JPH0970934A - Laminated polyester film for laminating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biaxially oriented laminated film for laminating a metal plate adapted to a metal can have excellent moldability and taste characteristics by specifying the metal element amounts of metal compounds contained in layers A and B of a polyester film having the layer B laminated on the one surface of the layer A. SOLUTION: The layers A and B of a polyester film having the layer B laminated on at least one surface of the layer A each contains a metal compound arbitrarily selected from antimony compounds, germanium compounds and titanium compounds. The metal element amount of the metal compound in the layer A is less than 80ppm, and the metal element of the metal compound in the layer B is 80 to less than 1000ppm. The catalyst metal amount in the layer A is reduced to obtain the film having excellent taste characteristics with reduced generation of a low-molecular-weight compound even if it receives a heat history. The catalyst metal amount in the layer B is increased to obtain a film having small thickness irregularity and excellent moldability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated polyester film for laminating. More specifically, the present invention relates to a laminated film for metal plate lamination, which has excellent moldability, impact resistance, and taste characteristics and is suitable for a metal can manufactured by a molding process.

[0002]

2. Description of the Related Art Conventionally, the inner and outer surfaces of metal cans are coated with various thermosetting resins, such as epoxy and phenol, dissolved or dispersed in a solvent for the purpose of preventing 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.

As a method of solving these problems, there is a method of laminating a film on a steel plate, an aluminum plate, or a metal plate which has been subjected to various surface treatments such as plating on the metal plate, 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 adhesion to a metal plate. (2) It has excellent moldability and does not cause defects such as pinholes after molding. (3) The polyester film should not be peeled off, nor should cracks or pinholes be generated by the impact on the metal can. (4) The scent component of the contents of the can is adsorbed on the film,
The flavor of the contents should not be impaired by the odor of the film (hereinafter referred to as taste characteristics).

Many proposals have been made in order to solve these requirements. For example, Japanese Patent Application Laid-Open No. 64-22530 discloses a polyester film having a specific density and surface orientation coefficient, and Japanese Patent Application Laid-Open No. 2-57339. Discloses a copolyester film having a specific crystallinity. However, these proposals are not ones that can comprehensively satisfy the various required characteristics as described above, and can be said to be at a sufficiently satisfactory level particularly in applications where high moldability and excellent taste characteristics are required. There wasn't.

[0006]

The object of the present invention is to eliminate the above-mentioned problems of the prior art, and is excellent in moldability, heat resistance and taste characteristics, and particularly excellent in taste characteristics produced by molding. Another object of the present invention is to provide a biaxially stretched laminated film for laminating a metal plate suitable for a metal can.

[0007]

The above-mentioned object of the present invention is to provide a polyester film obtained by laminating a B layer on at least one side of an A layer, wherein the A layer and the B layer are made of an antimony compound, a germanium compound and a titanium compound, respectively. Containing at least one metal compound selected from the group consisting of
And the amount of the metal element of the metal compound in the B layer is 80 or less.
It can be achieved by a laminated polyester film for laminating characterized by being in the range of from ppm to less than 1000 ppm.

As a result of intensive studies, the present invention focuses on a specific polymerization catalyst and reduces the amount of catalytic metal in the A layer to
It has been found that a film with good taste characteristics can be obtained with less generation of low molecular weight substances even when subjected to a heat history, and by increasing the amount of the catalytic metal in the B layer, a film with less thickness unevenness and excellent moldability can be obtained. It is a thing.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention is a polymer composed of a dicarboxylic acid component and a glycol component, and examples of the dicarboxylic acid component include terephthalic acid, ishiphthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and diphenyl. Aromatic dicarboxylic acids such as sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer
Acids, maleic acid, aliphatic dicarboxylic acids such as fumaric acid, alicyclic dicarboxylic acids such as cyclohexyne dicarboxylic acid, p
And oxycarboxylic acids such as oxybenzoic acid. Among these dicarboxylic acid components,
Terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like are preferable from the viewpoint of heat resistance. On the other hand, examples of the glycol component include ethylene glycol and propanediol.
Aliphatic glycols such as diol, butanediol, pentanediol, hexanediol and neopentyl glycol,
Examples thereof include alicyclic glycols such as cyclohexane dimethanol and aromatic glycols such as bisphenol A and bisphenol S. Among them, ethylene glycol and butanediol are preferable among these glycol components. Incidentally, two or more of these dicarboxylic acid components and glycol components may be used in combination.

Further, a polyfunctional compound such as trimellitic acid, trimesic acid and trimethylolpropane may be copolymerized with the copolyester as long as the effects of the present invention are not impaired.

In the present invention, in terms of heat resistance and taste characteristics,
It is necessary that the metal element content of the metal compound arbitrarily selected from the antimony compound, the germanium compound and the titanium compound in the layer A is less than 80 ppm. It is preferably 0.01 ppm or more and less than 70 ppm, and particularly preferably 0.1 ppm or more and less than 60 ppm. Preferably,
It is preferable that the layer A mainly contains a germanium compound because the taste characteristics after being subjected to a high temperature heat history such as drying and retort treatment in a can-making process become good.

Also, the amount of the metal element in the B layer is 80 ppm.
It is necessary to be less than 1000 ppm in order to reduce thickness unevenness when forming the polyester film. The amount of the metal element in the B layer is preferably 100 ppm or more and less than 800 ppm, particularly preferably 100 ppm or more and less than 500 ppm. Furthermore, it is preferable that the B layer mainly contains an antimony compound because the amount of diethylene glycol produced as a by-product can be reduced and the heat resistance can be improved.

The method of incorporating the antimony compound, germanium compound or titanium compound of the present invention into a polyester may be any conventionally known method and is not particularly limited, but it is usually an arbitrary step before the production of the polyester is completed. In the above, it is preferable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst. 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, or Japanese Patent Publication No.
As described in JP-A-4-22234, a method of dissolving and adding a germanium compound in a glycol component which is a starting material of polyester can be mentioned. As the germanium compound, for example, germanium dioxide, germanium hydroxide containing crystal water, or germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethylene glycoloxide, germanium phenolate, germanium β- Examples include germanium phenoxide compounds such as naphtholate, phosphorus-containing germanium compounds such as germanium phosphate and germanium phosphite, and germanium acetate. Among them, germanium dioxide is preferable. Examples of the antimony compound include, but are not particularly limited to, antimony oxides such as antimony trioxide, and antimony acetate. The titanium compound is not particularly limited, but an alkyl titanate compound such as tetraethyl titanate and tetrabutyl titanate is preferably used.

The polyester in the present invention preferably has an amount of diethylene glycol component of 0.01 to 1.5% by weight, more preferably 0.01 to 1.0% by weight, and particularly preferably 0.01 to 0.8% by weight. It is desirable to maintain good impact resistance even when subjected to a lot of heat history such as heat treatment in the can making process and retort treatment after can making. This is considered to improve the resistance to oxidative decomposition at 200 ° C. or higher.
To 1% by weight.

In order to improve the taste characteristics, the content of acetaldehyde in the film is preferably 30 ppm.
The following is more preferable, 25 ppm or less is more preferable, and 20 ppm or less is particularly preferable. If the content of acetaldehyde exceeds 30 ppm, the taste characteristics are poor. The method of controlling the content of acetaldehyde in the film to 30 pm or less is not particularly limited, but for example, in order to remove acetaldehyde generated by thermal decomposition when the polyester is produced by a polycondensation reaction or the like, the polyester is reduced in pressure or Heat treatment at a temperature below the melting point of polyester in an inert gas atmosphere, preferably at 150 ° C. under reduced pressure or in an inert gas atmosphere
As described above, a method of solid-phase polymerization at a temperature below the melting point, a method of melt extruding using a vent-type extruder, an extrusion temperature at the time of melt extruding a polymer, the melting point of the high melting point polymer side + 30 ° C or less,
A method of extruding at a melting point of + 25 ° C. or less for a short time, preferably for an average residence time of 1 hour or less, can be mentioned.

The polyester of the layer A in the present invention preferably has a melting point of 240 ° C. or higher from the viewpoint of taste characteristics.
More preferably 246 ° C or higher, particularly preferably 250
℃ or above. As the polyester, polyester mainly composed of polyester ethylene terephthalate and / or ethylene isophthalate is preferable, and 80 mol% or more of repeating units are ethylene terephthalate and / or ethylene isophthalate, more preferably 85 mol% or more. Is desirable.

The polyester for the layer B of the present invention is not particularly limited, but a melting point of 160 to 280 ° C. is preferable in order to improve heat resistance and adhesion to a metal plate, and more preferably 180 to 260. ℃. Other resins may be blended and copolymerized to improve impact resistance. Above all, it is preferable that the butanediol residue is contained in an amount of 5 to 60 mol% with respect to the total glycol residue, because the impact resistance becomes good.

It is desirable that the ratio rA / rB of the melting specific resistance (rA) of the A layer and the melting specific resistance (rB) of the B layer is 2 to 200 in order to improve the thickness unevenness. The method for controlling the melting specific resistance is not particularly limited, but known methods for limiting the amounts of alkali metal compounds, alkaline earth metal compounds, phosphorus compounds and the like can be used in combination.

In order to improve impact resistance and taste characteristics in the present invention, the intrinsic viscosity of the polyester is preferably 0.5 or more and 1.0 or less, more preferably 0.6 or more and 1 or less. It is considered that when the intrinsic viscosity is 0.0 or less, particularly preferably 0.7 or more and 1.0 or less, the entanglement density of polymer molecular chains increases, but impact resistance and taste characteristics can be further improved, which is preferable. .

The polyester of the present invention can be produced by any conventionally known method and is not particularly limited. For example, a case where an isophthalic acid component is copolymerized with polyethylene terephthalate and germanium dioxide is added as a germanium compound will be described. A terephthalic acid component, an isophthalic acid component and an ethylene glycol are transesterified or esterified, then germanium dioxide and a phosphorus compound are added, followed by polycondensation reaction at a high temperature and a reduced pressure until a constant diethylene glycol content is obtained, A polymer containing germanium element is obtained.
Then, the obtained polymer is subjected to solid-phase polymerization reaction at a temperature below its melting point under reduced pressure or under an inert gas atmosphere,
Examples thereof include a method of reducing the content of acetoaldehyde and obtaining a predetermined intrinsic viscosity and a carboxyl terminal group.

In producing the polyester of the present invention,
Conventionally known reaction catalysts and coloring inhibitors can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, and titanium. Examples of the coloring inhibitor such as a compound include a phosphorus compound.

The thickness of the biaxially stretched film of the present invention is preferably from 5 to 60 μm, more preferably from the viewpoint of moldability after being laminated on a metal, film formability with respect to the metal, impact resistance and taste characteristics. Is 10 to 40 μm. As the laminated thickness, it is preferable that the thickness of the layer A is 0.01 to 5 μm in terms of taste characteristics and moldability, and more preferably,
The thickness is 0.1 to 3 μm, particularly preferably 0.5 to 2 μm. The thickness of the B layer is preferably 4 to 60 μm, more preferably 8 to 30 μm.

The thickness of the layer A is 0.1 μm or more and 25 μm or more.
m or less is preferable, and when the B layer is modified from the viewpoint of impact resistance, it is 1 μm or more and 15 μm or more in order to achieve both taste characteristics and impact resistance.
μm or less is preferable, more preferably 2 μm or more and 10 μm
m or less.

Further, in order to improve the handleability and processability of the film of the present invention, any of known external particles having an average particle diameter of 0.1 to 10 μm, external particles such as inorganic particles and / or organic particles can be used. The particles selected for A layer and / or
Alternatively, the layer B preferably contains 0.01 to 10% by weight, and further contains 0.01 to 3 of internal particles having an average particle diameter of 0.1 to 5 μm, inorganic particles and / or organic particles.
It is preferably contained in a weight percentage. As a method for depositing the internal particles, a known technique can be adopted. For example, JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, and JP-A-54-90.
No. 397, for example. JP-A-55-20496, JP-A-59-20461
It can also be used in combination with other particles such as JP-A-7.
It is not preferable to use particles having an average particle diameter of more than 10 μm because defects in the film are likely to occur. Examples of the inorganic particles and / or organic particles include wet and dry silica, colloidal silica, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay and the like inorganic particles and styrene, silicone, Examples thereof include organic particles having acrylic acid as a constituent component. Among them, inorganic particles such as wet and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituents can be exemplified. These internal particles, inorganic particles and / or organic particles may be used in combination of two or more kinds.

The particles may be added to either the A layer or the B layer, but the center line average roughness Ra of the B layer is preferably 0.005.
To 0.08 μm, more preferably 0.008 to 0.0
It is 6 μm. Furthermore, the ratio Rt / Ra with the maximum roughness Rt
Is 5 to 50, preferably 8 to 40, whereby the high-speed can making property is improved. The center line average roughness Ra of the layer A is preferably 0.001 to 0.05 μm, more preferably 0.0.
The range of 02 to 0.04 μm is preferable because the taste characteristics are improved.

The method for producing the laminated film in the present invention is not particularly limited, but, for example, after drying each polyester as required, each polyester is supplied to a known extruder for melt lamination, and a sheet die is formed from a slit die. Then, the unstretched sheet is obtained by extruding and then closely adhering to a casting drum by a method such as electrostatic application to cool and solidify. In applications where the degree of molding is large, the unstretched film may be subjected to surface treatment such as corona discharge treatment, if necessary, and then slit and wound to obtain a film. On the other hand, it is preferable to use a film obtained by further biaxially stretching an unstretched film as described below, using a Tain-free steel (hereinafter referred to as TFS) steel plate, which will be described later, in applications where the degree of forming is rather low. In terms of As a method for obtaining a biaxially stretched film, an unstretched sheet obtained by bringing the film into close contact with the casting drum and solidifying by cooling is stretched in the longitudinal direction and the width direction of the film. The draw ratio can be arbitrarily set depending on the orientation of the target film, the strength, the elastic modulus, etc., but preferably by the tenter method in terms of the quality of the film, after stretching in the longitudinal direction, A sequential biaxial stretching method of stretching in the width direction and a simultaneous biaxial stretching method of stretching in the longitudinal direction and the width direction at the same time are desirable. The draw ratio is 1.5 to 4.
It is 0 times, preferably 1.8 to 4.0 times. Longitudinal direction,
Either of the stretching ratios in the width direction may be increased or the stretching ratio may be the same. The stretching speed is 1000% / min to 200.
The stretching temperature is preferably 000% / min, and the stretching temperature may be any temperature as long as it is equal to or higher than the glass transition temperature of polyester B and equal to or lower than the glass transition temperature of thermoplastic resin A + 20 ° C., but usually 80 to 190. C is preferred. Further, the film is subjected to a heat treatment after 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 can be any temperature of 120 ° C. or higher and 245 ° C. or lower, but is preferably 120 to 240 ° C. The heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in its longitudinal direction and / or width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

In the present invention, the heat shrinkage ratio at 150 ° C. × 30 minutes is preferably 5% or less. When the heat shrinkage rate is 5% or less, preferably 4% or less, more preferably 3% or less, not only the heat laminating property with a metal is excellent, but also the impact resistance is improved.

Further, in producing the film of the present invention, if necessary, additives such as an antioxidant, a plasticizer, an antistatic agent, a weathering agent and a terminal blocking agent can be appropriately used. In particular, the combined use of an antioxidant is preferable because it prevents the polyester B from deteriorating due to heat history in the can making process. The amount is preferably about 0.001 to 1% by weight based on the total weight of the film.

Further, it is preferable to improve the adhesion by subjecting the B layer to a surface treatment such as a corona discharge treatment in order to further improve the characteristics. At that time, E value is 5
-40, preferably 10-35.

Although the metal plate of the present invention is not particularly limited,
From the viewpoint of formability, a metal plate made of iron, aluminum, or the like is preferable. 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 A chemical conversion treatment coating layer represented by, for example, a chromate treatment or a chromium chromate treatment may be provided. In particular, in terms of chromium metal, 6.5 to chrome
A chromium hydrated oxide of 150 mg / m ² is preferable, and a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gunmetal, brass, etc. may be provided. For tin plating 0.5-15 / m ^2, it is preferable to have a plating amount when nickel or aluminum 1.8~20g / m ^2.

The metal laminating film of the present invention can be suitably used for coating the inner surface of a two-piece metal can produced by drawing or ironing. Also,
The lid of a two-piece can, or the barrel of a three-piece can,
It can be preferably used as a material for covering the lid and the bottom because it has good metal adhesion and moldability.

[0032]

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

(1) Content of diethylene glycol component in polyester It was measured by NMR (13 C-NMR spectrum).

(2) Content of Metal Element in Polyester The content of the element in the polyester composition and the peak intensity were quantified by fluorescent X-ray measurement.

(3) Intrinsic viscosity of polyester Dissolve the polyester in orthochlorophenol and prepare 25
Measured in ° C.

(4) Melting point of polyester Crystallized polyester was subjected to a differential scanning calorimeter (DSC-2 type manufactured by Perkin Elmer Co., Ltd.) at 10 ° C./min.
The temperature was measured at a rate of temperature rise.

(5) Content of acetaldehyde in the film 2 g of fine powder of the film was sampled and charged into a pressure resistant container together with ion-exchanged water, extracted with water at 120 ° C. for 60 minutes, and then quantified by high sensitivity gas chromatography.

(6) Average particle size of particles The resin is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are selected so that the resin is incinerated but the particles are not damaged. The number of the particles was observed at 5,000 to 10,000 using a scanning electron microscope, and the particle image was obtained from the equivalent circle diameter by an image processing apparatus.

When the particles are internal particles, a polymer cross section is cut to prepare an ultrathin section having a thickness of about 0.1 to 1 μm, and a photograph (10 sheets: 10: (25 cm × 25 cm) was photographed, and the average dispersion diameter of internal particles was calculated from the equivalent circle diameter.

(7) Heat Shrinkage A film sample having a width of 10 mm and a length of 250 to 300 mm is marked at intervals of 200 mm, fixed on a sample support plate under a constant tension, and a universal projector (V16 manufactured by Nippon Kogaku) is used.
The original length of the marking interval was measured using A). Apply a load to the measured sample using a 3g clip,
It processed in the hot air oven set to 0 degreeC, rotating for 30 minutes. The treated sample was allowed to stand for 2 hours in the atmosphere in which the original length was measured, and then the marking interval was measured in the same manner as in the original length measurement method to determine the shrinkage.

(8) Melt Specific Resistance Using the melt specific resistance measuring device shown in FIG. 1, the polyester chips used in each layer were melt-stored at 280 ° C. in a nitrogen gas atmosphere, and a melt ratio when 3 kV voltage was applied. The resistance was measured.

(9) Surface Roughness of Film (Centerline Average Roughness Ra, Maximum Roughness Rt) The surface roughness was measured using a high precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions are as follows, and the average value of 20 measurements was taken as the value.

-Tactile stylus tip radius: 0.5 μm-Stylus load: 5 mg-Measurement length: 1 mm-Cutoff value: 0.08 mm Note that Ra and Rt are defined, for example, by Jiro Nara, "Surface roughness". Measurement / Evaluation Method "(General Technology Center, 1983)
Is shown.

(10) Surface Orientation Coefficient A sodium D ray (wavelength 589 nm) was used as a light source and an Abbe refractometer was used. The plane orientation coefficient fn = (Nx + Ny) / 2-Nz obtained from the refractive indices (Nx, Ny, Nz) in the longitudinal direction, the width direction, and the thickness direction was calculated.

(11) Thickness unevenness Thickness unevenness in the longitudinal direction of the film center of 2 m was measured with an electronic micrometer to find the difference between the maximum value and the minimum value, and the average value after measuring 10 m in total was taken as the thickness unevenness R (μm). did.

(12) Formability A film and a TFS steel plate (thickness: 0.3 mm) heated to 140 to 250 ° C. at 50 m / min are laminated so that the B layer serves as an adhesive surface, followed by rapid cooling, and then a draw forming machine. (Molding ratio (maximum thickness / minimum thickness) = 1.5, and 2.0) 80 to 1
A can molded in the moldable temperature range at 00 ° C was obtained.
A 1% saline solution was placed in the obtained can, and a voltage of 6 v was applied to the electrode in the saline solution and a metal can to read a current value after 3 seconds and obtain an average value after 10 cans were measured.

Class A: less than 0.001 mA Class B: 0.001 mA or more and less than 0.01 mA Class C: 0.01 mA or more and less than 0.1 mA Class D: 0.1 mA or more

(13) Taste characteristics (a) Polyester A layer is a perfume aqueous solution (d-limonene 3)
(Contact area: 5)
00 cm ² ) After left at 35 ° C. for 14 days, the components that are heated and expelled by heating the glass transition temperature of the thermoplastic resin A at + 5 ° C. for 30 minutes in a nitrogen stream are used to measure the adsorbed amount of d-limonene per 1 g of the film by gas chromatography. It was quantified and taste characteristics were evaluated.

(B) In addition, a can (diameter 6 cm, height 12 c
m) was subjected to pressurized steam treatment at 120 ° C. for 30 minutes, 350 ml of a 20 ppm aqueous d-limonene perfume solution was charged, and the mixture was sealed at 35 ° C. and left for 1 month. Was evaluated according to the following criteria.

Grade A: No change in odor was observed. Class B: Almost no change in odor. Class B: Some change in odor is seen. Class C: A large change in odor is seen.

Example 1 An ethylene glycol slurry containing colloidal silica particles having different average particle diameters as the polyester of the layer A was heat-treated at 190 ° C. for 2 hours, and after completion of the esterification reaction, the slurry was added to carry out a polycondensation reaction. Isophthalic acid 12.0 mol% copolymerized polyethylene terephthalate containing the particles in a predetermined amount (germanium element amount 40 ppm, intrinsic viscosity 0.69, diethylene glycol 0.80 wt%, melting point 229 ° C., carboxyl end group: 42 equivalents / ton) Chips were manufactured. After heat-treating ethylene glycol slurries containing colloidal silica particles having different average particle diameters as the polyester for the layer B at 190 ° C. for 2 hours, the slurry is added after completion of the esterification reaction and polycondensation reaction is performed to contain the particles in a predetermined amount. Isophthalic acid 12.
Chips of 0 mol% copolymerized polyethylene terephthalate (antimony element amount 300 ppm, intrinsic viscosity 0.68, diethylene glycol 0.70 wt%, melting point 229 ° C., carboxyl end group: 41 equivalent / ton) were produced. Each polyester was vacuum dried at 170 ° C. for 4 hours and supplied to a single-screw extruder, and then two layers (A layer / A layer /
(Layer B = 1/4), the mixture was discharged from a normal die, and then electrostatically applied (7 kv) to cool and solidify with a mirror-cooling drum so that Layer B would be the drum surface to obtain an unstretched film ( Drum rotation speed 30 m / min). This unstretched film is heated to a temperature of 98
After stretching 3.0 times in the longitudinal direction at ℃, and stretching 3.0 times in the width direction at 115 ℃, relax at 187 ℃.
% For 5 seconds. The obtained film characteristics and can characteristics are as shown in Table 1, and good moldability and taste characteristics were obtained.

Examples 2 to 6 Films were obtained in the same manner as in Example 1 except that the production of polyester, the film forming method, the lamination ratio, the type of polyester, etc. were changed. The results are shown in Tables 1 and 2.

In Example 2, dry silica particles having an average particle diameter of 0.3 μm and internal particles were used as a catalyst, and a transesterification reaction was carried out by a conventional method using 64 parts of a glycol component and 0.1 part of calcium acetate as a catalyst to 100 parts of an acid component. 12.0 mol of isophthalic acid containing internal particles obtained by polycondensation by adding 0.17 part of lithium acetate, 0.15 part of trimethyl phosphate, 0.02 part of phosphorous acid and 0.03 part of antimony trioxide. % Copolymerized polyethylene terephthalate is blended with 12.0 mol% of particle-free isophthalic acid copolymerized polyethylene terephthalate to form polyester B, the lamination ratio is A layer / B layer = 1/24, and the longitudinal stretching temperature is 10.
A film was obtained in the same manner as in Example 1 except that the temperature was 0 ° C. and the transverse stretching temperature was 115 ° C. The obtained film characteristics and can characteristics are as shown in Table 1, and good moldability and taste characteristics were obtained.

In Example 3, ethylene glycol slurries containing colloidal silica particles having different average particle diameters as the polyester for layer B were heat-treated at 190 ° C. for 2 hours, and then transesterified with 0.1% by weight of tetrabutyl titanate as a catalyst. After completion of the reaction, a slurry is added to carry out a polycondensation reaction to obtain 3.0 mol% of isophthalic acid as an acid component containing a predetermined amount of the particles and 25 mol% of butanediol as a glycol component Copolymerized polyethylene terephthalate (amount of titanium element 190 ppm, specific Chips having a viscosity of 0.78, 0.50% by weight of diethylene glycol, a melting point of 190 ° C., and a carboxyl end group of 41 equivalent / ton were produced. Each polyester was vacuum dried at 140 ° C. for 6 hours and supplied to a single-screw extruder, and then two layers (A layer / A layer /
After being laminated in a B layer = 1/4) and discharged from a normal die, an unstretched film was obtained by cooling and solidifying with a mirror cooling drum so that the B layer became the drum surface by electrostatic application (7 kv). The unstretched film was stretched 3.1 times in the longitudinal direction at a temperature of 95 ° C. and 3.1 times in the width direction at a temperature of 113 ° C.
Heat treatment was carried out at 7 ° C. for 5 seconds for relaxation for 5%. The obtained film characteristics and can characteristics are as shown in Table 1, and good moldability and taste characteristics were obtained.

In Example 4, when the amount of Ti element in the B layer in Example 3 was set to 90 ppm, the unevenness in thickness was slightly deteriorated and the formability was slightly lowered.

In Example 5, when the amount of Ge element in the A layer of Example 1 was set to 75 ppm, the thickness unevenness was improved, but
The taste characteristics were slightly degraded.

In Example 6, the polyester of the layer A was polyethylene terephthalate and the polyester of the layer B was 5 mol% of isophthalic acid copolymerized polyethylene terephthalate in Example 1, and the longitudinal stretching temperature was 103 ° C. and the stretching ratio was both longitudinal and transverse. A film was obtained in the same manner as in Example 1 except that the amount was 3.3 times. The resulting film had particularly good taste characteristics.

In Comparative Example 1, the metal catalyst of the polyester of the layer A was antimony trioxide, and the metal catalyst element content was 2
A film was obtained in the same manner as in Example 1 except that the amount was set to 00 ppm. The obtained film had significantly deteriorated taste characteristics.

In Comparative Example 2, antimony trioxide was used as the metal catalyst in both layers A and B, and the antimony element content was 20 p.
A film was obtained in the same manner as in Example 1 except that pm was used. The resulting film had uneven thickness and greatly reduced moldability.

In Comparative Example 3, the metal catalyst of the polyester of the layer A was antimony trioxide, and the metal catalyst element content was 2
When the content of the metal catalyst of the B layer polyester was set to 00 ppm, the metal catalyst was set to antimony trioxide, and the content of the metal catalyst element was set to 20 ppm, the taste property of the obtained film was significantly deteriorated.

[0061]

[Table 1]

[Table 2]

[Table 3] The abbreviations in the table are as follows.

PET / I: Polyethylene terephthalate copolymerized with isophthalic acid (numerals are copolymerized mol%) P (E / B) / (T / I): Polyethylene terephthalate copolymerized with isophthalic acid and butanediol DEG: Diethylene glycol

[0063]

INDUSTRIAL APPLICABILITY The laminated polyester film for metal plate laminating of the present invention has not only excellent moldability in molding into a can and the like, but also excellent taste characteristics. It can be suitably used for cans.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus for measuring the specific resistance of polyester when molten.

[Explanation of symbols]

 1: DC high voltage generator 2: Ammeter 3: Voltmeter 4: Heating body 5: Polyester for measurement 6: Electrode 7: Container

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Claims (4)

[Claims] 1. A polyester film obtained by laminating a B layer on at least one side of an A layer, wherein the A layer and the B layer are at least one metal compound selected from the group consisting of antimony compounds, germanium compounds and titanium compounds, respectively. And a metal element amount of the metal compound in the A layer is less than 80 ppm, and a metal element amount of the metal compound in the B layer is 80 ppm or more and less than 1000 ppm. 2. The laminated polyester film for laminating according to claim 1, wherein the layer A mainly contains a germanium compound and the layer B mainly contains an antimony compound or a titanium compound. 3. The laminated polyester film for laminating according to claim 1, wherein the butanediol residue is contained in the layer B in an amount of 5 to 60 mol% based on all glycol residues. 4. The laminated polyester film for laminating according to claim 1, wherein the melting point of the layer A is 240 ° C. or higher.