Cemented lap seam container

Abstract

Can body blanks to be used in production of cemented lap side seam containers are pre-coated with a pigmented epoxy-type coating which, when the body blank is lap side seamed, functions to provide a bonding interface for the lap side seam adhesive while simultaneously functioning as an adherent base upon which to apply printing or other decoration for the exterior surface of the can body thereby permitting elimination of heretofore necessary binding lines and size coat.

Description

BACKGROUND OF THE INVENTION

Cemented, as opposed to soldered, side seam bodies are known in the art. Cans produced from such bodies have found a substantial degree of commercial success for the packaging of products which generate no substantial internal pressure, such as frozen citrus concentrate, household cleaners and polishers, and the like. One of the major selling features of such can bodies is that it is possible to provide printed decorations, as opposed to paper labels, completely around the external surface of a can body. However, such prior art cemented side seam bodies do not have a high degree of bursting strength, particularly when the can is subjected to conditions necessary to process certain products such as the sterilization cooking for fruits and vegetables, or pasturization of beer.

The very high strength adhesives known to the art have not been heretofore successfully used in the manufacture of cemented side seam can bodies for any one of a number of reasons. Some of the major reasons are that although these adhesives have excellent cohesive strength they have been woefully deficient in their adhesion to a metal surface or even to a coating supplied to sheet metal for making can bodies. Another drawback is that these high strength adhesives require a relatively prolonged setting time in the order of minutes or even hours, which time periods are completely unsuitable for high speed can making operations where sufficient bonding strength to hold the can bodies together must be achieved within seconds or less.

Recently, can bodies and methods therefor have been provided which overcome the disadvantages discussed above. Such a procedure, for example, is disclosed in copending application Ser. No. 202,096 filed Nov. 26, 1971 in the names of K. R. Rentmeester and E. W. Kaiser now U.S. Pat. No. 3,773,589 issued Nov. 20, 1973, wherein tubular sheet metal can bodies having opposed longitudinal edges overlapped to form a lap side seam are provided wherein the opposed surfaces of the sheet metal include within the lap side seam an organic coating containing epoxide resin and high-strength organic adhesive disposed within the lap side seam and adhered to the organic coating. As described in said copending application, the coating extends over the entire flat surfaces of the sheet metal and as a result thereof over the entire inside and outside surface of the can body. The coating employed in said copending application also provides an adherent base upon which to apply printing or other decoration for the outside surface of the can body and the decoration is most conveniently applied in the flat, i.e., to that surface of the blank which will later form the outside surface of the can body. Heretofore, the decorative coating has not been permitted to extend into the margin to which the adhesive is to be applied so as to assure that the adhesive would be bonded directly to the coating. Thus, in the procedure of said copending application, as well as in other procedures which do not have the attendant advantages of the procedure of said copending application, it has generally been the procedure in applying decorative coatings to first apply a primer or size coat to protect the metal surface and to provide a bonding interface for the adhesive. A further top coat which may be pigmented, printed or otherwise decorated is then applied but such decorated top coat has not been permitted to extend into the lap seam. This has been a necessary practice since pigmented or painted surfaces have not been readily bondable. The application of a first "size" or "primer" coat followed by application of a pigmented or decorative coat which is applied to only a portion of a can body blank leads to expense and difficulty. Aside from the care and equipment needed to produce the blank, the top coated or decorated blank contains an unpigmented or undecorated area usually seen as a ragged edge which detracts from the overall aesthetic effect. This area is usually hidden by binding lines. This is an added and expensive operation and detracts from all around lithography and decoration; there is therefore within the can making industry a considerable need for a container, produced by a cemented lap side seam process, which retains the advantages of containers produced by such a process, from a can body blank to which a protective and decorative coating has been applied to the entire exterior surface, which eliminates the need to apply a first size coat followed by a decorative coat followed by application of binding lines.

It is therefore an object of the present invention to provide a lap side seam can body having applied to the exterior surface thereof a pigmented coating which functions to provide a bonding interface for the lap side seam adhesive while simultaneously functioning as a adherent base upon which to apply printing or other decoration to the entire surface.

Another object of the present invention is to provide a lap side seam can body having applied thereto such an exterior pigmented coating and having exceptionally high bursting or hoop strength.

Another object is to provide a lap side seam can body having applied thereto such an exterior pigmented coating and which maintains its high bursting or hoop strength even after it is subjected to prolonged conditions of moist heat.

Yet another object is to provide a decorated lap side seam can body which can be made rapidly on high speed automatic equipment.

A further object is to provide a method for production of a lap side seam can body which eliminates the necessity of applying a first size or prime coat, a decorative top coat and binding lines as in the prior art.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description which, taken in connection with the accompanying drawings, discloses the preferred embodiment thereof.

SUMMARY OF THE INVENTION

The above objects are accomplished by providing a tubular sheet metal, lap side seam can body having as a decorative coating on its entire exterior surface, a baked organic coating containing a pigmented cured epoxide. Preferably, this coating is the heat-cured reaction product formed by applying and baking a coating composition comprising an epoxy resin and a pigment, for example, an epoxy ester and titanium dioxide, the pigment to non-volatile vehicle ratio preferably being about 40-65 parts pigment per 60-35 parts non-volatile vehicle, the opposed coated surfaces being bonded together with a linear superpolyamide adhesive. This can body is formed from a flat blank having at least one entire surface coated in the manner described and having the adhesive applied, before bonding of the lap side seam, to the coating on at least one of the longitudinal margins thereof. The method and apparatus for making the can body blank is described in U.S. Pat. No. 3,481,809 in the names of Edward William Kaiser, Arnold Robert Rein and Richard Otto Rahler.

Other methods and apparatus for forming the tubular can body and lap side seam as well as for applying the adhesive may be as disclosed in U.S. Pat. No. 3,508,507 issued to A. T. L. Austing and copending U.S. applications Ser. No. 75,530 filed Sept. 25, 1970 in the name of K. R. Rentmeester, now U.S. Pat. No. 3,760,750 issued Sept. 25, 1973 and Ser. No. 79,243 filed Oct. 8, 1970 in the names of K. R. Rentmeester and P. H. Winterroth, now abandoned.

In carrying out the method in accordance with the present invention, the steps of forming the blank into tubular shape, applying the superpolyamide to the longitudinal margin areas, heating the adhesive, and pressing the opposed lap seam surfaces together between chilled supporting surfaces are effected automatically, less than about one second being required for heating the adhesive and pressing the lap seamed surfaces to form the bonded seam.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings:

FIG. 1 is a perspective view of a can body blank of the instant invention.

FIG. 2 is a perspective view of a can body of the instant invention;

FIG. 3 is a fragmentary enlarged sectional view taken along line 3--3 of FIG. 2;

and FIG. 4 is a fragmentary enlarged sectional view of a can body of the prior art taken substantially along line 3--3 of FIG. 2.

As the preferred or exemplified embodiment of this invention, FIG. 1 shows a substantially rectangular can body blank generally designated 10 having for the metal component thereof thin guage sheet metal 11 in the order of magnitude of ten thousandths of an inch. This sheet metal, which may be thicker or thinner than the numerical number given, may be aluminum or low carbon steel, with or without an external plating of aluminum, chromium, cobalt, nickel or tin. Completely covering the exposed, extensive exterior flat surface 14 is a particular pigmented and decorative organic coating composition 13 which will be defined more thoroughly hereinafter. Covering the extensive interior flat surface 12 is an organic coating 19 which will be defined more thoroughly hereinafter. Tenaciously adhered to a coating 19 along the inside surface of one longitudinal surface 16 of the blank 10 is an organic cement or adhesive 18, which will also be defined more fully hereinafter. The adhesive 18 extends the full length of the margin 16 and inwardly from the edge of this margin, i.e., has a width of from three thirty-seconds inch to nine thirty-seconds inch and preferably 0.200 inch, and upwardly from the coated surfaces of the margin, i.e., has a thickness of from 0.003 inch to 0.006 inch and preferably about 0.004 inch.

The blank 10 is formed into an open ended tubular can body generally designated 20 (FIG. 2), on a high speed automatic, can body maker, for example of the type utilizing the body-blank applicator of the aforementioned U.S. Pat. No. 3,481,809, by lapping the blank 10 around a mandrel, heating the adhesive 18 to a semi-fluid, tacky condition and pressing onto the coated upper surface or the opposite blank margin 17. Immediately thereafter the bonded side seam is chilled to set the adhesive and to secure the lapped margins together to form the can body 20 having a lapped side seam generally designated 22, including an inner lap 24 (from the margin 16) and an outer lap 26 (from the margin 17). Bonding of the lapped margins is accomplished in less than one second and preferably in about 10 milliseconds. A container bodymaker which performs this function is described in U.S. Pat. No. 3,508,507 issued to A. T. L. Austing.

As best shown in FIG. 3, the adhesive 18 does not bond directly to the sheet metal 11 of the can body but rather to the opposed surfaces of the exterior organic pigmented epoxy coating 13 and interior coating 19 included within the side seam 22. In other words, the high strength bond of the lap side seam 22 is a result of the tenacious adherence of the coatings 13 and 19 to the sheet metal 11 and to the organic adhesive 18 interposed between the coated faces of the margins 16 and 17.

As stated previously, the coating 13 extends over the entire flat exterior surface 14 of the sheet metal 11 and as a result therof over the entire outside or exterior surface of can body 20. The coating 13 provides an adherent base upon which to apply printing or other decoration to the surface of the can body as well as a protective coating for the metal over its exposed surface. Decoration (not shown) is more conveniently applied in the flat, i.e., to that surface of the blank 10 or of a larger sheet from which the blank is cut which will later form the outside surface of the can body. As best illustrated in FIG. 3, the decorative coating extends into the bonding area to which the adhesive 18 is subsequently adhered. An appreciation of the present container over the prior art containers may be seen in FIG. 4 wherein a protective coating 25 was first applied over which a decorative top coat 23 was applied. The decorative top coat in FIG. 4 does not extend into the margin 26 to which the adhesive 28 is adhered, since adhesion is effected via bonding of the adhesive to the unpigmented size coating 25.

The coating 13 of this invention, mentioned hereinabove, comprises a pigmented epoxide resin having, before curing, an epoxide equivalent of from 425 to 6,000 and a number average molecular weight of from 1,000 to 4,000 and components coreactive therewith upon application of heat to form an epoxy resin which is preferably an epoxy-ester, epoxy-amino or epoxy-phenolic resin, and such classes of resins modified with various additives such as melamine, urea formaldehyde resins and mixtures thereof.

Any epoxy resin which, when pigmented as in the instant invention, forms a suitable bonding interface and base for receiving decorations may be employed. Epoxy-ester resins, generally derived by reaction of an epoxy-ether having an average molecular weight of about 1,000 to 2,000, and having an epoxide equivalent weight of about 875 to 1,025 with a fatty acid, as for example, saturated and unsaturated fatty acids derived from linseed oil, soya, dehydrated castor oil, tall oil, etc., or simple fatty acids such as oleic, lauric, stearic, palmitic, myristic, linoleic, sorbic, etc. and mixtures thereof may be employed and are especially preferred herein. Epoxy-ester resins are generally obtained by esterifying an epoxy-ether with said acids in relative proportions of about 1 equivalent epoxy to about 0.3 to 0.9 equivalent of fatty acid.

Other suitable epoxy resins are epoxy-amino resins, derived by reaction of epoxy-ethers having an average molecular weight, before curing, of about 900 to about 4,000 with various amino-containing resins such as melamine, triazine, ureaformaldehyde, etc. Such epoxy amino resins are generally obtained via reaction of epoxy ethers, for example, diglycidyl ether of bis-phenol A with such amino-containing resins in relative proportions varying from about 95/5 to 50/50. Other suitable epoxy resins include epoxy-phenolic resins which include reaction products of various polyhydricphenols for example, allyl ether of polymethylol phenol, polymethylol tertiary butyl phenol, polymethylol p-phenylphenol, etc., with epichlorohydrin and similar epoxidic materials by methods known in the art. Suitable epoxides of this class will have, before curing, an epoxide equivalent of about 425 to 6,000 and an average molecular weight of about 1,000 to 4,000 and include polyglycidyl ethers of bisphenol A, epoxidized novolacs, etc.

Thus, the epoxy-ester, epoxy-amino and epoxy-phenolic resins suitable for use in the invention are well known in the art and may be prepared by incorporation of the reacting components in the formulation including catalysts and modifying agents as desired. Particularly preferred are such resins modified through further reaction with melamine, ureaformaldehyde resins and combinations thereof. The epoxy resins, as employed herein, are pigmented with proportions of pigment to non-volatile vehicle being generally within the range of about 40 to 65, preferably 50 to 60, parts by weight of pigment to 60 to 35, preferably 50-40, parts of non-volatile vehicle. Exemplary of suitable pigments are titanium dioxide, colloidal silica, zinc oxide, and aluminum pastes or powders. Both rutile and anatase forms of titanium dioxide are preferred for use herein with rutile titanium dioxide being especially preferred.

Extender pigments may be employed where desired. In general, however, such ingredients are not employed particularly in formulating white coatings which are applied as relatively thin films and any substantial use of extenders would tend to detract from the desired coverage and aesthetic quality of the coating. Where it is desired to employ such extenders, however, conventional extender pigments known in the art, for example, calcium carbonate; may prove suitable. Various other additives such as flow control agents, suspending aids, and compatible lubricants may be employed as desired. The coating 13 is preferably applied as a dispersion of the above described ingredients, before their inter-reaction, in a fugitive liquid. It is necessary that the liquid be volatile at baking temperatures which may be as low as 300.degree.F. or as high as 650.degree.F. At the lower temperature, a baking period of about 10 minutes may be required and at the upper temperature a time of five seconds may suffice. The solvent must also be compatible with all the ingredients in their useful concentrations, so that precipitation, stratification or other separation does not occur. Suitable solvents comprise aryl or aralkyl hydrocarbons blended with alcohols, ketones, ethers or esters and mixtures thereof. Alcohol, ketones, ethers or esters or mixtures thereof may be employed without aryl or aralkyl hydrocarbons if desired. Solvent systems comprising a mixture of aryl or aralkyl hydrocarbons and alcohols yield solutions having optimum viscosity for application and for this reason are preferred.

Examples of the aromatic hydrocarbons solvents are xylene, toluene, and petroleum fractions having a high proportion of aromatic hydrocarbons and having a boiling range of about 230.degree.F. to 415.degree.F. Examples of suitable oxygen containing solvents are butanol, diacetone alcohol, isophorone, methylisobutylketone, nitropropane, ethylene glycol monobutyl ether, tetrahydrofuran, cyclohexanone, amyl acetate, ethylene glycol monomethyl ether acetate, diisobutyl ketone and cyclohexanone.

In the specific example which follows, the first three ingredients were dissolved in the remaining solvent components and uniformly applied to one large flat surface of sheet aluminum. The thus coated sheet was passed into an oven and baked under the conditions of temperature and time above discussed and thereafter cooled. Subsequently, the coating is printed as desired and preferably varnished over the printed label to provide the decorative coating 13.

After application of the fluid coating composition described immediately below and during the baking of the thus coated sheet described hereinafter, the non-volatile ingredients are inter-reacted and the volatile organic liquid is driven off so that upon completion of the baking operation and subsequent cooling, the solid inert adherent coating 13 remains on the metal sheet 11. A specific example of a fluid composition for application to the metal sheet 11 to provide the finished coating is as follows:

PARTS BY MATERIAL WEIGHT ______________________________________ Epoxy Resin (A glycidyl ether of bis Phenol A 19.0 having an average M.W. of about 2900) Urea-Formaldehyde Resin (Rohm & Haas 3300) 12.3 (50% total solids) Titanium Dioxide Pigment (Dupont R110) 19.7 Diacetone Alcohol 14.7 Diisobutyl Ketone 4.9 Isophorone 4.9 Xylene 17.1 n-Butanol 7.4 100.0 ______________________________________

In addition to the above described exterior coating, epoxy based coatings may be employed to form interior coatings 19 for the interior surfaces 12 of the container body. Such coatings may be unpigmented or pigmented epoxy resins as described above, or may include any of well known coatings employed for this purpose. One such other coating which may be employed is an epoxy-urea-formaldehyde coating wherein the epoxy component is a 1, 2-epoxide resin substantially similar to the epoxy-ethers hereinbefore described. Historically, it has been preferred that the inside coat for beverage containers be of some color. This preference has more significance in lap seam cemented cans because a coating must also be applied to the exterior surface in order to do the cementing job. Such a colored inside coating is desirable since it is often desired to have a difference in color between the inside and the outside of a container body, so that the printing press man can immediately determine if he is printing on the correct side of the sheet. For this reason it is preferred that the can body blank be coated on the surface that is to form the interior of a container body with an epoxy resin having a pigment different from that applied to the exterior surfaces, for example, a gold tartrazine lake pigment.

Additionally, the decorative, pigmented epoxy exterior coating may, if desired, be coated with a further clear varnish for protection of the decorative label once it has been applied. Such varnishes may be conventional lacquers such as alkyds, acrylics, etc. It will be understood, however, that such additional coating is not mandatory nor is it limited to the specific examples above enumerated and may include any of conventional coatings known in the art.

The linear superpolyamide adhesives useful in the instant invention are generally characterized by having recurring aliphatic amido groups separated by alkylene groups having at least two carbon atoms and having an inherent viscosity of at least 0.4. These superpolyamides are disclosed in U.S. Pat. Nos. 3,256,304; 2,962,468; 3,397,816; 3,447,999; 3,249,629, etc.

As employed herein, inherent viscosity .eta.inh is defined by the following equation: ##EQU1## wherein ln.eta.rel represents the natural logarithm of the relative viscosity and ##EQU2## .eta. being viscosity and C the concentration of the solute in grams per 100 cc. of solution. The inherent viscosity values employed herein are obtained with the polyamide involved dissolved in m-cresol at a concentration of 0.5 g. of polymer per 100 cc. of solution at 25.degree. C.

Among the superpolyamides which are useful in the present invention and having inherent viscosities as described above are polypentamethylene sebacamide, polyhexamethylene adipamide, polyhexamethylene sebacamide, poly-m-phenylene sebacamide, 6-amino-caproic acid polymers, 7-amino-heptanoic acid polymers, 11-amino undecanoic acid polymers, and 12-amino-stearic acid polymers; polyamides derived from reaction of polymeric fat acids with various amines for example polyamides derived from polymerized tall oil, 10-undecynoic, soybean, dehydrated castor oil, cottonseed, linoleic, etc., acids and organic diamines, triamines, tetramines, etc., as described in the above-identified patents, the disclosures thereof being incorporated herein by the aforegoing references thereto.

It is thought that the new invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the matter of ingredients, the identity and the proportions of formulation, and that changes may be made in the form, construction and arrangement of the parts of the article without departing from the spirit and scope of the invention of sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

Claims

I claim:

1. A decorated, tubular, sheet metal can body having opposed longitudinal edges overlapped to form a lap side seam wherein the interior metal surface within the seam is adjacent to and overlaps the opposed exterior metal surface within the seam, the opposed surfaces included within said lap seam having adhered thereto an organic coating comprising an epoxy resin, and an organic adhesive disposed in said lap seam and adhered to the coating on said surfaces, said organic adhesive being a linear superpolyamide having an inherent viscosity of at least 0.4;

the coating on the entire exterior surface being a cured, decorative pigmented organic coating which extends into the lap seam, constitutes a bonding interface for the organic adhesive and an adherent base receptive to printing or other decoration, said cured coating being derived from a composition comprising from about 40 to about 65 parts by weight of a pigment and from about 60 to about 35 parts by weight of non-volatile vehicle comprising an epoxy ether having, before curing, an epoxide equivalent of from 425 to 6,000 and a number average molecular weight of from 1,000 to 4,000 and components coreactive therewith upon application of heat to form an epoxy resin, the epoxy resin thus formed being selected from the group consisting of (1) epoxy-phenolic (2) epoxy-ester and (3) epoxy-amino resins.

2. A decorated, tubular, sheet metal can body as defined in claim 1 in which said coating on the exterior surface comprises an epoxy-ester resin derived from the reaction of a diglycidyl ether of bisphenol A and oleic acid.

3. A decorated, tubular, sheet metal can body as defined in claim 1 in which said coating on the exterior surface comprises an epoxy-amino resin derived from the reaction of a diglycidyl ether of bisphenol A and a ureaformaldehyde resin.

4. A decorated, tubular, sheet metal can body as defined in claim 1 in which said coating on the exterior surface comprises an epoxy-phenolic resin derived from the reaction of a diglycidyl ether of bisphenol A and a polyhydric phenol.

5. A decorated tubular sheet metal can body as defined in claim 1 in which said pigment is titanium dioxide.

6. A decorated, tubular, sheet metal can body as defined in claim 1 in which said coating on the exterior surface comprises an epoxy-ester resin derived from reaction of a diglycidyl ether of bisphenol A having an average molecular weight of about 1400 and oleic acid, said adhesive is a linear superpolyamide having recurring aliphatic amido groups separated by alkylene groups having at least two carbon atoms and said pigment is titanium dioxide.

7. A decorated, tubular sheet metal can body as defined in claim 1 in which the pigmented coating on the exterior surface is printed.

8. A method of fabricating a decorated, tubular, metal can body having its opposed longitudinal edges overlapped to form a lap side seam comprising:

applying to the entire exterior surface of the sheet metal to be formed into a can body, a decorative pigmented organic coating formulation comprising, as the non-volatile vehicle, about 60 to about 35 parts by weight of an epoxide having before curing, an epoxide equivalent of from 425 to 6,000 and a number average molecular weight of from 1,000 to 4,000 and components coreactive therewith upon application of heat to form an epoxy resin, the epoxy resin thus formed being selected from the group consisting of (1) epoxy-phenolic (2) epoxy-ester and (3) epoxy-amino resins, and about 40 to about 65 parts by weight of a pigment, said pigmented coating constituting a bonding interface for a lap side seam adhesive and an adherent base receptive to printing or other decoration;

baking the coated sheet metal at a temperature of at least 300.degree.F, to cure the organic coating thereon;

forming said coated sheet metal into a tubular can body, arranged to have a lap side seam wherein the interior metal surface within the finished seam is adjacent to and overlaps the opposed exterior metal surface within the seam, there being applied to at least one of said opposed surfaces forming the seam an organic adhesive comprising a linear superpolyamide having an inherent viscosity of at least 0.4;

and bonding said opposed surfaces to form the finished seam, said decorative pigmented coating extending into the lap seam thus produced.

9. A method as claimed in claim 1 wherein said cured epoxide is an epoxy-ester resin.

10. The method of claim 9 wherein said pigment is titanium dioxide and said epoxy ester resin is the reaction product of an epoxy-ether and a fatty acid.

11. The method of claim 10 wherein said fatty acid is oleic acid.

12. The method of claim 11 wherein said formulation consists of 50 - 60 parts titanium dioxide to 50 - 40 parts non-volatile vehicle.

13. A method as claimed in claim 1 wherein said cured epoxide is an epoxy-amino resin.

14. A method as claimed in claim 1 wherein said cured epoxide is an epoxy phenolic resin.

15. A method as claimed in claim 1 wherein said coating contains a urea-formaldehyde resin.

16. A method as claimed in claim 1 wherein said organic adhesive applied within the seam is a linear superpolyamide having recurring aliphatic amido groups separated by alkylene groups having at least two carbon atoms.

17. A method as claimed in claim 1 wherein said steps of applying said organic adhesive, forming said tubular shape, and bonding are carried out automatically, said step of bonding the opposed surfaces being effected in less than about 1 second.

18. A method as claimed in claim 1 wherein the surface of the sheet metal which is to form the interior surface of the can body is coated with a 1, 2-epoxide resin.

19. A method as claimed in claim 1 wherein said pigment is titanium dioxide.

20. A method as claimed in claim 1 wherein said coated sheet is printed prior to forming into said tubular can body.

21. A method of fabricating a decorated, tubular, sheet metal can body having its opposed longitudinal edges overlapped to form a lap side seam, comprising:

applying to the interior surface of the sheet metal to be formed into a can body an organic coating comprising a 1,2-epoxide resin having before curing an epoxide equivalent of from about 425 to 6,000 and a number average molecular weight of from 1,000 to 4,000;

applying to the exterior surface of the sheet metal to be formed into a can body a decorative pigmented organic coating formulation comprising, as the non-volatile vehicle, 60-35 parts by weight of an epoxide having before curing an epoxide equivalent of from 425 to 6,000 and a number average molecular weight of from 1,000 to 4,000 and components co-reactive therewith upon application of heat to form an epoxy resin, the epoxy resin thus formed being selected from the group consisting of (1) epoxy-phenolic, (2) epoxy-ester and (3) epoxy-amino resins, and 40-65 parts by weight titanium dioxide pigment, said pigmented coating constituting a bonding interface for a lap side seam adhesive and an adherent base receptive to printing or other decoration;

baking the coated sheet metal at a temperature of at least 300.degree.F to cure the organic coatings thereon;

forming said coated sheet metal into a tubular can body, arranged to have a lap side seam wherein the coated interior metal surface within the finished seam is adjacent to and overlaps the similarly coated opposed exterior surface within the seam, there being applied to at least one of said opposed coated surfaces forming the seam an organic adhesive comprising a linear superpolyamide having an inherent viscosity of at least 0.4;

and bonding said opposed surfaces to form the finished seam by heating said organic adhesive to a tacky condition and then pressing said opposed surfaces between chilled supporting surfaces, said pigmented coating extending within the lap seam and said steps of applying said organic adhesive, forming said tubular shape, and bonding by heating and pressing together said opposed surfaces being carried out automatically.

22. The method of claim 14 wherein said cured coating on the exterior surface comprises an epoxy-ester resin derived from the reaction of a diglycidyl ether of bisphenol A having an average molecular weight of about 1000-2000 and epoxide equivalent of about 875-1025 and oleic acid.

23. The method of claim 14 wherein said cured coating on the exterior surface of the sheet metal comprises an epoxy-amino resin derived from the reaction of a diglycidyl ether of bisphenol A having an average molecular weight of about 1000-4000 and an epoxide equivalent of about 425-6000 and a urea-formaldehyde resin.

24. The method of claim 14 wherein the coating formulation applied to the exterior surface of the sheet metal comprises 50 to 40 parts of vehicle containing a diglycidyl ether of bisphenol A having an average molecular weight of about 1400 and oleic acid and 50-60 parts of titanium dioxide pigment.

25. A method as claimed in claim 21 wherein said coated sheet is printed prior to forming into said tubular can body.