Easily openable container lid with resealability and method of producing the same

Abstract

An easily unsealable container closure having re-sealing performance and comprising a closure member having an opening portion that has been formed in advance, and an unsealing tab which is so fitted to the outer surface side of the closure member as to cover the opening portion and is hermetically adhered to the periphery of the opening portion, wherein the unsealing tab includes a flexible tab member and a plug member integrally adhered to the tab member and is so formed as to be fitted to the opening portion of the closure member, and the flexible tab member is hermetically fixed to the periphery of the opening portion in the closure member so as to be torn off. The container closure offers re-sealing performance which can be repetitively effected to temporarily seal again the once unsealed opening, and further offers excellent re-sealing performance, unseal indication function and easy-to-unseal performance.

1 . An easily unsealable container closure having re-sealing performance and comprising a closure member having an opening portion that has been formed in advance, and an unsealing tab which is so fitted to the outer surface side of said closure member as to cover said opening portion and is hermetically adhered to the periphery of the opening portion, wherein said unsealing tab includes a flexible tab member and a plug member integrally adhered to said tab member and is so formed as to be fitted to the opening portion of said closure member, and said flexible tab member is hermetically fixed to the periphery of the opening portion in said closure member so as to be torn off.  
   
   
       2 . A container closure according to  claim 1 , wherein the edge of said opening portion is treated by being folded or curled toward the outer side of the closure or by being coated with a coating material or a resin.  
   
   
       3 . A container closure according to  claim 1 , wherein said flexible tab member comprises a laminate obtained by forming a resin film on both surfaces of a metal foil.  
   
   
       4 . A container closure according to  claim 3 , wherein said laminate comprises a biaxially drawn polyethylene terephthalate layer/an aluminum layer/a sealant film, the layers being dry-laminated by using an urethane adhesive.  
   
   
       5 . A container closure according to  claim 1 , wherein said closure member is made of a metal member having double seamed portions along the peripheral edge thereof.  
   
   
       6 . A container closure according to  claim 1 , wherein the outer surface side of said closure member can be at least heat-adhered to said flexible tab member, but the inner surface side thereof adheres to neither the flexible tab member nor to the plug member.  
   
   
       7 . A container closure according to  claim 1 , wherein not only said flexible tab member but also the plug member are adhered to the periphery of the opening of said closure member.  
   
   
       8 . A container closure according to  claim 1 , wherein said unsealing tab has a portion firmly adhered to the closure member in a manner that it can be torn off with difficulty at a position on the side opposite to the unsealing start end with said opening portion held therebetween, and the unsealing tab is not torn off from the closure member even after the unsealing.  
   
   
       9 . A container closure according to  claim 8 , wherein said unsealing tab is cut away at a portion just before the portion that is firmly adhered to said closure member from both sides thereof in a direction nearly at right angles with the tearing direction to assume such a shape that the tab width is narrowed at the above portion.  
   
   
       10 . A container closure according to  claim 1 , wherein said flexible tab member is adhered and fixed to the outer surface side of said closure member, and includes a sealing portion to which the plug member is adhered integrally together and a folding portion continuing to the sealing portion at a sealing start end of said sealing portion, said folding portion having a grip portion for unsealing and being fixed to the sealing portion or to the closure member before being unsealed.  
   
   
       11 . A container closure according to  claim 10 , wherein said folding portion is adhered and fixed to the sealing portion or to the outer surface of the closure member except at least said grip portion and, after unsealed, the folding portion is prevented from being fixed again to the sealing portion or to the closure member.  
   
   
       12 . A container closure according to  claim 11 , wherein said folding portion that is adhered and fixed to the sealing portion or to the outer surface of the closure member is torn off thereby to tear off part of the folding portion or the sealing portion.  
   
   
       13 . A container closure according to  claim 11 , wherein said flexible tab member has an adhesive layer formed on the surface thereof on the side that is adhered to the closure member, and the end of the folding portion is folded or curled toward the side of the closure member so as to be adhered and fixed.  
   
   
       14 . A container closure according to  claim 1 , wherein said flexible tab member is adhered and fixed to the closure member, and the end of the periphery of the opening portion is folded toward the side of the closure member.  
   
   
       15 . A container closure according to  claim 14 , wherein said flexible tab member has an adhesive layer formed on only the surface thereof that comes in contact with the closure member.  
   
   
       16 . A container closure according to  claim 10 , wherein a vent hole is formed in advance in said closure member, said folding portion is adhered and fixed to the outer surface side of the closure member so as to seal at least said vent hole, and when said folding portion is torn off from the side of the outer surface of the closure member, the vent hole is opened earlier than the opening portion.  
   
   
       17 . A container closure according to  claim 10 , wherein the adhesion between the sealing portion and the closure member are torn off or are weakened near both ends of the folding line which is a boundary line between the sealing portion and the folding portion of said flexible tab member prior to pulling said plug member from the opening portion.  
   
   
       18 . A container closure according to  claim 17 , wherein said flexible tab member has the sealing portion and the folding portion that are adhered and fixed together near both ends of the folding line.  
   
   
       19 . A container closure according to  claim 1 , wherein said plug member is a plastic plug member formed by the injection forming or the compression forming, or is a metal plug member formed by the press forming.  
   
   
       20 . A container closure according to  claim 19 , wherein said plastic plug member is made of a resin composition of an olefin resin and at least the one selected from a thermoplastic elastomer and a rubbery composition, having a heptane elution amount at 25° C. of not larger than 150 ppm, a deformation ratio (JIS K 6723) at 100° C. of smaller than 30%, and a compressive permanent strain (JIS K 6262) at 70° C. of in a range of 50 to 95%.  
   
   
       21 . A container closure according to  claim 20 , wherein the olefin resin component in the resin composition constituting said plug member is at least the one selected from the copolymerized resin obtained by copolymerizing a polyethylene resin, a polypropylene resin and an ethylene or a propylene with a small amount of other olefin.  
   
   
       22 . A container closure according to  claim 20 , wherein the thermoplastic elastomer component and the rubbery composition component in the resin composition constituting said plug member are blended compositions of one or two or more kinds of those selected from an ethylene/α-olefin copolymer rubber, ethylene/propylene/diene copolymer rubber, ethylene/vinyl acetate copolymer rubber, acid-modified ethylene/vinyl acetate copolymer rubber, styrene/isoprene block copolymer rubber, styrene/butadiene/styrene block copolymer rubber, styrene/ethylene/butylene/styrene block copolymer rubber, styrene/ethylene/propylene/styrene block copolymer rubber, hydrogenated styrene/butadiene/styrene block copolymer rubber, hydrogenated styrene/ethylene/butylene/styrene block copolymer rubber, hydrogenated styrene/ethylene/butylene/styrene block copolymer rubber, hydrogenated styrene/ethylene/propylene/styrene block copolymer rubber, silicon rubber, silane-crosslinked polyethylene, silane-crosslinked polypropylene, and silicane-crosslinked ethylene/vinyl acetate copolymer rubber.  
   
   
       23 . A container closure according to  claim 20 , wherein the α-olefin component in said ethylene/α-olefin copolymer rubber is at least the one selected from propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene and 1-dodecene.  
   
   
       24 . A container closure according to  claim 20 , wherein said plug member is a resin composition obtained by mixing three kinds of polymers which are a polyethylene resin or a polypropylene resin, an ethylene/α-olefin copolymer rubber and a styrene/ethylene/butylene/styrene block copolymer rubber or a hydrogenated product thereof or a styrene/ethylene/propylene/styrene block copolymer rubber or a hydrogenated product thereof.  
   
   
       25 . A container closure according to  claim 20 , wherein the hardness at normal temperature of the resin composition constituting said plug member is in a range of 80 to 95 as measured by using a type-A durometer indentater and is in a range of 50 to 75 as measured by using a type-D durometer indentater in compliance with a cured rubber permanent strain testing method (JIS K 6262).  
   
   
       26 . A method of producing an easily unsealable container closure comprising the steps of treating an edge of an opening of a closure member having the opening portion that has been formed in advance, forming an unsealing tab by integrating a flexible tab member and a plug member together, and adhering the flexible tab member to the outer surface of the closure member in the periphery of the opening by applying said unsealing tab onto the surface that becomes the outer surface side of the closure member.  
   
   
       27 . A production method according to  claim 26 , wherein said unsealing tab is formed by integrally forming the plug member by the injection forming or by the compression forming on the flexible tab member.  
   
   
       28 . A method of producing an easily unsealable container closure comprising the steps of treating an edge of an opening of a closure member having the opening portion that has been formed in advance, forming a flexible tab member and a plug member, and placing said flexible tab member and the plug member on the outer surface of the closure member such that the plug member is fitted to the opening of the closure member and the flexible tab member covers the plug member, enabling the flexible tab member and the plug member to be integrally adhered together thereby to form an unsealing tab and, at the same time, adhering the flexible tab member to the outer surface of the closure member.