but the aluminum plate is not exposed. Class C: Cracks and breaks with a width of 20 μm or more are recognized, and the aluminum plate is exposed.

Example 1 Polyethylene terephthalate having a melting point of 255 ° C. as the polyester 1 of the A layer, and a melting point of 234 ° C. as the polyester 2
Polybutylene terephthalate from Polyester 1
And polyester 2 at a ratio of 40:60,
Titanium oxide with a particle size of 0.22 μm was used as a white pigment.
Wt% was added. Isophthalic acid 17 mol% copolymerized polyethylene terephthalate was used as the polyester 3 in the B layer, and 0.05% by weight of silica having a particle diameter of 0.6 μm was added. The laminated structure was B / A / B. After vacuum-drying 1 + 2 and 3 respectively, melt-extrude with individual extruders, stack in a feed block installed on the upper part of the die, and apply static electricity on the metal roll cooled to 25 ° C from the die. Was discharged while performing the above to obtain an unstretched sheet.

Next, the unstretched sheet was heated to 80 ° C., stretched 3.2 times in the longitudinal direction, and stretched at 95 ° C. 3.2 times in the width direction in a tenter type stretching machine. Then, while applying 5% of relaxation in a tenter, heat treatment was performed at 210 ° C. for 10 seconds and then wound to obtain a biaxially stretched laminated polyester film (total thickness 16 μm). When this biaxially stretched laminated polyester film was evaluated, Table 1
It had the physical properties shown in 1. and had excellent properties.

Example 2 Polyethylene terephthalate having a melting point of 256 ° C. is used as the polyester 1 of the A layer, and a melting point of 235 is used as the polyester 2.
Polybutylene terephthalate (° C.) Was used, polyester 1 and polyester 2 were mixed at a ratio of 70:30, and 30% by weight of calcium carbonate having a particle diameter of 0.8 was used as a white pigment.
Add and add isophthalic acid 22 as polyester 3 in layer B
Example 1 was used except that a mixture of mol% copolymerized polyethylene terephthalate and polybutylene terephthalate was mixed at a ratio of 80:20, 0.1% by weight of silica having a particle diameter of 1 μm was added, and the laminated constitution was A / B. A film was obtained in the same manner as in. The resulting film had reduced wear resistance,
It had excellent laminating properties and moldability.

Example 3 Polyethylene terephthalate having a melting point of 254 ° C. was used as the polyester 1 in the A layer, and the melting point was 214 as the polyester 2.
Polyester 1 and polyester 2 are used by using polybutylene terephthalate copolymerized with 10 mol% of isophthalic acid at ℃.
After mixing at a ratio of 5:75, 33% by weight of titanium oxide having a particle diameter of 0.15 μm was added as a white pigment, and as the polyester 3 of layer B, 30 mol% of isophthalic acid copolymerized polybutylene terephthalate was added as a white pigment. A film was obtained in the same manner as in Example 1 except that 6% by weight of titanium oxide having a particle diameter of 0.15 μm was added. The resulting film had poor laminate properties, abrasion resistance, and moldability.

Example 4 Polyethylene terephthalate having a melting point of 255 ° C. is used as the polyester 1 of the A layer, and a melting point of 234 is used as the polyester 2.
Polybutylene terephthalate at ℃ was used to mix Polyester 1 and Polyester 2 in a ratio of 45:55, and 0.07% by weight of silica having a particle size of 0.6 μm was added. A film was obtained in the same manner as in Example 1 except that 20% by weight of titanium oxide having a particle diameter of 0.23 μm was added as a white pigment to mol% copolymerized polyethylene terephthalate, and the laminated constitution was changed to A / B. The resulting film had poor laminate properties, abrasion resistance, and moldability.

Example 5 Polyester 1 and polyester 2 were prepared by using 3 mol of isophthalic acid copolymerized polyethylene terephthalate having a melting point of 247 ° C. as polyester 1 of the A layer and 20 mol of isophthalic acid 20 mol copolymerized polybutylene terephthalate having a melting point of 193 ° C. In a ratio of 50:50, 33% by weight of titanium oxide having a particle diameter of 0.28 μm was added as a white pigment, and 17 mol% of isophthalic acid copolymerized polyethylene terephthalate was used as the polyester 3 in the B layer. A film was obtained in the same manner as in Example 1 except that 0.8% by weight of silica having a particle size of 0.04 μm was added. The obtained film had low moldability and abrasion resistance, but had excellent laminating property.

Comparative Example 1 Polyethylene terephthalate having a melting point of 256 ° C. was used as the polyester 1 of the A layer, and polyester 2 had a melting point of 234.
Polybutylene terephthalate at 0 ° C. was used to mix Polyester 1 and Polyester 2 at a ratio of 40:60, and then 35% by weight of titanium oxide having a particle size of 0.25 μm was added as a white pigment to give a laminated structure of a single film. A film was obtained in the same manner as in Example 1 except for the above. The film obtained had poor moldability, poor laminating properties and abrasion resistance.

Comparative Example 2 Polyester terephthalate of 12 mol% isophthalic acid having a melting point of 229 ° C. was used as polyester 1 of layer A, and polybutylene terephthalate having a melting point of 234 ° C. was used as polyester 2, and polyester 1 and polyester 2 were 8
After mixing at a ratio of 5:15, 10% by weight of calcium carbonate having a particle size of 0.6 μm was added as a white pigment, and 28 mol% of isophthalic acid as a polyester 3 in the B layer was added to the polybutylene terephthalate as particles of a white pigment. A film was obtained in the same manner as in Example 1 except that 15% by weight of calcium carbonate having a diameter of 0.6 μm was added. The obtained film had poor laminating properties and was inferior in hiding power, abrasion resistance and moldability.

Comparative Example 3 Polyethylene terephthalate having a melting point of 254 ° C. was used as the polyester 1 of the A layer, and polyester 172 was used as the polyester 2.
30% by mol of isophthalic acid copolymerized polybutylene terephthalate at 9 ° C.
After mixing at a ratio of 0:10, 4% by weight of titanium oxide having a particle size of 0.5 μm was added as a white pigment, and 10 mol% of isophthalic acid copolymerized polyethylene terephthalate was used as the polyester 3 in the B layer, and particles were added as a white pigment. Diameter 0.5
Add 5% by weight of titanium oxide of μm to make the laminated structure A / B
A film was obtained in the same manner as in Example 1 except that The obtained film had low abrasion resistance and was inferior in hiding property, laminating property and moldability.

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[Table 1]

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[Table 2] The abbreviations in the above table are as follows. PET: Polyethylene terephthalate PBT: Polybutylene terephthalate PET / I *: Isophthalic acid copolymerized polyethylene terephthalate (* indicates copolymerized mole%) PBT / I *: Isophthalic acid copolymerized polybutylene terephthalate (* indicates copolymerized mole%) Shown).

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EFFECT OF THE INVENTION It is possible to provide a white laminated polyester film for metal laminating, which is suitable for being formed on a container such as food or beverage after being laminated on a metal plate and used.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4F100 AA20 AB10D AK42A AK42B                       AK42C AK42J AL01B AL01C                       AL05A BA02 BA03 BA04                       BA06 BA07 BA10B BA10C                       BA10D BA16 BA27 CA13A                       CA13B CA13C DA01 DE01A                       DE01B DE01C EH20 EJ38                       GB16 GB23 HB00 JA04A                       JA20 JK09 JL01 YY00 YY00A                       YY00B YY00C

Claims (7)

[Claims] 1. A polyester 1 containing ethylene terephthalate having a melting point of 246 to 270 ° C. as a main repeating unit is 80 to 20% by weight, and a polyester 2 containing a butylene terephthalate having a melting point of 180 to 240 ° C. as a main repeating unit is 20. A polyester layer (A
A polyester film in which a layer (layer B) made of polyester 3 having ethylene terephthalate and / or butylene terephthalate as a main repeating unit is laminated on at least one side of the layer), and the COOH terminal group amount of the film is 30 to 55 mmol. / Kg, and a white pigment is mixed in the A layer and / or the B layer, a white laminated polyester film for metal laminating. 2. The white laminated polyester film for metal laminating according to claim 1, wherein the amount of the white pigment added to the polyester film is 5 to 30 wt% in the A layer and less than 5 wt% in the B layer. . 3. An IR-based orientation parameter average value in all directions of the polyester film is 0.5 to 3.0 in the transformer portion.
A white laminated polyester film for metal laminating according to any one of 1. 4. The white laminated polyester film for metal laminating according to claim 1, wherein the laminated constitution of the polyester film is a B / A / B three-layer laminated structure. 5. The white laminated polyester film for metal laminating according to claim 1, wherein the amount of the white pigment added to the polyester film is 10 to 25 wt% of the entire film. 6. The white laminated polyester for metal laminating according to claim 1, wherein the white pigment of the polyester film is titanium oxide particles having an average particle size of 0.1 to 0.3 μm. the film. 7. The white laminated polyester film for metal lamination according to claim 1, wherein the polyester film is a white laminated polyester film for aluminum plate lamination.