JPH09277476A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good drawing processability as a main melting temperature in the temperature increase of each polyester layer and a crystallization temperature specified value in high speed cooling and temperature reincrease by a method in which a polyester layer of a polyester composition in which a specified quantity of an average particle size lubricant is incorporated into a specified polyester is laminated and formed. SOLUTION: A laminated polyester film is made by a method in which on one side of a polyester layer A of a polyester composition in which 0.01-1wt.% of a lubricant of 0.01-2.5μm average particle size is incorporated into polyester which mainly contains an aromatic dicarboxylic acid component and a diol component is laminated a polyester layer B of a polyester composition in which 0.05-1wt.% of a lubricant of 0.01-1.0μm average particle size is incorporated into polyester chiefly containing an aromatic dicarboxylic acid component and a diol components. In the polyester layers A, B, the main melting temperatures in temperature increase are made 180-240 deg.C and 210-260 deg.C, the crystallization temperatures in high speed cooling and temperature reincrease are made 100-160 deg.C and 140-190 deg.C, and the average diameter of spherulites generated in the layer A is made not greater than 5μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester laminated film, and more particularly, it has excellent formability when used for coating the outer surface of a deep-drawn metal can, and is printed on the outer coated surface of the metal can. The present invention relates to a polyester laminated film used for the outer surface coating of a deep-drawn metal can, in which the metal surface can be seen through, and when the metal can is subjected to retort sterilization, no white spots appear on the outer coating.

[0002]

2. Description of the Related Art Metal cans are generally coated 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 using 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.

As the thermoplastic resin film for coating the metal can, a polyester film, particularly a polyethylene terephthalate film, has attracted attention because of its balanced characteristics, and the following proposals have been made.
That is,

(A) 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 (JP-A-56).
-10451 and JP-A-1-192546).

(B) An amorphous or extremely low crystalline aromatic polyester film is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 192545/1989).
JP-A-2-57339).

(C) A biaxially oriented polyethylene terephthalate film which is heat-set in a low orientation is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 64-22530).

(D) A copolyester film having a specific plane orientation coefficient, heat shrinkage ratio, and density is laminated on a metal plate and used as a can-making material (Japanese Patent Publication No. 3-87629).
Issue).

(E) A copolyester film containing a white pigment having a specific particle size and number of particles is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 5-17094).
No. 2).

However, according to the investigations of the present inventors, when such a conventional polyester film is used as a film for coating the outer surface of a deep-drawn metal can, sufficient characteristics cannot be obtained, and there are the following problems. It became clear.

Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance, but the moldability is insufficient, and the film is whitened (generation of microcracks) and ruptured in the can manufacturing process accompanied by large deformation. Occurs.

As for (B), since it is an amorphous or extremely low crystalline aromatic polyester film, the moldability is good, but after printing, post-treatment such as retort sterilization after can-making, and further. It tends to become brittle after long-term storage,
There is a risk that the film will be transformed into a film that is easily broken by the impact from the outside of the can.

Regarding (C), although it is intended to exert its effect in the intermediate region between the above (A) and (B), it has not yet reached the low orientation applicable to can making, and Since the isotropy of the film surface is not guaranteed, when omnidirectional deformation such as can manufacturing (deep drawing) is performed, the moldability may be insufficient in a specific direction of the film.

As for (D), the moldability and heat resistance are good, but the retort sterilization treatment (usually 12) after can making.
During steam treatment at 0 to 130 ° C.), water droplets adhere to the bottom of the can, and white spots due to crystallization occur on the outer surface of the water droplet adhered portion and its surroundings, which impairs the appearance of the product.

With regard to (E), the molding processability and heat resistance are good, and since it has a white hiding property, there is no problem of whitening spots during retort sterilization treatment, but there is no printing of the outer surface coating. It is impossible to see through the metal background, and the outer surface coating intended by the present invention cannot be obtained.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the prior art and to provide a metal can with excellent forming workability in the deep drawing can processing after it is bonded to a metal plate. Polyester used for the outer surface coating of deep-drawn metal cans, where the metal surface can be seen through the non-printed outer surface coating and there is no white spots on the outer surface coating when the metal can is retort sterilized. It is to provide a laminated film.

[0016]

The object of the present invention is, according to the present invention, to provide a polyester (A) containing an aromatic dicarboxylic acid component and a diol component as main components and having an average particle size of 0.01 to
On one surface of the polyester layer (A) composed of the polyester composition (A) containing 0.01 to 1% by weight of a lubricant of 2.5 μm, the polyester (B) containing an aromatic dicarboxylic acid component and a diol component as main components The average particle size is 0.01 to 1.
A polyester laminated film in which a polyester layer (B) made of a polyester composition (B) in which 0.05 μm to 1% by weight of a lubricant is blended is laminated, and the polyester layer (A) has a main melting temperature at the time of heating. Of 180 to 240 ° C., the crystallization temperature at the time of re-heating after quenching is 100 to 160 ° C., and the average diameter of spherical crystals generated by the crystallization is 5 μm or less, and the polyester layer (B) is heated at the time of heating. Has a main melting temperature of 210 to 260 ° C and a crystallization temperature of 14 at the time of rapid reheating.
Achieved with a polyester laminated film that is 0-190 ° C. Hereinafter, the present invention will be described in detail.

[Polyester (A)] In the present invention, the polyester (A) forming the polyester layer (A) is
It is a linear polyester mainly composed of an aromatic dicarboxylic acid component and a diol component.

Examples of the aromatic dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, which may be used alone or in combination of two or more kinds. May be Of these, terephthalic acid and isophthalic acid are particularly preferable as the aromatic dicarboxylic acid component.

As the dicarboxylic acid copolymerization component other than the aromatic dicarboxylic acid component, for example, aliphatic dicarboxylic acid such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid; alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid. Etc. can be mentioned.

As the diol component, HO-(CH
₂ ) n-OH (where n is an integer of 2 to 10) fatty acid diol (eg, ethylenetiglycol, 1,4-butanediol, hexanediol, etc.); HO-CH ₂ C
(R) ₂ —CH ₂ —OH (where R is an alkyl group having 1 to 4 carbon atoms) branched glycol (for example, neopentyl glycol or the like); diethylene glycol (DEG);
Examples include triethylene glycol (TEG); alicyclic diols (eg, cyclohexanedimethanol, etc.); and polyoxyalkylene glycols (eg, polyethylene glycol, polypropylene glycol, etc.), and particularly ethylene glycol, 1,4- Butanediol is preferred. These may be used alone or in combination of two or more.

As the polyester (A), for example, polyethylene terephthalate copolymerized with isophthalic acid, polyethylene terephthalate copolymerized with an aliphatic dicarboxylic acid such as isophthalic acid and adipic acid, 1,4-
Examples thereof include copolymerized polyethylene terephthalate such as polyethylene terephthalate copolymerized with butanediol, isophthalic acid and polyethylene terephthalate copolymerized with 1,4-butanediol. Further, for example, this copolymerized polyethylene terephthalate may be polybutylene terephthalate or a copolymer thereof. The polyester obtained by melt-mixing a polymer can be mentioned.

Among the above polyesters (A), a modified polyester obtained by melt-mixing polybutylene terephthalate or a copolymer thereof with copolymerized polyethylene terephthalate has a main melting temperature of 180 to 240 ° C. and a crystallization temperature of A polyester layer (A) having a temperature of 100 to 160 ° C. and an average diameter of spherical crystals generated by the crystallization of 5 μm or less is easily obtained, which is preferable.

Among these modified polyesters,
Copolymerized polyethylene terephthalate having a main melting temperature of 210 to 245 ° C. and a glass transition temperature (secondary transition temperature) of 60 ° C. or more (hereinafter abbreviated as “polyester (I)”) 1.
Polybutylene terephthalate and // 00 parts by weight
Alternatively, it is preferable to use a modified polyester obtained by melt mixing 1 to 65 parts by weight of a copolymer thereof (hereinafter abbreviated as “polyester (II)”).

When the content of the polyester (II) is less than 1 part by weight, when the polyester laminated film is used for coating the outer surface of a metal can, the film may be easily broken by impact, and the polyester (II) is If it exceeds 65 parts by weight, the heat resistance of the film may be lowered and the impact resistance may be insufficient.

Although the ratio of the above-mentioned polyester (I) copolymerization component depends on the components used, the main melting temperature is 210 to 245 ° C., particularly 215 to 240 ° C., and the glass transition temperature is 60 as a result. A ratio of at least 0 ° C, especially at least 65 ° C is preferable. When the main melting temperature of polyester (I) is less than 210 ° C., the heat resistance of the polyester laminated film may be poor, and the outer surface coated film of the metal can may not be able to withstand heating during printing. On the other hand, if the main melting temperature of the polyester (I) exceeds 240 ° C., the crystallization rate of the polymer may be too fast and the processability of the polyester laminated film may be impaired. When the glass transition temperature is lower than 60 ° C, it may be difficult to set the crystallization peak temperature of the polyester layer (A) within the range of the present invention. As the polyester (I), polyethylene terephthalate obtained by copolymerizing an isophthalic acid component is particularly preferable because a polyester having a high glass transition temperature can be obtained.

On the other hand, the polyester (II) is preferably a polybutylene terephthalate homopolymer or a copolymerized polybutylene terephthalate having a main melting temperature of 180 to 223 ° C. The copolymerization component of the copolymerization polybutylene terephthalate may be a dicarboxylic acid component or a diol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid and sebacic acid, and ethylene glycol as the glycol component. And aliphatic diols such as hexanediol; and alicyclic diols such as cyclohexanedimethanol. These may be used alone or in combination of two or more.

The proportion of the copolymerization component of the copolymerized polybutylene terephthalate depends on the components used, but as a result, the main melting temperature of the polyester (II) is in the range of 180 to 223 ° C, preferably 210 to 223 ° C. Is. When the main melting temperature of the polyester (II) is less than 180 ° C, the heat resistance may be poor. The melting temperature of the polybutylene terephthalate homopolymer is 223 ° C., and it is difficult to obtain polyester (II) having a higher melting temperature than this.

[Polyester (B)] In the present invention, the polyester (B) forming the polyester layer (B) is
It is a linear polyester mainly composed of an aromatic dicarboxylic acid component and a diol component.

Examples of the aromatic dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalene dicarboxylic acid, which may be used alone or in combination of two or more. May be Among them, terephthalic acid and isophthalic acid are preferable as the aromatic dicarboxylic acid component, and terephthalic acid is particularly preferable. Examples of the dicarboxylic acid copolymerization component other than the aromatic dicarboxylic acid component include aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. be able to.

As the diol component, HO-(CH
₂ ) n-OH (where n is an integer of 2 to 10) fatty acid diol (eg, ethylenetiglycol, 1,4-butanediol, hexanediol, etc.); HO-CH ₂ C
(R) ₂ —CH ₂ —OH (where R is an alkyl group having 1 to 4 carbon atoms) branched glycol (for example, neopentyl glycol or the like); diethylene glycol (DEG);
Examples include triethylene glycol (TEG); alicyclic diols (eg, cyclohexanedimethanol etc.); and polyoxyalkylene glycols (eg, polyethylene glycol, polypropylene glycol etc.), and ethylene glycol is particularly preferred. These may be used alone or in combination of two or more.

As the polyester (B), for example, polyethylene terephthalate copolymerized with isophthalic acid, polyethylene terephthalate copolymerized with aliphatic dicarboxylic acid such as isophthalic acid and adipic acid, 1,4-
Examples thereof include copolymerized polyethylene terephthalate such as polyethylene terephthalate copolymerized with butanediol, isophthalic acid and polyethylene terephthalate copolymerized with 1,4-butanediol.

On the other hand, among the above polyesters (B), particularly copolymerized polyethylene terephthalate has a main melting temperature of 2
10 to 260 ° C., crystallization temperature is 140 to 190 ° C.
It is preferable because the polyester layer (B) can be easily obtained.

In particular, the above-mentioned copolymerized polyethylene terephthalate (hereinafter abbreviated as "polyester (III)") has a main melting temperature of 210 to 260 ° C., particularly 215, depending on the copolymerization component and its ratio. ~ 240 ° C
The range and the crystallization temperature are in the range of 140 to 190 ° C. and the glass transition temperature is 65 ° C. or higher, particularly 70 ° C. or higher. When the main melting temperature of the polyester (III) is less than 210 ° C., the heat resistance of the polyester laminated film may be poor, and the outer surface coated film of the metal can may not be able to withstand heating during printing. The melting temperature of polyethylene terephthalate homopolymer is 260 ° C.
Which has a higher melting temperature than that of polyester (III)
Is difficult to obtain.

Further, when the glass transition temperature is less than 65 ° C.,
The polyester laminated film may be scratched or shavings of the polyester laminated film may occur during handling after laminating to a metal plate or during deep drawing can processing.

If the crystallization temperature is less than 160 ° C., the polyester layer (B) may be crystallized and embrittled due to frictional heat during deep drawing can manufacturing. On the other hand, if the crystallization temperature exceeds 190 ° C., the oriented crystallization of the film does not proceed even if it is subjected to various heat history from film formation to can manufacturing.
The strength and dimensional stability required for outer surface coating cannot be obtained.

Further, when the glass transition temperature is less than 65 ° C.,
The polyester laminated film may be scratched or shavings of the film may be generated during handling after laminating to a metal plate or during deep drawing can processing.

Polyethylene terephthalate copolymerized with an isophthalic acid component is particularly preferable as the polyester (III) because a polyester having a high glass transition temperature and a high crystallization temperature can be obtained.

[Polyester] Here, the main melting temperature, crystallization temperature and glass transition temperature of the polyesters such as polyester (I), polyester (II) and a melt mixture thereof, polyester (III) and the like are measured by a DSC measuring machine. (For example, Du Pont Instruments
910 DSC) and sample temperature is about 20 mg.

That is, the main melting temperature is the temperature at the apex of the highest peak among the melting peaks obtained when the sample is heated from room temperature to 290 ° C. at a heating rate of 20 ° C./minute (hereinafter referred to as “melting point I”). It is sometimes said that). When the modified polyester is used, for example, two or more melting peaks may occur when the transesterification reaction is not completely carried out. In this case, the peak temperature of the melting peak having the highest height is the melting point I, The peak temperature of the melting peak (sub-melting peak) with the next highest peak height is the sub-melting temperature (hereinafter "melting point").
II)). The crystallization temperature and the glass transition temperature of the sample are from room temperature to 20 ° C.
/ Min to 290 ° C, hold at 290 ° C for 3 minutes,
It is determined from the displacement temperature due to the glass transition and the temperature of the peak apex of the crystallization peak when the temperature is rapidly cooled to 20 ° C. or lower and the temperature is raised again at a temperature rising rate of 20 ° C./min.

Intrinsic viscosity of polyester in the present invention (measured at 30 ° C. with orthochlorophenol as a solvent)
Is 0.50 to 1.50 dl / g, more preferably 0.55 to 1.
It is preferably 00 dl / g. When the intrinsic viscosity is less than 0.50 dl / g, the polyester coated on the outer surface does not have a sufficient strength and elongation, and the impact resistance may be deteriorated, which is not preferable. On the other hand, when it exceeds 1.50 dl / g, the melt viscosity of the polymer is too high in the course of film formation, shearing heat generation becomes large, and thermal decomposition is remarkable, so that the hue of the polyester laminated film is inferior, which is not preferable.

The catalyst used for polymerizing the polyester of the present invention is not particularly limited, but antimony compounds, titanium compounds, germanium compounds and the like are preferably mentioned. Preferred examples of the antimony compound include antimony acid oxide and antimony acetate. Preferable examples of the titanium compound include titanium tetrabutoxide and titanium acetate. As the germanium compound, (a) amorphous germanium oxide, (b) fine crystalline germanium oxide, (c) germanium oxide dissolved in glycol in the presence of an alkali metal, an alkaline earth metal, or a compound thereof. ,
(D) A solution obtained by dissolving germanium oxide in water is preferred.

[Polyester Composition] The polyester composition (A) which constitutes the polyester layer (A) in the present invention comprises a polyester (A) having fine spherulite crystals of the polyester layer (A). To improve the retort whitening resistance and the metal color see-through property of the laminated film, 0.01 to 1% by weight of a lubricant having an average particle size of 0.01 to 2.5 μm is blended.

The average particle size of this lubricant is 0.01 to 2.5 μm.
m. Average particle size of lubricant is 2.5μ
If it exceeds m, coarse lubricant particles (for example, 1
(Particles of 0 μm or more) as a starting point to generate pinholes,
In some cases, fracture occurs.

Particularly preferred lubricants for preventing the occurrence of pinholes are spherical particles having an average particle size of 0.01 to 2.0 μm and a particle size ratio (major axis / minor axis) of 1.0 to 1.2. It is a monodispersed lubricant. Examples of such a lubricant include true spherical silica, true spherical silicone, true spherical calcium carbonate and the like.

The amount of lubricant in the polyester composition (A) is 0.01 to 1% by weight. In general, 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 spherical silica having an average particle diameter of 2.3 μm, and about 0.1% by weight in the case of spherical silica having an average particle diameter of 1.5 μm.

The polyester composition (B) constituting the polyester layer (B) in the present invention has an average content of the polyester (B) in order to improve the abrasion resistance and the metal color see-through property of the polyester laminated film. Particle size is 0.0
The lubricant is blended with 0.05 to 1% by weight of 1 to 1.0 μm.

The average particle size of this lubricant is 0.01 to 1.0 μm.
m. If the average particle size of the lubricant exceeds 1.0 μm, coarse lubricant particles (for example, particles of 4 μm or more) will fall off due to the processing such as deep drawing cans of the outer surface coated film, and the film may be damaged or broken. Occurs.

If the average particle size is less than 0.01 μm, the film will not slide well during the above-mentioned deep-drawing process, and the film will be scratched.

In order to prevent these problems due to falling off and poor slippage, a particularly preferable lubricant has an average particle size of 0.05 to 0.
It is a spherical monodispersed lubricant having a particle size ratio of 8 μm (major axis / minor axis) of 1.0. Examples of such a lubricant include true spherical silica, true spherical silicone, true spherical calcium carbonate, alumina and the like, and particularly true spherical silica and alumina are preferable from the viewpoint of preventing scratches on the film.

The lubricant of the polyester layer (B) is 0.05 to
1% by weight, it is preferable to add a small amount,
Further, addition of 0.05% by weight or more is most preferable for preventing scratches. For example, it is preferable to add about 0.3% by weight in the case of spherical silica having an average particle size of 0.1 μm, and about 0.1% by weight in the case of spherical silica having an average particle size of 0.5 μm.

The lubricant used in the polyester composition (A) or the polyester composition (B) may be either an inorganic lubricant or an organic lubricant. Examples of the inorganic lubricant include inorganic fine particles such as silica, alumina, titanium dioxide, calcium carbonate and barium sulfate. Examples of the organic lubricant include resin fine particles such as silicone resin and crosslinked polystyrene resin.

The lubricant is not limited to the above-mentioned externally added particles, but it is also possible to use, in combination, internally precipitated particles obtained by precipitating a part or all of the catalyst used in the production of polyester in the reaction step.

If necessary, the polyester composition (A) or the polyester composition (B) may include an antioxidant, a heat stabilizer, a viscosity modifier, a plasticizer, an adhesion improver, a nucleating agent, an ultraviolet absorber and a charging agent. Other additives such as inhibitors can be added.

[Polyester Layer (A)] The polyester layer (A) in the present invention has a melting point I of 180 to 240 ° C.
It is preferably 220 to 240 ° C. and the crystallization temperature is 10
It is 0 to 160 ° C., and the average diameter of spherical crystals generated by crystallization is 5 μm or less.

When the melting point I exceeds 240 ° C., the crystallization rate of the polyester is too high and the processability of the polyester laminated film is impaired. Also, the melting point I is 180 ° C.
If it is less than the above range, the heat resistance of the polyester is poor, and the outer surface coating film cannot withstand the heating during printing. The preferable range of the melting point I is 220 to 240 ° C.

When the crystallization temperature of the polyester layer (A) is less than 100 ° C., the crystallization speed of the polyester laminated film is too high, resulting in poor moldability during deep drawing of the metal can. Further, when the temperature exceeds 160 ° C., the crystallization rate of the polyester constituting the outer surface coating of the metal can becomes slow, and the spherulite crystals grow slowly and become large. Therefore, when the metal can is sterilized by retort, white spots are generated, and thus the appearance is deteriorated. It becomes defective.

Further, the polyester layer (A) in the present invention has a spherical crystal having an average diameter of 5 μm or less. When the average spherulite diameter exceeds 5 μm, large spherulites are generated when the polyester forming the outer surface coating of the metal can is heated, so the heat embrittlement resistance of the coating is poor,
In addition, for example, after sterilization by retort, the impact resistance, the retort whitening resistance, and the metal color see-through property of the coating become poor.

The polyester layer (A) having the melting point I, the crystallization temperature and the average spherulite diameter is, for example, the above-mentioned polyester composition (A) is mixed in the above proportions, melt-extruded and formed into a film, It can be produced by biaxial stretching and heat setting. In particular, a biaxially stretched polyester laminated film is used at 150 to 220 ° C., preferably 160
When heat-set at a temperature of up to 200 ° C., when the polyester laminated film is melted, a small amount of polyester microcrystals are present in the molten polymer in an unmelted state, and the crystallized peak temperature of the polyester laminated film is caused by the action of these crystallites. And the average spherulite diameter can be within the range of the present invention, which is preferable.

[Polyester Layer (B)] The polyester layer (B) in the present invention has a melting point I of 210 to 260 ° C. and a crystallization temperature of 140 to 190 ° C.

The polyester layer (B) having the melting point I and the crystallization temperature is prepared by mixing the above polyester composition (B) in the above ratio and melt coextruding it with the polyester layer (A) to form a laminated film. It can be manufactured by molding into a shape, biaxial stretching, and heat setting.

[Polyester Laminated Film] The polyester laminated film of the present invention comprises a polyester layer (A) and a polyester layer (B) laminated on one side thereof. The polyester layer (A) side is laminated with a metal plate. It is preferably used as a surface. By using the surface of the polyester layer (A) as a surface to be bonded to the metal plate, the adhesion between the polyester laminated film and the metal plate is improved, and the surface of the polyester layer (B) is used as the outer surface of the metal can. As a result, the function as the outer surface coating film can be satisfied.

The polyester laminated film of the present invention preferably has the following requirements (1) and (2).

(1) The refractive index in the film thickness direction is 1.4.
90 or more and 1.550 or less, more than 1.495 and 1.5
It is preferably 40 or less. This refractive index is 1.49
If it is less than 0, the moldability is insufficient, while 1.55
When it exceeds 0 (in the case of excessively low orientation), the structure is close to an amorphous structure, and the heat resistance tends 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 the Abbe refractometer, and the refractive index of each is measured with a monochromatic NaD ray. The mounting solution uses methylene iodide, and the measurement temperature is 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.

The total thickness of the polyester laminated film of the present invention is preferably 6 to 75 μm, and further 6
It is preferably 50 μm, particularly 10 to 20 μm. If the thickness is less than 6 μm, breakage or the like is likely to occur during processing, while if it exceeds 75 μm, the quality is excessive and uneconomical.

The thickness of the polyester layer (A) of the present invention is required to be 2 μm or more, preferably 4 μm or more, more preferably 5 μm or more. When the thickness of the polyester film layer (A) is less than 2 μm, white spots appear on the polyester layer (B) when the metal can is sterilized by retort.

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

The metal plate is heated to a temperature not lower than the melting point of the film, the films are laminated and then rapidly cooled, and the surface layer portion (thin layer portion) of the film in contact with the metal plate is made amorphous and brought into close contact.

An adhesive layer is preliminarily coated on the film with 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.

[0072]

EXAMPLES The present invention will be further described below with reference to examples. The characteristics and evaluation of the polyester film were carried out by the following methods.

(1) Melting point DuPont Instruments 910 type D
Approximately 20 mg of polyester layer from 20 ° C to 2 using SC
The peak temperature of the melting peak obtained when the temperature was raised to 90 ° C. at a rate of 20 ° C./minute was taken as the melting point. In the polyester layer (A), the peak temperature of the highest peak among the melting peaks was defined as the melting point I, and the peak temperature of the melting peak having the next highest peak was defined as the melting point II.

(2) Crystallization temperature DuPont Instruments 910 type D
Approximately 20 mg of polyester layer from 20 ° C to 2 using SC
When the temperature is raised to 90 ° C. at a rate of 20 ° C./minute, melted and held at 290 ° C. for 3 minutes, rapidly cooled to 20 ° C. or lower, and then again raised from 20 ° C. to 200 ° C. at a rate of 20 ° C./minute The peak apex temperature of the crystallization peak of was the crystallization temperature.

(3) Average spherulite diameter DuPont Instruments 910 type D
Approximately 20 mg of polyester layer from 20 ° C to 2 using SC
The temperature was raised to 90 ° C. at a rate of 20 ° C./min, melted and held at 290 ° C. for 3 minutes, rapidly cooled to below 20 ° C., and then again raised from 20 ° C. to 200 ° C. at a rate of 20 ° C. to crystallize. After cooling, the sample was rapidly cooled to below 20 ° C and the average spherulite diameter of the obtained sample was enlarged with a polarizing microscope at a magnification of about 400 times. by.

[Evaluation of Polyester Laminated Film] The polyester laminated film was evaluated as follows.

The polyester layer (A) side of the polyester laminated film was attached to one side of a 0.25 mm tin-free steel plate, and the polyester film for coating the inner surface of the metal can obtained in the following reference example was attached to the other side. Together, a coated steel plate was obtained. Next, this coated steel plate was formed into a side-surface seamless container (hereinafter abbreviated as a can) using a die and a punch. The following tests were carried out on this can, and each can was evaluated according to the following criteria.

(4) Deep drawing workability-1 ○: Both the inner and outer surfaces of the can were processed into the film without any abnormality, and no whitening or breakage was observed on the film on the inner or outer surface of the can. Δ: Whitening was observed on the top of the film inside and outside of the can. X: Film peeling and breakage are observed on a part of the film on the inside and outside of the can.

(5) Deep drawing workability-2 ○: Both the inside and the outside of the can were processed into a film without any abnormality, and the rust prevention test of the film on the outside of the can (1% NaCl water from the bottom of the can
It is dipped to a height of 0%, an electrode is inserted into NaCl water, and a current value is measured when a voltage of 6 V is applied with the can body as an anode. In the following "abbreviated as ERV test"), the current value is 0.
It shows 1 mA or less.

X: There is no abnormality in the film on both the inside and outside of the can, but the current value is 0.1 mA or more in the ERV test, and when the energized portion is observed under magnification, pinhole-like cracks originating from the coarse lubricant particles are found in the film. Is recognized.

(6) Impact resistance With respect to 10 cans that had been well-formed by deep drawing, water was fully poured, and after dropping from a height of 10 cm onto a PVC tile floor surface, E
As a result of the RV test, ◯: 0.1 mA or less for all 10 pieces. C: 0.1 mA or more for 1 to 5 pieces. X: 0.1 mA or more for 6 or more, or cracks of the film were already observed after dropping.

(7) Heat embrittlement resistance: 200 ° C. for 10 cans that were well drawn.
After heating and holding for 5 minutes, the above-mentioned impact cracking resistance was evaluated. Good: 0.1 mA or less for all 10 pieces. C: 0.1 mA or more for 1 to 5 pieces. X: 0.1 mA or more for 6 or more, or cracks were already observed in the film after heating at 200 ° C. for 5 minutes.

(8) Retort whitening resistance: 200 ° C. for 10 cans that were well drawn.
After heating and holding for 3 minutes, retort treatment was performed at 130 ° C. for 30 minutes in a steam sterilizer, and the change in appearance before and after the treatment was observed. ◯: All 10 pieces showed no change in appearance. X: White spots were found on the outer surface film of the cans for 1 or more.

(9) Metallic color transparency With respect to a can with good deep-drawing, the result of observing the inner tin-free steel part through the appearance coating was as follows: ◯: The tin-free steel part had almost the same gloss. Seen through X: Observed in a state where the gloss of the tin-free steel part was insufficient (cloudy).

(10) Scratches on the surface of the coated film ◯: 100 scratches were found and no scratches were found. Δ: 1 to 5 if 100 scratches were found and small scratches were included
%Occurred. ×: 100 inspections revealed that 6% of the large scratches were mixed.

(11) Comprehensive Evaluation Good: All of the above evaluations of cans are good. Δ: The above-mentioned evaluation of cans is Δ and ○. Poor: Poor in the above evaluation of the can.

In the above evaluation, ◯, Δ and × indicate the following.

◯: Evaluation result is good. Δ: The evaluation result is slightly good. X: Poor evaluation result.

Example 1 Polyethylene terephthalate (polyester (I): intrinsic viscosity 0.70 dl / g) containing 0.3% by weight of aggregated silica having an average particle size of 1.5 μm and copolymerized with 9% by mole of isophthalic acid. ) 100 parts by weight,
A polyester composition containing 44 parts by weight of polybutylene terephthalate homopolymer (polyester (II): intrinsic viscosity 0.87 dl / g) was melt extruded at 280 ° C. as a polyester layer (A), while having an average particle diameter of 0.1 μm. Containing 0.35% by weight of agglomerated silica and containing 11 parts of isophthalic acid.
72% by weight of mol% copolymerized polyethylene terephthalate (polyester (III): intrinsic viscosity 0.70 dl / g) was melt extruded at 280 ° C. as a polyester film layer (B) and laminated, and rapidly solidified on a rotary cooling drum. To obtain an unstretched film. Next, this unstretched film was stretched 3.2 times in the machine direction at 120 ° C., and then 110 ° C.
Then, the film was stretched 3.3 times in the transverse direction and then heat-set at 180 ° C. to obtain a polyester film for coating the outer surface of a metal can having a thickness of 15 μm.

Melting point I of the obtained polyester layer (A),
The melting point II, the crystallization temperature, the average spherulite diameter, the melting point of the polyester layer (B) and the crystallization temperature are shown in Table 3, and the evaluation results of the film are shown in Table 4.

[Examples 2-10 and Comparative Examples 1-5, 7-
12] The polyester (I), polyester (II) and lubricant shown in Table 1 are used as the polyester layer (A) in the blending amounts and blending ratios shown in Table 1, and the polyester (III) shown in Table 2 as the polyester layer (B). Further, a polyester film was obtained in the same manner as in Example 1 except that the lubricant was used in the use amounts and blending ratios shown in Table 2 and the stretching and heat setting were performed under the conditions shown in Table 3. The melting point, crystallization temperature and average spherulite diameter of the obtained film are shown in Table 3, and the evaluation results of the film are shown in Table 4.

Comparative Example 6 A polyester film was obtained in the same manner as in Example 1 except that the polyester film was not heat set. The melting point, crystallization temperature and average spherulite diameter of the obtained film are shown in Table 3, and the evaluation results of the film are shown in Table 4.

Reference Example Polyethylene terephthalate copolymerized with 12 mol% of isophthalic acid (having an intrinsic viscosity of 0.6
4, having a melting point of 228 ° C. and containing 0.3% by weight of titanium dioxide having an average particle size of 0.3 μm) was melt-extruded at 280 ° C. and rapidly cooled and solidified on a rotary cooling drum to obtain an unstretched film. This unstretched film is 100
The film was stretched 3.0 times at 0 ° C and 3.0 times at 120 ° C in the transverse direction, and then heat set at 190 ° C to obtain a polyester film for coating the inner surface of a metal can having a thickness of 20 µm.

[0094]

[Table 1]

[0095]

[Table 2]

[0096]

[Table 3]

[0097]

[Table 4]

As is clear from the results shown in Table 4, the polyester laminate of the present invention has excellent deep drawing workability for coating the outer surface of a metal can, and the film coated on the outer surface of the metal can has impact resistance. It was excellent in crackability, heat embrittlement resistance, retort whitening resistance, and metal color transparency.

[0099]

EFFECT OF THE INVENTION The polyester laminate of the present invention has excellent deep drawing workability when the outer surface coating of a deep drawn metal can is used, and the polyester laminate of the present invention is used for the outer surface of a metal can. Since the coating film coated with is excellent in impact resistance, heat embrittlement resistance, retort whitening resistance, and metal color transparency, it is useful for coating the outer surface of a deep-drawn metal can.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08K 3/36 KJS C08K 3/36 KJS C08L 67/02 LPD C08L 67/02 LPD // B29K 67: 00 B29L 9:00 (72) Inventor Tetsuo Yoshida 3-37-19 Oyama, Sagamihara City, Kanagawa Teijin Limited Sagamihara Research Center

Claims (5)

[Claims] 1. A polyester (A) containing an aromatic dicarboxylic acid component and a diol component as main components and having an average particle size of 0.0.
Polyester layer (A) comprising a polyester composition (A) in which 0.01 to 1% by weight of a lubricant of 1 to 2.5 μm is blended
On one surface of the polyester (B) containing an aromatic dicarboxylic acid component and a diol component as main components, the average particle size is 0.01 to
A polyester laminated film in which a polyester layer (B) made of a polyester composition (B) in which 0.05 to 1% by weight of a lubricant having a thickness of 1.0 μm is mixed is laminated, and the polyester layer (A) is a main component during heating. Melting temperature is 180-240
C., the crystallization temperature at the time of rapid reheating is 100 to 160.degree. C., and the average diameter of the spherical crystals generated by the crystallization is 5 .mu.m.
m or less, and the polyester layer (B) has a main melting temperature of 210 to 260 ° C. at the time of temperature increase and a crystallization temperature of 140 to 190 ° C. at the time of rapid reheating. 2. The polyester laminated film according to claim 1, wherein the polyester layer (A) surface is laminated on a metal plate and used for coating the outer surface of a deep-drawn metal can. 3. The polyester (A) is obtained by melt mixing 1 to 65 parts by weight of polybutylene terephthalate and / or copolymerized polybutylene terephthalate with 100 parts by weight of polyethylene terephthalate and / or copolymerized polyethylene terephthalate. The polyester laminated film according to claim 1 or claim 2. 4. The polyester (B), which comprises a copolymerized polyethylene terephthalate as a main component, 1.
Alternatively, the polyester laminated film according to claim 3. 5. The polyester laminated film according to claim 1, wherein the polyester laminated film is biaxially stretched and heat-fixed.