JP2001122258A - Laminate lid, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a can lid which is excellent in openability, feathering resistance, workability and corrosion resistance, small in environmental load, and excellent in the working environment during the manufacture without causing any defective opening such as delamination and feathering in making an opening by piercing an unsealing tab tip or tearing an opening part to cut a score. SOLUTION: In the resin laminate lid having a scoring part, a polyester resin layer is provided at least on an inner surface side of a can, and the molecular weight of the polyester resin on the inner surface resin layer of a portion along the scoring part is 25,000 to 70,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated lid made of a polyester resin-coated metal plate and a method for producing the same, and more particularly, to cutting a score by pushing a tip of an opening tab or tearing off an opening. The present invention relates to a laminate lid having improved opening properties at the time of opening and improved content resistance, and a method for producing the laminate lid with high environmental compatibility and high productivity.

[0002]

2. Description of the Related Art Conventionally, a can body with an easy-open lid which can be easily opened by hand without using any special tool has been widely used. This can lid is made of aluminum, aluminum alloy, tinplate, TFS as a metal material, and a score is provided on the can lid made of this metal plate so as to reach the middle of the thickness direction of the metal plate to form an opening portion. are doing. A tear-off type in which the opening is torn off with a handle to separate it from the can, and a stay-on tab (SO
T) There is an equation.

[0003] With this easy-open lid, the inner coating film is damaged during score processing and rivet processing.
It is necessary to perform correction coating after processing.

Japanese Patent Laid-Open Publication No. Sho 62-52045 discloses a can lid which does not require such a correction coating and has excellent corrosion resistance. A biaxially oriented polyethylene terephthalate film layer having a thickness of 10 to 40 μm, a composite material of an aluminum substrate and an epoxy-phenol resin-based adhesive primer layer having a thickness of 0.3 to 3 μm interposed between the film layer and the aluminum substrate. There is described an easy-open lid in which a score is formed so as to reach the middle in the thickness direction.

Japanese Unexamined Patent Publication (Kokai) No. 63-12445 discloses that when the above-mentioned composite material comes into contact with a tool or a transfer tool, pinholes and cracks are prevented from being generated on the film. It has been proposed to provide a layer of a lubricant containing epoxy-based thermosetting resin coating.

Further, Japanese Patent Application Laid-Open No. 3-63124 discloses that
In an easily openable metal lid that is opened by cutting the score by an opening piece, a metal material for the lid, and a polyester biaxially oriented film mainly composed of ethylene terephthalate units provided on at least the inner surface side of the metal material for the container. Wherein the film has the following formula: 17 ≧ I ₍₁₀₀₎ / I ₍₁₁₀₎ ≧ 4 where I ₍₁₀₀₎ is parallel to the polyester coating (1
X) diffraction intensity according to ₍ 00), I ₍₁₁₀₎ is the X-ray diffraction intensity due to (110) parallel to the polyester coating,
Easy open with excellent corrosion resistance, opening property and feathering resistance, characterized by having an X-ray diffraction intensity ratio satisfying the following, and having an anisotropy index of in-plane orientation of the crystal of 30 or less. A container lid is described.

[0007] As an easily openable container lid (easy open lid), in order to eliminate the possibility that the cut-out opening piece is littered on the road or the like, the opening tab or the opening piece is left connected to the lid. So-called stay-on tab (SOT)
Easy opening container lids of the type have also become widely used.

Japanese Patent Application Laid-Open No. 7-51779 discloses a method of laminating a crystalline saturated polyester resin to prevent processing defects due to press working and to achieve feathering resistance at the time of opening.
There is described a method for producing a metal easy-opening lid material, which comprises performing a heat treatment at a temperature from a cold crystallization start temperature to a temperature lower than a melting point after pressing.

[0009]

In an easily openable container lid of the SOT type, the score is cut by pressing the tip of the opening tab to open the score. In this opening operation, the inner resin layer of the laminate plate is stretched. Since the score is cut in such a manner as to be cut, delamination tends to occur between the metal base material and the inner resin layer.

[0010] A full-open can generally used as a food can is of a tear-off type. At the initial stage of opening, the score is cut by pushing the tip of an opening tab as in the SOT type, and the score is cut. To separate it from the can body. Even in this case, for the same reason as in the SOT format,
Delamination tends to occur between the metal substrate and the inner resin layer.

In addition, even when the adhesion between the metal substrate and the inner resin layer is large and no significant delamination occurs, an organic film extending around the opening remains, that is, a so-called feathering phenomenon occurs. The feathering phenomenon is hated because it gives an unsanitary image in appearance. This phenomenon is often considered to be a problem even in a can lid made of a conventional painted metal plate, and is particularly remarkable when an unstretched polyester resin is laminated.

Particularly, as contents, green tea drink, black tea drink,
For canned products filled with coffee drinks, soups, soup flours, meat sauces, etc., they are often taken out in a hot bender or hot water and opened, and in this case, the inner resin layer is compared to room temperature. The feathering phenomenon is conspicuous because the particles are easily stretched.

On the other hand, in the conventional proposal using the above-mentioned laminated plate, a resin may be laminated on a metal material before molding, and a baking furnace for a paint film and a facility for treating paint exhaust gas are not required as in a normal coating process. Thus, there is provided an advantage that there is no air pollution and the working environment at the time of manufacturing the lid is excellent.

[0014] Further, a proposal of performing pressing in a state where the degree of crystallization is small and the elongation is large in order to prevent processing defects is extremely effective in securing workability and corrosion resistance.

However, it is industrially difficult to prevent feathering by promoting crystallization by cold heat treatment after pressing to suppress elongation. That is, the degree of crystallinity of the polyester is at most 60% even under sufficient time and temperature conditions, and the rest is due to the non-crystalline structure, which maintains elongation. For this reason, feathering cannot be sufficiently suppressed, and the aperture is not sufficient.

Accordingly, it is an object of the present invention to provide a method for opening a sheet without cutting defects such as delamination or feathering when cutting the score by pushing the tip of the opening tab or tearing off the opening. -To supply can lids that have excellent feathering properties, workability, and corrosion resistance, and have a low environmental load and an excellent working environment during manufacturing.

[0017]

According to the present invention, in a resin laminated lid having a scored portion, a polyester resin layer is provided at least on the inner surface side of the can, and the inner surface of a portion along the scored portion is provided. A laminate lid is provided, wherein the molecular weight of the polyester resin in the resin layer is in the range of 25,000 to 70000. In the laminate lid of the present invention, 1. Among the polyester resin layers, at least one of the inner and outer surfaces of the can lid is substantially unstretched; In the initial opening portion, the in-plane birefringence Δ of the inner resin layer
N is preferably 0.020 or less. According to the present invention, a laminate having a polyester resin layer provided on at least one surface of an aluminum plate or a steel plate is subjected to a scoring process, and then at least the resin layer near the opening is heat-treated. A method is provided.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Action] The inventors of the present invention have conducted intensive studies on a laminated lid with a score that is opened by pushing an opening or tearing the opening. As a result, delamination and feathering phenomena have been observed. It was found that the molecular weight of the resin on the inner surface of the lid in the vicinity of the score was most affected by the molecular weight of the resin instead of the degree of chemical conversion, and that there was an appropriate range for this molecular weight.

In addition, the initial opening often overlaps with a portion to be thinned, such as around the rivet, and delamination is most likely to occur at the time of opening. It has also been found that when the resin on the inner surface of the lid at this portion has excessive internal distortion, delamination becomes significant.

In FIG. 6 of the accompanying drawings, the weight average molecular weight (Mw) of the inner polyester resin layer is plotted on the abscissa with respect to the polyester resin laminated lid, and the heat of crystallization of this resin layer (the smaller the absolute value is, the higher the crystallinity becomes. Is higher) on the vertical axis,
The results of testing the opening property of the laminate lid by the method of the examples described later are shown. According to the results, the degree of crystallinity of the polyester hardly affects the opening of the laminate lid. Rather, the fact that the weight average molecular weight of the polyester is within a certain range prevents the occurrence of phasoring and improves the opening. The fact that it is important to improve becomes apparent.

In the present invention, the weight average molecular weight (M
w) is in the range of 25,000 to 70000,
It is important in terms of openability and corrosion resistance. That is, when the weight-average molecular weight of the inner polyester resin layer exceeds 70,000, phasoring occurs in the opening at the time of opening by cutting at the score processing portion, and delamination (hereinafter, also simply referred to as delamination) occurs in the opening. It is not preferable because the tendency to occur increases. On the other hand, when the weight average molecular weight of this resin layer is less than 25,000, the corrosion resistance of the laminate lid is lowered, and furthermore, the coating properties of the inner resin layer, particularly the mechanical strength, are not preferable.

In the present invention, as long as the molecular weight of the polyester resin is within the above range, a substantially unoriented unstretched film or a molecularly oriented biaxially stretched film can be used. However, when at least the polyester resin layer on the inner surface side, preferably both resin layers are substantially unstretched, a can lid excellent in adhesion to a metal substrate and further excellent in workability can be obtained. There are advantages.
Furthermore, when an unstretched film is applied to a lid metal material in the form of an extrusion coat, the cost of film formation and stretching is reduced as compared with the case of using a stretched film, and the metal substrate is covered with Since the direct melt extrusion coating is performed, the productivity of the can lid is excellent, and further, there is an advantage that there is no emission of paint and the like, so that it is environmentally compatible.

As already pointed out, in forming the easily openable can lid, a score is provided so as to reach the middle of the metal plate in the thickness direction to divide the opening portion, and the opening portion or a portion adjacent thereto is defined. Severe processing such as forming a rivet on the lid plate itself and fixing the pull tab with this rivet is performed, but even during these processing, at least the polyester resin layer on the inner surface side also causes coating defects such as cracks and pinholes It is important that they do not cause adhesion defects such as peeling and blisters between the metal substrate and the metal substrate. In the case of a can lid with a substantially unstretched polyester inner layer, the thickness of the sheet was reduced in order to save metal materials, and even if the degree of processing became more severe, the above-mentioned coating defects and adhesion There is an advantage that defects are unlikely to occur.

In the laminated lid of the present invention, it is determined that the in-plane birefringence (Δn) of the inner polyester resin layer at the initial opening is suppressed to 0.020 or less. It is preferable in preventing lamination. As already pointed out,
The initial opening portion of the lid often overlaps with a portion subjected to thinning processing, such as around the rivet processing portion, and when internal strain remains in the polyester resin inner layer of this portion,
It was found that delamination was likely to occur. In the present invention, delamination of the inner polyester resin layer in the initial opening portion is reduced by relaxing internal strain such that the in-plane birefringence (Δn) of the inner polyester resin layer in the initial opening portion becomes 0.020 or less. It is possible to improve the opening of the lid.

The laminate lid of the present invention is manufactured by subjecting a laminate having a polyester resin layer provided on at least one surface of an aluminum plate or a steel plate to a heat treatment at least for the resin layer near the opening after scoring. Can be. It is important that the heat treatment of the resin layer in the vicinity of the opening is performed after the score processing. If the heat treatment is performed before the score processing, corrosion tends to occur in the score processed part, and no heat treatment was performed. In such a case, bag-like peeling is likely to occur in the score processing portion at the time of opening. According to the present invention, the heat treatment can alleviate the internal strain of the resin layer remaining after the processing and prevent the delamination of the resin coating which is likely to occur at the time of opening. Further, by this heat treatment, the adhesiveness of the resin inner surface layer around the score-processed portion can be restored, and thereby the corrosion resistance around the score-processed portion can be improved. Furthermore, by this heat treatment, the elongation of the inner resin layer is reduced, and the occurrence of phasoring is suppressed.
The score cut can be made favorable.

[Metal Material] In the present invention, any metal material conventionally used for easy-open lids such as various aluminum materials and various steel plates can be used as the metal material.

As the aluminum material, for example, pure aluminum or an alloy of aluminum and another alloy, particularly an aluminum alloy containing a small amount of magnesium, manganese or the like is used.

A normal aluminum raw material is electrochemically lower than steel, and when both metals coexist in an electrolyte system, aluminum corrosion proceeds. From this point of view,
In the present invention, Cu 0 to 0.8%, Mg 0
2.8%, Mn 0-1.5%, Fe 0-0.5%,
By using an aluminum alloy containing Si 0 to 0.5% (% is based on weight) as the aluminum material, corrosion in the system can be effectively prevented. That is, C contained as an alloy component
It is desirable that u is in the range of 0% to 0.8%, particularly 0.05 to 0.4% from the viewpoint of corrosion resistance. This Cu acts to bring the aluminum material to an electrochemically noble state, so that corrosion of the steel-aluminum system is more effectively prevented. Mg is preferably in the range of 0 to 2.8% from the viewpoint of corrosion resistance. If it exceeds 2.8%, pitting is likely to occur when coupled with steel. Mn is desirably 0% to 1.5% from the viewpoint of workability. If it exceeds 1.5%, processing such as rivet processing becomes difficult. Of course,
In the case of aluminum, there is no particular limitation.

Although the thickness of the aluminum material varies depending on the size of the lid and the like, it is generally 0.20 to 0.50 mm,
In particular, it is preferably in the range of 0.23 to 0.30 mm. From the viewpoint of the adhesion of the inner surface material to the aluminum material and the corrosion resistance, it is generally desirable to form a surface treatment film on the surface of the aluminum material. Preferable examples of the surface treatment include a chromate treatment, a zirconium treatment, a phosphoric acid treatment, a polyacrylic acid treatment, an anodic oxidation treatment and the like. As an example of the formation of the surface treatment film, the formation of the chromate treatment film is as follows.
After a known means, for example, aluminum material is degreased and slightly etched with caustic soda, 4 g of CrO ₃
/ L, 12 g / L of H ₃ PO ₄ , 0.65 g / L of F, and the remainder is carried out by a chemical treatment of immersion in a treatment liquid such as water. The thickness of the chromate-treated film is 5 to 50 mg / dm ² , particularly 10
It is more preferable that it is within the range of 35 to 35 mg / dm ² from the viewpoint of adhesion.

On the other hand, various steel sheets include a chromate surface-treated steel sheet, particularly an electrolytic chromic acid-treated steel sheet, a chromate-treated nickel-plated steel sheet, a chromate-treated iron / tin alloy-plated steel sheet, a chromate-treated tin-nickel alloy-plated steel sheet, and a chromate-treated iron / steel sheet. Tin-nickel alloy plated steel sheets, chromate treated aluminum plated steel sheets, chromate treated tinplates and the like are used. The thickness of the steel sheet substrate is determined by a balance between the pressure deformation property, the workability, and the easy opening property, and is generally 0.1 mm.
To 0.4 mm, especially 0.12 to 0.35 mm.

Of these, electrolytic chromic acid-treated steel sheets are preferred, which comprise a metal chromium layer on a steel sheet substrate and a non-metallic chromium layer thereon. The thickness of the metal chromium layer is determined by the balance between corrosion resistance and workability, and the amount is preferably in the range of 30 to 300 mg / m ² , particularly preferably 50 to 250 mg / m ² . The thickness of the non-metallic chromium layer is related to coating film adhesion and adhesive peel strength, and is expressed as chromium amount of 4 to 40 mg / m ² , particularly 7 to 30 mg / m ² .
It is desirably in the range of ² .

[Polyester Resin Layer] The polyester resin is derived from an alcohol component mainly composed of ethylene glycol or butylene glycol and an acid component such as an aromatic dibasic acid such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid. Thermoplastic polyester. Of course, these polyester resins must have a molecular weight in the range described above.

As the polyester, polyethylene terephthalate itself can be used under limited laminating conditions. However, it is desirable to lower the maximum crystallinity that the film can reach from the viewpoint of impact resistance and processability. For this purpose, it is preferable to introduce a copolymer ester unit other than ethylene terephthalate into the polyester. It has a melting point of 18 based on ethylene terephthalate units or butylene terephthalate units and containing a small amount of other ester units.
It is particularly preferred to use a copolymerized polyester at 0 to 252 ° C. The melting point of homopolyethylene terephthalate is generally from 255 to 265 ° C.

Generally, at least 70 mol%, especially at least 75 mol%, of the dibasic acid component in the copolyester is composed of the terephthalic acid component, and at least 70 mol%, especially at least 75 mol%, of the diol component is ethylene glycol or butylene glycol. Consisting of 1 to 30 mol% of the dibasic acid component,
In particular, it is preferable that 5 to 25 mol% is composed of a dibasic acid component other than terephthalic acid.

Examples of dibasic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; succinic acid, adipic acid, sebacic acid, dodecane One or a combination of two or more aliphatic dicarboxylic acids such as dionic acid, and diol components other than ethylene glycol or butylene glycol include propylene glycol, diethylene glycol,
One or more of 1,6-hexylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A and the like can be mentioned. Of course, the combination of these comonomers must be such that the melting point of the copolyester is within the above range.

In order to improve the melt flow characteristics at the time of molding, the polyester is at least one selected from the group consisting of trifunctional or higher polybasic acids and polyhydric alcohols.
Various branching or crosslinking components can be included. These branched or crosslinked components are present in an amount of not more than 3.0 mol%, preferably from 0.05 to 3.0 mol%.

Examples of trifunctional or higher polybasic acids and polyhydric alcohols include trimellitic acid, pyromellitic acid, hemimellitic acid, 1,1,2,2-ethanetetracarboxylic acid,
1,1,2-ethanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, biphenyl-3,4,3 ′, 4′-
Polybasic acids such as tetracarboxylic acid, pentaerythritol, glycerol, trimethylolpropane,
6-hexanetriol, sorbitol, 1,1,4,
Polyhydric alcohols such as 4-tetrakis (hydroxymethyl) cyclohexane are exemplified.

Polyester resins suitable for the lamination lid include polyethylene terephthalate / isophthalate containing 5 to 25 mol% of an isophthalic acid component, and polyethylene / cyclohexylene dimethylene terephthalate containing 1 to 10 mol% of a cyclohexane dimethanol component. Is mentioned.

The polyester resin layer used in the present invention may be formed of the polyester or copolyester alone, or a blend of two or more of polyester or copolyester, or a polyester or copolyester and another thermoplastic resin. May be formed from a blend with As a blend of two or more polyesters or copolyesters, polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate, polyethylene /
Examples include a combination of two or more cyclohexylene dimethylene terephthalates, but are not limited to this example.

Other thermoplastic resins that can be blended in the polyester include ethylene polymers, thermoplastic elastomers, polyarylates, polycarbonates, and the like. By further containing at least one of these modified resin components, high-temperature wet heat resistance and impact resistance can be further improved. The modified resin component is generally used in an amount of up to 50 parts by weight, particularly preferably in an amount of 5 to 35 parts by weight, per 100 parts by weight of the polyester.

Examples of the ethylene polymer include low-, medium-, or high-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-propylene copolymer, and ethylene-butene-1 copolymer. , An ethylene-propylene-butene-1 copolymer, an ethylene-vinyl acetate copolymer, an ion-crosslinked olefin copolymer (ionomer), an ethylene-acrylate copolymer, and an alkyl ester thereof. Of these, ionomers are preferred, and as the base polymer of the ionomer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester- (meth) acrylic acid copolymer, ion As a seed,
Na, K, Zn and the like are used. Examples of the thermoplastic elastomer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, and hydrogenated styrene-isoprene-
A styrene block copolymer or the like is used.

The polyarylate is defined as a polyester derived from a dihydric phenol and a dibasic acid. As the dihydric phenol, bisphenols include 2,2'-bis (4-hydroxyphenyl) propane ( Bisphenol A), 2,2′-bis (4-hydroxyphenyl) butane (bisphenol B), 1,1 ′
-Bis (4-hydroxyphenyl) ethane, bis (4-
(Hydroxyphenyl) methane (bisphenol F), 4
-Hydroxyphenyl ether, p- (4-hydroxy) phenol and the like are used, but bisphenol A and bisphenol B are preferred. As dibasic acids,
Terephthalic acid, isophthalic acid, 2,2- (4-carboxyphenyl) propane, 4,4′-dicarboxydiphenyl ether, 4,4′-dicarboxybenzophenone and the like are used. The polyarylate may be a homopolymer derived from the above monomer component or a copolymer. Further, a copolymer of an ester unit derived from an aliphatic glycol and a dibasic acid may be used as long as the essence is not impaired. These polyarylates are
Unitika U-Series or AX Series of U-Polymer, UCC ArdelD-100, Bayer APE, Hoechst Durel, DuPont
Available from Arylon of Kaneka Corporation and NAP resin of Kaneka Chemical Corporation.

Polycarbonate is a carbonate resin derived from bicyclic dihydric phenols and phosgene, and is characterized by having a high glass transition point and heat resistance. As polycarbonate, bisphenols,
For example, 2,2'-bis (4-hydroxyphenyl)
Propane (bisphenol A), 2,2'-bis (4-
Hydroxyphenyl) butane (bisphenol B),
1,1′-bis (4-hydroxyphenyl) ethane, bis (4-hydroxyphenyl) methane (bisphenol F), 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) ) Cyclopentane, 1,1-bis (4-hydroxyphenyl) -1-phenylmethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,2-bis (4-hydroxyphenyl) ethane Preferred are polycarbonates derived from such.

The polyester resin layer used in the present invention may be a single-layer resin layer or a multi-layer resin layer formed by simultaneous extrusion. When a multilayer polyester resin layer is used, a polyester resin having a composition excellent in adhesion to the metal substrate is selected on the base layer, that is, the side in contact with the metal substrate, and the surface layer has a content resistance property, that is, a non-extraction property and a non-existence of flavor components. This is advantageous because a polyester resin having a composition excellent in adsorptivity can be selected.

Examples of the multilayer polyester resin layer include polyethylene terephthalate / polyethylene terephthalate / isophthalate, polyethylene terephthalate / polyethylene / cyclohexylene dimethylene terephthalate, and polyethylene having a low isophthalate content. Examples include terephthalate / isophthalate / polyethylene terephthalate / isophthalate having a large content of isophthalate, and a blend of polyethylene terephthalate / isophthalate / polybutylene terephthalate / adipate and polyethylene terephthalate / isophthalate, but are not limited to the above examples. The thickness ratio of the surface layer to the lower layer is desirably in the range of 5:95 to 95: 5.

The polyester resin layer contains known resin compounding agents such as antiblocking agents such as amorphous silica, inorganic fillers, various antistatic agents, lubricants, antioxidants, and ultraviolet absorbers. Can be formulated according to the formula

The thickness of the polyester resin layer is desirably in the range of generally 3 to 50 μm, particularly preferably 3 to 40 μm. That is, when the thickness is less than the above range, the corrosion resistance becomes insufficient, and when the thickness is more than the above range, a problem tends to occur in workability.

[Laminated Plate] FIG. 1 shows an example of a cross-sectional structure of a laminated plate used for manufacturing the laminated lid of the present invention.
The laminate plate 1 includes a polyester resin layer 3 provided on the side of the metal base 2 which will be the inner surface of the container lid, and an outer surface protective layer 4 provided on the side which will be the outer surface of the container lid.
Although not generally required, a primer layer (not shown) may be provided between the polyester resin layer 3 and the metal substrate 2.

As the outer protective layer 4, a polyester resin layer is used in the same manner as the inner protective layer. This protective layer is formed of a thermosetting resin paint such as a phenol-formaldehyde resin, a furan-formaldehyde resin, a xylene-formaldehyde resin. Resin, ketone-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin, alkyd resin, unsaturated polyester resin, epoxy resin, bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, oily resin, or Is formed of a thermoplastic resin paint, for example, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-maleic acid copolymer, a vinyl chloride-maleic acid-vinyl acetate copolymer, an acrylic polymer, a saturated polyester resin, or the like. You may. These resin coatings may be used alone or in combination of two or more. Further, it can be provided in two layers of an undercoat and a topcoat. The thickness of the outer surface protective layer 4 is not particularly limited, but is generally preferably set to a thickness of 0.5 to 20 μm.

In FIG. 2 showing another example of the cross-sectional structure of the laminated plate used for manufacturing the laminated lid of the present invention, the laminated plate 1 is made of a polyester resin applied to the metal substrate 2 on the side to be the inner surface of the container lid. It is the same as that of FIG. 1 in that it comprises a layer 3 and an outer protective layer 4 provided on the side to be the outer surface of the container lid, except that the polyester resin layer 3 comprises a polyester resin surface layer 3a and a polyester resin lower layer 3b. It has a laminated structure. As described above, a polyester resin surface layer 3a having excellent content resistance is used, while a polyester resin lower layer 3b having excellent adhesion to a metal substrate is used.

The resin-metal laminate plate used in the present invention can be produced by extrusion-coating a polyester resin in a molten state on a metal substrate and bonding them by heat. That is, after the polyester resin is melt-kneaded by an extruder, it is extruded into a thin film form from a T-die, and the extruded molten resin film is passed between a pair of laminating rolls together with a metal substrate to be pressed and integrated under cooling, and then rapidly cooled I do. When extrusion-coating a multi-layer polyester resin layer, use an extruder for the surface resin and an extruder for the lower resin, combine the resin flows from each extruder in multiple multilayer dies, Extrusion coating may be performed as in the case of resin. Also,
By vertically passing a metal substrate between a pair of laminating rolls and supplying a molten resin web to both sides thereof, a polyester resin coating layer can be formed on both surfaces of the metal substrate.

The production of the resin-metal laminate plate by the extrusion coating method is specifically performed as follows. If necessary, the metal plate is preheated by a heating device and supplied to a nip position between a pair of laminate rolls. On the other hand, the polyester resin is extruded in the form of a thin film through a die head of an extruder, supplied between a laminating roll and a metal plate, and pressed against the metal plate by the laminating roll. The laminating roll is maintained at a constant temperature, and a thin film made of a thermoplastic resin such as polyester is pressure-bonded to a metal plate to thermally bond the two, and is cooled from both sides to obtain a laminate. In general, the formed laminate is further guided to a cooling water tank or the like,
Rapid cooling is performed to prevent thermal crystallization.

In this extrusion coating method, the polyester resin layer has a low crystallinity level and a difference between the amorphous density of the polyester resin layer of 0.04% by selection of the resin composition and rapid cooling by a roll or a cooling bath.
Since it is suppressed to 5 or less, sufficient workability for subsequent button processing or rivet processing is guaranteed.
Needless to say, the quenching operation is not limited to the above example, and the cooling water may be sprayed on the formed laminated plate to rapidly cool the laminated plate.

The heat bonding of the polyester resin to the metal substrate is performed by the amount of heat of the molten resin layer and the amount of heat of the metal plate. The heating temperature (T ₁ ) of the metal plate is generally from 90 ° C. to 290 ° C., particularly from 100 ° C. to 280 ° C., while the temperature of the laminating roll is 10 ° C.
A range of from about 150C to about 150C is suitable.

The resin-metal laminate plate used in the present invention can also be manufactured by heat-bonding a previously formed unstretched polyester resin film to a metal substrate. In this case, a polyester resin is formed into a film by a T-die method to obtain a supercooled unoriented cast film. Using this unoriented film, it is possible to produce a laminate by heat bonding as described above.

According to the present invention, the metal substrate and the polyester resin layer can be firmly adhered to each other without providing a special primer layer between the metal substrate and the polyester resin layer, as shown in Examples described later. Is possible. For this reason, according to the present invention, conventional processes such as painting and baking of an adhesion primer are omitted, and there is no scattering of solvent or paint mist into a work environment or generation of paint exhaust gas accompanying paint baking, and environmental compatibility. Is excellent.

Of course, it is not generally necessary, but if desired, an adhesive primer can be provided between the resin layer and the metal material. Such an adhesive primer is excellent in both the metal material and the polyester resin layer. It shows adhesiveness. 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, the phenol resin and the epoxy resin are in a weight ratio of 50:50 to 5:95, particularly 40:50.
It is a paint contained in a weight ratio of 60 to 10:90. The adhesive primer layer is generally preferably provided with a thickness of 0.3 to 5 μm. The adhesive primer layer may be provided on a metal material in advance, or when a film is used, may be provided on a film in advance.

[Easily Opening Laminate Lid and Production Thereof] In FIG. 3 showing the upper surface of the easy-open container lid of the present invention and FIG. 5 showing an enlarged cross section, this lid 10 is made of the laminated plate of FIG. An annular rim (counter sink) 1 which is formed and is to be fitted to the inner surface of the can body side surface 1
1, a sealing groove 12 is provided on the outer peripheral side, and a score 14 that defines a portion 13 to be opened is provided inside the annular rim portion 11. A rivet 15 formed by projecting a lid material toward the outer surface of the can lid is formed near the outside of the portion (opening section) 13 to be opened, and a tab 16 for opening is formed on the rivet 15. It is fixed as shown below by riveting. That is, the opening tab 16 has an opening end 17 by pushing and tearing at one end and a holding ring 18 at the other end, and has a fulcrum portion 19 fixed by the rivet 15 near the opening end 17. The portion 13 to be opened is generally surrounded by the score 14, but a part is connected to the lid 10 without passing through the score 14 to the lid material. In the sealing groove 12 described above, a compound (sealant) 2 of a rubber composition for sealing is used.
0 is lined to provide a seal with the can body flange.

At the time of opening, the ring 18 of the opening tab 16 is held and lifted upward. As a result, the opening tip 17 of the opening tab 16 is pushed downward, and a part of the score 14 starts to be sheared. Next, by holding the ring 18 and pulling it upward, the remaining portion of the score 14 is broken and opening is easily performed. In this type of lid 10, the tab 16 does not come off the lid together with the opening 13 and remains on the lid.

The lid in the above specific example is a so-called stay-on-tab, but it is of course applicable to a fully open easy-open lid. In FIG. 4 showing an example of the full-open easy-open lid, a score 14 for partitioning a portion 13 to be opened is provided on the entire inside of the annular rim portion 11. The part to be opened (opening partition part) 13
A rivet 15 formed by projecting a lid material to the outer surface side of the can lid is formed in the vicinity of the inside of the tub, and the opening tab 1 is formed.
6 is fixed by riveting the rivet 15. As in the case of FIG. 3, the opening tab 16 has an opening tip 17 at one end by tearing and a holding ring 18 at the other end, and is fixed by the rivet 15 near the opening tip 17. An arc-shaped slit 20 is formed around the rivet 15 so that the tab 16 can be lifted above the rivet 15.
7, a fulcrum portion 19 exists. In this lid, the part 13 to be opened is completely surrounded by the score 14. Upon opening, the ring 18 of the opening tab 16 is held and lifted upward. As a result, the opening tip 17 of the opening tab 16 is pushed downward, and a part of the score 14 starts to be sheared. Next, by holding the ring 18 and pulling it upward, the remaining portion of the score 14 is broken and opening is easily performed. Lid 10 of this type
In this case, the tab 16 is completely separated from the lid together with the opening portion 13, and an opening over substantially the entire surface of the lid is made.

The molding of the easy-open lid of the present invention is carried out by means known per se except for using the above-mentioned laminated body. To explain this step, first, in a press forming step, the laminate sheet is punched into a disk shape and formed into a desired lid shape.

Next, in a score marking step, the score is marked using a score die so that the score reaches the middle of the metal material from the outer surface side of the lid. The residual thickness (t2) of the metal material in the score is preferably such that t2 / t1 × 100 is 10 to 50% and t2 is 20 to 150 μm with respect to the original thickness (t1) of the metal material. Further, it is important that the bottom width (d) of the score be 75 μm or less, particularly 50 μm or less, in order to prevent the occurrence of scratches on the film layer.

In the rivet forming step, a rivet projecting from the outer surface is formed in the opening section defined by the score using a rivet forming die, and in the tab attaching step, the opening tab is fitted to the rivet, and the rivet projecting section is formed. And fix the tab. Instead of the rivet forming step, in the case of an adhesive tab, an adhesive such as a nylon-based adhesive tape is applied to the opening or tab, and the tab and the opening are thermally bonded in the tab attaching step.

[Heat Treatment] In the present invention, the polyester resin layer near the opening is heat-treated after scoring the laminated lid formed as described above. The purpose of this heat treatment is, as already pointed out, to remove the residual strain in the vicinity of the scored portion and to restore the adhesion of the inner resin layer. Further, it is also possible to reduce the elongation of the inner resin layer near the scored portion by this heat treatment and suppress the occurrence of feathering.

The temperature of the heat treatment depends on the composition of the polyester resin layer to be used and the treatment time, but it is lower than the glass transition point, and more preferably, the temperature is Tg + 50 ° C. or higher. Suitable for the purpose of adhesion recovery. When the elongation of the inner resin layer is to be reduced at the same time, the temperature should be equal to or higher than the crystal melting range of the resin layer. At this temperature condition, the processing time is short, generally 0.01 to 60 seconds,
In particular, 0.01 to 10 seconds is sufficient.

The heat treatment can be performed using any heating means known per se, for example, oven heating, infrared heater, high frequency induction heating, laser irradiation and the like.

Finally, in the lining step, a sealing compound is lined and applied to the sealing groove of the lid through a nozzle and dried to form a sealant layer. To explain the double winding process of the lid and the can body, the flange of the can body member and the sealing groove of the easy-open lid are fitted together, and the groove is formed around the flange using the primary winding roll. Make primary winding. Next, in the secondary winding step, the flange portion is further wound along the can body side wall to form a can body.

As the can body member, a seam made of an adhesive (nylon-based adhesive) or a seam made by welding is provided on the side surface, and a tenin-free steel (TFS, electrolytic chromic steel sheet ) Or a so-called TFS or aluminum can body for a so-called two-piece can formed by drawing or deep drawing. In addition, the lid of the present invention is formed from a tin-plated steel plate (tinplate) and formed by a can body for a three-piece can having a seam by soldering or welding, or by drawing and ironing, deep drawing, or impact extrusion. The present invention is equally applicable to so-called tin-made seamless can bodies.

[0069]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples. The measurement in the examples was performed as follows.

Evaluation and Measurement Methods (1) Molecular Weight Measurement High Speed GPC System HLC-8120GP
C (manufactured by Tosoh Corporation) and TSK-G after the guard column.
The column configuration was such that two EL SuperHM-H (manufactured by Tosoh Corporation) were connected. UV-detector UV-
The measurement wavelength was 254 nm using 8020 (manufactured by Tosoh Corporation). The measurement temperature condition is 40 ° C. The resin layer was isolated from the can lid by an ordinary method, about 5 mg was dissolved in 0.3 ml of hexafluoroisopropanol (HFIP), and 4 ml of chloroform was added to prepare a sample solution. Chloroform was used as an eluent at a flow rate of 0.6 ml / min. From the obtained elution curve, a weight average molecular weight (Mw) was determined by a conventional method. (2) Melting point (Tm), glass transition temperature (Tg), crystallization peak area (ΔH _Tcc ) Differential thermal scanning calorimeter DSC7 (Perkin Elmer)
Was used. The resin layer is isolated from the can lid by an ordinary method, and about 6.
5 mg was heated at a rate of 10 ° C./min to a temperature 50 ° C. higher than the melting point of the resin under a nitrogen stream and measured. The temperature at the maximum height of the endothermic peak based on the crystal melting was defined as Tm, and the specific heat change point based on the glass transition was defined as Tg. The exothermic peak area due to crystallization was _defined as ΔH _Tcc . In a multilayer resin layer composed of different composition resins, the measurement was performed without separating each layer. (3) Birefringence The resin layer was isolated from the can lid by an ordinary method, the retardation was measured from the surface with a polarizing microscope, and the birefringence was calculated together with the thickness obtained by a contact-type film thickness meter. FIG. 7 shows the measurement positions. (4) Evaluation of opening property, evaluation of feathering, evaluation of delamination The sample lid was immersed in water at 40 ° C. for 10 minutes, and then
A tab is fixed in water at 0 ° C. with a hook, and the lid is opened at a rate of 7.5 degrees per second around a straight line in the panel plane passing through the rivet portion in a direction simulating a normal opening operation. . The periphery of the opening was observed under magnification with a microscope, and the maximum length of feathering measured from the opening and the maximum length of the delamination range were measured and evaluated according to the following criteria. As an overall evaluation, the quality of the opening property that can withstand the commercialization was good, and the thing that did not withstand the commercialization was defined as the poor opening property. Evaluation criteria Feathering resistance: ◎ (not recognized), ○ (0.2 m
m), (less than 3.0 mm), × (3.0 mm or more). Delamination resistance: （(not recognized), （(less than 0.5 mm), Δ (less than 5.0 mm), × (more than 5.0 mm). (5) Evaluation of corrosion resistance After filling the empty can with the following corrosive liquid, the sample lid was tightly wound. After storage at 50 ° C. for one week under an inverted condition in which the lid comes into contact with the corrosive liquid, the body of the can was cut open and the inner surface state of the lid was evaluated according to the following criteria. Corrosion liquid: 5% salt solution / 5% citric acid aqueous solution Evaluation criteria ○ (corrosion not observed), × (corrosion observed).

[Example 1] Metal material Aluminum alloy A5182H1 having a thickness of 0.235 mm
Ninth, a chromic acid / phosphoric acid surface treatment was performed to obtain a metal material. Resin material The resin composition shown in Table 1 was used. The Mw of the raw material pellet was 75,000. Production method of laminated metal material On the aluminum alloy plate heated to 250 ° C, the resin material was supplied to a 45 mmφ single screw extruder equipped with an extrusion lamination facility, and the temperature of the barrel and T-die was set at 250 ° C. The resin thickness on the outer surface of the lid is 3μ
m, the inner and outer surfaces were simultaneously melt-extruded so that the resin thickness on the inner surface side of the lid was 12 μm, and immediately cooled with water to obtain a laminated metal material. Method of manufacturing lid For the above laminated metal material, a lid having a diameter of 68.7 mm was punched out, and a partial opening type score processing (width 22 mm, remaining score thickness 110 μm, score width 20 μm), rivet processing and opening were performed from the outside of the lid. The tab was attached. Thereafter, a heat treatment was performed in an oven at 231 ° C. for 5 seconds to form an SOT lid. Regarding the obtained laminated lid, under the above conditions, the molecular weight, melting point (Tm), glass transition temperature (Tg), crystallization peak area (△)
H _Tcc ) and birefringence were measured, and the results are shown in Table 1. The opening property was evaluated under the above conditions using the obtained laminate lid. The aperture is good, no feathering or delamination is observed,
The periphery of the opening was in a good state. Further, when the corrosion resistance was evaluated under the above conditions, no corrosion was observed on the inner surface of the can lid, and the condition was good.

Example 2 The heat treatment after the lid was made was carried out at 240 ° C.
-The procedure was the same as in Example 1 except that the duration was 5 seconds. This is an example in which the molecular weight of Example 1 was changed. The molecular weight, melting point (Tm), glass transition temperature (T
g), the crystallization peak area (ΔH _Tcc ), and the measurement results of birefringence are shown in Table 1. The opening was good, no feathering or delamination was observed, and the periphery of the opening was in a good state. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Example 3 The heat treatment after lid production was performed at 210 ° C.
-The procedure was the same as in Example 1 except that the duration was 5 seconds. This is an example in which the molecular weight of Example 1 was changed. The molecular weight, melting point (Tm), glass transition temperature (T
g), the crystallization peak area (ΔH _Tcc ), and the measurement results of birefringence are shown in Table 1. The opening was good, the feathering and delamination were 0.1 mm at the maximum, and the periphery of the opening was in a good state without any practical problem. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Example 4 After the heat treatment after the lid production, 16
Example 1 was repeated except that the crystallization treatment was performed at 0 ° C. for 180 seconds. This is an example in which the degree of crystallization in Example 1 is changed. The molecular weight and melting point (T
m), glass transition temperature (Tg), crystallization peak area (Δ
Table 1 shows the measurement results of H _Tcc ) and birefringence. Example 1
As compared with, the crystallization peak area is reduced and crystallization is progressing. On the other hand, there was no change in the molecular weight. The opening was good, no feathering or delamination was observed, and the periphery of the opening was in a good state. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Example 5 The procedure of Example 1 was repeated except that the resin composition was as shown in Table 1 and that the heat treatment after lid production was performed at 251 ° C. for 5 seconds. This is an example in which the resin composition of Example 1 was changed. The Mw of the raw material pellet was 67000. The molecular weight and melting point (T
m), glass transition temperature (Tg), crystallization peak area (Δ
Table 1 shows the measurement results of H _Tcc ) and birefringence. The opening was good, no feathering or delamination was observed, and the periphery of the opening was in a good state. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Example 6 The procedure of Example 1 was repeated except that the resin composition was as shown in Table 1 and that the heat treatment after lid production was 231 ° C. for 15 seconds. This is an example in which the resin composition of Example 1 was changed. The Mw of the raw material pellet was 92,000. The molecular weight and melting point (T
m), glass transition temperature (Tg), crystallization peak area (Δ
Table 1 shows the measurement results of H _Tcc ) and birefringence. The opening property was good, feathering and delamination were not readily observed, and the periphery of the opening was in a good state. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Example 7 A biaxially stretched polyester film having the resin composition shown in Table 1 was thermocompression-bonded to the aluminum alloy plate heated to 225 ° C., and immediately cooled with water to obtain a laminated metal material. It was the same as in Example 1. This is an example in which Example 1 is changed from extrusion lamination to biaxially stretched film lamination. Table 1 shows the measured results of molecular weight, melting point (Tm), glass transition temperature (Tg), crystallization peak area (ΔH _Tcc ), and birefringence of the obtained laminated lid.
Shown in The opening was good, no feathering or delamination was observed, and the periphery of the opening was in a good state. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

[Embodiment 8] Heat treatment 2 on laminated metal material
Example 1 except that a heat treatment was performed at 31 ° C. for 3 seconds, and then the lid was made, and the heat treatment after the lid was made at 231 ° C. for 3 seconds.
Same as. This is an example in which the birefringence of the initial opening of the first embodiment is changed. Table 1 shows the measurement results of molecular weight, melting point (Tm), glass transition temperature (Tg), crystallization peak area (ΔH _Tcc ), and birefringence of the obtained laminate lid. The opening was good, and no feathering was observed, but 0.2 mm of delamination occurred in the initial opening. The periphery of the opening was in a good state without any practical problems. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

[Embodiment 9] Multi-manifold type 2
Using the layer T die, the inner surface side resin layer was
It was the same as Example 1 except that the layer structure was adopted. Example 1
It is an example of multilayering of the resin layer. The molecular weight, melting point (Tm), glass transition temperature (T
g), the crystallization peak area (ΔH _Tcc ), and the measurement results of birefringence are shown in Table 1. The opening was good, no feathering or delamination was observed, and the periphery of the opening was in a good state. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Example 10 Metallic Material Aluminum alloy A5052H1 having a thickness of 0.250 mm
Ninth, a chromic acid / phosphoric acid surface treatment was performed to obtain a metal material. Resin material The resin composition shown in Table 1 was used. The Mw of the raw material pellet was 75,000. Production method of laminated metal material On the aluminum alloy plate heated to 250 ° C, the resin material was supplied to a 45 mmφ single screw extruder equipped with an extrusion lamination facility, and the temperature of the barrel and T-die was set at 250 ° C. The resin thickness on the outer surface of the lid is 3μ
m, the inner and outer surfaces were simultaneously melt-extruded so that the resin thickness on the inner surface side of the lid was 15 μm, and immediately cooled with water to obtain a laminated metal material. Method of Manufacturing Lid For the above laminated metal material, a 90.5 mm diameter lid (commonly referred to as 301 diameter) was punched out, and a partial opening type score processing (score remaining thickness 110 μm, score width 25 μm), rivet processing and An opening tab was attached. Thereafter, a heat treatment was performed in an oven at 231 ° C. for 5 seconds to form a fully open lid. With respect to the obtained laminated lid, the molecular weight and the melting point (T
m), glass transition temperature (Tg), crystallization peak area (Δ
H _Tcc ) and birefringence were measured, and the results are shown in Table 1. The opening property was evaluated under the above conditions using the obtained laminate lid. The aperture is good, no feathering or delamination is observed,
The periphery of the opening was in a good state. Further, when the corrosion resistance was evaluated under the above conditions, no corrosion was observed on the inner surface of the can lid, and the condition was good.

[Comparative Example 1] Heat treatment after lid production was performed at 200 ° C.
-The procedure was the same as in Example 1 except that the time was 2 seconds. This is an example in which the molecular weight of Example 1 was changed. The molecular weight, melting point (Tm), glass transition temperature (T
g), crystallization peak area (ΔH _Tcc ), and measurement results of birefringence are shown in Table 1. As a result of the evaluation of the opening property, poor opening occurred. Due to the extension of the resin, the resin layer was not cut in about half of the entire length of the opening. In addition, delamination with a maximum width of 4 mm occurred. On the other hand, as a result of the evaluation of corrosion resistance,
No corrosion was observed on the inner surface of the can lid, and the condition was good.

[Comparative Example 2] The heat treatment after lid production was performed at 200 ° C.
Example 2 was repeated except that the crystallization process was performed at 160 ° C. for 180 seconds. Example 1
This is an example in which the molecular weight and the degree of crystallization were changed. Table 1 shows the measurement results of molecular weight, melting point (Tm), glass transition temperature (Tg), crystallization peak area (ΔH _Tcc ), and birefringence of the obtained laminate lid. As a result of the evaluation of the opening property, poor opening occurred. Due to the extension of the resin, the resin layer was not cut in about one third of the entire length of the opening. In addition, the maximum is 3.5
Delamination of mm width also occurred. On the other hand, as a result of the evaluation of the corrosion resistance, no corrosion was recognized on the inner surface of the can lid, which was in a good state.

[Comparative Example 3] Heat treatment after lid production was performed at 245 ° C.
-The procedure was the same as in Example 1 except that the duration was 5 seconds. This is an example in which the molecular weight of Example 1 was changed. The molecular weight, melting point (Tm), glass transition temperature (T
g), the crystallization peak area (ΔH _Tcc ), and the measurement results of birefringence are shown in Table 1. The opening was good, no feathering or delamination was observed, and the periphery of the opening was in a good state. On the other hand, as a result of the evaluation of the corrosion resistance, corrosion was found on the inner surface of the can lid at the boundary between the central panel portion and the peripheral bead portion.

[Comparative Example 4] Heat treatment 2 on a laminated metal material
A heat treatment was performed at 31 ° C. for 5 seconds, a lid was formed thereafter, and the process was performed in the same manner as in Example 1 except that no heat treatment was performed after the lid was formed. This is an example in which the birefringence of the initial opening of the first embodiment is changed.
The molecular weight, melting point (Tm), and
Glass transition temperature (Tg), crystallization peak area (ΔH
Table 1 shows the measurement results of _Tcc ) and birefringence. As a result of the evaluation of the opening property, feathering of 1.5 mm mainly occurred in the initial opening portion. Delamination with a maximum width of 3 mm occurred so as to overlap the portion where the feathering occurred. In addition, as a result of the evaluation of the corrosion resistance, no corrosion was observed on the inner surface of the can lid, which was in a good state.

Comparative Example 5 The procedure of Example 1 was repeated except that the resin composition was as shown in Table 1 and the raw material pellets had an Mw of 51,000, and that no heat treatment was performed after the lid was made. This is an example in which the molecular weight of the raw material resin of Example 1 was changed. The molecular weight, melting point (Tm), glass transition temperature (Tg), crystallization peak area (△
Table 1 shows the measurement results of H _Tcc ) and birefringence. As a result of the evaluation of the opening property, poor opening occurred. Due to delamination and expansion of the resin layer, the resin layer was not cut over the entire circumference of the entire opening. Delamination is up to 17m
m. As a result of the evaluation of the corrosion resistance, corrosion occurred along the score portion.

[0086]

[Table 1] Inner surface resin composition Mw Tm Tg ΔH _Tcc Example 1 PET / IA12 45000 227 74 -23.0 Example 2 PET / IA12 26000 227 74 -25.0 Example 3 PET / IA12 69000 227 74 -20.3 Example 4 PET / IA12 45000 227 74 0.0 Example 5 Homo PET 37000 253 79.5 -10.3 Example 6 PET / CHDM5 50000 226 80.6 -27.7 Example 7 PET / IA12 48000 228 76 0.0 (stretched film) Example 8 PET / IA12 44000 227 74 Example 9 Surface PET / IA12 48000 Lower layer PET / CHDM5 Example 10 PET / IA12 45000 227 74 -23.5 Comparative Example 1 PET / IA12 73000 227 74 -20.5 Comparative Example 2 PET / IA12 73000 227 74 0.0 Comparative Example 3 PET / IA12 20000 227 74 -25.6 Comparative Example 4 PET / IA12 46000 227 74 Comparative Example 5 PET / IA12 48000 227 74 -24.0 Birefringence Opening Resistance Feathering Delamination Resistance Corrosion Resistance Example 10 Good ◎ ◎ ○ Example 20 Good ◎ ◎ ○ Example 30 good ○ ○ ○ Example 40 good ◎ ◎ ○ Example 5 0.017 good ◎ ◎ ○ Example 60 good ◎ ◎ ○ Example 7 0.002 good ◎ ◎ ○ Example 8 0.019 Good ◎ ○ ○ Example 9 0 Good ◎ ◎ ○ Example 100 Good ◎ ◎ ○ Comparative Example 1 Bad × △ ○ Comparative Example 2 Bad × △ ○ Comparative Example 30 Good ◎ ◎ × Compare Example 4 0.025 defective △ △ ○ Comparative Example 5 0.011 defective × × In the above table, the resin composition has the following meaning. PET: Polyethylene terephthalate PET / IA12: Polyethylene terephthalate / isophthalate PET / CHDM5: 12 mol% of isophthalate component Polyethylene cyclohexylene dimethylene terephthalate of 5 mol% of cyclohexane dimethanol component

[0087]

According to the present invention, in a resin laminated lid having a score, a polyester resin layer is provided at least on the inner surface side of the can, and the molecular weight of the polyester resin of the inner resin layer at a portion along the score is reduced. By setting it in the range of 25,000 to 70000, the opening property when cutting and opening the score by pushing the tip of the opening tab or tearing the opening part is improved, and the content resistance is also improved. Can be. Further, according to the present invention, it is not necessary to perform the correction coating after the lid production, and at the same time, it is possible to manufacture a laminated can lid having excellent opening properties, and it is also excellent in environmental conservation and has a large effect of improving the working environment. An excellent manufacturing method can be provided.

[Brief description of the drawings]

FIG. 1 is an enlarged conceptual diagram showing an example of a cross-sectional structure of a laminate used in the present invention.

FIG. 2 is an enlarged conceptual diagram showing another example of a cross-sectional structure of a laminate used in the present invention.

FIG. 3 is a top view of an example of the laminate lid of the present invention.

FIG. 4 is a top view of another example of the laminate lid of the present invention.

FIG. 5 is an enlarged sectional view of the laminate lid of FIG. 3 of the present invention.

FIG. 6 is a graph showing the relationship between the inner polyester resin molecular weight, the degree of crystallization, and the opening property.

FIG. 7 is a diagram showing a measurement site of birefringence.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] January 14, 2000 (2000.1.1)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

[0017]

According to the present invention, a resin laminated lid having a scored portion has a polyester resin layer at least on the inner surface side of the can lid , and a portion along the scored portion is provided. A laminated lid is provided, wherein the polyester resin of the inner resin layer has a molecular weight in the range of 25,000 to 70000. In the laminate lid of the present invention, 1. Among the polyester resin layers, at least one of the inner and outer surfaces of the can lid is substantially unstretched; In the initial opening portion, the in-plane birefringence Δ of the inner resin layer
N is preferably 0.020 or less. According to the present invention, a laminate having a polyester resin layer provided on at least one surface of an aluminum plate or a steel plate is subjected to a scoring process, and then at least the resin layer near the opening is heat-treated. A method is provided.

Claims (5)

[Claims] 1. A resin-laminated lid having a scored portion, wherein the polyester resin layer is provided at least on the inner surface side of the can, and the molecular weight of the polyester resin in the portion of the inner surface resin layer along the scored portion is 25,000 to 25,000. 70
000 in the range of 000. 2. The laminated lid according to claim 1, wherein at least one of the inner and outer surfaces of the can lid in the polyester resin layer is substantially unstretched. 3. The laminate lid according to claim 1, wherein the in-plane birefringence ΔN of the inner resin layer is 0.020 or less in the initial opening portion. 4. A method for producing a laminated lid, comprising: after laminating a laminate having a polyester resin layer provided on at least one surface of an aluminum plate or a steel plate, heat-treating at least the resin layer near the opening. 5. The method according to claim 4, wherein the polyester resin of the inner resin layer has a molecular weight in the range of 25,000 to 70,000.