JP4236514B2 - Resin-coated metal plate for easy-open lid and easy-open lid made of this resin-coated metal plate - Google Patents

Description

【００５０】
【表２】

【００５１】
【発明の効果】
本発明の樹脂被覆金属板によれば、金属素材の少なくとも一方の表面に、金属素材側から順に、重量平均分子量４００００乃至８００００の熱可塑性ポリエステル樹脂にオレフィン系重合体が配合されて成る下層、熱可塑性ポリエステル樹脂から成る伸度が２０％以下の表層が形成されて成ることにより、優れた加工性、耐食性を有すると共に、蓋に成形した場合にフェザーリング現象の発生が抑制され開口性に優れていると共に、耐レトルト性にも優れている。
【図面の簡単な説明】
【図１】樹脂被覆金属板と加工性の関係を説明するための図である。
【図２】樹脂被覆金属板と開口性との関係を説明するための図である。
【図３】本発明の樹脂被覆金属板の一例を示す断面図である。
【図４】本発明の樹脂被覆金属板の他の一例を示す断面図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin-coated metal plate, and more particularly, to a resin-coated metal plate excellent in workability and corrosion resistance, and a lid excellent in openability made of this resin-coated metal plate.
[0002]
[Prior art]
Conventionally, an easy open (EO) lid that can be easily opened by hand without using a special tool has been widely used. The easy open lid includes a tear-off type that separates the opening portion from the can body, and an opening portion. There is a steion tab (SOT) type that leaves the material attached to the can body. Such an easy-open lid uses a resin-coated metal plate formed by coating a metal material such as aluminum, aluminum alloy, tinplate, and tin-free steel with a resin such as a polyester resin. A score is provided on the lid so as to reach the middle in the thickness direction of the resin-coated metal plate to form an opening portion.
[0003]
In the above SOT-type can lid, the score is cut in a form in which the inner surface side resin layer of the resin-coated metal plate is stretched by opening operation, because the score is cut and opened by pushing the opening tab tip, There is a tendency for delamination to occur between the metal material and the resin layer.
On the other hand, a full open can, which is a common food can, is a tear-off type. In the initial stage of opening, the score is cut by pushing the tip of the opening tab as in the SOT format, and then the opening is pulled. Separate from the canister body. Even in this case, as in the SOT format, the resin layer is stretched and delamination tends to occur between the metal material and the resin layer.
In addition, even when the adhesion between the metal material and the inner surface resin layer is large and significant delamination does not occur, a so-called feathering phenomenon occurs in which a resin film extending around the opening remains. Since the feathering phenomenon gives an unsanitary image in appearance, it must be prevented.
[0004]
It is characterized by laminating a crystalline saturated polyester resin and heat-treating from the cold crystallization start temperature to a temperature lower than the melting point after press processing in order to achieve both prevention of processing defects due to press processing and feathering resistance at the time of opening. A method for producing a metal easily openable lid material has been proposed (Patent Document 1).
In addition, a laminate lid in which the molecular weight of the polyester resin of the inner surface resin layer in the portion along the score processed portion is in the range of 25000 to 70000 has been proposed. In this laminate lid, the laminated lid after processing is heated. The occurrence of delamination is suppressed (Patent Document 2).
[0005]
[Patent Document 1]
Japanese Patent No. 3153055
[Patent Document 2]
JP 2001-122258 A
[0006]
[Problems to be solved by the invention]
The proposal of performing press processing in a state where the degree of crystallization is small and the elongation is large in order to prevent processing defects according to Patent Document 1 is very effective in securing workability and corrosion resistance. It is industrially difficult to prevent feathering by advancing crystallization by cold heat treatment to suppress elongation. That is, the degree of crystallinity of the polyester is 60% at most even under sufficient time and temperature conditions, and the rest is retained due to the amorphous structure. For this reason, feathering cannot be sufficiently suppressed, and the opening is not sufficient.
[0007]
The laminate lid described in Patent Document 2 has both openability and workability. However, when the heat treatment is performed after processing like this laminate lid, when aluminum is used as a metal material, There arises a problem that the hardness is lowered and the pressure resistance is lowered, or the content resistance is lowered due to loss of orientation of the resin. Moreover, since it is not premised on heat sterilization, such as retort sterilization, there exists a problem that it is inferior to retort resistance.
[0008]
Accordingly, an object of the present invention is to provide a resin-coated metal plate that is excellent in workability and corrosion resistance, and does not cause delamination or feathering when formed into a can lid, and has openability, workability and corrosion resistance, and retort resistance. It is also to provide an excellent can lid.
[0009]
  According to the present invention, on at least one surface of a metal material, in order from the metal material side, a lower layer in which an olefin polymer is blended with a thermoplastic polyester resin having a weight average molecular weight of 40,000 to 80,000, the thermoplastic polyester resin is formed. A surface layer having an elongation of 20% or less is formed.For easy open lidA resin-coated metal plate is provided.
  Of the present inventionFor easy open lidIn resin-coated metal plates,
1. The olefin polymer is contained in the thermoplastic polyester resin in an amount of 0.1 to 30% by weight;
2. The weight average molecular weight of the thermoplastic polyester resin constituting the surface layer is in the range of 25000 to 40000,
3. The weight average molecular weight of the thermoplastic polyester resin constituting the surface layer is in the range of 25000 to 70000, and the crystallinity is 20% or more,
4). The thermoplastic polyester resin constituting the surface layer is a copolyester containing an isophthalic acid component and / or a polyfunctional component;
5). The isophthalic acid component is blended in an amount of 5 to 25 mol% in the total carboxylic acid component,
6). The polyfunctional component is blended in an amount of 0.1 to 0.5 mol% in the carboxylic acid component or alcohol component,
Is preferred.
  According to the present invention, the aboveFor easy open lidMade of resin-coated metal plateEasy openA lid is provided.
[0010]
In the resin-coated metal plate of the present invention, at least one surface of a metal material, in order from the metal material side, a lower layer in which an olefin polymer is blended with a thermoplastic polyester resin having a weight average molecular weight of 40,000 to 80,000, thermoplastic It is an important feature that a surface layer composed of a polyester resin and having an elongation of 20% or less is formed.
The delamination and feathering phenomenon described above is caused by the breaking of the score in the form that the resin film is stretched. In order to suppress the occurrence of delamination and feathering, the elongation of the resin film is suppressed. Need to be reduced. On the other hand, in order to improve the workability of the resin-coated metal plate, it is desirable that the degree of crystallization of the resin film is small and the elongation is large. Thus, the openability and the workability are mutually contradictory characteristics. is there.
In the present invention, even if there is a layer having a large elongation of the resin film and excellent in workability but inferior in opening property, by making this layer a multilayer structure with a layer having excellent opening property, At the same time, it was found that the elongation of the layer with poor opening properties was suppressed and the occurrence of delamination and feathering phenomenon was effectively suppressed, and it was possible to combine both of these conflicting characteristics at a high level. Is.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
[Resin-coated metal plate]
FIG. 1 is a view for explaining the workability of a resin-coated metal plate. As is apparent from FIG. 1, a resin-coated metal plate (Comparative Example 1) having a coating layer made of polyethylene terephthalate used for general resin coating and a polyester resin having an elongation of 20% or less used for the surface layer of the present invention. In the resin-coated metal plate (Comparative Example 2) having a coating layer made of a material, a high current was detected both after the lid processing and after the T-bend, whereas the resin coating was damaged by the processing. The resin-coated metal plate (Comparative Example 3) having a coating layer made of a polyester resin containing an olefin polymer used in the lower layer of the present invention has excellent processability both after the lid processing and after the T-bend. It is clear that
[0012]
The T-bend test is one of the test methods for evaluating the workability of a laminated metal plate. A laminated metal material is folded in a mountain, a voltage of 6.30 V is applied to the bent portion for 4 seconds, and the current value flowing at that time is measured. Read. As is clear from FIG. 1, this test method has a correlation with the workability of the lid, and it can be said that the lower the current value, the better the workability when the lid is used.
[0013]
FIG. 2 is a view for explaining the opening of a can lid made of a resin-coated metal plate. As is apparent from FIG. 2, a resin-coated metal plate (Comparative Example 1) having a coating layer (elongation 10%) made of polyethylene terephthalate used for general resin coating and the olefinic system used in the lower layer of the present invention. In the resin-coated metal plate (Comparative Example 3) having a coating layer (elongation 80%) made of a polyester resin containing a polymer, feathering of 3.0 mm or more occurs, whereas the present invention In the resin-coated metal plate (Comparative Example 2) having a coating layer made of a polyester resin having an elongation of 20% or less used for the surface layer of the above, it is clear that almost no feathering occurs and the opening property is excellent. .
[0014]
On the other hand, in FIG.1 and FIG.2, the resin-coated metal plate which used as a lower layer the polyester resin in which the said olefin type polymer was contained, and made the polyester resin below 20% of elongation (Examples 1-5) Then, as is clear from the results of the examples described later, the excellent processability of the resin-coated metal plate of Comparative Example 3 and the excellent property of the resin-coated metal plate of Comparative Example 2 in both characteristics of workability and openability. The result is comparable to the openness.
The resin-coated metal plate of the present invention has excellent workability even when the crystallinity of the surface layer is in the state of the resin-coated metal plate, that is, the crystallinity is 20% or more before the lid processing. There is no need for heat treatment to improve the openability after the lid, and the advantage of excellent productivity is also obtained.
[0015]
(Polyester lower layer)
The lower layer provided on the surface of the metal material of the resin-coated metal plate of the present invention is obtained by blending an olefin polymer with a thermoplastic polyester resin having a weight average molecular weight of 40,000 to 80,000, particularly 50,000 to 75,000.
The polyester resin used for the lower layer is a thermoplastic polyester 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. Is mentioned.
[0016]
As the thermoplastic polyester resin, polyethylene terephthalate itself can be used under limited lamination conditions, but it is desirable to reduce the maximum crystallinity that the film can reach in terms of processability and impact resistance, In the lower layer, it is preferable to introduce copolymer ester units other than ethylene terephthalate into the polyester. It is particularly preferable to use a copolyester having an ethylene terephthalate unit or a butylene terephthalate unit as a main component and a melting point of 180 to 252 ° C. containing a small amount of other ester units. The melting point of homopolyethylene terephthalate is generally 255 to 265 ° C.
[0017]
In general, 70 mol% or more, particularly 75 mol% or more of the dibasic acid component in the copolyester is composed of a terephthalic acid component, and 70 mol% or more, particularly 75 mol% or more of the diol component is composed of ethylene glycol or butylene glycol, It is preferable that 1 to 30 mol%, particularly 5 to 25 mol% of the dibasic acid component is composed of a dibasic acid component other than terephthalic acid.
[0018]
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, dodecanedioic acid, etc. Or a combination of two or more of the aliphatic dicarboxylic acids: As the diol component other than ethylene glycol or butylene glycol, propylene glycol, diethylene glycol, 1,6-hexylene glycol, cyclohexane dimethanol, bisphenol A 1 type, or 2 or more types, such as an ethylene oxide adduct.
Polyester resins are blended with known resin compounding agents such as anti-blocking agents such as amorphous silica, inorganic fillers, various antistatic agents, lubricants, antioxidants, UV absorbers, etc. according to known formulations. can do.
[0019]
Examples of the olefin polymer blended in the polyester lower layer of the present invention include low-, medium-, and high-density polyethylene, linear low density polyethylene (LLDPE), isotactic polypropylene, ethylene-propylene copolymer, propylene. In addition to olefin homopolymers or copolymers such as butene-1 copolymer and ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ion-crosslinked olefin Examples thereof include olefin polymers such as copolymers (ionomers) or blends thereof.
In the present invention, among these olefin polymers, those having a polar group are preferred, and an ion-crosslinked olefin copolymer (ionomer) can be most suitably used.
[0020]
The ionomer resin is an ionic salt in which a part or all of the carboxyl groups in the copolymer of ethylene and α, β-unsaturated carboxylic acid are neutralized with a metal cation, and the degree of neutralization, that is, an ion Concentration affects its physical properties. In general, the melt flow rate (hereinafter simply referred to as MFR) of an ionomer resin depends on the ion concentration. If the ion concentration is high, the MFR is small, and the melting point depends on the carboxyl group concentration. The higher the carboxyl group concentration, the smaller the melting point. Become.
Accordingly, the ionomer resin used in the present invention is of course not limited thereto, but has an MFR of 15 g / 10 min or less, particularly 5 g / 10 min to 0.5 g / 10 min, and a melting point of 100 ° C. or less. In particular, it is desirable that the temperature is in the range of 97 ° C to 80 ° C.
[0021]
The α, β-unsaturated carboxylic acid constituting the ionomer resin is an unsaturated carboxylic acid having 3 to 8 carbon atoms, specifically acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, monomethyl maleate Examples thereof include esters and maleic acid monomethyl ester.
Particularly suitable base polymers include ethylene- (meth) acrylic acid copolymers and ethylene- (meth) acrylic acid ester- (meth) acrylic acid copolymers.
Further, as a metal ion for neutralizing the carboxyl group in the copolymer of ethylene and α, β-unsaturated carboxylic acid, Na⁺, K⁺, Li⁺, Zn⁺, Z²⁺, Mg²⁺, Ca²⁺, Co²⁺, Ni²⁺, Mn²⁺, Pb²⁺, Cu²⁺In the present invention, those neutralized with zinc can be preferably used since they have a high degree of crosslinking and low humidity sensitivity. Further, a part of the remaining carboxyl groups that are not neutralized with metal ions may be esterified with a lower alcohol.
The ionomer resin contains 80 to 99 mol% of structural units derived from ethylene, preferably 85 to 96 mol%, and 1 to 20 mol%, preferably 4 to 15 mol of structural units derived from an unsaturated carboxylic acid. % Is preferably contained.
[0022]
The olefin polymer is preferably blended in the thermoplastic polyester in an amount of 0.1 to 30% by weight, particularly 2 to 20% by weight. If the amount of the olefin polymer is less than the above range, the workability cannot be sufficiently improved, and the impact resistance (dent resistance), corrosion resistance, and adhesion are inferior. When the amount of the olefin polymer is large, a feathering phenomenon may occur even when the olefin polymer is formed into a multilayer with the upper layer, which may impair the openability and deteriorate the film forming property.
[0023]
(Polyester surface layer)
The polyester surface layer formed on the above-described polyester lower layer is a layer made of a thermoplastic polyester resin having an elongation of 20% or less. When the elongation is 20% or less, the feathering phenomenon can be effectively prevented even when combined with a lower layer having a relatively large elongation. A method for measuring the elongation will be described later in Examples.
As the thermoplastic polyester resin used for the surface layer, the same thermoplastic polyester resin as that of the lower layer described above can be used. However, the surface layer particularly contains isophthalic acid as a dicarboxylic acid component in an amount of 5 to 25 mol%. In order to suppress the elongation of the resin, a copolyester resin is preferable.
In order to make the elongation particularly suitable, it is preferable to contain at least one branching or crosslinking component selected from the group consisting of tribasic or higher polybasic acids and polyhydric alcohols. The cross-linking component is preferably in the range of 0.1 to 0.5 mol% in the total carboxylic acid component or the total alcohol component. By blending such a polyfunctional component, a crosslinked structure is introduced, and a hard coating layer with little elongation can be obtained.
Further, when the surface layer is composed only of the thermoplastic polyester resin, the weight average molecular weight is in the range of 25000 to 40000, or the weight average molecular weight is in the range of 25000 to 70000, and the crystallinity is 20% or more. Similarly, it is preferable from the viewpoint of preventing the feathering phenomenon.
[0024]
Examples of the trifunctional or higher polybasic acid and polyhydric alcohol 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, polybasic acids such as biphenyl-3,4,3 ′, 4′-tetracarboxylic acid, pentaerythritol, glycerol, Examples include polyhydric alcohols such as trimethylolpropane, 1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakis (hydroxymethyl) cyclohexane.
[0025]
(Metal material)
As the metal material used for the resin-coated metal plate of the present invention, all metal materials conventionally used for easy open lids such as various aluminum materials and various steel plates can be used.
[0026]
As the aluminum material, for example, pure aluminum or aluminum and another alloy metal, particularly an aluminum alloy containing a small amount of magnesium, manganese or the like is used.
As an aluminum alloy, Cu 0-0.8%, Mg 0-2.8%, Mn 0-1.5%, Fe 0-0.5%, Si 0-0. An aluminum alloy containing 5% (% is based on weight) is desirable. The thickness of the aluminum material varies depending on the size of the lid and the like, but is generally within a range of 0.20 to 0.50 mm, particularly 0.23 to 0.30 mm. From the viewpoint of adhesion of the inner surface material to the aluminum material and corrosion resistance, it is generally desirable to form a surface treatment film on the surface of the aluminum material. Preferred examples of the surface treatment include chromate treatment, zirconium treatment, phosphoric acid treatment, polyacrylic acid treatment, and anodizing treatment.
[0027]
Various types of steel sheets include chromate-treated steel sheets, especially electrolytic chromate-treated steel sheets, chromate-treated nickel-plated steel sheets, chromate-treated iron / tin alloy-plated steel sheets, chromate-treated tin-nickel alloy-plated steel sheets, chromate-treated iron / tin-nickel alloy plates. Steel plates, chromate-treated aluminum-plated steel plates, chromate-treated tinplate, etc. are used. The thickness of the steel plate substrate is determined by the balance between the pressure resistance deformability, workability, and easy opening, and is generally preferably in the range of 0.1 to 0.4 mm, particularly 0.12 to 0.35 mm.
Among these, an electrolytic chromic acid-treated steel plate is preferable, and this has a metal chromium layer and a non-metal chromium layer thereon on a steel plate substrate. The thickness of the metallic chromium layer is determined by the balance between corrosion resistance and workability, and the amount is 30 to 300 mg / m.² , Especially 50 to 250 mg / m² It is desirable to be in the range. The thickness of the non-metallic chromium layer is related to coating film adhesion and adhesive peel strength, and is expressed as 4 to 40 mg / m in terms of chromium content.² , Especially 7-30mg / m² It is desirable to be in the range.
[0028]
(Layer structure)
FIG. 3 is a sectional view showing an example of a sectional structure of the resin-coated metal plate of the present invention. The resin-coated metal plate represented by 1 as a whole is composed of a thermoplastic polyester resin on the lower layer 2 and the lower layer 2 in which an olefin polymer is blended with a thermoplastic polyester resin having a weight average molecular weight of 40,000 to 80,000 on the metal substrate 1. A surface layer 3 having an elongation of 20% or less is formed.
Further, in another example of the resin-coated metal plate of the present invention shown in FIG. 4, similar resin coating layers 2 and 3 are formed on the other surface of the resin-coated metal plate in FIG.
In the resin-coated metal plate of the present invention, it is sufficient that the surface layer and the lower layer are formed on at least one surface of the metal material, and a similar coating layer is provided on the other surface as in the specific example shown in FIG. Alternatively, a protective layer made of a known polyester resin conventionally used for resin coating, a thermosetting resin paint, or a thermoplastic resin paint may be provided on the other surface.
In addition, a primer layer (not shown) may be provided between the metal material 1 and the lower layer 2 although it is not generally necessary.
[0029]
In the resin-coated metal plate of the present invention, the thickness ratio of the polyester lower layer and the polyester surface layer is preferably in the range of 1: 1 to 5: 1 in order to satisfy both the opening property and the workability. That is, if the lower layer is thicker than the above range, the opening property and impact resistance may be insufficient, and if the lower layer is thinner than the above range, the workability and corrosion resistance may be insufficient.
The thickness of each layer is not limited to this, but the lower layer is preferably 5 to 30 μm, particularly preferably 10 to 25 μm, and the surface layer is preferably 5 to 30 μm, particularly 5 to 15 μm.
Moreover, when providing the protective layer which consists of a conventionally well-known polyester resin, a thermosetting resin coating material, or a thermoplastic resin coating material on the other surface of a metal raw material, it is preferable that the thickness exists in the range of 0.1-10 micrometers.
[0030]
(Production of resin-coated metal plate)
The resin-coated metal sheet of the present invention uses at least an extruder for the surface layer resin and an extruder for the lower layer resin, and the resin flow from each extruder is merged in the multi-layer die to form a thin film from the T-die. It can be manufactured by extruding and passing the extruded molten resin film together with a metal substrate between a pair of laminate rolls and pressing and integrating them under cooling. Further, by passing a metal substrate vertically between a pair of laminate rolls and supplying a molten resin web on both sides thereof, a polyester resin coating layer can be formed on both surfaces of the metal substrate.
[0031]
Specifically, the production of the resin-coated metal plate by the coextrusion coating method is performed as follows. If necessary, the metal plate is preheated by a heating device and supplied to the nip position between the pair of laminate rolls. On the other hand, each polyester resin is extruded in the form of a thin film through the die head of each extruder, supplied between the laminate roll and the metal plate, and pressed onto the metal plate by the laminate 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 them together, and is cooled from both sides to obtain a laminate.
[0032]
The resin-coated metal plate of the present invention can also be produced by thermally bonding an unstretched polyester resin film formed in advance to a metal substrate. In this case, the 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 in the same manner as described above.
[0033]
In the resin-coated metal sheet of the present invention, it is particularly preferable that the crystallinity of the surface layer is 20% or more in order to have excellent openability after the lid molding, but as described above, it is 20% or more from before the lid processing. Even if it has, it has excellent workability. For this reason, it is not necessary to carry out the rapid cooling operation for preventing the progress of thermal crystallization accompanying lamination. Further, it is not necessary to perform a heat treatment or the like for proceeding crystallization after the pressing process in the lid molding, and an advantage that the productivity is excellent is also obtained.
[0034]
[Lid and its manufacturing method]
The lid of the present invention can take a conventionally known shape except that the surface on which the polyester lower layer and the surface layer of the resin-coated metal plate are formed is the inner surface side of the lid. It is preferable that it is an easy open lid of a system or a steion tab system.
[0035]
The easy open lid is formed by first stamping the resin-coated metal plate into a disk shape and forming it into a desired lid shape in a press molding process. Next, in the score marking step, the score is stamped using a score die so that the score reaches the middle of the metal material from the outer surface side of the lid. Residual thickness of metal material in the score (t₂) Is the original thickness (t₁) For t₂/ T₁X100 is 10 to 50%, t₂Is preferably 20 to 150 μm. Further, it is important for the bottom width (d) of the score to be 75 μm or less, particularly 50 μm or less, in order to prevent the film layer from being damaged.
[0036]
In the rivet forming process, a rivet protruding to the outer surface is formed in the opening section defined by the score using a rivet forming die, and in the tab attaching process, the opening tab is fitted to the rivet, and the protruding part of the rivet is fed out. An easy open lid is formed by fixing the tab. In the case of an adhesive tab instead of a rivet forming process, an adhesive such as a nylon adhesive tape is applied to the opening or the tab, and the tab and the opening are thermally bonded in the tab attaching process. .
[0037]
The easy-open lid formed as described above suppresses the occurrence of feathering without performing heat treatment after score processing, but with higher openability and removal of residual strain near the score processing portion. Of course, heat treatment can be performed for the purpose of restoring the adhesion of the resin coating layer. The heat treatment temperature is preferably 180 to 280 ° C. for 15 to 60 seconds.
Finally, in the lining process, the sealing compound is lining-coated through a nozzle in the sealing groove of the lid, and dried to form a sealant layer.
In the lid of the present invention, the flange of the can body member and the sealing groove of the easy open lid are fitted, and the groove is primarily wound around the flange using a primary winding roll. Next, in the secondary winding step, this flange portion can be further wound along the can body side wall portion to form a can body.
[0038]
【Example】
The present invention is illustrated by the following examples, which are intended to be illustrative and are not limited in any way to the following examples. Measurements in the examples were performed as follows.
[0039]
[Evaluation and measurement method]
(Metal material)
The aluminum alloy A5052H18 having a plate thickness of 0.25 mm was subjected to a chromic acid / phosphoric acid surface treatment to obtain a metal material.
[0040]
(Manufacturing method of laminated metal material)
The resin material is supplied to a twin screw extruder, and the film is obtained by extruding the barrel and T-die at a temperature suitable for the resin material. The film is laminated on the aluminum alloy plate heated to 250 ° C., Immediately water-cooled to obtain a laminated metal material. At this time, the resin thickness on the inner surface of the lid was set to 30 μm. After painting on the side of the resulting single-sided laminate that would be the outer surface of the lid, it was baked at 185 ° C. for 10 minutes.
[0041]
(Cover manufacturing method)
For the EO lid, for the above laminated metal material, a lid is formed from a blank with a diameter of 90.5 mm, and score processing (residual pressure 120 μm, score width 25 μm), rivet processing and attachment of unsealing tabs are performed on this lid It was created.
As for the SOT lid, a 68.7 mm diameter lid is punched out of the above-mentioned laminated metal material, and a partial opening type score processing (width 22 mm, score residual pressure 110 μm, score width 20 μm), rivet processing is performed on the lid from the outside. In addition, an opening tab was attached and a lid was prepared.
[0042]
(Openness evaluation)
A lid made of a laminated metal material was subjected to a retort treatment at 110 ° C. for 60 minutes, immersed in water for 10 minutes, and then the lid was opened by hand under wet conditions, and the periphery of the opening was visually observed and evaluated.
○ Good: Feathering <1.0mm
× Defect: Feathering> 1.0 mm
[0043]
(Processability evaluation)
Evaluation was carried out based on the current value when a voltage of 6.30 V was applied to the entire inner surface of the lid made of the laminated metal material for 4.0 seconds.
○ Good: Average current value <0.005 mA
X Defect: Average current value> 0.005 mA
[0044]
(Molecular weight)
At the time of film formation, the surface layer and lower layer of the thick film directly under the T die were scraped to prepare a sample. The measurement was performed using a molecular weight measurement high-speed GPC apparatus HLC-8120GPC (manufactured by Tosoh Corp.) and a column configuration in which two TSK-GELSuperHM-H (manufactured by Tosoh Corp.) were connected after the card column. An ultraviolet detector UV-8020 (manufactured by Tosoh) was used as the detector, and the measurement wavelength was 254 nm. The measurement temperature condition is 40 ° C. The resin layer was isolated from the can lid, 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 the eluent, and the flow rate was 0.6 ml / min. A calibration curve was prepared from a Tosoh molecular weight standard styrene sample, and the weight average molecular weight (Mw) was determined.
[0045]
(Measurement of crystallinity)
The surface layer of the thick film directly under the T-die at the time of film formation was scraped, subjected to a heat treatment at 185 ° C. for 10 minutes and a retort treatment at 110 ° C. for 60 minutes, and then a differential operation calorimeter (DSC) measurement was performed. The measurement was performed using a DSC7-RS manufactured by PERKIN ELMER at a rate of temperature increase of 10 ° C./min. The crystallinity was calculated from the melting peak ΔH obtained by the measurement using the following formula.
Crystallinity (%) = (ΔH (PET) − | ΔHc |) / ΔH (PET) × 100
ΔH (PET) = 122.25 J / g
[0046]
(Tensile test)
The test was conducted using UCT-5T manufactured by Orientec. A film having a resin composition equivalent to that of the surface layer was formed, and a laminated metal material using aluminum as a base material was prepared. The laminated metal material was heat treated at 185 ° C. for 10 minutes and retorted at 110 ° C. for 60 minutes, and then the metal plate was dissolved with 6N hydrochloric acid to isolate and dry the film. A sample having a length of 10 mm and a width of 5 mm was used as a sample, the test temperature was 25 ° C., and the tensile speed was 5 mm / min.
[0047]
[Examples 1 to 6]
An EO lid / SOT lid having an inner surface resin composition as shown in Table 2 was prepared, and processability and openability were evaluated, and physical properties of the film were measured. The obtained evaluation results and measurement results are shown in Table 1.
As a result, Examples 1 to 6 were applicable as lids.
[0048]
[Comparative Examples 1 to 12]
An EO lid / SOT lid having an inner surface resin composition as shown in Table 2 was prepared, and processability and openability were evaluated, and physical properties of the film were measured. Compositions 1 to 3 are single layer films, and 4 to 13 are two layer films. The obtained evaluation results and measurement results are shown in Table 1.
As a result, about Comparative Examples 1-8 and 10-13, opening property and workability were not compatible, and it was not applicable as a lid | cover. In Comparative Example 9, the film formation was poor and a laminated metal material could not be created.
[0049]
[Table 1]

[0050]
[Table 2]

[0051]
【The invention's effect】
According to the resin-coated metal plate of the present invention, on at least one surface of the metal material, in order from the metal material side, a lower layer formed by blending an olefin polymer with a thermoplastic polyester resin having a weight average molecular weight of 40,000 to 80,000, By forming a surface layer made of a plastic polyester resin with an elongation of 20% or less, it has excellent workability and corrosion resistance, and when it is molded into a lid, the occurrence of feathering phenomenon is suppressed and the opening is excellent. In addition, it has excellent retort resistance.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the relationship between a resin-coated metal plate and workability.
FIG. 2 is a diagram for explaining a relationship between a resin-coated metal plate and opening properties.
FIG. 3 is a cross-sectional view showing an example of a resin-coated metal plate of the present invention.
FIG. 4 is a cross-sectional view showing another example of the resin-coated metal plate of the present invention.

Claims (8)

On the surface of at least one of the metal materials, in order from the metal material side, a lower layer formed by blending an olefin polymer with a thermoplastic polyester resin having a weight average molecular weight of 40,000 to 80,000, and an elongation composed of the thermoplastic polyester resin is 20% or less. A resin-coated metal plate for an easy open lid , characterized in that the surface layer is formed. The resin-coated metal plate for an easy-open lid according to claim 1, wherein the olefin polymer is contained in the thermoplastic polyester resin in an amount of 0.1 to 30% by weight. The resin-coated metal plate for an easy-open lid according to claim 1 or 2, wherein the thermoplastic polyester resin constituting the surface layer has a weight average molecular weight in the range of 25000 to 40000. The resin-coated metal plate for an easy-open lid according to claim 1 or 2, wherein the thermoplastic polyester resin constituting the surface layer has a weight average molecular weight in the range of 25000 to 70000 and a crystallinity of 20% or more. The resin-coated metal plate for an easy open lid according to any one of claims 1 to 3, wherein the thermoplastic polyester resin constituting the surface layer is a copolyester containing an isophthalic acid component and / or a polyfunctional component. The resin-coated metal plate for an easy open lid according to claim 5, wherein the isophthalic acid component is blended in an amount of 5 to 25 mol% in the total carboxylic acid component. The resin-coated metal plate for an easy open lid according to claim 5 or 6, wherein the polyfunctional component is blended in an amount of 0.1 to 0.5 mol% in the carboxylic acid component or the alcohol component. Easy open end, characterized in that it consists of easy open end for a resin-coated metal sheet according to any one of claims 1 to 7.

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