JPH10100315A - Laminate and container using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve impact resistance, especially, dent resistance by forming a polyester film of a laminate from a blend containing crystalline polyester and copolymer polyester being a specific component which are blended at a specified ratio, and setting the ester exchange ratios and intrinsic viscosities of the components of the blend to specific values. SOLUTION: A polyester film layer constituting a laminate is formed of a laminated film composed of a substrate layer constituted of a blend containing crystalline polyester (i) based on an ethylene terephthalate unit and copolymer polyester (ii) containing an ester unit derived from butylene glycol and aromatic dibasic acid and an ester unit derived from butylene glycol and aliphatic dibasic acid in a mol ratio of 90:10-50:50 in a wt. ratio of (i):(ii)=90:10-30:70. The ester exchange ratio E shown by formula of the component (i) in the blend is set to 0.5-20% and the intrinsic viscosity of the blend is set to 0.55 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate comprising a metal substrate and a polyester film laminated thereon and a seamless container formed by drawing or further ironing the laminate. More specifically,
The present invention relates to a laminate having significantly improved impact resistance (dent resistance) and a seamless container formed from the laminate.

[0002]

2. Description of the Related Art Conventionally, as a side seamless can (side seamless can), a metal material such as an aluminum plate, a tin plate or a tin-free steel plate is provided by at least one step between a drawing die and a punch. By drawing, a cup consisting of a body part having no side seam and a bottom part connected to the body part without a seam is formed, and then, if desired, an ironing punch and a die are formed on the body part. It is known that the body of the container is thinned by ironing between them.
In addition, instead of ironing, it is already known that the side wall portion is thinned by bending and stretching at a curvature corner portion of a redrawing die (Japanese Patent Publication No. 56-501442).

As an organic coating method of a side seamless can, there is a method of applying an organic paint to a molded can which is widely used in general, and a method of laminating a resin film on a metal material before molding in advance. Known, Tokubiko Sho 59-3
No. 4580 describes the use of a metal material laminated with a polyester film derived from terephthalic acid and tetramethylene glycol. Also, when producing redrawn cans by bending and stretching,
It is also known to use a coated metal plate of vinyl organosol, epoxy, phenolics, polyester, acrylic or the like.

There have been many proposals for the production of polyester-coated metal sheets, for example, see Japanese Patent Application Laid-Open No. Sho 51-4229.
In JP-A-6-172556, a coating film composed of polyethylene terephthalate having a biaxial orientation remaining on the surface is described.
It has been proposed to use five or more polyester films for metal lamination.

JP-A-3-101930 discloses a lamination of a metal plate, a polyester film layer mainly composed of ethylene terephthalate units and, if necessary, an adhesive primer layer interposed between the metal plate and the polyester film. Wherein the polyester film layer has the formula Rx = IA / IB, where IA is parallel to the polyester film surface and has a plane spacing of about 0.34 nm (CuKα X-ray diffraction angle is from 24 ° to 2 °).
8 ゜) X-ray diffraction intensity by the diffraction plane, IB is about 0.39 nm (Cu
The X-ray diffraction intensity defined by the diffraction plane having a Kα X-ray diffraction angle of 21.5 ° to 24 °) is in the range of 0.1 to 15, and the anisotropy of the in-plane orientation of the crystal. A coated metal sheet for drawn cans characterized by comprising a film layer having a property index of 30 or less is described. Also, the coated metal sheet is drawn and redrawn, and a can body side wall is formed at the time of redrawing. A thinned drawn can having a thinned portion by bending and stretching is described.

[0006]

The proposal recognized in the above prior art is to apply a resin film to a metal material before molding, and to apply a coating film baking furnace or a paint exhaust gas treatment facility as in a normal coating process. Is required, there is no air pollution, and there is no need to apply coating treatment to the molded body. However, various characteristics of the can, especially impact resistance (dent resistance), corrosion resistance There is room for improvement in terms of properties and tightness or tightness.

[0007] The proposal of Japanese Patent Application Laid-Open No. Hei 3-101930 proposes that a polyester film layer of a coated metal material for drawing and redrawing is provided with a certain balanced oriented crystal so as to obtain excellent workability and resistance to drawing. Although it imparts corrosiveness (pinhole resistance), it has not yet been sufficiently satisfactory in terms of impact resistance and corrosion resistance to highly corrosive contents.

As practical impact resistance required for actual canned products, there is 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. .

Next, in the case of cans, the influence 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, and the effect of heating for printing the printing ink occurs on the polyester film. Polyester tends to crystallize (become brittle) due to heating, thereby lowering dent resistance, lowering adhesion to a metal substrate or lowering coatability, neck-in processing, winding processing, and the like. Workability decreases.

[0010] In view of the above facts, various characteristics of a metal can coated with a polyester film or the like, particularly impact resistance (dent resistance), corrosion resistance, and tightness or sealing property, are required for the metal plate. It will be appreciated that it depends not on the physical properties of the polyester film before or after application but on the physical properties of the film as it is actually formed into a can.

Further, in a seamless can formed from a coated metal plate, it is also extremely important to highly thin the side wall of the can body from the viewpoint of saving material costs and reducing container weight. In redrawing, the side wall is bent and elongated (bending-bending deformation) at the die corner portion having a small R, or is thinned by ironing. The method of reducing the thickness of the side wall of the seamless can and reducing the thickness is one. In this way, the can height has been increased, and material cost and container weight have been successfully reduced to some extent. In other words, the degree of orientation crystallization (uniaxial orientation crystallization) of the polyester layer is also increased, and embrittlement due to processing and reduction in impact resistance cannot be ignored.

Accordingly, an object of the present invention is to provide a metal-polyester laminate having significantly improved impact resistance, particularly dent resistance, and a seamless container formed from the laminate.

Another object of the present invention is to suppress brittleness due to crystallization and maintain excellent dent resistance despite advanced drawing or ironing or heat treatment during or after can making. To provide a metal-polyester laminate and a seamless container comprising the same.

[0014]

According to the present invention, there is provided a laminate comprising a metal substrate and a biaxially stretched polyester film layer thermally bonded to the metal substrate, wherein the polyester film mainly comprises (i) an ethylene terephthalate unit. And (ii) an ester unit derived from (a) butylene glycol and an aromatic dibasic acid, and (b) an ester unit derived from butylene glycol and an aliphatic dibasic acid. Component (i) formed from a blend containing a copolymerized polyester containing a molar ratio of 10 to 50:50 in a weight ratio of (i) :( ii) = 90: 10 to 30:70. The ester exchange rate (E) shown in the following formula (1) is in the range of 0.5 to 20%,
And a laminate characterized in that the intrinsic viscosity (IV) of the blend is 0.55 or more: E = 100 · [1-exp {(Hu / R) · (1 / Tm0−1 / Tm)}] (1) where: Hu: heat of fusion of crystalline polyester mainly composed of ethylene terephthalate units: 9200 (J / mol) R: gas constant: 8.314 (J / (mol · K)) Tm: melting point of blend (K) Tm0: melting point (K) of the crystalline polyester (i) mainly composed of ethylene terephthalate units.

According to the present invention, there is also provided a laminate comprising a metal substrate and a biaxially stretched polyester film layer thermally bonded thereto, wherein the polyester film layer comprises:
(A) a surface layer of a crystalline polyester mainly composed of ethylene terephthalate units; (B) (i) a crystalline polyester mainly composed of ethylene terephthalate units; and (ii)
(a) an ester unit derived from butylene glycol and an aromatic dibasic acid and (b) an ester unit derived from butylene glycol and an aliphatic dibasic acid in a molar ratio of 90:10 to 50:50. (I): (ii) = 90:10 to 30:70 by weight, comprising a laminated film with a base layer comprising a blend and the following components (i) in the blend: A laminate characterized in that the transesterification ratio (E) shown in the formula (1) is in the range of 0.5 to 20% and the intrinsic viscosity (IV) of the blend is 0.55 or more: E = 100 · [1-exp {(Hu / R) · (1 / Tm0−1 / Tm)}] (1) where, Hu: heat of fusion of crystalline polyester mainly composed of ethylene terephthalate unit 9200 (J / mol) R: gas constant .314 (J / (mol · K)) Tm: melting point of the blend (K) Tm0: melting point of the crystalline polyester composed mainly of ethylene terephthalate units (i) (K), is provided.

In the present invention: 1. The polyester (i) is polyethylene terephthalate or polyethylene terephthalate / isophthalate containing an ethylene isophthalate unit in an amount of 20 mol% or less; 2. the copolymerized polyester (ii) is polybutylene terephthalate / adipate; Assuming that the birefringence of the polyester film layer of the laminate represented by the following formula (2) is Δn1 on the surface side of the film, Δn2 at an intermediate position of the film from the surface to the metal plate, and Δn3 on the side in contact with the metal plate, At least one of Δn1 and Δn2 is 0.02 or more, and Δn3 is Δn
It is preferably 1 or less than Δn 2, where Δn 1-3 = nm−nt (2) nm is the refractive index in the maximum orientation direction of the film, and nt is the refractive index in the thickness direction of the film.

According to the present invention, there is further provided a seamless container obtained by drawing or laminating the above-mentioned laminate.

In the present invention, as the polyester coating layer of the laminate, a specific copolymerized polyester, a crystalline polyester mainly composed of ethylene terephthalate units,
That is, (a) an ester unit derived from butylene glycol and an aromatic dibasic acid and (b) an ester unit derived from butylene glycol and an aliphatic dibasic acid are 90: 1.
The first feature is to use a blend of copolyesters containing a molar ratio of 0 to 50:50.

As noted above, for canned products,
It is frequent to receive an impact due to dropping or the like, and exhibiting excellent corrosion resistance even after this impact is a very important requirement for preventing metal elution, leakage due to pitting corrosion, and the like. However, crystalline polyesters mainly composed of ethylene terephthalate units are excellent in mechanical properties, heat resistance, barrier properties against corrosive components, etc., but after impact, the corrosion resistance tends to be significantly reduced ( See Comparative Example 1). On the other hand, when the above copolymerized polyester is blended with the ethylene terephthalate-based polyester, the corrosion resistance after impact can be significantly improved without impairing the above-mentioned properties of polyethylene terephthalate.

Please refer to FIG. 1 of the accompanying drawings. FIG.
After performing heat treatment (heat treatment at 220 ° C. for 3 minutes and then heat treatment at 205 ° C. for 2 minutes) on a laminate obtained by laminating various polyesters on a metal plate, the environmental temperature at which a dent (dent) test is performed is changed. 4 is a graph plotting the relationship between the enameler value ERV (evaluating the degree of metal exposure as a current value). In addition, this dent test was performed by the following method. Dent test: The film surface of the laminate is brought into contact with the wet silicone rubber, and a 1-inch diameter steel ball is placed on the back side of the laminate, and a 1 kg weight is dropped from a height of 40 mm on the steel ball. Was. Next, the crack of the film of the laminated body was evaluated by a current value (ERV: mA) flowing at 6.3 V. According to the test results, in the case of the PET / I type ethylene terephthalate polyester (88 mol% of terephthalic acid, 12 mol% of isophthalic acid), the current value due to the metal exposure after the dent test was significantly large. , PET / I // PBT (30% by weight of PBT blended with ethylene terephthalate-based polyester consisting of 94 mol% of terephthalic acid and 6 mol% of isophthalic acid)
It is understood that the current value due to the metal exposure after the dent test is about one digit lower. The PET / I // PBT / A system in which 30% by weight of PBT / A (80% by mole of terephthalic acid, 20% by mole of adipic acid, 100% by mole of 1,4-butanediol) is blended in place of the above-mentioned PBT is a dent. The surprising fact that the current value due to the metal exposure after the test can be suppressed to a value lower by one digit or more becomes clear.

The copolymerized polyester used as a blend component in the present invention, that is, (a) an ester unit derived from butylene glycol and an aromatic dibasic acid and (b) a copolymer derived from butylene glycol and an aliphatic dibasic acid. Is relatively low in crystallinity as compared with polybutylene terephthalate, but the molecular orientation of the whole blend and / or the crystallinity due to heating are high. This has the effect of suppressing the formation of the oxidizing agent.

FIG. 2 shows that a laminate obtained by laminating various polyesters is molded into a seamless can and then subjected to a heat treatment (220 ° C.).
After heat treatment at 205 ° C. for 2 minutes after heat treatment for 3 minutes), after retort sterilization, a polyester film was isolated by the method described below for the can bottom, lower can body, and upper can body, and the degree of crystallization of the polyester was determined as follows. In the differential thermal analysis described below, the results obtained by evaluating the calorific value of crystal melting when the isolated film is measured as it is from normal temperature at a heating rate of 20 ° C./min are shown. According to the results, the PET / I polyester has a large degree of crystallization, and furthermore, the bottom of the can, the lower part of the can body,
And the degree of crystallization increases in the order of the upper part of the can body.
In the PET / I // PBT system in which PBT is blended with 30% by weight of PET / I, the crystallization of the polyester layer is increased, but PET / I // PBT / in which PBT / A is blended instead of PBT. In the A system, the crystallinity of the polyester layer can be suppressed lower. This is thought to be due to the effect of significantly lowering the crystallization rate of PBT by copolymerizing adipic acid with PBT.

FIG. 3 shows a laminate obtained by laminating a polyester film in a PET / I // PBT system in which the transesterification rate of the blend is variously adjusted by the method described below, and heat-treated in the same manner as in FIG. It is a graph which shows the relationship between the enameler value ERV after a dent test, and the calorific value of the crystal fusion in a differential thermal analysis. The heat of crystal fusion was determined by isolating a polyester film from the sample subjected to the dent test by the method described below and by the method described in FIG. The enamellator value simply increases with an increase in the heat of crystal fusion. Thus, it is understood that reducing the crystallinity of the polyester layer is important for improving the dent resistance of the can, particularly for improving the dent resistance of the neck-in processed portion and the flange processed portion of the upper portion of the can body. .

The excellent dent resistance of the blend of the present invention can be understood by referring to the viscoelastic behavior of the blend. FIG. 4 shows the above-mentioned PET / I, P
ET / I // PBT blend system and PET / I // P
It is the graph which plotted the relationship between temperature and loss elastic modulus about what was laminated and heat-processed about the BT / A blend system. In this graph, the peak appearing on the right side indicates the α dispersion which is a measure of the glass transition point (Tg),
The peaks appearing on the left indicate β dispersion, which is a measure of impact resistance. From these results, both the PET / I // PBT blend system and the PET / I // PBT / A blend system show large dispersion on the low temperature side, which indicates that the low temperature brittleness is improved. But PET / I // PBT
The / A blend system shows α-dispersion even at a temperature lower by about 30 ° C. than the PET / I // PBT blend system, which seems to contribute to the improvement of dent resistance and workability. It is.

In the present invention, the component (i) in the above-mentioned blend, that is, the transesterification rate of the ethylene terephthalate-based crystalline polyester represented by the above formula (1) is 0.5 to 2
The second feature is that it is within the range of 0%.

The above formula (1) for determining the transesterification rate is as follows:
It is based on the generally known Flory equation, and there is a certain relationship between the degree of transesterification in the blend and the melting point drop of the crystalline polyester (i) mainly composed of ethylene terephthalate. Is required based on That is, when no drop in the melting point of the polyester (i) occurs, 1 / Tm0 on the left side of the formula (1) is obtained.
The value of −1 / Tm is 0, and the transesterification rate E is zero%.
Becomes When the degree of melting point drop increases, 1 / Tm0 −
The value of 1 / Tm is negative and its absolute value becomes large, and the transesterification ratio E becomes a large value.

In the present invention, the transesterification rate is 0.5
It is important for the corrosion resistance after impact to be in the range of -20%. That is, when the transesterification rate is less than 0.5%, the blend of both components (i) and (ii) is insufficient, and a film having satisfactory physical properties cannot be obtained. On the other hand, when the transesterification rate exceeds 20%, the corrosion resistance after impact is significantly reduced (see Comparative Example 4). The reason is considered as follows. The molded cans are printed and baked with printing ink. At this time, the effect of the sea-island structure by the blending is reduced in the coating layer of the blend having a transesterification rate of more than 20%. It seems to be. That is, in the present invention, the polyester component (i) mainly composed of polyethylene terephthalate contributes to improvement in heat resistance, and the copolymerized polyester component (ii) having an ester unit derived from butylene glycol reduces the glass transition temperature of the blend. These improve the impact resistance after the heat treatment. However,
When the transesterification ratio exceeds 20%, the effect of improving the heat resistance by the component (i) is impaired, and the effect of lowering the glass transition temperature by the component (ii) is impaired. As a result, the impact resistance is impaired. It is done. Therefore,
In the coating layer of the blend in which the transesterification rate is in the range of 0.5 to 20%, the molecular orientation is maintained, and even if the oriented crystallization proceeds, the thermal crystallization is suppressed, and the film is cracked upon impact. Is prevented, and excellent corrosion resistance is maintained.

In the present invention, the weight ratio between the ethylene terephthalate-based polyester (i) and the specific copolymerized polyester (ii) in the blend is as follows:
It is also important that (i) :( ii) = 90: 10 to 30:70. In both cases where the blend ratio of both is below and above the above range, the moldability into a seamless container, the neck-in processability and the flange processability of the can after molding are reduced, and the corrosion resistance after impact is also reduced. (See Comparative Example 6).

In the laminate and the seamless container of the present invention, the layer of the blend should be provided on the inner surface of the can where corrosion resistance is a problem, and may be provided as a single layer or as a multilayer. . In the latter case, it is desirable to provide the blended material layer as a lower layer and to provide an ethylene terephthalate-based polyester as an upper layer from the comprehensive viewpoint of workability, corrosion resistance, impact resistance, flavor and the like.

(Ethylene Terephthalate-Based Crystalline Polyester) The ethylene terephthalate-based crystalline polyester used in the present invention has a glass transition point (Tg) in which most of the ester repeating units account for at least 80 mol% of ethylene terephthalate units. Is 50 to 90 ° C, especially 7
0 to 90 ° C, melting point (Tm) 210 to 260 ° C,
Particularly, a crystalline polyester having a temperature of 220 to 260 ° C. is preferable. 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, and 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 as a copolymer component is excellent in content resistance, content flavor retention, and the like.

The diol component is preferably composed of only ethylene glycol, but other diol components such as propylene glycol, 1,4-butanediol, diethylene glycol, and the like may be used within a range not to impair 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-based crystalline polyester used satisfies the intrinsic viscosity described later as a blend, but the upper limit of the intrinsic viscosity is preferably 1.5 or less. The measurement of the intrinsic viscosity is performed by a method described later.

(Copolymerized polyester) The copolymerized polyester used in the present invention comprises (a) an ester unit derived from butylene glycol and an aromatic dibasic acid, and (b) a copolymer derived from butylene glycol and an aliphatic dibasic acid. The copolymerized polyester contains the obtained ester unit in a molar ratio of 90:10 to 50:50.

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

The aliphatic dibasic acid component constituting the ester unit (b) includes succinic acid, azelaic acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecandioic acid, tetradecandioic acid, dimer acid and the like. Although long-chain aliphatic dibasic acids are preferred because they have a large effect of lowering Tg, adipic acid is particularly preferred from the viewpoint of industrial production.

The diol component is preferably composed only of 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, diethylene glycol and 1,6-hexyl. It may contain one or more of xylene glycol, cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A, and the like.

This copolymerized polyester has an aromatic ester unit (a) and an aliphatic ester unit (b) in a ratio of 90: 1.
It is also important to include a molar ratio of 0 to 50:50, and when the content of the aliphatic ester unit is less than the above range, the improvement of impact resistance (dent resistance) is insufficient,
On the other hand, if it exceeds the above range, the heat resistance, workability, barrier properties against corrosive components and the like of the coating will be reduced.

The glass transition point (T
g) is -20 to 40 ° C, especially -10 to 20 ° C, and the melting point (Tm) is 180 to 220 ° C, particularly 190 to 22 ° C.
Copolyesters at 0 ° C. are preferred.

The copolyester used should have at least a molecular weight sufficient to form a film;
In the form of a blend, it gives the intrinsic viscosity described below. The upper limit of the intrinsic viscosity is preferably 1.5 or less.

(Polyester blend) In the present invention,
Polyester blend containing ethylene terephthalate-based polyester (i) and specific copolymerized polyester (ii) in a weight ratio of (i) :( ii) = 90: 10 to 30:70, especially 90:10 to 40:60 Use

In a blend of a crystalline polyester resin mainly composed of ethylene terephthalate and a specific copolymerized polyester resin, a method for controlling the ester exchange rate in the above-mentioned range is as follows.
A method of blending resin chips in advance and kneading while controlling the resin temperature, reaction time, humidity, etc. to control the transesterification rate, or directly putting the raw material chips into the extruder, and setting the resin temperature and residence time in the extruder The temperature and time during kneading are very important parameters in the transesterification reaction. The temperature at the time of kneading the polyester resin is generally 260 ° C. to 280 ° C., but when the temperature is high, the transesterification reaction easily proceeds, but conversely, thermal decomposition starts, and as a result, the molecular weight decreases. Also, the longer the kneading time, the higher the transesterification rate.

The mixing or kneading operation is performed by performing dry mixing using a blender, a Henschel mixer, or the like, and then performing melt kneading using various kneaders or a single- or twin-screw extrusion-type melt-kneading apparatus or a kneading apparatus for an injection machine. Done.

(Polyester Film) The polyester film used in the present invention may be a film of the above-mentioned blend alone or a multilayer film containing this blend layer. In the case of a multilayer film, the lower layer (the metal plate side) is preferably made of a blend, and the upper layer is preferably made of the aforementioned ethylene terephthalate-based crystalline polyester.

The total thickness of the polyester film used in the present invention is 2 to 100 μm, especially 5 to 5 μm.
The range of 0 μm is good in terms of metal protection effect and workability. In the case of a multilayer film, the blend layer and the ethylene terephthalate-based polyester layer preferably have a thickness ratio of 96: 4 to 4:96.

The polyester film should be biaxially oriented. The degree of biaxial orientation can also be confirmed by X-ray diffraction, polarized fluorescence, birefringence, density gradient tube method, and the like. The degree of biaxial stretching of the film is suitably such that the refractive index difference Δn represented by the following formula, that is, the birefringence Δn is in the range of 0.04 to 0.18. Δn = n1−n2 where n1 is the refractive index in the maximum orientation direction of the film, and n2 is the refractive index in the thickness direction of the film.

Of course, the polyester film may contain known film compounding agents such as anti-blocking agents such as amorphous silica, pigments such as titanium dioxide (titanium white), various antistatic agents, lubricants and the like. Can be formulated according to the formula

Although not generally required, when an adhesive primer is used, it is generally desirable to subject the surface of the biaxially stretched polyester film to a corona discharge treatment in order to increase the adhesion to the adhesive primer to the film. .
The degree of the corona discharge treatment is such that the wetting tension is 44 dyne.
/ Cm or more.

In addition, the film may be subjected to a known surface treatment for improving adhesion such as plasma treatment or flame treatment or a coating treatment for improving adhesion of urethane resin or modified polyester resin. .

(Metal Plate) In the present invention, various metal sheets such as surface-treated steel sheets and 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 kinds of 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 200 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.

[Laminate and Method for Producing the Same] In FIG. 5, which shows an example of the cross-sectional structure of the laminate of the present invention, the laminate 1 comprises a metal substrate 2 and a polyester blend layer 3 located at least on the inner surface side. ing. An outer coating 4 is formed on the metal substrate 2.
May be the same as the polyester blend layer 3, or may be a normal can coating or resin (polyester) film coating.

In FIG. 6 showing another example of the cross-sectional structure of the laminate, the same as FIG. 5 except that an adhesive primer layer 5 is provided between the polyester blend layer 3 and the metal substrate 2. It is.

The polyester-metal laminate used in the present invention can be produced by thermally bonding a biaxially stretched polyester film to a metal. At this time, it is preferable that the biaxial orientation partially remains in the polyester layer in order to maintain the dent resistance. Table 1 below shows the relationship between the birefringence of the polyester film layer in the laminate made of the polyester-metal laminate (assuming the bottom of the can) and the enamel value ERV after the dent test.
That is, a film having the same composition as the biaxially stretched laminated film used in Example 2 described later but having different transesterification rates and IVs is used, and when laminating the films, the plate temperature is in the range of 235 ° C to 250 ° C. Was adjusted to adjust the birefringence of the film in the obtained laminate. The birefringence of the polyester film layer in this laminate, the birefringence of the film layer when the laminate was subjected to a certain heat treatment, and the same as described above in a 5 ° C. environment for the laminate after the heat treatment. Table 1 shows the enamel value ERV obtained by the dent test. The IV of the lower polyester layer in the film of the laminate before the heat treatment was 0.64, and the transesterification rate was 5.0%. The measurement of these IV, transesterification rate and birefringence was performed by the method described in Examples described later.

[0058]

[Table 1]

According to Table 1, at the heat treatment temperature of 220 ° C., the birefringence (Δn 1) on the film surface side or the intermediate position of the film from the film surface to the metal plate (about 1 ° C.).
/ 2 thickness), the higher the birefringence (Δn2), the higher the dent ER
It is understood that V shows a tendency to decrease (Table 1).
Where Δn3 is the birefringence of the TFS steel plate side portion). Also, even if Δn1 or Δn2 of the laminate is high, if the heat treatment temperature becomes high (240 ° C.), the birefringence of the laminate after heat treatment decreases (in the case of a can, the birefringence at the bottom of the can decreases), and the dent ERV It is understood that is increasing. in this way,
The polyester film layer laminated on the metal plate preferably has a part of the biaxial orientation remaining, and has a birefringence Δn.
At least one of 1 or Δn2 is 0.02 or more, and the birefringence Δn3 of the metal plate side portion is Δn1 or Δn2.
It is most preferable that it is smaller than n2 in terms of ensuring dent resistance and adhesion.

Referring to FIG. 7 for explaining the method of manufacturing the polyester-metal laminate, a metal plate 20 is heated by a heating roll 21 to a temperature (T1) higher than the melting point (Tm) of the polyester used. To supply. On the other hand, the polyester film 23 is unwound from the supply roll 24,
It is supplied in a positional relationship in which the metal plate 20 is sandwiched between 22. Laminating rolls 22 and 22 are heated roll 2
A temperature (T2) slightly lower than 1 is maintained, and a polyester film is thermally bonded to both surfaces of the metal plate 20. Below the laminating rolls 22, a water tank containing cooling water 26 for rapidly cooling the laminate 25 to be formed is provided, and a guide roller 27 for guiding the laminate into the water tank is arranged. Laminating roll 2
A gap 28 is formed at a certain interval between the cooling water 2 and 22 and the cooling water 26, and a heat retaining mechanism 29 is provided in the gap 28 to keep the temperature in a certain temperature range (T3). In the transition state to the phase, it is preferable that a peak of biaxial orientation is formed in the middle of the film thickness direction due to the return of orientation.

The heating temperature (T1) of the metal plate is generally Tm
+ 0 ° C to Tm + 100 ° C, especially Tm + 0 ° C to Tm +
A temperature of 50 ° C. is suitable, while the laminating roll 11
Temperature T2 is 70 ° C to 180 ° C, especially 80 ° C to 1 ° C.
A range of 50 ° C. is appropriate. By adjusting the temperature of the metal plate or the temperature of the laminating roll within this range,
The biaxial orientation remaining amount of the film, that is, the birefringence of the film in the laminate can be controlled to a better state.
That is, a temperature gradient corresponding to the temperature difference is formed in the polyester on the metal plate by the above temperature setting, so that a portion in the thickness direction from the surface side of the polyester to the metal plate side is formed from the molten phase. It is preferable that the temperature is maintained in a temperature region in which a return phenomenon of the orientation occurs in the transition state to the solid phase for a sufficient time. For this reason, it is effective to keep the temperature of the laminate after passing through the laminating rolls in a heat retaining region.

The adhesive primer optionally provided between the 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, Particularly, a phenol resin and an epoxy resin are mixed in a ratio of 50: 5
0 to 5:95 weight ratio, especially 40:60 to 10:90
Is a paint contained in a weight ratio of

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 FIG. 8 showing an example of the seamless can of the present invention, the seamless can 11 is made of the polyester-metal laminate 1 described above.
Formed by bending and stretching by drawing or redrawing or further ironing, and is composed of a bottom portion 10 and a side wall portion 12. A neck portion 13 is provided on the upper end of the side wall portion 12 if desired.
The flange portion 14 is formed through the opening. This can 11
In this case, the side wall portion 12 is thinner than the bottom portion 10 by bending or stretching or further ironing so as to have a thickness of 30 to 85% of the original thickness of the laminate.

In the seamless can of the present invention, the above-mentioned polyester-metal laminate is drawn and deep drawn into a cup having a bottom between a punch and a die. It is manufactured by thinning. 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. 9, 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. . Coaxially with the holding member 31 and the redrawing-ironing die 32,
A re-drawing-ironing punch 33 is provided so as to be able to get in and out of the inside. 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 a working corner portion 35 having a small radius of curvature on the periphery of the flat portion, and the diameter increases downward toward the 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 small curvature portion 37. Below the land portion 38, a reverse tapered relief 3
9 are provided.

The side wall 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 and re-drawn 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
Its outer surface comes into contact with the approach portion 36 having a small taper angle whose diameter gradually increases, and its 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. According to the present invention, the outer surface of the side wall portion is brought into contact with the approach portion 36 to reduce the diameter thereof, and the inner surface side is free. It prevents the occurrence of uneven distortion inside the film, 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 redrawing-ironing punch 33, and is rolled to a thickness regulated by the gap (C1). You. The thickness C1 of the final side wall is determined to be 30 to 85% of the original thickness (t) of the laminate. The small curvature portion 37 on the ironing portion introduction side smoothly introduces the laminated body into the ironing portion 38 while effectively fixing the ironing start point, and has a reverse tapered shape below the land portion 38. The relief 39 prevents 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 5 °. 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 curvature radius Ri of the small curvature portion 37 is determined by the thickness (t) of the laminate in order to effectively fix the ironing start point.
However, if the radius of curvature is too large, the laminate will be scraped. Therefore, it is particularly preferable that the thickness be not more than 20 times the thickness (t) of the laminate.

The ironing land 38, the re-drawing-ironing punch 33 and the clearance are in the above-mentioned ranges, but the land length L is generally preferably 0.5 to 30 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 at the flange portion is subjected to severe tightening, it is preferable that the polyester layer is mildly processed as compared with the polyester layer at 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 1.0 to 2.0, especially 1.0.
It is good to set it in the range of 0 to 1.7.

In FIGS. 10, 11 and 12, which show the seamless can after redrawing and ironing, the seamless can 5
Numeral 0 includes a bottom portion 51 having substantially the same thickness as the blank pressure and a side wall portion 52 thinned by redrawing and ironing, and a thicker flange is formed on the upper portion of the side wall portion 52. A portion 53 is formed.

The flange forming portion has various structures.
In the example shown in FIG. 11, 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, and the inner surface of the flange forming portion 53 'has a smaller diameter than the inner surface of the side wall portion 52'. have. This type of flange forming portion 53 '
Is formed by making the portion where the side wall portion is extended and the flange forming portion 53 'is located in the redrawing-ironing punch 32 smaller in diameter than other portions.

In the example shown in FIG. 10 of the flange forming portion,
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 has a larger diameter than the outer surface of the side wall portion 52. This type of flange forming portion 53 reduces the length L of the land portion of the re-drawing and ironing die, and provides a portion following the land portion with a smaller diameter than the land portion so that the flange forming portion 53 returns. It is formed by deforming.

In the example shown in FIG. 12 of the flange forming portion,
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 smaller diameter than the inner surface of the side wall portion 52".
In this type of flange forming portion 53 ″, the portion where the side wall portion is extended and the flange forming portion 43 is located in the redrawing and ironing punch 32 is made smaller in diameter than other portions, and the redrawing and ironing punch 32 is used. The length L of the land portion of the die is reduced, and a portion having a smaller diameter than the land portion is provided at a portion following the land portion, and the flange forming portion 43 is formed by returning and deforming.

In producing the seamless can of the present invention, the polyester layer on the surface imparts sufficient lubricating performance. However, in order to further enhance the lubricity, a small amount of a lubricant such as various oils or waxes is used. Can be applied. 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 ironing) is preferably 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 temperature of 40 ° C., particularly preferably 190 ° C. to 230 ° C., is suitable. Although it depends on the melting point of the film, if the heat treatment temperature is higher than this range, it tends to be difficult to leave the biaxial orientation in the polyester layer. 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.

[0085]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples. Various measured values are
It was determined by the following measurement method.

(1) Adjustment of Transesterification Rate The transesterification rate in Examples was determined by blending a crystalline polyester mainly composed of polyester and a crystalline polyester mainly composed of butylene terephthalate in a reactor, and controlling the amount of water in the atmosphere. While the resin temperature is 260-280 ° C,
The transesterification rate was adjusted by setting the kneading time to 5 minutes to 90 minutes.

(2) Calculation of the transesterification rate The transesterification rate is determined using the following equation (1). E = 100 · [1-exp {(Hu / R) · (1 / Tm0−1 / Tm)}] (1) where Hu: heat of fusion of the crystalline polyester mainly composed of ethylene terephthalate units 9200 ( J / mol) R: gas constant 8.314 (J / (mol · K)) Tm: melting point of blend (K) Tm0: melting point of crystalline polyester mainly composed of ethylene terephthalate units (K) Tm in the formula (Melting point of the blend) The isolated film of the laminate was heated at 280 ° C. for 2 minutes under the DSC (differential scanning calorimeter) conditions shown below, and then immediately at 500 ° C.
/ Minute, and the temperature at which the calorific value peaks on a DSC curve raised from room temperature again under the following conditions was taken as the melting point of the blend. The isolated film of the laminate was obtained by immersing the can body in an 18% aqueous hydrochloric acid solution at room temperature, dissolving the metal plate, and then washing and drying the film. In the case of a two-layer film, the surface layer was scraped off and only the lower layer film was isolated by the above method. DSC apparatus: DSC7 type manufactured by PerkinElmer Inc. Temperature rising rate: 20 ° C./min Weighing: 5 to 10 mg Further, regarding Tm0 (melting point of crystalline polyester mainly composed of ethylene terephthalate unit), the isophthalic acid shown in FIG. A graph (experimental value) showing the relationship between the polymerization ratio and the melting point was used.

(3) IV (intrinsic viscosity) A film was isolated from the laminate by the above-mentioned method (as it is in the case of a two-layer film), and 200 mg of phenol /
It was dissolved in a 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′ηsp) ^1/2 ２ / 2K′C] (dl / g) K ′: Haggins constant (= 0.33) C: Concentration (g / 100 ml) ηsp: Specific viscosity [= (fall time of solution−fall time of solvent) / fall time of solvent]

(4) Storage test A sports drink was hot-filled at 90 ° C., allowed to cool, and the filled can was cooled to 5 ° C., and the can axis was tilted by 15 ° with respect to the vertical direction to increase the height by 50 cm. I dropped it and gave it a shock. Thereafter, a storage test was performed at a temperature of 37 ° C., and one year later, the can was opened, and the corrosion state of the peripheral polyhedral wall ridge on the inner surface side was observed. Corrosion was also observed for the part that was impacted by the drop.

(5) Birefringence: The laminate and the bottom of the can were cut into 5 mm squares, and a film was isolated by the same method as described in the above method (2) (in the case of a two-layer film,
The surface layer was scraped off). The isolated film was subjected to vacuum drying for 24 hours to obtain a sample. This sample film is embedded in epoxy resin, and 3
It was cut out to a size of μm, and the retardation was measured with a polarizing microscope. The value of birefringence was an average value at five points on the cross section. Here, Δn1 is an average value of up to 2 μm from the film surface side, and Δn3 is an average value of up to 2 μm from the metal plate side of the film. Δn2 is an average value of 2 μm centered on a half position of the film thickness. The measurement wavelength at that time is 54
6 nm was used.

Example 1 The following TFS steel plate was used as a metal plate. TFS steel sheet: 0.195 mm thickness, temper T-4, chromium metal content 110 mg / m ² , chromium hydrate oxide content 15 m
g / m ² A polyester film of the following (1) on one side of this metal plate,
On the other side, a polyester film of (2) below,
50 ° C, laminating roll temperature 150 ° C, passing speed 40
Both sides were simultaneously heat-laminated at m / min and immediately cooled with water to obtain a laminated metal plate. Polyester film (1) (can outer surface side): White resin obtained by blending 20% by weight of titanium oxide (pigment) with polyester resin consisting of 12% by mole of isophthalic acid, 88% by mole of terephthalic acid and 100% by mole of ethylene glycol. A biaxially stretched film (thickness: 13 μm) obtained by stretching a polymer polyester resin under the conditions of 3.0 times length and 3.0 times width. Polyester film (2) (inside of can): polyester resin (i) comprising 6 mol% of isophthalic acid, 94 mol% of terephthalic acid and 100 mol% of ethylene glycol,
Terephthalic acid 80 mol% (a), adipic acid 20 mol%
(B) Polyester blend obtained by blending 100% by mole of 1,4-butanediol with copolymerized polyester resin (ii) at a weight ratio of 55:45, and controlling the transesterification reaction by kneading. 2. Vertically
A biaxially stretched film (25 μm in film thickness) stretched under the condition of 0 × 3.0. A wax-based lubricant was applied to the coated metal plate obtained above, and a disk having a diameter of 158 mm was punched out so that the polyester film (1) side was the outer surface of the can to obtain a shallow drawn cup. Next, the shallow drawn cup was redrawn and ironed to obtain a deep drawn and ironed cup.

Various characteristics of the deep drawing cup were as follows. Cup diameter: 52 mm Cup height: 140 mm 73% of the thickness of the can wall relative to the base plate thickness 85% of the thickness of the flange portion relative to the base plate thickness

The deep drawn ironing cup was subjected to doming molding according to a conventional method, and heat treatment was performed at 220 ° C., after which the cup was allowed to cool, trimming the edge of the opening, curved surface printing and baking drying, and necking. Processing, flange processing, and peripheral polyhedral wall processing were performed to obtain a seamless can for 250 g. The circumferential polyhedral wall includes the minimum structural unit surface shown in FIGS.
60mm with 1/2 phase difference in the container axis direction
L / W is 0.96, and the depth ratio d1 / d0 is 0.
95, the concave unit was provided such that the concave curvature R of the structural unit surface was 5t.

Next, after the sports drink was hot-filled at 90 ° C. and sufficiently cooled, the filling can was cooled at 5 ° C. to 50 c.
After dropping from a height of m, the bottom of the can was made to collide with a stainless steel wedge (angle 15 °) placed on a concrete floor, stored at 37 ° C for one year, and observed the corrosion state of the can bottom impact part. .

As a result of analyzing the polyester film (2) in the laminate used for producing the can, the transesterification rate was 1.2% and the IV was 1.15. Table 2 shows the characteristic values and evaluation results of the film. Good results were obtained for both the corrosion resistance of the can wall and the corrosion resistance of the impact part. Also polyester film of laminated metal plate before forming into cans (2)
And polyester film at the bottom of the molded can
Table 3 shows the measured values of the birefringence of (2).

Example 2 Example 1 was repeated except that the biaxially oriented polyester film (2) provided on one side (the inner side of the can) of the TFS steel sheet was replaced with the following biaxially oriented laminated film (3). Example 1
A laminated metal plate was obtained in the same manner as described above (however, the plate temperature during thermal lamination was 240 ° C.). Biaxially stretched laminated film (3): Thickness: 25 μm, Stretching ratio: 3.0 times in length × 3.0 times in width Surface layer: polyester resin used for preparing polyester film (1) (without pigment). 5 μm thick. Lower layer (metal plate side); blend ratio (weight ratio) of polyester resin (i) and copolymerized polyester resin (ii) is 70: 3.
The same blend as that used to make the polyester film (2), except that it was changed to 0. 20 μm thick. Using the laminated metal plate, can making and a corrosion test were performed in the same manner as in Example 1. As a result of analyzing the lower layer of the biaxially stretched laminated film (3) in the laminate used for producing this can, the transesterification rate was 5.1% and the IV was 0.66. Table 2 shows the characteristic values and evaluation results of the film.
Good results were obtained for both the corrosion resistance of the can wall and the corrosion resistance of the impact part. Table 3 shows the birefringence of the biaxially stretched laminated film (3) of the laminated metal sheet before forming into a can and the measured birefringence of the film (3) at the bottom of the formed can.

Example 3 The biaxially stretched laminated film (4) obtained by changing the composition of the lower layer blend of the biaxially stretched laminated film (3) (inner side of the can) used in Example 2 as follows: A laminated metal plate was prepared, canned, and subjected to a corrosion test in the same manner as in Example 2 except that the axially stretched laminated film (3) was used instead. Composition of lower layer blend of biaxially stretched laminated film (4): polyester resin (i) composed of 8 mol% of isophthalic acid, 92 mol% of terephthalic acid and 100 mol% of ethylene glycol, 70 mol% of terephthalic acid (a), A 55:45 (weight ratio) blend with a copolymer resin (ii) consisting of 30 mol% of adipic acid (b) and 100 mol% of 1,4-butanediol. As a result of analyzing the lower layer of the biaxially stretched laminated film (4) in the laminate used for manufacturing this can, the transesterification rate was 2.5% and the IV was 0.75. Table 2 shows the characteristic values and evaluation results of the film. Good results were obtained for both the corrosion resistance of the can wall and the corrosion resistance of the impact part. Further, a biaxially stretched laminated film (4) of a laminated metal plate before forming into a can and the film (4) at the bottom of the formed can
Are shown in Table 3.

Comparative Example 1 In Example 1, the polyester film on the inner surface side of the can was used.
(2) is a biaxially stretched polyester resin film composed of 12 mol% of isophthalic acid, 88 mol% of terephthalic acid and 100 mol% of ethylene glycol (5) (25 μm in thickness)
A laminated metal sheet was prepared in the same manner as in Example 1 except that the temperature was changed to 240 ° C.
A canning and corrosion test was performed. As a result of analyzing the biaxially stretched film (5) in the laminate used for manufacturing the can,
IV was 0.64. Table 2 shows the characteristic values and evaluation results of the film. The corrosion resistance of the peripheral polyhedral wall ridge was good, but the film was significantly cracked at the impacted portion, causing corrosion and judged to be unsuitable for practical use. Table 3 shows the measured birefringence of the biaxially stretched film (5) of the laminated metal sheet before forming into a can and the film (5) at the bottom of the formed can.

Comparative Example 2 Biaxially stretched laminated film (3) on the inner surface side of the can used in Example 2
Preparation of a laminated metal plate in the same manner as in Example 2 except that the biaxially stretched laminated film (6) in which the composition of the lower layer blend was changed as follows was used instead of the biaxially stretched laminated film (3) (However, the sheet temperature during the heat lamination was 245 ° C.), a can-making test and a corrosion test were performed. Composition of lower layer blend of biaxially stretched laminated film (6): polyester resin (i) comprising 6 mol% of isophthalic acid, 94 mol% of terephthalic acid and 100 mol% of ethylene glycol, 100 mol% of terephthalic acid, 1,4 7 with a copolymer resin (ii) consisting of 100 mol% of butanediol
0:30 (weight ratio) blend. As a result of analyzing the lower layer of the biaxially stretched laminated film (6) in the laminate used for producing this can, the transesterification rate was 3.5% and the IV was 0.7.
It was 0. Table 2 shows the characteristic values and evaluation results of the film. Corrosion resistance of the peripheral polyhedron wall ridge was good,
It was judged that the film was broken at the impact portion and corrosion occurred, and it was not practically applicable. Table 3 shows the birefringence of the biaxially stretched laminated film (6) of the laminated metal plate before forming into a can and the measured birefringence of the film (6) at the bottom of the formed can.

Comparative Example 3 Biaxially stretched laminated film (3) on the inner surface side of the can used in Example 2
Preparation of a laminated metal plate in the same manner as in Example 2 except that the biaxially stretched laminated film (7) in which the composition of the lower layer blend was changed as follows was used instead of the biaxially stretched laminated film (3) (However, the sheet temperature during the heat lamination was 245 ° C.), a can-making test and a corrosion test were performed. Composition of lower layer blend of biaxially stretched laminated film (7): polyester resin (i) composed of 6 mol% of isophthalic acid, 94 mol% of terephthalic acid and 100 mol% of ethylene glycol, 80 mol% of terephthalic acid, and 20 of isophthalic acid
A 70:30 (weight ratio) blend with a copolymer resin (ii) consisting of 100 mol% of 1,4-butanediol and 100 mol% of 1,4-butanediol. As a result of analyzing the lower layer of the biaxially stretched laminated film (7) in the laminate used for producing the can, the transesterification rate was 3.2% and the IV was 0.68. Table 2 shows the characteristic values and evaluation results of the film. Although the corrosion resistance of the peripheral polyhedral wall ridge was good, the impact portion had a large film crack and corrosion occurred, so it was judged that it was not practically suitable. Further, a biaxially stretched laminated film (7) of a laminated metal plate before forming into a can and the film at the bottom of the formed can
Table 3 shows the measured values of the birefringence of (7).

Comparative Example 4 Biaxially stretched laminated film (3) on the inner surface side of the can used in Example 2
And the composition is exactly the same, but the biaxially stretched laminated film (8), in which the melt kneading time is extended to increase the transesterification rate in the preparation of the lower layer blend, and the biaxially stretched laminated film (3)
Except for using in place of the above, a laminated metal plate was prepared in the same manner as in Example 2 (however, the plate temperature during thermal lamination was 240
0 C), can making and corrosion tests. As a result of analyzing the lower layer of the biaxially stretched laminated film (8) in the laminate used for producing this can, the transesterification rate was 23.2% and the IV was 0.66. Table 2 shows the characteristic values and evaluation results of the film. At the time of molding, a partial crack occurred in the inner surface film, and the surface of the inner film of the can after the heat treatment became wrinkled, which was judged to be impractical. Table 3 shows the birefringence of the biaxially stretched laminated film (8) of the laminated metal sheet before forming into a can and the measured birefringence of the film (8) at the bottom of the formed can.

Comparative Example 5 The composition was exactly the same as that of the biaxially stretched laminated film (8) used in Comparative Example 4, but the IV was significantly reduced by increasing the temperature during melt-kneading in preparing the lower layer blend. Except for using the biaxially stretched laminated film (9), a laminated metal plate was prepared, canned, and subjected to a corrosion test in exactly the same manner as in Comparative Example 4. As a result of analyzing the lower layer of the biaxially stretched laminated film (9) in the laminate used for producing this can, the transesterification rate was 7.6% and the IV was 0.52. Table 2 shows the characteristic values and evaluation results of the film. The peripheral polyhedron wall ridge line was partially corroded, a film crack at the impact portion was observed, and corrosion occurred, and it was judged that the film was not practically applicable. Table 3 shows the birefringence of the biaxially stretched laminated film (9) of the laminated metal plate before forming into a can and the measured birefringence of the film (9) at the bottom of the formed can.

Comparative Example 6 A biaxially stretched laminated film (10) was prepared by changing the composition of the lower layer blend of the biaxially stretched laminated film (3) used in Example 2 as follows. Except for using in place of 3), a laminated metal plate was prepared (however, the plate temperature during thermal lamination was 240 ° C.), and a can-making and corrosion test were carried out in the same manner as in Example 2. Composition of lower layer blend of biaxially stretched laminated film (10): polyester resin (i) composed of 6 mol% of isophthalic acid, 94 mol% of terephthalic acid and 100 mol% of ethylene glycol, and 80 mol% of terephthalic acid (a); A 20:80 (weight ratio) blend with a copolymer resin (ii) consisting of 20 mol% of adipic acid (b) and 100 mol% of 1,4-butanediol. As a result of analyzing the lower layer of the biaxially stretched laminated film (10) in the laminate used for producing this can, the transesterification rate was 4.8% and the IV was 0.70. Table 2 shows the characteristic values and evaluation results of the film. The peripheral polyhedron wall ridge line was partially corroded, a film crack at the impact portion was observed, and corrosion occurred, and it was judged that the film was not practically applicable. Table 3 shows the birefringence of the biaxially stretched laminated film (10) of the laminated metal plate (laminate) before forming into a can and the measured birefringence of the film (10) at the bottom of the formed can.

[0104]

[Table 2]

[0105]

[Table 3]

[0106]

According to the present invention, a specific copolymerized polyester, that is, (a) an ester unit derived from butylene glycol and an aromatic dibasic acid, and (b) a butylene glycol and an aliphatic dibasic acid are used. 9 derived units
By blending a copolyester containing a molar ratio of 0:10 to 50:50 with an ethylene terephthalate-based polyester and using a polyester composition having a transesterification rate controlled in a specific range for lamination on a metal substrate. Thus, a metal-polyester laminate having significantly improved impact resistance, particularly dent resistance, and a seamless container formed from this laminate can be provided.

[0107] Despite advanced drawing or ironing, or heat treatment during or after can making, embrittlement due to crystallization is suppressed, and excellent dent resistance is maintained. Neck-in processing and flange processing of the upper part of the can body that have been performed have been facilitated, and the dent resistance of this part can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the environmental temperature of a dent test and the enamel value after a dent test.

FIG. 2 is a graph showing the relationship between each part of a seamless can and the heat of fusion in differential thermal analysis of a polyester layer.

FIG. 3 is a graph showing the relationship between the heat of fusion of the polyester layer by differential thermal analysis and the enamel value after a dent test.

FIG. 4 is a graph showing the relationship between temperature and loss modulus for various polyester layers.

FIG. 5 is an enlarged sectional view showing an example of a sectional structure of a laminate used in the present invention.

FIG. 6 is an enlarged cross-sectional view showing another example of the cross-sectional structure of the laminate used in the present invention.

FIG. 7 is a sectional view of an apparatus for manufacturing a laminated plate.

FIG. 8 is a sectional view showing an example of the seamless can of the present invention.

FIG. 9 is a cross-sectional view showing a main part of the drawing and ironing apparatus for a seamless can of the present invention.

FIG. 10 is a sectional view showing an example of a flange portion of the seamless can of the present invention.

FIG. 11 is a sectional view showing another example of the flange portion of the seamless can of the present invention.

FIG. 12 is a sectional view showing another example of the flange portion of the seamless can of the present invention.

FIG. 13 is a graph (experimental value) showing the relationship between the copolymerization ratio of isophthalic acid and the melting point.

FIGS. 14A and 14B show an example of a container provided with a polyhedral wall having a quadrilateral as a constituent unit surface, wherein FIG. 14A is a plan view, FIG. 14B is a longitudinal sectional view, and FIG.

15A and 15B show an example of a constituent unit surface of a polyhedral wall formed on a side surface of the container of FIG. 14, wherein FIG.
(C) and (D) are vertical cross-sectional views of the structural unit surface, showing the curvature radius of the depressed portion changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated body 2 Metal substrate 3 Polyester blend layer 4 Outer surface coating 5 Adhesive primer layer 10 Bottom part 11 Seamless can 12 Side wall part 13 Neck part 14 Flange part 20 Metal plate 21 Heating roll 22, 22 Laminating roll 23 Polyester film 24 Supply Roll 25 Laminate 26 Cooling water 27 Guide roller 28 Gap 29 Heat retaining mechanism 30 Front drawing cup 31 Annular holding member 32 Redrawing-ironing die 33 Redrawing-ironing punch 34 Flat part 35 Working corner part 36 Approach part 37 Small curvature part 38 Land Part (ironing part) 39 Reverse tapered relief 40 Outer peripheral surface 41 Curvature corner part 42 Annular bottom surface 43 Flange forming part 50 Seamless can 51 Bottom part 52 Side wall part 53 Flange forming part 61 Structural unit surface 62 Boundary ridgeline 63 Intersection 65 parts 66 side wall portion 67 closed bottom 68 the lid between intersections

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuo Miyazawa 1328-60 Kozono, Ayase-shi, Kanagawa Prefecture (72) Inventor Katsuhiro Imazu 625-1 Izumi-cho, Izumi-ku, Yokohama-shi, Kanagawa Prefecture 27-101 Greenheim Izumino

Claims (10)

[Claims] 1. A laminate comprising a metal substrate and a biaxially stretched polyester film layer thermally bonded to the metal substrate, wherein the polyester film comprises (i) a crystalline polyester mainly composed of ethylene terephthalate units and (ii) ( a) an ester unit derived from butylene glycol and an aromatic dibasic acid; and (b) an ester unit derived from butylene glycol and an aliphatic dibasic acid.
(I): (i)
i) is formed from a blend containing a weight ratio of 90:10 to 30:70, and the transesterification rate (E) of component (i) in the blend represented by the following formula (1) is 0.5 to 2:
0% and the intrinsic viscosity of the blend (IV)
Is not less than 0.55: E = 100 · [1-exp {(Hu / R) · (1 / Tm0−1 / Tm)}] (1) where Hu: Heat of fusion of crystalline polyester mainly composed of ethylene terephthalate unit 9200 (J / mol) R: gas constant 8.314 (J / (mol · K)) Tm: melting point of blend (K) Tm0: ethylene terephthalate unit Melting point (K) of the main crystalline polyester (i). 2. The laminate according to claim 1, wherein the polyester (i) is polyethylene terephthalate or polyethylene terephthalate / isophthalate containing an ethylene isophthalate unit in an amount of 20 mol% or less. 3. The laminate according to claim 1, wherein the copolyester (ii) is polybutylene terephthalate / adipate. 4. The polyester film layer of the laminate represented by the following formula (2) has a birefringence of Δn on the film surface side.
1. At the intermediate position of the film from the surface to the metal plate, Δn2
.DELTA.n3 on the side in contact with the metal plate, .DELTA.n1 and .DELTA.n
n2 is at least 0.02 and Δ
4. The laminate according to claim 1, wherein n3 is not more than .DELTA.n1 or .DELTA.n2, wherein .DELTA.n1-3 = nm-nt (2) where nm is the refractive index in the maximum orientation direction of the film. Where nt is the refractive index in the thickness direction of the film. 5. A laminate comprising a metal substrate and a biaxially stretched polyester film layer thermally bonded thereto, wherein said polyester film layer comprises: (A) a crystalline polyester surface layer mainly composed of ethylene terephthalate units; (B) (i) a crystalline polyester mainly composed of ethylene terephthalate units, (ii) (a) an ester unit derived from butylene glycol and an aromatic dibasic acid, and (b)
(I) :( ii) = 90: 10 to 30:70 copolymerized polyester containing butylene glycol and an ester unit derived from an aliphatic dibasic acid in a molar ratio of 90:10 to 50:50. The transesterification rate (E) of the component (i) in the blend, which is represented by the following formula (1), is in the range of 0.5 to 20%. And a laminate characterized in that the intrinsic viscosity (IV) of the blend is 0.55 or more: E = 100 · [1-exp ｛(Hu / R) · (1 / Tm0−1 / Tm) ｝] (1) where: Hu: heat of fusion of crystalline polyester mainly composed of ethylene terephthalate units: 9200 (J / mol) R: gas constant: 8.314 (J / (mol · K)) Tm: blend Melting point (K) of Tm0: ethyl Melting point of the crystalline polyester to the terephthalate units mainly (i) (K). 6. The polyester of the surface layer (A) and the polyester (i) of the underlayer (B) are polyethylene terephthalate or polyethylene terephthalate / isophthalate containing an ethylene isophthalate unit in an amount of 20 mol% or less. Item 6. The laminate according to Item 5. 7. The laminate according to claim 5, wherein the copolymerized polyester in the base layer (B) is polybutylene terephthalate / adipate. 8. The polyester film layer of the laminate represented by the following formula (2) has a birefringence of Δn on the film surface side.
1. At the intermediate position of the film from the surface to the metal plate, Δn2
.DELTA.n3 on the side in contact with the metal plate, .DELTA.n1 and .DELTA.n
n2 is at least 0.02 and Δ
8. The laminate according to claim 5, wherein n3 is not more than .DELTA.n1 or .DELTA.n2: where .DELTA.n1-3 = nm-nt (2) nm is the refractive index in the maximum orientation direction of the film. Where nt is the refractive index in the thickness direction of the film. 9. A seamless container formed by drawing or ironing the laminate according to claim 1. Description: 10. The polyester film layer at the bottom of the seamless container represented by the following formula (2) has a birefringence of Δn1 on the surface side of the film and Δn2 at an intermediate position of the film from the surface to the metal plate, and contacts the metal plate. Assuming Δn3 on the side,
10. The seamless container according to claim 9, wherein at least one of Δn1 and Δn2 is 0.02 or more, and Δn3 is Δn1 or Δn2 or less, provided that Δn1−3 = nm−nt (2) nm is the refractive index in the maximum orientation direction of the film, and nt is the refractive index in the thickness direction of the film.