US2138419A - Container closure and facing material therefor - Google Patents

Description

Nov. 29, 1938. v F. J. GAvlN 2,138,419

CONTAINER CLOSURE AND FACING MATERIAL THEREFOR Filed July l2, 1955 Patented Nov. 29, 1938 PATENT OFFICE CONTAINER CLOSUBE AND FACING MATERIAL THEREFOR Frank Joseph Gavin, Baltimore, Md., assignorto Crown Cork & Seal Company, Inc., Baltimore, Md., a corporation of New York application July 12, 193s. serai No. 31,113'

IClaim.

The present invention contemplates facing material for closure caps constituted by a sheet of aluminum foil having predeveloped overall surface iilms of its own oxide with a layer of a thermoplastic adhesive applied to one of the surfaces of the foil. It relates also to container closures having sealing faces of the oxidized foil.

In the packaging of many products in sealed containers, greatcare'must be taken to insure, as far as possible, that over a period of time the internal pressure, whether positive or negative, will be substantially maintained. To this end the closures of such containers have heretofore been provided on their undersides with sealing facings of an impermeable nature, such facings ordinarily being applied to a cushion liner and being either coextensive with the latter or of lesser diameter, the facings in the latter instances being known as spots.

While many materials have been proposed for such facings, metal foils, such as tin, aluminum, and so forth are naturally suited from a physical standpoint due to their impermeability, but are frequently objectionable due to their lack of resistance to chemical action. So far as its physical characteristics are concerned, aluminum foil makes an ideal facing material and is preferable to tin foil in view of its relative cheapness.'

aeFrom a chemical standpoint, however, plain aluminum foil is unsuited for many purposes due to its lack of acid and alkali resistance. To overcome this objection, the plain foil has been provided on its face with a re sisi-,ant coating ci er, this adding, however, materially to the cost and not being an absolute protection since upon age tothe lacquer the foil is exposed to ible destructive action.

ly have found that a facing material of wide use is afforded by oxidized aluminum foil, that is, an alum foil having ace films of its own oxide. Extensive tests ed out with a variety of products, auch as carbonated water and erale, have chown 'such icil to have e,l

s remarkable resistance to deterioration.

-Incarryingoutthetestslhavemadeuseoi oxidized aluminum foil produced both by the anodic procl and by the p 'ai ci passing the so bonate'and potassium dichromate. The former method results in a product whose color is metallic white, while in the latter case the color is -darkish i: f and on this ff--::' not so de- 'sirable as the iirst. e anodic foil is produced the x-r i1 ioil anode in the h a not solution of sodium can.A

(Cl. 21S-39) electrolysis of a suitable electrolyte, which may be an aqueous solution containing sulphuric acid or chromic acid.

The anodic foil is resistant to acids that corrode aluminum foil and in alkali resistance is 5 superior to the oxidized foil produced by the other method. While not so strong or ductile as the plain foil, its capacity in these respects is quite suicient to enable its successful use as closure facings. oxidized aluminum foils of both 1 types take coatings extremely well, the adherence of thermoplastic coatings being greatly superior as contrasted to the plain foil.

' The anodic foil is sensitive to discoloration and for this reason may desirably be dipped in a 15 dye solution to give it a color which will not be visibly marked in handling. Both types of the oxidized foil may be subjected to a coloring treatment, in the one instance principally for the purpose of providing a non-discolorable surface, 20 I and in the other instance for the principal 1" purpose' of imparting a color more pleasing than its natural darkish gray.

The oxidized foils may be coated with a rev sistant varnish such as vinyl lacquer and in this 25 case a double safeguard, as over the plain foil. is provided against deterioration. At the same time, the varnish may be given the desired color so as to have a double function.

Ordinarily in stamping metal foils a lubricant ao must be provided to prevent tearing by the punches. The oxide illms of the oxidized aluminum foils serve facilitate punching without the use of an ext ecus lubricant so that the danger ci discoloration fromuse of such latter is 35 avoided. V v

In the accom w r. drawing I have shown the facing steriel and closures,

Figure l being a bottom plan view of a crown cap provided with a spot of oxidized aluminum; 40

Figure 2 a dlametric section of the cap of Figure i;

Figure 3 a sheet or strip of the facing material, and

4 a view sar to Figure 2 with the 48 spot provid th a protective coating.

In Fie 3, reference numeral i0 designates a sheet or strip of exi aluminum foil prepared in any suitable manner, for example by one of the p #1v-ii.- above described, the treated so roll having overall predeveloped surface films of its own oxide. Applied to one face ci the foil is n layer ii ci nso-plastic adhesivewhich may be the gatta percha or the cellule derivative er ive dribed in Fai/ent No. lo

1,956,481, issued April 24, 1934, to Albin E. Warth. Any other suitable thermoplastic adhesive may, of course, be used. The adhesive is applied to the foil by any suitable method and bonds tenaciously therewith. In Figure 3 the foil and adhesive layer are shown as separated at one end of the strip. this being merely for the purpose of illustration. When properly applied, separation of the foil and adhesive layer is impossible. The described facing material may be packaged in stacks or in rolls, depending on the fmanner in which it is to be fed to the punches.

Il. 1It will be understood that the facing mate' rial may cover the cork cushion entirely if desired instead of being merely a spot as shown. Furthermore, the cushion layer may be of any suitable material other than cork and in some instances might be omitted altogether. So far as the combination of a sealing facing of oxidizedaluminum foil with a container closure is concerned, an adhesive other than a thermoplastic may be used.

In Figure 4 reference numeral I5 designates the metal shell of a crown cap, reference numeral i6 the cushion liner, reference numeral I1 an adhesive layer, reference numeral i8 a. spot of oxidized aluminum foil, and reference numeral i9 a protective varnish coating. As above stated, this protective coating may also have a coloring function. Protective varnish coatings used with a plain aluminum foil may deteriorate or crack, thusexposing the -foil to the destructive action of the packaged goods. When such a coating is Ausedon oxidized foil, even if it becomes damaged,

facing of aluminum foil treated to form on itsl exposed surface an overall articial lm of its own oxide, said film being substantially heavier than a naturally formed iilm and of uniform thickness and being acid and alkali'resistant.

FRANK JOSEPH GAVIN.

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