JP2002212315A - Polyester film for metal plate laminate, metal plate and metal container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film excellent in applicability to heat lamination on a metal plate, can formability, especially high-order processability to such as drawing forming or strip-off forming, shock resistance and holdability for the flavor and taste of content, and suitable for producing a film-laminated metal can. SOLUTION: The film comprises a polyester (I) of polybutylene terephthalate or mainly composed of it, and a polyester (II) of polyethylene terephthalate or composed mainly of it. The content of the polyester (I) is 80-40 mass% and that of the polyester (II) is 20-60 mass%. The film has the melting point of the polyester (I) in the range of 200-223 deg.C, and the melting point of the polyester (II) in the range of 230-256 deg.C. The intrinsic viscosity of the whole film is >=0.75.

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 mass 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 mass at a temperature of from 245 ° C 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. (C) Japanese Patent Application Laid-Open
No. 316,775 discloses a copolymer polyester 99-
A film comprising 60% by mass and 1 to 40% by mass of a polyester mainly composed of butylene terephthalate having a melting point of 180 to 223 ° C and having an intrinsic viscosity of 0.68 or more and less than 0.75 is disclosed. Also, (d) Tokuhei 7-84
No. 532 discloses a polyester film having an intrinsic viscosity of 0.75 or more. Furthermore, (e) JP-A-11-279294 discloses a polyester film in which ethylene terephthalate units are at least 90 mol% and the reduced viscosity is 0.8 to 1.1 dl / g.

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 intrinsic viscosity is 0.68 or more,
Less than 0.75, which is at a low level, and lacked the ability to follow deformation for more severe drawing and ironing,
The resin component is substantially 40% by mass or less as a PBT component, the crystallization characteristics of the film are insufficient, and the film is not necessarily sufficient in terms of resistance to retort treatment, stability in long-term storage after treatment, and shock absorption resistance. It wasn't.

In (d), it is proposed to use a polyester film having an intrinsic viscosity of 0.75 or more, which is effective in retort resistance, impact resistance, and prevention of deterioration of the taste of the contents. Specifically, as a polymer, PE
There has been proposed a homogeneous polymer which is a copolymer containing T, polyethylene naphthalate and polycyclohexane dimethylene terephthalate as main components. However, in addition to the heat laminating properties, demands for recent high performance that requires contradictory properties such as stricter high deformation deformation followability, adhesion to processing jigs, and long-term storage stability after retort processing are required. As a film for cans, it is difficult to satisfy all the characteristics with a uniform polymer system having such a single composition.

In (e), the ethylene terephthalate unit is at least 90 mol% and the reduced viscosity is 0.8%.
１．１1.1 dl / g, which proposes a polyester film that can withstand drawing and ironing and is not easily whitened even in boiling water. The polyester film is resistant to boiling water by containing at least 90 mol% of ethylene terephthalate units having high heat resistance and high hot water resistance, and has an adhesion to metal of at least 3 mol and less than 10 mol. This is addressed by the introduction of a copolymer component. Therefore, this polymer is in the technical category of a homogeneous polymer, and has a limitation similarly to (e), and can sufficiently respond to recent demands for high-speed and high-deformability followability. It is not. In other words, when emphasis is placed on deformation followability, the concentration of the copolymer component in the polyester must be increased, and the adhesion to the jig during can processing increases, impeding productivity and preventing retort resistance as a can. In addition, long-term storage stability had to be inhibited.

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 comprising 5% by mass and 10 to 55% by mass of PET or a 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 increasing the speed of cans, increasing the capacity of cans, and reducing the thickness of cans, and the ratio of metal deformation during drawing and ironing has been increasing further. 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. further,
As cans are expanded to be used for cooling soft drinks, the impact resistance of the laminate film when the can falls or an external impact is applied during the processing and distribution stage is strongly demanded. ing. Further, since the storage period of the cans is long, the long-term stability when the storage can be cooled for a long time or heated and stored in the winter is also an important property. As the range of use of film-laminated cans has increased as described above, the required performance of films and cans formed by laminating the films is becoming increasingly sophisticated.
Development and improvement of suitable films are urgently required.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent heat lamination properties with a metal plate, excellent moldability of cans, especially high-order workability such as drawing and ironing, excellent impact resistance, and the like. Polyester film for metal lamination suitable for film-laminated metal cans with excellent content and flavor retention of the contents,
It is to provide a laminated metal plate and a metal container using the same.

[0014]

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 the crystallinity differs.
A polyester film having a specific blending ratio of at least two types of polyesters including at least two types of polyesters, that is, a polyester (I) mainly composed of PBT and a polyester (II) mainly composed of PET, is used. By selecting the intrinsic viscosity (IV) as an index, a metal having excellent heat lamination properties with metals, moldability of cans, particularly excellent in draw molding and ironing, and also excellent in impact resistance and flavor retention The present inventors have found that cans can be manufactured and provided, and arrived at the present invention.

That is, the gist of the present invention is as follows. A film comprising polybutylene terephthalate or a polyester (I) mainly comprising the same and polyethylene terephthalate or a polyester (II) mainly comprising the same, wherein the content of the polyester (I) is 8
0 to 40% by mass, the content of polyester (II) is 20 to
60% by mass, the film has a melting point of the polyester (I) at 200 to 223 ° C, a melting point of the polyester (II) at 230 to 256 ° C, and the intrinsic viscosity of the whole film is 0.75 or more. Characteristic film for metal plate lamination.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the PBT-based polyester (I) is PBT or a copolymer of other components with PBT. In a film blended with the polyester (II), the melting point of the polyester (I) is 200 ° C.
As described above, the melting point of PBT needs to be 223 ° C. or lower, and 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 decreases.
When using the copolymerized PBT, the copolymerization ratio may be selected by selecting the copolymerization ratio and the structure of the component to be copolymerized so that the melting point is within the above range.
80 mol% or more of 1,4-butanediol is preferable,
Particularly, 90 mol% or more is preferable. 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. The melting point of (II) needs to be in the range of 230 to 256 ° C, and preferably in the range of 236 to 256 ° C. More preferably, it is in the range of 246 to 256 ° C. When the melting point is lower than 230 ° C., the crystallinity decreases,
Whitening or white spots occur after the retort treatment, or the impact resistance after the retort treatment decreases. 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 that can be copolymerized with PET is not particularly limited, and examples thereof include the same compounds as polyester (I).

The intrinsic viscosity of the whole film of the present invention is 0.1.
It needs to be 75 or more. 0.75 intrinsic viscosity
If it is less than 1, the practical performance of the film is insufficient, and the film breaks particularly at the time of high-order processing of the can, and the productivity is extremely deteriorated. In particular, the capacity of the can increases, and as a result, the degree of deformation of the film increases during the process of drawing and ironing from a laminated metal plate to the can, so that it can not follow it, causing voids and cracks in the film layer And, even if a slight impact from the outside promotes peeling of the film layer and growth of cracks, when used on the inner surface of the can,
As a result of direct contact between the contents and the metal of the can, the flavor and aroma may be reduced or a problem may occur in flavor. In addition, on the outer surface of the can, the printed appearance is deteriorated in the portion where the film is whitened by the void. Further, there is a fear that a problem that the can is corroded during long-term storage due to voids and cracks may occur.

On the other hand, the limiting viscosity of the raw material polyester used for producing the polyester film of the present invention is preferably 0.70 or more for polyester (I).
Furthermore, 0.75 to 1.6 is preferable. Polyester (I
In I), it is preferably 0.60 or more, more preferably 0.65 to
1.0 is preferred. The intrinsic viscosity after melt-mixing the polyester (I) and the polyester (II) is 0.75 to
A range of 1.2 is preferred. When the intrinsic viscosity exceeds the above range, the load applied to the resin melt extruder in the film production process increases, and the production speed has to be sacrificed, or the melt residence time of the resin in the extruder increases. Too much reaction between the polyester resins leads to deterioration of the film properties, resulting in deterioration of 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 the 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 film are represented by (I) / (II) =
A range of 80 to 40/20 to 60 (% by mass) is required, but more preferably (I) / (II) = 70 to 55/3.
It is in the range of 0 to 45 (% by mass).

When the polyester (I) in the film is 8
If it exceeds 0% by mass, the polyester (I) having high crystallinity
Is remarkably exhibited, the moldability of the film-laminated metal plate is reduced, and the impact resistance is also deteriorated. When the amount of the polyester (I) is less than 40% by mass, the crystallization rate decreases, and the physical properties after the retort treatment decrease. In particular, when the content of the polyester (I) is in the range of 70 to 55% by mass,
It has good followability of forming process when performing high-order drawing and ironing of a laminated metal plate at high speed, and there is no whitening phenomenon due to generation of voids due to excessive deformation of the film, no generation of micro cracks, and It has excellent adhesiveness and balances the impact resistance of the resulting can and the physical properties after retort treatment. As a result, when it is used on the inner surface of a can, it has good corrosion resistance, and is excellent in the protection of the contents, the flavor and fragrance retention, and the flavor retention. In addition, when used on the outer surface of a can, a product with high commercial value can be obtained, for example, no rust is generated and the glossiness of a printed pattern is good.

The concentration of terminal carboxyl groups of the film of the present invention is preferably 30 equivalents / ton or less. If the terminal carboxyl group concentration is higher than this, the adhesion of the film surface to the metal jig increases, the squeezing of the can, the sliding in the ironing process becomes worse, and as the production speed of the can increases, This will reduce productivity. Although the reason is unknown, if the terminal carboxyl group concentration is high, the surface hardness of the film decreases, the film is easily scratched during can processing, the film layer is easily scraped, and the surface gloss of the metal can is reduced. Otherwise, the metal surface is exposed, and the corrosion resistance is reduced, the taste of food is affected, and the flavor and aroma retention are reduced. In addition, the carboxyl group promotes the generation of a low molecular compound in the film, which migrates into the food, resulting in a decrease in the flavor and aroma.

As a method for controlling the terminal carboxyl group concentration, a prepolymer obtained by melt polymerization is heated to a temperature not lower than its glass transition temperature and not higher than its melting point, and is subjected to solid-phase polymerization under an inert gas flow or under vacuum. Or the method of adding a so-called terminal blocking agent that reacts with a carboxyl terminal group, a method of lowering the melting temperature of the polymer as much as possible, or a method of reducing the water content of the polymer as much as possible. Although it can be realized by combining them, it is sufficient that the technology can substantially reduce the terminal carboxyl group concentration regardless of the method.

In the film of the present invention, the transesterification index of the polyester (I) and the polyester (II) (the measuring method is described in Examples) is preferably 1 to 10%, more preferably 2 to 7%. When the transesterification rate increases and the randomization of the components of the polyesters (I) and (II) progresses, especially when it exceeds 10%, the melting point of the film decreases, and the heat resistance decreases. In addition, the crystallization speed accompanying the stretching during the molding process is significantly increased, and the moldability is reduced.
On the other hand, when the content is 1% or less, the polyethylene terephthalate component retains its properties, and the PBT having high crystallinity is present therein, so that the film is poor in following deformation and the formability of the metal plate is reduced. . When this transesterification index is within the preferred range, the metal plate does not stick to the processing jig during forming into a can, friction is reduced, and the uniformity of the obtained can surface is increased.

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.

As a method for producing the film of the present invention, polyester (I) and (II) are blended in an appropriate ratio,
After melt-mixing at a temperature of 250 to 280 ° C. for 3 to 15 minutes from an extruder, the mixture is extruded into a sheet through a T die. The sheet is closely contacted on a cooling drum whose temperature has been adjusted to room temperature or lower and cooled. The obtained unstretched film is then guided to a simultaneous biaxial stretching machine, and MD and TD are heated at a temperature of 50 to 150 ° C.
The film is biaxially stretched (transverse direction) so as to have a draw ratio of about 2 to 4 times, and the relaxation rate of TD is set to several percent, and
It can be manufactured by performing a heat treatment at 20 ° C. for several seconds. 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 2.7 times or more, preferably 3.0 times or more, and more preferably 3.6 times or more.
It is better to make it twice or more. 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. The content of such an inorganic lubricant in the film is 0.001 to 0.5% by mass, preferably 0.1 to 0.3% by mass. Also, in combination with the function of the lubricant, titanium dioxide can be added 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 coextrusion 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 of 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, it 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 that 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 up. 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.

[0039]

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 1.40 dl /
g, Tm 223 ° C, 40 ppm Ti catalyst, COOH
Group 5 equivalents / ton. A-2: PBT subjected to solid-phase polymerization, IV 1.22 dl /
g, Tm 223 ° C, 40 ppm Ti catalyst, COOH
Group 7 equivalents / ton. A-3: PBT subjected to solid-state polymerization, IV 1.08 dl /
g, Tm 223 ° C, 40 ppm Ti catalyst, COOH
Group 7 equivalents / ton. A-4: PBT subjected to solid-state polymerization, IV 0.94 / g,
Tm: 223 ° C., 100 ppm of Ti catalyst, 12 equivalents / ton of COOH groups. A-5: PBT without solid phase polymerization, IV 0.90
dl / g, Tm223 ° C, TI catalyst 40ppm, C
OOH group 35 equivalents / ton. A-6: PBT subjected to solid-state polymerization, IV 0.80 dl /
g, Tm 223 ° C., 40 ppm Ti catalyst, COOH
Base 15 equivalents / ton. A-7: PBT not subjected to solid phase polymerization, IV 0.65
dl / g, Tm 223 ° C., containing 100 ppm of Ti catalyst,
COOH group 50 equivalents / ton. A-8: 5 mol of sebacic acid (SEA) subjected to solid state polymerization
1% copolymerized PBT, IV 0.92 dl / g, Tm217
° C, 40 ppm of Ti catalyst, 18 equivalents of COOH group /
T. A-9: SEA 12 mol% copolymerized PBT, IV 0.9
5 dl / g, Tm 204 ° C., not subjected to solid state polymerization,
Contains 30 ppm of Ti catalyst, 30 equivalents / ton of COOH group.

Polyester (II) B-1: PET subjected to solid layer polymerization, IV 0.90 dl /
g, Tm 255 ° C., containing 40 ppm of Ge catalyst, COOH
Base 10 equivalents / ton. B-2: PET subjected to solid-state polymerization, IV 0.75 dl /
g, Tm 255 ° C., containing 40 ppm of Ge catalyst, COOH
Base 15 equivalents / ton. B-3: PET subjected to solid-state polymerization, IV 0.64 dl /
g, Tm 255 ° C., 100 ppm Sb catalyst, COO
H group 20 equivalents / ton. B-4: PET without solid phase polymerization, IV 0.62
dl / g, Tm 255 ° C, 100 ppm of Sb catalyst,
COOH group 50 equivalents / ton. B-5: 5 mol% copolymerized PE of isophthalic acid (IPA)
T, IV 0.81 dl / g, Tm 243 ° C., not subjected to solid-state polymerization, 100 ppm of Sb catalyst, 18 equivalents / ton of COOH group. B-6: 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 and 50 equivalents / ton of COOH group.

(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. With respect to the film having a thermal lamination property of Δ, the film was subjected to thermal lamination again in order to find the optimum thermal lamination temperature of the film, and was subjected to the subsequent tests.

E. Formability Using the film side of the laminated metal plate obtained in D above as the inner surface of the can body, drawing and ironing was performed, and 2 equivalent to 500 ml.
A piece can was molded. The obtained can was filled with a 1% by mass saline solution, and a current value was measured when a voltage of 6 V was applied using the can body as an anode to evaluate the degree of defects in the polyester film. The more current flows, the more defects there are, and the can quality is preferably 1 mA or less. Those having a current value of 5 mA or more were evaluated as x.

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 6 and Comparative Examples 1 to 10 Polyester (I) and polyester (II) having the composition shown in Table 1 were added and contained silica having an average particle size of 1.1 μm. It was melt-mixed, extruded from the T-die outlet, and quenched and solidified to obtain an unstretched film. Next, the end of the unstretched film was gripped by clips of a tenter-type simultaneous biaxial stretching machine, and after traveling through a preheating zone of 60 ° C.
Simultaneous biaxial stretching was performed at 0 ° C. by 3.0 times in MD and 3.3 times in TD. Thereafter, the relaxation rate of TD was set to 5%, and the temperature was set to 150 ° C.
, And then cooled to room temperature and taken 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.

Examples 7 to 9 and Comparative Examples 11 to 13 Unstretched films shown in Table 1 were 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 2 shows the films and their evaluation results.

[0052]

[Table 1]

[0053]

[Table 2]

The films obtained in Examples 1 to 9 were excellent in heat laminating properties, moldability, impact resistance, retort resistance, and flavor and fragrance retention, but were obtained in Comparative Examples 1 to 13. A film satisfying all the above-mentioned properties was not obtained.

[0055]

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. A polyester film for metal plate lamination suitable for coating a metal can can be provided.

[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.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Inugi 31-3 Uji Hinojiri, Uji City, Kyoto Pref. AA46 AA84 AA88 AF53 AF58 AH05 BA01 BB06 BB08 BC01 4F100 AA20 AB01A AB03 AK42B AL05B BA02 BA07 CB00G DA01 DA20 DE01 EH17 EJ19 EJ38 EJ42 GB16 JA04B JA06B JB02 JK10 JL01 JL02 JL002 YG00B

Claims (5)

[Claims] 1. Polybutylene terephthalate or a polyester (I) mainly comprising the same, and polyethylene terephthalate or a polyester (II) mainly comprising the same
Wherein the polyester (I) content is 80 to 40% by mass, the polyester (II) content is 20 to 60% by mass, and the film is 200 to 223%.
A film for laminating a metal plate, wherein the film has a melting point of the polyester (I) at 230C and the melting point of the polyester (II) at 230 to 256C, and the intrinsic viscosity of the whole film is 0.75 or more. 2. Polyester (I) and polyester (I)
2. The film for laminating a metal plate according to claim 1, wherein the transesterification index of I) is 1 to 10%. 3. The film for laminating a metal plate according to claim 1, wherein the terminal carboxyl group has an amount of 30 equivalents / ton or less. 4. A film-laminated metal plate obtained by directly laminating the film for laminating a metal plate according to any one of claims 1 to 3 or via an adhesive. 5. A metal container formed by using the film-laminated metal plate according to claim 4.