JP6060643B2 - Easy-open can lid made of resin-coated steel sheet and method for producing the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an easy open can lid used for a can lid for food cans and a method for producing the same, by breaking an opening formed in a can lid of a can body.

2. Description of the Related Art An easy open can lid is widely used as a lid for canned food containing food such as fish, fruits, vegetables, etc., by opening the can opening with a finger to open the can. The easy open can lid is roughly classified into a full open type can lid mainly used for food canning and a partial type can lid mainly used for beverage cans.
A full-open type can lid has an opening groove formed along the outer periphery of the can lid, and the tab attached to the panel near the outer periphery of the can lid is pulled up with a fingertip to remove the opening piece from the can lid. It comes to separate.

  For forming such an opening groove in such an easy open can lid, conventionally, as shown in FIG. 1, a processing tool 10 having a cutting edge-like (V-shaped) projection having a predetermined opening profile is used. It is performed by pressing with a press with a high load such that the opening groove 2 having a depth of 1/2 or more of the thickness of the lid plate 11 is formed from the surface side of the can lid, An opening groove 2 having a V-shaped cross section was formed.

  In this way, the formation of the opening groove is performed by pressing with a high load using a processing tool, and in the case of a can lid made of a resin-coated steel plate coated with resin on both sides, it is press-molded. Sometimes, the resin film formed on both sides of the can lid is damaged, resulting in a problem that the corrosion resistance deteriorates. Therefore, in order to prevent the deterioration of the corrosion resistance, repair coating has to be performed after the press molding, and much labor and cost are required.

  Against this background, in recent years, aluminum that does not rust even if the resin film is damaged has been used as the material for cans of food cans. There is also a problem from a point.

  Therefore, as a countermeasure against the problem that occurs when the opening groove is formed in the can lid made of the resin-coated steel plate as described above, Patent Documents 1 to 3 disclose a method of forming the opening groove by composite extrusion processing. ing.

  According to the description in Patent Literatures 1 to 3, since the opening groove is formed by the composite extrusion process, the resin film is not damaged and repair coating is unnecessary. However, the details of the processing conditions and groove shape of the composite extrusion are unknown, and it is difficult to judge the reproducibility of stably forming the opening groove.

  Patent Document 4 discloses a method using a curved score mold. It has been disclosed to use a mold that is a curved surface mold having a radius of 0.1 to 1.0 mm and to perform press molding so that the thickness of the thinnest part is in a range of 0.025 to 0.08 mm. By adopting the curved surface type, the compressive stress generated during the processing of the groove for opening can be greatly reduced, so that reduction of film damage can be expected.

  According to this method, the film damage of the opening groove portion is certainly reduced as compared with the conventional V-shaped opening groove mold. However, it has been found that there is still room for improvement in can openability. The reason is shown below.

  FIG. 1 shows a conventional V-shaped opening groove section, and FIG. 2 shows a curved opening groove section. It can be seen that by using a curved surface shape as shown in FIG. By using a curved mold, the contact area with the material increases, and the surface pressure (compressive stress) generated during processing can be greatly reduced. It will be expanded in the direction (width direction). For this reason, the processing region of the opening groove is enlarged, and the steel plate pushed out from the processed portion remains with a prominent processing ridge (unevenness) formed on the lid panel.

  In a general full-open lid manufacturing process, bead processing is performed after the opening groove is processed, and the processing wrinkles are absorbed by the bead processing portion. In the case of the conventional V-shaped opening groove type, there is no problem because the generation amount of machining wrinkles is small, but in the case of curved surface processing specified in Patent Document 4, the generation amount of machining wrinkles becomes extremely large. For this reason, the processing flaws cannot be eliminated unless the bead processing amount is significantly increased. On the other hand, increasing the amount of bead processing means that there is an increased risk of deforming the thinnest groove for opening, and as shown in FIG. 3, there is a problem that the groove for opening is greatly deformed. This phenomenon (deformation of the opening groove) is affected by the processing conditions of the opening groove, and becomes more prominent as the thickness of the thinnest opening groove decreases and the bead processing speed increases. When the opening groove shape is deformed as described above, even when stress is applied from the outside, the force is not easily concentrated on the thinnest portion of the opening groove, and an unnecessarily large force is required to open the lid. At present, in the canned food field, human-friendly technology is aimed at, and a lid that can be easily opened even by elderly people and children is strongly demanded, and it is desired to prevent deformation of the opening groove. In addition, with the recent remarkable economic development of BRICs countries and other countries, the demand for lids is expected to increase in the future, and further increase in the processing speed is inevitably. Therefore, it is considered that the can lid is more easily deformed and the amount of deformation is increased, and a can lid that has excellent can openability and does not cause impact destruction is desired.

  On the other hand, Patent Document 5 is an easy-open can lid made of a resin-coated steel plate mainly composed of polyester on both sides, the groove for opening is formed on both sides of the can lid, and the cross-sectional shape of the groove for opening is It is composed of a curve and / or a straight line, the slope (Tp) in the cross-sectional shape of the opening groove is 1.5 or less, the thickness of the thinnest part of the opening groove is 0.035 mm or more and 0.075 mm or less, and the opening groove A can lid that is excellent in can opening property and does not cause impact destruction is disclosed by setting the ratio of the thickness of the thinnest part to the thickness of the resin-coated steel sheet to be 0.1 or more. In addition, with respect to impact fracture characteristics that are slightly insufficient only by this, it is disclosed that impact fracture characteristics are further improved by forming a multilayer structure on at least one surface and containing a block-free isocyanate compound in the adhesion layer. Yes. According to this method, it is possible to achieve a can lid that has excellent can openability and does not cause impact breakage.

JP-A-6-115546 JP-A-6-115547 JP-A-6-115548 JP-A-11-91775 JP 2010-105689 A

  However, in Patent Document 5, an isocyanate compound is used, and a highly toxic unreacted monomer may remain, which is not necessarily a safe substance. In addition, in a heat treatment for a very short time (less than 1 second) such as a heat fusion laminating method, the crosslinking reaction between the polyester resin and the isocyanate compound may not sufficiently proceed. Therefore, there is a possibility that strong adhesion between the base material and the resin layer cannot be secured, and there is a possibility that the resin layer may be peeled off at the opening groove processing portion where a large deformation occurs.

  In view of such circumstances, the present invention can cope with many characteristics required for food canning such as suppression of resin color change (hereinafter referred to as retort whitening phenomenon) by retort treatment, and has excellent can openability and impact fracture. It is an object of the present invention to provide an easy open can lid made of a resin-coated steel plate and a method for producing the same.

As a result of intensive studies by the present inventors for solving the problems, the following knowledge was obtained.
The bottom cross-sectional shape, the thickness of the thinnest part, etc. were defined on a can lid made of a resin-coated steel sheet in which a polyester resin composed of a specific resin structure was used as an adhesion layer with the steel sheet, and a polyester film was further laminated on the adhesion layer. By forming the opening groove, there is no film damage even in the thinnest part of the opening groove processed part, and furthermore, suppression of resin color change (hereinafter referred to as retort whitening phenomenon) due to retort treatment It has been found that an easy-open can lid made of a resin-coated steel plate having a function and excellent in can opening property can be obtained.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] An easy-open can lid made of a resin-coated steel plate, wherein grooves for opening are formed on both surfaces of a can lid made of a resin-coated steel plate, and the can is opened by breaking the groove for opening.
The resin-coated steel sheet has a resin layer mainly composed of polyester on both surfaces, and the resin layer on at least one surface has a structure of two or more layers, and the resin that adheres to the steel plate among the structures of two or more layers The layer (a) contains 1.0 to 50.0 mass% of any one or more selected from the group consisting of (i) a polyamine resin, a polyamidoamine resin, and a polyamide resin,
The opening groove is composed of the following: an easy open can lid made of a resin-coated steel sheet.
(A) The cross-sectional shape of the opening groove is constituted by a curve and / or a straight line. (B) The inclination (Tp) in the cross-sectional shape of the opening groove is 1.5 or less. (C) The thickness of the thinnest portion of the opening groove. 0.035 mm or more and 0.075 mm or less (D) The ratio of the thickness of the thinnest part of the opening groove to the thickness of the resin-coated steel sheet is 0.1 or more. [2] The cross-sectional shape of the opening groove has a radius of 0. The easy-open can lid made of a resin-coated steel plate according to [1], wherein the easy-open can lid is an arc curve of 1 mm to 0.5 mm.
[3] The easy-open can lid made of a resin-coated steel plate according to [1] or [2], wherein the resin layer (a) further contains (b) an epoxy resin.
[4] The resin according to any one of [1] to [3], wherein the resin layer (a) further contains (c) a metal alkoxide compound and / or a metal chelate compound. Easy open can lid made of coated steel.
[5] The adhesion amount of the resin layer (a) is 0.1 g / m ² or more and 3.0 g / m ² or less, according to any one of [1] to [4], Easy-open can lid made of resin-coated steel plate.
[6] The easy-open can lid made of a resin-coated steel plate according to any one of [1] to [5], wherein the resin layer (a) contains a colorant.
[7] The resin-coated steel plate easy open can lid according to any one of [1] to [6], wherein the resin layer (a) contains 5 PHR or more of a corrosion inhibitor.
[8] Easy open can lid made of resin-coated steel sheet according to any one of [1] to [7], wherein the resin layer (a) contains 0.1 to 30 mass% of a conductive polymer. .
[9] The polyester resin layer (b) that forms the upper layer of the resin layer (a) is formed from a polyester film, and the polyester film has at least 93 mass% of the structural units of the polyester as ethylene terephthalate units and / or ethylene naphthalates. It is a phthalate unit, has an area-converted average particle size of 0.005 to 5.0 μm, a relative standard deviation represented by formula (1) of 0.5 or less, and a major axis / minor axis ratio of 1 The resin-coated steel plate easy as described in any one of [1] to [8], wherein 0.005 to 10 mass% of particles having a Mohs hardness of less than 7 are contained in a range of 0.0 to 1.2. Open can lid.

[10] A pair of upper and lower gold configured with a curved surface with a radius of 0.1 mm to 0.5 mm or a curved line with a radius of 0.1 mm to 0.5 mm and a straight line with respect to a can lid panel made of a steel plate coated with a resin layer. The can lid according to any one of [1] to [9] is manufactured by using a mold and applying pressure molding so that the thickness of the thinnest part is within a range of 0.035 mm to 0.075 mm. A method for producing an easy-open can lid made of a resin-coated steel sheet.
[11] When the resin-coated metal sheet is press-molded using the mold according to [10], the entire processed part of the resin-coated steel sheet is pressed while maintaining a state in contact with the mold. A method for producing an easy open can lid made of a resin-coated steel sheet.

According to the present invention, it is possible to obtain an easy open can lid made of a resin-coated steel plate, which can cope with many characteristics required for food canning, has excellent can openability and does not cause impact destruction.
As described above, in the present invention, when the groove for opening is formed in the can lid made of the steel plate having the resin layer formed on both sides, the repair due to the damage of the plating layer and the resin coating layer formed on both sides of the can lid is performed. An easy-open can lid with excellent openability that can be easily opened by children and the elderly without painting is obtained, and has an industrially useful effect.

It is a figure which shows the cross-section of the conventional groove part for opening formed in the can lid. It is a figure which shows the cross-section of the groove part for opening formed in the can lid described in patent document 4. FIG. It is a figure which shows the cross-sectional structure of the groove part for opening after manufacture of the groove part for opening formed in the can lid of patent document 4. It is a figure which shows the principal part of the lamination apparatus of a steel plate. Example 1 It is a figure which shows the cross-section of the groove part for opening of this invention formed in the can lid. It is a figure which shows the cross-section of a resin-coated steel plate. Example 1 It is a figure which shows the cross-sectional structure of the groove | channel for opening. Example 1 It is a figure which shows the cross-sectional structure of the groove | channel for opening. Example 1 It is a figure which shows the cross-sectional structure of the groove | channel for opening. Example 1 It is a figure which shows the cross-sectional structure of the groove | channel for opening. Example 1 It is a figure which shows the cross-sectional structure of the groove | channel for opening. Example 1 It is a figure which shows the cross-sectional structure of the groove | channel for opening. Example 1

  Hereinafter, the resin-coated steel plate easy open can lid of the present invention will be described in detail.

First, the steel plate of the present invention used for the can lid will be described.
As the steel plate of the present invention, a mild steel plate widely used as a material for cans can be used. In particular, a surface-treated steel sheet (hereinafter referred to as TFS) on which a two-layer film is formed, in which the lower layer is made of metallic chromium and the upper layer is made of chromium hydroxide, is optimal.
The amount of adhesion of the metal chromium layer and chromium hydroxide layer of TFS is not particularly limited, but from the viewpoint of adhesion after processing and corrosion resistance, both are in terms of Cr, the metal chromium layer is 70 to 200 mg / m ² , chromium hydroxide layer is preferably in the range of 10 to 30 mg / ^{m 2.}

  In this invention, the resin layer which has polyester as a main component is coat | covered on both surfaces of the said steel plate, and it is set as a resin-coated steel plate. In the present invention, the resin containing polyester as a main component is a resin containing 50 mass% or more and 100 mass% or less of polyester, and when it contains a resin other than polyester, it can contain a resin such as polyolefin.

  In the present invention, as the polyester resin, one obtained by esterifying a polybasic acid component and a polyhydric alcohol component can be used. Examples of the polybasic acid component include terephthalic acid as a carboxylic acid component and polyethylene terephthalate composed of ethylene glycol as a glycol component, but isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid and the like as other carboxylic acid components In addition, diethylene glycol, propylene glycol, butanediol, neopentyl glycol and the like as other glycol components include copolymer resins and the like. As an acid component, terephthalic acid is essential because of mechanical strength, heat resistance, chemical resistance, and the like, but further, by copolymerizing with isophthalic acid, flexibility, tear strength, and the like are improved. By copolymerizing the isophthalic acid component with the terephthalic acid component in the range of 10.0 mol% or more and 60.0 mol% or less, it is preferable because it functions to improve deep drawability and post-processing adhesion. As the glycol component, a low Tg (Tg = glass transition temperature) component having excellent flexibility such as ethylene glycol and propanediol and a rigid high Tg component having a ring structure such as neopentyl glycol and cyclohexanedimethanol are copolymerized. It is desirable to make it. This is because strength and flexibility can be balanced. Preferable examples include polyester resins in which the acid component is composed of 10 to 30 mol% isophthalic acid and 70 to 90 mol% terephthalic acid, and the glycol component is composed of 30 to 50 mol% ethylene glycol and 50 to 70 mol% propanediol. be able to.

As the thermophysical properties of the polyester forming the resin layer, it is desirable that the glass transition point is in the range of 50 ° C. to 85 ° C., and the softening point is in the range of 100 ° C. to 200 ° C.
When the resin-coated steel sheet is stored and transported, it may be kept at a temperature of about 40 ° C. for a long time. Therefore, the glass transition point is preferably 50 ° C. or higher. On the other hand, a polyester polymer having a glass transition point of more than 85 ° C. has an increased softening point, and it is difficult to maintain the softening point in the range of 200 ° C. or less defined in the present invention.

  Moreover, the retort sterilization treatment for food cans may take 1 hour or more at a high temperature of 100 ° C. or higher, and is required to have heat resistance in a temperature range of 100 ° C. or higher. Therefore, the softening point defined in JIS K2425 is preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. On the other hand, the upper limit of the softening point is preferably 200 ° C. or less. When the softening point exceeds 200 ° C., the thermal fluidity of the resin is lowered, and the flexibility of the resin is insufficient in a process such as laminating with a steel plate or canning. Insufficient flexibility when laminating affects the adhesion to the steel sheet. Insufficient flexibility during can manufacturing suppresses deformation in the can height direction, causing resin damage and rupturing the can body. Cause.

  The polyester resin forming the resin layer preferably has a mass average molecular weight of 10,000 or more and 40,000 or less. Desirably, it is the range of 15000-20000. A polyester resin having a mass average molecular weight in such a range is excellent in the balance between processability and strength, and has a good deep drawability and adhesion after molding. By setting the molecular weight to 10,000 or more, the strength of the resin increases, and the resin follows the deformation without tearing during the deep drawing. Also in the subsequent retort treatment, delamination from the trim end or the like can be suppressed against the thermal shrinkage of the film formed in the upper layer. In addition, with respect to the impact resistance after canning, the occurrence of defects can be suppressed and good performance can be obtained. On the other hand, if the molecular weight exceeds 40,000, the strength of the resin becomes excessive, and conversely, flexibility may be impaired. By setting it to 40000 or less, the balance between strength and flexibility can be maintained.

The resin layer on at least one surface has a structure of two or more layers, and among the structures of two or more layers, the resin layer (a) in close contact with the steel sheet includes the following (A) in addition to the polyester resin as the main component: Preferably, it contains the components (b) and (c).
(I) Any one or more selected from the group consisting of polyamine resin, polyamidoamine resin, and polyamide resin: 1.0 to 50.0 mass%
(B) Epoxy resin: 0.5 to 30 mass%
(C) Metal alkoxide compound and / or metal chelate compound: 0.01 to 10 mass%
(A) One or more selected from the group consisting of polyamine resins, polyamide amine resins, and polyamide resins Polyamine resins, polyamide amine resins, and polyamide resins have a faster curing speed and form a tough film compared to melamine resins, etc. It is excellent in that it can be done. Because it has excellent curing characteristics compared to resin compositions made of polyester / melamine, epoxy / melamine, etc., cross-linking reaction between resins even in heat treatment of extremely short time (less than 1 second) such as heat fusion laminating. It becomes possible to polymerize. And while improving the intensity | strength and workability of a resin layer (a) significantly, the firm adhesiveness of a base material and an upper layer film can be obtained. For this reason, even in the groove processing portion for opening in which large deformation occurs, good coverage can be ensured because the deformation is followed without peeling from the base material and the upper layer.

Specific examples of the polyamine resin include diethylenetriamine, triethylenetriamine, and triethylenepentamine as the aliphatic amine, and isophoronediamine as the alicyclic polyamine. In addition, an epoxy resin or acrylonitrile may be added to an aliphatic polyamine or modified by reacting formaldehyde and phenol to improve workability, reduce irritation, or improve mechanical properties. Examples of the aromatic polyamine include metaphenylenediamine, diaminodiphenylsulfonic acid, and diaminodiphenylmethane. Commercially available products include EPICRON EXB-353 manufactured by DIC Corporation, Ancamine 2596 manufactured by Air Products Japan Co., Ltd., Ancamine 2605, and the like.

  The polyamide amine resin and the polyamide resin are compounds synthesized by, for example, a dehydration condensation reaction between fat and fatty acid and polyamine. Commercially available products include Sanyo Kasei Polyamide L-15-3, Polyamide L-45-3, Air Products Japan Co., Ltd. Ancamide 2137, Sunmide 330, Sunmide X-2000, and the like.

  The addition amount of any one or more selected from the group consisting of a polyamine resin, a polyamidoamine resin, and a polyamide resin is in the range of 1.0 to 50.0 mass%. If the addition amount is lower than 1.0 mass%, the curability is insufficient and the retort resistance is inferior, and if it exceeds 50.0 mass%, the workability may deteriorate. More preferably, it is the range of 3-30 mass%.

(B) Epoxy resin The epoxy resin mainly improves the adhesion of the resin layer (a). The type of the epoxy resin is not particularly limited. However, in recent years, bisphenol A type epoxy resins are concerned about endocrine disrupting action. Therefore, the resin is preferably free from such concerns and does not contain bisphenol A. It is preferable to use an epoxy resin. Examples of the epoxy resin that does not contain bisphenol A include novolak type epoxy resins and biphenyl type epoxy resins, and a novolak type epoxy resin is particularly preferable. Examples of the novolak type epoxy resin include a cresol novolak type and a phenol novolak type. As a commercial product of a novolak type epoxy resin, Epicron N-665, 670, 673, 680, 690, 695, 730, 740, 770, 865, 870 manufactured by DIC Corporation, manufactured by Dow Chemical Co., Ltd. XD-7855, ECN-1273, 1299 manufactured by Asahi Kasei Epoxy Co., Ltd. and the like. Examples of the biphenyl type epoxy resin include YL6121H and YX7399 manufactured by Mitsubishi Chemical Corporation.
The amount of epoxy resin added to the resin layer (a) is preferably in the range of 0.5 to 30 mass%. If the ratio of the epoxy resin is lower than 0.5 mass%, the effect of improving the adhesion is poor, and conversely, if it exceeds 30 mass%, the workability may be lowered. More preferably, it is the range of 5-25 mass%.

(E) A metal alkoxide compound and / or a metal chelate compound A metal alkoxide compound and / or a metal chelate compound is a polyester resin that is a main component of the resin layer (a), (a) a polyamine resin, a polyamidoamine resin, a polyamide. One or more selected from the group consisting of resins reacts with (b) an epoxy resin. A crosslinking reaction proceeds between the functional group of each resin and the metal alkoxide compound and / or metal chelate compound. This cross-linking reaction has a significantly faster curing rate compared to the case where there is no metal alkoxide compound and / or metal chelate compound, and as a result, excellent adhesion, workability, Retort resistance and corrosion resistance can be expressed. For example, existing laminated cans are baked at 180 ° C. or higher for several seconds to several minutes after laminating the film, and then the post-heating is used to cure the resin film to ensure the above various required performances. . However, in the present invention, the resin layer containing a metal alkoxide compound and / or a metal chelate compound is sufficiently cured by only heating for a short time of about 1 second when performing heat fusion lamination. The performance equal to or better than that after post-heating can be obtained. Therefore, the post-heating step in the manufacturing process is not necessary, and the manufacturing efficiency is greatly improved. In addition, carbon dioxide emissions can be reduced, which can be a very useful technique in practice. Furthermore, by incorporating a metal into the film, the strength of the film is improved, and as a result, impact resistance and corrosion resistance are greatly improved. For the above reasons, it is preferable that the resin layer (a) further contains a metal alkoxide compound and / or a metal chelate compound.
Examples of the metal alkoxide compound and / or metal chelate compound include alkoxide metal compounds such as aluminum, titanium, tin, and zirconium, and metal chelate compounds in which acetoacetic acid is coordinated to the metal. Among these, it is preferable to use a titanium alkoxide compound and / or a titanium chelate compound.
The addition amount of the metal alkoxide compound and / or the metal chelate compound is preferably in the range of 0.01 to 10 mass%. If it is less than 0.01 mass%, the expected effect such as fast curability cannot be obtained. Conversely, if it exceeds 10 mass%, the resin film becomes hard and the workability becomes inferior. Sometimes it causes gelation. More preferably, it is the range of 0.1-7 mass%.

The adhesion amount of the resin layer (a) serving as the adhesion layer to the steel sheet is preferably specified in a range of 0.1 g / m ² or more and 3.0 g / m ² or less. If it is less than 0.1 g / m < ² >, the steel plate surface cannot be coated uniformly, and the film thickness may become non-uniform. When a modifier is added, the adhesion amount of the modifier fluctuates, and a stable function cannot be obtained, which is inappropriate. On the other hand, if it exceeds 3.0 g / m ² , the cohesive strength of the resin becomes insufficient, and the strength of the resin layer may be reduced. As a result, at the time of can manufacturing, the resin layer is agglomerated and broken to peel off the film, and the can body portion is torn from that point. Therefore, the adhesion amount is preferably in the range of 0.1 g / m ² m to 3.0 g / m ^2, more preferably in the range of 0.5 g / m ^{2 to} 2.5 g / m ^2. .

Furthermore, by adding colorants such as dyes and pigments to the resin layer (a), the underlying steel plate can be concealed and various colors unique to the resin can be imparted. For example, by adding carbon black as a black pigment, it is possible to conceal the steel color of the base and to impart a high-class feeling of black to food cans. In addition, in this application, when adding a coloring agent in the resin layer (a), the total of components, such as outer division (polyester resin, (i)-(iii) related to resin performance, is 100 parts by mass. In parts by weight of colorant (PHR)). That is, the amount of carbon black added is desirably 5 PHR or more and 40 PHR or less. If it is less than 5 PHR, the blackness is insufficient, the color tone of the base steel cannot be concealed, and a high-quality design may not be imparted. On the other hand, even if it exceeds 40 PHR, the blackness does not change, so the effect of improving the design is not obtained, and the structure of the polyester resin becomes brittle, so that the resin layer may be easily broken during can manufacturing. is there. By making the addition amount in the range of 5 PHR to 40 PHR, it is possible to achieve both design properties and other required characteristics.
The particle size of carbon black is preferably in the range of 5 to 50 nm, but in view of dispersibility and color developability in the polyester resin, the range of 5 to 30 nm is more preferable.

  In addition to the black pigment, by adding a white pigment, the steel luster of the base can be concealed, the printed surface can be sharpened, and a good appearance can be obtained. As a pigment to be added, it is necessary that an excellent design property can be exhibited after container molding. From such a viewpoint, inorganic pigments such as titanium dioxide can be used. Since the coloring power is strong and rich in spreadability, it is preferable because a good design property can be secured even after container molding. The amount of titanium dioxide added is desirably 5 to 40 PHR with respect to the target resin layer. If it is 5 PHR or more, sufficient whiteness can be obtained and good design properties can be secured. On the other hand, even if it is added in excess of 40 PHR, the whiteness is saturated, so it is desirable to make it 40 PHR or less for economic reasons. More preferably, it is the range of 10-30 PHR.

  When a bright color is desired on the container surface, use of an azo pigment is also suitable. Although it is excellent in transparency, it has a strong coloring power and a high spreadability, so that a bright appearance can be obtained even after the container is molded. As an azo pigment that can be used in the present invention, the color index (abbreviation: CI) is at least one of Pigment Yellow 12, 13, 14, 16, 17, 55, 81, 83, 139, 180, and 181. One type can be mentioned. In particular, from the viewpoints of vividness of color tone (bright color) and bleeding resistance in retort sterilization environment (inhibition ability against the phenomenon that pigments are deposited on the film surface), it has a large molecular weight and is soluble in PET resin. A poor pigment is desirable. For example, C.I. having a benzimidazolone structure having a molecular utilization of 700 or more. I. Pigment Yellow 180 is more preferably used.

  The addition amount of the azo pigment is desirably 10 to 40 PHR with respect to the target resin layer. If the addition amount is 10 PHR or more, it is preferable because coloring is excellent. When the color is 40 PHR or less, the transparency becomes high and the color tone is rich.

  By adding 5 PHR or more of a corrosion inhibitor in the resin layer (a), metal elution can be suppressed even when defects occur in the resin layer and the steel sheet surface is exposed. As the corrosion inhibitor, substances having confirmed food safety such as ascorbic acid, tocophenol and carotenoid having a reducing action can be used. These substances have an effect of suppressing metal anodic dissolution by being preferentially oxidized in the resin defect portion.

  Moreover, adding a conductive polymer in the range of 0.1 to 30 mass% in the resin layer (a) is also effective in suppressing the elution of iron in the defective portion. As the conductive polymer, a heterocyclic conjugated system or a hetero atom-containing conjugated π-conjugated polymer is suitable. Since the π-conjugated polymer is at a noble potential with respect to the base steel plate, it undergoes a reduction reaction at the interface with the base steel plate. As the π-conjugated polymer is reduced, the base steel plate is oxidized, and a dense passive film is formed on the surface of the base steel plate. On the other hand, on the surface side in contact with air, the π-conjugated polymer is oxidized by air and returns to the original state. By repeating such a redox reaction, a passive film having a high barrier property is formed on the surface of the underlying steel sheet. Even if a film defect such as a scratch occurs, the passivation is promoted, so that the progress of corrosion starting from the defective portion is suppressed. As the π-conjugated polymer, polypyrrole, polythiophene, polyaniline and the like can be used, and among them, polyaniline can be most preferably used.

  In addition, in order to further improve the water resistance of the resin layer (a), it is preferable to include a hydrophobic polyol resin derived from a fatty acid in a range of 5 mass% to 15 mass%. Examples of the hydrophobic polyol resin include dimer acid polyol, polydiene polyol, polyisoprene polyol and the like. Among them, by applying a long-chain alkyl group having 20 to 50 carbon atoms, the ester bond portion can be shielded from water, and film peeling in a humid environment such as retort treatment can be effectively prevented.

  The addition amount of the hydrophobic polyol resin is desirably 5 mass% or more and 15 mass% or less. If it is less than 5 mass%, sufficient water resistance cannot be obtained, and if it exceeds 15 mass%, the surface free energy of the polyester resin is excessively lowered, and thus the adhesion between the polyester film and the steel sheet may be inhibited. is there. By defining it in the range of 5 mass% or more and 15 mass% or less, both water resistance and adhesion can be achieved. More preferably, it is the range of 7 mass% or more and 10 mass% or less.

  Moreover, polyester polyol can be added in the range which does not inhibit hydrophobicity. In this case, the range of 50% or more of the total polyol mass is suitable as the hydrophobic polyol. As the polyester polyol, glycol components such as 1,6-hexanediol and neopentyl glycol, and esters such as maleic acid, adipic acid, oleic acid, and dimer acid thereof can be used. Particularly preferred are polyester polyols using dimer acid of oleic acid.

Next, the polyester resin layer (b) formed on the upper layer of the resin layer (a) will be described.
The polyester resin layer (b) formed on the upper layer of the resin layer (a) is formed from a polyester film (hereinafter sometimes simply referred to as a polyester film). The polyester film is a polyester mainly composed of ethylene terephthalate and / or ethylene naphthalate from the viewpoint of improving the taste characteristics after retort and suppressing the generation of abrasion powder in the lid making process. Is desirable. That is, the polyester mainly composed of ethylene terephthalate and / or ethylene naphthalate is a polyester in which 93 mass% or more of the structural units of the polyester are ethylene terephthalate units and / or ethylene naphthalate units. More preferably, it is 95 mass% or more. Even if a metal can is filled with food for a long time, it is desirable because it has good taste characteristics.
On the other hand, other dicarboxylic acid components and glycol components may be copolymerized as long as the taste characteristics are not impaired. Examples of the dicarboxylic acid component include aromatics such as diphenylcarboxylic acid, 5-sodium sulfoisophthalic acid, and phthalic acid. Dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, aliphatic dicarboxylic acid such as fumaric acid, aliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid, oxycarboxylic acid such as p-oxybenzoic acid Etc.
On the other hand, examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentyl glycol, finger ring glycols such as cyclohexanedimethanol, and aromatics such as bisphenol A and bisphenol S. Examples include glycol, diethylene glycol, and polyethylene glycol. In addition, since bisphenol A of aromatic glycol is concerned about endocrine disrupting action, it is desirable not to use it as a glycol component. These dicarboxylic acid components and glycol components may be used in combination of two or more.
Moreover, as long as the effect of this invention is not inhibited, you may copolymerize polyfunctional compounds, such as trimellitic acid, trimesic acid, a trimethylol propane.

  The polyester resin layer (b) forming the upper layer of the resin layer (a) has a particle: area-converted average particle diameter of 0.005 to 5.0 μm, and a relative standard deviation represented by the formula (1) is 0.5. It is preferable that 0.005 to 10 mass% of particles having a major axis / minor axis ratio of 1.0 to 1.2 and a Mohs hardness of less than 7 is contained.

The particles in the polyester resin layer (b) used in the present invention are not particularly limited in terms of composition regardless of organic or inorganic.
From the viewpoint of wear resistance, workability, taste characteristics, etc., the area-converted average particle diameter is preferably 0.005 to 5.0 μm. More preferably, it is 0.01-3.0 micrometers.
Moreover, it is preferable that relative standard deviation shown by following formula (1) is 0.5 or less from points, such as abrasion resistance. More preferably, it is 0.3 or less.

The major axis / minor axis ratio of the particles is preferably 1.0 to 1.2 from the viewpoint of wear resistance and the like. The Mohs hardness is preferably less than 7 from the viewpoints of protrusion hardness, wear resistance, and the like. And in order to fully express these effects, it is preferable to contain 0.005-10 mass% of particles which consist of the above.

Specifically, examples of the inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, and clay. Among them, the one in which the functional group on the particle surface reacts with the polyester constituting the polyester film to generate a carboxylic acid metal salt is preferable. Specifically, the one having 10 ⁻⁵ mol or more per 1 g of the particles is polyester. It is preferable in terms of affinity with the polyester constituting the film, wear resistance, and the like, and more preferably 2 × 10 ⁻⁵ mol or more.
As the organic particles, various organic polymer particles can be used. As the type, particles having any composition may be used as long as at least a part thereof is insoluble in the polyester constituting the polyester film. Absent. In addition, polyimide, polyamideimide, polymethyl methacrylate, formaldehyde resin, phenol resin, cross-linked polystyrene, silicone resin, etc. can be used as the material of such particles, but they have high heat resistance and a uniform particle size distribution. Particularly preferred are vinyl-based crosslinked polymer particles that are easy to obtain.

Such inorganic particles and organic polymer particles may be used alone, but preferably used in combination of two or more, and further function by combining particles having different physical properties such as particle size distribution and particle strength. A highly reliable polyester resin layer (b) can be obtained.
In addition, other particles such as various amorphous external additive particles and internal precipitation particles, or various surface treatment agents may be added as long as the effects of the present invention are not hindered.

  Furthermore, from the viewpoint of heat resistance and taste characteristics, the polyester film is preferably a biaxially stretched polyester film. The biaxial stretching method may be simultaneous biaxial stretching or sequential biaxial stretching, but the stretching conditions and heat treatment conditions are specified, and the refractive index in the thickness direction of the film is 1.50 or more. Is preferable in terms of improving the laminating property and moldability. Furthermore, when the refractive index in the thickness direction is 1.51 or more, particularly 1.52 or more, the plane orientation coefficient is controlled within a specific range in order to achieve both formability and impact resistance even if there is some variation during lamination. This is preferable because it can be performed.

  In addition, the biaxially stretched polyester film preferably has a carbonyl relaxation time of 270 msec or more in structural analysis by solid high-resolution NMR in terms of workability and impact resistance during can manufacturing. More preferably, it is 280 msec or more, Most preferably, it is 300 msec or more. As long as the effects of the present invention are not hindered, other particles, for example, various amorphous externally added particles, internally precipitated particles, or various surface treatment agents may be used.

As a technique for suppressing retort whitening, it is also effective to control the degree of residual orientation of the polyester resin layer (b) formed on the upper layer of the resin layer (a) to be adhered to a range of 2% to 30%. Here, the residual orientation degree is a value obtained by an X-ray diffraction method and is defined as follows.
(1) For the oriented polyester resin (or oriented polyester film) before lamination and the resin (or film) after lamination, the X-ray diffraction intensity is measured in the range of 2θ = 20 to 30 °.
(2) The X-ray diffraction intensity at 2θ = 20 ° and 2θ = 30 ° is connected by a straight line to be a base line.
(3) The height of the highest peak appearing in the vicinity of 2θ = 22 to 28 ° is measured from the baseline.
(4) When the height of the highest peak of the film before lamination is P1, and the highest peak of the film after lamination is P2, P2 / P1 × 100 is the residual orientation degree (%).

  As a result of intensive studies by the present inventors, it has been found that the amount of water vapor that permeates through the resin layer decreases as the residual orientation degree increases. By making the residual orientation degree 2% or more, the amount of water vapor reaching the interface with the steel sheet is reduced, and the effect of adding any one or more selected from the group consisting of the aforementioned polyamine resin, polyamidoamine resin, and polyamide resin In addition, retort whitening can be completely suppressed. As the residual orientation increases, the amount of permeated water vapor tends to decrease and the resistance to retort whitening becomes good, while the flexibility and elongation characteristics of the resin decrease. When the residual orientation degree exceeds 30%, follow-up to the can manufacturing process becomes insufficient, and film peeling or material tearing occurs. By adjusting the degree of residual orientation to a range of 2% to 30%, both retort whitening resistance, resin flexibility, and moldability can be achieved.

The total thickness of the resin layer (a) of the present invention and the polyester resin layer (b) forming the upper layer is preferably 5 μm or more and 100 μm or less, more preferably 8 μm or more and 50 μm or less, and particularly 10 μm or more and 25 μm. The following range is preferable. The preferred thickness of each of the resin layers (a) and (b) is not particularly limited, but the preferred thickness of the resin layer (a) is specific gravity to a preferred adhesion amount (0.1 to 3.0 g / m ² ). You can understand if you apply. That is, since the specific gravity of the resin is often about 1, in that case, 0.1 μm to 3.0 μm is preferable. When the specific gravity is changed by adding a colorant or the like, the specific gravity and blending ratio of the substance are changed. The film thickness calculated in consideration is preferable. The preferable film thickness range of the resin layer (b) may be that the film thickness of the resin layer (a) is subtracted.

Next, a manufacturing method as an example of the resin-coated steel sheet according to the present invention will be described.
In the resin-coated steel sheet of the present invention, the polyester resin layer (b) may be formed on the steel sheet after forming the resin layer (a) composed of the above. Here, the resin layer (a) is made of polyester. The resin layer (b) is formed on the surface of the polyester film. Next, the polyester film on which the resin layer (a) is formed is laminated on the steel plate surface so that the resin layer (a) exists at the interface between the steel plate and the polyester film.
First, a method for forming the resin layer (a) on the polyester film surface will be described. The polyester resin specified in the present invention is dissolved in an organic solvent to form a coating solution. Next, the coating liquid is applied to the surface of the polyester film and dried at the time of film formation of the polyester film or after film formation. The formation method is not particularly limited, but the method described above is preferable because it is suitable for the purpose and application of the present invention.

Examples of the organic solvent for dissolving the polyester resin defined in the present invention include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and cyclohexanone, and ester solvents such as ethyl acetate and ethylene glycol monoethyl ether acetate. One or more of these can be appropriately selected and used.
In addition, additives such as polyamine resin, polyamide amine resin, polyamide resin, epoxy resin, metal alkoxide compound, metal chelate compound, colorant, carbon black, and azo pigment as defined in the present invention are dissolved in an organic solvent. Alternatively, it is desirable to use in a dispersed manner. In this case, it is preferable to use a dispersant in combination because the uniformity of the additive can be imparted.

  The coating solution for the resin layer (a) produced as described above is applied to the film surface and dried at the time of film formation of the polyester film or after film formation.

  As a method for applying the coating liquid for the resin layer (a) to the polyester film, known coating means such as a roll coater method, a die coater method, a gravure method, a gravure offset method, a spray coating method can be applied. The coating method is most preferred. As drying conditions after application of the coating liquid, 80 to 170 ° C. for 20 to 180 seconds, particularly 80 to 120 ° C. for 60 to 120 seconds are preferable.

Next, the polyester film formed by the above method and formed with the resin layer (a) is laminated on the surface of the steel sheet so that the resin layer (a) is in close contact with the steel sheet.
In the present invention, for example, a method is used in which a steel sheet is heated to a certain temperature or higher with a heating device, and a polyester film is brought into contact with the steel sheet using a pressure-bonding roll (hereinafter referred to as a laminate roll) and heat-sealed. be able to. Details of the lamination conditions will be described below.

  The temperature of the steel sheet at the start of heat fusion is in the range of + 5 ° C. to + 30 ° C., based on the higher value of the melting point of the polyester film or the softening point of the resin layer (a) (polyester resin) to be adhered. It is desirable to do. In order to ensure the interlaminar adhesion of the steel sheet-resin layer (a) -polyester film by the heat fusion method, the heat flow of the resin at the adhesion interface is necessary. By setting the temperature of the steel sheet to a temperature range of + 5 ° C. or higher, based on the higher value of the melting point of the polyester film or the softening point of the resin layer (a) to be adhered, the resin between the layers is thermally fluidized. In addition, the wettability at the interface becomes good and excellent adhesion can be obtained. On the other hand, even if the temperature exceeds + 30 ° C., further improvement of adhesion cannot be expected, the film is excessively melted, and problems such as surface roughness due to embossing of the surface of the lami roll and transfer of the melt to the pressure roll arise. This is because there are concerns.

  The heat history received by the film at the time of lamination is preferably 5 msec or more at the higher temperature of the melting point of the polyester film or the softening point of the resin layer (a) to be adhered, whichever is higher. . This is because wetting at the interface is good. In addition, the wettability improves with increasing time, but when it exceeds 40 msec, almost constant performance is exhibited and the effect is not recognized. Since there is a possibility of causing a decrease in productivity, it is desirable to set it to 40 msec or less. Therefore, the range of 5 to 40 msec is preferable.

  In order to achieve such lamination conditions, in addition to high-speed operation of 150 mpm or more, cooling during heat sealing is also necessary. For example, when the laminate roll is an internal water-cooled type, the polyester film and the resin layer (a) to be adhered can be prevented from being excessively heated by passing the cooling water. Furthermore, since the thermal history of a polyester film and the resin layer (a) to adhere | attach can be controlled by changing the temperature of cooling water, it is suitable.

The pressurization of the laminate roll is preferably 9.8 to 294 N / cm ² (1 to 30 kgf / cm ² ) as the surface pressure. When the temperature is less than 9.8 N / cm ² , even if the temperature at the start of heat fusion is not less than the melting point of the film + 5 ° C. and sufficient fluidity is ensured, the force to spread the resin on the steel surface is sufficient. Since it is weak, sufficient coverage cannot be obtained, and as a result, performance such as adhesion and corrosion resistance may be affected. On the other hand, if it exceeds 294 N / cm ^2, there is no inconvenience in the performance of the laminated steel sheet, but it is uneconomical because the force applied to the laminating roll is large and the strength of equipment is required, resulting in an increase in the size of the apparatus.

  Next, the easy open can lid and the manufacturing method thereof according to the present invention will be described with reference to the drawings.

  FIG. 5 is a cross-sectional view of the opening groove portion formed in the can lid, showing one embodiment of the easy open can lid of the present invention. In this embodiment, as shown in FIG. 5, the radius (R) is 0.1 to 0.5 mm on the front surface 1a and the back surface 1b of the can lid 1 having the thickness t0 and having the resin film layers 4 on both sides. An opening groove having a curved cross section within a range where the slope 3 (Tp) of the cross section is 1.5 or less and the thickness (ts) of the thinnest portion 2a is 0.035 to 0.075 mm. 2 is formed. Here, the inclination of the cross section (Tp) is the inclination of the tangent or the straight line of the curved portion in the opening groove cross section, and indicates the maximum value (Tanθ) of the inclination. When the opening groove cross-sectional shape is only a curved portion, the maximum slope of the tangent (Tan θ) is obtained, and when the opening groove cross-section is included, the slope of the straight portion (Tan θ) is obtained.

  Since the curved opening groove 2 having the radius (R) described above is formed on the front surface 1a and the back surface 1b of the can lid 1, it can be opened to such an extent that even a child or an elderly person can easily open the can. The can force can be stably reduced, and the occurrence of impact breakage is prevented.

  The cross-sectional shape of the opening groove is composed of a curve and / or a straight line. For example, the cross section of the opening may be any curved line and / or straight line as long as the slope (Tp) is 1.5 or less. A combination of a plurality of curves having different curvatures or a cross section in which straight lines are combined may be used. However, it is easy to produce a curve with a single curvature as a mold for processing, and its practicality is high.

  In addition, when the cross section of the opening is composed of a combination of a curve and a straight line, it is easy to manufacture a shape composed of a curve having a single curvature and a tangent line of the curve, which is highly practical.

  Here, if the radius (R) of the opening groove 2 is less than 0.1 mm, it becomes difficult to form the opening groove 2 in the can lid panel without damaging the resin layer. On the other hand, when the radius (R) of the opening groove 2 exceeds 0.5 mm, the opening groove portion is extended in the width direction, and the amount of opening groove processing is excessively increased, so that processing flaws are generated. By setting the radius (R) of the opening groove 2 in the range of 0.1 mm to 0.5 mm, the opening groove can be formed without damaging the resin layer. More preferably, it is the range of 0.2 mm-0.3 mm.

  If the thickness of the thinnest portion 2a of the opening groove 2 is less than 0.035 mm, the resin layer may be damaged during the molding process, and the can lid panel may be broken. When such a can body with a can lid attached is dropped or the can body receives an impact from the outside, there is a risk that the opening portion is broken. On the other hand, if the thickness of the thinnest part 2a of the opening groove 2 exceeds 0.075 mm, the thinnest part is difficult to tear, and a problem that a large can opening force is required arises.

  Furthermore, in the present invention, the value of the ratio (= ts / t0) of the plate thickness ts of the thinnest portion 2a of the opening groove 2 and the plate thickness t0 of the resin-coated metal plate is defined in a range of 0.1 or more. The opening force (pop value / tier value) correlates with the thinnest part thickness ts of the opening groove and does not depend on the thickness t0 of the metal plate. Even if the value of t0 changes, the value of ts at which the can openability is good is substantially constant. Therefore, if t0 increases, the score processing amount up to the thinnest part ts will increase.

  If the score processing amount for the resin-coated metal plate increases, the amount of stress and strain applied to the resin layer increases and the risk of damage increases, so care must be taken in selecting t0. As a result of investigating the influence of the values of t0 and ts on the performance by the present inventors, by defining the value of ts / t0 within a range of 0.1 or more, the score processing amount is limited, and the resin layer It was found that damage can be reliably suppressed. Therefore, the ratio of the thickness of the thinnest part of the opening groove to the thickness of the resin-coated metal plate is set to 0.1 or more.

  Therefore, the cross-sectional shape of the opening groove formed on the front and back surfaces of the can lid is configured such that the cross-sectional shape of the open groove is a curve and / or a straight line (preferably an arc curve having a radius of 0.1 to 0.5 mm). The thickness of the thinnest part is 0.035 to 0.075 mm, and the ratio of the thickness of the thinnest part of the groove for opening to the thickness of the resin-coated metal plate is in the range of 0.1 or more.

  Furthermore, the inclination (Tp) of the cross section is defined in a range of 1.5 or less. Here, the inclination of the opening groove portion means the maximum inclination in the opening groove section as described above. When the opening groove cross-sectional shape is only a curve, it is the maximum inclination of the tangent. By prescribing this value to 1.5 or less, the shear stress in the film can be controlled within an appropriate range during the opening groove processing. When it exceeds 1.5, the shear stress becomes excessive, and the resin is torn starting from the location where the maximum stress is generated.

  The can lid of the present invention uses a pair of upper and lower molds composed of a curved surface with a tip radius of 0.1 mm to 0.5 mm or a curved line with a radius of 0.1 mm to 0.5 mm, and the thickness of the thinnest part. Can be formed by pressing a can lid panel having a resin layer formed on both sides so that the thickness is in the range of 0.035 to 0.075 mm. The reason why the curved mold is made to have the above-mentioned dimension and shape is to form an opening groove having the above-mentioned dimension and shape in the can lid, and the reason for limiting the dimension and shape of the opening groove is as described above.

  Also, when press-molding a resin-coated metal plate using a mold, the entire processing portion of the resin-coated metal plate is pressed while maintaining a state in contact with the mold, that is, the mold and the resin. It is desirable to maintain the state in which the coated metal plate is always in contact without leaving in the opening groove processing region. When a region where the mold and the resin-coated metal plate are not in contact with each other is generated, the contact pressure rapidly changes at the contact / non-contact boundary. Due to the sudden change in the external force distribution, the film in the vicinity of the boundary is greatly deformed, and is easily damaged. If the contact is maintained, the change in the contact pressure distribution is small, and film deformation and damage are suppressed.

  When a can lid panel is pressed, if a lubricant is used, the frictional force between the mold and the resin is reduced, so the shear stress generated in the resin is reduced, and at the interface between the resin and the steel plate. Generation | occurrence | production of peeling can be suppressed.

Examples of the present invention will be described below.
First, a polyester film formed on the upper layer of the resin layer (a) is manufactured. A polyester resin obtained by polymerizing a diol component and a dicarboxylic acid component in the ratios shown in Tables 1 and 2 is dried, melted, extruded, cooled and solidified on a cooling drum to obtain an unstretched film, and then biaxially stretched and heated. The biaxially oriented polyester film was obtained by fixing.

  Next, the resin layer (a) is formed on the surface of the polyester film prepared above. Various additives such as a resin mainly composed of a polyester resin and a polyamidoamine resin were dissolved in a mixed solvent of toluene and methyl ethyl ketone at a mass ratio shown in Tables 1 and 2 to prepare a coating solution. This coating solution was applied to one side of the polyester film obtained above using a gravure roll coater and dried to adjust the amount of the resin layer after drying. The drying temperature was in the range of 80 to 120 ° C. Table 1 shows the resin layer components on the inner side of the can lid, and Table 2 shows the resin layer components on the outer side of the can lid.

As the steel plate, a chrome plated steel plate was used. A steel sheet having a thickness of 0.18 mm and a width of 977 mm that had been subjected to cold rolling, annealing, and temper rolling was manufactured by degreasing and pickling, followed by chrome plating. Chromium plating was performed by chromium plating in a chromium plating bath containing CrO ₃ , F ⁻ , SO ₄ ²⁻ , intermediate rinsing, and then electrolyzed with a chemical conversion treatment solution containing CrO ₃ and F ⁻ . At this time, electrolysis conditions adjusted to metallic chromium adhering amount and chromium hydroxide deposition amount (current density, the quantity of electricity, etc.), respectively Cr terms was adjusted to ^{120mg / m 2, 15mg / m} 2.

Next, using the laminating apparatus shown in FIG. 4, the chrome-plated steel sheet 5 obtained above is heated by the steel sheet heating apparatus 6, and is laminated on one side of the chrome-plated steel sheet 5 by the laminating roll 7 and on the inner surface side of the container after container forming. As a polyester film, the film 8a prepared from Table 1 is laminated (heat fusion), and on the other side, the film 8b prepared from Table 2 is laminated (heat fusion) as a polyester film that becomes the outer side of the container after container molding. ) Then, water cooling was performed with the steel plate cooling device 9 to produce a resin-coated metal plate. FIG. 6 shows a cross-sectional structure of the resin-coated metal plate of the present invention.
The laminating roll 7 was an internal water-cooling type, and cooling water was forcibly circulated during lamination to cool the film during bonding. When laminating the film on the steel plate, the time during which the film temperature at the interface in contact with the steel plate was equal to or higher than the melting point of the film was set in the range of 1 to 20 msec.

For the resin-coated steel sheet obtained by the above method, a pair of molds having the shape defined in the present invention is used, and the thickness of the thinnest part falls within the range of 0.035 to 0.075 mm. Thus, the can lid panel was subjected to press working, and the surface was subjected to opening groove processing and bead processing to prepare specimens of easy open can lids within the scope of the present invention shown in Table 3. The processing speed was set to 1.0 cm / min. For comparison, a specimen in which the structure and characteristics of the resin film, the radius of the opening groove of the curved mold, and / or the thickness of the thinnest part is out of the scope of the present invention with respect to the chromium-plated steel sheet. , Together.
Here, the cross-sectional structure of the opening groove of the embodiment is shown in FIGS. 7 to 11, the cross section of the can lid is symmetrical with respect to the center line of the opening groove. However, the present invention is not limited to this, and even when it is not symmetrical, the same effects can be obtained within the technical scope of the present invention. The fragment structure of the opening groove in FIG. 12 is a comparative example in which the inclination (Tp) is off.

Measurement and evaluation of the can opening force (pop value, tear value) and the soundness, impact resistance, and retort whitening resistance of the above-described specimens of the present invention and comparative specimens by the following methods. did. Moreover, about the characteristic of the resin layer which has on the steel plate obtained by the above method, it measured and evaluated by the following method, respectively. The following (1) and (2) were measured at the film stage before lamination.
(1) Measurement of particle size ratio, area-converted average particle size, number average particle size, particle size and calculation of relative standard deviation σ Particles are blended with polyester, cut into ultra-thin pieces with a thickness of 0.2 μm, and transmitted. At least 50 particles were observed with a scanning electron microscope and the particle size was measured. The calculation formulas for the relative standard deviation σ and the number average particle diameter are as follows.

(2) Measurement of Mohs hardness Prepare a standard ore in the order of finishing in a smooth flat surface with a diamond or a grindstone. If each surface is aligned and rubbed between the particles, the lower reference ore is scratched and the upper reference ore is not scratched, the hardness of the particles is between the two reference ores It was.
(3) Can openability (pop value)
Using a tensile tester, the tab attached to the can lid was raised at a constant speed and evaluated by the maximum peak value at the first stage when the lid opening started to open.
(About the score)
◎: Less than 15 (N) ○: 15 (N) or more, less than 20 (N) Δ: 20 (N) or more, less than 25 (N) ×: 25 (N) or more (4) Can openability (tier value)
The tear can value was evaluated based on the initial maximum peak value observed when the tab was raised to an angle of 90 degrees with the lid surface and then pulled up in a direction perpendicular to the lid surface.
(About the score)
◎: Less than 30 (N) ○: 30 (N) or more, less than 40 (N) Δ: 40 (N) or more, less than 50 (N) ×: 50 (N) or more (5) Evaluation of damage degree of resin film (energization test)
Using a 3% potassium chloride solution as an electrolyte, a specimen (can lid) as an anode, and a platinum electrode as a cathode, the current value after energization for 4 seconds at an applied voltage of 6.2 V was measured and evaluated.
A: Less than 0.001 (mA) B: 0.001 (mA) or more, less than 0.01 (mA) Δ: 0.01 (mA) or more, less than 0.1 (mA) x: 0.1 (mA) or more (6) Impact resistance Ten test pieces (can lids) were wound and sealed around a can body filled with tap water. The can was dropped on a PVC tile floor from a height of 1.0 m with the lid facing downward, and the can was evaluated by the presence or absence of impact destruction when an impact force was applied.
(About the score)
○: No damage to the grooved part for opening ×: Damaged to the grooved part for opening (7) After filling normal temperature tap water in the retort whitening-resistant can, the specimen of the present invention and the specimen for comparison The lid which is is tightened and sealed. Thereafter, the lid was placed face down in a retort sterilization furnace, and retort treatment was performed at 125 ° C. for 90 minutes. After the treatment, the change in the appearance of the outer surface of the bottom of the can was visually observed.
(About the score)
◎: No change in appearance ○: Faint cloudy appearance △: Appearance clouded (whitening occurred)
X: Appearance is remarkably cloudy (remarkable whitening occurs)
Table 4 shows the results obtained as described above.
(8) Resin adhesion of opening grooved portion The grooved portion for opening formed on both surfaces of the can lid was visually observed to evaluate the adhesive state of the resin layer.
(About the score)
◎: No abnormality ○: Slight film lift is observed in a part of the groove processed part ×: Film lift is recognized in the groove processed part

  From Table 4, according to the example of the present invention, when the groove for opening is formed in the can lid made of the steel plate having the resin layers formed on both sides, the plating layer and the resin coating layer formed on both sides of the can lid It is possible to obtain an easy-open can lid having excellent openability that does not require repair coating due to damage and can maintain a good color tone even after retort processing.

  It is a material suitable for container use, mainly for food canned lids.

DESCRIPTION OF SYMBOLS 1 Can lid 2 Opening groove 3 Inclination 4 Resin layer 5 Steel plate (chromium plated steel plate)
6 Steel strip heating device 7 Laminate roll 8a, 8b Film 9 Steel strip cooling device 10 Processing tool 11 Cover plate

Claims (11)

An opening groove is formed on both sides of a can lid made of a resin-coated steel plate, and an easy open can lid made of a resin-coated steel plate that can be opened by breaking the opening groove.
The resin-coated steel sheet has a resin layer mainly composed of polyester on both surfaces, and the resin layer on at least one surface has a structure of two or more layers, and the resin that adheres to the steel plate among the structures of two or more layers The layer (a) contains 1.0 to 50.0 mass% of any one or more selected from the group consisting of (i) a polyamine resin, a polyamidoamine resin, and a polyamide resin,
The opening groove is composed of the following: an easy open can lid made of a resin-coated steel sheet.
(A) The cross-sectional shape of the opening groove is constituted by a curve and / or a straight line. (B) The inclination (Tp) in the cross-sectional shape of the opening groove is 1.5 or less. (C) The thickness of the thinnest portion of the opening groove. 0.035 mm or more and 0.075 mm or less (D) The ratio of the thickness of the thinnest part of the opening groove to the thickness of the resin-coated steel sheet is 0.1 or more   2. The easy-open can lid made of a resin-coated steel plate according to claim 1, wherein a cross-sectional shape of the opening groove is an arc curve having a radius of 0.1 mm to 0.5 mm.   The said resin layer (a) contains 0.5-30 mass% of (ii) epoxy resin further, The easy open can lid | cover made from the resin-coated steel plate of Claim 1 or 2 characterized by the above-mentioned.   The said resin layer (a) contains 0.01-10 mass% of (c) metal alkoxide type compound and / or a metal chelate compound further, As described in any one of Claims 1-3 characterized by the above-mentioned. Easy-open can lid made of resin-coated steel plate. The resin-coated steel sheet easy according to any one of claims 1 to 4, wherein the adhesion amount of the resin layer (a) is 0.1 g / m ² or more and 3.0 g / m ² or less. Open can lid.   The resin layer (a) contains a colorant, and the resin-coated steel plate easy open can lid according to any one of claims 1 to 5.   The resin layer (a) contains 5 PHR or more of a corrosion inhibitor, The easy-open can lid made of a resin-coated steel sheet according to any one of claims 1 to 6.   The resin layer (a) contains 0.1 to 30 mass% of a conductive polymer, and the resin-coated steel plate easy open can lid according to any one of claims 1 to 7. The polyester resin layer (b) that forms the upper layer of the resin layer (a) is formed of a polyester film, and the polyester film is composed of 93% by mass or more of the structural units of the polyester in units of ethylene terephthalate units and / or ethylene naphthalate units. And the average particle diameter in terms of area is 0.005 to 5.0 μm, the relative standard deviation represented by the formula (1) is 0.5 or less, and the major axis / minor axis ratio of the particles is 1.0 to The easy-open can lid made of a resin-coated steel sheet according to any one of claims 1 to 8, further comprising 0.005 to 10 mass% of particles having a Mohs hardness of less than 7 in 1.2.
  For a can lid panel made of a steel plate coated with a resin layer, a pair of upper and lower molds composed of a curved surface with a radius of 0.1 mm to 0.5 mm or a curved line with a radius of 0.1 mm to 0.5 mm is used. And the can lid according to any one of claims 1 to 9 is manufactured by performing press molding so that the thickness of the thinnest part falls within a range of 0.035 mm to 0.075 mm. To manufacture easy-open can lid made of resin-coated steel sheet.   When press-molding a resin-coated metal plate using the mold according to claim 10, the entire processed part of the resin-coated steel sheet is pressed while maintaining a state in contact with the mold. Manufacturing method of easy-open can lid made of resin-coated steel sheet.