US2138439A - Container closure and lining material therefor - Google Patents

Description

Nov. 29, 1938.

A. H. WARTH* 2,138,439

vCONTAINER CLOSURE AND LINING MATERIAL THEREFOR` Filed March 51, 1956 Patented Nov. 2,9, 1938 CONTAINER CLOSURE AND LINEN@ MATERIAL THEREFR Albin l1. Warth, 'Baltimoref Md.,

assignor to Crown Cork & Seal Company, Inc., Baltimore,

Md., a, corporation of New `ilork Application March 31, 1936, Serial No. '71,911

2 Claims.

The present invention relates to container closures and particularly to closures of the center spot crown type. Caps of this type comprise a metallic shell having a crimped skirt, a cushion 5 liner of natural cork or cork composition, and a facing layer of smaller diameter than the cushion disc, adhesively 'secured to the disc to cover the central portion thereof, and to leave exposed an annular marginal portion, adapted to l0 cooperate with the exterior portion of the sealing lip of the bottle neck to provide a tight seal. As is well known, the center spot constitutes a liner and prevents the contents of lthe bottle from coming in contact with the cushion disc.

In the past, satisfactory results have been obtained by using metal foils, such as aluminum foil, as the lining material. Such foils ,have been adhesively united to the cushion disc by means of thermoplastic adhesives, so that the. caps and spots can be rapidlyvassembled by uniting the spots to the cushion discsby heat and pressure. Attempts have been made to use exteriorly varnished paper as a spotting material, and fairly satisfactory results have been accomplished by combining a4 sheet of paper, having a varnish coat on its exterior surface, with an interior layer of gutta percha., the latter acting as a thermoplastic adhesive between the paper face of the spot and the cork cushion. However,

certain defects have been encountered in lthe commercial use of such single surface varnished spots. For instance, the capillarity of the paper inwardly of the varnish layer results in Aabsorption of the liquid contents of the bottle by 3,-, the paper, particularly in connection withv the sealing of beverages which must be subjected to a pasteurizing or sterilizing operation, such as beer. Any minute break in such a varnish coating results in permitting the 'liquid to penetrate 40 the. spot and soften the paper. If paper of the /bleached kraft type is used, the spot will be subjected to an undesirable swelling action and disintegration which renders the spot useless and causes the beverage to deteriorate in quality. 4., The same difficulty is encountered with other papers such as Express paper, although to a lesser degree.

Attempts have been made to avoid this capillary absorption of'the paper by saturating the paper with varnish, or coating it on both surfaces, but a satisfactory spot of this type could not be made, prior to the present invention, because the gutta percha adhesive would not adghere with suicient tenacity to a varnished surface. Consequently, when a sheet of kraft paper (ci. ais- 39) or the like was given a coating of varnish on its inner and outer surfaces, it could not be satisfactorily adhesively united to the cork `cushion by the standard thermoplastic adhesive .of the prior art, i. e., gutta percha. As a result, all commercial-varnish paper spots,` prior to the present invention, consisted of a layer of paper, a single outer layer of varnish, and an inner layer of gutta percha united directly to the inner, uncoated paper face of the spot, and even so, the paper spots were not as commercially satisfactory as the metal foil spots.

In my prior United States Patent No. 1,956,481, April 24, 1934, I have disclosed and claimed a novel spot for crown caps, comprising a metal foil disc, or a single surface varnished paper disc,

in combination with a novel thermoplastic ad-' hesive comprising a nitrocellulose and a resin. When used with metal foil, this adhesive has been found to be far superior to `gutta percha. It has gone into wide commercial use as a means for uniting foil spots to the cushion liners of crown caps.

`When attempts were made to substitute this new adhesive material for gutta percha, as a means for securing varnish coated paper spots of the prior art to the cushion liners of crown caps, somewhat unsatisfactory results were encountered. satisfactory bond, the nitrocellulose-resin ladhesive must be in the form of a continuous surface layer or film on the material, such as paper or foil, with which -it is to be used. If it is absorbed by the web of material, the surface layer will be discontinuous and will lack the continuity of a nlm. At the places where such absorption occurs and where the lm is broken, the adhesive effect under heat and pressure"is poor. When attempts were made to use such an adhesive with the single surface varnish coated papers of commercial type, as a substitute for the more expensive gutta percha adhesive, I discovered that the absorption of the adhesive by the paper was such as to destroy the uniform filming of the adhesive and resulted in a poor bond between the paper and the cushion layer. Consequently,

I discovered that, in order to make a prior to the present invention, it I was thought that the recently developed nitrov cellulose-resin could not displace gutta percha adhesives in the varnished paper spot art, and that it would be useful only in connection with metallic foil spotting materials.

Upon discovering the cause of the defect in the action of the nitrocellulose-resin type loi' thermoplastic adhesive when used with paper-355 VAll 100 polmdsoilsoluble 100% mnamemtheabsorpuon'of Madneaveby paper. I conceived the idea of preventing on by rst both faces, in

-paper saturate the 'paper fibres to such an extent that absorption of the contents of the bottle by the paper is effectively prevented, and me capillarity of the paper eliminated. The nitrocellulose-resin adhesive' lms out Yupon the inner varnish layer of the paper spot with the desired continuity, and the spot so coated with an inner layer of a varnish cooperates with the nitrocellulose-resin adhesive with the same eiiciency as a metal foil spot.

The present invention is not limited to the use of a thermoplastic adhesive of the type disclosed in my prior Patent No. 1,956,481, referred to above. as I have found that other thermoplastic adhesives may be used to form a suitable bond between the cork cushion and the inner varnish face of a paper spot. Such adhesives include chlorinated rubber-resin adhesives, and an adhesive comprising an ethyl ester of shellac and nitrocellulose;

The varnish coating used on the inner and.

outer faces of the paper spot maybe either an oil varnish solution, or a synthetic resin varnish. Although the paper preferred is a bleached kraft paper, because of its strength and cheapness, the invention is not confined to its use, as any good strong paper may be substituted. Express paper, for certain types'of spots, has been found to be particularly satisfactory. A typical oil varnish for coating the paper may be made in accordance with the following formula:

phenolic resin 2? gallons China-wood oil 3 gallonsfourhourbodiedlinseed oilV 72 ounces cobalt drier 63 ounces manganese drier 65 gallons mineral spirits f Coole- The resin and China-wood oil are heated together to 470' F. in about thirty-four minutes. Hold for body and get three and one-half foot string on piece of metal. Add bodied linseed oil and cool to 440 F. Add mineral spirits and A typical synthetic resin varnish for 'coating or satmatingthe paperV may be made in accordance with the following formula:

Y Y Parts Synthetic resin (e. g. rezyl resin) Butyl acetate 20 Ethyl acetate 20 Butyl cellosolve 20 75 '.llieoilvarnishischaracterinedbyitshignV aise-isc viscosity, the usev of high` boiling solvents, the limited penetration into the paper, and the requirement for thorough baking or drying of the coating to polymerize and, oxidize the oil containing constituent.I

The synthetic resin solution varnish is of lower viscosity, and its solvents are a mixture ofl lower and higher boiling solvents. It penetrates the paper quite rapidly, and-the drying may be accomplished in a short time cycle.

It should 'be understood that the organic solvents for the resin solution varnishes are not limited to ,those given in the above formula, as

such solvents as cellosolve (B. P. 135 0.), methyl n. amyl ketone (B. P. 147-152 C.), hexone (B P. 113-119" 0.), acetone (B. P. 56 C.), methyl acetone (B. P. 50-67 C.), and toluol (B. P. .110 C.) are all useful for such resin solutions.

The thickness of the paper layer is selected according to the factors of (1) the degree of penetration, (2) its physical strength,l and (3) its cost. For coating with oil varnishes, the paper is preferably Within the range 'of .0035" to .0045". For dip resin solutions it should be between .0025" and .0035". The varnish iilms bring these papers in coated condition to a greater thickness, e. g., .0053 for a .0045" paper, and .0042" for dipped .0035 paper. Thenitrocellulose-resin adhesive film is .0015" to ;0025 thick. The invention, of course,visv 'not to be conned to` these particular thicknesses of paper, varnish,

and/or adhesive. It is usually desirable to keep I nishes, and if the solution is suilciently thin,

no wipers are needed. If the varnish is somewhat viscous, it can be applied satisfactorily with coating rolls, for instance, by the use of a fountain 'with pick-up distributor and applicator rolls for one side, and a similar set for the other side. Drying may be accomplished in a vertical oven in which the varnish coated paper is festooned by running the same over supporting rolls at the top of the oven, and then down for rewind. The oil varnish described above should be dried at 220 F.for twenty-live minutes. The resin solution may be dried at 260 F. for ten to twelve minutes as will be appreciated, such varnishes are not thermo-plastic.v

In the accompanying drawing:

Figure 1 shows an enlarged plan view of a spot crownaccording to the present'invention.

Figure 2 is a vertical sectional view, on an enlarged scale, of the'device of Figure 1.

Figure 3 is a diagrammatic plan view of the spot of the present invention, with the various layers exposed to view. y

Figure 4 is a greatly enlarged cross sectional view of the laminated material which is used to form the spot of the present invention.

In the drawing, a crown cap is shown comprising aA metallic shell I0 having the usual -top Il and adown-turned crimped skirt I 2. A cushion hner I3 which may be either natural cork'or a granulated cork composition, is adhesively For instance, the paper may be4 united to the interior of the shell by an appropriate adhesive I4. The center spot I5 is secured concentrically to the inner face' of the cushion liner I3. The spot comprises a layer of paper I6, an outer varnish layer II, an inner varnish layer I8, and a thermoplastic adhesive layer I9. The spot is preferably secured to lthe cushion disc by heat and pressure.

The paper layer IS preferably is a smooth nished, bleached kraft paper, although other papers, suchias Express, are satisfactory.

The varnish layers I1 and I8 may'consist of either an oil varnish, or a resin varnish, of the types discussed above. Preferably, the varnish penetrates the paper somewhat, as indicated dia- .grammatically in Figure 4, and the capillarity of the paper and, consequently, its tendency to absorb the contents of the bottle, is thus diminished. As a result, an impervious facing Il is presented to the contents of the bottle, and an impervious surface I8 is provided upon which the adhesive may be spread in a continuous lm, without any penetration into the paper.

The thermoplastic adhesive I9 may be of the type described in detail in my prior Patent No. 1,956,481, or it may comprise a chlorinated rubber-resin adhesive. Anvadhesive of a suitable type may comprise 20 parts 50% solution of ethyl ester of shellac and 15 parts of 10% solution of nitrocellulose (5 sec.) Such an adhesive has been found to be particularly eiicient as a.

bonding medium between an inner varnished surface of a paper spot and a cork disc.

said varnish rendering the paper non-adsorptive to and being adhesively compatible with said adhesive.

2. In a cap which includes a metal shell and a cushion liner, a facing of the center spot type of lesser diameter than the cushion liner, said facing comprising a layer of paper having a nonthermoplastic varnish coating on both its faces and a continuous layer of thermoplastic adhesive comprising nitro-cellulose and a resin between its inner varnished face and said cushion liner, said varnish rendering 'the paper non-adsorptlve to and being adhesively compatible with said adhesive. Y

` ALBIN H. WARTH.

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