Abstract:
A sealing member for a container including a polyethylene or polypropylene foam or film layer bonded to a foil layer. A first PET tab defining layer over at least a first portion of, but is not bonded to the first portion of, the polyethylene or polypropylene foam or film layer. A polypropylene film layer bonded to both a second portion of the polyethylene or polypropylene foam or film layer not covered by the first PET tab defining layer and also to the first PET tab defining layer itself, the bonds being established by an adhesive resin and catalyst to provide a bonding strength sufficient to hold against a manually generated force. The sealing member also includes a second PET layer bonded to the polypropylene film layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of prior application Ser. No. 12/026,691, filed Feb. 6, 2008, which claims benefit pursuant to 35 U.S.C. 119(e) of U.S. Provisional Application No. 60,896,827, filed Mar. 23, 2007, which are both hereby incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates generally to a sealing member for closing the mouth of a container, the sealing member having a graspable tab on its upper surface to expedite its removal from the container. 
         [0004]    2. Description of the Related Art 
         [0005]    In the Figures, the last two digits of the reference numbers for elements that correspond in the various Figures always match. Hence, the hot melt bonding material or adhesive layer, which is essentially the same in all of the Figures, is assigned the reference number  122  in  FIG. 1 ,  222  in  FIG. 2 ,  322  in  FIG. 3 ,  422  in  FIG. 4 , and  522  in  FIGS. 5 and 6 . Once such an element has been described with respect to one Figure, the description of that element is incorporated by reference into the descriptions of corresponding elements of other Figures unless the text or context indicates otherwise. 
         [0006]    It is often desirable to seal a bottle, jar, or other container having a screw-on cap by providing a sealing member that attaches across the mouth of the container before the cap is screwed down onto the container for the first time. When the cap is later removed after purchase, the purchaser must penetrate, break, or otherwise remove the sealing member before the contents of the container may be accessed. The cap may then be screwed back into place to keep the contents fresh and to keep the contents from spilling out. If the sealing member is not present when the container is first opened, or if it is damaged, then the purchaser knows that the contents of the container may have been tampered with. 
         [0007]    Many such sealing members are known which have tabs attached to their upper surface to facilitate their removal. One simply grasps the tab and pulls it to one side, and the entire sealing member is removed from the container in a single motion. 
         [0008]    U.S. Pat. No. 5,514,442, which issued to Michael P. Galda, et al. on May 7, 1996 discloses the sealing member  100  shown in  FIG. 1  (which is derived from  FIG. 4  of the &#39;442 patent). The sealing member  100  is a laminated structure the lower half of which is formed from a 0.00150″ thick aluminum foil layer  110  the underside of which is bonded to a hot melt bonding material or adhesive layer  122 . The upper half of the sealing member  100  is formed from a 0.00400″ thick sheet of bleached kraft paper  102  (having a nominal weight of 52 pounds) the lower half of which is glued (by means of adhesive layer  114 ) to a 0.00100″ thick polyester layer  104  (most likely a sheet or film of PET, or Polyethylene Terephthalate). As shown, the upper and lower halves of the sealing member  100  are joined by means of an adhesive layer  116  (SPENBOND adhesive 650/651, supplied by NL Chemicals—650 is a water dispersed urethane-laminating adhesive, and 651 is a water dispersible curing agent for the adhesive) which extends only half way (left-to-center) which joins the aluminum foil layer  110  to the polyester layer  104 , leaving a gap  124  to the right. The sealing member  100  is circular and is die-cut from a much larger sheet of laminated materials, the cutting being positioned to cause the gap  124  to be present in each sealing member  100 , thereby forming a removal tab that comprises the kraft paper  102  and the polyester  104  layer above the gap  124  to the right in  FIG. 1 . The &#39;442 patent goes on to teach that this circular sealing member  100  is inserted deep into the screw-on cap (not shown) which is then screwed onto the container (not shown). Induction heating applied to the neck of the container then heats up the aluminum foil layer  110 , causing the hot melt bonding material or adhesive layer  122  to melt and thereby seal the sealing member  100  to the top of the container. After the container is purchased, the purchaser removes the cap and then grasps and pulls on the removal tab and thereby removes the sealing member  100  from the container. 
         [0009]    U.S. Pat. No. 5,702,015, which issued to Joseph M. Giles, et al. on Dec. 30, 1997, teaches a somewhat different design for a sealing member  200  that is shown in  FIG. 2  (which is derived from  FIGS. 1 and 3  of the &#39;015 patent). In  FIG. 1 , the adhesive layer  116  may sometimes fail during tab removal, leaving the sealing member  100  still at least partially attached to the container. To provide a stronger seal between the upper and lower halves of the sealing member, the sealing member  200  shown in  FIG. 2  coats the aluminum foil  210  with a PE (polyethylene) foam layer  208 . The upper half of the sealing member  200  comprises a polyester (again probably PET) upper layer  202  glued to a second PE (polyethylene) foam layer  204 . A release layer  206  is inserted between the two PE foam layers  204  and  208  over half their length, as is shown. This release layer  206  is formed from a material that resists bonding to at least one of the PE foam layers  204  and  208 . The upper and lower halves of the sealing member  200  are joined by heating the layers  204  and  208  during manufacture so that the layers  204  and  208  merge and become one thicker PE foam layer in the left half of the sealing member  200 , thus forming a joining of the upper and lower halves of the sealing member  200  without an adhesive layer (such as the layer  116  shown in  FIG. 1 ). The two layers  204  and  208  are separated from each other by the release layer  206  (to the right in  FIG. 2 ), and hence a removal tab is formed in the upper right half of the sealing member  200 . The resulting removal tab structure is stronger than that shown in  FIG. 1  because the merger of the two layers  204  and  208  in  FIG. 2  (both formed from PE foam) is stronger than the adhesive bond layer  116  in  FIG. 1 . During manufacture of the sealing member  200 , the PE foam layer  208  is extruded between the upper and lower remaining laminated sheets. 
         [0010]    U.S. Pat. No. 6,866,926, which issued to Joe Smelko et al. on Mar. 15, 2005, includes a “prior art” sealing member  300  which is shown in  FIG. 3  (this Figure corresponds to  FIG. 2  of the &#39;926 patent). The upper layers of the sealing member  300  comprise an upper PET layer  302  (which could be 0.00100″ thick) which is bonded to a lower EVA (ethylene-vinyl acetate) layer  304  (that could be 0.00200″ thick). The lower layers comprise an aluminum foil layer  310  (that could be 0.00100″ thick) that is bonded to a PET layer  312  (which could be 0.00050″ thick) and which in turn is bonded to a hot melt bonding material or adhesive layer  322  (that could be 0.00150″ thick). These upper and lower layers are bonded together by means of the bottom surface of the EVA layer  316  which “is surface treated and bonded to foil layer” (&#39;926 patent, col. 1, lines 37-39), possibly by an adhesive layer  316  similar in function to the layer  116  in  FIG. 1 . A paper release layer  306  lies on top of the aluminum foil layer  310  in the right half of the sealing member  300  and prevents attachment of the upper EVA layer  304  to the lower foil layer  310 . This forms a removal tab to the right. 
         [0011]    With reference to  FIG. 4 , the &#39;926 patent teaches how to improve on the sealing member shown in  FIG. 3  by adding a PE foam layer  408  (which could be 0.00500″ thick) over the upper surface of the aluminum foil layer  410 , as is illustrated in  FIG. 4  (which corresponds to  FIG. 3  of the &#39;926 patent). This PE (polyethylene) foam layer  408  (shown in  FIG. 4 ) is essentially identical in positioning and function to the PE foam layer  208  (shown in  FIG. 2  and described above). The EVA layer  404  is heat bonded to the new PE foam layer  408  in a manner similar to that illustrated in  FIG. 2 , where the PE foam layer  208  is shown heat bonded to the extruded PE foam layer  408 . However, less heating and temperature is required in  FIG. 4  to achieve this bond, since the EVA layer  404  ( FIG. 4 ) softens and bonds at a lower temperature than does the PE foam layer  204  ( FIG. 2 ). A good bond is achieved, since EVA and PE both contain polyethylene. The release strip  406  is made of PET (0.00045″ to 0.00100″ thick) and is coated on its underside with a silicon release coating to prevent the strip  406  from sticking to the PE foam layer  410 . The release strip  406  forms the underside of a tab. 
         [0012]    In the design shown in  FIG. 4 , the tab strength is dependant primarily upon the strength and thickness of the upper PET layer  402 , which is 0.00092″ thick in one embodiment. The EVA layer  404  is reduced in thickness over the land area of the container during the induction sealing process, and this reduces any EVA reinforcing of the tab in that area, which is the area where the tab gets stressed first when it is pulled to remove the sealing member  400 . The EVA layer  404  is also quite soft because of its high vinyl acetate content, and accordingly it does not contribute significantly to tab strength in this design. The EVA layer can also shrink and become even less effective following the inductive heating step which seals the sealing member  400  to a container, as was explained in the description of  FIG. 1 . 
       SUMMARY OF THE INVENTION 
       [0013]    In at least one of its embodiments, the invention relates to a sealing member for a container comprising a heat actuated sealant or adhesive layer for securing the sealing member to a container, a metal foil layer over and covering and adhesively bonded to the heat actuated sealant or adhesive layer, and a polyethylene or polypropylene foam or film layer over and covering and adhesively bonded to the foil layer. In addition, a first PET tab defining layer lies over and covers at least a portion of, but is not adhesively bonded to at least part of that portion of, the polyethylene or polypropylene foam or film layer. Also a polypropylene film layer lies over and covers and is adhesively bonded to both the portion of the polyethylene or polypropylene foam or film layer not covered by the first PET tab defining layer and also to the first PET tab defining layer itself, the bonds being established by an adhesive resin and catalyst chosen to provide a high bonding strength sufficient to hold against a manually generated force. A second PET layer lies over and covers and adhesively bonds to the polypropylene film layer. The first PET tab defining layer and the portions of the propylene film and second PET layers immediately above and adhesively bonded to the first PET tab defining layer serve as a tab to facilitate removal of the sealing member from a container to which it has been adhered. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIGS. 1 through 4  each present a side view of a prior art sealing member having a removal tab structure oriented to face to the right in the Figure. The vertical dimensions are exaggerated and are not drawn in proportion to the actual vertical dimensions of each layer of the sealing member. 
           [0015]      FIG. 5  presents a side view of a sealing member in accordance with an embodiment of the invention having a removal tab structure oriented to face to the right in the Figure. The vertical dimensions are exaggerated and are not drawn in proportion to the actual vertical dimensions of each layer of the sealing member. 
           [0016]      FIG. 6  presents a side view of the sealing member in accordance with an embodiment of the invention that was illustrated in  FIG. 5  and that has a removal tab structure oriented to face to the right in the Figure. The vertical dimensions are exaggerated, but they are drawn in approximate proportion to the actual vertical dimensions of each layer of the sealing member to illustrate the relative thicknesses of the layers. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0017]    An embodiment of the invention is presented in  FIGS. 5 and 6 .  FIG. 5  is provided to facilitate comparing the invention to the prior art designs presented in  FIGS. 1 to 4 .  FIG. 6  contains additional details of the design. The description which follows will refer only to  FIGS. 5 and 6 . The general description of sealing members and their use, presented in the Description of the Related Art portion of this specification, is hereby incorporated by reference into this Detailed Description. 
         [0018]    Referring now to  FIG. 6 , there is shown the details of the layered structure of a sealing member  500  designed in accordance with an embodiment of the present invention. 
         [0019]    The sealing member  500  is formed in two parts: an upper removal tab section  501  and a lower sealing section  503 . The right half of the upper section  501  forms a removal tab  505 , as has been explained. 
         [0020]    The lower sealing section  503  includes three or four layers which are cemented together using 2 to 3 grams standard urethane adhesive. 
         [0021]    Lying at the heart of the lower sealing section  503  is an upper aluminum foil layer  510  which is 0.00100″ thick and which seals the container. Optionally, beneath the layer  510  is a layer  512  that is formed from a 0.00048″ (48 gauge) PET film (polyethylene terephthalate film—MELINEX 800C). This optional layer  512  forms a good gas barrier and a fair moisture barrier, but its primary purpose is not to act as a sealing layer but to prevent chemicals such as acidic components that have the ability to corrode aluminum from coming into contact with the aluminum foil layer  510 . The PET film layer  512  prevents any acidic substances within the container from corroding the aluminum foil layer  510 . 
         [0022]    A hot melt bonding material or adhesive layer  522  is placed below the PET film layer  512 , if present, or beneath the aluminum foil layer  510  if the layer  512  is not present. The adhesive layer  522  is 0.00150″ thick, and it may be placed around the peripheral edge of the PET layer  512  where the PET layer comes in contact with the mouth of the container (not shown). The heat activated hot melt bonding material or adhesive layer  522  was obtained from New England Extrusion (Turner Falls, Mass.). The layer  522  is a 0.00150″ thick co-extruded blown sealant film. Variations of this film may be as thick as 0.00300″. The layer  522  may be composed of layers of MDPE/LDPE/18%Eva (35/45/20-70/30 HDPE/LDPE outer, 80/20 core). The layer  522  is specifically designed and chosen to seal to polyethylene and polypropylene containers. The exact composition may vary, and similar co-extruded films can be manufactured as blown films obtained from other vendors using various polymer compositions. Other suppliers of similar co-extruded films include Pliant and Imaflex. The material chosen is dependent upon the composition of the container. 
         [0023]    Another option is to purchase an extrusion or solvent heat seal coated with polyester film from suppliers such as DuPont (MYLAR CL or OL) or Toray (XL4, XL5). These films can act both as the adhesive layer  522  and as a substitute for the PET layer  512 , thus eliminating the need of providing the separate PET layer  512  to protect the aluminum foil layer from corrosion. 
         [0024]    Another possible heat activated adhesive is an ionomer that softens as it is heated such as SURLYN (trademark) of E. I. DuPont DeNemours &amp; Company. Many other suitable heat activated adhesives are known to those skilled in the art. 
         [0025]    Above the aluminum foil layer  510  there is a polyethylene film layer  508  that is 0.00250″ thick (Imaflex—70% HDPE). This layer could also be formed from polyethylene foam. In this design, this layer can be thinner than it has been customary to make this layer in prior art designs, since there is no EVA layer that is more sensitive to high temperatures than the remaining layers. But this layer must still contribute to insulation of heat generated during the inductively-induced heating of the aluminum foil to bond the sealing member  500  to a container, preventing as much as possible of that heat from reaching the upper removable tab section  501  of the sealing member  500 . 
         [0026]    The upper removable tab section  501  contains three layers. Lying at the heart of the section  503  is a PP or polypropylene film layer  504  that is 0.00300″ thick (clear New England Extrusion polypropylene blown film C328 grade). This layer  504 , among other things, adds insulation properties to the overall structure, reducing heat transfer to the inner area of the sealing member  500 . The PP layer  504  is sandwiched in between an upper PET (polyethylene terephthalate) layer  502  that is 0.00092″ thick (92 gauge—Toray PA10 or DuPont LBT) and a lower PET tab layer  506  that is 0.00048″ thick (48 gauge). The PP layer  502  extends over the entire upper surface of the section  503 , as is shown. The PET tab  506 , on the other hand, only extends over about half of the tab  505  part of the sealing section  503  and thus defines the size and the extent of the liftable tab  505 . In  FIGS. 5 and 6 , the PET tab  506  is shown extending over the right side, or tab  505  side, of the section  503 , and it extends from the right side only to the center of the section  503 . Variations in the size and shape of the PET tab  506  are, of course, permissible and desirable, as is illustrated in  FIGS. 6 ,  7 , and  8  and the accompanying text of U.S. Pat. No. 5,514,442 cited above. 
         [0027]    The bond  514  between the PET layer  502  and the PP layer  504  is formed from the same adhesive that is used in the bonds  518 ,  520  and  521  (2 or 3 grams standard urethane adhesive). 
         [0028]    The upper removable tab section  501  and the lower sealing section  503  are bonded together by an adhesive  516  carefully selected to give the maximum possible strength to this bond. This adhesive is a two-part urethane adhesive system. It must produce a bond value of 3500 g/in, and most advantageously a bond value of 4000 g/in or above. COIM NOVACOTE 250A adhesive resin was chosen and was treated with COIM NOVACOTE 375S catalyst. COIM NOVACOTE 253 adhesive has also been used, again with the 375S catalyst. Adhesives with similar characteristics could be produced by other adhesive manufacturers. 
         [0029]    Note in  FIG. 6  that in the left half of the sealing member  500 , the adhesive layer  516  bonds the upper removable tab section  501  directly to the lower sealing section  503 . It does this by bonding the PP layer  504  directly to the PE layer  508  over the left half of the width of the sealing member  500 . In the right half of the sealing member  500 , the adhesive layer  516  bonds the PP layer  504  to the PET tab  506 , rather than to the PE layer  508 . The lower surface of the PET tab  506  is not bonded to the PE film  508 . Accordingly, the right half of the removable tab section  501  is formed into the lifting tab  505 , comprising the right half of the PP film layer  504  sandwiched between the two PET layers  502  and  506 . The tab  505  so formed may be pulled up and used to remove the entire sealing member  500  from the container. In this design, both the outer PET film layer  502  and the PP film layer  504  jointly contribute to the strength of the connection formed between the tab  505  and the remainder of the sealing member  500 . The strength of adhesive layer  516  insures a strong bond between the upper removable tab section  501  and the lower sealing section  503  of the sealing member  500 . The high melt point of the PE foam or film layer  508  preserves the integrity of this layer, while its insulative characteristics protect the upper layers from heat damage, and the higher melt point characteristics of the PP film layer  504  (in comparison to the melt point characteristics of the EVA layer  404 —FIG.  4 —used in earlier designs) contributes to both the strength and the stability of the removable tab section. 
         [0030]    While  FIGS. 5 and 6  and the detailed description presented above illustrate a particular embodiment of the invention, those skilled in the art will recognize that modifications and variations will also fall within the scope of the invention. For example, the thicknesses of the various layers may be varied. The PET film layer  502  can be 0.00092″ (92 gauge), 0.00048″ (48 gauge), or 0.00044″ (48 gauge), for example, and can be constructed from DuPont LBT or DuPont 800C or Toray PA10. The polypropylene film layer  504  may range in thickness from 0.00200″ (2.0 mil) to 0.00600″ (6.0 mil) thick, for example, dependent upon the overall desired thickness of the structure. It is a monolayer polypropylene blown film supplied by New England Extrusions. It can also be a co-extruded film composed of HDPE and polypropylene, or it can be another polyethylene or foam layer of similar thickness. 
         [0031]    Other materials may be substituted for those shown in  FIGS. 5 and 6 . For example, the PET film  502  and the PET tab  506  may be DuPont MELINEX 800C or Toray PA10. The polyethylene film or foam layer  508  could be polyethylene film with a thickness ranging from 0.00200″ to 0.00600″ or polypropylene film or a co-extruded film comprised of both polyethylene and polypropylene. This material can be replaced with polyethylene foam or polypropylene foam from 0.00300″ to 0.00900″ thick. As this material is an insulating or heat distribution layer, the melt point of the material is important. A polyethylene film or foam blend advantageously may be composed of 70% HDPE blended with MDPE. By controlling the melt point of this layer it is possible to insure that the polymer will not melt upon induction sealing and will not squeeze out and melt to the inside of the closure, resulting in high sealing member removal torques. The melt point of the film or foam should be at least 125 degrees Celsius and above.