Abstract:
A seal and method of forming a seal for a reclosable container includes a removable cap that is selectively received over a pour opening formed in a can body. The method includes applying a plastisol to an interior surface of the cap, curing the plastisol at an elevated temperature in the cap, and cold-forming the cap containing the cured plastisol therein. In another arrangement, an EVA seal material is extruded into the cap and the seal is subsequently cold-formed in the cap.

Description:
BACKGROUND 
       [0001]    This disclosure relates to containers or cans of a wide variety of sizes, volume, etc. used in the food and beverage industry or in connection with other fluid products such as oil, paint, powders, etc. More particularly, this application relates to reclosable containers as disclosed in commonly owned U.S. Pat. Nos. 6,082,944 and 6,015,062, and to the disclosure of related published International Application W0 2006/072079, the disclosures of which are expressly incorporated herein by reference. 
         [0002]    The disclosure is related to seals within a container cap having a general shape of an inverted cup that fits closely about and interacts with a container body having a neck. The neck has a pour opening at its top and a plurality of thread lugs formed outwardly in the neck material at a predetermined spacing below the pour opening. The thread lugs interact with a plurality of lugs extending inwardly from a perimeter of the cap and spaced about a lower rim of the cap to draw the interior surface or underside of the cap toward the pour opening and to complete a seal between the neck/body and cap. 
         [0003]    Previous seal constructions for this type of reclosable container have included various types of seal materials applied to the underside or interior surface of the cap. Primarily a pre-formed ring, for example of polypropylene, has been widely used as a preferred form of seal. The materials of construction of such seals may vary with the type of content in the container. However, there is a need to provide a different approach to placing seals of different compositions within the containers, as may be required to accommodate the needs of properly packaging different contents of the container. Instead, it would be desirable to provide a seal that is useful for a wide variety of container contents and needs. Such needs may involve pressurization or vacuum packing of the container contents, or an ability to withstand the high temperature and elevated pressure of retort operations after filling and closing, or possible exposure to wide ranges of temperatures from other sources after filling and sealing. These are but a few potential requirements encountered in adapting such a container to a large variety of potential contents. 
         [0004]    As shown and described in W0 2006/072079, the disclosure of which is attached and expressly incorporated herein by reference, the seal is typically extruded from pellets heated to approximately 340° F. The material was extruded into the cap, such as an aluminum cap, and then cold-formed with a tool to match a lip curl on the dome of the container. The seal could be formed into an annulus or ring that only covers and seals on the lip curl, or could be formed into a disk to cover the center area of the cap with the form for the lip curl. This seal worked very well and held high pressures, over approximately 140 PSI. One problem was that the seal would not stick to the aluminum cap and could potentially fall out when the cap was removed from the can. A coating material provided on the cap is designed to keep anything from sticking to it. The coating is in widespread use, and therefore changing the coating would be a difficult change over the entire industry. 
         [0005]    One way to keep the seal from falling out was to mechanically hold the seal in. For example, an ethylene vinyl acetate (EVA) copolymer material was extruded and supplied as a roll of material. Seals were blanked or cut from the EVA roll stock to form a flat disk. The flat disk was generally oversized so that the disk would not fall out of the cap interior i.e., the perimeter edge of the oversized flat disk would interfere with the lugs provided on the cap and therefore be effectively retained within the cup-shaped cavity of the cap in a position where the seal would abuttingly engage the lip curl on the container. However, the cost of this EVA material has recently substantially increased, thus requiring potential alternative options. Although disk seal performance was generally acceptable, this type of seal did not perform as well as extruded or cold-formed seals. The EVA material was only suitable for cold fill products, and would not work well for hot fill or pasteurized products such as beer. 
         [0006]    Alternatively, a solid thermoplastic elastomer (SOR) material was tested for pasteurization but has not performed well. The seal either fell out of the cap or the on-off torques developed between the cap and container were too high. Moreover, the SOR material is extremely expensive when compared to the EVA material. 
         [0007]    Consequently, a need exists for a different material and method of forming a seal for a removable, re-sealable cap (typically steel or aluminum) that overcomes the above-noted problems, and others, in a manner that is easy to manufacture, repeatable, effective, inexpensive, usable in a wide array of end uses (e.g., pressure, vacuum, steel cap, aluminum cap, thermal extremes, thermal cycling 
       SUMMARY 
       [0008]    A method of forming a seal for a reclosable container having a removable cap that is selectively received over a pour opening formed in a can body, including applying a seal material to an interior surface of the cap. If the seal is a plastisol, the method includes curing the plastisol at an elevated temperature in the cap. The seal is then cold-formed to the desired shape. 
         [0009]    The seal can be fowled into an annulus or ring that only covers and seals on the lip curl, or could be formed into a disk to cover the center area of the cap along with the desired form for the lip curl. 
         [0010]    The seal works well at high pressures, as well as in vacuum situations, and is also applicable to high temperature environments. 
         [0011]    A reclosable container has a body with a pour opening formed therein. A removable cap is selectively received over the pour opening of the can body. A seal is provided along at least a portion of an interior surface of the cap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a plan view of a conventional extruded seal. 
           [0013]      FIG. 2  is an elevational view of the seal of  FIG. 1 . 
           [0014]      FIG. 3  is a plan view of an interior surface of a conventional lugged cap receiving the seal of  FIG. 1 . 
           [0015]      FIG. 4  is a plan view of an interior surface of a conventional lugged cap receiving a seal disk. 
           [0016]      FIG. 5  is an elevational view of the seal disk of  FIG. 4 . 
           [0017]      FIG. 6  illustrates the machinery for manufacturing the seal disk of  FIG. 4 . 
           [0018]      FIG. 7  shows the scrap left from a web of the seal material as a result of the manufacturing of the seal disks. 
           [0019]      FIG. 8  is a plan view of a lugged beverage cap interior and illustrating the new seal formed therein. 
           [0020]      FIG. 9  is a view similar to  FIG. 8  and showing the new seal formed in a larger food cap. 
           [0021]      FIG. 10  illustrates the applicator dispensing the fluidized plastisol along an interior face of the cap. 
           [0022]      FIGS. 11 and 12  show the cold form tooling station that receives the cap from  FIG. 10  after has been baked. 
           [0023]      FIG. 13  shows an oven for baking a plastisol and/or pre-coat coating on the interior surface of the cap. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The development of the plastisol cold-form seal and various images of the original extruded and cold formed seals ( FIGS. 1-3 ) and current EVA seal disks ( FIGS. 4-7 ) are shown in the attached drawings. 
         [0025]    More particularly,  FIGS. 1-3  show a conventional extruded and cold-formed seal  100  received in a cup-shaped cap  110 . The seal  100  has a cross-sectional profile conducive to formation by extrusion and is typically formed into a generally C-shaped conformation  120  having an enlarged inner diameter and a space or gap  130  between opposite ends  132 ,  134  of the seal. When the seal  100  is positioned in the cap  110 , the seal is reduced in diametrical dimension, i.e., the opposite ends  132 ,  134  abut against one another and form a circumferentially continuous seal member received in the cap interior. As shown in  FIG. 3 , the seal  100  is disposed at a location radially inward of the cap inner perimeter, and preferably dimensioned to engage the lip or outer curl of the can body. 
         [0026]      FIGS. 4-7  show a typical EVA seal  200  received in the interior of the cup-shaped cap  210 , and mechanically held in position by an interference engagement between a peripheral portion or perimeter of the seal  200  and the lugs  212  that extend radially inward toward the cap interior. The seal  200  is preferably cut from a continuous web  220  of seal material, and for example may have a thickness ( FIG. 5 ) on the order of 0.035″. As shown in  FIGS. 6 and 7 , the web  220  of material proceeds through a blanking station  230  where cooperating tool surfaces out or blank the individual seal disks  200  from the web. As perhaps best illustrated in  FIG. 7 , a large amount of scrap material  240  remains once the individual seal disks  200  have been formed. 
         [0027]    The new seals  300  formed on the interior face of the cap  310  are illustrated in  FIGS. 8-9 , while the applicator  320  and cold form tooling station  330  are shown in  FIGS. 10-12 , and a baking oven  340  shown in  FIG. 13 . 
         [0028]    According to the present disclosure, and for example when working with steel reclosable food cans, the cap  310  typically includes a coating on the interior surface. This coating  350  allows a plastisol material (which is used for sealing) to stick to the cap  310 . One accepted definition of plastisol is a suspension of polyvinyl chloride (PVC) particles in a plasticizer. The plastisol advantageously flows as a liquid and can be poured into a heated mold or is sufficiently viscous an as to be sprayed as in the present disclosure (and as will be further described below). 
         [0029]    The plastisol is sprayed into a cap  310  (that is, sprayed on the interior surface of the cup-shaped cap) and then cold-formed. The plastisol material is typically used for retort products, because the can and cap  310  will not be exposed to temperatures over 250° F. during the retort process, that is, pasteurized products are typically processed below 165° F. Therefore, using the plastisol material for pasteurized products seems to exhibit good performance characteristics and passes the pasteurized tests, as well as exhibiting low on-off torques in attaching and removing a cap  310  from the associated container. The plastisol is sprayed over the entire interior surface in one preferred method, but one skilled in the art will recognize that the spray may be more directed and only be applied to a portion of the interior surface of the cap. 
         [0030]    One issue with the plastisol, however, is that the material will not stick to an aluminum cap  310  ( FIG. 8 ) due to the coating. Therefore, a pre-coating  350  was found that when heated to 40° F. for a predetermined time. (e.g., 11 min), would allow the pre-coating  350  to stick to the aluminum cap  310  and then the plastisol  300  would adhere to the pre-coating. Preferably, after the aluminum cap  310  is heated in order to stick the pre-coating  350  to the aluminum surface, the plastisol  300  is then sprayed into the cap (on to the interior surface of the cup-shaped cap at a thickness of approximately 0.030-0.040″ although other ranges might be used), heated to approximately 400° F. for a preselected time (e.g., approximately 2 min.) to cure, and then cold-formed into a desired configuration. 
         [0031]    These plastisol, cold-formed seals  300  perform well for pasteurized products with low on-off torques. The plastisol seal  300  also out-performed the EVA disk used for cold fill beverages. Further, the plastisol cold-fowled seal  300  held higher pressures with low on-off torques. Moreover, the plastisol seal  300  can be used for almost all products and the cost is significantly less than other seal alternatives. The plastisol opens the possibility for new markets such as beer, where the plastisol, cold-formed seal  300  can also be used for cold fill products at a considerable savings for the can maker. 
         [0032]    The process of applying the new plastisol, cold-formed seal of the present disclosure (or sometimes referred to as manufacturing the seal) would be roughly the same for a steel or aluminum container/cap (after applying the pre-coat to the aluminum). Particularly, the process would include applying e.g., spraying, the plastisol into the cap  310 , baking the plastisol after application to the cap (e.g., baking at approximately 400° F. in an oven such as depicted in  FIG. 13 ) for a predetermined time (approximately 2 min.), and then cold fowling the plastisol (in the tooling station of  FIGS. 11 and 12  to form the final profile or configuration of the seal in the cap that cooperates with the body lip or curl of the can body. As the lugs of the cap engage the thread lug portions of the can body during relative rotation of the cap in first direction relative to the body, the cap is axially drawn into sealed abutting engagement with the outer end of the can body. 
         [0033]    In another arrangement, the EVA pelletized material is formed into an extrusion and a bead applied to the inner surface of the cap. The extruded bead can be placed at a desired thickness and desired location. Thereafter, the seal is cold-formed in a tooling station such as shown in  FIGS. 11-12 .