JP2000212302A - Polyester film for packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film excellent in protecting properties for contents as a packaging material, especially taste characteristics, long-period preserving properties and a reduction in catalyst metal components by specifying the amount of a residual catalyst metal and amount of residual phosphorus element. SOLUTION: This film is obtained by regulating the ratio (M/P) of the amount of a residual catalyst metal (M: unit mmol.%) and the amount of residual phosphorus element (P: unit mmol.%) in a polyester film to <1. The amount of the residual alkali in the film (A: ppm) is preferably <=10 ppm, the melting point of the film is preferably 240-280 deg.C, the degree of heteromorphy of a particle (ratio D/d of the maximum length D of the particle to the minimum length d thereof) contained in the film is preferably >=1.1 and >=90 mol.% in the acidic component constituting the polyester is preferably a terephthalic acid component and/or a 2,6-naphthalenedicarboxylic acid component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyester film for packaging. Specifically, it is not only excellent in preservability when used as a packaging material that comes into direct contact with the contents, but also used for molding and processing, laminating, especially laminating using metal, paper, and plastic as base materials, containers The present invention relates to a polyester film suitable for packaging.

[0002]

2. Description of the Related Art Conventionally, in the case of flexible packaging, a polyester film used as a packaging material is laminated using polyethylene, polypropylene and an adhesive or without using an adhesive, and the sealant layer is directly covered with the content. In order to come into contact with objects, contact between the polyester film and the contents was rarely considered.

[0003] However, in recent years, as packaging materials have been diversified and evolved, applications in which the polyester film and the contents are in direct contact have increased, and it has been considered to improve the quality of the polyester film with an increase in shelf life. I have.

[0004] In particular, when the contents are foods and beverages,
A case in which a change in quality due to contact with the polyester film is recognized, for example, a change in taste of a beverage or food may cause a problem because the value of the content is reduced as a product.

[0005] In the case of using a polyester film on the inner surface of a container, which has been increasing in recent years, among packaging materials, for example, a metal and a polyester film are laminated with or without an adhesive. The can is obtained by molding.

Conventionally, the inside and outside surfaces of metal cans are coated with a solution of various thermosetting resins such as epoxy or phenol dissolved or dispersed in a solvent for the purpose of corrosion protection, to coat the metal surface. Has been widely practiced. However, such a method of coating with a 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 on which various surface treatments such as plating are performed on the metal plate, which are materials of a 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 properties, and more recently, a metal catalyst component and a metal catalyst component to the contents of the metal can. There is an increasing demand to reduce the amount of impurity components mixed in the metal catalyst component, and the following properties are required for the film.

(1) It has excellent laminating properties on a metal plate.

(2) It has excellent adhesion to a metal plate.

(3) It is excellent in moldability and does not cause defects such as pinholes after molding.

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

(5) The taste of the contents of the can is not impaired by metal components and low molecular components in the film (hereinafter referred to as taste characteristics). Further, its properties are maintained for a long time (long-term storage property).

Among these demands, many proposals have been made to solve the taste characteristics.
In Japanese Patent No. 41361, the content of the catalytic metal and the content of phosphorus are specified in a specific range to achieve both taste characteristics and productivity.

However, in the method of casting a molten polymer film by electrostatic application as described in Japanese Patent Publication No. 37-6142, since a sufficient amount of metal and phosphorus is required in the polyester, it is necessary to secure taste characteristics. In particular, it was not sufficient in terms of long-term storage properties and reduction of catalytic metal components. In addition, it is insufficient to minimize the mixing of the metal catalyst component and the impurity component mixed with the metal catalyst component.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to protect the contents, especially the taste characteristics, long-term storage properties, and the catalytic metal component as a packaging material. An object of the present invention is to provide a polyester film for packaging which is excellent in reduction, enables molding and lamination, and has excellent taste characteristics and corrosion resistance even after severe molding such as drawing and ironing.

[0016]

SUMMARY OF THE INVENTION The object of the present invention is to provide a polyester film having a ratio (M / mole%) of the residual amount of catalyst metal (M: unit mmol%) to the residual amount of phosphorus element (P: unit mmol%). P) can be achieved by a packaging polyester film having a value of less than 1.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester constituting the polyester film of the present invention is a generic term for polymers having a main bond in the main chain as an ester bond, and is usually a polycondensation reaction of a dicarboxylic acid component and a glycol component. Can be obtained. Here, as the dicarboxylic acid component, for example, aromatic compounds such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid, and phthalic acid Group dicarboxylic acid, oxalic acid, succinic acid,
Examples thereof include aliphatic dicarboxylic acids such as 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.
Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, and polypropylene glycol; and cyclohexanedimethanol. Alicyclic glycol, bisphenol A,
And aromatic glycols such as bisphenol S.

From the viewpoint of heat resistance and taste characteristics, it is preferable that 90% by mol or more of the acid component of the polyester in the present invention is a terephthalic acid component and / or a 2,6-naphthalenedicarboxylic acid component. In applications having severe characteristics, it is preferable that 95% by mole or more of the acid component is a terephthalic acid component and / or 2,6-naphthalenedicarboxylic acid component because of excellent long-term storage properties.

The polyester film of the present invention comprises:
The melting point is preferably from 240 to 280 ° C. from the viewpoint of heat resistance and moldability. Further, in terms of moldability, the melting point is 246-2.
The temperature is preferably 75 ° C, particularly preferably 246 to
270 ° C.

The polyester film for packaging of the present invention comprises:
In order to make taste characteristics and long-term storage very good, the ratio (M / P) of the residual amount of catalytic metal (M: unit mmol%) to the residual amount of phosphorus element (P: unit mmol%) in the film is 1 It must be less than. More preferably, M / P is 0.3 or more and less than 1. When the ratio is 0.5 or more and less than 1, the productivity of the film does not deteriorate, so that it is more preferable.
Moreover, it is preferable in terms of taste characteristics that the residual amount of catalyst metal (M) in the film is 5 to 30 mmol%, and it is more preferable that the amount is 5 to 25 mmol%. On the other hand, the phosphorus element residual amount (P) is preferably 10 to 30 mmol%, more preferably 15 from the viewpoint of productivity and prevention of coloring.
２５25 mmol%.

Further, in the polyester film for packaging of the present invention, the heat resistance and the long-term storage stability, more specifically, the amount of alkali metal remaining in the film in order to suppress the change in taste at high temperatures and improve the storage stability (A: unit ppm) is 10p
pm or less, more preferably 7p
pm or less. Especially preferably, it is 5 ppm or less.

The catalyst for producing the polyester of the present invention is not particularly limited, but includes alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, titanium / silicon composite oxides, and germanium compounds. Etc. can be used.
Among them, a titanium compound, a titanium / silicon composite oxide, and a germanium compound are preferable in setting the catalytic activity, taste characteristics, and the amount of the catalytic metal.

For example, when a titanium / silicon catalyst is added as a catalyst, a terephthalic acid component and an ethylene glycol component are reacted, and then a titanium / silicon composite oxide,
A phosphorus compound is added, and subsequently a polycondensation reaction is performed under a high temperature and a reduced pressure until a constant diethylene glycol content is obtained.
A method of obtaining a polyester having a specific amount of catalyst metal and phosphorus is preferably employed.

The phosphorus compound added as a coloring inhibitor is not particularly limited, but phosphoric acid and phosphorous acid are preferred.

Further, it is preferable that particles are contained from the viewpoint of processability and handling as a packaging film.
Although the particle diameter and the amount of addition are not particularly limited, the particle diameter is 0.01 to 0.01 in terms of slipperiness during molding and adhesion during lamination.
It is preferable to contain 0.005 to 0.5% by weight of 5 μm particles.

Specifically, the inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate,
Examples include barium sulfate, alumina, mica, kaolin, and clay.

As the organic particles, various organic polymer particles can be used, and the type of the organic particles is not particularly limited as long as at least a part of the particles is insoluble in the polyester. Further, as a material of such particles, polyimide, polyamide imide,
Various materials such as polymethyl methacrylate, formaldehyde resin, phenol resin, cross-linked polystyrene, silicone resin, and mixtures and copolymer resins thereof can be used, but particles having high heat resistance and uniform particle size distribution can be obtained. Particularly preferred are vinyl-based crosslinked polymer particles which can be easily obtained.

In the polyester film of the present invention, the degree of irregularity of the particles (the ratio of the maximum length D to the minimum length d of the particles, D / d) is 1.1 or more from the viewpoint of abrasion resistance during molding. Preferably, there is. It is further preferable that D / d is 2.0 to 15 in order to further improve the moldability.

The polyester in the present invention preferably has a diethylene glycol content of 0.01 to 3.5% by weight, more preferably 0.01 to 2.5% by weight, particularly preferably 0.01 to 2.0% by weight. Is desirable in order to maintain excellent protection and taste characteristics of the contents even when subjected to many heat histories such as retort treatment in the packaging material.

In order to improve taste characteristics, the content of acetaldehyde in the film is preferably 20 ppm.
Below, it is more desirable to make it 15 ppm or less. If the acetaldehyde content exceeds 20 ppm, the taste characteristics may be inferior. The method of reducing the content of acetaldehyde in the film to 20 ppm or less is not particularly limited. For example, in order to remove acetaldehyde generated by thermal decomposition when producing a polyester by a polycondensation reaction or the like, the polyester is reduced under reduced pressure or A method in which heat treatment is performed at a temperature lower than the melting point of the polyester in an inert gas atmosphere, preferably a method in which the polyester is subjected to solid-state polymerization at a temperature of 155 ° C. or higher and a temperature lower than the melting point under reduced pressure or an inert gas atmosphere, using a vented extruder And a method in which the polymer is extruded at a melting point of + 25 ° C., preferably + 20 ° C. in a short time when the polymer is melt-extruded.

The intrinsic viscosity of the polyester is 0.05
０．１0.15 m3 / kg, and especially in applications where heat resistance and aging resistance are required, the intrinsic viscosity is 0.06 m3 / kg.
More preferably, it is 0.15 m3 / kg.

The film of the present invention has a thickness of 5 to 100 in terms of moldability, heat resistance and insulating properties after lamination on metal.
0 μm, more preferably 8 to 2 μm.
00 μm, particularly preferably 8 to 100 μm.

The method for producing a film in the present invention is not particularly limited. For example, after drying polyester as required, it is fed to a known melt extruder, extruded from a slit die into a sheet, and Alternatively, a method of applying static electricity using a tape-shaped electrode, a casting method in which a water film is provided between a casting drum and an extruded polymer sheet, a method of sticking a polymer by setting the temperature of the casting drum to a high temperature, or these methods There is a method in which a sheet-like polymer is brought into close contact with a casting drum and cooled and solidified to obtain an unstretched film by a method combining two or more kinds. Among these, productivity,
From the viewpoint of flatness, a method of applying static electricity is preferably used, and it is particularly preferable to use a tape-like electrode as the electrode.

A method of stretching and heat-treating the unstretched film in the longitudinal and width directions of the film to obtain a film having a desired refractive index in the thickness direction is particularly preferable in view of heat resistance and aging resistance. Preferably, a tenter method is preferable in terms of film quality.After stretching in the longitudinal direction, a sequential biaxial stretching method in which the film is stretched in the width direction, a simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the longitudinal direction and the width direction. Is desirable. The stretching ratio was 1. in each direction.
It is 5 to 10.0 times, preferably 2.0 to 6.0 times.
Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased, and may be the same. The stretching speed is 1000% /
Min to 200,000% / min, and the stretching temperature can be any temperature as long as it is equal to or higher than the glass transition temperature of the polyester and equal to or lower than the glass transition temperature + 80 ° C, but is preferably the glass transition temperature + 20 ° C to 60 ° C. .

After that, the film is subjected to a heat treatment. 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 from 60 to 250 ° C, but is preferably from 150 to 240 ° C. From the viewpoint of lamination properties and impact resistance, the heat treatment temperature is 170 to 220.
It is more preferable that the temperature is ° C. The heat treatment time can be arbitrarily set, but is preferably 0.1 to 60 seconds, and more preferably 1 to 20 seconds. Further, in the cooling after the heat treatment, it is preferable to provide an intermediate cooling zone at 100 to 180 ° C. and perform slow cooling from the viewpoint of obtaining the flatness of the film and, moreover, the uniform formability.

The polyester film for packaging of the present invention comprises:
The plane orientation coefficient is 0.0 in terms of moldability and film strength.
The surface orientation coefficient is preferably from 0.10 to 0.15, particularly preferably from 0.10 to 0.15, and more preferably from 0.10 to 0. .14. Here, the plane orientation coefficient is
When the refractive index in the longitudinal direction of the film is n _MD , the refractive index in the width direction of the film is n _TD , and the refractive index in the thickness direction of the film is n _ZD , the plane orientation coefficient fn = (n _MD + n _TD ) / 2−n _{Expressed as ZD} .

In view of the laminating property, the refractive index in the longitudinal direction of the film (nMD) and the refractive index in the width direction (nTD)
Birefringence (Δn = nMD−nTD) is 0.01
~ -0.05, more preferably-
0.001 to -0.04. Birefringence is -0.01 ~
A range of −0.04 is particularly preferable because not only the lamination property but also the impact resistance after lamination is good.

Further, from the viewpoint of moldability, heat resistance and aging resistance, it is preferable that the thickness direction refractive index n _ZD is 1.5 or more. In particular, it is preferably 1.51 to 1.55 in order to achieve both moldability and aging resistance. The heat treatment may be performed while relaxing the film in its longitudinal direction and / or its width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

It is preferable to further improve the adhesiveness by subjecting the film surface to a surface treatment such as a corona discharge treatment in order to improve the characteristics. At that time, E
The value is preferably 5 to 50 W · min / m 2, more preferably 10 to 45 W · min / m 2. Here, the E value is the intensity of corona discharge treatment, applied voltage (Vp, unit: V), applied current (Ip, unit: A), treatment speed (S, unit: m / min), treatment width ( Wt, unit: m), and is expressed by E = Vp × Ip / S × Wt.

The film of the present invention may be coated with various coatings, and the coating compound, method, and thickness are not particularly limited as long as the effects of the present invention are not impaired.

Further, it is preferable that the average value of the heat shrinkage in the film longitudinal direction and the width direction when the film is heat-treated at 150 ° C. for 30 minutes is 5% or less, in order to improve the laminability with metal. And 4% or less is particularly preferable.

The packaging polyester film of the present invention comprises:
It is used for packaging materials, and its use is not particularly limited as long as it is used for packaging, but examples include aluminum vapor deposition applications, metal oxide vapor deposition applications, polyester sealant applications, flexible packaging with polyester laminate laminates, containers, and the like. . Above all, it is preferably used for forming applications such as bending, drawing, and ironing, and more preferably used for forming after lamination with a substrate.

Particularly preferably, the laminate substrate is a metal,
It is desirable that the base material is selected from paper and plastic, and an adhesive may be used at the interface with metal, paper, and plastic as long as the properties are not significantly impaired. Preferably, the polyester film is directly adhered by heat. Packaging materials formed from a metal-polyester film, a paper-polyester film and a plastic-polyester film do not have direct contact between the base material and the contents, which are factors that change the taste, by the polyester film. preferable. In that case, it is particularly preferable that the laminate substrate is a metal in terms of barrier properties and sufficient heating, and is preferable because the protection of the contents is further improved.

Among these uses, it is particularly preferable to use them in molded containers containing beverages and foods as contents.

The metal plate used in the present invention is not particularly limited, but is preferably a metal plate mainly composed of a material selected from iron and aluminum in view of formability.

Further, in the case of a metal plate made of iron, an inorganic oxide coating layer for improving adhesion and corrosion resistance on the surface thereof, for example, chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic treatment A chemical conversion coating layer represented by chromic acid treatment, chromate treatment, chromium chromate treatment, or the like may be provided. Especially 5 to 20 as chromium in terms of metal chromium
0 mg / m ² chromium hydrated oxide is preferred,
A malleable metal plating layer, for example, nickel, tin, zinc, aluminum, gunmetal, brass, etc. may be provided. It is preferable that tin plating has a plating amount of 1 to ²⁰ mg / m ² , and nickel or aluminum has a plating amount of 1 to 25 mg / m ² .

The paper used in the present invention is not particularly limited, but the pulp content is preferably 90% or more, and recycled paper may be used.

[0048]

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

(1) Intrinsic viscosity of the film The film was dissolved in orthochlorophenol and measured at 25 ° C.

(2) Plane Orientation Coefficient, Birefringence Using an Abbe refractometer, the refractive index n _{MD in} the longitudinal direction, the refractive index n _{TD in} the width direction, and the refractive index n _ZD in the thickness direction with respect to the sodium D line are determined. Measured at 23 ° C. The plane orientation coefficient (fn) was determined from the respective refractive indices by the following equation.

Fn = (n _MD + n _TD ) / 2−n _ZD The birefringence (Δn) is the refractive index in the longitudinal direction of the film (n
MD) and the refractive index in the width direction (nTD) by the following formula.

Δn = nMD-nTD In the measurement of the refractive index, methylene iodide was used as the mounting liquid, and a polarizing plate analyzer was attached to the eyepiece of the refractometer, and the measurement was performed.

The laminated steel sheet was immersed in about 10 mol% concentrated hydrochloric acid to dissolve the steel sheet to obtain a laminated film. The refractive index of the non-laminated surface of the laminate film thus obtained was measured in the same manner as the film before lamination.

(3) Amount of alkali metal The film was dissolved in orthochlorophenol, extracted with a 0.5 mol% hydrochloric acid solution, and determined by atomic absorption analysis.

(4) Catalytic metal element amount and phosphorus element amount The amount of the catalytic metal element and the amount of phosphorus element were determined by fluorescent X-ray analysis. In the determination, a calibration curve using fluorescent X-rays obtained from a sample in which the amount of each metal element added was changed in advance was used.

The metal component due to the particles in the film was determined by removing the component. As a method for removing particles, for example, a film is dissolved in orthochlorophenol heated to 80 to 100 ° C., centrifugation is performed, particles are removed, and the polymer in the solution is precipitated. There is a way to do the analysis.

(5) Degree of Deformation of Particles A cross section of the film in the longitudinal direction was observed by a transmission electron microscope (TE).
M), the individual particles or those forming aggregates (aggregates) at intervals smaller than the primary particle diameter are regarded as one particle, and the maximum length D of each particle present in the film is determined.
And the minimum length d were obtained. The ratio (D / d) between the maximum length D and the minimum length d was defined as the particle irregularity. D and d
Was measured for at least 50 or more particles to obtain an average value.

(6) Melting point (Tm), heat treatment temperature (Ts) About 5 mg of the film was measured by a differential scanning calorimeter (DSC2, manufactured by Perkin-Elmer Co.) at a heating rate of 20 ° C./min, and the endothermic peak temperature was measured. The melting point (Tm) was used. The heat treatment temperature (Ts) is the peak temperature of the endothermic peak accompanying the heat treatment that appears as a subpeak on the lower side of the melting point.

(7) Amount of diethylene glycol The amount of diethylene glycol in the film was measured by ¹³ C nuclear magnetic resonance spectroscopy.

(8) Heat Shrinkage The distance between the marked lines is 200 mm in the longitudinal and width directions of the film.
The film cut to a width of 10 mm was suspended in the length direction, a 1 g load was applied in the length direction, heated for 30 minutes using hot air at 150 ° C, and the distance between the marked lines after cooling was measured. Heat shrinkage was measured as a percentage of the size. Five samples were measured in each of the longitudinal direction and the width direction, and the average value was obtained.

(9) Formability (Drawability) A tin-free steel metal plate (heat 0.24 mm) heated at 150 to 280 ° C. at 70 m / min was laminated and quenched. Using a laminated steel sheet having a surface orientation coefficient of 0.06 to 0.04 on the non-laminated surface side of the film after lamination, molding using a draw molding machine (forming ratio (maximum thickness / minimum thickness) = 1.9, At 80 to 100 ° C. in a moldable temperature range) to obtain a can. A 1% aqueous solution of sodium chloride was placed in the obtained can and left for 1 day. A voltage of 6 V was applied to the electrode and the metal can in the aqueous solution of sodium chloride, and the current value was read 3 seconds later. The value was determined. Note that the smaller the current value, the better the moldability.

A: less than 0.001 mA B: 0.001 to 0.01 mA C: 0.01 mA or more (10) Formability (bendability) A polyester film is heat-laminated on both sides of paper and molded to form a container. did. Bending was performed to prepare a beverage pack. The bent portion of the obtained pack was observed and judged as follows.

A: There is no whitening or crack in the film.

B: The film was slightly whitened, but no crack was found.

C: Whitening and cracks are observed in the film.

(11) Taste characteristics The film was laminated on both sides on a tin-free steel plate (0.2 mm thick) heated to a melting point of the film of +15 to + 30 ° C. at a rate of 70 m / min, and then cooled with hot water of 55 ° C.
The plane orientation coefficient on the non-laminated surface side after lamination is 0.0
Using a laminated steel plate having a thickness of 6 to 0.04, drawing and ironing were performed using an ironing machine. Thereafter, the laminated metal plate was formed at a reduction ratio of 20% to obtain a can. The obtained metal can is filled with purified water, tightly wound and sealed, and 80 ° C. × 2
Heat treatment was performed for 0 minutes. After opening, the following judgment was made by 20 panelists.

A: No more than one person has recognized a change in taste.

B: 2 to 4 persons who recognized a change in taste.

C: The number of persons who have recognized a change in taste is 5 or more.

(12) Long-term storage property The above metal container was filled with purified water, heat-treated at 110 ° C for 30 minutes, stored at 30 ° C for 4 weeks, and the following judgment was made by 20 panelists.

A: No more than one person has recognized a change in taste.

B: The number of persons who recognized a change in taste was 2 to 4 persons.

C: The number of persons who have recognized a change in taste is 5 or more.

Examples 1 to 5 and Comparative Examples 1 and 2 Films were formed using polyesters having the components, metal amounts and phosphorus amounts shown in Table 1.

In Example 1, polyethylene terephthalate was polymerized using a titanium / silicon composite oxide catalyst, phosphoric acid, and calcium carbonate particles (average diameter: 0.5 μm) as particles, and was sufficiently dried at 160 ° C. under vacuum, followed by drying at 280 ° C. To raise the surface temperature of the casting drum immediately before casting, and rapidly solidified on the cast while applying static electricity with a tape-shaped electrode to obtain an unstretched film.
The obtained unstretched film was successively stretched by a biaxial stretching machine.
The conditions at that time were a longitudinal stretching temperature of 105 ° C. and a longitudinal stretching ratio of 3.
0 times, transverse stretching temperature 115 ° C, transverse stretching ratio 3.0 times, heat treatment temperature 195 ° C, relaxation 5%.

In Example 2, polyethylene terephthalate was polymerized using a germanium oxide catalyst and phosphoric acid.
Full vacuum drying at 160 ° C and melt extrusion at 280 ° C to form a water film on the surface of the casting drum and quench and solidify on the cast while applying static electricity with electrodes on the tape to obtain an unstretched film Was. The obtained unstretched film was heated at a temperature of 11 with a simultaneous biaxial stretching machine of a linear motor system.
Simultaneous biaxial stretching at 0 ° C (stretching ratio 2.8 in both vertical and horizontal directions)
And a stretching speed of 3000% / min), and a heat treatment at 190 ° C. for 5% relaxation for 3 seconds to obtain a 20 μm film.

In Examples 3 to 5, a film was formed in the same manner as in Example 1 except that the polyester was changed. The film forming conditions were changed as shown in Table 1.

The physical properties of the obtained film are shown in Tables 1 and 2, and the characteristics are shown in Table 3.

Comparative Examples 1-2 Using polyesters having different amounts of catalyst metals and phosphorus,
A film was formed in the same manner as in Example 1. The film forming conditions were changed as shown in Table 1.

The physical properties of the obtained film are shown in Tables 1 and 2, and the characteristics are shown in Table 3.

The results obtained by using the polyester film of the present invention were excellent in moldability, taste characteristics and long-term storage stability.

The symbols in the table are as follows.

PET: polyethylene terephthalate PET / I *: polyethylene terephthalate copolymerized with isophthalic acid (* is copolymer mole%) PET / N *: polyethylene terephthalate copolymerized with 2,6-naphthalenedicarboxylic acid (* is copolymer mole%) PET / A *: adipic acid copolymerized polyethylene terephthalate (*: copolymerized mole%) M: residual amount of catalytic metal element (mmol%) P: residual amount of phosphorus element (mmol%) A: residual amount of alkali metal (ppm) IV : Intrinsic viscosity (m3 / kg) Ts: Endothermic peak temperature on DSC due to heat treatment (° C.) nMD: Refractive index in film longitudinal direction nTD: Refractive index in film width direction nZD: Refractive index in film thickness direction fn: Plane orientation Coefficient Δn: birefringence DEG: diethylene glycol

[0084]

[Table 1]

[0085]

[Table 2]

[0086]

[Table 3]

[0087]

Industrial Applicability The polyester film for packaging of the present invention is excellent in moldability, heat resistance, taste characteristics and long-term storage property, and is used for packaging materials, especially molding, lamination molding, and the like.
It can be suitably used for laminating processing and containers using metal, paper and plastic as base materials.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B65D 8/16 B65D 8/16

Claims (11)

[Claims] 1. A packaging polyester film in which the ratio (M / P) of the residual amount of catalytic metal (M: unit mmol%) to the residual amount of phosphorus element (P: unit mmol%) in the polyester film is less than 1. 2. The packaging polyester film according to claim 1, wherein the residual amount of alkali metal (A: unit ppm) in the polyester film is 10 ppm or less. 3. The polyester film having a melting point of 240 to
The polyester film for packaging according to any one of claims 1 to 2, which is at 280 ° C. 4. The particle according to claim 1, wherein the irregularity of the particles contained in the film (the ratio of the maximum length D to the minimum length d, D / d) is 1.1 or more. Polyester film for packaging. 5. The polyester of the acid component constituting the polyester, wherein 9
0 mol% or more of the terephthalic acid component and / or 2,6
The polyester film for packaging according to any one of claims 1 to 4, which is a naphthalenedicarboxylic acid component. 6. The method according to claim 1, which is used for molding.
The polyester film for packaging according to any one of the above. 7. A molding process after lamination.
The polyester film for packaging according to 1. 8. The packaging polyester film according to claim 7, wherein the laminate substrate is selected from metal, paper, and plastic. 9. The packaging polyester film according to claim 8, wherein the laminate substrate is a metal. 10. The method according to claim 6, which is used as a container after molding.
The polyester film for packaging according to any one of claims 9 to 9. 11. The packaging polyester film according to claim 10, which is used as a food or beverage container.