US3883035A

US3883035A - Easy opening container with safety edge compounds

Info

Publication number: US3883035A
Application number: US399123A
Authority: US
Inventors: Kenneth Richard Rentmeester; Jr Joseph Lambert Godar
Original assignee: American Can Co
Current assignee: Rexam Beverage Can Co
Priority date: 1973-09-19
Filing date: 1973-09-19
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13
Also published as: GB1437158A; FR2243875B2; JPS5055488A; AU6555374A; FR2243875A2; JPS5744540B2; IT1019329B

Abstract

Easy open containers, particularly those of the full-panel type, having safety edge compound applied to the scored metal area of the end are provided whereby, upon pulling the tab to open the container, the compound tears at the score line with a portion remaining on the metal edge of the removable panel as well as on the container rim giving protection to the consumer against cutting on raw metal edges to the ends thus treated.

Description

United States Patent Rentmeester et al.

[4 1 May 13, 1975 1 1 EASY OPENING CONTAINER WITH SAFETY EDGE COMPOUNDS [75] inventors: Kenneth Richard Rentmeester,

Barrington; Joseph Lambert Godar, Jr., Wauconda, both of 111.

[73] Assignee: American Can Company,

Greenwich, Conn.

[22] Filed: Sept. 19, 1973 [21] Appl. No: 399,123

[52] US. Cl. 220/270; 113/121 A; 220/906 [51] Int. Cl. B65d 41/32 [58] Field of Search 220/54, 53, 90.6, 27, 266, 220/270; 113/121 A [56] References Cited UNITED STATES PATENTS 3,754,678 8/1973 Fox et a1 220/54 Hekal et al. 220/54 Kehe 220/54 Primary E.\-aminerGeorge T. Hall Attorney, Agent, or Firm-Robert P. Auber; Ernestine C. Bartlett; George P. Ziehmer [57] ABSTRACT 18 Claims, 3 Drawing Figures EASY OPENING CONTAINER WITH SAFETY EDGE COMPOUNDS BACKGROUND OF THE INVENTION This invention relates to containers and in particular to new and improved easy opening ends for containers.

Heretofore metallic containers have been provided with easy-opening means to facilitate the emptying of the contents therefrom. These prior structures have been generally characterized by a structure in which a tear portion defined by a scored line in the container is separated from the container. Although such easy opening containers have been readily accepted by the public, several disadvantages have made their use less than totally satisfactory. Perhaps the major disadvantage has been insufficient protection of the raw, sharp metal edges which result when the removable portion is torn from the end.

Many proposals have been made in the can making industry to solve the problems presented by the unprotected raw metal edges of such containers. Many of such proposals include application of plastisols to the score area of the removable portion so that when the can end is opened, the plastisol will separate along the score line with a portion remaining on the end in the areas of the score line which serves to protect, to a certain extent, the raw metal edge thereby diminishing the likelihood of being cut. Plastisol materials proposed as safety edge compounds are basically vinyl chlorideresin containing suspensions in non-aqueous liquids which do not dissolve the resin at ordinary temperature, such liquids normally being plasticizers. Such suspensions can be converted to films by heating to approximately 340 F to above 380 F depending upon the type of plasticizer used. While the use of plastisols has afforded some protection from raw metal edges, such compounds are totally unsatisfactory for many applications.

A satisfactory safety edge compound should desirably possess the following properties for broad application and use; particularly for containers packed with edible goods:

1. Resistance to edible fats and oils.

2. Suitable extractive levels required by the FDA for food contact surfaces, i.e., insolubility in common solvents such as water, alcohol, etc.

3. Resistance to heat thereby achieving acceptance for aseptic container steam sterilization and thermal heat processing of the packed products.

4. Good adhesion to the various types of resinous coated substrates as well as to laminate and/or unprimed substrates.

5. Curing and drying at low temperatures for easy and economical manufacture.

6. Ready application through conventional equipment and simplicity of manufacture.

7. Satisfactory physical properties, for example, elongation, tensile strength, tear strength, etc. to permit the compound to tear cleanly, i.e., without fragments, stringing and frills when the container is opened.

Plastisols are decidedly deficient in many of the above mentioned criteria particularly where the container is to be packed with edible goods. For example, plastisols, in general, do not meet FDA extractive levels, do not possess resistance to heat and moisture encountered under aseptic processing conditions and require specific primers for adhesion to substrates. Moreover, plastisols require special equipment for their manufacture, heavy duty pump equipment for application and high temperature curing ovens (they generally require temperatures above 380 F for adequate curing) and once applied, the compositions frequently fragment or frill when the container is opened, and become mobile during aseptic sterilization.

Elastomeric polymers, sometimes referred to in the art as rubber sealants have long been known in the art as excellent gasketing and end lining materials resulting in tough gaskets or seals having resistance to fat and oils, usually conveyed by inclusion of organic solvent-insoluble rubbers and resistance to moist heat, usually conveyed through use of a tackifying resin. Such compositions are disclosed and claimed in U.S. Pat. No. 2,767,152, for example, and usually include a solvent-soluble rubber in combination with a solventinsoluble rubber, tackifying resin and filler, diluted with solvent to proper viscosity, to a solids content usually between about 34 to 40%. Such compositions are not suitable for use as safety edge compounds as illustrated further hereinbelow because they are normally too highly elongated resulting in stringing or frilling when the structure is torn. Additionally, the tackifying resin necessarily present in gasketing or lining compounds to prevent deterioration and afford moist heat resistance, when employed in a safety edge compound inhibits drying of the film, causes blocking and sticking and'other problems.

The primary object of this invention is to provide an improved easy-opening container with a safety feature which protects the ruptured score edge of the removable section as well as the metal edge remaining on the container.

Another object of the invention is to provide an easyopening container having protected metal edges employing safety edge compounds which possess all of the advantages above enumerated including resistance to fats and oils, resistance to heat, good adhesion to a variety of substrates, coated and unprimed, and proper elongation and tear properties.

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 drawing, discloses a preferred embodiment thereof.

SUMMARY OF THE INVENTION This invention relates to an easy-opening container, preferably of the type having a full-open and closure seamed to a container body, wherein the end closure includes a peripheral countersink wall, a full-open removable central panel section defined by a peripheral score, an opening tab secured to the central panel and operative upon manipulation to impress an opening force to cause a rupture in the score, to leave a rim between the countersink wall and the score. The improvement comprises providing a safety edge compound, comprising elastomeric polymer compounded with suitable fillers, on the score line to protect the metal edges upon rupturing the score.

Brief Description of the Drawing FIG. 1 is a top plan view of an end closure of an easyopen container of this invention.

FIG. 2 is an enlarged fragmentary vertical section taken along line 22 of FIG. 1.

FIG. 3 is an enlarged fragmentary sectional view similar to FIG. 2 showing a portion of the removable central panel section removed from the container body.

DETAILED DESCRIPTION OF THE INVENTION As a preferred and exemplary form of the present invention, FIG. 1 shows a cylindrical can C having a conventional top end closure having a central wall 12 defined by a substantially peripheral primary score line 14, which defines a removable central panel 24 that includes most of central wall 12, a peripheral secondary score line 15, a rim 16 which merges into an upwardly extending annular countersink wall 18 (FIG. 2) and an annular flange 20 interfolded with the upper end portion of a container body C into a double seam 22 (FIG. 2).

Central panel 24 has an opening tab 26 secured thereto by conventional means, for example, a rivet 28. The opening tab, as illustrated in FIG. 1, has a front portion 30 at one end adjacent score line 14 and a handle portion 32 at the other end. The front portion 30 at one end adjacent score line 14 in this embodiment includes a web portion 36 having a U-shaped slit cut 38 therethrough which defines a flap 40 wherein is located the hole in which rivet 28 is secured. The major portion of front end portion 30 lies outside of U-shaped slit cut 38 so that when handle 32 is lifted upwardly, the front end portion 30 and the rest of tab 26 are free to pivot about rivet 28 to allow nose 34 to rupture score line 14, while flap 40 is held flatly against central panel 12 by rivet 28. The opening tab as illustrated is described only as a specific embodiment herein and it should be understood that other suitable forms of the opening tab may be substituted.

To facilitate opening and easy initial rupture of the primary score 14, a secondary score may be formed in the central panel although the invention is equally applicable to structures devoid of such an auxiliary score.

As best seen in FIGS. 2 and 3, a safety edge compound 46 comprising an elastomeric polymer is present on the undersurface of removable panel section 24 adjacent and covering score line 14 (and score line 15 if present) to protect the edge of the panel section 24 and the rim 16 once the score is ruptured and panel 24 is partly or fully removed from rim l6 and container body C. As shown in FIG. 3, the safety edge compound covers the rim l6 and

score lands

42 and 44 so that should the score rupture with all or a portion of the land remaining with central panel 24 or rim 16, there remains on all edges a protective elastomeric edge.

The compositions employed as safety edge compounds according to the invention consist essentially of elastomeric polymer materials compounded with suitable fillers.

Typical safety edge compounds of the invention will have the following composition:

Percent By Weight -Continued Solid Ingredients Percent By Weight 45-75% pre- 55-25%, pmferably about ferably about 50-60% 50-40% To achieve the desired results herein, the relative proportions of the components should be maintained within the stated ranges. For example compositions containing substantially less than 5% elastomeric polymer result in compounds that are too friable for the purposes of the invention while those containing substantially more than 30% elastomer or less than filler are too stringy for satisfactory use both as a safety edge compound and in conventional nozzle equipment. Similarly, when the ingredients are compounded to have a solids content substantially lower than about 45%, the solution is too thin for satisfactory application. Substantially above solids, the compounds are too viscous for ready application.

The elastomeric polymer component of the compounds of the invention are well known in the art and include butadiene-acrylonitrile copolymers, butadienestyrene copolymers, isobutylene-isoprene copolymers, Natural rubber (polyisoprene), ethylene-propylene copolymer, neoprene, polyacrylic rubber, chlorosulfonated polyethylene (I-Iypalon), etc. and mixtures thereof. Expecially preferred are mixtures of soluble elastomers, particularly those including butadieneacrylonitrile polymers containing about 50 to about 70 percent by weight butadiene and about 30 to 50 percent acrylonitrile. An example of such a copolymer which is commercially available and suitable for use in the present invention is Hycar 1001 available from the B. F. Goodrich Chemical Company. An example of a suitable butadiene-styrene copolymer is Kraton l 101 available from Shell Chemical Company while a suitable isobutylene-isoprene polymer is Butyl O07 available from Exxon Chemical Company. Especially preferred for use herein are mixtures of organic solventsoluble polymers such as butadiene-acrylonitrile/isobutylene-isoprene and butadiene-styrene/isobutyleneisoprene. While the above elastomers constitute preferred embodiments of the invention, it should be understood that other elastomeric polymers may be substituted therefor provided they are soluble in an organic solvent and, when compounded according to the invention, exhibit suitable elongation, tear and tensile strengths to tear cleanly and evenly without fragmenting, frilling or stringing.

The filler component of the compounds of the invention is likewise selected from compounds well known in the art and includes titanium dioxide, silica, zinc oxide and other fillers that function in accordance with the present invention. Especially preferred are high density (3 or above) nonreinforcing type fillers which form compounds with the elastomer having adequate tear properties. Such components may be employed alone, in combination with each other or with other fillers and/or pigments well known in the art.

The liquid medium or vehicle employed herein may include suitable solvents or diluents which may be selected to form solutions, dispersions, etc., based on the solubility of the particular polymer, ease of drying and ecological properties, as desired. Thus, the vehicle may include water, organic and inorganic solvents, diluents and combinations thereof. Particularly preferred I added to the vehicle, with or without milling as deemed necessary after which the elastomers will be added, preferably with agitation to aid in solvation or dispersion of the same.

In a typical procedure of the process, metal sheet, which may be aluminum, tinplate, tin-free steel, etc., is coated with typical primer coatings which may be any of a variety of conventional coatings including oleoresinous lacquers or enamels such as tung oil or linseed oil based materials, epoxy esters, epoxy-phenolics, acrylics, vinyls, etc. The primed sheet is formed into the basic end and converted to an inside or outside scored full-panel, easy-open end by any of conventional procedures known in the art. A safety edge compound of the invention is applied to the score area by any suitable means, employing preferably conventional nozzle equipment, and is dried to evaporate at least a portion of the vehicle, utilizing standard equipment, for example, a helical dryer, at a temperature of about 100 to 180 F, preferably about 130 F for about 6 minutes. Complete cure of the compound is not necessary so long as sufficient vehicle is removed to preserve the integrity of the compound whereby it can serve the desired function.

The primary score land may be of any length desired,

generally from about 0.001 to 0.005 inch and may be formed by either an inside or outside score. The secondary score depth, when present, will be substantially less than that of the primary score, normally about 0.003 inch or less and likewise may be on the interior or exterior surface of the end.

Thicknesses of the safety compounds may vary as desired and preferably will be in the range of about 4 to 25 mils with 8 to mils being the preferred range. The width of the compound as applied likewise may vary as desired, usually from about a one-eighth inch minimum to as wide as desired and as is economically feasible. The compound may or may not be applied to cover the secondary score, as desired although it will be preferably cover both the primary and secondary score in the practice of this invention. Similarly, the compound may be applied to the interior or exterior surface of the end with interior application being most preferred herein.

The following examples are illustrative of various compositions suitable for use in this invention:

EXAMPLE ll Ingredients Percent by Weight butadieneacrylonitrile l 1.0 copolymer (Hycar 1001) isobutylenc-isoprene 0.5 copolymer Butyl 007) TiO 11.0 SiO- 32.5 Toluene/Methyl ethyl ketone 45.0

The following examples are illustrative of elastomeric compositions known in the art of gasketing or sealing compounds, which are not satisfactory as safety edge compounds in accordance with this invention.

EXAMPLE III This formulation is as disclosed in US. Pat. No. 2,767,152 to Biermann:

The above formulations (Examples I to IV) were applied to a primed, scored, metal end in accordance with the invention and dried at F for about 6 minutes or until a substantial amount of vehicle was evaporated. The compositions of Examples 1 and II had a solids content of about 55 percent while that of Examples 111 and IV was about 36 percent.

The compounds of Examples 111 and IV were found to be totally unsatisfactory for use as a safety edge compound. Drying was inhibited by the tackifying resin in each case necessitating at the least doubling of drying time. Upon rupturing the score line, the compounds of each of these examples were excessively stringy and were found to be too soft to give raw edge protection. Additionally, ends containing compounds of these examples were extremely difficult to process because of the tackiness of the compounds which caused blocking or sticking of the ends one to the other.

The compounds of Examples 1 and II were not tacky, did not block, provided excellent protection to the metal edges, tearing cleanly and easily without stringing, fragmenting or frilling and exhibited good retention of adhesion to the metal ends even when opened at vending temperatures of 150 F or higher. The compound of Example l is particularly well suited for use on container ends under aseptic conditions while the compound of Example II is the preferred fat resistant compound.

It is thought that the 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 the ingredients, the identity and proportions of the 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 or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim:

1. In a metal container wherein a full-open end closure is seamed to a container body, wherein the end closure includes a peripheral countersink wall, fullopen removable central panel defined by a substantially peripheral score line and an opening tab secured to the central panel and operative upon manipulation to cause a rupture in the score to leave a rim between the countersink wall and the score, the improvement which comprises:

a safety edge compound having sufficient elongation,

tear and tensile characteristics to tear without substantial fragmenting or stringing upon removal of the central panel derived from a composition comprising from about to about 30 percent of an elastomeric polymer, liquid vehicle and from about 95 to 70 percent filler, said compound covering the score and tearing to protect the metal edges of the removable panel section and the rim upon rupture of the score.

2. The container of claim 1 wherein the compound is applied to the interior surface of the scored end.

3. The container of claim 1 wherein the composition has a solids content of about 45 to about 75 percent.

4. The container of claim 3 wherein said elastomer is selected from the group consisting of copolymers of butadiene-acrylonitrile, butadiene-styrene, isobutylene-isoprene, ethylene-propylene, polyisoprene, neoprene, polyacrylic rubber, chlorosulfonated polyethylene and mixtures thereof.

5. The container of claim 4 wherein said elastomer is a mixture of butadiene-acrylonitrile and isobutyleneisoprene copolymers.

6. The container of claim 4 wherein said elastomer is a mixture of butadiene-styrene and isobutyleneisoprene copolymers.

7. The container of claim 1 wherein said filler is titanium dioxide, zinc oxide, silicon dioxide and mixtures thereof.

8. The container of claim 1 wherein said elastomer is a mixture of butadiene-acrylonitrile and isobutyleneisoprene copolymers, said filler is a mixture of titanium dioxide and silicon-dioxide and said vehicle is a methyl ethyl ketone-toluene mixture.

9. The container of claim 1 wherein said elastomer is 5 a mixture of butadiene-styrene and isobutyleneisoprene copolymers, said filler is a mixture of titanium dioxide and silicon dioxide and said vehicle is a toluene-hexane mixture.

10. The container of claim 1 wherein said compound is derived by evaporation of at least a portion of the vehicle from said composition after application to the metal end.

11. The container of claim wherein said compound is derived by heating said composition to a temperature of about 100 F to about 180 F.

12. A method for making an improved, full-open end closure comprising, in combination:

a. forming a can end, including a peripheral countersink wall and flange means to be seamed to the end of a container body,

b. forming a score line in said end, said score line defining a removable central panel portion which is separable from a rim in said countersink wall of said end,

c. attaching finger tab means to a portion of said removable central panel portion,

d. applying to said score line a composition comprising an elastomeric polymer, liquid vehicle and filler and e. removing at least a portion of said vehicle to provide a cured compound which protects the metal edges of the removable central panel portion and the rim upon rupture of the score.

13. A method as defined in claim 12 in which said composition is applied to the interior surface of the scored end.

14. A method as defined in claim 12 wherein the compound consists essentially of from about 5 to about 30 percent by weight of an elastomeric polymer or mixtures thereof, and from about 70 to about 95 percent by weight of a filler.

15. A method as defined in claim 14 wherein the composition has a solids content of about 45 to about 75 percent.

16. A method as defined in claim 15 wherein said elastomer is selected from the group consisting of copolymers of butadiene-acrylonitrile, butadiene-styrene, isobutylene-isoprene, ethylene-propylene, polyisoprene, neoprene, polyacrylic rubber, chlorosulfonated polyethylene and mixtures thereof.

17. A method as defined in claim 16 wherein said filler is titanium dioxide, zinc oxide, silicon dioxide and mixtures thereof.

18. A method as defined in claim 17 wherein said cured product is provided by baking said end at a temperature of about 100 F to about 180 F.

Claims

1. In a metal container wherein a full-open end closure is seamed to a container body, wherein the end closure includes a peripheral countersink wall, full-open removable central panel defined by a substantially peripheral score line and an opening tab secured to the central panel and operative upon manipulation to cause a rupture in the score to leave a rim between the countersink wall and the score, the improvement which comprises: a safety edge compound having sufficient elongation, tear and tensile characteristics to tear without substantial fragmenting or stringing upon removal of the central panel derived from a composition comprising from about 5 to about 30 percent of an elastomeric polymer, liquid vehicle and from about 95 to 70 percent filler, said compound covering the score and tearing to protect the metal edges of the removable panel section and the rim upon rupture of the score.

5. The container of claim 4 wherein said elastomer is a mixture of butadiene-acrylonitrile and isobutylene-isoprene copolymers.

6. The container of claim 4 wherein said elastomer is a mixture of butadiene-styrene and isobutylene-isoprene copolymers.

8. The container of claim 1 wherein said elastomer is a mixture of butadiene-acrylonitrile and isobutylene-isoprene copolymers, said filler is a mixture of titanium dioxide and silicon-dioxide and said vehicle is a methyl ethyl ketone-toluene mixture.

9. The container of claim 1 wherein said elastomer is a mixture of butadiene-styrene and isobutylene-isoprene copolymers, said filler is a mixture of titanium dioxide and silicon dioxide and said vehicle is a toluene-hexane mixture.

11. The container of claim 10 wherein said compound is derived by heating said composition to a temperature of about 100* F to about 180* F.

12. A method for making an improved, full-open end closure comprising, in combination: a. forming a can end, including a peripheral countersink wall and flange means to be seamed to the end of a container body, b. forming a score line in said end, said score line defining a removable central panel portion which is separable from a rim in said countersink wall of said end, c. attaching Finger tab means to a portion of said removable central panel portion, d. applying to said score line a composition comprising an elastomeric polymer, liquid vehicle and filler and e. removing at least a portion of said vehicle to provide a cured compound which protects the metal edges of the removable central panel portion and the rim upon rupture of the score.

18. A method as defined in claim 17 wherein said cured product is provided by baking said end at a temperature of about 100* F to about 180* F.