JP2002178471A - Polyester film for laminating metal plate, metal plate and metal vessel formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film suitable for a metallic can laminated by the film, in which heat laminating properties for a metal plate, formability of the can, especially higher-order workability such as draw forming and squeeze forming is excellent and furthermore taste keeping properties and flavor keeping properties of contents are excellent. SOLUTION: A laminated film of at least two or more layers is comprised of laminating both a polyester layer A and a polyester layer B. (1) The layer A consists of both 94-45 wt.% PBT or polyester (I) comprising this as the main constituent and 10-55 wt.% PET or polyester (II) comprising this as the main constituent. Ester exchange index (I) and (II) contained in the layer A is 1-10%. (2) The layer B consists of 25-55 wt.% (I) and 75-45 wt.% (II) and the ester exchange index of (I) and (II) contained in the layer B is <=7%. (3) The layer A is a film having a melting point of (I) at 200-223 deg.C and the layer B is the film having a melting point of (II) at 230-256 deg.C.

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 a metal plate, a film-laminated metal plate and a metal container using the same, and more particularly, to a film-laminated metal plate obtained by laminating a metal plate.
The present invention relates to a polyester film that can be used for drawing or ironing, and a film-laminated metal plate and a metal container using the same.

[0002]

2. Description of the Related Art Conventionally, a solvent type paint mainly composed of a thermosetting resin has been applied to the inner and outer surfaces of a metal can for the purpose of preventing corrosion. However, solvent-type paints require heating at a high temperature to form a coating film, and a large amount of solvent is generated at that time, and thus there is a problem in terms of work safety and the environment. Therefore, recently, as a corrosion prevention method without using a solvent, coating of a metal plate with a thermoplastic resin has been proposed. Among thermoplastic resins, polyester is particularly excellent in workability and heat resistance. The development of a film for plate lamination is in progress.

As a method of coating a film on a metal plate, there are a method in which a thermoplastic resin is melted and extruded directly onto a metal, and a method in which a thermoplastic resin film is thermocompressed directly or through an adhesive. Among them, the method using a thermoplastic resin film is easy to handle the resin and excellent in workability,
In addition, it is an effective method because the resin film has excellent uniformity in film thickness. In addition, since the method using an adhesive has environmental and cost problems, a method of directly thermocompression bonding a film is advantageous and attracts attention.

[0004] A metal can coated with a thermoplastic resin film is formed by laminating a thermoplastic resin film on a metal plate such as a steel plate or an aluminum plate (including a plate subjected to a surface treatment such as plating). Manufactured.
The thermoplastic resin film used in such applications has good heat laminating properties with a metal plate and excellent moldability of the can, that is, peeling, cracking, pinholes, etc. of the film at the time of molding the can. Various properties are required at the same time, such as no generation of odor, no embrittlement during printing after can molding, retort sterilization treatment and long-term storage, and excellent content and flavor retention of the contents.

[0005] As such a polyester film for metal plate lamination, there are several methods such as mixing or copolymerizing other components for the purpose of imparting heat lamination properties and improving the moldability of a can. Proposed. For example,
(A) Polyethylene terephthalate (PET) copolymerized with other components is disclosed in JP-B-8-19245, JP-B-8-19246, Japanese Patent No. 2528204, and the like. A blend of 99 to 60% by weight of a copolymerized polyester having ethylene terephthalate as a main repeating unit and a polybutylene terephthalate (PBT) or a copolymer thereof at 1 to 40% by weight at a temperature of from 245 to 245 ° C is disclosed in Japanese Patent No. 2851468. These are disclosed in Japanese Unexamined Patent Publication No. Hei 5-186612 and Japanese Unexamined Patent Publication No. Hei 5-186613, respectively. Further, (c) the melting point is 21
99 to 50% by weight of a copolymer polyester containing ethylene terephthalate as a main repeating unit at 0 to 245 ° C and P
In a multilayer film including a layer containing 1 to 50% by weight of BT or a copolymer thereof, the transesterification rate is 3%.
% Or more (Japanese Patent Laid-Open No. 10-315412,
Japanese Patent Application Laid-Open No. H11-207909) is disclosed.

However, in (a), the thermal lamination property and moldability are improved by copolymerizing PET and lowering the melting point and lowering the crystallization, but the embrittlement occurs during the heat treatment after can molding and the retort sterilization treatment. There is a problem that impact resistance is reduced.

In (b), by blending a PBT-based resin, the heat laminating property and the embrittlement and impact resistance of the can are improved, but the heat laminating property and adhesion to metal are not sufficient. In particular, high-order formability such as drawing and ironing was not sufficient.

In (c), the copolymerized PET is used as a surface layer,
There has been proposed a film in which a mixture of copolymerized PET and polyester mainly comprising PBT is laminated on a lower layer, and a transesterification index between the polyesters in the lower layer is defined. However, there is a problem that it is likely to be embrittled with time after retorting, which is considered to be based on the properties of the copolymerized PET of the surface layer, and the impact resistance is reduced. In addition, the protective properties of the contents, the resistance to retort whitening, and the like have not been improved in connection with the problem that the heat and humidity at high temperatures are likely to decrease due to the low crystallinity.
In the lower layer, PBT or PB copolymerized with adipic acid is used.
Since only 50% or less of the polyester mainly composed of T is added, and its transesterification rate is 3% or more and 5% or more, which is higher in the examples, the film has low crystallinity, and the film is processed. Although it has improved heat resistance and adhesion to metals, it has low retort resistance and low barrier properties, and is comprehensive in terms of heat resistance, impact resistance, and content protection properties that are indispensable when used as cans. It was still unsatisfactory due to its unique characteristics.

On the other hand, the present inventors have previously described PB
T or a polyester (A) 90-4 mainly composed of T
A biaxially stretched film composed of 5% by mass and 10 to 55% by mass of PET or polyester (B) containing the same as a main component has been proposed (JP-A-9-194604, JP-A-10-110046). ). The film proposed here has a high degree of crystallinity and can be thermocompression-bonded at a relatively low temperature, and the obtained laminated metal plate has excellent workability. Further, even after retort sterilization and storage for a long time, the film is not embrittled and has excellent impact resistance.

However, recently, there has been an increasing demand for an increase in the speed of cans, an increase in the capacity of the can, and a reduction in the thickness of the can, and the ratio of deformation of the metal during drawing and ironing has been further increasing. Also, since the friction with the processing jig is further increased, even if the above-mentioned film is used in the body of the can which is particularly severely deformed, subtle fluctuations in the manufacturing conditions of the laminated metal sheet and the forming processing conditions of the final can. In some cases, problems such as whitening of the film and generation of microcracks newly occurred. It was also assumed that the residual strain of the film caused by the increase in the processing ratio caused peeling due to partial adhesion failure to the metal, and that there was concern about the protection of the contents. In addition, the sticking between the drawing and ironing jig and the film at the time of canning occurs, and the problem that the body of the can is broken at the time of can forming has been pointed out. It has come to be desired.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide excellent heat lamination properties with a metal plate, high moldability of cans, especially high-order workability such as drawing and ironing, and furthermore, preservation of the content. An object of the present invention is to provide a polyester film for metal lamination, a laminated metal plate, and a metal container using the same, which are suitable for a film-laminated metal can excellent in fragrance.

[0012]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that two crystals having different crystallinities have different properties.
A polyester film in which at least two or more polyester layers each having a specific mixing ratio of polyester (I) mainly composed of PBT and polyester (II) mainly composed of PET is laminated, and the polyester (I ) And polyester (II) by using a polyester film in which the degree of transesterification reaction is adjusted to a specific range, it is excellent in heat lamination properties with metal, moldability of cans, especially drawing and ironing. Further, the present inventors have found that a metal container excellent in impact resistance and flavor retention can be manufactured and provided, and have reached the present invention.

That is, the gist of the present invention is as follows. A laminated film of at least two layers obtained by laminating a polyester A layer and a polyester B layer, wherein the polyester A layer is composed of polybutylene terephthalate or 90 to 45% by mass of a polyester (I) mainly containing the same, and polyethylene. A terephthalate or 10-55% by mass of polyester (II) containing the same as a main component,
The transesterification index of the polyesters (I) and (II) in the layer is 1 to 10%, and the polyester B layer is the polyester (I) 25 to 55
% Of polyester (II) and 75 to 45% by weight of polyester (II), wherein polyester (I) and polyester (II) in layer B
Has a transesterification index of 7% or less, and each of the polyester A layer and the polyester layer B is 200 to 223.
A film for laminating a metal plate, wherein the film has a melting point of the polyester (I) at ℃ and the melting point of the polyester (II) at 230 to 256 ° C.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the polyester (I) mainly composed of PBT is PBT or a copolymer of PBT and other components. In the polyester layers A and B blended with the polyester (II), the melting point of the polyester (I) Needs to be 200 ° C. or higher and a melting point of PBT of 223 ° C. or lower. If the melting point is lower than 200 ° C., the crystallinity of the polyester is low, and as a result, the heat resistance of the film is lowered. When using the copolymerized PBT, the copolymerization ratio may be selected so that the melting point is within the above range, and the copolymerization ratio and the structure of the component to be copolymerized may be selected. Butanediol is preferably at least 80 mol%, particularly preferably at least 90 mol%. If the amount of 1,4-butanediol is less than 80 mol%, the crystallinity, particularly the crystallization rate, is reduced, and the impact resistance and barrier properties after retort treatment are reduced.

The copolymerization component is not particularly limited. Examples of the acid component include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, and the like.
Azelaic acid, dodecane diacid, dimer acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, dicarboxylic acids such as cyclohexanedicarboxylic acid, 4-hydroxybenzoic acid, ε-caprolactone, lactic acid and the like. No. Further, as the alcohol component, ethylene glycol, diethylene glycol,
1,3-propanediol, neopentyl glycol,
Examples include 1,6-hexanediol, cyclohexanedimethanol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene oxide adducts of bisphenol A and bisphenol S. In addition, trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, pentaerythritol, etc.
A small amount of a functional compound or the like may be used. Two or more of these copolymer components may be used in combination.

In the film of the present invention, examples of the polyester (II) mainly composed of PET include PET and those obtained by copolymerizing PET with other components. In B, the melting point of the polyester (II) is 230 to 256 ° C.
And preferably 236 to 2
It is in the range of 56 ° C. More preferably, 246 to 25
It is in the range of 6 ° C. When the melting point is less than 230 ° C., the crystallinity is reduced, whitening or white spots are generated after the retort treatment, or the impact resistance after the retort treatment is reduced. When the melting point exceeds 256 ° C., the heat laminating property decreases. In particular, when the melting point of polyester (II) is 246 ° C. or more, heat resistance, impact resistance after retort treatment, and impact resistance after long-term storage are improved. In addition, it is effective in reducing a fusion trouble with a jig during can processing and a break trouble during processing of a can body.

The component which can be copolymerized with PET is not particularly limited, and examples thereof include the same compounds as polyester (I).

The limiting viscosity of the raw material polyester used for producing the polyester film of the present invention is 0.6 to 1.6 for the polyester (I), and 0.6 for the polyester (II).
Is preferably 0.5 to 0.9, and the intrinsic viscosity after melt mixing is 0.6 to 1.0, particularly preferably 0.75 to 1.0. When the intrinsic viscosity is less than the above range, the practical performance of the film is insufficient, and in particular, the film may be broken or cracked during high-order processing of the can. Further, when the intrinsic viscosity exceeds the above range, the load applied to the resin melt extruder in the film production process becomes large, and the production speed has to be sacrificed, or the melt residence time of the resin in the extruder is reduced. If the length is too long, the reaction between the polyester resins proceeds too much, which causes deterioration of the film properties, and consequently lowers the physical properties of the metal plate of the laminated film. In addition, those having a high intrinsic viscosity have a long polymerization time and a long polymerization process, which may be a factor to increase the cost.

The method of polymerizing the raw material polyester is not particularly limited. For example, it can be polymerized by a transesterification method, a direct polymerization method or the like. As a transesterification catalyst, Mg,
Examples include oxides and acetates of Mn, Zn, Ca, Li, and Ti. As the polycondensation catalyst, Sb, Ti, G
e. Compounds such as oxides and acetates. Since the polyester after polymerization contains monomers and oligomers, by-products such as acetaldehyde and tetrahydrofuran, it is preferable to carry out solid-phase polymerization at a temperature of 200 ° C. or more under reduced pressure or an inert gas flow.

In the polymerization of polyester, if necessary, additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber,
An antistatic agent or the like can be added. As the antioxidant, for example, a hindered phenol compound, a hindered amine compound, or the like, as the heat stabilizer, for example, a phosphorus compound, and as the ultraviolet absorber, for example, a benzophenone compound, a benzotriazole compound, or the like. Can be mentioned. Further, as a reaction inhibitor between different polyesters, it is preferable to add a conventionally known phosphorus compound before, during or after the polymerization. In particular,
More preferably, it is added at the end of melt polymerization before solid phase polymerization.

In the present invention, the polyester (I) and the polyester (II) in the polyester A layer are (I) /
(II) = 90-45 / 10-55 (% by mass), preferably (I) / (II) = 80-50 / 20-50 (% by mass), more preferably (I) / (II) = 70 ~ 55 /
It needs to be 30 to 45 (% by mass). Also,
The polyester (I) and the polyester (II) in the polyester B layer are (I) / (II) = 25-55 / 75-
45 (% by mass), more preferably (I) / (II) = 3
It is necessary to be 0-55 / 70-45 (mass%).

When the content of the polyester (I) in the polyester A layer exceeds 90% by mass, the properties of the polyester (I) having high crystallinity are remarkably exhibited, and the moldability of the film-laminated metal plate is reduced, and The impact property also worsens. In addition, the adhesion to metal is also reduced. When the content of the polyester (I) is less than 45% by mass, the crystallization rate is reduced, and the physical properties after the retort treatment are reduced. In addition, the adhesion to metal is also poor. In particular, when the content of the polyester (I) is in the range of 70 to 55% by mass, the formability, impact resistance, adhesion to metal, and physical properties after retort treatment of the laminated metal sheet are balanced, which is a preferable embodiment. .

When the polyester (I) in the polyester B layer exceeds 55% by mass, the heat resistance is reduced, and when performing high-speed drawing and ironing of a metal plate, friction with a processing jig increases, Moldability decreases. In addition, the quality of the final product decreases accordingly. In addition, the corrosion resistance of the can and the flavor retention of the content deteriorate. If the content of the polyester (I) is less than 25% by mass, the ability to follow the deformation during molding of the can deteriorates, causing whitening and microcracking of the film, and the corrosion resistance and the protection of the contents on the inner surface of the can deteriorate. On the outer surface, the glossiness of the printed pattern is reduced, or a problem occurs in corrosion resistance. In particular, when the content of the polyester (I) is in the range of 30 to 55% by mass, the moldability of the laminated metal sheet, the flavor retention of the content, and the balance of the physical properties after the retort treatment are preferable.

The film of the present invention has a polyester (I) and a polyester (II) in the polyester A layer which have a transesterification index of 1 to 10% (the measuring method is described in Examples), more preferably 2 to 7%. It is necessary to be. The transesterification rate of layer A increases, and polyester (I) and (I)
If the randomization of the components of I) progresses,
%, The melting point of the film decreases, and the heat resistance decreases. Also, the protection of the contents is reduced. On the other hand, when the content is less than 1%, the polyethylene terephthalate component retains its properties, and the highly crystalline PBT is present in the A layer. descend. On the other hand, the transesterification index between the polyester (I) and the polyester (II) in the polyester B layer must be 7% or less, preferably 5% or less. When the transesterification rate of the layer B exceeds 7%, the melting point of the film decreases, and the metal plate becomes easily adhered to the processing jig when forming the metal plate into the can, the friction increases, and the can surface becomes uneven. In the worst case, the metal may break during the forming process.

The method for adjusting the transesterification index within the above range is not particularly limited, but the melting temperature of the polyesters (I) and (II) in the extruder, the degree of kneading in the extruder, the degree of kneading in the extruder, and the like. Methods such as adjusting the residence time are exemplified.
The method of melt mixing is not particularly limited, and a method of mixing and melting the blended raw material chips in the same extruder, a method of mixing after melting each in a separate extruder, and the like may be mentioned. The latter method is preferable from the viewpoint of control. Transesterification is also greatly affected by the type and amount of the polyester polymerization catalyst and its residual activity. Therefore, techniques such as selection of the catalyst, optimization of the amount, and addition of a catalyst activity inhibitor such as a phosphorus compound may be used in combination.

The polyester film of the present invention has a structure of at least two or more layers formed by laminating a polyester layer A and a polyester layer B. Such a film having a multilayer structure constitutes, for example, each layer. The polyester composition is separately melted and extruded, and after lamination and fusion before solidification, biaxial stretching, a method of heat setting, the polyester A layer and the B layer are separately melted, extruded and formed into a film,
It can be manufactured by a method of laminating and fusion-bonding them both in an unstretched state or after stretching. However, from the simplicity of the process, it is preferable to laminate-fusion before solidification using a multilayer die.

The ratio of the thickness of the polyester A layer to the thickness of the B layer R
(R = thickness of layer A / thickness of layer B) is preferably in the range of 0.5 to 5. Furthermore, the range of 1-4 is preferable. R is 0.
If it is less than 5, the deformation follow-up property is deteriorated during processing into a can. On the other hand, if R exceeds 5, the thickness of the B layer, which is the contact surface with the can forming jig, becomes too thin, so that sufficient hardness of the surface cannot be obtained, and adhesion to the jig tends to occur.

As a method for producing the film, polyesters (I) and (II) constituting the layer A and the layer B are blended in an appropriate ratio, respectively, and an extruder for forming the layer A and an extruder for forming the layer B are blended. More separately, at a temperature of 250-280 ° C, 3-15
The mixture is extruded by melt mixing for one minute, and is laminated and joined by a T die (referred to as a multilayer die) having a structure in which the respective layers are joined before being solidified and then extruded into a sheet shape, and the sheet is cooled to a room temperature or lower. The resulting unstretched film was then guided to a simultaneous biaxial stretching machine,
MD and TD (lateral direction) at a temperature of 150 ° C.
Biaxially stretched to a draw ratio of about 4 times,
Can be manufactured by performing a heat treatment at 80 to 220 ° C. for several seconds with a relaxation rate of several percent. Before leading to the simultaneous stretching machine, preliminary longitudinal stretching of about 1 to 1.2 times may be performed.

This film can also be produced by a successive stretching method. An outline of the method is as follows. The unstretched film is heated by roll heating, infrared rays or the like, and stretched in the machine direction to obtain a machined film. Stretching utilizes the difference in the peripheral speed of two or more rolls, and the glass transition point (T
g) 2.5 times or more in a temperature range of 40 ° C. higher than Tg,
It is preferred to be 3.6 times or less. The longitudinally stretched film is then successively subjected to transverse stretching, heat setting, and heat relaxation treatments sequentially to form a biaxially oriented film. The transverse stretching is started at a temperature 40 ° C. higher than the Tg to Tg of the polyester. The temperature is preferably a temperature (100 to 40) C lower than the melting point (Tm) of the polyester. The magnification of the transverse stretching is adjusted depending on the required physical properties of the final film, but is preferably at least 2.7 times, more preferably at least 3.0 times. Further, it is preferably at least 3.6 times. An extension of 2 to 20% may be applied in the film width direction at the time of the heat setting treatment subsequent to the stretching, but this stretching rate is preferably included in the total stretching ratio. After the heat setting, a process of continuously reducing the width of the film (called a relaxation process) is performed to adjust the heat shrinkage characteristics of the film, and then the film is cooled to Tg or less of the film to obtain a biaxially stretched film.

The heat treatment after stretching is a necessary step for imparting dimensional stability to the film. Examples of the method include a method of blowing hot air, a method of irradiating infrared rays, and a method of irradiating microwaves. A known method can be used. Among them, the method of blowing hot air is optimal because heating can be performed uniformly and accurately.

In order to improve the processability during film production and can production, it is desirable to add a small amount of an inorganic lubricant such as silica, alumina, kaolin or the like to form a film to impart slip properties to the film surface. Furthermore, in order to improve the appearance and printability of the film, for example, the film may contain a silicone compound or the like. In the case of a laminated film of the layer A and the layer B, it is preferable that the content of the inorganic lubricant in the layer A adhered to the final metal is equal to or less than that of the layer B. The content of the inorganic lubricant in each film is 0.001 to 0.5% by mass, preferably 0.1 to 0.3% by mass. Further, in combination with the function of the lubricant, titanium dioxide can be added to the A layer or the B layer up to about 20% for the purpose of hiding. In particular, in the simultaneous biaxial stretching, a stretched film can be obtained even if more than 40% of titanium dioxide is added.

The polyester film of the present invention comprises a steel plate,
It is heat-laminated on a metal plate such as aluminum, but the metal plate to be laminated is chemically treated such as chromic acid treatment, phosphoric acid treatment, electrolytic chromic acid treatment, chromate treatment, nickel, tin, zinc, aluminum, gunmetal, brass Alternatively, a steel plate subjected to other various plating treatments or the like can be used.

The film of the present invention may be provided with an adhesive layer by a co-extrusion method, a laminating process, or a coating process for the purpose of further improving the thermocompression bonding property with the metal plate and the subsequent adhesion. Adhesive layer is 1μ in dry film thickness
m or less is preferable. The adhesive layer is not particularly limited, but is preferably a thermosetting resin layer made of an epoxy resin, a polyurethane resin, a polyester resin, or various modified resins thereof. In addition, on the opposite side of the film to be thermocompression-bonded to the metal plate, one or two or more resins are used to improve the appearance and printability of the metal can body and to improve the heat resistance and retort resistance of the film. Layers can be provided. These layers can be provided by a coextrusion method, a lamination or a coating process.

As a method for laminating the film and the metal plate of the present invention, the metal plate is preheated to 160 to 250 ° C., and the film and the film are heated at 30 ° C.
Further, after being pressed and thermocompression-bonded by a roll whose temperature is controlled at a temperature lower by 50 ° C. or more, it is continuously manufactured by cooling to room temperature. Examples of the method of heating the metal plate include a heater roll heat transfer method, an induction heating method, a resistance heating method, and a hot air transfer method. preferable.
As a cooling method after lamination, a method of dipping in a coolant such as water or a method of contacting with a cooling roll can be used.

The metal plate obtained as described above may be subjected to a processing treatment as it is. However, after being heat-treated at a temperature higher by 10 to 30 ° C. than the melting point of the polyester, the metal plate is rapidly cooled to bring the present polyester film into an amorphous state. By doing so, higher workability can be imparted.

As the metal container, a metal container which has been processed to a form that can be used after being filled with food and drink, and a part thereof, for example, a can lid formed into a shape that can be wound and processed. Is also included. In particular, can body members of three-piece cans (3P cans) subjected to severe neck-in processing, and two-piece cans (2
When used as a can body member of (P can), excellent workability of the film of the present invention is exhibited. The metal container using the film of the present invention is excellent in retort resistance, flavor, and corrosion resistance, and thus, coffee, green tea, black tea, oolong tea,
It is suitable for filling contents such as various processed foods.

[0037]

Next, the present invention will be described specifically with reference to examples. The raw materials of the films and the methods for measuring the characteristic values in the examples and comparative examples are as follows.

(1) Raw material polyester (I) A-1: PBT subjected to solid-phase polymerization, IV 1.08 dl /
g, Tm 223 ° C, containing 40 ppm of Ti catalyst. A-2: PBT subjected to solid-state polymerization, IV 0.94 / g,
Tm 223 ° C, containing 100ppm of Ti catalyst. A-3: Sebacic acid (SEA) 5mo subjected to solid state polymerization
1% copolymerized PBT, IV 0.92 dl / g, Tm217
° C, containing 40 ppm of Ti catalyst. A-4: SEA 12 mol% copolymerized PBT, IV 0.9
5 dl / g, Tm 204 ° C., not subjected to solid state polymerization,
Contains 40ppm of Ti catalyst.

Polyester (II) B-1: PET subjected to solid-state polymerization, IV 0.75 dl /
g, Tm 255 ° C., containing 40 ppm of Ge catalyst. B-2: PET subjected to solid-state polymerization, IV 0.64 dl /
g, Tm 255 ° C, 100 ppm Sb catalyst. B-3: Isophthalic acid (IPA) 5 mol% copolymerized PE
T, IV 0.81 dl / g, Tm 243 ° C, not subjected to solid-state polymerization, containing 100 ppm of Sb catalyst. B-4: IPA 12 mol% copolymerized PET, IV 0.6
5 dl / g, Tm 226 ° C., not subjected to solid state polymerization,
Contains 100 ppm of Sb catalyst.

(2) Measurement method Intrinsic viscosity (IV) Using an equal mass mixed solvent of phenol / tetrachloroethane,
It was determined from the solution viscosity measured at a temperature of 20 ° C. and a concentration of 0.5 g / dl.

B. Transesterification index (Ex) 13C NM by GEMINI2000 / 300 nuclear magnetic resonance apparatus (magnetic field strength: 7.05T) manufactured by Varian.
R was measured. The measurement sample is a film 60-1
A solution obtained by dissolving 00 mg in 0.7 ml of CF ₃ COOD solvent was used, and the index was determined from the integrated value of the peak (FIG. 2) caused by transesterification according to the following equation. Ex = (Sab + Sba) / (Saa + Sbb + Sab)
+ Sba) × 100 (%)

C. Melting point (Tm) Using Perkin Elmer DSC at 20 ° C. /
The melting point at the time of heating was measured in minutes. As a measurement sample of the film, a stretched film was melted and then rapidly cooled at a rate of 100 ° C./min or more to be in an amorphous state.

D. Heat laminating property A sample film and a tin-free steel plate having a thickness of 0.21 mm are superposed and supplied between a metal roll heated to 200 ° C. and a silicon rubber roll, and the speed is 20 m.
/ Min, with a linear pressure of 4.9 × 10 ⁴ N / m.
After sec, it was immersed in ice water and cooled to obtain a laminated metal plate. From the obtained laminate, a strip-shaped test piece having a width of 18 mm (ends were not laminated, and the laminated portion was secured to the MD by 8 cm or more) was placed on the TD for 11 hours.
Cut out pieces. Next, JI was applied to the film surface of this test piece.
Attach the adhesive tape specified in SZ-1522,
A 180 degree peel test was performed at a speed of 10 mm / min with an autograph manufactured by Shimadzu Corporation, and the peel strength was measured to evaluate the adhesiveness according to the following criteria. ◎: The peel strength of 10 or more test pieces was 2.9N or more, or the film was broken at 2.9N or more. ：: The peel strength of 5 to 9 test pieces was 2.9N or more, or the film was broken at 2.9N or more. Δ: 7 or more test pieces having a peel strength of less than 2.9 N. For a film having a heat lamination property of △, the film was heat-laminated again in order to determine the optimum heat lamination temperature of the film, and was subjected to the subsequent tests.

E. Formability The state of the laminated metal plate obtained in D above when the two-piece can of 500 ml was subjected to deep drawing with the film side as the inner surface of the can body was observed. The evaluation was XX for peeling, rupture or whitening that was visually observed, but was not visually observed, but X where corrosion of the metal was observed by immersion in an aqueous copper sulfate solution,腐 食 indicates that no corrosion was observed. Films evaluated as “×” and “XX” in terms of moldability were poor in taste retention and fragrance retention. Therefore, the evaluation was not carried out and the film was judged to be unacceptable.

F. Retort resistance The laminated metal plate obtained in the above D was treated at 125 ° C. for 30 minutes.
The state of the film after the min retort treatment was observed. In the evaluation, x was given when clear whitening or white spots were observed, Δ was given when whitening was observed to the extent that it was not obvious but was visually discernible, and ○ was given when no change was observed visually.

G. Impact resistance Ten pieces of the laminated metal plate obtained in D above were
After retort treatment at 25 ° C for 30 minutes, and (b) 1
After retort treatment at 25 ° C for 30 minutes, storage in a 50 ° C atmosphere for one month,
50 kg weight (the tip is a spherical surface with a diameter of 1/2 inch)
The state of the film when dropped on a film surface from a height of cm was observed, and the impact resistance was evaluated according to the following criteria. X: Peeling or breakage was visually observed even with one sheet. Δ: Not visually observed, three or more of which were immersed in an aqueous solution of copper sulfate and metal corrosion was observed. ：: Two or less sheets which were not visually observed and were corroded by immersion in an aqueous solution of copper sulfate. ◎: Not observed visually, even when immersed in an aqueous solution of copper sulfate
No corrosion was observed on all the sheets.

H. 500 g of distilled water was filled using the 2P 500 ml can body obtained in E above, and a commercially available 202-diameter aluminum EO lid was tightly sealed and sealed, and subjected to a retort treatment at 125 ° C. for 30 minutes. Was. Next, after sufficiently cooling to room temperature, the contents were tasted by 50 panelists to determine whether the smell, taste, etc. were different from distilled water, and the results were preserved according to the following criteria. It was used as an index of scent retention. ：: Less than 5 people sensed the difference between the two. Δ: The number of persons who sense the difference between the two is 5 or more and less than 10. ×: 10 or more people sensed the difference between the two.

Examples 1 to 12 and Comparative Examples 1 to 13 Layer A and layer B were prepared from polyester (I) and polyester (II) having the composition shown in Table 1 by adding silica having an average particle size of 1.1 μm. And melt blended and extruded using two independent extruders. The respective melts were merged and laminated in layers before reaching the outlet of the T-die.
It was extruded from the die outlet and quenched and solidified to obtain an unstretched film. Next, the end of the unstretched film was gripped by a clip of a tenter-type simultaneous biaxial stretching machine, and after traveling in a preheating zone at 60 ° C, the MD was 3.0 times at 80 ° C and 3.3 at TD. It was simultaneously biaxially stretched by a factor of two. After that, the relaxation rate of TD was 5
%, And after a heat treatment at a temperature of 150 ° C. for 4 seconds,
After cooling to room temperature, the film was rolled up to obtain a biaxially stretched film having a thickness of 25 μm. From the obtained film, a laminated metal plate was obtained by the method described in D and evaluated at the same time. Furthermore, the moldability of the film of the laminated metal plate obtained in D was evaluated by the method described in E. Further, the retort resistance, impact resistance, and flavor and fragrance retention of the laminated metal plate were evaluated by the methods shown in F, G, and H, respectively. Table 2 shows various physical properties of the film obtained in the above test and each evaluation result. In order to measure the independent basic physical properties of each layer of the film, a raw material having the same polymer composition was extruded into each extruder under the same extrusion conditions so as to have the same residence time, and an unstretched film was obtained. The transesterification index and the melting point were measured by the methods shown in FIGS.

Examples 13 to 17 and Comparative Examples 14 to 1
9 An unstretched film shown in Table 1 was obtained in the same manner as in Example 1.
This unstretched film is guided to a roll-type vertical (MD) stretching machine, and is preheated from 45 ° C. to a final 55 ° C.
The film was stretched longitudinally 2.8 times at ℃. After cooling to room temperature, the film was continuously guided to a tenter-type transverse stretching machine, preheated at 75 ° C. while holding both ends of the film with clips, and stretched 3.6 times while raising the temperature from 80 ° C. to 90 ° C. for a while. . Then 150 ° C
For 4 seconds, followed by a 4% relaxation treatment, followed by cooling and winding to obtain a sequentially biaxially stretched film having a thickness of 25 μm. From the obtained film, a laminated metal plate was obtained in the same manner as in Example 1, and was similarly evaluated. Table 3 shows the films and their evaluation results.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

The films obtained in Examples 1 to 17 were excellent in heat laminating properties, moldability, impact resistance, retort resistance, and flavor and fragrance retention, but were obtained in Comparative Examples 1 to 17. A film satisfying all the above-mentioned properties was not obtained.

[0054]

According to the present invention, it has excellent heat lamination properties and moldability, especially high-order workability such as drawing and ironing, and also has excellent impact resistance and retort resistance after molding. Suitable for coating metal cans, it is possible to provide a polyester film for metal plate lamination

[Brief description of the drawings]

FIG. 1 is an NMR chart of a film of the present invention.

FIG. 2 is an NMR chart in which peaks (Sab, Sba, Saa, Sbb) caused by transesterification in FIG. 1 are enlarged.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Inui 31-3 Uji Hinojiri, Uji City, Kyoto Prefecture Unitika Co., Ltd. Uji Plastic Factory F-term (reference) 3E086 BA04 BA13 BA15 BB15 BB41 CA01 CA11 4F100 AB01C AK41A AK41B AK42A AL05A BA02 BA03 BA07 BA10A BA10B BA10C BA16 CB00 DA01 GB16 JA04A JA04B JA20A JA20B JJ03 JL01 YY00A YY00B 4J002 CF06X CF07W GG00

Claims (4)

[Claims] 1. A laminated film comprising at least two layers formed by laminating a polyester A layer and a polyester B layer, wherein the polyester A layer is composed of polybutylene terephthalate or a polyester (I) 90 to 45 mainly comprising the same. % By weight, and 10 to 55% by weight of polyethylene terephthalate or a polyester (II) mainly containing the same,
The transesterification index of the polyesters (I) and (II) in the layer is 1 to 10%, and the polyester B layer is the polyester (I) 25 to 55
% Of polyester (II) and 75 to 45% by weight of polyester (II), wherein polyester (I) and polyester (II) in layer B
Has a transesterification index of 7% or less, and each of the polyester A layer and the polyester layer B is 200 to 223.
A film for laminating a metal plate, wherein the film has a melting point of the polyester (I) at ℃ and the melting point of the polyester (II) at 230 to 256 ° C. 2. The thickness ratio R of A layer and B layer (R = A layer thickness /
The film for laminating a metal plate according to claim 1, wherein the thickness (B layer thickness) is 0.5 to 5. 3. A film-laminated metal plate obtained by laminating the layer A of the film for metal plate lamination according to claim 1 directly or via an adhesive. 4. A metal container formed using the film-laminated metal plate according to claim 3.