JPH11216826A - Laminate for manufacturing can and seamless can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal-polyester laminate wherein migration of low mol.wt, components existing inevitably in a polyester film into the content is suppressed as low as possible and generation of turbidity is suppressed on high temp. treatment and during long-term preservation and which has excellent combination of impact resistance (especially dent resistance), processability and content resistance and a seamless container formed of the laminate. SOLUTION: In a laminated body for manufacturing cans consisting of a metal base body and a thermoplastic polyester layer provided on the surface of the base body, the thermoplastic polyester layer consists of a laminated film provided with a surface layer (I) consisting of a copolymerized polyester or a blended polyester wherein amt. of naphthalenedicarboxylic acid ingredient per the whole basic carboxylic acid ingredient is 1.0-95 mole% and an underlayer (II) consisting of a polyester or a polyester compsn. contg. terephthalic acid ingredient and with a glass transition point (Tg) of at most 65 deg.C and with the difference between glass transition point of the surface layer and that of the underlayer of 10 deg.C or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated body for cans and a seamless can produced by using the laminated body. More particularly, the present invention relates to a high-temperature sterilized filling container for coffee beverages, teas and the like. The present invention relates to a laminate which can be used, has remarkably improved storage stability at high temperature, and has excellent combination of impact resistance (dent resistance), workability and content resistance, and a seamless container molded from the laminate.

[0002]

2. Description of the Related Art A laminate in which a metal material is coated with a thermoplastic polyester film has been known for a long time as a material for cans, and this laminate is subjected to drawing or drawing / ironing to prepare beverages and the like. It is also well known to provide a seamless can for filling.

[0003] From the viewpoints of processability, corrosion resistance, flavor retention and the like, a thermoplastic polyester to be laminated on a metal material is mainly composed of an ethylene terephthalate unit and, if desired, a polyester or a copolyester containing other ester units. Has been used.

Japanese Patent Application Laid-Open No. 7-82391 discloses a biaxially oriented film comprising a copolymerized polyester containing a lubricant having an average particle size of 2.5 μm or less, wherein the copolymer is 2,6-naphthalenedicarbon. An acid component composed of 80 to 95 mol% of an acid and 5 to 20 mol% of an aliphatic linear dicarboxylic acid having 2 to 10 methylene groups, and a glycol component mainly composed of ethylene glycol, and having an intrinsic viscosity ([η] A) a polyester film for laminating and processing all metals, which has a molecular weight of 0.5 to 0.7.

[0005] Japanese Patent Application Laid-Open No. 9-52337 discloses that A having at least two layer structures,
The layer is composed of 70 to 30% by weight of a polyester having the following ester unit X as a main repeating unit, and the following ester unit Y:
Is a polyester having 30 to 70 as a main repeating unit.
The layer B, which is composed of a mixed polyester blended by weight% and forms the other surface, has a crystal melting enthalpy of 25.
J / g or less, a polyester having a melting point of 165 to 210 ° C. or a mixed polyester, and the difference between the maximum value and the minimum value of the glass transition point of the polyester constituting each layer is 10
C. or lower and an impact resistance index of 4 or more, wherein the polyester unit for metal coating is described as follows: Ester unit X: ethylene terephthalate or ethylene naphthalate Ester unit Y: butylene terephthalate or butylene naphthalate I have.

[0006]

A seamless can formed from a laminate coated with a thermoplastic polyester has been evaluated as satisfactory for corrosion resistance, but in recent years rationalization and efficiency of retort sterilization have been improved. Therefore, a high-temperature retort is desired. In hot retort sterilization,
It was found that the amount of low molecular weight components eluted from the polyester film on the inner surface side was increased.

[0007] That is, under high-temperature, high-humidity heat conditions, the amount of the low-molecular-weight component necessarily contained in the film migrates into the contents, and among the low-molecular-weight components, the relatively high-molecular-weight component is relatively high. Therefore, the extraction of components that are originally extremely low in solubility in an aqueous solution becomes remarkable. The amount that is transferred into the contents is treated at high temperatures, at least far below the limits set by the Ministry of Health and Welfare Notification Regulations and the US FDA Regulations,
In addition, when stored for a long period of time, the relatively high molecular weight components that have migrated into the contents may aggregate to increase the particle size and cause turbidity, which is not psychologically preferable.

The present inventors have previously described a can-forming laminate comprising a metal substrate and a thermoplastic polyester layer provided on the surface of the substrate, wherein the thermoplastic polyester layer has an ethylene terephthalate unit as the main component. A terephthalate-based polyester (A) and an ethylene-naphthalate-based polyester (B) having ethylene naphthalate units as a main component have an amount of the naphthalenedicarboxylic acid component of 1.0 to 95 mol% based on the total basic carboxylic acid component. In the case of a laminate formed from a blend containing the polyester resin and having a transesterification amount in a specific range, low-molecular weight components which are inevitably present in the polyester film migrate into the content during high-temperature treatment and long-term storage. Is suppressed as much as possible,
It has been proposed that the occurrence of turbidity be suppressed (patent pending).

However, although the above proposal is effective in suppressing the generation of turbidity in cans that have undergone thermal history at high temperatures, the combination of impact resistance, workability and content resistance required for actual canned products is not considered. Still, it was not satisfactory enough.

Practical impact resistance required for actual canned products includes what is called dent resistance. This means that even if the canned product falls or collides with each other and a dent called a dent occurs on the canned product, the adhesion and coverage of the coating can be completely maintained. Is required. That is, if the coating peels off or pinholes or cracks enter the coating in the dent test, metal elution or leakage due to pitting corrosion occurs from this portion, causing a problem of losing the preservability of the contents. . In general, polyesters having excellent content resistance are generally lacking in the property of absorbing or mitigating impact during a dent test, and the provision of these properties is an important issue.

In the case of a seamless can formed from a polyester laminate, draw-forming and ironing of the seamless can are not only severe, but the neck-in process and the flange Secondary processing such as processing and winding processing is indispensable, and a laminated body processed into a seamless can must still maintain workability enough to withstand these processings. In the case of polyester having excellent content resistance, it is customary to undergo a high degree of molecular orientation during processing into a seamless can. In such a high orientation state, generally, the processability is considerably reduced. Furthermore, in the case of cans, the effects of heat treatment on the coating cannot be avoided. That is, it is common to print on the outer surface of the can to display the contents and the like,
The effect of heating to print the printing ink occurs on the polyester film. Polyester tends to crystallize (become brittle) by heating, which reduces dent resistance and also reduces workability in neck-in processing, winding processing, and the like.

Accordingly, an object of the present invention is to minimize the migration of low molecular weight components, which are necessarily present in a polyester film, into the contents during high-temperature treatment and long-term storage, thereby suppressing the occurrence of turbidity. Another object of the present invention is to provide a metal-polyester laminate excellent in the combination of impact resistance (particularly dent resistance), workability and content resistance, and a seamless container formed from the laminate.

[0013]

According to the present invention, there is provided a laminate for cans comprising a metal substrate and a thermoplastic polyester layer provided on the surface of the substrate, wherein the thermoplastic polyester layer comprises: When the amount of the naphthalenedicarboxylic acid component per basic carboxylic acid component is l. A surface layer composed of a copolymerized polyester or a blended polyester containing 0 to 95 mol%, and a lower layer composed of a polyester or a polyester composition containing (II) a terephthalic acid and having a glass transition point (Tg) of 65 ° C. or less. And a difference between the glass transition point of the surface layer and the glass transition point of the lower layer is greater than 10 ° C., and a laminated body for a can made of a laminated film is provided. According to the present invention, there is also provided a seamless can formed by drawing or laminating the above laminate.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Action] The laminate for cans of the present invention comprises:
The thermoplastic polyester layer comprises a metal substrate and a matured polyester layer provided on the surface of the substrate. In the present invention, the thermoplastic polyester layer has (I) an amount of naphthalenedicarboxylic acid component of 1 per basic carboxylic acid component. 0.0 to 9
A surface layer of a copolymerized polyester or a blended polyester containing 5 mol%, and (II) a terephthalic acid component-containing glass transition point (Tg) of 65 ° C.
It is characterized by having a lower layer comprising the following polyester or polyester composition, and a difference between the glass transition point of the surface layer and the glass transition point of the lower layer is larger than 10 ° C.

Polyethylene terephthalate (PET)
Is crystalline and has a high melting point, and has excellent properties such as tensile strength, impact resistance, and bending fatigue resistance. Have. For example, when examining the relationship between the aging time and the retention of elongation in an autoclave treatment at 130 ° C., polyethylene terephthalate shows that the retention of elongation is about 85% in 20 hours, about 70% in 40 hours, and about 70% in 60 hours. When it is 50% or less, it is recognized that the retention of elongation significantly decreases with time. It is considered that this is because polyethylene terephthalate undergoes hydrolysis under high-temperature moist heat conditions.

On the other hand, polyethylene naphthalate (PEN) is not less than 90% in 20 hours and 80% or more in 40 hours even in the above-mentioned autoclave treatment.
At 60% or more at 0 hours, the retention of elongation with time is high, and by incorporating ethylene naphthalate units into the polyester or blending the ethylene terephthalate-based polyester, deterioration over time under high-temperature, moist heat conditions is effectively prevented. It will be appreciated that this is possible.

In the present invention, it is surprising that the naphthalenedicarboxylic acid component is present by copolymerization or blending so that the amount of the naphthalenedicarboxylic acid component per total basic carboxylic acid component of the surface layer polyester is 1.0 to 95 mol%. To
It was found that the preservability of the contents under high-temperature, high-humidity conditions was significantly improved. Occurrence of turbidity during retort sterilization in a seamless can having a polyester layer in which the content of the naphthalenedicarboxylic acid component is less than the above range,
For example, while the turbidity is on the order of 4.2 (see Comparative Example 2 described later), in a seamless can provided with a polyester layer containing a naphthalenedicarboxylic acid component in the above-described ratio, the occurrence of turbidity is reduced. It can be suppressed to the order of one digit lower in degrees.

In a seamless can having a polyester layer, the occurrence of turbidity is due to the elution of oligomers in the polyester. In the specific surface layer polyester of the present invention, the elution of the oligomers is remarkably suppressed. . This fact has been found as a phenomenon by many experiments of the present inventors, and the present invention is not limited by the following reasons, but the following is considered. .

In general, the free volume refers to the volume not occupied by constituent particles (in this case, polymer chains) of the volume occupied by a substance. According to the literature, the free volume fraction of polyethylene terephthalate is 0.39 at 300 ° K, 0.41 at 400 ° K, and 0.1 at 500 ° K.
44, whereas for polyethylene naphthalate, 0.32 at 300 ° K, 0.33 at 400 ° K,
0.34 at 500 ° K, indicating a smaller free volume fraction than polyethylene terephthalate. That is, in the surface layer polyester used in the present invention, the free volume is reduced as compared to polyethylene terephthalate due to the presence of the naphthalenedicarboxylic acid component. Is considered to be suppressed.

In the present invention, a polyester containing a terephthalic acid component and a polyester resin having a glass transition point (Tg) of 65 ° C. or lower is provided as a lower layer in combination with the above-mentioned surface layer polyester, and the glass transition of the surface layer is provided. It is important to make the difference between the point and the glass transition point of the lower layer larger than 10 ° C. in order to improve impact resistance and workability without impairing the content resistance.

That is, the polyester of the above surface layer generally has a high glass transition point and lacks the ability to absorb or alleviate impact or the like. However, in the present invention, the polyester containing a terephthalic acid component below the surface layer and containing By providing a polyester layer having a transition point of 65 ° C. or lower and a glass transition point of at least 10 ° C. lower than the glass transition point of the surface layer, the impact is absorbed or moderated, and the resin layer is peeled off during the dent test, It is possible to prevent the occurrence of pinholes, cracks, and the like, and to further improve the formability into a seamless can and the secondary workability such as neck-in processing and flange processing of the formed can.

In the present invention, in order to enhance impact resistance and improve processability, it is essential to use the above-mentioned lower layer polyester, but at the same time, the above-mentioned specific surface layer polyester also has an impact resistance and processability. Is helping to improve.

In the case of a copolyester having a low copolymerization ratio of a naphthalenedicarboxylic acid component or a blend polyester having a low blend ratio of polyethylene naphthalate, poor processability such as whitening of a portion having a high degree of processing at the upper part of the can is inferior. Also, the dent resistance is poor (see Comparative Examples 1 and 3).
On the other hand, when the blend ratio of the ethylene naphthalate-based polyester is large, a crack is generated in the upper part of the can where the degree of processing is large, and the molding becomes difficult (Comparative Example 4). On the other hand, by using a copolymerized polyester or a blended polyester containing a naphthalenedicarboxylic acid component in a specific ratio as a surface layer, the moldability into a seamless can is improved, and the dent resistance of the can is improved. (See Examples 1 to 4).

[Outline of Seamless Can and Laminated Body] In FIG. 1 showing an example of the seamless can of the present invention, the deep drawn can 1 is formed by bending and stretching of the above-described polyester-metal laminate and ironing. And a side wall 3. A flange portion 5 is formed at an upper end of the side wall portion 3 via a neck portion 4 as desired. This can 1
In this case, the side wall portion 3 is thinned by bending and stretching and ironing so as to have a thickness of 30 to 100%, particularly 30 to 85% of the original thickness of the laminate.

In FIG. 2 showing an example of the cross-sectional structure of the side wall portion 3, the side wall portion 3 comprises a metal base 6 and a polyester-based laminated film 7. The outer coating 8 is formed on the metal substrate 6, and the outer coating 8 may be the same as the inner coating 7 of the film, or may be an ordinary can coating or resin film coating. . The laminated film 7 has an amount of naphthalenedicarboxylic acid component per total basic carboxylic acid component of 1. A surface layer 7a made of a copolymerized polyester or a blended polyester contained so as to be 0 to 95 mol%, and containing terephthalic acid and having a glass transition point (Tg) of 65 ° C. or lower and at least lower than the glass transition point of the surface layer. Lower layer 7b made of polyester or polyester composition having a glass transition point lower by 10 ° C.
And

In FIG. 3 showing another example of the cross-sectional structure of the side wall portion, the same as FIG. 3 except that an adhesive primer layer 9 is provided between the composite polyester layer 7 and the metal base 6. is there. In any of these cases, the cross-sectional structure of the bottom portion 2 is the same as the cross-sectional structure of the side wall portion 3 except that the bottom portion 2 has not been subjected to a thinning process.

[Metal Plate] In the present invention, various surface-treated steel plates and light metal plates such as aluminum are used as the metal plate.

As the surface-treated steel sheet, a cold-rolled steel sheet is annealed and then subjected to secondary cold rolling, and is subjected to one or more surface treatments such as zinc plating, tin plating, nickel plating, electrolytic chromic acid treatment, and chromic acid treatment. Can be used.
An example of a suitable surface-treated steel sheet is an electrolytic chromic acid-treated steel sheet, particularly provided with a chromium metal layer of 10 to 300 mg / m ² and a chromium oxide layer of 1 to 50 mg / m ² (in terms of chromium metal). This is excellent in the combination of coating film adhesion and corrosion resistance. Another example of a surface-treated steel plate is a hard tin plate having a tin plating amount of 0.5 to 11.2 g / m ² . This tin plate is desirably subjected to chromic acid treatment or chromic acid-phosphoric acid treatment so that the amount of chromium is 1 to 30 mg / m ^{2 in} terms of metal chromium.

As still another example, an aluminum-coated steel sheet subjected to aluminum plating, aluminum pressure welding, or the like is used.

As the light metal plate, an aluminum alloy plate is used in addition to a so-called aluminum plate. An aluminum alloy plate excellent in corrosion resistance and workability has a Mn: 0.
2 to 1.5% by weight, Mg: 0.8 to 5% by weight, Z
n: 0.25 to 0.3% by weight, Cu: 0.15 to 0.25% by weight, with the balance being Al. It is desirable that these light metal plates have also been subjected to a chromic acid treatment or a chromic / phosphoric acid treatment such that the chromium amount becomes 20 to 300 mg / m ^{2 in} terms of chromium metal.

The thickness of the metal plate, that is, the thickness of the bottom of the can (tB)
) Varies depending on the type of metal, the purpose or the size of the container, but generally preferably has a thickness of 0.10 to 0.50 mm. Among them, in the case of a surface-treated steel sheet, 0.10 to 0. It is preferable to have a thickness of 0.30 mm, and in the case of a light metal plate, a thickness of 0.15 to 0.40 mm.

[Composite Polyester Layer] The composite polyester layer used in the present invention has (I) an amount of naphthalenedicarboxylic acid component of 1 / total basic carboxylic acid component. 0 to 9
A surface layer composed of a copolymerized polyester or a blended polyester containing 5 mol%, and a lower layer composed of a polyester or a polyester composition containing (II) a terephthalic acid and having a glass transition point (Tg) of 65 ° C. or less. Become.

(I) Surface Layer The surface layer may be a copolymerized polyester or a blended polyester as long as the naphthalenedicarboxylic acid component is contained in the above amount. The naphthalenedicarboxylic acid is preferably naphthalene-2,6-dicarboxylic acid, but may naturally contain other naphthalenedicarboxylic acid components.

(I-1) Copolyester The copolyester contains the naphthalenedicarboxylic acid component in the above-mentioned ratio, but the other carboxylic acid components include terephthalic acid, isophthalic acid, P-β-oxy Ethoxybenzoic acid, diphenoxyethane-4,4 '
-Dicarboxylic acid, 5-sodium sulfoisophthalic acid,
Hexahydroterephthalic acid, naphthalenedicarboxylic acid,
Adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, etc., but terephthalic acid (TA)
A carboxylic acid component mainly composed of

As the alcohol component of the copolymerized polyester, ethylene glycol, propylene glycol,
1,4-butanediol, neopentyl glycol,
1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A,
Alcohol components such as trimethylolpropane and pentaerythritol can be mentioned, but alcohol components mainly composed of ethylene glycol (EG content: 95 mol% or more) are preferred.

The copolymerized polyester should have a molecular weight in the range of forming a film, and has an intrinsic viscosity [η] of 0.5 or more, especially 0.5 to 1 when measured using a phenol / tetrachloroethane mixed solvent as a solvent. The range of 0.5 is good in terms of barrier properties against corrosive components and mechanical properties.

(II-2) Blend Polyester The blend polyester used for the surface layer is a polyester (A) mainly composed of ethylene naphthalate units and another polyester, particularly a polyester mainly composed of ethylene terephthalate units. The amount of the naphthalenedicarboxylic acid component per carboxylic acid component is 1.0 to 95.
It is formed from a blend that is blended to give a mole%.

Ethylene naphthalate polyester (A) As the ethylene naphthalate polyester (A),
In addition to polyethylene naphthalate, a copolymerized polyester mainly composed of ethylene naphthalate units is used. The naphthalenedicarboxylic acid preferably accounts for at least 50 mol% of the acid component. It is desirable that ethylene glycol accounts for 95 mol% or more, particularly 98 mol% or more of the alcohol component.

Acid components other than naphthalenedicarboxylic acid include terephthalic acid, isophthalic acid, P-β-oxyethoxybenzoic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, and hexahydroterephthalic acid. Acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid and the like can be mentioned.

As the alcohol component other than ethylene glycol, those exemplified above are used.

Ethylene terephthalate-based polyester (B) As the ethylene terephthalate-based polyester (B), a copolymerized polyester mainly composed of ethylene terephthalate units is used in addition to polyethylene terephthalate. Terephthalic acid preferably accounts for at least 50 mol% of the acid component. It is desirable that ethylene glycol accounts for 95 mol% or more, particularly 98 mol% or more of the alcohol component. A polyester comprising the above amounts of terephthalic acid and ethylene glycol is preferred in terms of molecular orientation, barrier properties against corrosive components and odor components, and the like.

Acid components other than terephthalic acid include isophthalic acid, P-β-oxyethoxybenzoic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, and naphthalenedicarboxylic acid. Acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid and the like can be mentioned.
Copolyester containing isophthalic acid has a large improvement in moldability and dent resistance by lowering the melting enthalpy of the copolymer, and has a large barrier effect against various components, flavor components and corrosion components. It has the characteristic that it has a low adsorptivity. Further, as the alcohol component other than ethylene glycol, propylene glycol,
1,4-butanediol, neopentyl glycol,
1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A,
Alcohol components such as trimethylolpropane and pentaerythritol can be mentioned.

The blended polyester should have a molecular weight in the range of film formation, and the intrinsic viscosity [η] measured using a phenol / tetrachloroethane mixed solvent as a solvent is 0.5 or more, especially 0.5 to 1. The range of 5 is good in terms of barrier properties against corrosive components and mechanical properties.

Ethylene naphthalate polyester (A) and ethylene terephthalate polyester (B)
Can be manufactured by dry blending or melt blending.In the former case, the resin may be mixed with a blender, Henschel mixer, super mixer, etc., and fed directly to the hopper of the extruder. Alternatively, kneading may be performed with a twin-screw extruder, kneader, Banbury mixer, or the like.

(II) Lower Layer The lower layer of the composite polyester coating contains a polyester or polyester composition containing a terephthalic acid component and having a glass transition point of 65 ° C. or lower.

As the polyester or polyester composition used for the lower layer, any one can be used as long as it satisfies the above conditions. However, alcohol components mainly composed of ethylene glycol and butylene glycol, terephthalic acid and isophthalic acid can be used. It is preferably derived from an acid component containing at least one of naphthalenedicarboxylic acid and naphthalenedicarboxylic acid, and more preferably derived from an acid component containing an aliphatic dibasic acid as the acid component.

More preferably, the polyester or polyester composition used for the lower layer comprises (I) a polyethylene terephthalate segment, (II) a polyester segment derived from butylene glycol and an aromatic dibasic acid, and (III) butylene. And polyester segments derived from glycols and aliphatic dibasic acids. In this specification, a segment is a commonly used meaning, that is, the smallest unit in a polymer chain used to statistically express the properties of a chain polymer.

In the polyester used in the present invention,
The ethylene terephthalate segment (I) is a component that imparts mechanical strength, rigidity and heat resistance to the coating to be formed, while the polyester segments (II) and (III) are glass transitions of the formed polyester coating. It is a component that increases the crystallization speed at the same time as lowering the temperature, generates fine crystals, improves the workability of the polyester coating layer, and further improves the dent resistance when applied to can applications. By using in combination with the lower layer of the polyester coating layer, the impact resistance can be improved without lowering the heat resistance.

That is, by incorporating the polyester segment (II) and the polyester segment (III) at the same time, the current value due to the metal exposure after the dent test can be suppressed to about three orders of magnitude lower.

In the polyester or polyester composition constituting the lower layer (II), I: II: III = 10-90: 7-81: 3-54 with the total amount being 100 parts by weight.
Weight ratio, especially I: II: III = 10-70: 15-6
It is preferable to contain them in a weight ratio of 0:15 to 54. As described above, these polyester segments are only required to be statistically contained in the polyester or polyester composition at the above composition ratio, and the state of their presence is not particularly limited. For example, it may be a blend of polyesters or a copolyester. However, in the present invention, it is preferable to use a blend of (I) a polyester mainly containing an ethylene terephthalate segment and a copolymerized polyester containing a polyester segment (II) and a polyester segment (III). Hereinafter, this example will be described in detail, but the present invention is not limited to this case.

The ethylene terephthalate crystalline polyester used as one component of the lower layer (II) in the present invention is:
Crystalline polyesters in which ethylene terephthalate units account for at least 80 mol% or more of the ester repeat units are preferred. Homopolyethylene terephthalate is preferred in terms of heat resistance, but a copolymerized polyester containing a small amount of an ester unit other than the ethylene terephthalate unit may be used.

Acid components other than terephthalic acid include isophthalic acid, orthophthalic acid, P-β-oxyethoxybenzoic acid, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium Preference is given to at least one polybasic acid selected from the group consisting of sulfoisophthalic acid, hexahydroterephthalic acid, adipic acid, sebacic acid, dimer acid, trimellitic acid and pyromellitic acid. Polyester containing isophthalic acid and / or naphthalenedicarboxylic acid as a copolymer component is excellent in content resistance, content flavor retention and the like.

The diol component is preferably composed only of ethylene glycol, but other diol components such as propylene glycol, 1,4-butanediol, diethylene glycol, and the like may be used within the range not impairing the essence of the present invention. , 6-hexylene glycol, pentaerythritol, dipentaerythritol, cyclohexane dimethanol, bisphenol A ethylene oxide adduct or the like, or two or more thereof may be contained.

The ethylene terephthalate crystalline polyester to be used should have a molecular weight in the range of film formation, and the intrinsic viscosity [IV] measured using a phenol / tetrachloroethane mixed solvent as a solvent is 0.5 or more, especially 0. It may be in the range of .5 to 1.5.

The copolymerized polyester used as the other component of the lower layer (II) in the present invention comprises (II) an ester unit derived from butylene glycol and an aromatic dibasic acid and (II)
I) Copolymerized polyester containing ester units derived from butylene glycol and an aliphatic dibasic acid in the above-mentioned quantitative ratio.

As the aromatic dibasic acid constituting the ester unit (II), terephthalic acid, isophthalic acid, orthophthalic acid, P-β-oxyethoxybenzoic acid, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4 , 4 '
-Dicarboxylic acid, 5-sodium sulfoisophthalic acid,
Trimellitic acid, pyromellitic acid, 3,4,3 ', 4'
-Biphenyltetracarboxylic acid and the like, with terephthalic acid being preferred.

Examples of the aliphatic dibasic acid component constituting the ester unit (III) include succinic acid, azelaic acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecandioic acid, tetradecandioic acid, dimer acid and the like. Although a long chain aliphatic dibasic acid is preferable because of its great effect of lowering Tg, adipic acid is particularly preferable from the viewpoint of industrial production.

The diol component is preferably composed of only butylene glycol. However, as long as the essence of the present invention is not impaired, diol components other than butylene glycol include ethylene glycol, propylene glycol and
It may contain one or more of diethylene glycol, 1,6-hexylene glycol, cyclohexane dimethanol, and an ethylene oxide adduct of bisphenol A.

The copolymerized polyester preferably contains the aromatic ester unit (II) and the aliphatic ester unit (III) in the above-mentioned ratio, and when the content of the aliphatic ester unit is smaller than the above range, The impact resistance (dent resistance) tends to be insufficiently improved, while if it exceeds the above range, the heat resistance, workability, barrier properties against corrosive components and the like of the coating tend to decrease.

This copolymerized polyester should also have a molecular weight in the range of forming a film, and has an intrinsic viscosity [η] of 0.5 or more, especially 0.5 to 0.5 as measured using a phenol / tetrachloroethane mixed solvent as a solvent. It is better to be in the range of 1.5.

In the present invention, the ethylene terephthalate-based polyester and the above-mentioned specific copolymerized polyester are blended and used in the above-mentioned quantitative ratio. The mixing may be performed by dry mixing or by melt blending.

The polyester composition used for the lower layer (II) in the present invention comprises a blend of an ethylene terephthalate-based polyester and a copolymerized polyester.
In connection with the fact that it should have a glass transition point of 5 ° C. or less, it was found that the melting point (Tm ₁ ) specific to the ethylene terephthalate-based polyester and the melting point (Tm ₂ ) specific to the copolymerized polyester were determined by differential thermal analysis. Show. Of course, the height of each peak depends on the mixing ratio of both components. This fact indicates that the ethylene terephthalate-based polyester and the copolymerized polyester exist mainly as independent phases even in a homogeneous composition.

The polyester or polyester composition used for the lower layer in the present invention may contain a resin compounding agent known per se. For example, by adding an antioxidant, particularly an antioxidant having a molecular weight of 400 or more, the heat resistance of the laminate for cans can be significantly improved.

Examples of the above-mentioned polymer phenolic antioxidant include tetrakis [methylene-3 (3 ′, 5 ′)
-Di-t-butyl-4'-hydroxyphenyl) propionate) methane (molecular weight 1177.7), 1,1,3
-Tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (molecular weight 544.8), 1,3,5
-Trimethyl-2,4,6-tris (3,5-di-t-
Butyl-4-hydroxybenzyl) benzene (molecular weight 7
75.2), bis [3,3'-bis- (4'-hydroxy-3'-tert-butylphenyl) butyric acid]
Glycol ester (molecular weight 794.4), 1,3,5
-Tris (3'5'-di-t-butyl-4'-hydroxybenzyl) -s-triazine 2,4,6- (1H,
3H, 5H) trione (molecular weight 783.0), triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (molecular weight 586.8), 1,6-hexane For example, diol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (molecular weight 638.9) can be used. Among them, particularly, tetrakis [methylene-3
(3 ′, 5′-Di-tert-butyl-4′-hydroxyphenyl) propionate) methane is preferred.

Other examples of the antioxidant having a molecular weight of 400 or more include tocopherol-based antioxidants such as α-type, β-type
-, Γ-, and δ-type tocopherols. α-Tocopherol is particularly preferred.

These antioxidants are used in an amount of 0.01 to 1.5 parts by weight per 100 parts by weight of the polyester or the polyester composition.

Of course, the polyester composition may contain other resin compounding agents known per se, such as an antiblocking agent such as amorphous silica, a pigment such as titanium dioxide (titanium white), various antistatic agents, and a lubricant. Etc. can be blended according to a known formulation.

In the composite polyester coating used in the present invention, the upper layer (I) generally has a thickness of 0.5 to 20 μm, especially 1 to 20 μm.
Preferably, the lower layer (II) has a thickness of 0.5 to 40 μm, particularly 1 to 35 μm.
μm, and the entire polyester coating layer generally has a thickness of 1 to 60 μm, particularly 2 to 40 μm.
Preferably.

[Production of Laminate] The metal laminate having the above-mentioned composite polyester coating layer can be produced by an extrusion coating method or a heat bonding method of a laminated film.

In the case of the extrusion coating method, using an extruder for the upper layer polyester and an extruder for the lower layer polyester, the two resins are joined in a multilayer multi-die, and the upper and lower polyester layers are co-extruded, and these are melted. It can be manufactured by extrusion coating on a metal substrate and heat bonding.

Referring to FIG. 4 for explaining the method of manufacturing the composite polyester-metal laminate by the extrusion coating method, the metal plate 11 is preheated by the heating rolls 12 a and 12 b as necessary and supplied between the chill roll 13 and the nip roll 14. . On the other hand, polyester is the die head 1 of the extruder.
5 and is extruded into a thin film 16 and supplied between the chill roll 13 and the nip roll 14 so as to overlap the metal plate 11. The chill roll 13 and the nip roll 14 are forcibly cooled, and a thin film 16 made of a composite polyester is pressure-bonded to the metal plate 11 to thermally bond the two and rapidly cool from both sides to obtain a laminate 17.

The heat adhesion of the composite polyester composition to the metal substrate is performed by the heat of the molten polyester layer and the heat of the metal plate. The heating temperature (T ₁ ) of the metal plate is generally from 90 to 290 ° C., preferably from 100 to 280 ° C.

In the case of the production method using a laminated polyester film, a roll of the laminated film is provided in place of the die head shown in FIG.
What is necessary is just to supply between 3 and the nip roll 14.
In this case, it is necessary to heat the metal plate by the heating roll 12 to a temperature equal to or higher than the melting point of the laminated polyester.

The above-mentioned laminated film is obtained by forming the above-mentioned coextrudate into a film by a T-die method or an inflation film forming method. For example, an unstretched film formed by a cast molding method can be used. In general, a biaxially stretched film manufactured by sequentially or simultaneously biaxially stretching this film at a stretching temperature and heat fixing the stretched film can be used.

The degree of biaxial orientation of the polyester film can be confirmed by an X-ray diffraction method, a polarization fluorescence method, a birefringence method, a density gradient tube method, or the like. The degree of biaxial stretching of the film is such that the surface layer polyester is 0.04 to 0.18.
Are suitable. The stretching of the film is generally carried out at a temperature of from 80 to 130 ° C. and an area stretching ratio of 2.
From the range of 5 to 16.0, particularly 4.0 to 14.0, the stretching ratio at which the birefringence falls within the above range is selected in relation to the type of polyester and other conditions. Further, the heat setting of the film is performed at 130 to 240 ° C., particularly 150 to 230 ° C.
, A heat setting temperature that also satisfies the above conditions is selected.

The adhesive primer optionally provided between the composite polyester film and the metal material exhibits excellent adhesiveness to both the metal material and the film. A typical primer paint excellent in adhesion and corrosion resistance is a phenol epoxy paint composed of a resol type phenol aldehyde resin derived from various phenols and formaldehyde, and a bisphenol type epoxy resin, In particular, phenol resin and epoxy resin
0:50 to 1:99 weight ratio, especially 40:60 to 3:
It is a paint containing at a weight ratio of 97.

The adhesive primer layer is generally preferably provided with a thickness of 0.01 to 10 μm. The adhesive primer layer may be provided in advance on a metal material or may be provided in advance on a polyester film.

[Seamless Can and Manufacturing Method Thereof] In the seamless can of the present invention, the side wall portion is stretched by drawing and redrawing of the composite polyester-metal laminate, or is further ironed, so that the original thickness of the laminate is 20 to 95%.
%, Preferably 30 to 85%.

The seamless can of the present invention is obtained by drawing and deep-drawing the above-mentioned composite polyester-metal laminate into a bottomed cup between a punch and a die, and bending and elongating the cup at the deep drawing stage or further ironing. It is manufactured by reducing the thickness of the side wall. That is, the deformation for thinning is performed by a combination of the deformation (bending and elongation) due to the load in the can axis direction (height direction) and the deformation (ironing) due to the load in the can thickness direction, and in this order. Bending and stretching gives the molecular orientation of the ethylene terephthalate units in the c-axis direction, while ironing gives the ethylene terephthalate units a molecular orientation parallel to the film plane of the benzene plane.

The draw-ironing of the laminate is performed by the following means. That is, as shown in FIG. 5, a front drawing cup 30 formed from a coated metal plate is held by an annular holding member 31 inserted into the cup and a redrawing-ironing die 32 located thereunder. . A redrawing-ironing punch 33 is provided coaxially with the holding member 31 and the redrawing-ironing die 32 so as to be able to enter and exit the holding member 31. The redrawing-ironing punch 33 and the redrawing-ironing die 32 are relatively moved so as to bite each other.

The redrawing-ironing die 32 has a flat portion 34 at an upper portion, and has a working corner portion 35 having a small radius of curvature on the periphery of the flat portion, and has a diameter decreasing downward toward a periphery connected to the working corner portion. Tapered approach portion 36
Following the approach portion, a cylindrical ironing land portion (ironing portion) 38 is provided via a curvature portion 37. An inverted tapered relief 39 is provided below the land portion 38.
Is provided.

The side wall portion of the front drawing cup 30 is bent perpendicularly inward from the outer peripheral surface 40 of the annular holding member 31 through the curvature corner portion 41 to re-draw with the annular bottom surface 42 of the annular holding member 31. It passes through a portion defined by the flat portion 34 of the die 32 and is bent substantially vertically in the axial direction by the working corner portion 35 of the redraw die 32, and is formed into a deep drawn cup having a smaller diameter than the front drawn cup 30. At this time, the portion of the working corner 35 opposite to the side in contact with the corner 35 is elongated by bending deformation, while the portion in contact with the working corner 35 is returned after leaving the working corner. It is stretched by deformation, whereby the side wall is thinned by bending and stretching.

The side wall part thinned by bending and stretching is
The outer surface thereof comes into contact with the approach portion 36 having a small taper angle whose diameter is gradually reduced, and the inner surface is guided to the ironing portion 38 in a free state. The process of passing the side wall portion through the approach portion is a stage prior to the subsequent ironing process, and stabilizes the laminate after bending and stretching, and slightly reduces the diameter of the side wall portion to prepare for ironing. In other words, the laminate immediately after bending and stretching is affected by vibrations caused by bending and stretching, distortion remains inside the film, and the film is still in an unstable state. Although it is not possible to perform the ironing process, the outer surface of the side wall portion is brought into contact with the approach portion 36 to reduce the diameter, and the inner surface is free, so that the influence of vibration is prevented and the inside of the film is prevented. In addition, the non-homogeneous distortion of the steel sheet is alleviated, and the heat generated by the bending and elongation is also taken away, thereby enabling smooth and smooth ironing.

The side wall passing through the approach portion 36 is introduced into the gap between the ironing land portion (ironing portion) 38 and the re-drawing and ironing punch 33, and is rolled to a thickness regulated by the gap (C1). You. The thickness C1 of the final side wall portion is determined so as to be 20 to 95%, particularly 30 to 85% of the original thickness (t) of the laminate. In addition, the curvature portion 37 on the ironing portion introduction side smoothly introduces the laminate into the ironing portion 38 while effectively fixing the ironing start point, and has a reverse tapered relief below the land portion 38. Reference numeral 39 is for preventing an excessive increase in the processing force.

The radius of curvature Rd of the curvature corner portion 35 of the redrawing-ironing die 32 should be 2.9 times or less of the thickness (t) of the laminate for effective bending and elongation. If the radius of curvature is too small, the laminate will break, so it should be at least one time the thickness (t) of the laminate.

The approach angle (１ ／ of the taper angle) α of the tapered approach portion 36 should be 1 to 8 °. When the angle of the approach portion is smaller than the above range, relaxation of the orientation of the polyester film layer and stabilization before ironing become insufficient, and when the angle of the approach portion is larger than the above range, the bending and elongation are uneven (return). (Sufficient deformation), and in any case, smooth smooth ironing becomes difficult without cracking or peeling of the film.

The ironing land portion 38, the redrawing-ironing punch 33 and the clearance are in the above-mentioned ranges, but the land length L is generally preferably 0.5 to 3 mm. If the length is larger than the above range, the working force tends to be excessively large. On the other hand, if the length is smaller than the above range, the return after ironing is large, which may be undesirable.

In the seamless can of the present invention, since the polyester layer of the flange portion is subjected to severe tightening, it is preferable that the polyester layer is mildly processed as compared with the polyester layer of the side wall of the can. Thereby, the sealing performance and corrosion resistance of the tightened portion can be improved. For this purpose, a flange forming portion thicker than the thickness of the can side wall is formed at the upper end of the can side wall after ironing.
That is, the thickness of the can side wall is t1 and the thickness of the flange is t.
Assuming that 2, the ratio of t2 / t1 is preferably set in the range of 1.0 to 2.5, particularly 1.0 to 2.0.

In FIGS. 6, 7 and 8 showing the seamless can after redrawing and ironing, the seamless can 50 is
It comprises a bottom part 51 having substantially the same thickness as the base plate thickness and a side wall part 52 thinned by redrawing and ironing.
A thicker flange forming portion 53 is formed on the upper portion of the side wall portion 52.

The flange forming portion 53 has various structures. In the example shown in FIG. 6, the outer surface of the side wall portion 52 and the outer surface of the flange forming portion 53 are on a cylindrical surface having the same diameter. The inner surface of 53 has a smaller diameter than the inner surface of the side wall portion 52. The flange forming portion 53 of this type is formed by reducing the diameter of the portion where the flange forming portion 53 is located by extending the side wall portion in the redrawing-ironing punch 32 as compared with the other portions.

In the example shown in FIG. 7 of the flange forming portion 53, the inner surface of the side wall portion 52 and the inner surface of the flange forming portion 53 are on a cylindrical surface having the same diameter, and the outer surface of the flange forming portion 53 is It has a larger diameter than the outer surface. The flange forming portion 53 of this type is provided with a land portion of the redrawing-ironing die and an ironing portion having a smaller diameter than the land portion in a portion following the land portion.
3 and the side wall 52 are formed.

In the example of the flange forming portion 53 shown in FIG. 8, the outer surface of the flange forming portion 53 has a larger diameter than the outer surface of the side wall portion 52, and the inner surface of the flange forming portion 53 has a larger diameter than the inner surface of the side wall portion 52. It has a small diameter. In this type of flange forming portion 53, the side wall portion is stretched in the redrawing-ironing punch 32 so that the flange forming portion 53 is formed.
By keeping the portion where is located smaller than the other portions, and by re-drawing-the land portion of the ironing die, and further, by providing an ironing portion having a smaller diameter than the land portion in a portion following this land portion, The flange forming portion 53 and the side wall portion 52 are formed.

In producing the seamless can of the present invention, the composite polyester layer on the surface imparts sufficient lubricating performance. However, in order to further enhance the lubricity, a lubricant such as various oils or waxes is used. Apply a small amount,
The processing can be performed with solid surface lubrication. Of course, an aqueous coolant containing a lubricant (of course, also serving as cooling) can be used, but should be avoided in terms of simplicity of operation.

The temperature at the time of redrawing and ironing (the temperature immediately after the completion of ironing) is preferably a temperature not higher than 50 ° C. higher than the glass transition point (Tg) of the polyester and not lower than 10 ° C. For this reason, it is preferable to heat the tool or conversely cool it.

According to the present invention, the drawn container can then be subjected to at least one stage of heat treatment. This heat treatment has various purposes, and mainly includes removing residual strain of a film generated by processing, volatilizing a lubricant used for processing from a surface, and drying and curing a printing ink printed on the surface. Is the purpose. For this heat treatment, a heating device known per se, such as an infrared heater, a hot air circulation furnace, and an induction heating device, can be used. In addition, this heat treatment may be performed in one stage, or may be performed in two or more stages. The heat treatment temperature is 180 to 2
A range of 80 ° C. is appropriate. The heat treatment time is generally on the order of 1 to 10 minutes.

The container after the heat treatment may be cooled rapidly or may be left to cool. That is, in the case of a film or a laminate, the quenching operation is easy, but in the case of a container, the quenching operation in an industrial sense is difficult because it is three-dimensional and has a large heat capacity due to metal. In the present invention, even without a quenching operation, crystal growth is suppressed, and excellent combination characteristics can be obtained. Of course, if desired, it is optional to employ a rapid cooling means such as blowing cold air or spraying cooling water.

The obtained can is subjected to one-stage or multi-stage neck-in processing, if necessary, and flanged to obtain a can for winding. Prior to neck-in processing, bead processing or circumferential polyhedral wall processing described in Japanese Patent Publication No. 7-5128 can be performed.

[0098]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples.

Preparation of Laminated Body For Examples 1 and 3 and Comparative Examples 1 to 4 shown in Table 1, a TFS steel sheet (sheet thickness 0.195 mm, temper degree T-4,
Metal chromium amount 110 mg / m ² , chromium hydrated oxide amount 1
5 mg / m ² ), a film obtained by biaxially stretching a polyester resin having the composition shown in Table 1 at 3.0 times and 3.0 times horizontally on one surface and a pigment having the same resin composition on the other surface. A 13 μm-thick film obtained by biaxially stretching a white copolymer polyester resin containing 20% by weight of titanium oxide was heat-laminated and immediately cooled with water to obtain a laminated metal plate. At this time, the sheet temperature before lamination was set to be about 15 ° C. higher than the melting point of the polyester resin. The laminating roll temperature is 150 ° C., and the passing speed is 40 m / mi.
n. Was used for lamination. For Examples 2 and 4 shown in Table 1, the apparatus shown in FIG. 4 was used, and the resin shown in Table 1 was blended by dry blending and supplied to an extruder having a diameter of 65 mm. A TFS steel sheet (sheet thickness 0.195 mm, heated to a melting flow start temperature of each resin + 20 ° C. so that the film thickness is as shown in Table 1
Temper T-4, amount of chromium metal 110 mg / m ² , hydrated chromium oxide 15 mg / m ² ) 20m / min using warm laminating roll
The lamination was performed at the following speed. Thereafter, a laminate was obtained through a quenching step using a water shower and a slight trimming step on both sides of the coil.

IV (Intrinsic Viscosity) Measurement A can body was cut out, and a metal plate was dissolved with 6N hydrochloric acid to isolate a film. Thereafter, the sample was subjected to vacuum drying for at least 24 hours to obtain a sample for IV measurement. A 200 mg portion of this sample was dissolved in a phenol / 1,1,2,2-tetrachloroethane mixed solution (weight ratio 1: 1) at 110 ° C., and the specific viscosity was measured at 30 ° C. using an Ubbelohde viscometer. The intrinsic viscosity was determined by the following equation. [Η] = [(-1+ (1 + 4K′η _sp ) ^1/2 ) / 2K ′
C] (dl / g) K ′: Haggins constant (= 0.33) C: concentration (g / 100 ml) η _sp : specific viscosity [= (fall time of solution−fall time of solvent)
/ Fall time of solvent]

Dent Test After the can filled with cola was allowed to stand laterally, at 5 ° C., the diameter of the diameter of the can at the end of the neck processed portion of the can at the bottom of the can was determined on the can axis perpendicular to the rolling direction of the metal plate. A 1 kg weight having a spherical surface of 65.5 mm was dropped from a height of 60 mm so that the spherical surface hit the can, and an impact was applied. Then 37
A storage test was carried out at a temperature of ° C, and the condition of the inner surface of the can after one year was observed.

Retort treatment test After filling distilled water at 95 ° C., retort treatment was performed at 135 ° C. for 30 minutes, the temperature was returned to room temperature, distilled water was removed, and the turbidity was measured. Further, the corrosion state of the inner surface of the can was observed. The turbidity measurement was performed using a simple high-sensitivity turbidity / chromaticity meter manufactured by Yasui Kikai Co., Ltd., and 100 ml of the sample was placed in a turbidity colorimetric tube and placed in the cell for the sample. Was placed in a control cell, the bottom was seen through from the top, and the brightness at the bottom was compared to measure the turbidity.

Measurement of Tg A cast film for each of the surface layer and the lower layer was prepared and used as a DSC measurement sample. The measurement was made by PerkinElmer DS
C7 type was used. Tg is measured at -20 ° C to 28 ° C.
The sample heated to 0 ° C. was rapidly cooled to −20 ° C., left for 5 minutes, and then heated at a rate of 20 ° C./min to 280 ° C., and determined according to JIS K-7121 from the obtained chart.

Example 1 A wax-based lubricant was applied to a laminate using a resin having the composition shown in Table 1, and a disk having a diameter of 166 mm was punched to obtain a shallow drawn cup. Then re-draw the shallow drawn cup
Ironing was performed to obtain a deep-drawn ironing cup. The characteristics of this deep drawing cup were as follows. Cup diameter: 66 mm Cup height: 128 mm Thickness of can wall 65% of base plate thickness Flange thickness 77% of base plate thickness This deep drawn ironing cup is subjected to doming molding according to a conventional method, and heat-treated at 220 ° C. After the cooling, the cup is allowed to cool, and the opening edge is trimmed, curved surface printed and baked, dried, necked, and flanged to perform 350.
A seamless can for g was obtained. There was no problem on molding.
Then, it was subjected to a dent test by filling with cola and a retort treatment test by filling with distilled water. The analysis values and evaluation results of the film used for this can are summarized in Table 2, but no corrosion was observed in the dent portion in the dent test and no corrosion was observed in the retort test, and the results were good. Moreover, the turbidity after retort was also a low value and was favorable. From these results,
The seamless can obtained here was evaluated as being excellent for storing beverages.

Example 2 As summarized in Table 1, molding was performed in the same manner as in Example 1 except that the resin composition was different. There was no problem on molding. Evaluation and film analysis were performed in the same manner as in Example 1. In all the evaluations, good results were obtained, and the obtained seamless can was evaluated as being excellent for storing beverages.

Example 3 As summarized in Table 1, molding was performed in the same manner as in Example 1 except that the resin composition was different. There was no problem on molding. Evaluation and film analysis were performed in the same manner as in Example 1. In all the evaluations, good results were obtained, and the obtained seamless can was evaluated as being excellent for storing beverages.

Example 4 As summarized in Table 1, molding was performed in the same manner as in Example 1 except that the resin composition was different. There was no problem on molding. Evaluation and film analysis were performed in the same manner as in Example 1. In all the evaluations, good results were obtained, and the obtained seamless can was evaluated as being excellent for storing beverages.

Example 5 As summarized in Table 1, molding was performed in the same manner as in Example 1 except that the resin composition was different. There was no problem on molding. Evaluation and film analysis were performed in the same manner as in Example 1. In all the evaluations, good results were obtained, and the obtained seamless can was evaluated as being excellent for storing beverages.

Comparative Example 1 A laminate having the resin composition shown in Table 1 was prepared and molded in the same manner as in Example 1. As a result, whitening was observed in the upper part of the can. When this can was subjected to a dent test in the same manner as in Example 1, corrosion under the film was observed at the dent portion. Further, when subjected to a retort test, the occurrence of corrosion was severe at the neck portion. The turbidity was not measured because brown turbidity of the contents due to the corrosion was observed. These were believed to be due to excessive crystallization of the film as indicated by the enthalpy of fusion of the film. From these results, the cans obtained here were evaluated as unsuitable for storing beverages.

Comparative Example 2 As summarized in Table 1, molding was performed in the same manner as in Example 1 except that the resin composition was different. There was no problem on molding. In addition, when the evaluation and the film analysis were performed in the same manner as in Example 1, no corrosion was recognized, but the measured value of the turbidity was
It was larger than in Examples 1 to 5. From these results, although the can obtained here did not have a big problem in preserving beverages, it was inferior in turbidity as compared with Examples 1 to 5.

Comparative Example 3 A laminate having the resin composition shown in Table 1 was prepared and molded in the same manner as in Example 1. As a result, whitening was observed in the upper part of the can. When this can was subjected to a dent test in the same manner as in Example 1, corrosion under the film was observed at the dent portion. Further, when subjected to a retort test, the occurrence of corrosion was severe at the neck portion. The turbidity was not measured because brown turbidity of the contents due to the corrosion was observed. From these results, the cans obtained here were evaluated as unsuitable for storing beverages.

Comparative Example 4 A laminate having the resin composition shown in Table 1 was prepared and molded in the same manner as in Example 1. As a result, cracks in the film were observed in the upper part of the can, and the film was used only for evaluation. No cans were obtained.

[0113]

[Table 1]

[0114]

[Table 2]

[0115]

According to the present invention, in a laminate comprising a metal substrate and a matured polyester layer provided on the surface of the substrate, (I)
A surface layer composed of a copolymerized polyester or a blended polyester containing the naphthalenedicarboxylic acid component in an amount of 1.0 to 95 mol% based on the total basic carboxylic acid component, and (II) a glass containing the terephthalic acid component and A combination comprising a polyester having a transition point (Tg) of 65 ° C. or lower and a lower layer made of a polyester composition, wherein the difference between the glass transition point of the surface layer and the glass transition point of the lower layer is larger than 10 ° C. As a result, during high-temperature treatment and long-term storage, migration of low-molecular-weight components inevitably present in the polyester film into the contents is suppressed as much as possible, and the occurrence of turbidity is suppressed, and the impact resistance (particularly, dent resistance) ), A metal-polyester laminate excellent in combination of workability and content resistance, and a seamless container. Kill.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a seamless can according to the present invention.

FIG. 2 is an enlarged sectional view showing an example of a sectional structure of a laminate used in the present invention.

FIG. 3 is an enlarged cross-sectional view showing another example of the cross-sectional structure of the laminate used in the present invention.

FIG. 4 is an explanatory view showing a lamination step.

FIG. 5 is an explanatory view showing a bending / stretching / ironing step.

FIG. 6 is a sectional view showing an example of a flange portion of the seamless can of the present invention.

FIG. 7 is a sectional view showing another example of the flange portion of the seamless can of the present invention.

FIG. 8 is a sectional view showing another example of the flange portion of the seamless can of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deep drawing can 2 Bottom part 3 Side wall part 4 Neck part 5 Flange part 6 Metal substrate 7 Inner coating (laminated film) 7a Surface layer 7b Lower layer 8 Outer coating 9 Adhesive primer layer 11 Metal plate 12a Heating roll 12b Heating roll 13 Chill roll 14 Nip roll 15 Die head 16 Thin film 17 Laminated body 30 Pre-draw cup 31 Ring-shaped holding member 32 Redraw-ironing die 33 Redraw-ironing punch 34 Flat part 35 Working corner part 36 Approach part 37 Curvature part 38 Land part 39 Escape 40 Outer peripheral surface 41 Curvature corner part 42 Annular bottom surface 51 Bottom part 52 Side wall part 53 Flange forming part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Katsuhiro Imazu, Inventor 6205-1, Izumicho, Izumi-ku, Yokohama-shi, Kanagawa Prefecture Greenheim 27-101 Izumino 27-101

Claims (5)

[Claims] 1. A can-forming laminate comprising a metal substrate and a thermoplastic polyester layer provided on the surface of the substrate,
When the thermoplastic polyester layer contains (I) an amount of naphthalenedicarboxylic acid component per total basic carboxylic acid component of l. A surface layer composed of a copolymerized polyester or a blended polyester containing 0 to 95 mol%, and (II) a polyester or polyester composition containing a terephthalic acid component and having a glass transition point (Tg) of 65 ° C. or less. A laminated body for cans comprising a laminated film comprising a lower layer and a difference between the glass transition point of the surface layer and the glass transition point of the lower layer is greater than 10 ° C. 2. The polyester or polyester composition of the lower layer (II) is an acid component containing an alcohol component mainly composed of alethylene glycol and butylene glycol, and at least one component among terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid. The laminate for cans according to claim 1, wherein the laminate is derived from: 3. The laminate for cans according to claim 1, wherein the polyester or the polyester composition of the lower layer (II) is derived from an acid component containing an aliphatic dibasic acid. 4. The laminated body for a can according to claim 1, wherein the thermoplastic polyester layer has a molecular weight corresponding to an intrinsic viscosity of 0.5 or more as a whole. 5. A seamless can formed by drawing or laminating / ironing the laminate according to claim 1.