JPH0726039A - Polyester film for lamination with metallic sheet - Google Patents

Abstract

PURPOSE:To provide a polyester film which is laminated with a metallic sheet to give a laminate excellent in fabricability, such as drawability, impact strength after being fabricated into a can, and the capability of preserving the perfume of the contents. CONSTITUTION:The polyester film is a biaxially oriented film made from a copolyester containing a lubricant of a mean particle diameter of 2.5mum or below. The copolyester is prepared from an acid component comprising 79.9-94.9mol% terephthalic acid, 5-20mol% isophthalic acid and 0.1-5mol% sulfonated aromatic dicarboxylic, maleic and/or fumaric acid and a glycol component mainly consisting of ethylene glycol and has a molecular weight corresponding to the intrinsic viscosity [eta] of 0.5-0.7.

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 metal plates, and more specifically, it shows excellent forming processability when it is laminated with a metal plate to perform can-making processing such as drawing. The present invention relates to a polyester film for metal sheet laminating and forming, which is resistant to cracking by an impact from the outside of the can even when subjected to heat treatment such as retort sterilization after the can, and which has excellent aroma retaining property of the contents.

[0002]

2. Description of the Related Art Metal cans are generally painted to prevent corrosion on the inside and outside, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention without the use of organic solvents The development of a method for obtaining the property has been advanced, and as one of them, coating with a thermoplastic resin film has been attempted. That is,
A method of making a can by laminating a thermoplastic resin film on a metal plate such as tin plate, tin-free steel, aluminum or the like and then making a can is under study. As the thermoplastic resin film, a polyolefin film or a polyamide film has been tried, but it does not satisfy molding processability, heat resistance and impact resistance.

On the other hand, a polyester film, particularly a polyethylene terephthalate film, has attracted attention as having balanced properties, and several proposals based on this have been made. That is, (A) Biaxially oriented polyethylene terephthalate film is laminated on a metal plate through an adhesive layer of low melting point polyester and used as a can-making material (Japanese Patent Laid-Open No. 56-10451).
(B) Amorphous or extremely low crystalline aromatic polyester film is laminated on a metal plate and used as a can-making material (JP-A-1-192545, JP-A-2-573).
No. 39) (C) A low orientation, heat-set, biaxially stretched polyethylene terephthalate film is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 64-22530).

However, none of these methods can obtain sufficient characteristics, and it has become clear that each of them has the following problems. Regarding (A), the biaxially oriented polyester film is excellent in heat resistance, but its moldability is insufficient, and whitening of the film (generation of minute cracks) and breakage occur in the can manufacturing process involving large deformation. As for (B), since it is an amorphous or extremely low crystalline aromatic polyester film, the moldability is good,
It is easily embrittled by post-processing such as printing after can-making and post-treatment such as retort sterilization, and is transformed into a film that is easily cracked by an impact from the outside of the can. Regarding (C), the effect is not exerted in the intermediate region between (A) and (B), but since the isotropy of the film surface is not guaranteed, it seems to be a can-making process (deep drawing process). When omnidirectional deformation is carried out, the workability of the film may be insufficient in a specific direction of the film.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of intensive studies to develop a polyester film for can manufacturing which does not have these problems, the present inventors have found that by using a specific copolymerized polyester as a raw material for the film, Molding processability,
The present invention has been accomplished by finding that a polyester film for can manufacturing which is excellent in impact resistance and can retain the aroma of the contents can be obtained.

[0006]

That is, the present invention is a biaxially oriented film comprising a copolyester containing a lubricant having an average particle size of 2.5 μm or less, wherein the copolyester is terephthalic acid 79 From 9 to 94.9 mol%, 5 to 20 mol% of isophthalic acid and 0.1 to 5 mol% of an aromatic dicarboxylic acid having a sulfonate group, maleic acid and / or fumaric acid, and mainly ethylene glycol. Is a polyester film for laminating and forming metal plates, which has a molecular weight of 0.5 to 0.7 and an intrinsic viscosity [η] of 0.5 to 0.7.

The copolyester used in the present invention has an acid component of terephthalic acid of 79.9 to 94.9 mol% (preferably 80 to 94.5 mol%) and isophthalic acid of 5 to 20 mol% (preferably 5 to 19). .5 mol%) and sulfonic acid group-containing aromatic dicarboxylic acid, maleic acid and / or
Or fumaric acid 0.1 to 5 mol% (preferably 0.5 to 3)
Mol%) and the glycol component is mainly ethylene glycol. If the content of this isophthalic acid component is less than 5 mol%, the moldability tends to deteriorate, while if it exceeds 20 mol%, the heat resistance and impact resistance tend to deteriorate. Further, when the aromatic dicarboxylic acid having a sulfonate group, maleic acid and / or fumaric acid component is less than 0.1 mol%, the impact resistance is insufficient, whereas when it exceeds 5 mol%, the moldability is poor. Noticeably worse.

The aromatic dicarboxylic acid having a sulfonate group is preferably a dicarboxylic acid represented by the following formulas (I) and (II).

[0009]

[Chemical 3]

(In the formula, M is an alkali metal, R ₁ and R ₂ are hydrogen atoms or-(CH ₂ ) _n --OH, and n is 2
Indicates a positive integer of ~ 4. )

[0011]

[Chemical 4]

(Wherein R ₁ and R ₂ are the same as defined above, and R ₃ , R ₄ , R ₅ and R ₆ represent the same or different groups selected from the group consisting of alkyl groups and aryl groups. .)

Preferred examples of the alkali metal represented by M in the above formula (I) include lithium, potassium and sodium. Further, in the above formula (II), R ₃ ~
The alkyl group of R ₆ is preferably one having 18 or less carbon atoms, and examples thereof include methyl, ethyl, propyl, butyl, dodecyl and stearyl. Further, as the aryl group of R _{3 to} R ₆ in the above formula (II),
It preferably has 6 to 12 carbon atoms, and examples thereof include phenyl, naphthyl, and biphenyl. These aryl groups may be substituted with, for example, a halogen atom, a nitro group or a lower alkyl group.

Specific examples of the aromatic dicarboxylic acid having a metal sulfonate group represented by the above formula (I) include 5
-Sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, and esters of these with alkylene glycols. Further, specific examples of the dicarboxylic acid having a quaternary phosphonium sulfonate represented by the above formula (II) include 5-tetrabutylphosphonium sulfoisophthalic acid, 5-ethyltributylphosphonium sulfoisophthalic acid and 5-tetraphenylphosphonium sulfo. Examples thereof include isophthalic acid, 5-phenyltributylphosphonium sulfoisophthalic acid, 5-ethyltriphenylphosphonium sulfoisophthalic acid and 5-butyltriphenylphosphonium sulfoisophthalic acid.
These may be used alone or in combination of two or more.

Examples of the alcohol component which can be used in combination with the ethylene glycol include diethylene glycol, propylene glycol, neopentyl glycol, butanediol, pentanediol, hexanediol and other aliphatic diols, polyethylene glycol, polypropylene glycol and other polyalkylene glycols. And the like can be preferably mentioned. These may be used alone or in combination of two or more.

The copolymerized polyester in the present invention preferably has a melting point in the range of 210 to 245 ° C. If the melting point of the polymer is less than 210 ° C, the heat resistance is poor, so that heating during printing after can-making cannot be endured. On the other hand, if the melting point of the polymer exceeds 245 ° C, the crystallinity of the polymer is too high and the moldability is impaired. Is not preferable.

Here, the melting point of the copolymerized polyester is measured by Du Pont Instruments 910.
According to a method of determining a melting peak at a temperature rising rate of 20 ° C./minute using DSC. The sample amount is about 20 mg.

The second-order transition point of the copolyester is preferably 60 ° C. or higher. Second-order transition point is 60 ° C
If it is lower than the above range, the polyester film has an insufficient aroma retaining property, which is not preferable.

Here, the second-order transition point of the polyester is measured by measuring the temperature distribution and tan δ with "Vibron direct reading dynamic viscoelasticity measuring instrument DDV-II type" manufactured by Toyo Baldwin Co., Ltd. The dynamic loss elastic modulus (E ″) is obtained, and the temperature at which the E ″ value becomes maximum is obtained as the second-order transition point. The measurement condition at this time is a driving frequency of 110 cps, and the temperature rising rate is 1 ° C./min. The measurement sample is prepared by forming a thin film having a width of 5 mm, a length of 20 mm and a thickness of 0.2 mm from the molten polymer,
Immediately after forming the film, the film is cooled and allowed to stand at room temperature for 3 days or more. At this time, if the film has uneven thickness, the measured values will be slightly different. Therefore, each of the five separately prepared measuring films is measured, and the average value of the five measured values is determined as the secondary transition point.

The copolyester in the present invention must have a molecular weight such that the intrinsic viscosity [η] of the film is in the range of 0.5 to 0.7. If this [η] is less than 0.5, the impact resistance will be insufficient, while if it is greater than 0.7, the moldability will be markedly poor, and this is not preferred.

The copolyester of the present invention contains a lubricant having an average particle size of 2.5 μm or less. The average particle size is preferably 0.05 μm or more, more preferably 0.1 μm or more. This lubricant may be inorganic or organic, but is preferably inorganic. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate, zirconium oxide and the like, and examples of the organic lubricant include silicone resin particles and crosslinked polystyrene particles. Both require that the average particle size is 2.5 μm or less. When the average particle size of the lubricant exceeds 2.5 μm, the coarse lubricant particles (for example, particles of 10 μm or more) in the portion deformed by processing such as deep drawing can are used as the starting point,
Pinholes may occur, or they may break, so
Not preferable. The lubricant preferably has a sharp particle size distribution and is preferably spherical particles.

The amount of the lubricant in the copolyester may be determined depending on the winding property and the deep drawing processability in the film manufacturing process. Generally, it is preferable to add a small amount of particles having a large particle size and a large amount of particles having a small particle size. For example, it is preferable to add about 0.05% by weight in the case of silica having an average particle size of 2.0 μm, and about 0.3% by weight in the case of titanium dioxide having an average particle size of 0.3 μm. Further, the film can be made opaque by intentionally adjusting the content of the lubricant. For example, a white film can be obtained by adding 10 to 15% by weight of titanium dioxide.

The copolyester of the present invention can be produced by a conventionally known method. For example, a terephthalic acid component, an isophthalic acid component, an aromatic dicarboxylic acid having a sulfonate group, a maleic acid and / or a fumaric acid component, and ethylene glycol are allowed to undergo an esterification reaction or a transesterification reaction in the presence or absence of a catalyst. It can be easily obtained by obtaining a bisglycol ester and / or an initial condensate thereof, and then subjecting the bisphenol ester and / or an initial condensate thereof to a polycondensation reaction in the presence of a polycondensation catalyst.
When an ester-forming derivative is used as the acid component, examples of the ester-forming derivative include lower alkyl ester, particularly dimethyl ester.

The catalyst used in the polycondensation reaction of the copolyester in the present invention is not particularly limited,
Preferable examples include antimony compounds, titanium compounds, germanium compounds and the like.

Preferred examples of the antimony compound include antimony trioxide and antimony acetate. Preferable examples of the titanium compound include titanium tetrabutoxide and titanium acetate. Also,
Examples of the germanium compound include (a) amorphous germanium oxide, (b) fine crystalline germanium oxide,
(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, and a solution in which (d) germanium oxide is dissolved in water are preferably exemplified. The amount of the germanium compound is preferably 40 to 200 ppm as the amount of germanium atom remaining in the copolyester, and further 60 to
150 ppm is preferred.

In the production of the copolyester, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber and an antistatic agent may be added if necessary.

The polyester film of the present invention can be produced by melting the above-mentioned lubricant-containing copolymerized polyester, discharging it from a die to form a film, biaxially stretching and heat setting. For example, in sequential biaxial stretching, the longitudinal stretching ratio is from 2.5 to 3.6 times, the transverse stretching ratio is from 2.7 to 3.6 times, and the heat setting temperature is 15 times.
It may be produced by selecting from the range of 0 to 220 ° C., preferably 160 to 200 ° C. and combining them.
The film preferably satisfies the following requirements (1), (2) and (3).

(1) The refractive index in the thickness direction of the film is 1.
It is preferably 505 or more and 1.550 or less, and more preferably more than 1.510 and 1.540 or less. When the refractive index is less than 1.505, the moldability becomes insufficient, while when it exceeds 1.550 (that is, when the orientation is excessively low), the structure becomes close to an amorphous structure, resulting in heat resistance. Is likely to be insufficient.

The refractive index in the film thickness direction is measured as follows. A polarizing plate analyzer is attached to the eyepiece side of Abbe's refractometer, and each refractive index is measured with a monochromatic NaD ray. Methylene iodide was used as the mount solution, and the measurement temperature was 25 ° C.

(2) The refractive index in the in-plane direction of the film is preferably 1.610 to 1.660 in all directions. The refractive index in the film surface direction is preferably as uniform as possible in all directions, and the refractive index value is 1.610.
When the thickness is out of the range of 1.660, the film has anisotropy, so that the moldability tends to deteriorate. The refractive index in the surface direction of the film is also measured by Abbe's refractometer in the same manner as above.

Further, the polyester film of the present invention may be a laminated film of two kinds of copolymerized polyesters having different copolymerization amounts and different copolymerization types, if necessary. In this case, each layer of the laminate may be polyester satisfying the requirements of the present invention, or only the outer layer portion may satisfy the requirements of the present invention.

The polyester film of the present invention preferably has a thickness of 6 to 75 μm. 10-75μ
m, particularly preferably 15 to 50 μm. If the thickness is less than 6 μm, breakage or the like tends to occur during processing, while if it exceeds 75 μm, it is uneconomical because of excessive quality.

As a metal plate for a can to which the polyester film of the present invention is stuck, a plate of tin plate, tin-free steel, aluminum or the like is suitable. The polyester film can be attached to the metal plate by the following method, for example.

The metal plate is heated above the melting point of the film, the films are laminated and then cooled, and the surface layer portion (thin layer portion) of the film in contact with the metal plate is made amorphous and adhered.

The film is pre-coated with an adhesive layer as a primer, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive such as an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used.

The polyester film of the present invention is subjected to a forming process, especially a deep-drawing process after it is bonded to a metal plate. The molded product, especially the can, is excellent in impact resistance and aroma retaining property. It is a thing. The detailed reason why the excellent impact resistance and the fragrance retaining property of the contents are developed is still unknown, but it is considered as follows when, for example, an aromatic dicarboxylic acid having a sulfonate group is copolymerized.

Since the copolyester constituting the film has a sulfonate group, a physical cross-linking effect (ion agglomeration) occurs between them to form a similar three-dimensional structure like a cured resin. Improved resistance to impact. Further, since the sulfonic acid base is hydrophilic, the entire film is hydrophilized, and as a result, the hydrocarbon compounds that are generally added as a flavoring agent to beverages are less likely to be adsorbed on the film, thus improving the aroma retention property.

[0038]

EXAMPLES The present invention will be further described below with reference to examples. In addition, "part" in an Example means a weight part. Moreover, the measurement of each characteristic value followed the following method.

(1) Intrinsic viscosity [η] It was measured at 30 ° C. using orthochlorophenol as a solvent.

(2) Formability of film, etc. The film was laminated on both sides of a 0.25 mm thick tin-free steel heated to 260 ° C., water-cooled to 150
A circular plate having a diameter of mm was cut out and deep drawing was performed in two steps using a drawing die and a punch to prepare a side surface seamless container having a diameter of 55 mm (hereinafter, abbreviated as a can). The following observations and tests were carried out on the cans, and the cans were evaluated according to the following standards.

(2-1) Molding workability-1 ○: The inner and outer surfaces of the film are processed without any abnormality, and no whitening or breakage is observed on the inner and outer surfaces of the can. Δ: Whitening is observed on the inside of the can and on the top of the can of the film. X: Film rupture is recognized in a part of the film inside and outside the can.

(2-2) Molding workability-2 ○: The inner and outer surfaces were processed without any abnormality, and the rust prevention test of the film surface inside the can (1% NaCl water was put in the can, the electrode was inserted, and the can body was Is used as an anode and a current value is measured when a voltage of 6 V is applied. In the following, abbreviated as ERV test) 0.1 mA
The following is shown. X: There is no abnormality in the film on both the inner and outer surfaces, but the current value is 0.1 mA or more in the ERV test, and pinhole-like cracks originating from the coarse lubricant are observed in the film when the energized portion is enlarged and observed.

(2-3) Impact resistance With respect to cans having good moldability, water was fully poured, and 10 bottles for each test were dropped from a height of 1 m onto the PVC tile floor surface. As a result of the test, ◯: 0.1 mA or less for all 10 pieces. (Triangle | delta): It was 0.1 mA or more about 1-5 pieces. X: 0.1 mA or more for 6 or more, or cracks of the film were already observed after dropping.

(2-4) Heat embrittlement resistance The cans, which had good moldability, were heated and held at 210 ° C. for 5 minutes and then subjected to the above impact resistance evaluation. It was 0.1 mA or less. (Triangle | delta): It was 0.1 mA or more about 1-5 pieces. ×: 0.1 mA or more for 6 or more, or cracks were already observed in the film after heating at 210 ° C. for 5 minutes.

(2-5) Fragrance Retaining A can which was well formed by deep drawing was filled with ten ciders or mineral water and sealed. After holding at 37 ° C. for 4 months, it was opened and sensory-tested for changes in aroma and taste.

⊚: There was no change in fragrance or taste. ◯: There were 1 or 2 fragrances and tastes that were slightly changed. Δ: There were 5 to 6 pieces with slightly changed scent and taste. X: Changes in aroma and taste of 10 bottles were recognized.

[0047]

Example 1 Production of Copolyester: Dimethyl terephthalate 87
3 parts, dimethyl isophthalate 92.15 parts, 5-sodium sulfoisophthalate dimethyl 7.4 parts, ethylene glycol 620 parts and manganese acetate 0.74 parts as an ester exchange catalyst, a stirrer, a rectification column and a methanol distillation condenser. The mixture was charged into a reactor equipped with, and heated while gradually raising the temperature from 130 ° C. to 230 ° C., methanol generated as a result of the reaction was distilled out of the system, and an ester exchange reaction was carried out. 3 hours after the reaction started, the internal temperature reached 230 ° C,
320 parts of methanol was distilled off. Here, 0.49 part of trimethyl phosphate as a stabilizer, 1.94 parts of spherical monodisperse silica having an average particle size of 1.5 μm as a lubricant, and 0.18 part of germanium dioxide as a polycondensation catalyst were added. The reaction mixture was transferred to a reactor equipped with a stirrer and a glycol distilling condenser, and heated from 230 ° C to 285 ° C.
The polycondensation reaction was performed while gradually raising the temperature to 0 ° C and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. The obtained polymer had a second-order transition point of 70 ° C and a melting point of 230 ° C.

Production of Film: The copolyester obtained as described above was melt extruded at 290 ° C. and rapidly solidified to obtain an unstretched film. Next, this unstretched film was longitudinally stretched 3.0 times at 100 ° C., and further from 100 ° C. to 1
While being heated to 50 ° C., the film was laterally stretched 3.2 times and then 20 times.
The film was heat set at 0 ° C. to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of this film.

[0049]

Example 2 Production of Copolyester: Same as Example 1 except that the composition of the dicarboxylic acid component was changed as shown in Table 1 and 0.34 part of titanium tetrabutoxide was used as the polycondensation catalyst instead of germanium dioxide. I went to. Table 1 shows Tg and Tm of the obtained polymer.

Production of film: Using the copolymerized polyester obtained as described above, the procedure of Example 1 was repeated to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of this film.

[0051]

Example 3 Production of Copolyester: Same as Example 1 except that the composition of the dicarboxylic acid component was changed as shown in Table 1 and 0.39 parts of antimony trioxide was used as the polycondensation catalyst instead of germanium dioxide. I went to. T of the obtained polymer
Table 1 shows g and Tm.

Production of film: Using the copolymerized polyester obtained as described above, the procedure of Example 1 was repeated to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of this film.

[0053]

Example 4 Preparation of Copolyester: The same procedure as in Example 1 was carried out except that 12.6 parts of dimethyl 5-tetrabutylphosphonium sulfoisophthalate was used in place of dimethyl 5-sodium sulfoisophthalate. T of the obtained polymer
Table 1 shows g and Tm.

Production of Film: Using the copolymerized polyester obtained as described above, the same procedure as in Example 1 was carried out to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of this film.

[0055]

Comparative Examples 1 to 4 Preparation of Copolyester: The same procedure as in Example 1 was carried out except that the molar ratio of the dicarboxylic acid component was changed as shown in Table 1. Table 1 shows Tg and Tm of the obtained polymer.

Production of Film: The same procedure as in Example 1 was carried out except that the heat setting treatment temperatures in Comparative Examples 3 and 4 were 160 ° C. and 220 ° C., respectively. Table 1 shows the evaluation results of these films.

[0057]

Comparative Examples 5 to 6 Preparation of Copolyester: The same procedure as in Example 1 was carried out except that the polycondensation reaction was adjusted so that the [η] of the film was the value shown in Table 1. Table 1 shows Tg and Tm of these polymers.
Shown in.

Production of film: The same procedure as in Example 1 was carried out to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of this film.

[0059]

Comparative Example 7 Example 1 was repeated except that 0.97 parts of spherical monodisperse silica having an average particle size of 2.8 μm was used as a lubricant. Table 1 shows the evaluation results of this film.

[0060]

Comparative Example 8 Production of Copolyester: As a dicarboxylic acid component,
873 parts of dimethyl terephthalate, dimethyl sebacate 1
The procedure of Example 1 was repeated except that 09.25 parts and 7.4 parts of dimethyl 5-sodium sulfoisophthalate were used. Table 1 shows Tg and Tm of this polymer.

Production of film: Using the copolymerized polyester obtained as described above, the procedure of Example 1 was repeated to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of this film.

[0062]

[Table 1]

The abbreviations in the table are as follows. TA: terephthalic acid IA: isophthalic acid SI: 5-sodium dimethyl sulfoisophthalate PI: 5-tetrabutylphosphonium dimethyl sulfoisophthalate EG: ethylene glycol Tg: secondary transition point Tm: melting point

[0064]

Example 5 Production of Copolyester: Dimethyl terephthalate 87
3 parts, dimethyl isophthalate 92.15 parts, dimethyl maleate 3.6 parts, ethylene glycol 620 parts and manganese acetate 0.74 parts as an ester exchange catalyst were provided with a stirrer, a rectification column and a methanol distillation condenser. The mixture was charged into a reactor and heated while gradually raising the temperature from 130 ° C. to 230 ° C. The methanol produced as a result of the reaction was distilled out of the system to carry out a transesterification reaction. The internal temperature reached 230 ° C. 3 hours after the start of the reaction, and 320 parts of methanol was distilled.

Here, 0.49 parts of trimethyl phosphate as a stabilizer, 1.94 parts of spherical monodisperse silica having an average particle size of 1.5 μm as a lubricant, and 0.18 part of germanium dioxide as a polycondensation catalyst were added.

This reaction mixture was transferred to a reactor equipped with a stirrer and a glycol distillation condenser, the temperature was gradually raised from 230 ° C. to 285 ° C., and atmospheric pressure was 1 mmHg.
The polycondensation reaction was performed while lowering the pressure to the high vacuum. The second-order transition point (Tg) of the obtained polymer was 70 ° C. and the melting point (T
m) was 230 ° C.

Production of polyester film: The copolyester obtained above was melt extruded at 290 ° C. and rapidly solidified to obtain an unstretched film. Next, this unstretched film was longitudinally stretched 3.0 times at 100 ° C., and further laterally stretched 3.2 times while raising the temperature from 100 ° C. to 150 ° C., followed by 2 times.
It was heat set at 00 ° C. to obtain a biaxially oriented film having a thickness of 25 μm. Table 2 shows the evaluation results of this film.

[0068]

Example 6 Production of Copolyester: The composition of the dicarboxylic acid component was changed as shown in Table 2, and titanium tetrabutoxide 0.3 was used instead of germanium dioxide as a polycondensation catalyst.
Example 5 was repeated except that 4 parts were used. Table 2 shows Tg and Tm of the obtained polymer.

Production of Polyester Film: A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in the production of the film of Example 5 except that the copolymer polyester obtained above was used. Table 2 shows the evaluation results of this film.

[0070]

Example 7 Preparation of Copolyester: Example except that the composition of the dicarboxylic acid component was changed as shown in Table 2 and 0.39 parts of antimony trioxide was used as the polycondensation catalyst instead of germanium dioxide. The same procedure as 5 was performed. Table 2 shows Tg and Tm of the obtained polymer.

Production of Copolyester: A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in the production of the film of Example 5 except that the copolymer polyester obtained above was used. Table 2 shows the evaluation results of this film.

[0072]

Example 8 Preparation of Copolymerized Polyester: The same procedure as in Example 5 was repeated except that 3.6 parts of dimethyl fumarate was used instead of dimethyl maleate. Tg and Tm of the obtained polymer
Is shown in Table 2.

Production of Polyester Film: A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in the production of the film of Example 5 except that the copolymerized polyester obtained above was used. Table 2 shows the evaluation results of this film.

[0074]

Comparative Examples 9 to 12 Production of Copolyester: The same procedure as in Example 5 was carried out except that the molar ratio of the dicarboxylic acid component was changed as shown in Table 2. Table 2 shows Tg and Tm of the obtained polymer.

Production of Polyester Film: Comparative Example 3,
4, the heat setting temperature was set to 160 ° C. and 22
The film was produced in the same manner as in Example 5 except that the temperature was 0 ° C. The evaluation results of the obtained film are shown in Table 2.

[0076]

[Comparative Examples 13 to 14] The intrinsic viscosity [η] of the film is shown in Table 2
The same procedure as in Example 5 was carried out except that the polycondensation reaction was adjusted so as to obtain the value shown in. Table 2 shows Tg and Tm of these polymers.

Production of polyester film: The same procedure as in the production of the film of Example 5 was carried out except that the copolymerized polyester obtained above was used to obtain a biaxially oriented film having a thickness of 25 μm. Table 2 shows the evaluation results of this film.

[0078]

Comparative Example 15 The procedure of Example 5 was repeated except that 0.97 part of spherical monodisperse silica having an average particle diameter of 2.8 μm was used as a lubricant. The evaluation results of the obtained film are shown in Table 2.

[0079]

Comparative Example 16 Production of Copolyester: As a dicarboxylic acid component,
873 parts of dimethyl terephthalate, dimetal sebacate 1
The procedure of Example 5 was repeated except that 09.25 parts and dimethyl maleate 3.6 parts were used. Table 2 shows Tg and Tm of the obtained polymer.

Production of polyester film: The same procedure as in the production of the film of Example 5 was carried out except that the copolymerized polyester obtained above was used to obtain a biaxially oriented film having a thickness of 25 μm. Table 2 shows the evaluation results of this film.

[0081]

[Table 2]

The symbols in the table are as follows.

TA: terephthalic acid IA: isophthalic acid MA: maleic acid FA: fumaric acid EG: ethylene glycol

[0084]

According to the present invention, it is possible to provide a polyester film for metal plate laminating and molding which is excellent in molding processability, impact resistance after can making, and aroma retaining property of the contents.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C08G 63/183 NNA 63/688 NNK B29K 67:00 B29L 7:00

Claims (4)

[Claims] 1. A biaxially oriented film comprising a copolyester containing a lubricant having an average particle diameter of 2.5 μm or less, wherein the copolyester is 79.9 to 9 terephthalic acid.
4.9 mol%, 5 to 20 mol% of isophthalic acid and 0.1 to 5 mol% of an aromatic dicarboxylic acid having a sulfonate group, maleic acid and / or fumaric acid, and a glycol component mainly composed of ethylene glycol. A polyester film for laminating and forming metal plates, which is characterized by having a molecular weight of 0.5 to 0.7 and an intrinsic viscosity [η] of 0.5 to 0.7. 2. The acid component of the copolyester is 80 to 94.5 mol% terephthalic acid and 5 to 19.5 isophthalic acid.
The polyester film for metal sheet laminating and processing according to claim 1, which comprises 0.5 to 3 mol% of an aromatic dicarboxylic acid having a sulfonate group, maleic acid and / or fumaric acid. 3. The polyester film for laminating and processing metal plates according to claim 1, wherein the aromatic dicarboxylic acid having a sulfonate group is a dicarboxylic acid represented by the following formulas (I) and (II). [Chemical 1] (In the formula, M represents an alkali metal, R ₁ and R ₂ represent a hydrogen atom or — (CH ₂ ) _n —OH, and n represents a positive integer of 2 to 4.) (Wherein R ₁ and R ₂ are the same as defined above,
R ₃ , R ₄ , R ₅ and R ₆ represent the same or different groups selected from the group consisting of alkyl groups and aryl groups. ) 4. The melting point of the copolyester is 210-2.
The polyester film for laminating and forming metal plates according to claim 1, 2 or 3, which has a second-order transition point of 45 ° C or higher and 60 ° C or higher.