GB2219543A

GB2219543A - Thin-walled deep-draw-formed coated can and process for preparation thereof

Info

Publication number: GB2219543A
Application number: GB8910920A
Authority: GB
Inventors: Tetsuo Miyazawa; Kazuhiro Satoh; Seishichi Kobayashi
Original assignee: Toyo Seikan Kaisha Ltd
Current assignee: Toyo Seikan Group Holdings Ltd
Priority date: 1988-05-12
Filing date: 1989-05-12
Publication date: 1989-12-13
Also published as: GB8910920D0; JPH01284431A; JP2508799B2

Abstract

A thin-walled deep-draw-formed coated can is prepared by deep-draw-forming a precoated metal sheet, the coating of the precoated metal sheet being composed of a plasticizer-containing or internally plasticized thermosetting resin having a gel proportion of 30 to 90% as measured in methylethylketone at the boiling point thereof, an elongation of at least 200% as measured at 100 DEG C, a Young's modulus of 1 x 10<6> to 5 x 10<9> dyne/cm<2> as measured at 100 DEG C, and a chlorine content lower than 20% by weight in the resin. Formation of a shock line or occurrence of breaking or peeling of the coating can be prevented at the draw-forming step, and the corrosion resistance of the final can body is improved. The precoated metal sheet may comprise formation coatings 12a, 12b, an inner coating 13, a white outer coating 14 and a varnish 15. A redrawn cup 10 is formed from a predrawn cup 1 using a punch 4, holding member 2 and redrawing die 3. The entire draw ratio may be from 1.3 to 4.0. The thermosetting resin may comprise an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin or an amine resin. The coating may incorporate a lubricant. <IMAGE>

Description

THIN-WALLED DEEP-DRAW-FORMED COATED CAN AND PROCESS FOR PREPARATION THEREOF Background of the Invention (1) Field of the Invention The present invention relates to a thin-walled deep-draw-formed coated can and a process for the preparation thereof. More particularly, the present invention relates to a can which has an excellent corrosion resistance even though the can is prepared by deep-draw-forming a precoated metal sheet while reducing the thickness of a side wall by bending elongation, and also to a process for the preparation thereof.

(2) Description of the Related Art The preparation of a seamless can barrel by subjecting a coated metal sheet to drawing and redrawing has been conducted from old in the field of can manufacture. At this drawing and redrawing, plastic flow is caused in the metal sheet so that the dimension in the direction of the can height is increased but the dimension is reduced in the direction of the circumference of the can barrel. Accordingly, in the can barrel obtained by draw-redraw forming, the thickness of the side wall of the c-an barrel gradually increases toward the upper part from the lower part and the thickness is extremely large at the top end (open end) of the side wall.

In the method of draw-redraw forming of a coated metal sheet, it is known that the can sheet is drawformed into a deep-drawn cup having a small diameter by a curvature corner portion of a redrawing die and simultaneously, the side wall portion is bend-elongated to reduce the thickness of the side wall portion. For example, this method is disclosed in Japanese Unexamined Patent Publication No. 56-501442 and Japanese Unexamined Patent Publication No. 62-502181. Furthermore, as the paint for the preparation of a coated metal sheet, there are known a vinyl organosol paint, an epoxy paint, a polyester paint and an acrylic paint.

This preparation of a thin-walled deep-draw-formed coated can involves a problem in that the corrosion resistance of a coating formed on a metal sheet prior to deep-draw forming is drastically reduced by deep-draw forming. In the first place, a shock line is formed in a final thin-walled deep-draw-formed can. This shock line means a phenomenon in which the coating at the corner portion of the cup is caused to appear as a groove on the side wall of the can by draw forming of the former stage. Occurrence of this shock line results in degradation of the appearance characteristics of the can, and furthermore, since many microcracks are formed in the coating of this grooving line portion, corrosion of the metal sheet and dissolution of the metal into the content of the can are caused.

In the second place, at the thickness-reducing deep-draw forming, the coating fails to follow up with the plastic flow of the metal sheet, and breaking or peeling of the coating is caused. As pointed out hereinbefore, at the draw-redraw forming, plastic flow is caused so that the dimension is increased in the direction of the height of the can while the dimension is reduced in the direction of the circumference of the can, and moreover, reduction of the thickness is caused by bend elongation. A coating of a paint heretofore used for cans cannot endure such deformation, and breaking or peeling is caused.

Summary of the Invention It is therefore a primary object of the present invention to provide a thin-walled deep-draw-formed coated can prepared by deep-draw-forming a precoated metal sheet while reducing the thickness of the side wall portion, in which formation of the above-mentioned shock line or occurrence of breaking or peeling of the coating is prevented and the corrosion resistance of the can is prominently improved.

More specifically, in accordance with the present invention, there is provided a thin-walled deep-drawformed coated can prepared by deep-draw-forming a precoated sheet and having a reduced thickness in the side wall portion, wherein the coating of the precoated metal sheet is composed of a plasticizer-containing or internally plasticized thermosetting resin having a gel proportion of 30 to 90% as measured in methylethylketone at the boiling point thereof, an elongation of at least 200% as measured at 100 C, a Young's modulus of 1 x 106 to 5 x 109 dyne/cm as measured at 100 c and a chlorine content lower than 20% by weight in the resin.

Furthermore, in accordance with the present invention, there is provided a process for the preparation of a thin-walled deep-draw-formed coated can, which comprises preparing a predrawn cup from a precoated metal sheet holding the predrawn cup by an annular holding member inserted in the cup and a redrawing die, and relatively moving a redrawing punch, which is arranged coaxially with the holding member and redrawing die so that the redrawing punch can enter into the holding member and come out therefrom, and the redrawing die so that the redrawing punch and redrawing die engage with each other, to form the predrawn cup into a deep-drawn cup having a diameter smaller than the diameter of the predrawn cup, wherein a metal sheet having a coating composed of a plasticizer-containing or internally plasticized thermosetting resin having a gel proportion of 30 to 90% as measured in methylethylketone at the boiling point thereof, an elongation of at least 200% as measured at 100 C, a Young's modulus of 1 x 106 to 5 x 109 dyne/cm as measured at 100 C and a chlorine content lower than 20% by weight in the resin is used as the precoated metal sheet, and the predrawn cup is formed into the deep-drawn cup while bend-elongating the predrawn cup through the redrawing die at a temperature higher than the glass transition temperature of the thermosetting resin coating.

The present invention is effectively applied to a thin-walled deep-draw-formed coated can in which the entire draw ratio is 1.3 to 4.0, especially 1.5 to 3.5, and the thickness of the side wall portion is 5 to 40%, especially 10 to 30%, of the thickness of the blank on the average.

The thermosetting resin coating used In the present invention comprises (i) a coating-forming component selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amine resin and (ii) a coating-forming component other than the coatingforming component (i), which shows a curing action to the coating-forming component (i) and is selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin, and a resin component which is internally plasticized by a long-chain alkyl group present in the molecule is used as at least one of the coating-forming components (i) and (ii), or (iii) a plasticizer is externally incorporated.

Brief Description of the Drawings Fig. 1 is a sectional view illustrating one example of the- precoated metal sheet preferably used in the present invention.

Fig. 2 is a sectional view illustrating steps of the forming process of the present invention.

Fig. 3 is a sectional view illustrating the redrawing step in the process of the present invention.

Fig. 4 is a diagram illustrating the relation between the curvature radius Rd of an operating corner portion and the thickness change ratio Et.

Incidentally, reference numerals in the drawings represent the following members.

1: predrawn cup, 2: annular holding member, 3: redrawing die, 4: redrawing punch, 6: curvature corner portion of annular holding member, 9: operating corner portion of redrawing die, 10: deep-drawn cup, 11: metal substrate, 12a and 12b: formation coatings, 13: inner face coating, 14: white coating, 15: transparent varnish, 20: disk, 21, 24 and 27: bottoms, 22, 25 and 28: side walls, 23: shallow-drawn cup, 26: redrawn cup, 29: deep-drawn cup Detailed Description of the Preferred Embodiments It is basically important that the precoated metal sheet should comprise a coating of a plasticizercontaining or internally plasticized thermosetting resin. In view of the adhesion to the metal sheet or the barrier property to a corrosive component, it is indispensable that the coating should be composed of a thermosetting resin.However, in case of an ordinary thermosetting resin, it is substantially impossible to produce sufficient plastic flow in the coating at the thickness-reducing deep-draw forming. In the present invention, by internally plasticizing this thermosetting resin or externally plasticizing the thermosetting resin by incorporation of a plasticizer, a property capable of following up with the plastic flow of the metal sheet is imparted to the coating.

In order to prevent formation of a shock line or occurrence of breaking or peeling of the coating, it is important that the coating should have a certain degree of crosslinking (network). More specifically, it is indispensable that the coating should have a gel proportion of 30 to 90%, especially 40 to 90%, as measured in methylethylketone (MEK) at the boiling thereof. If the gel proportion as measured in MEK is lower than 30%, formation of a shock line can hardly be prevented and the corrosion resistance (the barrier property to a corrosive component) of the coating per se is degraded. If the gel proportion as measured in MEK is higher than 90%, breaking or peeling of the coating is caused.This means that in order to prevent flow of the resin from a portion other than the portion being formed, a certain network structure is necessary within a range allowing plastic flow in said portion being formed.

Moreover, it is important that the coating should have an elongation of at least 200% as measured at 100 C and a Young's modulus of 1 x 106 to 5 x 109 dyne/cm2 especially 1 x 106 to 2 x 109 dyne/cm2, as measured at 100 C. The reason why the elongation and Young's modulus as measured at 100 C are regarded as important factors in the instant specification is that at the thickness-reducing deep-draw-forming, the temperature of the coating is elevated to a level close to the above temperature by internal friction at the deformation.In case of an epoxy/phenolic paint customarily used for a draw-redraw-formed can, the elongation at the abovementioned temperature in the order of scores of % and the coating cannot follow up with the thickness-reducing deep-draw forming of the present invention. In contrast, according to the present invention, by adjusting the elongation at the above-mentioned temperature to at least 200%, a minimum and necessary processability can be maintained. It also is important that the Young's modulus at the above-mentioned 6 temperature should be 1 x 10 to 5 x 109 dyne/cm. If the Young's modulus is too high and exceeds this range, internal stress is left in the coating after the forming, and the coating is shrunk with the lapse of time or by a post treatment, and peeling or breaking is often caused.If the Young's modulus is too low and below the above-mentioned range, breaking of the coating is caused during the forming, and the continuity is lost in the coating or microcracks are formed in the coating even if the continuity is not lost.

In the coating of the present invention, the chlorine content in the resin should be lower than 20% by weight. If the chlorine content in the resin exceeds 20%, s hydrogen chloride is already generated at the step of baking (cross-linking) the coating, and troubles such as corrosion of the iron surface are caused by hydrogen chloride generated by decomposition with the lapse of time after the processing or at the retort sterilization.

According to the present invention, by using an internally or externally plasticized thermosetting resin coating, formation of a shock line or occurrence of breaking or peeling of the coating can be prevented, the formability of the precoated metal sheet at the thickness-reducing deep-draw forming can be improved, and the corrosion resistance of the final can body can be prominently improved.

The present invention will now be described in detail.

Paint In the present invention, an internally or externally plasticized thermosetting resin paint is used. This thermosetting resin comprises at least two kinds of resin components capable of reacting with each other to form a crosslinked structure. As the functional group capable of forming a cross-linked structure, there can be mentioned an alcoholic hydroxyl group, a phenolic hydroxyl group, an etherified methylol group, an amino group, an amide group, a carboxyl group, a carboxylic anhydride group and an epoxy group. Resin components having such functional groups can be used.

As one resin component, (i) a coating-forming component selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin is used, and as the other resin component, (ii) a coatingforming component other than the coating-forming component (i), which shows a curing action to the coating-forming component (i) and is selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin, is used.

As the acrylic resin, there can be used acrylic resins comprising main structural units of an alkyl methacrylate or acrylate such as ethyl acrylate or methyl methacrylate and functional group-containing units of an ethylenically unsaturated carboxylic acid or its anhydride such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, itaconic acid or citraconic acid, a hydroxyl group-containing methacrylate or acrylate such as hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate or hydroxypropyl acrylate, or an amino group-containing methacrylate or acrylate such as aminoethyl methacrylate, aminoethyl acrylate, aminopropyl methacrylate, aminopropyl acrylate, Naminoethylamino methacrylate or N-aminoethylamino acrylate.

As the vinyl resin, there can be used vinyl resins comprising main structural units of vinyl chloride or vinyl acetate and functional group-containing units of an ethylenically unsaturated carboxylic acid or its anhydride as mentioned above, a hydroxyl groupcontaining methacrylate or acrylate as mentioned above, or vinyl alcohol.

As the polyester resin, there can be mentioned polyester resins for paints, which have a hydroxyl group or carboxyl group at the terminals or side chains and have a polyfunctionality such as a bifunctionality, a trifunctionality or a higher functionality. For example, a polyester resin obtained by condensing an acid component such as isophthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid or a polymerized fatty acid with a polyhydric alcohol such as ethylene glycol, diethylene glycol, propylene glycol, glycerol, neopentyl glycol, trimethylolpropane, pentaerythritol or bisphenol A can be used.

As the polyamide resin, there can be used polyamide resins for paints, which have an amino group or carboxyl group at the terminals or side chains and a polyfunctionality such as a bifunctionality, a trifunctionality or a higher functionality. For example, a polyamide obtained by polycondensing a polymerized fatty acid (dimer acid) or a polymerized fatty acid and a dibasic acid such as adipic acid or sebacic acid with a diamine such as ethylene diamine or tetramethylene diamine can be used.

As the epoxy resin, there can be used epoxyterminated phenols obtained by condensing an epihalohydrin with a polyhydric phenol such as bisphenol 2,2-bis(4-hydroxyphenyl)propane). Such epoxy resins having an epoxy equivalent of 2,000 to 10,000, especially 2,500 to 8,000, are preferably used.

As the phenolic resin, there can be used resol resins obtained by condensing a monocyclic or polycyclic phenol with formaldehyde in the presence of an alkaline catalyst, that is, methylol group-containing resins, and resins obtained by etherifying this methylol group with butanol or the like. It is generally preferred that the molecular weight of the phenolic resin be 500 to 2,000.

As the amino resin, there can be used resins formed by polycondensing a nitrogen-containing compound such- as urea, melamine, guanamine or benzoguanamine with formamide in the presence of an alkaline catalyst and, if desired, etherifying the methylol group of the obtained resin with an alcohol such as butanol. It is generally preferred that the molecular weight of the amino resin be 1,000 to 2,000.

At least two of the foregoing resins are combined so that one resin acts as a curing agent for the other resin. For example, in the case where one resin is an epoxy resin, at least one of resins acting as an epoxy resin-curing agent, such as acrylic resins, vinyl resins, polyamide resins, polyester resins, phenolic resins and amino resins, is used and combined with the epoxy resin. Curable resins of this type are especially excellent in the adhesion to a metal sheet. It is preferred that the epoxy resin/curing agent resin weight ratio be in the range of from 70/30 to 99/1, especially from 80/20 to 98/2.

The internal plasticization of the thermosetting resin component is accomplished by incorporation of a long-chain alkyl group, ordinarily an alkyl group having 6 to 36 carbon atoms, especially 8 to 36 carbon atoms, in the main chain, side chain or terminals of the resin.

For example, in case of an acrylic resin or vinyl resin, the internal plasticization can be accomplished by including a methacrylic or acrylic acid ester having a long-chain alkyl group into the polymer chain. In case of a polyester or polyamide resin, the internal plasticization is accomplished by using a polymerized fatty acid or long-chain alkyl dicarboxylate as the carboxylic acid component or using a long-chain alkylene diol or long-chain alkylene diamine and including such a component into the polymer chain. Furthermore, in case of an epoxy resin, a phenolic resin or an amino resin, the internal plasticization can be accomplished by modification with a fatty acid, a polymerized fatty acid, a drying oil, a resin acid or a resin.

The degree of the internal plasticization of the resin is changed according to the kind of the resin and the combination of the resins, but it is sufficient if the long-chain aliphatic hydrocarbon group is contained in an amount of 1 to 50% by weight, especially 1 to 40 by weight, based on the resin.

In the present invention, the external plasticization by addition of a plasticizer is carried out instead of the internal plasticization or simultaneously with the internal plasticization. As the plasticizer preferably used for the external plasticization, there can be mentioned polyester type plasticizers such as poly-(diethylene glycol/terpenemaleic anhydride) -ester, poly- (propylene glycol/adipic acid)-ester, poly-(1,3-butanediol/ adipic acid)-ester, poly-(propylene glycol/sebacic acid)ester, poly-(propylene glycol/phthalic acid)-ester, poly (1,3-butanediol/phthalic acid)-ester, poly- (ethylene glycol/adipic acid)-ester, poly-(1 ,6-hexane-diol/adipic acid)-ester and acetylated poly-(butanediol/adipic acid)-ester, epoxy type plasticizers such as epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, epoxidized safflower oil, epoxidized butyl linseed oil fatty acid and epoxidized octyl stearate, and acidmodified waxes such as maleic anhydride-modified polyethylene wax, maleic anhydride-modified polypropylene wax and oxidized polyethylene.

Of course, phthalic acid esters, aliphatic dibasic esters, phosphoric acid esters, fatty acid esters and polyhydric alcohol esters can be used, though the capacity is relatively low.

In case of the external plasticization, it is preferred that the plasticizer be used in an amount of 1 to 50% by weight, especially 1 to 40% by weight, based on the resin.

Precoated Metal Sheet In the present invention, various surface-treated steel sheets and sheets of light metals such as aluminum can be used as the metal sheet.

As the surface-treated steel sheet, there can be used a surface-treated steel sheet obtained by annealing a cold-rolled steel sheet, subjecting the annealed steel sheet to secondary cold rolling, and subjecting the cold-rolled steel sheet to at least one of surface treatments such as zinc plating, tin plating, nickel plating, electrolytic chromate treatment and chromate treatment. As a preferred example of the surfacetreated steel sheet, there can be mentioned an electrolytically chromate-treated steel sheet, and especially, an electrolytically chromate-treated steel sheet comprising 10 to 200 mg/m of a metallic chromium layer and 1 to 50 mg/m (calculated as metallic chromium) of a chromium oxide layer is excellent in the combination of the coating adhesion and the corrosion resistance. Another example of the surface-treated steel sheet is a hard tinplate having a tin diposition amount of 0.5 to 11.2 g/m2. It is preferred that this tinplate be subjected to a chromate treatment or a chromate-phosphate treatment so that the chromium amount is 1 to 30 mg/m2 calculated as metallic chromium.

Not only a pure aluminum sheet but also an aluminum alloy sheet can be used as the light metal sheet. An aluminum alloy sheet excellent in the corrosion resistance and processability comprises 0.2 to 1.5to by weight of Mn, 0.8 to 5% by weight of Mg, 0.25 to 0.3% by weight of Zn and 0.15 to 0.25% by weight of Cu, with the balance being A. It is preferred that the light metal sheet be subjected to a chromate treatment or a chromate-phosphate treatment so that the chromium amount is 20 to 300 mg/g2 calculated as metallic chromium.

The blank thickness (tB) of the metal sheet is changed according to the kind of the metal and the use or size of the final vessel, but it is generally preferred that the blank thickness be 0.10 to 0.50 mm and it is especially preferred that the blank thickness be 0.10 to 0.30 mm in case of a surface-treated steel sheet and 0.15 to 0.40 mm in case of a light metal sheet.

The present invention is advantageous in that a protecting coating of the above-mentioned resin is applied to the metal sheet prior to the draw forming and the deep-draw firming and the uniform reduction of the thickness of the side wall can be simultaneously accomplished without damaging this protecting coating layer.

The above-mentioned resin paint is applied to the metal blank in the form of an organic solvent solution such as an enamel or lacquer or an aqueous dispersion or aqueous solution by roller coating, spray coating, dip coating, electro-coating or electrophoretic coating. Of course, if the resin paint is heat-curable, the paint is baked according to need. In view of the corrosion resistance and processability, it is preferred that the thickness (dry state) of the protective coating be 2 to 50,um, especially 3 to 40 sum. A lubricant can be incorporated in the coating for improving the drawredraw-formability.

An example of the coated metal sheet preferably used in the present invention is illustrated in Fig. 1.

Referring to Fig. 1, formation films 12a and 12b such as chromate treatment coatings are formed on both the surfaces of a metal substrate 11, and an inner surface coating 13 is formed through the formation film 12a on the surface to be formed into the inner surface of the final can. An outer face coating comprising a white coating 14 and a transparent varnish 15 is formed through the formation coating 12b on the surface to be formed into the outer surface of the can.

Thickness-Reducing Deep-Draw Forming Referring to Fig. 2 illustrating the forming process, the above-mentioned coated metal sheet is punched into a disk 20 having a thickness tB at the punching step. Then, at the drawing step, the disk 20 is formed into a shallow-draw-formed vessel 23 comprising a bottom portion 21 having a thickness of tB and a large diameter and a side wall portion 22 having a thickness tw, and a low height. The draw ratio tsee formula (8) given hereinafter) at this drawing step is preferably 1.2 to 1.9 and especially preferably 1.3 to 1.8. The thickness tw, of the side wall portion is slightly larger than tB Then, at the primary redrawing step, the shallowdraw-formed cup 23 is subjected to redraw-forming as described hereinafter.

Referring to Fig. 3 illustrating the redrawing step of the process of the present invention, a predrawn cup 1 formed from the coated metal sheet is held by an annular holding member 2 inserted in this cup 1 and a redrawing die 3 located below, and a redrawing punch 4 is arranged coaxially with the holding member 2 and redrawing die 3 so that the redrawing punch 4 can enter into the holding member 2 and come out therefrom. The redrawing punch 4 and redrawing die 3 are relatively moved so that they engage with each other.

By this relative movement, the side wall portion of the predrawn cup 1 is vertically bent inwardly of the diameter through a curvature corner portion 6 of the annular holding member 2 from the outer circumferential surface 5 thereof, is passed through a zone defined by the annular bottom face 7 of the annular holding member 2 and the top face 8 of the redrawing die 3 and is bent substantially vertically to the axial direction by an operating corner portion 9 of the redrawing die 3, whereby a deep-draw-formed cup 10 having a diameter smaller than the diameter of the predrawn cup 1 is prepared and simultaneously, the thickness of the side wall portion is reduced by bend elongation.

In this case, if the curvature radius Rd of the operating corner portion of the redrawing die is adjusted to 100 to 290%, especially 150 to 290%, of the blank thickness tg of the metal sheet, reduction of the thickness of the side wall portion by bend elongation is effectively accomplished, and simultaneously, the difference of the thickness between the upper and lower parts of the side wall portion is eliminated and the thickness is uniformly reduced in the entire side wall portion. This point will now be explained.

Referring to Fig. 3 illustrating the principle of the bend elongation, the coated metal sheet is forcibly bent under a sufficient back tension along the operating corner portion 9 of the redrawing die having the curvature radius Rd. In this case, no strain is produced on the face of the coated metal sheet on the side of the operating corner but the face on the side opposite to the operating corner undergoes a strain. Supposing that the curvature radius of the operating corner portion is Rd and the sheet thickness is t, this strain quantity Es is given by the following formula:

The face (inner face) of the coated metal sheet is elongated by s at the operating corner portion, while the other face (outer surface) is elongated by the same amount as Es just below the operating corner portion by the back tension.Since the coated metal sheet is bendelongated in the above-mentioned manner, the thickness of the coated metal sheet is reduced, and this thickness change ratio St is given by the following formula:

From the above formula (2), it is seen that reduction of the curvature radius Rd of the operating corner portion is effective for reducing the thickness of the coated metal sheet, that is, the smaller is Rd, the larger is the thickness change lett. Supposing that the curvature radius Rd is constant, the larger is the thickness t of the coated metal sheet passing through the operating corner portion, the larger is the thickness change IE;tl.

Fig. 4 is a graph illustrating the relation between the curvature radius Rd of the operating corner portion and the thickness change ratio Et, which is observed when the thickness t of the coated metal sheet is changed, where the thickness change ratio Et is plotted on the ordinate and the curvature radius Rd is plotted on the abscissa. The results shown in Fig. 4 are well in agreement with the above-mentioned fact.

Supposing that the thickness of the coated metal sheet supplied to the operating corner is to and the thickness reduced by the bend elongation is tl, this thickness tl is given by the following formula:

Incidentally, the thickness at the upper part of the side wall portion of the predrawn cup is increased beyond the standard thickness (blank thickness) tB by the influence of compression in the radial direction, and this thickness Is expressed by the following formula:

wherein o( stands for the thickness index.

Accordingly, in this case, the reduced thickness tl is expressed by the following formula:

Therefore, the ratio (Ratio) between t1 in case of i = 0 and tl in case ofS &num; 0 is expressed by the following formula:

From the above-mentioned formula (6), it is understood that reduction of Rd results in a function of controlling the thickness change in the bend-elongated side wall portion to a small value. For example, in the case where tB is equal to 0.18 mm and i is 0.1, when Rd is 2 mm, the value of Ratio is 1.091, but when Rd is 0.5 mm, the value of Ratio is 1.072. Namely, it is understood that reduction of Rd is effective for controlling the thickness change and uniformalizing the thickness.

In other words, since the thickness ratio between the standard thickness (tB) and the thickness of the predrawn cup is (1 +o(), and therefore, the ratio of control of the thickness change is given by the following formula:

When the value of the formula (7) is calculated with respect to the above-mentioned examples, it is seen that if Rd is 2 mm, the value of the formula (7) is 0.009 and if Rd is 0.5 mm, the value of the formula (7) is 0.028.

Thus, it is confirmed that the effect in the latter case is about 3.2 times as high as the effect in the former case.

As is apparent from the foregoing illustration, reduction of the curvature radius (Rd) of the operating corner portion of the redrawing die is effective for uniformalizing the thickness of the side wall portion after the bend elongation. If the value of Rd is too large and exceeds the above-mentioned range, it often happens that the degree of reduction of the thickness of the side wall portion and the uniformity of the thickness of the side wall portion are not satisfactory.

If the value of Rd is too small and below the abovementioned range, material breaking is often caused at the operating corner portion of the die at the redrawing step.

It is preferred that the draw-forming be carried out under such conditions that the curvature radius (Rh) of the holding corner portion 6 of the holding member 2 is 4.1 to 12 times, especially 4.1 to 11 times, the blank thickness (tB) of the metal coated thickness, the plane portions to be engaged with the predrawn cup in the holding member 2 and the redrawing die 3 have a dynamic friction coefficient ( ) of 0.001 to 0.20, especially 0.001 to 0.10, and the draw ratio defined by the ratio of the diameter of the shallow-draw-formed cup to the diameter of the deep-draw-formed cup is 1.1 to 1.5, especially 1.15 to 1.45. These conditions will now be described.

In order to attain sufficient bend elongation at the operating corner portion of the redrawing die, it is necessary that a back tension sufficient to supply the metal sheet should be given while the metal sheet is bent precisely along this operating corner portion.

This back tension is given as the sum of (1) the load for forming the side wall portion of the predrawn cup into a flat sheet, (2) a substantial blank holder load and (3) a load of the resistance to deformation of the predrawn cup to the deep-drawn cup. The sum of these three forces should not be so great as causing breaking of the metal sheet, and in order to perform the bend elongation effectively, it is required that a certain balance should be maintained among these three forces.

The curvature radius Rh of the holding corner portion 6 has relations to the above-mentioned forming load (1) and the formability. More specifically, if the curvature radius Rh of the holding corner portion 6 is too small and below the above-mentioned range, breaking of the metal sheet and damage of the coating are often caused. If the curvature radius Rh is too large and exceeds the above-mentioned range, wrinkles are readily formed. In each case, no satisfactory redraw-forming can be accomplished. However, if this curvature radius Rh is controlled within the range specified in the present invention, it is possible to perform redrawforming smoothly while imparting a sufficient back tension.

The dynamic friction coefficient Ul) of the annular face 7 of the holding member 2 and the annular face 8 of the redrawing die 3 has a relation to the substantial blank holder force (2). The substantial blank holder force referred to herein is the force of effectively preventing formation of wrinkles by the shrinkage of the dimension of the metal sheet in the circumferential direction, and this force is expressed by the product of the force applied between the holding member and the redrawing die and the dynamic friction coefficient (P) of the foregoing faces.If the dynamic friction coefficient ( ) is too large and exceeds the abovementioned range, necking breaking is often caused in the metal sheet, and if the dynamic friction coefficient 0A) is too small and below the above-mentioned range, prevention of formation of wrinkles becomes difficult.

If the dynamic friction coefficient ( ) is controlled within the above-mentioned range, it becomes possible to give a back tension necessary for the bend elongation while preventing formation of wrinkles and occurrence of breaking of the metal sheet.

The redraw ratio defined by the ratio of the diameter (b) of the shallow-drawn cup to the diameter (a) of the deep-drawn cup has a relation to the load (3) of resistance to deformation. If this redraw ratio (b/a) is too low and below the range specified in the present invention, the object to manufacture a deepdraw-formed can is hardly attained, and it becomes difficult to give a large back tension necessary for the bend elongation. If the redraw ratio (b/a) is too high and exceeds the above-mentioned range, the deformation resistance becomes too large and breaking of the metal sheet is often caused at the bend elongation. In contrast, if the redraw ratio (b/a) is maintained within the above-mentioned range, deep-draw forming can be performed at a high efficiency while preventing breaking of the metal sheet, and a back tension necessary for high bend elongation can be imparted.

As is apparent from the foregoing illustration, by controlling the curvature radius (Rd) of the corner portion of the redrawing die to a small value, controlling the curvature radius (Rh) of the corner portion of the holding member to a large value, adjusting the dynamic friction coefficient (r) of the holding member and die and the redraw ratio (b/a) within the specific ranges and combining these conditions, deep-draw forming, reduction of the thickness of the side wall portion and uniformalization of the thickness are rendered possible. Furthermore, if the redrawing operation is carried out in multiple stages, for example, in 1 to 4 stages, the thickness of the side wall portion can be further uniformalized.

According to the present invention, since the above-mentioned precoated metal sheet is used, a deepdrawn can having an entire draw ratio of 2.0 to 4.0, especially 2.0 to 3.5, can be obtained.

The draw ratio referred to herein is a value defined by the following formula: raw ratio = (blank diameter)/(deep-draw can diameter)(8) According to the present invention, the thickness of the side wall portion of the can is able to be reduced to 60 to 95%, especially 65 to 90%, of the blank thickness (tB) on the average, and the ratio (tu/tb) of the thickness (tu) of the upper part of the side wall portion where the thickness is most easily reduced, to the thickness (tL) of the lower part of the side wall portion can be reduced below 1.5, especially 1.0 to 1.4, whereby the thickness of the side portion can be uniformalized without an ironing operation.In the draw-redraw-formed can of the present invention, since the thickness is reduced without ironing the entire side wall portion, the covering degree is complete, and the can of the present invention is characterized in that the enamel rater value (mA) of the upper part of the side wall portion is smaller than 5 times the enamel rater value (mA) of the lower part of the side wall portion, especially 1 to 4 times the enamel rater value (mA) of the lower part of the side wall portion.

Referring to Fig. 2 again, by the redraw forming, there is provided a redrawn cup 26 comprising a bottom portion 24 having a thickness of tg B and a diameter smaller than that of the shallow-draw-formed cup and a side wall portion 25 having a thickness of tw, and a height larger than that of the shallow-draw-formed cup.

The side wall portion of the redraw cup 26 is bendelongated according to the above-mentioned principle, and the thickness tw of this cup 26 is smaller than tB and tw,.

In general, this redrawing operation is carried out in a plurality of stages. If the redrawing operation is carried out in a plurality of stages, the thickness of the side wall portion is further reduced and the thickness is more uniformalized throughout the side wall portion. At the final n-th redrawing step, a deep-drawformed can 29 comprising a bottom portion 27 having a thickness tg B and a small diameter and a side wall portion 28 having a thickness tw,,, and a long height is obtained. The characteristic values of this can are as described above.

The above-mentioned metal or cup can be coated with a lubricant such as liquid paraffin, synthetic paraffin , edible oil, hydrogenated edible oil, palm oil, natural wax or polyethylene wax prior to the draw forming or redraw forming. The amount coated of the lubricant is changed according to the kind of the lubricant, but it is preffered that the amount coated of the lubricant be 0.1 to 10 mg/dm, especially 0.2 to 5 mg/dm2. The coating operation is performed by melting the lubricant and spraying the melt.

The formed can be subjected to various processing treatments such as trimming of a flange, doming, neck-in processing and flanging to form acas barrel for a twopiece canned product.

According to the present invention, when a precoated metal sheet is deep-draw-formed while the thickness of the side wall portion is reduced by bend elongation, by using an internally plasticized or externally plasticized thermosetting resin coating, formation of a shock line or breaking or peeling of the coating is prevented at the draw-forming step, and the adaptability of the precoated metal sheet to reduction of the thickness and the deep-draw forming can be improved, and the corrosion resistance of a final can body can be prominently improved.

The present invention will now be described in detail with reference to the following examples that by no means limit the scope of the invention.

The phenolic resins used in the examples were prepared in the following manner.

Preparation of Phenol-Formaldehyde Resins (1) A reaction vessel was charged with a mixed phenol comprising 0.2 mole of p-cresol, 0.3 mole of bisphenol A and 0.5 mole of p-octylphenol and 1.2 mole of formaldehyde in the form of a 372 aqueous solution, and the mixture was heated at 50 C with stirring to form a solution. Then, 0.2 mole of diethanolamine in the form of a 25% aqueous solution was added to the above solution, and the temperature was elevated to 90 C and reaction was carried out for 2 hours. Then, a mixed solvent comprising 30 parts of methylethylketone, 20 parts of cyclohexanone and 50 parts of xylene was added to the reaction mixture to extract the condensation product. The condensation product was washed with deionized water two times.The water layer was removed and a small amount of residual water was removed by azeotropic distillation. The residue was cooled to obtain a 30% solution of a phenol-aldehyde resin (phenolic resin A).

(2) A reaction vessel was charged with 1.0 mole of bisphenol A and 2.4 moles of formaldehyde in the form of a 37% aqueous solution, and the mixture was heated at 50 C with stirring to form a solution. Then, 0.1 mole of magnesium hydroxide was added to the solution, and the temperature was elevated to 90 C and reaction was carried out for 1 hour. Then, a mixed solvent comprising 30 parts by weight of methylethylketone, 20 parts of cyclohexanone and 50 parts of xylene was added to the reaction mixture to extract the condensation product, and the condensed product was washed with deionized water two water and the water layer was removed. A small amount of residual water was removed by azeotropic distillation and the residue was cooled to obtained a 30% solution of a phenol-aldehyde resin (phenolic resin B).

(3) A reaction vessel was charged with a mixed phenol comprising 0.5 mole of o-cresol and 0.5 mole of p-cresol and 1.2 moles of formaldehyde in the form of a 37% aqueous solution, and the mixture was heated at 50 C with stirring to form a solution. Then, 0.1 mole of magnesium hydroxide was added to the solution, and the temperature was elevated to 90 C and reaction was carried out for 1 hour. Then, a mixed solvent comprising 30 parts of methylethylketone, 20 parts of cyclohexanone and 50 parts of xylene was added to the reaction mixture to extract the condensation product.

The condensation product was washed with deionized water two times and the water layer was removed, and a small amount of residual water was removed by azeotropic distillation. The residue was cooled to obtain a 30 solution of a phenolaldehyde resin (phenolic resin C).

Preparation of Paints Precoating paints A through D according to the present invention and comparative precoating paints E through I outside the scope of the present invention are described below.

Resin Components of Paint A Epikote 1009 (supplied by Yuka-Shell 45 parts Epoxy K.K.) PKHH (phenoxy resin supplied by 45 parts Union Carbide Corporation) Phenolic resin A 10 parts Resin components of Paint B Epikote 1009 (supplied by Yuka-Shell 47 parts Epoxy K.K.) PKHH (supplied by Union Carbide 47 parts Corporation) Phenolix resin A 6 parts Resin components of Paint C Epikote 1009 (supplied by Yuka-Shell 32 parts Epoxy K.K.) PKHH (supplied by Union Carbide 32 parts Corporation) Phenolix resin B 6 parts Byron 200 (polyester type plasticizer 30 parts supplied by Toyobo K.K) Resin components of Paint D Epikote 1009 (supplied by Yuka-Shell 60 parts Epoxy K.K.) Sumilit EX-13 (vinyl chloride resin 30 parts supplied by Sumitomo Kagaku K.K.) Phenolix resin A 10 parts Resin components of Paint E Epikote 1009 (supplied by Yuka-Shell 35 parts Epoxy K.K.) PKHH (supplied by Union Carbide 35 parts Corporation) Phenolix resin B 30 parts Resin components of Paint F Epikote 1009 (supplied by Yuka-Shell 95 parts Epoxy K.K.) Phenolic resin B 5 parts Resin components of Paint G Epikote 1009 (supplied by Yuka-Shell 20 parts Epoxy K.K.) PKHH (supplied by Union Carbide 19 parts Corporation) Byron 200 (supplied by Toyobo K.K) 60 parts Phenolix resin B 1 parts Resin components of Paint H Sumilit- EX-13 (supplied by sumitomo 40 parts Kagaku K.K.) Hitanol 4020 (phenolic resin supplied 16 parts Hitachi Kasei K.K.) Vinylite VMCC (vinyl chloride/vinyl 40 parts acetate copolymer supplied by Union Carbide Corporation) Epikote 828 (supplied by Yuka-Shell 4 parts Epoxy K.K.) Resin components of Paint I Epikote 1007 (supplied by Yuka-Shell 50 parts Epoxy K.K.) Phenolix resin C 50 parts The coating paints and resin solution were dissolved in a mixed solvent (xylene/cyclohexanone/butylcellosolve =40/40/20) to form paints A through I having a resin concentration of 30%.

Example 1 The paint A was coated on the surface, to be formed onto the outer surface of the can, of a tinfree steel sheet having a blank thickness of 0.18 mm and a temper degree of DR-9 so that the coating thickness after drying was about 8 yum, and the coating was baked at 200 C for 10 minutes. Then, the uncoated surface (the surface to be formed into the inner surface) of this one-coated sheet was coated with the paint A so that the coating thickness after drying was about 20 jim, and the coating was baked at 200 C for 10 minutes to obtain a coated steel sheet. Palm oil was coated on the coated steel sheet, and the coated sheet was punched into a disk having a diameter of 187 mm and formed into a shallow-draw-formed cup between a drawing punch and a drawing die according to customary procedures.

The draw ratio at this drawing step was 1.5, and the thickness tw, of the side wall portion of the shallow-draw-formed cup was larger by about 20% than tB.

The redraw forming was carried out through first, second and third redrawing steps shown in Fig.2.

The draw ratios at the first, second and third redrawing steps were as follows.

Draw ratio at first redrawing step: 1.29 Draw ratio at second redrawing step: 1.24 Draw ratio at third redrawing step: 1.20 Other redrawing conditions were as follows.

Curvature radius (Rd) of operating corner of redrawing die: 0.41 mm Curvature radius (Rh) of holding corner portion: 1.0 mm Blank holder load: 6000 kg Dynamic friction coefficient (H): 0.09 The characteristics of the redrawn deep-draw-formed cup were as follows.

Cup diameter: 66 mm Cup height: 140 mm Thickness change ratio of side wall: -1870 tU/tL 1.3 Then, the deep-draw-formed cup was subjected to doming, trimming, neck-in processing and flanging according to customary procedures, degreased and washed to obtain a can barrel for a two-piece canned product.

The gel proportion of the inner face coating was measured according to the following procedures.

The outer surface organic coating of the barrel of the sample can was removed by decomposition by 95 concentrated sulfuric acid for 2 minutes and water washing, and the sample can was cut into a test piece having a size of 5 cm x 5 cm. The test piece was dried and the weight (W0) was measured. The test piece was subjected to extraction in MEK at the boiling point MEK for 60 minutes. The test piece was dried at 150 C for 20 minutes and the weight (W1) of the test piece was measured. Then, the inner face coating left as the extraction residue was decomposed and removed by concentrated sulfuric acid according to the abovementioned method, and the test piece was water-washed and dried and the weight (W2) of the test piece was measured.The gel proportion was determined by the following formula: 2 Gel proportion (,0) = -- x 100 WO - W2 The elongation and Young's modulus of the coating were measured in the following manner.

The paint A was coated on a clean tinplate so that the coating thickness after drying was 20 jim, and the coating was baked at 200 C for 10 minutes. Then, a free film obtained by the mercury amalgam method was cut into a tensile test sample having a width of 5 mm and a length of 30 mm. So-obtained five samples were subjected to the tensile test at a pulling speed of 50 mm/min in an atmosphere maintained at 100 C, and from the results of the analysis of the obtained stressstrain curve, the elongation and Young's modulus of the coating were determined as mean values of the five samples.

The chlorine content was determined in the following manner.

Determination of Chlorine A coated steel sheet sample was dipped in N/10 nitric acid solution to dissolve the substrate and obtain a coating. Then, precisely measured about 0.2 g of the coating was placed on about 2 g of potassium hydroxide spread on the bottom of a nickel crucible having a capacity of 60 ml, and the coating was sufficiently covered with about 5 of potassium hydroxide. Then, about 1 ml of ethyl alcohol was dropped into the crucible to wet the content sufficiently with ethyl alcohol. The crucible was strongly heated for 10 minutes, and after cooling, the crucible was placed in a beaker and 100 ml of water was added to dissolve the content of the hot crucible. The solution was filtered, and the washing liquid of the beaker, the filter paper and the crucible and the filtrate were placed in another beaker.The solution was made weakly acidic by nitric acid, and precisely measured 50 ml of N/10 silver nitrate solution was added to the solution and the mixture was stirred. The formed white precipitate was recovered by filtration, and the filtrate and the washing liquid of the breaker and the precipitate were charged in another breaker. Then, 5 ml of an ammonium ferric nitrate was added to the solution and titration was carried out with N/10 ammonium sulfocyanide until the liquid became reddish brown.The content of chlorine was calculated according to the following formula: N/10 silver nitrate solution (ml)) X F;Ag-N/10 ammonium sulfocyanide Chlorine solution (ml)) X FCN content = xO. 003546x100 (%) coating (g) wherein FAg stands for the factor of N/10 silver nitrate solution and FCN stands for the factor of N/10 ammonium sulfocyanide solution.

This determination method is described on page 1436 of "Handbook of Coating" published by Sangyo Tosho.

Cola was cold-filled in 100 of the above-mentioned redraw cans, and the cans were double-seamed and were stored at 37 C for 6 months. Then, the cans were opened, and the corrosion state of the inner surface of each can was observed. The obtained results are shown in Table 1.

Example 2 The procedures of Example 1 were repeated in the same manner except that the paint B was used instead of the paint A. The obtained results are shown in Table 1.

Example 3 The procedures of Example 1 were repeated In the same manner except that the paint C was used instead of the paint A. The obtained results are shown in Table 1.

Example 4 The procedures of Example 1 were repeated in the same manner except that the paint D was instead of the paint A. The obtained results are shown in Table 1.

Comparative Example 1 The procedures of Example 1 were repeated in the same manner except that the paint E was used instead of the paint A. The obtained results are shown in Table 1.

Comparative Example 2 The procedures of Example 1 were repeated in the same manner except that the paint F was used instead of the paint A. The obtained results are shown in Table 1.

Comparative Example 3 The procedures of Example 1 were repeated in the same manner except that the paint G was used instead of the paint A and the baking of the inner face coating and the coating of the tensile test sample was carried out at 2000C for 2 minutes. The obtained results are shown in Table 1.

Comparative Example 4 The procedures of Example 1 were repeated in the same manner except that the paint H was used instead of the paint A. The obtained results are shown in Table 1.

Comparative Example 5 The procedures of Example 1 were repeated in the same manner except that the paint I was used instead of the paint A. The obtained results are shown in Table 1. Table 1 Paint Gel Elonga- Young's Chlo- Evaluation of Deep-Drawn Cup Proport- tion (%) Modulus rine ion (%) (dyne/cm) Cont- Storage Test (6months) ent (%) Formability State or inner Number of leak face cans (total= 100 cans) Example 1 A 70 232 7.6 x 108 0 good no change 0 Example 2 B 52 380 5.3 x 107 0 good no change 0 Example 3 C 65 653 3.3 x 106 0 good no change 0 Example 4 D 53 502 6.1 x 108 17 good no change 0 Comparative Example 1 E 92 13 1.5 x 1010 0 bad (breaking conspicuous 99 of coating) corrosion at broken part of coating Comparative Example 2 F 38 68 3.9 x 109 0 bad (shock conspicuous 32 line) corrosion at shock line Comparative Example 3 G 8 251 2.6 x 105 0 bad (insuffi- blister 0 cient draft) Comparative Example 4 H 74 455 2.3 x 107 42 good blister, filament- 0 ary rust Comparative Example 5 I 88 74 2.9 x 1010 0 bad (roughness conspicuous 91 of coating, corrosion shock line)

Claims

1. A thin-walled deep-draw-formed coated can prepared by deep-draw-forming a precoated sheet and having a reduced thickness in the side wall portion, wherein the coating of the precoated metal sheet is composed of a plasticizer-containing or internally plasticized thermosetting resin having a gel proportion of 30 to 90% as measured in methylethylketone at the boiling point thereof, an elongation of at least 200% as 6 measured at 100 C, a Young's modulus of 1 x 10 to 5 x 109 dyne/cm2 as measured at 100 C and a chlorine content lower than 20% by weight in the resin.

2. A thin-walled deep-draw-formed coated can as set forth in claim 1, wherein the entire draw ratio is in the range of from 1.3 to 4 and the thickness of the side wall portion is 5 to 40% of the blank thickness on the average.

3. A thin-walled deep-draw-formed coated can as set forth in claim 1, wherein the thermosetting resin coating comprises (i) a coating-forming component selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin, (ii) a coating-forming component other than the coating-forming component (i), which shows a curing action to the coating-forming component (i) and is selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin, and (iii) a plasticizer.

4. A thin-walled deep-draw-formed coated can as set forth in claim 1, wherein the thermosetting resin coating comprises (i) a coating-forming component selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin and (ii) a coating-forming component other than the coatingforming component (i), which shows a curing action to the coating-forming component (i) and is selected from the group consisting of an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin, an epoxy resin, a phenolic resin and an amino resin, and a resin component which is internally plasticized by a long-chain alkyl group present in the molecule is used as at least one of the coating-forming components (i) and (ii).

5. A thin-walled deep-draw-formed coated can as set forth in claim 4, wherein the long-chain alkyl group has 6 to 36 carbon atoms and the long-chain alkyl group is contained in an amount of 1 to 50% by weight based on the resin.

6. A thin-walled deep-draw-formed coated can as set forth in claim 1, wherein the thermosetting resin coating comprises (A) an epoxy resin derived from as epihalohydrin and bisphenol A, (B) a resol type phenolic resin which is derived from phenols including an alkyl phenol having an alkyl group having 6 to 26 carbon atoms and formaldehyde and contains said alkyl group in an amount of 1 to 50% by weight based on the resin, and (C) a phenoxy resin.

7. A thin-walled deep-draw-formed coated can as set forth in claim 6, wherein the components (A), (B) and (C) are present in amounts of 30 to 99 by weight, 1 to 45S by weight and 0 to 50% by weight, respectively.

8. A thin-walled deep-draw-formed coated can as set forth in claim 1, wherein the thermosetting resin coating comprises (A) an epoxy resin derived from an epihalohydrin and bisphenol A, (B) a resol type phenolic resin which is derived from phenols including an alkyl phenol having an alkyl group having 6 to 26 carbon atoms and formaldehyde and contains said alkyl group in an amount 1 to 50% by weight based on the resin, and (C) a vinyl chloride resin.

9. A thin-walled deep-draw-formed coated can as set forth in claim 8, wherein the components (A), (B) and (C) are present in amounts of 30 to 99 by weight, 1 to 45% by weight and 0 to 35% by weight, respectively.

10. A thin-walled deep-draw-formed coated can as set forth in claim 1, wherein the thermosetting resin coating is formed from a composition comprising (A) an epoxy resin derived from an epihalohydrin and bisphenol A, (B) a resol type phenolic resin, (C) a phenoxy resin and (D) a polyester type plasticizer.

11. A thin-walled deep-draw-formed coated can as set forth in claim 10, wherein the components (A), (B), (C) and (D) are present in amounts of 30 to 99% by weight, 1 to 45% by weight, 0 to 50% by weight and 5 to 40% by weight, respectively.

12. A process for the preparation of a thin-walled deep-draw-formed coated can, which comprises preparing a predraw cup from a precoated metal sheet, holding the predraw cup by an annular holding member inserted in the cup and a redrawing die, and relatively moving redrawing punch, which is arranged coaxially with the holding member and redrawing die so that the redrawing punch can enter into the holding member and come out therefrom, and the redrawing die so that the redrawing punch and redrawing die engage with each other, to form the predrawn cup into a deep-drawn cup having a diameter smaller than the diameter of the predrawn cup, wherein a metal sheet having a coating composed of a plasticizercontaining or internally plasticized thermosetting resin having a gel proportion of 30 to 90% as measured in methylethylketone at the boiling point thereof, an elongation of at least 200% as measured at 1000 C, a Young's modulus of 1 x 106 to 5 x 109 dyne/cm2 as measured at 100 C and a chlorine content lower than 20% by weight in the resin is used as the precoated metal sheet, and the predraw cup is formed into the deep-drawn cup while bend-elongating the predrawn cup through the redrawing die at a temperature higher than the glass transition temperature of the thermosetting resin coating.

13. A can substantially as described herein with reference to the figures.

14. A process for preparing a can substantially as described herein with reference to the figures.