JP4654617B2 - Reseal can - Google Patents

Description

  The present invention relates to a resin-coated metal plate, and more particularly, excellent processing capable of withstanding high-level processing while preventing turbidity due to elution of low molecular weight components even when subjected to high temperature retort sterilization or the like. TECHNICAL FIELD The present invention relates to a resin-coated metal plate provided with properties, corrosion resistance, and the like, a metal can formed by molding the resin-coated metal plate, and a lid for the metal can.

  Resin-coated metal plates coated with a thermoplastic polyester film on metal materials have long been used as can-making materials. Such resin-coated metal plates are subjected to drawing processing, drawing or ironing processing, etc. It is also well known to make seamless cans for filling.

  As such a resin-coated metal plate, a polyester or copolymer polyester mainly containing ethylene terephthalate units and optionally containing other ester units has been used from the viewpoint of processability, corrosion resistance, flavor retention, etc. (Patent Document) 1).

  In general, polyethylene terephthalate has crystallinity and a high melting point, and has excellent properties such as tensile strength and impact resistance, but has the disadvantage that the physical properties are drastically reduced under high temperature and humidity conditions. Corrosion resistance and dent resistance decrease even if the contents are satisfactory under normal conditions when subjected to harsh conditions, such as when the contents are low acidity such as coffee beverages and are applied to hot benders However, the oligomer component of the polyester is eluted and the content is turbid. In particular, high-temperature retort has been desired in recent years for rationalization and efficiency of retort sterilization. In retort at high temperature, the amount of low-molecular-weight components contained in the film has increased, and it is inherently less than aqueous solution. Extraction of components having extremely low solubility becomes remarkable. Even if the amount transferred to the contents is much less than the limit set by the Ministry of Health, Labor and Welfare Notification Regulations and the US FDA Regulation, if it is processed at high temperature or stored for a long time, the relatively high molecular weight components transferred into the contents are Agglomeration may increase particle size and cause turbidity, which is not psychologically preferable.

  In order to solve such problems, the present applicant has included ethylene terephthalate units such that the amount of terephthalic acid components per total basic carboxylic acid component is 5 to 99 mol% and ethylene naphthalate units. Can be formed by extrusion coating of a copolyester or blend polyester containing 1 to 95 mol% of naphthalene dicarboxylic acid component per total basic carboxylic acid component A laminated body has been proposed (Patent Document 2).

JP-A-7-108650 Japanese Patent Laid-Open No. 10-288910

  In the above-mentioned laminated body for cans, it was possible to suppress the migration of the low molecular weight component inevitably present in the polyester into the contents during high-temperature treatment and long-term storage, and to suppress the turbidity of the contents. However, the high temperature retort desired in recent years has not been sufficient to suppress the turbidity of the contents. Furthermore, in the case of a metal can formed by forming an annular curled portion with the open end curled outward after the upper portion of the seamless can is neck-in processed if necessary like a reseal can, the resin is scraped off at the end of the curled portion There was a problem such as, and something that can withstand severe processing was necessary. In addition, in such metal cans, weight reduction has been achieved by thinning the can body in order to reduce costs, and along with the thinning of the can body, the resin coated on the metal plate is more A high degree of workability is required, and a resin-coated metal plate that can withstand a high degree of processing is required.

Accordingly, the object of the present invention is to suppress the turbidity of the contents due to elution of low molecular weight components even when subjected to high temperature treatment or heat warming, etc. It is also possible to provide a resin-coated metal plate that is capable of continuous can-making.
Another object of the present invention is to provide a metal can, in particular a reseal can, which can be continuously produced without turbidity of contents due to elution of low molecular weight components even when subjected to heat treatment such as high temperature treatment or hot warmer. That is.

According to the present invention, at least the upper layer and the resin-coated metal plate polyester resin coating layer of unoriented Ru formed, which are formed of two layers, the lower layer to the metal plate surface, so that the polyester resin coating layer is can inner side The upper polyester resin coating layer is made of a polyester resin containing a naphthalenedicarboxylic acid component in an amount of 0 to 15 mol%, and the lower polyester resin layer is made of a naphthalenedicarboxylic acid component 8 to Ri consists 25 mole% of the amount in and polyester resin containing more than the content of naphthalene dicarboxylic acid component of the polyester resin forming the upper layer, the seamless can top is mouth and neck with resealing engagement portion, The open end of the mouth-and-neck portion is wound outward to form an annular curl portion. Cans are provided.

According to the reseal can of the present invention,
1. The intrinsic viscosity [η] of the polyester resin forming the upper polyester resin layer and the lower polyester resin layer is 0.6 or more,
2. The thickness ratio of the upper polyester resin layer and the lower polyester resin layer is 1:20 to 20: 1;
3. The lower polyester resin layer contains a silica lubricant in an amount of 0.05 to 3% by weight with an average particle size in the range of 0.1 to 5.0 μm;
Is preferred.

  In the resin-coated metal plate of the present invention, the resin coating formed on the surface of the metal plate includes an upper layer made of a polyester resin containing a naphthalene dicarboxylic acid component in an amount of 0 to 15 mol%, and the polyester resin layer is naphthalene dicarboxylic acid High-temperature treatment such as retort sterilization by forming the lower layer of the polyester resin containing the component in an amount of 8 to 25 mol% and more than the content of the naphthalenedicarboxylic acid component of the polyester resin forming the upper layer Even when it is attached to a hot-warmer or hot bender, etc., the low molecular weight components are not eluted and the turbidity of the contents is effectively prevented.

In addition, the upper layer and the lower layer are made of polyester resins having different properties, so that they are excellent in workability, work adhesion, impact resistance (dent resistance), etc., and even when subjected to advanced processing, there are film defects. Without the occurrence, the above-described reseal can having the curled portion at the front end of the mouth-and-neck portion can be continuously manufactured with high productivity.
Furthermore, it is possible to obtain an effect that the product is not colored even when it is filled with an easily colored content.

  In the resin-coated metal plate of the present invention, a substantially unoriented polyester resin coating layer composed of at least two layers of an upper layer and a lower layer is formed on the surface of the metal plate, and the upper polyester resin coating layer contains 0 to 15 moles of a naphthalenedicarboxylic acid component. %, Especially 3 to 15 mol% of ethylene terephthalate-based polyester resin, the lower polyester resin layer forms naphthalenedicarboxylic acid component in an amount of 8 to 25 mol%, especially 10 to 20 mol% and forms the upper layer It is an important feature that the two-layer resin coating is substantially unoriented, and is composed of an ethylene terephthalate-based polyester resin containing more than the content of the naphthalenedicarboxylic acid component of the polyester resin.

In the present invention, when the naphthalenedicarboxylic acid component is an essential component as a dicarboxylic acid component of the polyester resin used for resin coating of the resin-coated metal plate, it is subjected to high-temperature wet heat conditions such as retort sterilization. In addition, the elution of low molecular weight components can be suppressed, and the occurrence of turbidity of the contents and the deterioration of workability and dent resistance can be prevented.
At this time, it is particularly important that the amount of naphthalenedicarboxylic acid contained is in the above range, and thereby, in addition to the above-described effects, it is possible to sufficiently develop characteristics such as processability and color resistance that can withstand severe processing. It becomes possible.

This is also clear from the results of Examples described later. When there are more upper layers than the said range, it becomes difficult to obtain the corrosion resistance and coloring resistance of the resin-coated metal plate secured by the upper layers (Comparative Example 4). Further, when the lower layer naphthalene dicarboxylic acid component is less than the above range, the above-described effect obtained by the naphthalene dicarboxylic acid component cannot be sufficiently obtained (Comparative Example 1), whereas when the amount is larger than the above range. Becomes inferior in corrosion resistance (Comparative Example 2).
Even when the amount of naphthalenedicarboxylic acid in the upper layer and the lower layer is within the above range, when the content of the upper layer is larger than the content of the lower layer (Comparative Example 5), the content of the lower layer is larger. It is clear that the coloration resistance and the fusion resistance are inferior to the case (Example 3).

  Furthermore, since the polyester resin coating of the resin-coated metal plate of the present invention is substantially unoriented, the elongation at break is large, and film breakage occurs even when subjected to severe processing such as drawing, stretching processing, ironing processing, etc. And excellent workability. On the other hand, the unoriented film has a defect that the barrier property is inferior to that of the stretched film, but in the present invention, it is almost the same as the stretched film by having a two-layer constitution of polyester resin having different naphthalenedicarboxylic acid content. Similar barrier properties can be imparted and excellent corrosion resistance can be obtained.

(Resin coated metal plate)
[Polyester resin]
As long as the polyester resin used for the resin-coated metal plate of the present invention contains naphthalenedicarboxylic acid in the above-mentioned range, a conventionally known one can be used, and it may be a copolyester or a blend. It may be. Moreover, the polyester resin which comprises an upper layer and a lower layer can also use the combination of the polyester resin of arbitrary compositions.

In the polyester used in the present invention, the naphthalene dicarboxylic acid is preferably composed of naphthalene-2,6-dicarboxylic acid, but may contain a small amount of other naphthalene dicarboxylic acid as long as the essence of the present invention is not impaired. Good.
A polyester derived from an acid component mainly composed of a combination of terephthalic acid and naphthalene-2,6-dicarboxylic acid and an alcohol component mainly composed of ethylene glycol is preferable. It is preferable that terephthalic acid accounts for 50 mol% or more of the acid component.

Acid components other than terephthalic acid include isophthalic acid, P-β-oxyethoxybenzoic acid, diphenoxyethane-4,4′-dicarboxylic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, adipic acid, sebacic acid , Dimer acid, trimellitic acid, pyromellitic acid and the like.
The acid component other than terephthalic acid and naphthalenedicarboxylic acid is allowed to be contained in an amount of 30 mol% or less based on the acid component.

As alcohol components other than ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexane dimethanol, ethylene oxide adduct of bisphenol A, Examples include glycol components such as trimethylolpropane and pentaerythritol.
As the diol component of the polyester, those mainly composed of ethylene glycol are preferable. It is preferable from the viewpoint of molecular orientation, barrier properties against corrosive components and aroma components that 95 mol% or more, particularly 98 mol% or more of the diol component is composed of ethylene glycol.

The polyester should have a molecular weight in the film forming range, and the intrinsic viscosity [η] measured using a phenol / tetrachloroethane mixed solvent as a solvent is 0.6 or more, particularly in the range of 0.65 to 1.2. It may be in terms of barrier properties against corrosive components and mechanical properties.
In addition, any polyester resin in the upper layer and the lower layer may contain a known film compounding agent, for example, an antiblocking agent such as amorphous silica, a pigment such as titanium dioxide, various antistatic agents, a lubricant, and the like according to a known formulation. Can be blended.
In the present invention, it is particularly preferable to add a silica-based lubricant having an average particle size in the range of 0.1 to 5.0 μm to the lower layer. Thereby, the multilayer film can be effectively prevented from blocking when the multilayer film is previously prepared and wound. The silica lubricant is desirably blended in an amount of 0.05 to 3% by weight based on the lower layer resin.

Furthermore, as the polyester resin used in the present invention, a blended olefin polymer having rubber-like elasticity can be used to improve impact resistance. Examples of the olefin polymer used in the present invention include low-, medium-, and high-density polyethylene, linear low density polyethylene (LLDPE), ethylene-butene-1 copolymer, ethylene-1-octene copolymer, Besides olefin homopolymer or copolymer such as ethylene-hexene copolymer, isotactic polypropylene, ethylene-propylene copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, etc. And olefin polymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ion-crosslinked olefin copolymer (ionomer), and blends thereof.
In the present invention, among these olefin polymers, those containing a resin having a polar unit are preferred, and examples thereof include ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, among which ion-crosslinked olefins. A copolymer (ionomer) can be most preferably used.

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 lower 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. Particularly, it is desirable that the temperature is in the range of 97 ° C to 80 ° C.

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.
Moreover, as a metal ion which neutralizes the carboxyl group in such a copolymer of ethylene and an α, β-unsaturated carboxylic acid, Na ⁺ , K ⁺ , Li ⁺ , Zn ⁺ , Z ²⁺ , Mg ²⁺ , Ca ²⁺ , Co ²⁺ , Ni ²⁺ , Mn ²⁺ , Pb ²⁺ , Cu ^2+, etc. In the present invention, those that are neutralized by zinc in particular have a high degree of crosslinking and are sensitive to humidity. Since there is little property, it can use suitably. 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.
The olefin polymer (B) is a thermoplastic polyester (A),
A: B = 95: 5 to 50:50
In particular, 90:10 to 70:30
It is preferable that it is blended by weight ratio. If the olefinic polymer is less than the above range, impact resistance (dent resistance), corrosion resistance, adhesion cannot be sufficiently improved, and more olefinic polymer than the above range, When the coating layer is formed, holes are opened in the film, resulting in poor film forming properties. Further, excellent properties such as workability and corrosion resistance of the polyester resin are inferior to those in the above range.

[Metal plate]
As the metal plate used in the present invention, various surface-treated steel plates and light metal plates such as aluminum are used. As the surface-treated steel sheet, a cold-rolled steel sheet is annealed and then secondary cold-rolled and subjected to one or more surface treatments such as galvanizing, tin-plating, nickel-plating, electrolytic chromic acid treatment, and chromic acid treatment. Can be used. Further, an aluminum-coated steel sheet subjected to aluminum plating, aluminum rolling, or the like is used. In addition to the so-called pure aluminum plate, an aluminum alloy plate is used as the light metal plate. The original thickness of the metal plate varies depending on the type of metal and the use or size of the container, but generally it should have a thickness of 0.10 to 0.50 mm. The thickness is preferably 10 to 0.30 mm, and in the case of a light metal plate, the thickness is preferably 0.15 to 0.40 mm.

[Layer structure]
FIG. 1 is a diagram showing a cross-sectional structure of an example of the resin-coated metal plate of the present invention. The resin-coated metal plate of the present invention, indicated as a whole by 1, is a metal plate 2, a lower layer 3 made of an ethylene terephthalate-based polyester resin having a naphthalenedicarboxylic acid content of 8 to 25 mol% formed on the surface of the metal plate 2, a lower layer 3 comprises an upper layer 4 made of an ethylene terephthalate polyester resin having a naphthalenedicarboxylic acid content of 0 to 15 mol%.
In the resin-coated metal plate shown in FIG. 1, when formed into a metal can, the polyester resin coating composed of the lower layer 3 and the upper layer 4 is formed only on the inner surface, but of course the same is applied to the outer surface. The polyester resin coating may be formed, or a single layer resin coating may be formed.

  Further, in the present invention, various configurations other than the above-described layer configuration can be adopted, and a conventionally known adhesion primer can be provided between the metal plate and the lower layer on the inner surface side or the lower layer on the outer surface side. . This adhesion primer exhibits excellent adhesion to both the metal material and the film. As a primer paint excellent in adhesion and corrosion resistance, it is a phenol epoxy paint composed of a resol type phenol aldehyde resin derived from various phenols and formaldehyde and a bisphenol type epoxy resin. It is a paint containing a resin in a weight ratio of 50:50 to 1:99, in particular 40:60 to 5:95. The adhesive primer layer is generally preferably provided with a thickness of 0.01 to 10 μm. The adhesive primer layer may be provided on a metal material in advance, or may be provided on a polyester film.

In the present invention, the thickness of the above-mentioned upper layer is preferably in the range of 1 to 24 μm, particularly 2 to 12 μm, while the thickness of the lower layer is preferably in the range of 4 to 36 μm, particularly 8 to 32 μm.
Moreover, it is preferable from points, such as workability and corrosion resistance, that the thickness ratio of an upper layer and a lower layer exists in the range of 1: 20-20: 1, especially 2: 18-18: 2.

[Lamination method]
The resin-coated metal plate of the present invention is formed by previously forming a multilayer film composed of the above-described upper layer and lower layer by a known lamination method, preferably by lamination of a multilayer cast film or coextrusion coating, and then laminating the metal film. A resin-coated metal plate may be used, or a resin-coated metal plate may be formed by extrusion lamination in which the resin plate is directly melt-extruded onto the metal plate.
Lamination of the multilayer cast film is formed by putting the upper and lower polyester resin chips in separate extruders, heating and melting them, extruding them into a sheet form from a die, and cooling and solidifying them on a casting drum. On the other hand, the coextrusion coat is formed by using two extruders and supplying the upper and lower polyester resins to a die and extruding them.
In the present invention, by using a multilayer cast film lamination or coextrusion coating to form a laminated film, it is possible to strongly bond the interlayer without using an adhesive between the films, thereby improving workability. it can.

  Also, in the extrusion laminating method in which polyester resin is melt-extruded directly on a metal plate, at least an extruder for the upper layer resin and an extruder for the lower layer resin are used, and the resin flow from each extruder is merged in a multi-layer die. The molten resin film extruded from the T-die is passed through a pair of laminate rolls together with a metal plate, and pressed and integrated 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.

(Metal can)
The metal can of the present invention is a drawing / redrawing process and a bending / stretching process (stretch process) by drawing / redrawing so that the multilayer film coating surface composed of the upper layer and the lower layer of the resin-coated metal plate is the inner surface side of the can. It can be produced by subjecting it to a conventionally known means such as bending / stretching / ironing by drawing / redrawing or drawing / ironing.
The metal can of the present invention is manufactured by the above-mentioned means, but preferably the side wall portion is thinned by performing bending and stretching by redrawing and / or ironing. As for the thinning, the side wall portion is thinned so as to have a thickness of 20 to 95%, particularly 30 to 85% of the base thickness of the resin-coated metal plate, by bending and / or ironing the side wall portion compared to the bottom portion. It becomes.

Since the resin-coated metal plate of the present invention is particularly excellent in workability, it can be effectively applied to a reseal can that is subjected to a high degree of processing.
The re-seal can, roughly speaking, forms the mouth and neck by necking in the upper part of the seamless can as required, and the re-sealing engagement part (for example, screw part) and the open end of the mouth and neck part. Is formed by forming an annular curl portion that is wound outward. At this time, in the conventional resin-coated metal plate, the resin coating was scraped or cracked at the tip of the curled part of the neck and neck, but the reseal can made of the resin-coated metal plate of the present invention has such disadvantages. In addition, turbidity due to the elution of low molecular weight components is effectively prevented even when subjected to heat retention by a high temperature retort treatment or hot warmer.

(Metal can lid)
The lid of the present invention can take a conventionally known shape except that the surface on which the polyester lower layer and upper layer of the resin-coated metal plate are formed is the inner surface side of the lid. In addition to the easy open lid of the system or the steion tab system, a screw cap used for a reseal can etc. may be used.

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. In the rivet forming process, a rivet that protrudes to the outer surface is formed on the opening section defined by the score using a rivet forming die, and in the tab mounting process, the opening tab is fitted to the rivet and the protruding part of the rivet is fed out. By fixing the tab, an easy open lid is formed. In the case of an adhesive tab instead of the rivet forming process, an adhesive such as a nylon adhesive tape is applied to the opening part or tab, and the tab and the opening part are thermally bonded in the tab attaching process. The
The screw cap used for the reseal can is formed by drawing a resin-coated metal plate and then performing screw processing, liner processing, or the like.

The invention is illustrated in the following examples.
Using the resin shown in Table 1, the resin-coated metal plate shown in (1) was prepared. At this time, the resin characteristic values shown in (2) and (3) were measured and shown together in Table 1. Subsequently, this resin-coated metal plate was formed into a can by the following forming method, and the following characteristic values (4) to (6) of the inner surface resin layer of the can were obtained. Further, this can was subjected to the following evaluation (7). These characteristic values and can evaluation results are summarized in Table 2.
As can be seen from Table 2, the examples based on the present invention had good moldability, corrosion resistance, and turbidity based on retort elution, and were optimal as cans for storing beverages.

(1) Preparation of resin-coated metal plate A resin-coated metal plate was prepared by the method shown in Table 2 using the resin shown in Table 1. In the film laminating method, a resin obtained by feeding a resin to an extruder, and extruding it through a two-layer T die so as to have a thickness ratio of 1: 4 and a total thickness of 20 μm is cooled by a cooling roll. Was rolled up into a cast film. At this time, the optimum temperature condition suitable for each resin was selected as the temperature condition.
In addition, for those using a biaxially stretched film, naphthalene dicarboxylic acid 10 mol% copolymerized PET resin was extruded in the same manner as described above, then biaxially stretched 3.0 times in length and 3.0 times in width, and heated at 180 ° C. Set to create a stretched film.
These produced films were made of TFS steel plate (plate thickness 0.24 mm, metal chromium content 120 mg / m ² , chromium hydrated oxide content 15 mg / m ² ) or aluminum alloy plate (A3004H39 material) with a plate thickness 0.24 mm. A laminate was obtained by heat laminating on both sides and immediately water cooling. At this time, the temperature of the metal plate before lamination was set 15 ° C. higher than the melting point of the polyester resin.
Further, lamination was performed at a laminating roll temperature of 150 ° C. and a sheet passing speed of 40 m / min to obtain a resin-coated metal plate.
In the method by extrusion lamination, a resin having the composition shown in Table 1 on a TFS steel plate heated to 250 ° C. (plate thickness 0.24 mm, metal chromium content 120 mg / m ² , chromium hydrated oxide content 15 mg / m ² ). Was supplied to a φ65 mm extruder equipped with extrusion laminating equipment, and melt extrusion was performed so that the outer surface side had a thickness of 20 μm, which was laminated on one side of TFS. Next, as the inner surface side, the same resin component was extruded and supplied to a φ65 mm extruder equipped with laminating equipment, and then the plate temperature was heated to a temperature 30 ° C. lower than the melting point of the resin, and melt extrusion was performed to a thickness of 30 μm. The other surface was laminated to obtain a resin-coated metal plate.

(2) Resin intrinsic viscosity 200 mg of the resin shown in Table 1 was dissolved in a phenol / 1,1,2,2-tetrachloroethane mixed solution (weight ratio 1: 1) at 110 ° C., and using an Ubbelohde viscometer. The specific viscosity was measured at 30 ° C.
The intrinsic viscosity was determined by the following formula.
[Η] = [(− 1+ (1 + 4K′η _sp ) ^1/2 ) / 2K′C ”(dl / g)
K ′: constant of Haggins (= 0.33)
C: Concentration (g / 100ml)
η _sp : specific viscosity [= (solution dropping time−solvent dropping time) / solvent dropping time]

(3) Retort treatment test For the reseal can, the cap shown below was used. For the 350 ml can, a positive pressure steion tub lid (SOT) covered with epoxy acrylic paint was used, and distilled water was used at 95 ° C. After filling, a retort treatment at 135 ° C. for 30 minutes was performed, the temperature was returned to room temperature, distilled water was taken out and subjected to turbidity measurement. Moreover, the state of the inner surface of the can was observed.
For turbidity measurement, a simple high-sensitivity turbidity / colorimeter manufactured by Yasui Instruments Co., Ltd. is used, 100 ml of sample is taken in a turbidity colorimetric tube, placed in a sample cell, and diluted turbidity standard solution as a standard for comparison. A turbidity colorimetric tube with 100 ml taken was placed in a control cell, the bottom was seen through from the top, and the brightness of both bottoms were compared to measure turbidity. The lid of Example 5 was measured together with the can body of Example 4.
The cap used was 20.8 mm in height using aluminum (JIS5151 / H39) with a plate thickness of 0.25 mm, 38.4 mm in outer shape, and using a styrene liner.

(4) Preparation of molded reseal can A wax-based lubricant was applied to the polyester resin-coated metal plate shown in Table 1, and a disk having a diameter of 158 mm was punched out to obtain a shallow drawn cup. Subsequently, this shallow drawn cup was redrawn and ironed, and bottom molding was performed by a conventional method to obtain a deep drawn-ironed cup.
The characteristics of this deep drawn cup were as follows.
Cup diameter: 52mm
Cup height: 141.5mm
37% of can wall thickness relative to base plate thickness
Flange thickness 69% of base plate thickness
This deep-drawn ironing cup is molded into a bottom according to a conventional method, and after heat-treating the polyester resin at Tm-10 ° C. for 3 minutes, the cup is allowed to cool, and then the opening edge is trimmed, curved surface printed and printed. Yopi-baked and dried. This cup was further subjected to neck processing, bead processing, screw processing, and curling processing to produce a reseal can with a diameter of 30 mm shown in FIG.

Preparation of 350 ml can A wax-based lubricant was applied to the polyester resin-coated metal plate shown in Table 1, and a disk having a diameter of 152 mm was punched out to obtain a shallow drawn cup. Next, the shallow drawn cup was ironed to obtain a seamless cup. Various characteristics of this seamless cup were as follows.
Cup diameter: 66mm
Cup height: 127mm
The thickness of the can wall relative to the base plate: 45%
This seamless cup is domed in accordance with a conventional method, and after a heat treatment of Tm-10 ° C. for 3 minutes for the polyester resin, the cup is allowed to cool, then trimming of the edge of the opening, curved surface printing and baking drying, Post-processing such as neck-in processing and flange processing was performed to obtain a 350 cc seamless can.

Preparation of DR can Apply a wax-based lubricant to a polyester resin-coated metal plate using a 0.22 mm thick aluminum alloy (JISA3004P) shown in Table 1, punch out a 154 mm diameter circular blank, and then squeeze twice Processing was performed to produce a can with a flanged inner diameter of 79.5 mm, a height of 46 mm, and an internal volume of 200 ml.

Creation of a lid Apply a wax-based lubricant to the polyester resin-coated aluminum alloy (A5182, plate thickness 0.235 mm) shown in Table 1, punch out a lid with a diameter of 68.7 mm, and then open a partially open type on the outer surface side of the lid. Score processing (width 22 mm, score remaining thickness 110 μm, score width 20 μm), rivet processing and attachment of a tab for opening were performed to create an SOT lid.

It is a figure which shows an example of the cross-section of the resin coating metal plate of this invention. It is a figure which shows the reseal can which used the resin coating metal plate of this invention.

Claims (4)

At least upper and lower two layers formed Ru unoriented resin-coated metal plate polyester resin coating layer is formed from a metal plate surface, the polyester resin coating layer is formed by molding such that the can inner side In the seamless can , the upper polyester resin coating layer comprises a polyester resin containing a naphthalenedicarboxylic acid component in an amount of 0 to 15 mol%, and the lower polyester resin layer comprises an naphthalenedicarboxylic acid component in an amount of 8 to 25 mol%. and Ri many content to a polyester resin than the content of naphthalene dicarboxylic acid component of the polyester resin forming the upper layer formed, the seamless can top is mouth and neck with resealing engagement portion, the open end of the mouth neck Is a re-sealed can characterized in that an annular curled portion is formed . The resealable can according to claim 1, wherein the intrinsic viscosity [η] of the polyester resin forming the upper polyester resin layer and the lower polyester resin layer is 0.6 or more. The reseal can according to claim 1 or 2, wherein a thickness ratio of the upper polyester resin layer and the lower polyester resin layer is 1:20 to 20: 1. The resealable can according to any one of claims 1 to 3, wherein the lower polyester resin layer contains a silica lubricant in an amount of 0.05 to 3% by weight having an average particle size in the range of 0.1 to 5.0 µm. .

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