JP2001192475A - Polyester film for laminating to metal plate and molding the laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film which has excellent can-producing processability after laminated to a metal plate, has excellent heat resistance, impact resistance, corrosion resistance and deep draw formability, and especially has excellent hydrolysis resistance and taste and smell retainabilyty. SOLUTION: This biaxially oriented polyester film containing a lubricant having an average particle diameter of <=2.5 μm in an amount of 0.05 to 5.0 wt.%, characterized in that the concentrations of titanium element metal and phosphorus element in the polyester and the concentration of acetaldehyde in the film satisfy the following expression (1): 0.2<=(AA+P)/Ti<=20...(1) [AA is the concentration (ppm) of the acetaldehyde contained in the film; P is the concentration (ppm) of the phosphorus element contained in the polyester; Ti is the concentration (ppm) of the titanium metal element contained in the polyester].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for laminating and forming a metal plate, and more particularly, it shows excellent formability when laminating to a metal plate and performing can forming such as drawing. TECHNICAL FIELD The present invention relates to a polyester for metal plate lamination molding capable of producing metal cans, such as beverage cans, food cans, and the like, which are excellent in properties, retort resistance, flavor and fragrance retention, impact resistance, rust resistance and the like.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion on the inner and outer surfaces, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention is performed without using an organic solvent. Development of a method for obtaining the property has been advanced, and as one of the methods, coating with a thermoplastic resin film has been attempted. That is, a method of laminating a thermoplastic resin film on a metal plate of tin, tin-free steel, aluminum, or the like, followed by drawing, etc., has been studied. Polyolefin films and polyamide films have been tried as this thermoplastic resin film, but they do not satisfy all of moldability, heat resistance, impact resistance, and flavor and fragrance retention.

[0003] Therefore, attention has been paid to polyester films, especially polyethylene terephthalate films because of their well-balanced properties, and several proposals based on this have been made (JP-A-56-10451, JP-A-56-10451). JP-A-64-22530, JP-A-1-19
No. 2545, JP-A-1-192546, JP-A-2-57339, etc.). However, the present inventors have found that it is insufficient to satisfy all of the moldability, retort resistance, flavor retention and fragrance retention, especially in the case of molding with large deformation.

[0004] Copolymerized polyester films have been studied as satisfying moldability, heat resistance, impact resistance, and flavor and fragrance retention.
Japanese Patent Application Laid-Open No. 6-39979 discloses a polyester film for metal plate lamination molding comprising a copolymerized polyester having a specific melting point, glass transition temperature and terminal carboxyl group concentration. Although a polyester film for laminating and forming a metal plate on which a copolymerized polyester having a glass transition temperature is laminated has been proposed, according to studies by the present inventors, cans using these films are used, for example, for beverage containers. In this case, it became clear that a change in odor and taste as described in, for example, Japanese Patent Application Laid-Open No. 55-23136 was detected depending on the type of beverage.

Japanese Patent Application Laid-Open No. 6-116376 proposes a polyester film for forming a metal plate comprising a copolymerized polyester containing a specific amount of an alkali metal element and a germanium element. In the case where the content is packed, such as a cold pack system, the process that does not receive heat shows excellent flavor and aroma retention, but in the process where the heat treatment is performed at the stage of packing the content, such as retort treatment, it is not always necessary. There is a problem that sufficient flavor retention cannot be obtained.

In Japanese Patent Application Laid-Open No. 8-40437,
A polyester film containing a specific amount of oligomers and an alkali metal element is disclosed in JP-A-9-24136.
No. 1 and JP-A-10-231413 propose copolymerized polyesters in which the content of alkali metal and catalytic metal compound and the compounding ratio of phosphorus compound are within a specific range. The productivity and the thermal degradation during the production of the biaxially oriented film are not always sufficient, and further improvement in performance has been desired.

Further, Japanese Patent Application Laid-Open No. 9-70934 proposes a laminated polyester film containing a specific amount of a specific metal. However, in a process in which a heat treatment is performed at a stage where contents are packed such as a retort treatment. However, there is a problem that the hydrolysis resistance is not sufficient, and sufficient flavor and fragrance retention cannot be obtained.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and to maintain the excellent heat resistance, impact resistance, deep drawability and rust resistance of polyester films while maintaining their resistance. It is an object of the present invention to provide a polyester film for laminating and processing a metal plate which is improved in hydrolyzability and flavor and fragrance preservation, has high productivity, is inexpensive and has good hygiene.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the content of polymer-soluble titanium metal, the content of phosphorus element, and the content of acetaldehyde contained in the film. By controlling the ratio within a specific range, the conventional good laminability,
The present inventors have found that while maintaining the deep drawability, heat resistance, impact resistance, and retort resistance, it is possible to remarkably improve hydrolysis resistance and flavor retention, which were difficult to achieve conventionally, and the present invention. Was completed.

[0010] That is, the present invention provides an average particle size of 2.5 µm
A biaxially oriented polyester film comprising a polyester containing 0.05 to 5.0% by weight of the following lubricant and having ethylene terephthalate as a main repeating unit, wherein the polyester contains a soluble titanium compound in the polymer. The titanium metal element concentration and the phosphorus element concentration in the polyester and the acetaldehyde concentration in the film satisfy the following formula (1), and the total of the antimony metal element concentration and the germanium metal element concentration in the polyester is 15 ppm or less. And the polyester has a melt resistivity at 290 ° C. of 1 × 10 ^{6 to} 5 × 1.
0 is a polyester film for combined molding bonded metal plate, which is a ^{8 Ω} · cm. 0.2 ≦ (AA + P) / Ti ≦ 20 (1) (In the above formula, AA is the concentration (ppm) of acetaldehyde contained in the film, and P is the phosphorus element of the phosphorus compound contained in the polyester. Concentration (ppm), Ti is the concentration of titanium metal element contained in polyester (ppm)
Is shown. )

Hereinafter, the present invention will be described in detail. The polyester in the present invention is a polyester containing ethylene terephthalate as a main repeating unit. As the polyester, copolymerized polyethylene terephthalate obtained by copolymerizing a third component other than the component constituting the ethylene terephthalate unit is preferable in terms of heat resistance and moldability. The third above
The component (copolymer component) may be either a dicarboxylic acid component or a glycol component. Examples of the dicarboxylic acid component preferably used as the third component include aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, isophthalic acid, and phthalic acid, and fatty acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. Group dicarboxylic acids,
Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be exemplified, and these can be used alone or in combination of two or more. Of these, 2,6-naphthalenedicarboxylic acid and isophthalic acid are preferred. Glycol components preferably used as the third component include aliphatic diols such as diethylene glycol, propylene glycol, neopentyl glycol, butanediol, pentanediol and hexanediol, alicyclic diols such as cyclohexanedimethanol, and bisphenol A.
And polyalkylene glycols such as polyethylene glycol and polypropylene glycol. These can be used alone or in combination of two or more. Of these, diethylene glycol is preferred. As the polyester in the present invention, the following three types of copolymerized polyesters are preferable. (a) the total dicarboxylic acid component comprises terephthalic acid and isophthalic acid and the terephthalic acid is at least 82 mol%, the isophthalic acid is at most 18 mol%, and 82-100 mol% of the total diol component is ethylene; A copolymerized polyester which is a glycol and comprises from 0 to 18 mol% of a diol other than ethylene glycol. (b) terephthalic acid and 2,6-
It contains naphthalenedicarboxylic acid and terephthalic acid is more than 82 mol%, 2,6-naphthalenedicarboxylic acid is less than 18 mol%, and 8
2-100 mol% is ethylene glycol and 0
~ 18 mol% of a copolymerized polyester comprising a diol other than ethylene glycol. (c) A copolymer polyester in which the dicarboxylic component is terephthalic acid, the glycol component contains ethylene glycol and diethylene glycol, and the ethylene glycol is 95 mol% or more and the diethylene glycol is 5 mol% or less.

The above-mentioned copolymerized polyester (b) is preferred in view of flavor and moldability. Further, the above (a)
It is preferable that the copolymerized polyester further contains 2,6-naphthalenedicarboxylic acid as a dicarboxylic acid component, whereby the flavor and impact resistance are further improved. Examples of glycol components other than ethylene glycol in the copolymerized polyesters (a) and (b) include triethylene glycol, cyclohexanedimethanol, neopentyl glycol, and diethylene glycol.
It is preferable to contain more than one kind in terms of flavor and moldability. It is particularly preferred that the copolymerized polyester (c) has a copolymerization amount of the diethylene glycol component to all the glycol components of 4 mol% or less. When the copolymerization amount of diethylene glycol exceeds 5 mol%, heat resistance may be reduced. The diethylene glycol component also includes a diethylene glycol component by-produced when producing a copolymerized aromatic polyester containing ethylene glycol as a glycol component.

The polyester of the present invention can be synthesized by any method. For example, a copolymerized polyethylene terephthalate which copolymerizes a third component such as isophthalic acid will be described.A lower alkyl ester of terephthalic acid and isophthalic acid is transesterified with ethylene glycol, or terephthalic acid and isophthalic acid are mixed with ethylene glycol. Is directly esterified, or
Furthermore, glycol terephthalate and / or
Alternatively, the low-polymer and isophthalic acid are subjected to an esterification reaction to carry out a first-stage reaction for producing a terephthalic acid-isophthalic acid glycol ester and / or the low-polymer. By subjecting the reaction product to high-vacuum heating to advance the deglycolization reaction, a polycondensation reaction can be performed until a desired degree of polymerization is reached, thereby obtaining the desired polyester. The polyester obtained by the above method (melt polymerization) can be converted into a polymer having a higher degree of polymerization, if necessary, by a polymerization method in a solid state (solid state polymerization).

In the present invention, when the first stage reaction during melt polymerization is carried out by a transesterification reaction, it is necessary to add a transesterification catalyst during the reaction. The transesterification catalyst is not particularly limited as long as it is a commonly used transesterification catalyst, and includes a calcium compound, a manganese compound, a titanium compound, and the like. Titanium compounds are desirable in that they have fragrance. As a catalyst used for the polycondensation reaction of the polyester, a titanium compound soluble in a polymer is used in terms of excellent hydrolysis resistance and flavor and fragrance retention. It does not specifically limit as a titanium compound, Titanium acetate, tetrabutoxy titanium, etc. are mentioned preferably.

The polyester of the present invention preferably contains 4 to 50 pp as a titanium metal element soluble in the polymer.
m, particularly preferably in the range of 7 to 35 ppm. If the titanium metal element is less than 4 ppm, the productivity of the polyester decreases, and a polyester having a target molecular weight cannot be obtained. On the other hand, when the titanium metal element exceeds 50 ppm, the thermal stability is conversely reduced, and the molecular weight during the production of the film is greatly reduced, so that the desired polyester cannot be obtained.
In the case of the first step reaction by transesterification, the titanium metal element soluble in the polymer mentioned here is a titanium compound used as a transesterification catalyst and a titanium compound used as a polycondensation reaction catalyst. Shows the sum of the compounds.

When an antimony compound or a germanium compound used as a general polyester catalyst is used in the polyester of the present invention, the antimony compound increases foreign substances in the film due to reduction of antimony and sublimates during film formation. Inferior moldability and flavor retention due to the generation of a large amount of substances, high cost of industrial production due to expensive germanium compounds, and further improvement is required in terms of hydrolysis resistance while at the practical level Is not preferred. In addition, when these two types of metal compounds are used in combination as a polycondensation catalyst in the titanium catalyst of the present invention, a polyester film having the flavor preserving property and the hydrolysis resistance obtained in the present invention cannot be obtained. Therefore, the total amount of the antimony metal element and the germanium metal element contained in the polyester must be 15 ppm or less. More preferably, the total amount is 10 ppm or less.

Conventionally, there has been widely known a technique of adding a phosphoric acid-based stabilizer in order to suppress the catalyst activity in the polyester and obtain good thermal stability. Addition of a phosphoric acid-based stabilizer in an amount necessary for obtaining thermal stability suppresses the polymerization reaction activity, and it has been difficult to obtain a polymer having a desired degree of polymerization. Furthermore, it has been found that a polyester produced using a titanium catalyst polymerized by a conventional technique has a problem in that the hydrolysis resistance, which is an object of the present invention, is reduced. As a result of the present inventors' research to solve such a problem, acetaldehyde which is a by-product at the time of polyester polymerization shows a high interaction with a polymer-soluble titanium compound added as a catalyst, and reduces the polymerization activity of the titanium catalyst. It has been found that high thermal stability can be obtained without doing so. Furthermore, by controlling the respective abundance ratios in consideration of the interaction between the conventionally known phosphate-based stabilizer and the titanium catalyst, it is possible to greatly improve the productivity, hydrolysis resistance, and flavor and fragrance retention of the polyester. I found it. That is, it has been found that when the titanium metal element concentration and the phosphorus element concentration in the polyester and the acetaldehyde concentration in the film satisfy the following formula (1), the above-mentioned interaction becomes remarkable. 0.2 ≦ (AA + P) / Ti ≦ 20 (1) (In the above formula, AA is the concentration (ppm) of acetaldehyde contained in the film, and P is the phosphorus element of the phosphorus compound contained in the polyester. Concentration (ppm), Ti is the concentration of titanium metal element contained in polyester (ppm)
Is shown. )

When the value of (AA + P) / Ti is less than 0.2, the activity of Ti is increased and the heat resistance and the hydrolysis resistance are inferior. On the other hand, when the value of (AA + P) / Ti is more than 20, the taste and fragrance retention properties are significantly inferior, and the desired polyester film cannot be obtained.

In the present invention, the concentration of acetaldehyde contained in the polyester film is 0.1 to 3
0 ppm, more preferably 0.1 ppm.
-20 ppm. If it is less than 0.1 ppm, the activity of titanium in the polyester cannot be suppressed, and
If it exceeds m, the flavor and fragrance retention properties will be significantly inferior, which is not preferable.

As described above, the polyester in the present invention is not particularly limited by its production method, but is produced using a titanium compound as a catalyst and a phosphorus compound as a stabilizer.
It is preferable that the following expressions (2) and (3) are satisfied. 0.2 ≦ Ti / P ≦ 4.5 (2) 10 ≦ Ti + P ≦ 85 (3) (In the above formula, Ti is a titanium metal element of the polyester-soluble titanium compound contained in the polyester. Concentration (pp
m) and P indicate the concentration (ppm) of the phosphorus element of the phosphorus compound contained in the polyester. )

More preferably, the following (4):
The range is (5). 0.4 ≦ Ti / P ≦ 3.5 (4) 15 ≦ Ti + P ≦ 75 (5) When (Ti / P) is less than 0.2, the polymerization reactivity of the polyester is significantly reduced. And the desired polyester cannot be obtained. When (Ti / P) exceeds 4.5,
Thermal stability is rapidly reduced, and the desired polyester cannot be obtained. When a titanium compound is used for the production of the polyester in the present invention, the proper range of (Ti / P) is characterized in that it is narrower than the metal catalyst used in the prior art. The effect which cannot be obtained can be obtained. On the other hand, when (Ti + P) is less than 10, the productivity in the film forming process by the electrostatic application method is greatly reduced, and the reduction in the formability and the resistance to molding due to the reduction in the uniformity of the film thickness are also observed. The impact property is reduced, and satisfactory performance cannot be obtained. If (Ti + P) exceeds 85, the flavor property is reduced due to the low molecular weight component of the polyester generated by the interaction with the polyester, and satisfactory performance cannot be obtained. The “phosphorous element” is derived from a phosphorus compound used to deactivate a catalyst or as a stabilizer for a polymer.

In the polyester of the present invention, the total amount of the alkali metal elements in the alkali metal compound is preferably 5 ppm or less in order to maintain the taste and aroma. Especially preferably, it is 3 ppm or less. The total amount of the alkali metal elements is determined by atomic absorption analysis of Li, Na and K.
It is the sum of the ppm concentrations of the elements.

Further, when producing the film of the present invention, in order to obtain excellent flatness by adopting an electrostatic application method, and when laminating to a metal plate and forming into a metal can, the laminability and moldability are reduced. In order to make the copolymer excellent, the melting specific resistance of the copolymerized polyester at 290 ° C. is 1 × 10 ^{6 to} 5 × 1.
It is necessary to set to 0 ⁸ Ω · cm. Melting specific resistance value is 1 × 1
0 unfavorably to Homi aroma retention after can manufacturing is poor at the time of less than ^{6 Ω} · cm. Further, the melting specific resistance value is 5 × 10 ⁸
If it exceeds Ω · cm, the film productivity is lowered, and the laminating formability is poor, which is not preferable. In order to make the melting specific resistance value within this range, it can be achieved by adjusting the abundance ratio of acetaldehyde to the polymer-soluble titanium compound and the phosphorus compound in the above-mentioned polyester film within an appropriate range of the present invention.

In the present invention, the intrinsic viscosity of the film (ο-
Chlorophenol, 35 ° C.) is preferably in the range of 0.5 to 0.8, more preferably 0.55 to 0.8.
0.75, particularly preferably 0.60 to 0.70.
If the intrinsic viscosity is less than 0.50, the impact resistance of the film becomes insufficient, which is not preferable. On the other hand, the intrinsic viscosity is 0.80
If it exceeds, it is necessary to raise the intrinsic viscosity of the raw material polymer excessively, which is uneconomical.

The glass transition temperature (hereinafter sometimes abbreviated as Tg) of the film of the present invention is 70 ° C. or higher, especially 73 ° C.
It is preferable that it is above. When the Tg is less than 70 ° C., the heat resistance becomes poor, and the film retains the flavor and aroma after retort treatment. The Tg of the film was determined by placing a 20 mg sample in a pan for DSC measurement, heating and melting on a 290 ° C. heating stage for 5 minutes, and then rapidly solidifying the sample pan on an aluminum foil laid on ice, followed by Du Pont.
A method of determining the glass transition point at a temperature rising rate of 20 ° C./min using Instruments 910 DSC.

The film of the present invention has a melting point of 210 to 25.
It is preferably in the range of 0 ° C, particularly in the range of 215 to 245 ° C. If the melting point is lower than 210 ° C., the heat resistance of the film is inferior, which is not preferable. On the other hand, if the melting point is higher than 250 ° C., the crystallinity of the film is increased and the moldability of the film is impaired. The melting point of the film was measured using Du Pont Instruments 91
0 By using DSC and determining the melting peak at a heating rate of 20 ° C./min. The sample amount is 20 mg.

Further, the polyester film in the present invention preferably has a terminal carboxyl group concentration of 40 eq / 10 ⁶ g or less, particularly preferably 35 eq / 10 ⁶ g or less. The terminal carboxyl group is A.I. It can be determined according to the method of Conix (Makromol. Chem. 26, 226 (1958)).

The polyester as described above in the present invention must contain a lubricant having an average particle size of 2.5 μm or less. It is preferably from 0.05 to 2.0 μm, and more preferably from 0.1 to 1.5 μm. 2.5μ average particle size
If it exceeds m, pinholes are apt to occur during molding, which is not preferable. As the average particle diameter of the lubricant, a value at an integrated 50% point in an equivalent spherical diameter distribution obtained by a centrifugal sedimentation type particle size distribution analyzer is used. The content of the lubricant used in the present invention is 0.0
It must be from 5 to 5.0% by weight. Preferably 0.0
The content is 8 to 3.0% by weight, and more preferably 0.1 to 1.0% by weight.
0% by weight. If the content is less than 0.05% by weight, film winding property is insufficient and productivity is poor. On the other hand, if it exceeds 5.0% by weight, pinholes are formed in the film at the time of molding, which is not preferable. Although the lubricant used in the present invention is not particularly limited, for example, as inorganic particles, colloidal silica, porous silica, titanium oxide,
Examples thereof include calcium carbonate, calcium phosphate, barium sulfate, alumina, zirconia, kaolin, and composite oxide particles, and examples of the organic particles include crosslinked polystyrene, acrylic crosslinked particles, methacrylic crosslinked particles, and silicone particles. Further, the present invention is not limited to the externally added particles as described above, and it is also possible to use, for example, internally precipitated particles obtained by precipitating part or all of the catalyst used in the production of the copolymerized polyester in the reaction step. It is also possible to use externally added particles and internally precipitated particles in combination. Among these, inorganic particles are preferred, and among them, colloidal silica is preferred in terms of molding. The method of including a lubricant in the copolymerized polyester in the present invention is not particularly limited,
For example, a method of adding at an optional stage in the process of producing a copolymerized polyester is exemplified. In addition, the copolymerized polyester, if necessary, an antioxidant, a heat stabilizer, a viscosity modifier,
Additives such as a plasticizer, a hue improver, a nucleating agent, and an ultraviolet absorber can be added.

The film of the present invention is used in the form of a biaxially stretched film which is biaxially stretched and optionally heat-set. Specifically, a method by sequential biaxial stretching will be described below. The film of the present invention is obtained by melting and extruding polyester from a die, laminating and fusing before solidification, and immediately quenching to obtain a substantially amorphous polyester sheet. Next, this sheet is heated by roll heating, infrared heating or the like and stretched in the longitudinal direction. At this time, the stretching temperature is preferably 20 to 40 ° C. higher than the glass transition point (Tg) of the polyester, and the stretching ratio is preferably 2.7 to 3.6 times. The stretching in the transverse direction is preferably started at a temperature 20 ° C. or more higher than Tg, and then performed while increasing the temperature to 100 to 130 ° C. lower than the melting point (Tm) of the polyester. The magnification of transverse stretching is 2.
It is preferable to make it 8 to 3.7 times. The heat setting temperature is selected in the range of 150 ° C. to 205 ° C. to adjust the film quality according to the melting point of the polyester polymer.

The refractive index in the thickness direction of the film of the present invention is preferably from 1.500 to 1.540,
More preferably, it is 1.505 to 1.530. If the refractive index is too low, the moldability will be insufficient, while if it is too high, the film will have a structure close to amorphous, and the heat resistance may decrease.

The center line average roughness (Ra) of the film surface of the polyester film of the present invention is preferably 30 nm or less, more preferably 25 nm or less, and particularly preferably 20 nm or less.
nm or less.

The film of the present invention has a thickness of 6 to 75 μm.
Is preferred. Further, it is preferably from 8 to 75 μm, particularly preferably from 10 to 50 μm. If the thickness is less than 6 μm, breakage or the like is likely to occur during molding, while if it exceeds 75 μm, the quality is excessive and uneconomical.

A metal plate on which the film of the present invention is bonded,
In particular, as a metal plate for can making, a plate of tin, tin-free steel, aluminum or the like is suitable. The lamination of the film to the metal plate can be performed, for example, by the following method. The metal plate is heated to a temperature equal to or higher than the melting point of the film, the film is laminated, and then cooled. The surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. An adhesive layer is primer-coated on the film in advance, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive, for example, an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used.

[0034]

The present invention will be further described with reference to the following examples.
The properties of the film were measured and evaluated by the following methods. (1) Intrinsic viscosity ([η]) of polyester Measured in orthochlorophenol at 35 ° C.

(2) Melting point (Tm) of polyester Du Pont Instruments 910 D
A method in which a melting peak is determined at a heating rate of 20 ° C./min using SC. The sample amount is 20 mg.

(3) Glass transition temperature (Tg) A 20 mg sample was placed in a pan for DSC measurement, and 290
After heating and melting on a heating stage for 5 minutes, the sample pan was quickly cooled and solidified on an aluminum foil laid on ice, and then Du was added.
Pont Instruments 910 DSC
To determine the glass transition point at a heating rate of 20 ° C./min.

(4) Terminal carboxyl group concentration (equivalent / 1
0 ⁶ g) A. It is measured according to the method of Conix. (Makro
mal. Chem. 26, 226 (1958))

(5) Lubricant average particle diameter The diameter of 50% of the integrated volume fraction in the equivalent spherical diameter distribution measured by a centrifugal sedimentation type particle size distribution analyzer is defined as the average particle diameter.

(6) Amount of Alkali Metal After the film sample was dissolved in o-chlorophenol, extraction was performed with 0.5N hydrochloric acid. This extract was subjected to quantification of Na, K, and Li for each element using a polarized Zeeman atomic absorption spectrophotometer, Model Z-6100, manufactured by Hitachi, Ltd.

(7) Titanium metal element, germanium metal element, antimony metal element and phosphorus element amount A film sample was heated and melted at 240 ° C. to form a circular disk, and a catalyst was prepared using a Rigaku fluorescent X-ray apparatus Model 3270. Quantify metal and phosphorus element concentrations.

(8) Amount of diethylene glycol The film is dissolved in a mixed solvent of CDCl ₃ / CF ₃ COOD and measured by ¹ H-NMR.

(9) Acetaldehyde Amount The amount of acetaldehyde generated when the film was heat-treated at 160 ° C. for 20 minutes was quantified by gas chromatography.

(10) Electric Resistance of Polymer Melt British. J. Appl. Phys. (17,1
149-1154 (1966)). The sample was melted at 290 ° C.
The measured value stabilized by applying 000 V was taken as the melting specific resistance value.

(11) Hydrolysis resistance The film was immersed in a container filled with ion-exchanged water,
C. for 30 days. The decrease in molecular weight at this time was evaluated by measuring the intrinsic viscosity described in (1). ：: IV decrease is 0.04 or less Δ: IV decrease exceeds 0.04 and less than 0.10 ×: IV decrease is 0.10 or more

(12) Laminability The film was bonded to a tin-free steel plate having a thickness of 0.25 mm heated above the melting point of the copolymerized polyester, and then cooled to obtain a coated steel plate. Observe this coated steel sheet,
Laminability was evaluated according to the following criteria. [Criteria for judging bubbles and wrinkles (lamination property A)] 〇: No bubbles and wrinkles are observed. Δ: Bubbles and wrinkles are observed at two or three places per 10 cm in length. ×: Many bubbles and wrinkles are observed. [Judgment criteria for heat shrinkage (laminability B)] 〇: Shrinkage is less than 2%. Δ: Shrinkage rate is 2% or more and less than 5%. X: Shrinkage rate is 5% or more.

(13) Deep drawing workability-1 A tin-free steel plate on which a film was laminated in the same manner as in (12) above was cut into a disk having a diameter of 150 mm, and was deep drawn in four stages using a drawing die and a punch. By processing, a side-seamless container having a diameter of 55 mm (hereinafter, sometimes abbreviated as a can) was prepared. The following observations were made on this can and evaluated according to the following criteria. ：: No whitening or breakage is observed in the film processed without any abnormality. Δ: Whitening is observed at the top of the film can. X: Film breakage is observed in a part of the film.

(14) Deep drawing workability-2 The following observations and tests were performed on the cans obtained in the above section (13), and evaluated according to the following criteria. ：: Processed without any abnormality, rust prevention test of film surface in can (1% NaCl aqueous solution was put into the can, electrode was inserted, current value was measured when 6V voltage was applied with the can body as anode) Hereinafter, it may be abbreviated as ERV test). ×: There is no abnormality in the film, but the current value exceeds 0.2 mA in the ERV test, and pinhole-shaped cracks starting from the coarse lubricant of the film are observed when the energized portion is observed under magnification.

(15) Impact resistance For cans having good deep drawability, pour water thoroughly, cool to 0 ° C., drop 10 pieces from a height of 30 cm onto a PVC tile floor, and apply ERV. A test was performed and evaluated according to the following criteria. ：: 0.2 mA or less for all 10 samples. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: The film exceeded 0.2 mA for 6 or more pieces, or cracks of the film were already observed after dropping.

(16) Heat Embrittlement Resistance A can having good deep drawing workability was heated and held at 200 ° C. for 5 minutes, and then subjected to the above-described impact resistance evaluation, which was evaluated according to the following criteria. ：: 0.2 mA or less for all 10 samples. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: The film exceeded 0.2 mA for 6 or more pieces, or cracks of the film were already observed after heating at 200 ° C. for 5 minutes.

(17) Retort resistance A can with good deep drawing workability was filled with water and retorted in a steam sterilizer at 120 ° C. for 1 hour.
Stored at 60 ° C for 60 days. 5 cans of 10 cans each after treatment
ERV in can after dropping from 0cm onto PVC tile floor
A test was performed and evaluated according to the following criteria. ：: 0.2 mA or less for all 10 samples. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: The film exceeded 0.2 mA for 6 or more pieces, or cracks of the film were already observed after dropping.

(18) Taste preservation -1 A can having good deep drawing workability was filled with ion-exchanged water and stored at room temperature (20 ° C) for 60 days. A tasting test was conducted by 30 panelists using the filled liquid, and compared with ion-exchanged water for comparison, and evaluated according to the following criteria. ：: Three or less out of thirty felt changes in taste and aroma as compared with the comparative solution. 〇: Four to six out of thirty people felt a change in taste and aroma as compared with the comparative solution. Δ: 7 to 9 out of 30 persons felt a change in taste and aroma as compared with the comparative solution. ×: Ten or more of the 30 persons felt a change in taste and aroma as compared with the comparative solution.

(19) Taste preservation property-2 Cans having good deep drawing properties were filled with ion-exchanged water, subjected to a retort treatment at 125 ° C. for 1 hour in a steam sterilizer, and then at room temperature (20 ° C.). Stored for 60 days. A tasting test was conducted by 30 panelists using the filled liquid, and compared with ion-exchanged water for comparison, and evaluated according to the following criteria. ：: Three or less out of thirty felt changes in taste and aroma as compared with the comparative solution. 〇: Four to six out of thirty people felt a change in taste and aroma as compared with the comparative solution. Δ: 7 to 9 out of 30 persons felt a change in taste and aroma as compared with the comparative solution. ×: Ten or more of the 30 persons felt a change in taste and aroma as compared with the comparative solution.

Examples 1 to 5 and Comparative Examples 1 to 5
After drying the copolymerized polyethylene terephthalate (containing 0.3% by weight of spherical silica particles having an average particle diameter of 0.5 μm) obtained by using the components, catalyst and ethylene glycol shown in (1), melt-extrusion at 280 ° C. and solidification by rapid cooling Thus, an unstretched film was obtained. Next, the unstretched film was stretched 3.0 times in the longitudinal direction at 110 ° C., stretched 3.0 times in the transverse direction at 120 ° C., and heat-set at 180 ° C. to obtain a biaxially oriented film. The thickness of each of the obtained films was 25 μm. Other characteristics are shown in Table 1, and the evaluation results are as shown in Table 3.

[0054]

[Table 1]

[Examples 6 to 10] As shown in Table 2, the same copolymerization as in Example 1 except for the molten electric resistance, the amount of alkali metal, the Ti / P value, the Ti + P value and the (AA + P) / Ti value. Polyethylene terephthalate was polymerized to obtain a biaxially stretched polyester film. The results are shown in Table 3.

[0056]

[Table 2]

[0057]

[Table 3]

As is apparent from Table 3, the melt electric resistance of the copolymerized polyethylene terephthalate is 1 × 10 ^{6 to} 5
× 10 ⁸ Ω · cm, the (AA + P) / Ti value of the biaxially oriented film is in the range of 0.2 to 20 ppm, and the total content of Ge metal element and Sb metal element in the film is 15 ppm In the case of the film of the present invention in the following range (Examples 1 to 10), good results were obtained, but when the melt electric resistance exceeded 5 × 10 ⁸ Ω · cm (Comparative Example 1), And poor drawability. Also,
When (AA + P) / Ti value exceeds 20 (Comparative Example 2)
Was inferior in flavor retention and flavor retention, and when less than 0.2 (Comparative Example 3), hydrolysis resistance was poor. Further, when a combination of a germanium compound and an antimony compound is used in combination with a titanium compound as a polymerization catalyst in a range exceeding 15 ppm in total (Comparative Example 4) and when an antimony compound is used instead of the titanium compound (Comparative Example 5), respectively, Degradability,
The flavor and fragrance retention was insufficient.

[0059]

According to the present invention, hydrolysis resistance and flavor retention are improved while maintaining excellent heat resistance, impact resistance, deep drawability and rust resistance, and further high production is achieved. It is possible to provide a polyester film for laminating and forming a metal plate which has good properties, is inexpensive, and is also desirable in terms of hygiene.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/00 C08K 3/00 C08L 67/02 C08L 67/02 // B65D 1/09 (C08L 67/02 (C08L 67/02 101: 00) 101: 00) B65D 1/00 B (72) Inventor Kimihiko Sato 77, Kitayoshida-cho, Matsuyama-shi, Ehime F-term in Teijin Limited Matsuyama Office (reference) 3E033 BA07 BA17 BB08 CA03 CA07 CA14 CA20 FA01 4F071 AA01 AA45 AA46 AA84 AA86 AA88 AB01 AE11 AF31Y AF36Y AH05 BB08 BC01 BC02 BC10 4F100 AA01A AB01B AB12A AK42A BA02 DE19 EJ38A GB16 GB23 JA04A JA02 J03 J02B01 J02B03 DH046 DJ016 DJ036 FA082 FA096 FD172 FD176 GF00 GG01 4J029 AA03 AB01 AC02 AD01 AD02 AD06 AD07 AD10 AE03 AE18 BA02 BA03 BA05 BA08 BA10 BB13A BD06A BF09 BF25 CA02 CA06 CB04A CB05A CB06A CC06A CD03 JE182 JF321 JF361 JF471 KB02

Claims (12)

[Claims] 1. A lubricant having an average particle size of 2.5 μm or less is added to 0.0
What is claimed is: 1. A biaxially oriented polyester film comprising 5 to 5.0% by weight of a polyester having ethylene terephthalate as a main repeating unit, wherein said polyester contains a titanium compound which is soluble in a polymer. The metal element concentration, the phosphorus element concentration, and the acetaldehyde concentration in the film satisfy the following formula (1), and the total of the antimony metal element concentration and the germanium metal element concentration in the polyester is 15 pp.
m or less, and the polyester has a melting specific resistance at 290 ° C. of 1 × 10 ^{6 to} 5 × 10 ⁸ Ω · cm. 0.2 ≦ (AA + P) / Ti ≦ 20 (1) (In the above formula, AA is the concentration (ppm) of acetaldehyde contained in the film, and P is the phosphorus element of the phosphorus compound contained in the polyester. Concentration (ppm), Ti is the concentration of titanium metal element contained in polyester (ppm)
Is shown. ) 2. The polyester film according to claim 1, wherein the ratio of the titanium compound soluble in the polymer contained in the polyester is 4 to 50 ppm as a titanium metal element concentration. 3. The polyester film according to claim 1, wherein the concentration of acetaldehyde contained in the polyester film is 0.1 to 30 ppm. 4. The polyester film according to claim 1, wherein the titanium metal element concentration and the phosphorus element concentration in the polyester satisfy the following formulas (2) and (3). 0.2 ≦ Ti / P ≦ 4.5 (2) 10 ≦ Ti + P ≦ 85 (3) (In the above formula, Ti is the concentration (ppm) of the titanium metal element contained in the polyester, P represents the concentration (ppm) of the phosphorus element of the phosphorus compound contained in the polyester.) 5. The polyester wherein the total dicarboxylic acid component comprises terephthalic acid and isophthalic acid and the terephthalic acid is at least 82 mol%, the isophthalic acid is at most 18 mol%, and 100
2. The polyester film for laminating and processing a metal plate according to claim 1, wherein mol% is ethylene glycol and 0 to 18 mol% is a copolymerized polyester comprising a diol different from ethylene glycol. 6. The polyester wherein the total dicarboxylic acid component comprises terephthalic acid and 2,6-naphthalenedicarboxylic acid and the terephthalic acid is at least 82 mol% and the 2,6-naphthalenedicarboxylic acid is 18 mol%. 2. The metal plate lamination molding process according to claim 1, wherein 82 to 100 mol% of the total diol component is ethylene glycol and 0 to 18 mol% is a copolymerized polyester comprising a diol different from ethylene glycol. Polyester film. 7. The polyester film according to claim 1, wherein the polyester contains at least 5 ppm of at least one alkali compound selected from Na, K and Li as an alkali metal. 8. The biaxially oriented film has an intrinsic viscosity of 0.5 to
The polyester film for laminating and forming a metal plate according to claim 1, which has a range of 0.8. 9. The biaxially oriented film has a melting point of 210 to 25.
The polyester film for laminating and processing a metal plate according to claim 1, wherein the polyester film has a temperature range of 0 ° C and a glass transition point of 70 ° C or more. 10. The glycol component constituting the polyester comprises ethylene glycol and diethylene glycol, and 95% by mole of ethylene glycol.
The polyester film for laminating and processing a metal plate according to claim 1, wherein the content of diethylene glycol is 5 mol% or less. 11. The polyester film according to claim 1, wherein the terminal carboxyl group concentration of the biaxially oriented film is 40 eq / 10 ⁶ g or less. 12. The polyester film according to claim 1, wherein the refractive index in the thickness direction of the biaxially oriented film is in the range of 1.500 to 1.540.