JP3083707B2 - Polyester film for metal plate lamination processing - Google Patents

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 to a polyester film for laminating a metal plate and performing can forming such as drawing, and exhibiting heat resistance. The present invention relates to a polyester film for metal plate lamination molding capable of producing metal cans, such as beverage cans and food cans, having excellent properties, retort resistance, fragrance retention and the like.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion of the inner and outer surfaces, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, the use of organic cans is prevented. Development of a method for obtaining rust properties has been advanced, and as one of the methods, coating with a thermoplastic resin film has been attempted. That is,
Studies have been made on a method of laminating a thermoplastic resin film on a metal plate such as tinplate, tin-free steel, or aluminum, and then forming the can by drawing or the like. Polyolefin films and polyamide films have been tried as such thermoplastic resin films, but they do not satisfy all of the moldability, heat resistance and fragrance retention.

[0003] Accordingly, attention has been paid to polyester films, particularly polyethylene terephthalate films, because of their well-balanced properties, and several proposals based on these have been made. That is, (A) a biaxially oriented polyethylene terephthalate film is laminated on a metal plate via a low-melting-point polyester adhesive layer and used as a can-making material (JP-A-56-10451).
No. JP-A-1-192546). (B) Amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a material for can production (Japanese Patent Application Laid-Open Nos. 1-192545 and 2-573).
No. 39). (C) A low-orientation, heat-fixed, biaxially oriented polyethylene terephthalate film is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 64-22530).

[0004] However, the present inventors' studies have revealed that no satisfactory characteristics can be obtained in any case, and that each has the following problems. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and fragrance retention, but is insufficient in moldability and whitening of the film (generation of minute cracks) in canning with large deformation. Breakage occurs. Regarding (B), since it is an amorphous or extremely low-crystalline aromatic polyester film, the moldability is good, but the fragrance retention is inferior, and after printing after can-making, retort sterilization, etc. There is a possibility that the film may be easily embrittled by the treatment and further stored for a long period of time, and the film may be easily broken by an impact from the outside of the can. As for (C), the effect is not exhibited in the intermediate region between the above (A) and (B). However, the orientation has not yet reached the low orientation applicable to can processing, and the degree of deformation has not been improved. Even if processing could be performed in a small area, the subsequent printing and other retort treatments that sterilize the contents of the can make the film liable to be embrittled and may be transformed into a fragile film by an impact from the outside of the can. Same as B).

Further, Japanese Patent Application Laid-Open No. 5-339348 discloses a polyester film for laminating and processing a metal plate comprising a copolymerized polyester having a specific melting point, glass transition temperature and terminal carboxyl group concentration.
No. 79 proposes a polyester film for laminating and forming a metal plate on which a copolymerized polyester having a specific melting point and glass transition temperature is laminated. However, according to the study of the present inventors, when a can using these films is used for a beverage container, for example, depending on the type of beverage,
For example, a change in odor and taste as described in JP-A-55-23136 is sensed.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have conducted further intensive studies to develop a polyester film for can-making without these problems, and have reached the present invention.

[0007]

That is, according to the present invention, 99 to 60% by weight of a polyester (I) having a melting point of 210 to 245 ° C. and a glass transition temperature of 60 ° C. or more, and a melting point of mainly polybutylene terephthalate of 180% To 223 [deg.] C. and 1 to 40% by weight of the polyester (II), the following [M-1], [M-2], [M-3], [M-4] and The total content of one or more monomers selected from the compounds represented by [M-5] in a free state is 300 p
pm or less and phosphation in the polyester film
Has compound content (Pt) and transesterification catalytic ability
The content (Pn) of the metal compound is represented by the following (formula I) and
A polyester film for laminating a metal plate, characterized by satisfying (formula II) .

[0008]

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[0009]

## EQU3 ## -10 ≦ Pt−Pn ≦ 30 (Formula I) In the formula (I), Pt is a phosphorus compound remaining in the film
Is calculated from the following (formula II).
Has transesterification catalytic ability remaining in the whole film
Considerable total ability of metal compounds to inactivate phosphorus compounds
Concentration (mmol%).

[0010]

(Equation 4) Pn = (1/2) × M ₁ + M _Two + 2 × M _Three ... (Formula II) (Formula II) ₁ Is the ester exchange remaining in the film
Of monovalent metal compounds among the metal compounds having a catalytic activity
Concentration (mmol%), M _Two Is the S remaining in the film
Among the metal compounds having a terexchange catalytic ability Bivalent metallization
Concentration of compound (mmol%), M _Three Remains in the film
Tetravalent metal compounds having transesterification catalytic ability
It is the concentration (mmol%) of the metal compound. Where Pt,
Pn, M ₁ , M _Two , M _Three Concentration (mmol%)
To all the acid components in the polyester constituting the film
Things.

The polyester (I) in the present invention is a saturated polyester comprising a dicarboxylic acid component and a diol component, and is a copolymerized polyester having a melting point of 210 to 245 ° C. and a glass transition temperature of 60 ° C. or higher.

The dicarboxylic acid component includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid; cyclohexanedicarboxylic acid An alicyclic dicarboxylic acid such as an acid can be exemplified. As the diol component, HO— (CH ₂ ) _n —OH (where n = 2 to 1)
0) aliphatic diols (eg, ethylene glycol,
Butanediol, hexanediol, etc.); OH-CH ₂
—C (R) ₂ —CH ₂ —OH (where R = alkyl group having 1 to 4 carbon atoms), branched glycol (for example, neopentyl glycol and the like); diethylene glycol (DE
G); triethylene glycol (TEG); alicyclic diols (eg, cyclohexane dimethanol); and polyoxyalkylene glycols (eg, polyethylene glycol, polypropylene glycol). These can be used alone or in combination of two or more.

The proportion of the copolymer component of the polyester (I) depends on the components used, but as a result, the melting point is 210 to 24.
5 ° C., preferably 215-240 ° C., and the glass transition temperature of the polymer is 60 ° C. or higher, preferably 6 ° C.
It is a rate of 5 ° C. or more. If the melting point is less than 210 ° C., the heat resistance is inferior, so that it cannot withstand the heating in printing after can-making. On the other hand, when the melting point exceeds 245 ° C., the crystallinity of the polymer is too large, and the moldability is impaired. On the other hand, if the glass transition temperature is lower than 60 ° C., satisfactory scent retention cannot be obtained. As such a copolyester, a copolyester having a high glass transition temperature can be obtained,
Isophthalic acid copolymerized polyethylene terephthalate is particularly preferred.

On the other hand, the polyester (II) mainly composed of polybutylene terephthalate and having a melting point of 180 to 223 ° C. used in the present invention is a polybutylene terephthalate homopolymer or a copolymerized polyester mainly composed of polybutylene terephthalate. In the case of a copolymerized polyester, the copolymerized component may be a dicarboxylic acid component or a diol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid. Are aliphatic diols such as ethylene glycol and hexane diol; and alicyclic diols such as cyclohexane dimethanol. These can be used alone or in combination of two or more.

The proportion of the copolymer component of the polyester (II) depends on the components used.
The ratio is in the range of 0 to 223 ° C, preferably 200 to 223 ° C, and more preferably 210 to 223 ° C. When the melting point is lower than 180 ° C., the heat resistance is extremely poor. The melting point of the polybutylene terephthalate homopolymer is 223.
° C and it is difficult to obtain a polyester (II) having a higher melting point.

The melting points and glass transition temperatures of the polyesters (I) and (II) were measured by using DuPo.
A method of obtaining a melting peak and a glass transition temperature peak at a heating rate of 20 ° C./min using nt Instruments 910 DSC. The sample size is about 20m
g.

Further, the polyester (I) used in the present invention
And the intrinsic viscosity of the polyester (II) (measured at 30 ° C. using orthochlorophenol as a solvent) is 0.52 to 1.5.
It is preferably 0 dl / g, more preferably 0.60 to 1.00 dl / g. If the intrinsic viscosity is too low, it is difficult to obtain a sufficient strength and elongation, so that the molding processability and the impact resistance are poor, which is not preferable. On the other hand, if the intrinsic viscosity is too high, the melt viscosity will be high, and the shear heat generated in the extruder during film formation will increase, and a large amount of low molecular weight compounds will be by-produced due to thermal decomposition.

The polyester film of the present invention comprises 99 to 60% by weight of polyester (I) and polyester (II)
1 to 40% by weight. In the case of a film containing less than 1% by weight of polyester (II) and more than 99% by weight of polyester (I), when this film is used for a metal can, especially a metal can to which internal pressure is applied, the film is broken by an impact from the outside of the can. Easy and excellent quality cans cannot be obtained. When the content of the polyester (II) exceeds 40% by weight and the content of the polyester (I) is less than 60% by weight, the heat resistance of the film decreases and the impact resistance becomes insufficient.

Further, the polyester film of the present invention comprises:
[M-1], [M-2], [M-
3], the total content of one or more monomers selected from the compounds represented by [M-4] and [M-5] (hereinafter sometimes referred to as “monomers”) in a free state is the total amount At 300 ppm or less.

[0020]

Embedded image

Where [M-1] is terephthalic acid, [M-1]
-2] is bis (2-hydroxyethyl) terephthalate, [M-3] is mono (2-hydroxyethyl) terephthalate, [M-4] is monomethyl terephthalate, and [M-5] is monomethyl-mono (2-hydroxy Ethyl) terephthalate is shown.

When the total amount exceeds 300 ppm, the fragrance retention of the contents becomes poor when used in a metal can. In order to reduce the total amount of the monomers to 300 ppm or less, for example, in a polyester film obtained from the polyester (I) and the polyester (II) (hereinafter sometimes referred to as “polyester (I) (II)”) used in the present invention. Can be achieved by setting the content (Pt) of the phosphorus compound and the content (Pn) of the metal compound having transesterification catalytic activity in the ranges described below.

In addition, low molecular compounds other than the above monomers,
For example, the following [M-6] or [M- derived from polyester (II) mainly containing polybutylene terephthalate]
The compounds [7], [M-8], and [M-9] are not used in the present invention because of their low content in polyester film and low influence on fragrance retention compared to the monomers. The content is not particularly limited.

[0024]

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Here, [M-6] is dimethyl terephthalate, [M-7] is bis (4-hydroxybutyl) terephthalate, and [M-8] is mono (4-hydroxybutyl) terephthalate and [M-9]. Represents monomethyl-mono (4-hydroxybutyl) terephthalate, respectively.

The catalyst used for polymerizing the polyesters (I) and (II) of the present invention is not particularly limited, but preferred examples include an antimony compound, a titanium compound and a germanium compound.

Preferred examples of the antimony compound include antimony trioxide and antimony acetate. Preferred examples of the titanium compound include titanium tetrabutoxide, titanium acetate and the like. Examples of the germanium compound include (a) amorphous germanium oxide, (b) fine crystalline germanium oxide, and (c) a solution in which germanium oxide is dissolved in glycol in the presence of an alkali metal, an alkaline earth metal, or a compound thereof. ,
(D) A solution obtained by dissolving germanium oxide in water is preferred.

In the present invention, the total concentration (Pt) of the phosphorus compound in the polyester film and the ability of the metal compound having a transesterification catalytic activity (hereinafter sometimes referred to as "ester exchange catalyst") to deactivate the phosphorus compound. the total concentration (Pn), should be in the range satisfying the following (formula I) and (formula II), it is favorable preferable is a range satisfying the equation (III) and (formula II).

[0029]

-10 ≦ Pt−Pn ≦ 30 (Formula I)

[0030]

-5 ≦ Pt−Pn ≦ 15 (Formula III) In the formulas (I) and (III), Pt represents the total concentration (mmol%) of the phosphorus compound remaining in the film. , Pn
Represents the equivalent total concentration (mmol%) of the ability to deactivate the transesterified phosphorus compound remaining in the film as determined from the following (formula II).

[0031]

Pn = (1/2) × M ₁ + M ₂ + 2 × M ₃ (Formula II) In Formula (II), M ₁ is the concentration of the monovalent metal compound in the transesterification catalyst ( M ₂ represents the concentration of the divalent metal compound in the transesterification catalyst (mmol%), and M ₃ represents the concentration of the tetravalent metal compound in the transesterification catalyst (mmol%).

However, the concentrations (mmol%) of Pt, Pn, M ₁ , M ₂ and M ₃ are all based on the total acid components in the polyester constituting the film.

In the above formula (II), monovalent metal compounds of the transesterification catalyst include metal compounds such as lithium and sodium compounds, and divalent metal compounds of the transesterification catalyst include calcium, magnesium and manganese compounds. As the tetravalent metal compound among the metal compounds and transesterification catalysts, titanium compounds and the like can be mentioned, and all of these metal compounds having the transesterification catalytic ability remaining in the film are converted to the phosphorus compounds of the transesterification catalyst. Used to calculate the equivalent total concentration (Pn) of the ability to inactivate.

In the present invention, the value of Pt-Pn is -10
If the temperature is lower, the fragrance retention of the content may be insufficient when used as a metal can, and if it exceeds 30, the thermal stability of the polymer will deteriorate, and breakage and foreign matter will occur during film forming. Is unfavorable because the process condition may deteriorate or the moldability and impact resistance of a metal can may be insufficient.

Further, when the value of Pt-Pn is lower than -10, the deactivation of the catalyst by the phosphorus compound is weak, the decomposition of the polymer by the catalyst is promoted, and the amount of the low molecular compound in the polymer may be increased. Absent. On the other hand, Pt-P
If the value of n exceeds 30, an excessive amount of the phosphorus compound acts as a decomposition catalyst and also acts as a polymerization inhibitor during the polymerization reaction, so that the amount of the low-molecular compound in the polymer may increase, which is not preferable. .

The value of Pt-Pn is, for example, in the case of a polyester obtained by a polymerization method (direct weight method) without using a transesterification catalyst, the amount (mmol%) of the phosphorus compound added remaining in the film. In the case of a polyester obtained by a polymerization method using a transesterification catalyst (transesterification method), the phosphorus compound of the transesterification catalyst remaining in the film is determined from the amount of the phosphorus compound added remaining in the film. This is the amount obtained by subtracting a considerable amount of the ability to inactivate.

Among the low molecular weight compounds in the polyester film, the above-mentioned monomers particularly deteriorate the fragrance retention. However, a small amount of the low molecular weight compounds including these monomers is required to improve the fragrance retention. preferable. For example, when the film is extracted in ion-exchanged water at 121 ° C. for 2 hours, the amount of extraction per 1 inch ² of the film is 0.1 mg.
/ Inch ² or less, and 0.05 is m
g / inch ² or less is more preferable. Here, ion-exchanged water refers to water obtained by reducing ions in tap water with a cation-exchange resin and an anion-exchange resin, and then distilling.

In the present invention, the polyester (I) (I
I) is not limited by its manufacturing method. For example, in order to produce a copolymerized polyester mainly composed of polyethylene terephthalate as the polyester (I),
A method in which a reaction product obtained by subjecting terephthalic acid, ethylene glycol and a copolymer component to an esterification reaction is subjected to a polycondensation reaction to obtain a copolymerized polyester, or obtained by subjecting dimethyl terephthalate, ethylene glycol and a copolymer component to a transesterification reaction. A method in which the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymerized polyester can be preferably used.

The polyesters (I) and (II) may optionally contain an antioxidant, a heat stabilizer, a viscosity modifier, a plasticizer,
Other additives such as adhesion improvers, nucleating agents, lubricants, UV absorbers, antistatic agents and the like can be added.

The polyester film of the present invention can be produced by a conventionally known film-forming method. For example, the polyester film (I) and the polyester (II) are blended at a ratio within the range of the present invention, and are obtained by melt extrusion. It can be manufactured by biaxially stretching a stretched film and heat setting. The biaxial stretching conditions at this time include, for example, a stretching ratio in the longitudinal direction of 2.5 to 3.6 times and a stretching ratio in the transverse direction of 2.7.
It is preferable to select from a range of up to 4.0 times, and the stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. In addition, the heat setting temperature may be selected, for example, from the range of 150 to 220 ° C, particularly 160 to 200 ° C. At the time of film formation, the above-mentioned additives can be added, or at the time of polymerization, the film is formed by using polyester (I) and / or polyester (II) containing such additives. Additives can be added to the film.

This film has the following requirements (1) and (2):
It is preferable to provide (1) The refractive index in the film thickness direction is 1.505 or more and 1.550 or less, further 1.51
It is preferable to be more than 0 and 1.540 or less. If the refractive index is too low, the molding processability becomes insufficient, while if it is too high (in the case of an excessively low orientation), the structure becomes almost amorphous, and the heat resistance tends to be insufficient. (2) The refractive index in the plane direction of the film is 1.610 to 1.66 in all directions.
It is preferably 0. The refractive index in the film surface direction is preferably as uniform as possible in all directions. If the value of the refractive index is out of the above range, the anisotropy of the film becomes remarkable, so that the moldability tends to deteriorate.

Incidentally, the refractive index of the film was measured by attaching a polarizing plate analyzer to the eyepiece side of the Abbe refractometer,
The refractive index in the thickness direction and the refractive index in the plane direction are measured using the aD line. The mounting solution uses methylene iodide, and the measurement temperature is 25 ° C.

The preferred thickness of the polyester film of the present invention is from 6 to 75 μm, more preferably from 10 to 75 μm, especially from 15 to 50 μm. If the thickness is too thin, breakage or the like is likely to occur during processing, while if too thick, the quality is excessive and uneconomical.

The polyester film of the present invention can contain inert fine particles as a lubricant in order to impart lubricity to the film. Examples of such inert fine particles include inorganic particles such as silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate, and organic particles such as silicone resin particles. Of these, inorganic particles are preferable.

The above-mentioned inert fine particles have an average particle diameter of 2.
Preferably it is 5 μm or less. 2.5μ average particle size
If it exceeds m, coarse lubricant particles (for example, particles having a size of 10 μm or more) of a portion deformed by processing of a deep drawing can or the like become a starting point, and pinholes are generated or broken in some cases, which is not preferable.

The inert fine particles are preferably spherical monodisperse lubricants having a particle diameter ratio (major axis / minor axis) of 1.0 to 1.2 from the viewpoint of pinhole resistance. Examples of such fine particles include spherical silica, spherical silicone, and spherical calcium carbonate having an average particle diameter of 2.5 μm or less.

As for the amount of inert fine particles in the polyester film, it is generally preferable to add a small amount of particles having a large particle diameter and a large amount of particles having a small particle diameter. For example, an average particle size of 2.3 μm
In the case of spherical silica having a mean particle size of 1.5% by weight.
In the case of spherical silica of μm, it is preferable to add about 0.1% by weight. The film can also be made opaque by intentionally adjusting the content of inert fine particles. For example, spherical titanium oxide may be added in an amount of 5 to 20% by weight, preferably 10 to 1% by weight.
By adding 5% by weight, a white film can be obtained.

The inert fine particles are not limited to the above-mentioned externally added particles. For example, internal precipitated particles obtained by precipitating part or all of the catalyst used in the production of polyester in the reaction step can be used. It is also possible to use externally added particles and internally precipitated particles in combination.

As the metal plate for cans to which the polyester film of the present invention is bonded, a plate of tin, tin-free steel, aluminum or the like is suitable. The bonding of the polyester 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 bonded, and then rapidly cooled, and the surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. The 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 such as an epoxy-based adhesive, an epoxy-ester-based adhesive, an alkyd-based adhesive, or the like can be used.

When the polyester film of the present invention is bonded to a metal plate, if the film in contact with the content liquid has a composition satisfying the requirements of the present invention, the copolymerization amount, Polyester films having different copolymerization types may be laminated.

[0051]

The present invention will be further described below with reference to examples. In the examples, "parts" represents parts by weight. The measurement of each characteristic was performed according to the following method.

(1) Monomers A polyester film sample (500 mg) is dissolved in hexafluoroisopropanol (3 ml). 10 ml of methanol was added thereto to reprecipitate the sample, and the filtrate (filtrate) was used as it was, and the above monomers (terephthalic acid, bis (2-hydroxyethyl) terephthalate, mono (4-hydroxyethyl) terephthalate were subjected to liquid chromatography by liquid chromatography. , Monomethyl terephthalate, monomethyl-mono (2
-Hydroxyethyl) terephthalate) in the film was measured, and the total content [ppm] of the monomers in a free state was determined.

(2) Laminability The polyester film was bonded to a tin-free steel plate heated to a temperature equal to or higher than the melting point of polyester, and then cooled to obtain a coated steel plate. The lamination property of this coated steel sheet was determined according to the following criteria. (A) Criteria for determination of bubbles and wrinkles ：: No bubbles and wrinkles are observed. Δ: Bubbles and wrinkles are observed at two or three places per 10 m in length. X: Many bubbles and wrinkles are observed. (B) Criteria for determining heat shrinkage 収縮: Shrinkage is less than 2%. Δ: Shrinkage rate is 2% or more and less than 5%. X: Shrinkage rate is 5% or more. The tin-free steel plate on which the above-mentioned polyester film was laminated was formed into a side-seamless container (hereinafter abbreviated as can) using a die and a punch. The following observations and tests were performed on the cans, and the cans were evaluated according to the following standards.

(3) Deep drawing workability -1 ○: The film was processed without any abnormality, and no whitening or breakage was observed in the film on the inner and outer surfaces of the can. Δ: Whitening is observed at the top of the film can. X: Film breakage is observed in a part of the film.

(4) Deep drawing processability-2 ○: Rust prevention test of film inside can (1% NaCl water was put in the can, electrode was inserted, and the can was used as anode) The current value when a voltage of 6 V is applied is measured.
In the ERV test, the value is 0.2 mA or less. ×: No abnormality was found in the film, but the current value was 0.2 mA or more in the ERV test. When the energized portion was observed under magnification, pinhole-shaped cracks starting from the coarse lubricant particles were observed in the film.

(5) Impact cracking resistance Cans with good deep drawability were filled with water and 10 pieces of each test were dropped from a height of 1 m onto a PVC tile floor for each test. As a result,: 0.1 mA or less for all 10 samples. C: 0.1 mA or more for 1 to 5 pieces. X: The film was 0.1 mA or more for 6 or more pieces, or cracks of the film were already observed after dropping.

(6) Heat Embrittlement Resistance The can which had been subjected to good deep drawing was heated and maintained at 210 ° C. for 5 minutes, and then subjected to the above-described impact cracking resistance evaluation. .1 mA or less. C: 0.1 mA or more for 1 to 5 pieces. ×: The film was 0.1 mA or more for 6 or more pieces, or cracks of the film were already observed after heating at 210 ° C. for 5 minutes.

(7) Retort Resistance The cans having good deep drawing properties were filled with water and retorted at 130 ° C. for 1 hour in a steam sterilizer, and then stored at 50 ° C. for 30 days. After dropping 10 cans for each test from a height of 1 m onto a PVC tile floor, an ERV test was performed in the cans. The results were as follows: A: 0.1 mA or less for all 10 cans. C: 0.1 mA or more for 1 to 5 pieces. X: The film was 0.1 mA or more for 6 or more pieces, or cracks of the film were already observed after dropping.

(8) Rust Prevention A 5% acetic acid aqueous solution was fully poured into cans having good deep drawing and kept at 50 ° C. for 7 days. No rust was observed for 10 pieces. Δ: For 1 to 5, rust was observed. ×: Rust generation was observed for 6 or more pieces.

(9) Perfume Retention A can having good deep drawing was filled with 10 pieces of the above-described ion-exchanged water and sealed. After being kept at room temperature for one month, the package was opened and subjected to a sensory test for changes in aroma and taste. ○: No change in flavor and taste was observed. Δ: 3 to 4 pieces slightly changed in flavor and taste. D: Five or more changes in flavor and taste were observed.

(10) Total Dicarboxylic Acid Concentration About 10 mg of a sample was dissolved in 0.5 ml of a mixed solvent of CDCl ₃ / CF ₃ COOD (1: 1), and then 1H-NMR was performed using an FT-NMR / Hitachi R-1900 type machine. Was measured and determined from the integrated value of each component.

(11) Phosphorus Compound Concentration The sample was heated to 240 ° C. and melted to form a circular disk, and the phosphorus compound concentration was measured by X-ray fluorescence analysis.

(12) Concentration of metal compound having transesterification catalytic activity The sample was wet-decomposed and quantified by IPC analysis.

Examples 1 to 6 and Comparative Examples 1 to 5 Copolymerized polyethylene terephthalate obtained by copolymerizing the components shown in Table 1 as polyester (I) (having an intrinsic viscosity of 0.6
4, containing 0.3% by weight of titanium dioxide having an average particle diameter of 0.3 μm and having a Pt-Pn value of 10;
) And polybutylene terephthalate (having a Pt-Pn value of 0) as polyester (II);
T) or a copolymerized polybutylene terephthalate (having a Pt-Pn value of 0; hereinafter abbreviated as copolymerized PBT) obtained by copolymerizing the components shown in Table 1 at a ratio shown in Table 1 and 280 The mixture was melt-extruded at ℃ and quenched on a cooling drum to obtain an unstretched film. Next, the unstretched film was stretched in the machine direction, then stretched in the transverse direction, and then heat-set to obtain a biaxially stretched film having a thickness of 25 μm. However, Comparative Example 1 is an example using only polyester (I), Comparative Example 2 is an example using only PBT, and Comparative Example 3 is an example using only copolymerized PBT.

Comparative Example 6 A biaxially stretched film was obtained in the same manner as in Example 1 except that a copolymerized PET having a Pt-Pn value of -29 was used as the polyester (I).

Comparative Example 7 A biaxially stretched film was obtained in the same manner as in Example 1, except that a copolymerized PET having a Pt-Pn value of 50 was used as the polyester (I).

Example 7 Polyester (for an adhesive layer to a metal plate) in which the same copolymerized PET and PBT as in Example 1 were blended in the ratio shown in Table 1 and the copolymerized PET used in Example 1 The same polyester (for the contact layer with the content liquid) is dried and melted in the usual manner, then co-extruded from dies adjacent to each other, fusion-laminated, and quenched on a cooling drum to form an unstretched laminated film. Obtained. Next, this unstretched laminated film is
Stretched 3.0 times in the machine direction at 100 ° C.
The film was transversely stretched 3.2 times in the transverse direction while the temperature was raised to 50 ° C., and then heat-set at 200 ° C. to obtain a biaxially stretched film having a thickness of 25 μm. The thickness of the polyester layer for the adhesive layer with the metal plate was 20 μm, and the thickness of the polyester layer for the contact layer with the content liquid was 5 μm.

Example 8 One surface of a biaxially stretched film obtained in the same manner as in Example 2 was coated with a primer of an epoxy-based adhesive, and the coated surface was used as a bonding surface to bond the film to a metal plate. . The thickness of the primer coat layer was 0.7 μm.

Table 1 shows the film qualities of the above Examples 1 to 8 and Comparative Examples 1 to 7, and Table 2 shows the laminating properties, deep drawability and various evaluation results of the cans obtained by deep drawing. Show. In Table 1, PET indicates polyethylene terephthalate, PBT indicates polybutylene terephthalate, IA indicates isophthalic acid, and AA indicates adipic acid. Further, Tm indicates a melting point, and Tg indicates a glass transition temperature. Incidentally, the amount of the monomers is based on the terephthalic acid, bis (2-hydroxyethyl) terephthalate, mono (2-hydroxyethyl) terephthalate, monomethyl terephthalate and monomethyl-mono (2-hydroxyethyl) terephthalate in the polyester constituting the film. Is a value obtained by measuring the total amount of the contents in the free state by the above-described quantitative method. The Pt-Pn value was determined by measuring the total dicarboxylic acid concentration, the phosphorus compound concentration, and the concentration of a metal compound having a transesterification catalytic activity in the polyester constituting the film, and determining the total phosphorus compound concentration (Pt) in the film and the ( Pn determined by equation II)
And the value obtained from

[0070]

[Table 1]

[0071]

[Table 2]

As is clear from the results shown in Table 2, the polyester film of the present invention has good laminating properties and deep drawability, and the can using the polyester film of the present invention has impact cracking resistance and heat embrittlement resistance. It has good retort resistance and rust resistance, and is particularly excellent in fragrance retention.

[0073]

Industrial Applicability The polyester film for laminating and processing metal sheets of the present invention has good moldability, heat resistance, impact resistance, retort resistance, rust resistance, and adhesiveness, and also has excellent terephthalic content in the film. Content of one or more monomers selected from acids, bis (2-hydroxyethyl) terephthalate, mono (2-hydroxyethyl) terephthalate, monomethylterephthalate and monomethyl-mono (2-hydroxyethyl) terephthalate in a free state Is 300 ppm or less in total, so that the fragrance retention is extremely excellent. Therefore, it is suitable for deep-drawn metal cans, especially beverage cans and food cans.

Continuation of the front page (56) References JP-A-5-320378 (JP, A) JP-A-5-320377 (JP, A) JP-A-5-222216 (JP, A) JP-A-5-186613 (JP) JP-A-5-186612 (JP, A) JP-A-5-156040 (JP, A) JP-A-5-339349 (JP, A) JP-A-6-179742 (JP, A) 3-174441 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/18 B32B 15/08 C08L 67/02 B21D 51/18

Claims (2)

(57) [Claims] 1. A polyester (I) having a melting point of 210 to 245 ° C. and a glass transition temperature of 60 ° C. or more, 99 to 60% by weight.
And a melting point mainly composed of polybutylene terephthalate is 1
A polyester film consisting of 1 to 40% by weight of polyester (II) at 80 to 223 ° C, wherein the following [M-1], [M-2], [M-
3], the total content of one or more monomers selected from the compounds represented by [M-4] and [M-5] in a free state is 300 ppm or less , and polyester
The content (Pt) of the phosphorus compound in the film,
(Pn)
Characterized by satisfying the following (formula I) and (formula II) . Embedded image -10 ≦ Pt−Pn ≦ 30 (Formula I) In the formula (I), Pt is the total concentration of the phosphorus compound remaining in the film (mm
Mol%) and Pn in the film determined from the following (Formula II)
Of metal compounds having transesterification catalytic activity remaining in
Total concentration (millimolar) of the ability to inactivate
%). ## EQU2 ## Pn = (1/2) × M ₁ + M ₂ + 2 × M ₃ (Formula II) In Formula (II), M ₁ has a transesterification catalytic activity remaining in the film.
Concentration of monovalent metal compound (millimolar
%), M ₂ is the transesterification catalytic activity remaining in the film
The concentration (mmol%) of the divalent metal compound among the metal compounds having the following formula: M ₃ has a transesterification catalytic activity remaining in the film
Concentration of the tetravalent metal compound (mole
%). However, the concentrations of Pt, Pn, M ₁ , M ₂ and M ₃
(Mmol%) are the polye
For all acid components in the stell. 2. A film is heated at 121.degree.
The amount of extraction when the time extraction process is performed is 0.1 mg / inch
^The polyester film for laminating and processing a metal plate according to claim 1, which is ² or less.