JPH08119285A - Thinned seamless can - Google Patents

Abstract

PURPOSE: To increase the anticorrosition property and external appearance, by providing an ultraviolet ray setting coating layer mixed with titanium oxide with a specified thickness on the external face film layer at the side wall of a metallic material and setting the total amount of titanium oxide per unit area of the side wall of external face at least in a specified value. CONSTITUTION: In a thinned seamless can 1, the metallic base material 11 is coated with a thermoplastic film at both inside and outside and an ultraviolet ray setting coating layer 16 mixed with titanium oxide having 3-20 micron millimeter in thickness is applied on the external face side film layer of the side wall 3. And the total amount of titanium oxide per unit area of the external face side wall is at least 0.5mg/cm<2> . When the thickness of ultraviolet ray setting coating layer 16 mixed with titanium oxide is finer than 3μm, a sufficient whiteness degree cant not be obtained and also the hiding power is not enough. On the other hand, when the thickness is larger than 20μm, the coating layer can not follow at the neck-in process and hence, the coating layer is broken. Since the coating layer has been hardened by ultraviolet ray, it is lustrous and excellent in score-resistance and hence, the external appearance characteristics are increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin seamless can having improved corrosion resistance, impact resistance and appearance characteristics.
More specifically, the present invention relates to a thinned seamless can whose inner and outer surfaces are covered with a resin film and whose outer surface is provided with a white coating.

[0002]

2. Description of the Related Art Conventionally, so-called seamless cans having no side surface are made by drawing metal material such as aluminum plate, tin plate or tin-free steel plate in at least one stage between a drawing die and a punch. To form a cup consisting of a side-seamless body and a bottom integrally connected to the body seamlessly, and then, if desired, ironing between the ironing punch and the ironing die on the body A method of manufacturing a can is known in which a container body is thinned by processing.

Also, instead of ironing, there is already known a manufacturing method in which the side wall portion is bent and extended at the curvature corner portion of the redrawing die to thin the side wall portion (Japanese Patent Publication No. 56-501).
No. 442).

For the purpose of saving the container material and manufacturing a can having a large can height (height) from a certain amount of metal material, it is preferable to thin the container body by ironing or bending and stretching. That is.

Further, as an organic coating method for a side seamless can, in addition to a generally widely used method of applying an organic paint to a can after molding, a method of previously laminating a resin film on a metal material before molding, etc. As an example of the latter, Japanese Patent Publication No. 59-34580 describes that a metal material laminated with a polyester film derived from terephthalic acid and tetramethylene glycol is used. . It is also known to use a coated metal plate of vinyl organosol, epoxy, phenolics, polyester, acrylic or the like in the production of a redrawn can by bending and stretching.

It is also known to provide a white coating on the outer surface of a seamless can, and a printing ink layer and a finishing varnish layer on it. For example, Japanese Utility Model Publication No. 6-16739 discloses TFS (electrolytic chromic acid). Deep squeezing a clear polyester film laminated on the inner surface of the treated steel plate and a polyester film containing titanium dioxide on the outer surface, apply a printing ink layer and a finishing varnish layer on the outer surface of this cup, and bake it, then neck It is described that a can is obtained by performing in-processing and flange processing.

[0007]

[Problems to be Solved by the Invention]
The method of preliminarily laminating a titanium oxide-containing film on the outer surface of a seamless can as disclosed in Japanese Patent No. 39 discloses a method of concealing a metal substrate to give an excellent appearance and utilizing the anticorrosive effect of titanium oxide itself to form a film at the time of drawing. Although it has excellent effects such as better transmission of wrinkle holding force to the container, the side wall of the container is ironed in order to manufacture a can with a large can height (height) from a certain amount of metal material. Alternatively, when the film is thinned by bending and stretching, the titanium oxide-containing film also becomes thin, a satisfactory hiding effect cannot be obtained, and the commercial value of the can decreases. Of course, if a titanium oxide-containing film having a large thickness is used in consideration of the degree of thinning in advance, satisfactory results can be obtained in the hiding property. However, in this case, there is a problem that the white distribution in the can height direction becomes uneven due to the influence of the thickness distribution in the can height direction due to the molding of the can.

In the field of can manufacturing, a coating called a white coat is generally provided in order to conceal a metal substrate, but when this means is applied to a resin film-coated seamless can, a white coating is applied. The baking of the coat increases the degree of crystallinity of the resin film, which causes a problem that the workability of the film is lowered or the impact resistance is lowered.

That is, in the production of seamless cans, a cup that has been coated or printed is subjected to neck-in processing or flange processing to obtain a final seamless can. At the time of this neck-in processing or flanging, the resin coating on the inner surface of the processed portion is performed. Is apt to be exposed or has potential damage, and point corrosion or under-film corrosion (UFC) on the inner surface of the neck portion may proceed immediately or with time, or the flavor retention of the content may deteriorate.

Another property of concern in seamless cans is impact resistance. That is, the seamless can does not have a reinforcing structure such as a double winding part at the bottom like a side seam can,
Moreover, since the side wall is generally thin, if the impact is applied to the bottom such as a drop impact, if the coating is highly crystallized and becomes brittle, peeling off the coating on the impacted part,
Coating defects such as pinholes and cracks are likely to occur.

Therefore, an object of the present invention is to provide a thin-walled seamless can which has improved corrosion resistance, impact resistance and appearance characteristics and whose inner and outer surfaces are covered with a resin film and whose outer surface is provided with a white coating. .

[0012]

According to the present invention, in a thin seamless can of a resin-coated metal material, the inner surface and the outer surface of the metal material are made of a thermoplastic film and at least the outer surface film of the side wall portion is formed. A UV-curable coating layer containing titanium oxide is provided on the layer with a thickness of 3 to 20 μm, whereby the total amount of titanium oxide per unit area of the outer side wall is 0.5 mg / cm ² or more. Seamless cans are provided.

In the present invention, the titanium oxide in the UV-curable coating layer is preferably rutile-type titanium dioxide from the viewpoint of hiding power, and the UV ray used for curing the coating layer is near-ultraviolet light or near-ultraviolet light. Preferably there is.

In the thinned seamless can of the present invention,
The outer surface-coated thermoplastic film may be a titanium oxide-containing polyester film.

The effect of the present invention is great when the thickness of the side wall portion is reduced to 80% or less of the thickness of the bottom wall portion.

[0016]

In the seamless can of the present invention, the side wall of the can is thinned, and the titanium oxide-containing UV-curable coating layer is provided on the outer thermoplastic film of the thinned side wall. Is.

This coating layer contains titanium oxide and has a high whiteness and an excellent hiding effect, and since it is UV-cured in the form of a coating, it is rich in gloss and is tough and scratch resistant. Since it is also excellent, the appearance characteristics and commercial value of the seamless can can be enhanced.

It is particularly important to UV cure the titanium oxide loaded coating layer. Since it is difficult to print or coat the can body after the final processing due to the presence of the neck portion and the flange, it is absolutely necessary to coat the can body before these processing.
In this case, when the coating layer is baked by heating,
The resin coating on the inner surface of the part where neck-in processing or flange processing should be subjected to heat history, and the resin coating on the inner surface becomes brittle as it crystallizes or progresses due to this heat. And the impact resistance of the entire inner surface coating is also reduced, which causes corrosion resistance and flavor retention. On the other hand, in the present invention, since an ultraviolet curable coating is used and is cured by ultraviolet light, no extra heat history is given, and corrosion resistance, impact resistance and flavor retention are remarkably improved. is there.

In the present invention, it is also important to provide the titanium oxide-containing UV-curable coating layer with a limited thickness, that is, a thickness of 3 to 20 μm. Thickness is 3μ
When it is smaller than m, sufficient whiteness cannot be obtained and the hiding effect on the metal substrate is not sufficient, while 20 μm.
If it is thicker than the above, the coating layer cannot follow the processing during neck-in processing and flange processing,
The coating layer will be destroyed, and it is not economically preferable.

When a titanium oxide-containing UV-curable coating is UV-cured, the UV-curing efficiency tends to be low. FIG. 1 shows the reflectance of various titanium oxides at each wavelength. Referring to FIG. 1, titanium oxide has a large tendency to absorb ultraviolet rays, and as a result that titanium oxide absorbs the ultraviolet rays with which the coating layer is irradiated, it cannot be effectively used for polymerization and curing of the resin component of the coating layer. Cause a situation.

In order to prevent this, it is effective to use a near-ultraviolet ray for the ultraviolet curing of the coating layer and to use an ultraviolet curable resin having a high sensitivity in the near-ultraviolet range.

In the thinned seamless can of the present invention,
The outer surface-coated thermoplastic film may be a titanium oxide-containing polyester film. This is because the titanium oxide compounded in the film is somewhat useful for improving the whiteness and not only can reduce the thickness of the coating layer, but the titanium oxide itself has an excellent anticorrosion effect and at the time of squeezing the film. This is because it has the effect of improving the transmission of the wrinkle pressing force to the. The polyester film is also excellent in mechanical properties, processability, barrier properties against corrosive components, and the like.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 2 showing an example of the thinned seamless can of the present invention, the thinned seamless can 1 is formed by deep drawing (drawing-redrawing) or drawing-ironing of the resin-coated metal material described above. It is composed of a bottom portion 2 and a side wall portion 3. A flange portion 5 is formed on the upper end of the side wall portion 3 via a neck portion 4. In this can 1, the side wall portion 3 is thinner than the bottom portion 2 by bending and stretching and ironing.

In FIG. 3 showing an example of the cross-sectional structure of the side wall portion of the thinned seamless can, the side wall portion 10 is formed on the metal substrate 11, the inner thermoplastic film 12 provided on the inner surface of the metal substrate 11, and the outer surface of the substrate. It comprises an outer thermoplastic film 14 provided, a titanium oxide-comprising UV-curable coating layer 16 on the outer film, a printing ink layer 17 on the coating layer and a finishing varnish layer 18 on the printing ink layer.

In FIG. 4 showing another example of the cross-sectional structure, the cross-sectional structure is the same as that of FIG. 3, but between the metal surface and the inner surface organic coating 12 and between the metal surface and the outer surface organic coating 14.
And the adhesive layers 15a and 15b are respectively interposed between and.

The thin-walled seamless can molded body (cup) used in the present invention may be any one as long as it has a thermoplastic film on the inner surface and the outer surface of the metal plate, and the organic coated metal plate is molded into the cup. .

This cup is obtained by subjecting the coated metal plate to redrawing and ironing, drawing and bending and redrawing, drawing and bending and redrawing and ironing.

In the present invention, various surface-treated steel plates and light metal plates such as aluminum are used as the metal plate.

As the surface-treated steel sheet, a cold-rolled steel sheet is annealed and then secondary cold-rolled, and one or more surface treatments such as zinc plating, tin plating, nickel plating, electrolytic chromic acid treatment and chromic acid treatment are performed. It can be used.
An example of a suitable surface-treated steel sheet is an electrolytic chromic acid-treated steel sheet, which is particularly provided with a metal chromium layer of 10 to 200 mg / m ² and a chromium oxide layer of 1 to 50 mg / m ² (metal chromium conversion). This is an excellent combination of coating film adhesion and corrosion resistance. Another example of a surface-treated steel plate is a hard tin plate having a tin plating amount of 0.5 to 11.2 g / m ² . This tin plate is preferably subjected to chromic acid treatment or chromic acid / phosphoric acid treatment so that the amount of chromium becomes 1 to 30 mg / m ^{2 in} terms of metal chromium. As still another example, an aluminum-coated steel plate that has been subjected to aluminum plating, aluminum pressure welding, or the like is used. Among these, the effect is particularly large when applied to the electrolytic chromic acid-treated steel sheet.

The light metal plate is a so-called pure aluminum plate.
Besides, an aluminum alloy plate is used. Corrosion resistance and
Aluminum alloy plate, which has excellent workability, has Mn: 0.2
To 1.5% by weight, Mg: 0.8 to 5% by weight, Zn:
0.25 to 0.3% by weight, and Cu: 0.15 to
0.25% by weight with the balance being Al
You. These light metal plates also have a chromium content in terms of metal chromium.
20 to 300 mg / m ²Chromic acid treatment
Or chromic acid / phosphoric acid treatment is desired
New

The thickness of the metal plate, that is, the thickness of the bottom of the can (tB)
Although it depends on the type of metal, the use or size of the container, it is generally preferable that it has a thickness of 0.10 to 0.50 mm.
It is preferable to have a thickness of 0.10 to 0.30 mm, and in the case of a light metal plate, a thickness of 0.15 to 0.40 mm.

The thermoplastic resin coated on the metal plate is preferably a crystalline thermoplastic resin, and examples thereof include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene. -Acrylic ester copolymer, olefin resin film such as ionomer; polyethylene terephthalate,
Examples thereof include polyesters such as polybutylene terephthalate and ethylene terephthalate / isophthalate copolymers; polyamides such as nylon 6, nylon 6,6, nylon 11 and nylon 12; polyvinyl chloride; polyvinylidene chloride.

The thermoplastic resin coating layer contains an inorganic filler (pigment) for the purpose of concealing the metal plate and assisting the transmission of the wrinkle holding force to the metal plate during drawing-redrawing. You can In addition, a compounding agent known per se for the film, for example, an antiblocking agent such as amorphous silica, various antistatic agents, lubricants, antioxidants, ultraviolet absorbers and the like may be added to this film according to a known formulation. it can.

The inorganic fillers include inorganic white pigments such as rutile type or anatase type titanium dioxide, zinc white, and gloss white; barite, precipitated barium sulfate, calcium carbonate, gypsum, precipitated silica, aerosol, talc, calcined or Is a white extender pigment such as unsintered clay, barium carbonate, alumina white, synthetic or natural mica, synthetic calcium silicate, magnesium carbonate; black pigment such as carbon black and magnetite; red pigment such as red iron oxide; yellow pigment such as siena. And blue pigments such as ultramarine blue and cobalt blue. These inorganic fillers can be added in an amount of 10 to 500% by weight, particularly 10 to 300% by weight, based on the resin. It has already been pointed out that titanium dioxide has a particularly large hiding power, and it is preferable to fill the outer surface side resin layer with the material.

The coating of the coated thermoplastic resin on the metal plate is performed by a heat fusion method, dry lamination, an extrusion coating method or the like, and the adhesiveness (heat fusion property) between the coating resin and the metal sheet.
When the amount is low, for example, a urethane-based adhesive, an epoxy-based adhesive, an acid-modified olefin resin-based adhesive, a copolyamide-based adhesive, a copolyester-based adhesive or the like can be interposed.

The thickness of the thermoplastic resin is preferably in the range of generally 3 to 50 μm, particularly 5 to 40 μm. In the case of heat fusion using a film, it may be unstretched or stretched.

As a particularly suitable film, a polyester mainly comprising ethylene terephthalate units is formed into a film by a T-die method or an inflation film forming method, and this film is biaxially stretched successively or simultaneously at a stretching temperature and stretched. The film produced by heat-fixing the latter film can be mentioned.

As the raw material polyester, polyethylene terephthalate itself can be used under remarkably limited stretching, heat setting and laminating conditions, but it is necessary to reduce the maximum crystallinity that can be achieved by the film to reduce impact resistance and processability. It is desirable that the copolymer ester unit other than ethylene terephthalate is introduced into the polyester for this purpose. In the present invention, it is particularly preferable to use a biaxially stretched film of a copolymerized polyester mainly composed of ethylene terephthalate units and containing a small amount of other ester units and having a melting point of 210 to 252 ° C. The melting point of homopolyethylene terephthalate is generally 255 to 265 ° C.

Generally, 70 mol% or more, especially 75 mol% or more of the dibasic acid component in the copolyester is composed of a terephthalic acid component, and 70 mol% or more, especially 75 mol% or more of the diol component is composed of ethylene glycol, It is preferable that 1 to 30 mol%, particularly 5 to 25% of the dibasic acid component and / or diol component is composed of a dibasic acid component other than terephthalic acid and / or a diol component other than ethylene glycol.

Dibasic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid: alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid: succinic acid, adipic acid, sebacic acid, dodecane Aliphatic dicarboxylic acids such as dionic acid: One or a combination of two or more thereof may be mentioned. As the diol component other than ethylene glycol, propylene glycol,
1,4-butanediol, diethylene glycol, 1,
One or more of 6-hexylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A and the like can be mentioned. Of course, the combination of these comonomers must have the melting point of the copolyester within the above range.

The copolyester used should have a molecular weight sufficient to form a film, for which an intrinsic viscosity (IV) of 0.55 to 1.9 dl / g, in particular 0.65 to 1.4 dl / g. Those in the range of g are desirable.

The film is generally stretched at 80 to 110 ° C.
It is preferable that the area stretching ratio is 2.5 to 16.0, especially 4.0 to 14.0, and the film is heat-set at 130 to 240 ° C., especially 150 to 2
It is preferable to carry out in the range of 30 ° C.

It is important that the copolyester film is biaxially stretched. The degree of biaxial orientation can also be confirmed by a polarized fluorescence method, a birefringence method, a density gradient tube method, or the like.

When laminating, the time for the film to be laminated to pass through the crystallization temperature range is shortened as much as possible in order to prevent excessive crystallization, and this temperature range is preferably within 10 seconds, particularly 5 seconds. Try to pass within. For this,
When laminating, only the metal material is heated, and the laminated body is forcibly cooled immediately after laminating the films. For cooling, direct contact with cold air or cold water or pressure contact of a cooling roller forcibly cooled is used. It should be understood that it is possible to relax the degree of crystal orientation by heating the film to a temperature near the melting point during the lamination and then performing rapid cooling after the lamination.

When an adhesive primer is used, it is generally desirable to subject the surface of the film to corona discharge treatment in order to enhance the adhesion to the film. The degree of corona discharge treatment is such that the wetting tension is 44
It is desirable that the dyne / cm is not less than that.

In addition, it is also possible to subject the film to plasma treatment, flame treatment, or other known adhesion-improving surface treatment, or urethane resin-based or modified polyester resin-based adhesion-improving coating treatment. .

The adhesive primer, which is optionally provided between the polyester film and the metal material, exhibits excellent adhesion to both the metal material and the film. A typical example of a primer coating having excellent adhesion and corrosion resistance is a phenol epoxy-based coating composed of a resol-type phenol aldehyde resin derived from various phenols and formaldehyde, and a bisphenol-type epoxy resin. Particularly, the phenol resin and the epoxy resin are 50: 5.
0 to 5:95 weight ratio, especially 40:60 to 10:90
It is a paint containing in a weight ratio of.

The adhesive primer layer is generally 0.3 to 5
It is preferable to provide it with a thickness of μm. The adhesive primer layer may be previously provided on the metal material or may be previously provided on the polyester film.

The metal cup-shaped container is molded by a means known per se so that the side wall portion is thinned, for example, drawing redrawing and ironing, drawing and bending and redrawing, drawing and bending and redrawing and ironing. Done in.

For example, according to deep drawing bending drawing (drawing-bending drawing redrawing), a front drawing cup formed from a coated metal plate is inserted into the cup-shaped holding member and below it. Hold with re-drawing dies located. The re-drawing punch is arranged coaxially with the holding member and the re-drawing die so as to be able to move in and out of the holding member.
The redraw punch and the redraw die are moved relative to each other so as to mesh with each other.

As a result, the side wall portion of the front draw cup is bent perpendicularly inward from the outer peripheral surface of the annular holding member through its curvature corner, and the annular bottom surface of the annular holding member and the upper surface of the redrawing die. It passes through the part specified by and and is bent almost perpendicular to the axial direction by the action corner of the redrawing die.
It can be molded into a deep drawing cup having a smaller diameter than the front drawing cup.

At this time, the radius of curvature (Rd) of the working corner portion of the redrawing die is set to be 1 to 2.9 times, particularly 1.5 to 2.9 times the metal plate thickness (tB). As a result, it is possible to effectively reduce the wall thickness by bending and pulling the side wall portion. Not only is the variation in thickness between the lower portion and the upper portion of the side wall portion eliminated, it is possible to reduce the thickness evenly throughout. Generally, the side wall of the can body has the following formula (1). In the formula, tB is the thickness of the blank, and tW is the thickness of the side wall. It is possible to reduce the thickness to 5 to 45%, particularly 5 to 40%.

In the case of a deep-drawn can, the following formula (2) In the formula, D is the diameter of the sheared laminate material, d is the punch diameter, and the reduction ratio RD defined is 1.
It is preferable that the range is 1 to 3.0, and the total range is 1.5 to 5.0.

Further, an ironing die is arranged behind the redrawing or bending / stretching redrawing, and the thinning rate including ironing is 5 to 70%, particularly 10 to 60% with respect to the side wall portion.
It can also be thinned by ironing so that it has the same thickness.

For drawing, etc., various lubricants such as liquid paraffin, synthetic paraffin, edible oil, hydrogenated edible oil, palm oil, various natural waxes, and polyethylene wax are applied to the coated metal plate or further cups for molding. Good to do. The amount of lubricant applied varies depending on the type, but is generally 0.1 to 10 mg / dm ² , and particularly 0.2.
It is preferably in the range of 5 to 5 mg / dm ² , and the lubricant is applied by spray-coating the lubricant in a molten state on the surface.

In order to improve the drawability of the cup,
Advantageously, the temperature of the resin-coated squeeze cup is preset to a temperature not lower than the glass transition point (Tg) of the coating resin, particularly not higher than the thermal crystallization temperature, and molding is performed in a state in which the plastic coating of the resin coating layer is facilitated Is.

The inner surface side organic coated metal cup after molding is
After the so-called trimming, in which the ear portion of the cup opening is cut, the printing process is performed. Prior to this trimming treatment, the cup after molding is covered with the glass transition point (T
The strain of the coating resin can be relaxed by heating to a temperature not lower than g) and lower than the melting point. This operation is particularly effective in the case of a thermoplastic resin in order to enhance the adhesion between the coating and the metal.

[Titanium oxide-containing UV-curable coating layer] In the present invention, a UV-curable coating layer containing titanium oxide is used. This coating layer contains an ultraviolet curable resin composition, and the ultraviolet curable resin composition is roughly classified into a cation curable type and a radical polymerization type.

As the ultraviolet cationic polymerization type resin composition, a combination of an ultraviolet curing type epoxy resin and a cationic photopolymerization catalyst is used.

The ultraviolet-curable epoxy resin contains an epoxy resin component having an alicyclic group in the molecule and adjacent carbon atoms of the alicyclic group forming an oxirane ring. An epoxy compound having at least one epoxycycloalkane group such as an epoxycyclohexane ring or an epoxycyclopentane ring may be used alone or in combination.

Suitable examples thereof include, but are not limited to:
Vinylcyclohexene diepoxide, vinylcyclohexene monoepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,
5-spiro-3,4-epoxy) cyclohexane-m-
Dioxane, bis (3,4-epoxycyclohexyl)
Such as adipate.

The cationic UV polymerization initiator used in combination with the above-mentioned epoxy resin has a function of decomposing by UV rays and releasing a Lewis acid, and this Lewis acid has a function of polymerizing an epoxy group. Examples thereof include aromatic iodonium salts, aromatic sulfonium salts, aromatic selenium salts, and aromatic diazonium salts.

Examples of diallyl iodonium salts include diphenyl iodonium hexafluoroantimonate, diphenyl iodonium hexaolophosphate, 4-chlorophenyl iodonium tetrafluoroborate, di (4-methoxyphenyl) iodonium chloride, (4-methoxyphenyl) phenyl. Examples thereof include iodonium.

Examples of the triarylsulfonium salt include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluorophosphate, p- (phenylthio) phenyldiphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroantimonate and 4-chloro. Examples thereof include phenyldiphenylsulfonium hexafluorophosphate.

Examples of the triaryl selenium salt include triphenyl selenium hexafluorophosphate, triphenyl selenium hexafluoroantimonate and the like.

As other cationic polymerization initiators,
(2,4-Cyclopentan-1-yl) [(1-methoxythiethyl) -benzene] -iron-hexafluorophosphate, diphenylsulfonium hexafluroantimonate, dialkylphenylsulfonium hexafluoroantimonate, dialkylphenylsulfonium Hexafluorophosphate, 4,4'-bis [di (βhydroxyethoxy) phenylsulfonio]
Phenyl sulfide-bis-hexafluoroantimonate, 4,4-bis [di (βhydroxyethoxy) phenylsulfonio] phenyl sulfide-bis-hexafluorophosphate and the like can be mentioned.

The cationically curable resin composition may contain a diluent known per se, other epoxy resin, sensitizer, crosslinking agent and the like.

Examples of the diluent include phenyl glycidyl ether, methylphenyl glycidyl ether, n-butyl glycidyl ether, and 1,2-epoxyhexadecane.

Other epoxy resins for modification include bisphenol type epoxy resins, that is, epoxy resins derived from bisphenols and epichlorhydrin.

Examples of the sensitizer for providing sensitivity in the near ultraviolet region include thioxanthone derivatives such as 2,4-diethylthioxanthone and 2,4-diisopropylthioxanthone.

As the crosslinking agent, various polyols such as ε-caprolactone triol can be mentioned.

Suitable examples of formulations of cationically curable resin compositions include, but are not limited to, cycloaliphatic epoxy resin 10
0.1 to 20 parts by weight, in particular 0.5 to 15 parts by weight, 0 to 50 parts by weight of diluent, especially 5 to 45 parts by weight, and 0 to 50 other epoxy resins per 0 parts by weight of the cationic UV polymerization initiator. Parts by weight, especially 5 to 45 parts by weight, sensitizer 0
To 20 parts by weight, in particular 0.5 to 10 parts by weight, and 0 to 50 parts by weight, especially 5 to 45 parts by weight of a crosslinking agent.

As the ultraviolet radical-polymerizable resin composition, a combination of an ultraviolet-polymerizable monomer or prepolymer and a photopolymerization catalyst is used.

As the UV polymerizable monomer or prepolymer, a monomer or prepolymer having a plurality of ethylenically unsaturated groups in the molecule or a mixture thereof is used. Suitable examples thereof are epoxy acrylate resin, urethane acrylate resin, polyester acrylate, thermosetting acrylic resin, thermosetting polyester resin and the like.

As the epoxy acrylate resin, an adduct of a bisphenol type epoxy resin and an ethylenically unsaturated carboxylic acid such as acrylic acid or methacrylic acid, or this adduct and an ethylenically unsaturated polycarboxylic acid anhydride, for example, A reaction product with maleic anhydride, itaconic anhydride, or the like is used.

As the urethane acrylate resin, a urethane acrylate resin obtained by reacting an isocyanate-terminated polyester or isocyanate-terminated polyol with a functional group-containing acrylic monomer such as acrylic acid, methacrylic acid or hydroxyethyl (meth) acrylate Is used.

As the thermosetting acrylic resin, 1,6-
Hexanediol diacrylate (HDDA), 1,6-hexanediol dimethacrylate (HDDMA), neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, ethylene glycol diacrylate (E
GDA), ethylene glycol dimethacrylate (EGDMA),
Polyethylene glycol diacrylate (PEGMA-A), polyethylene glycol diacrylate (PEGMA), polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate, pentaerythritol diacrylate, 1,4-butanediol di Acrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
Pentaerythritol triacrylate, dipentaerythritol hexaacrylate, tetramethylolmethane tetraacrylate, N, N, N ', N'-tetrakis (β
Acrylic ester of -hydroxyethyl) ethylenediamine, 2,2-bis [4- (3-methacryloyloxy-2-hydroxypropoxy) phenyl) propane and the like are used.

The thermosetting polyester resin is a polyester containing an ethylenically unsaturated bond in the molecule, for example, an ethylenically unsaturated polyvalent carboxylic acid such as maleic acid, fumaric acid, itaconic acid or tetrahydrophthalic acid. , Isophthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, combination with other acid components such as polymerized fatty acid, ethylene glycol, diethylene glycol, propylene glycol, glycerin, neopentyl glycol, trimethylolpropane, penta A polyester resin obtained by condensing a polyhydric alcohol such as erythritol and bisphenols is used.

The above-mentioned polyfunctional monomer or prepolymer is usually used in combination with a monofunctional monomer. Examples of such a monomer include glycidyl acrylate (GA), glycidyl methacrylate (GMA) and carbitol acrylate. , Tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, dicyclopentadienyl acrylate, dihydrodicyclopentadienyl methacrylate, isobornyl acrylate, acrylamide (AAm), methacrylamide (MAm),
N-methylol acrylamide (N-MAM), N-diacetone acrylamide (DAAM), N-vinylpyrrolidone, maleic acid, itaconic acid, methyl methacrylate (MMA), ethyl acrylate (EA), styrene (ST), acrylonitrile (AN ), Vinyl acetate (VAc), vinyltoluene (VT), etc.

Further, divinylbenzene, diallyl phthalate (DAP), diallyl isophthalate, diallyl adipate, diallyl glycolate, diallyl maleate, diallyl sebacate, triallyl phosphonate,
Other multifunctional monomers such as triallyl aconitate, trimellitic acid allyl ester, pyromellitic acid allyl ester may also be used. .

Typical photoradical polymerization initiators are benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and other benzoins and their alkyl ethers; acetophenone, 2,2-dimethoxy-2-phenylacetophenone. , 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2- Morpholino-Propane-
Acetophenones such as 1-one; Anthraquinones such as 2-methylanthraquinone and 2-amylanthraquinone; 2,4-Dimethylthioxanthone, 2,4-Diethylthioxanthone, 2-Chlorothioxanthone, 2,4
Thioxanthones such as diisopropylthioxanthone, ketals such as acetophenone dimethyl ketal, benzyl dimethyl ketal; benzophenones such as benzophenone or xanthones, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6 dimethoxybenzoyl) -2,4,4-Tri-
Examples include acylphosphine oxides such as methylpentylphosphine oxide.

Such a photopolymerization initiator can be used in combination with one or more known conventional photopolymerization accelerators such as benzoic acid type or tertiary amine type.

In the radical-polymerizable resin composition, the photopolymerization initiator is 0.1% by weight based on 100 parts by weight of the ultraviolet-curable resin.
It is preferable to use 1 to 30 parts by weight, preferably 1 to 25 parts by weight.

The titanium oxide-containing UV-curable coating used in the present invention comprises the above UV-curable resin composition containing rutile-type or anatase-type titanium dioxide and a coating aid. The amount of titanium dioxide compounded is 20 to 70 parts by weight, particularly 40 to 60 parts by weight, per 100 parts by weight of the resin composition. It is desirable that the viscosity is generally in the range of 200 to 800 centipoise (cp, 20 ° C.).

As the compounding agent for coating, use of silicone oil or the like as an antifoaming agent, fluorine-based surfactant, silicone-based surfactant, acrylic copolymer or the like as a leveling agent, thickener, thickener, etc. You can

In the present invention, a known coating means such as roller coating, gravure coating, spray coating, electrostatic coating or the like can be used for coating the titanium oxide-containing UV-curable coating, but roller coating, gravure coating, etc. Is advantageous. The coating thickness of the coating layer is preferably in the range of 2 to 20 μm.

As the ultraviolet ray used for curing the coating layer, a light ray having a wavelength of 200 to 440 nm, particularly 240 to 420 nm is used, including the near ultraviolet region. As the ultraviolet light source, a halide lamp, a high pressure mercury lamp, a low pressure mercury lamp or the like is used. Since the thickness of the coating layer is small, it is advantageous that the energy required for curing is considerably small, and an energy of 500 to 5000 joules / m ² or the like is generally sufficient.

The ink applied on the coating layer is
A coloring pigment is used instead of titanium oxide, while a finishing varnish not containing titanium oxide is used. These resin vehicles are UV curable,
Although any thermosetting type can be used, an ultraviolet curable type is preferable in the sense of minimizing the heat history.

Suitable examples of color pigments used in the ink are as follows. Black pigments Carbon black, acetylene black, run black, aniline black. Yellow pigment Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G,
Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake. Orange pigment Red lead yellow molybdenum, Molybden orange, Permanent orange GTR, Pyrazolone orange, Balkan orange, Induslen brilliant orange RK, Benzidine orange G, Induslen brilliant orange GK. Red pigment Bengal, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B. Purple pigment Manganese purple, fast violet B, methyl violet lake. Blue pigment Navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorinated compound, fast sky blue, indanthrene blue B
C. Green pigment chrome green, chrome oxide, pigment green B,
Malachite Green Rake, Fanal Yellow Green G. White pigment Zinc white, titanium oxide, antimony white, zinc sulfide. Extender barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white.

As the finishing varnish, the same varnish as the printing ink is used except that it does not contain a coloring pigment and is excellent in transparency. Its viscosity is generally 2
It is preferably in the range of 00 to 600 centipoise (cp, 20 ° C.).

In the present invention, the ultraviolet-curable ink can be printed by a known can-making printing method such as offset printing, lithographic printing, gravure printing and screen printing. On the other hand, the application of the UV curable finishing varnish
It can be performed using a gravure roll, a normal coating roll, or the like. The coating thickness of the finishing varnish is generally 2
To 20 μm is preferable.

Curing of the ink layer and the like can be carried out by using ultraviolet rays similarly to the curing of the white coat.

Neck-in processing and flanging processing of the printing cup are performed by means known per se. Neck-in processing is
Neck-in processing method known per se, for example, die method,
Alternatively, the spin neck-in method can be performed in one step or a plurality of steps.

The following formula (3) In the formula, RL represents the outer diameter of the can body before neck-in processing, and R
S represents the outer diameter of the can body of the neck-in processing part. Neck-in processing rate (NR) defined by 1.
It should be in the range of 01 to 1.10, particularly 1.02 to 1.07. It should be in the range.

It is recommended that the neck-in processing be performed at a temperature of 50 ° C. or higher and lower than the glass transition temperature (Tg) of the coating. That is, at a temperature above the Tg of the coating, the coating itself is scratched due to engagement between the coating and a tool, and on the other hand, at a temperature lower than 50 ° C, the coating causes plastic flow of the metal material during neck-in processing. And the coating defects such as the peeling of the coating and the generation of cracks are likely to occur. At the time of neck-in processing, it is optional that a lubricant or a lubricant can be applied to the can body that comes into contact with the tool, or that the surface of the tool that comes into contact with the can body can be formed of a material having excellent lubricating performance.

The neck-in processed cup engages the flanging die at its open end to perform flanging to form a flange for double winding with the can end.

The processed metal cup-shaped container is heated at a temperature not lower than the glass transition point (Tg) of the organic coating on the inner surface side, particularly preferably at a temperature not lower than Tg + 100 ° C., so that the neck-in processing and the flange processing portion can be heated. Effectively releases the strain remaining in the resin coating on the inner surface.

This heating may be performed on the entire container using a hot air heating furnace, an infrared heating furnace, or the like, or may be performed only on the neck-in processing of the cup and the flange processing portion or its vicinity.

[0099]

The present invention will be described in more detail with reference to the following examples. The methods for evaluating and measuring the container characteristics given in the examples are as follows.

(A) Crystallinity The density of the sample was determined using a density gradient tube. Thus, the crystallinity was calculated according to the following formula. (P-pa) / (pc -pa) × 100 p: Measurement Density (g / cmg ³⁾ pa: fully amorphous form Density (g / cmg ³⁾ pc: Complete crystal density (g / cmg ³⁾ polyethylene terephthalate In the case of pa = 1.335 (g / cmg ³ ), pc = 1.455 (g / cmg ³ ).

(B) Lightness (L) Using a color difference meter R-300 of Minolta Camera Co., Ltd., the L value (Hunter) of the outer surface of the side wall where the height from the bottom of the thin seamless can is 60 mm is measured. I asked.

(C) Impact resistance A corrosion model liquid (distilled water 1000
The solution was added with 5 g of citric acid, 5 g of acetic acid, and 30 g of sodium chloride), and the mixture was wound and stored at 7 ° C for 2 days.
As it was, it was dropped upright from a height of 30 cm, shock-deformed on the lower part of the can, and stored at 37 ° C. for 1 month, and the corrosion state of the deformed part was visually observed. The corrosion test due to drop deformation is performed for 100 cans under each condition described in Examples and Comparative Examples, and if there is at least one corrosion point of 1 mm ² or more, it is determined that there is corrosion, and there are 100 cans of corrosion. The impact resistance was evaluated by.

Example 1 Tin-free steel plate having a base plate thickness of 0.18 mm and a tempering degree of DR-9 (a surface treatment coating amount of metallic chromium of 120 m
g / m ² , chromium oxide amount 15 mg / m ² ) and a 20 μm-thick biaxially stretched polyethylene terephthalate / isophthalate copolymer film on the inner surface side, while titanium oxide on the outer surface side. A biaxially stretched polyethylene terephthalate / isophthalate copolymer film containing 20% by weight and having a thickness of 15 μm was heat-bonded simultaneously on both sides at the melting point of the film, and immediately water-cooled to obtain an organic coated metal plate.

After glamor wax was uniformly applied to this organic coated metal plate, it was punched into a disc having a diameter of 160 mm,
A shallow-drawn cup was molded according to a conventional method. The drawing ratio in this drawing process is 1.59.

Then, the primary and secondary redrawing processes were performed to obtain a thin-walled deep drawn cup. The molding conditions of the redrawing process and various properties of the redrawn deep drawn cup are shown below. Primary redraw ratio 1.23 Secondary redraw ratio 1.24 Redraw die working corner radius 0.30mm Redraw die holding corner radius 1.0mm Cup diameter 66mm Cup height 130mm Sidewall thickness Change rate -40%

Thereafter, after doming according to a conventional method, the deep-drawing cup was heat-treated at 215 ° C. for 1 minute to remove the processing strain of the film and volatilize the lubricant. Next, the edge of the opening is cut off, and an epoxy acrylate-based radical-curable UV-curable white coating containing 50% by weight of titanium oxide is applied to the entire outer side wall so that the dry coating amount is 200 mg / can and the output is 160 w. The white coating layer was cured by irradiating it with ultraviolet rays from a metal halide lamp of / cm. The white coating initiator is CGI-
A mixture of 1700 and Irgacure 184 (both manufactured by Ciba-Geigy Co., Ltd., trade name) was used.

Printing was performed on the outer side wall of this deep-drawing cup by a dry offset method using a polyester thermosetting ink, and further, an acrylic amino water-based thermosetting finishing varnish was dried at a coating amount of 150 mg / can. After coating the entire outer side wall with the wet-on-wet method, 2
Baking was performed at 05 ° C for 30 seconds. Next, the 66 mm opening end was reduced in diameter to 57 mm by a roll neck method, and flange processing was performed to obtain a thin seamless can for 350 ml. The area of the outer side wall of this can is 235c.
m ² . When printing, a design with many non-image areas was adopted so as not to interfere with the brightness measurement of the side wall of the can. Table 1 shows the characteristics of the thin seamless cans produced.
, The lightness (L value), which is an index of whiteness, was as high as 80, and a can with good impact resistance was obtained.

Example 2 Using the same organic coated metal plate as in Example 1, glamor wax was uniformly applied, and then punched into a disk having a diameter of 155 mm to form a shallow drawing cup according to a conventional method. The drawing ratio in this drawing process is 1.55. Then the first,
In the second redrawing process, the side wall was thinned to some extent.
In the second redrawing process, the side wall was thinned by ironing together with the ironing ring. The molding conditions of the redrawing process and various properties of the redrawn deep drawn cup are shown below. Primary redraw ratio 1.23 Secondary redraw ratio 1.24 Redraw die working corner radius 0.35mm Redraw die holding corner radius 1.5mm Ironing die clearance 0.10mm Cup diameter 66mm Cup height 132mm Side wall thickness change rate -45%

Then, after performing doming according to a conventional method, the deep-drawing cup was heat-treated at 215 ° C. for 1 minute to remove processing strain of the film and volatilize the lubricant. Next, the edge of the opening is trimmed, and an alicyclic epoxy-based cationically curable UV-curable white coating containing 50% by weight of titanium oxide is applied to the outer side wall so that the dry coating amount is 200 mg / can and the output is obtained. 16
The white coating layer was cured by irradiating it with ultraviolet rays from a 0 w / cm metal halide lamp. A mixture of a diaryliodonium salt-based initiator and a thioxanthone-based sensitizer was used as an initiator system in order to effectively cure the white coating.

Printing was carried out on the outer side wall of this deep-drawing cup by a dry offset method using a polyester thermosetting ink, and further, an acrylic amino water-based thermosetting finishing varnish had a dry coating amount of 150 mg / can. After coating the entire outer side wall with the wet-on-wet method, 2
Baking was performed at 05 ° C for 30 seconds. Next, the 66 mm opening end was reduced in diameter to 57 mm by a roll neck method, and flange processing was performed to obtain a thin seamless can for 350 ml. The area of the outer side wall of this can is 235c.
m ² . The print design is the same as in the first embodiment.

Various properties of the thin-walled seamless can thus produced are shown in Table 1. A can having a high lightness of 79 and a high whiteness and good impact resistance was obtained.

Example 3 A thin seamless can was produced in the same manner as in Example 1 except that the dry coating amount of the white coating layer was changed to 150 mg / can. As a result, as shown in Table 1, the L value was 77, which was lower than that in Example 1, but the whiteness was at a level at which there was no problem.

Comparative Example 1 A thin-walled seamless can was produced in the same manner as in Example 1 except that the white coating was not applied. The cans produced under these conditions were significantly lacking in whiteness.

Comparative Example 2 A thin-walled seamless can was produced in the same manner as in Example 2 except that white coating was not applied. The cans produced under these conditions were significantly lacking in whiteness.

Comparative Example 3 A thin seamless can was produced in the same manner as in Example 2 except that the dry coating amount of the white coating layer was changed to 80 mg / can. The cans produced under these conditions had an amount of titanium oxide per unit area outside the range of the present invention as shown in Table 1, and the whiteness was insufficient.

Comparative Example 4 The white coating was changed to an acrylic epoxy thermosetting paint containing 50% by weight of titanium oxide, and the temperature was changed to 210 ° C.
A thin-walled seamless can was produced in the same manner as in Example 2 except that the baking was performed for 2 minutes for curing. The cans produced under these conditions have sufficient whiteness as shown in Table 1, but have poor impact resistance.

Comparative Example 5 Example 1 was repeated except that the film adhered to the outer surface of the tin-free steel plate was changed to a biaxially oriented polyethylene terephthalate / isophthalate copolymer having a thickness of 30 μm and containing 20% by weight of titanium oxide. Similarly, a thinned seamless can was produced. In this case, as shown in the results in Table 1, there was no problem in terms of whiteness itself, but unevenness of whiteness occurred in the height direction of the can and there was no gloss, which was not practical as a white can.

Example 4 Tin-free steel plate having a base plate thickness of 0.18 mm and a tempering degree of DR-9 (the amount of metallic chromium as the surface treatment coating amount is 120 m)
g / m ² , the amount of chromium oxide was 15 mg / m ² ) and a biaxially stretched polyethylene terephthalate / isophthalate copolymer film having a thickness of 20 μm was formed on the side of the inner surface of the can, while a thickness of 15 μm was formed on the outer surface of the can. The biaxially stretched polyethylene terephthalate / isophthalate copolymer film was heat-bonded on both sides at the melting point of the film at the same time and immediately cooled with water to obtain an organic coated metal plate.

After glamor wax was uniformly applied to this organic coated metal plate, it was punched into a disk having a diameter of 187 mm,
A shallow-drawn cup was molded according to a conventional method. The drawing ratio in this drawing process is 1.4.

Then, the primary, secondary, and tertiary redrawing processes were performed to obtain a thin-walled deep-drawing cup. The molding conditions of the redrawing process and various properties of the redrawn deep drawn cup are shown below. Primary redraw ratio 1.25 Secondary redraw ratio 1.25 Third redraw ratio 1.25 Redraw die action Corner radius of curvature 0.40mm Cup diameter 66mm Cup height 140mm Sidewall thickness change rate- 20%

Then, after performing doming according to a conventional method, the deep-drawing cup was heat-treated at 215 ° C. for 1 minute to remove the processing distortion of the film and volatilize the lubricant. Then, the edge of the opening is cut off, and an epoxy acrylate-based radical-curable UV-curable white coating containing 50% by weight of titanium oxide is applied to the entire surface of the outer side wall so that the dry coating amount is 400 mg / can and the output is 160 w. The white coating layer was cured by irradiating it with ultraviolet rays from a metal halide lamp of / cm. The white coating initiator is CGI-
A mixture of 1700 and Irgacure 184 (both manufactured by Ciba-Geigy Co., Ltd., trade name) was used.

Printing was performed on the outer side wall of this deep-drawing cup by a dry offset method using a polyester thermosetting ink, and further, an acrylic amino water-based thermosetting finishing varnish had a dry coating amount of 150 mg / can. After coating the entire outer side wall with the wet-on-wet method, 2
Baking was performed at 05 ° C for 30 seconds. Next, the 66 mm opening end was reduced in diameter to 57 mm by a roll neck method, and flange processing was performed to obtain a thin seamless can for 350 ml. The area of the outer side wall of this can is 235c.
m ² . The print design is the same as in the first embodiment.

The cans produced under these conditions have a whiteness of L value of 82 as shown in Table 1 and a very good impact resistance.

Comparative Example 6 The white coating was changed to an acrylic epoxy thermosetting paint containing 50% by weight of titanium oxide, and the temperature was changed to 210 ° C.
A thin seamless can was prepared in the same manner as in Example 4 except that the baking was performed for 2 minutes to cure the can. The cans produced under these conditions have a sufficient whiteness as shown in Table 1, but the impact resistance is slightly deteriorated.

[0125]

[Table 1]

As shown in the above Examples and Comparative Examples, by utilizing the UV-curable white coating, unnecessary heat history is given to the can, so that the impact resistance is not deteriorated and the unit is easily treated. An outer surface coating containing 0.5 mg or more of titanium oxide per area (1 cm ² ) can be formed, and a thinned seamless can having excellent whiteness can be obtained.

[0127]

EFFECTS OF THE INVENTION By using the UV-curable coating, it is possible to avoid giving an extra heat history to the thermoplastic film on the inner surface, and to prevent deterioration of processability and deterioration of corrosion resistance and flavor retention due to it. In addition, it was possible to prevent the impact resistance of the entire thermoplastic film on the inner surface from being lowered, and to impart excellent whiteness and luster to the outer side wall portion, thereby enhancing the appearance characteristics and the commercial value.

[Brief description of drawings]

FIG. 1 is a diagram showing the reflectance of various titanium oxides at each wavelength.

FIG. 2 is a side view showing an example of a thinned seamless can of the present invention.

FIG. 3 is a sectional view showing an example of a sectional structure of a cup used in the present invention.

FIG. 4 is a sectional view showing another example of the sectional structure of the cup used in the present invention.

[Explanation of symbols]

 1 Thinned Seamless Can 2 Bottom 3 Sidewall 4 Neck 5 Flange 10 Cup 11 Metal Substrate 12 Inner Organic Coating 14 Outer Organic Coating 15a, 15b Adhesive Layer 16 Titanium Oxide UV Curing Coating Layer 17 Printing Ink Layer 18 Finishing Varnish layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C09D 7/12 PSK C23C 30/00 C (72) Inventor Yoshiki Watanabe Imaicho, Hodogaya-ku, Yokohama-shi, Kanagawa 166-19 (72) Inventor Yasuhiro Yukawa 6-7-27 Shimootachu, Nakahara-ku, Kawasaki-shi, Kanagawa

Claims (4)

[Claims] 1. In a thin seamless can of a resin-coated metal material, an inner surface side and an outer surface side coating of the metal material are made of a thermoplastic film, and a titanium oxide-containing UV-curable coating is formed on at least the outer surface side film layer of the side wall portion. The layer is provided in a thickness of 3 to 20 μm, so that the total amount of titanium oxide per unit area of the outer side wall is 0.5 mg /
A seamless can that is at least cm ² . 2. The seamless can according to claim 1, wherein the titanium oxide is rutile titanium dioxide. 3. The seamless can according to claim 1, wherein the thermoplastic film coated on the outer surface side is a titanium oxide-containing polyester film. 4. The seamless can according to claim 1, wherein the thickness of the side wall portion is reduced to 80% or less of the thickness of the bottom wall portion.