Cohesive Reclosable Fasteners For Flexible Packages

Abstract

A flexible package having a reclosable fastener with opposing front and back panels joined together to form a cavity. The reclosable fastener including opposing cohesive layers supplied from a solvent dispersion of a thermoplastic elastomer and diluent disposed on each of the front and back panels effective to form a reclosable fastener having a cohesive peel strength less than the bond strength to the front and back panels.

1 . A flexible package having a reclosable fastener comprising:
 opposing front and back panels joined together to form a cavity;   a reclosable fastener including opposing cohesive layers supplied from a solvent solution of a blend of a thermoplastic elastomer and a diluent resin disposed on each of the front and back panels, the cohesive layers being positioned facing each other on the front and back panels so that the flexible package can be closed when the opposing cohesive layers contact each other; and   a bond strength of the cohesive layers to the panels greater than a cohesive bond strength between opposing cohesive layers so that the front and back panels can be repeatedly peeled open without substantially delaminating the cohesive layers from the front and back panels.   
   
   
       2 . The flexible package of  claim 1 , wherein the cohesive layers include a major amount of the thermoplastic elastomer including a styrenic block copolymer or a mixture of styrenic block copolymers diluted with a minor amount of the diluent resin including ethylene vinyl acetate copolymer to form the cohesive bond strength. 
   
   
       3 . The flexible package of  claim 2 , wherein the cohesive layers include about 7 to about 9 parts of the thermoplastic elastomer and about 0.5 to about 2 parts of the ethylene vinyl acetate copolymer. 
   
   
       4 . The flexible package of  claim 2 , wherein the styrenic block copolymer is selected from the group consisting of SIS block copolymers based on styrene and isoprene, SBS block copolymers based on styrene and butadiene, SEBS block copolymers with a hydrogenated midblock of styrene-ethylene/butylenes-styrene, SEPS block copolymers with a hydrogenated midblock of styrene-ethylene/propylene-styrene, and mixtures thereof. 
   
   
       5 . The flexible package of  claim 1 , wherein the cohesive bond strength is about 100 to about 700 g/inch with a residual cohesion bond strength after contamination about 25 to about 100 percent of the cohesion bond strength before contamination. 
   
   
       6 . The flexible package of  claim 5 , wherein the cohesive layer has a tack level not exceeding about 5 psi when preloaded with about 4.5 pounds and not exceeding about 15 psi when preloaded with about 10 pounds. 
   
   
       7 . The flexible package of  claim 6 , wherein the cohesive layer has a peel strength to the panels of greater than about 700 g/inch. 
   
   
       8 . The flexible package of  claim 1 , wherein the front and back panels are selected from the group consisting of ethylene vinyl acetate, polyethylene, polypropylene, polybutylene, nylon, polyethylene terephthalate, polyvinyl chloride, ethylene vinyl alcohol, polyvinylidene chloride, polyvinyl alcohol, polystyrene, or combinations thereof. 
   
   
       9 . The flexible package of  claim 8 , wherein the front and back panels contain ethylene vinyl acetate in at least their innermost surfaces. 
   
   
       10 . The flexible package of  claim 1 , wherein at least the innermost surfaces of the front and back panels include less than about 10 percent of a filler therein. 
   
   
       11 . The flexible package of  claim 10 , wherein the filler is selected from micro- or nano-sized inorganic materials. 
   
   
       12 . The flexible package of  claim 11 , wherein the filler includes clay, calcium carbonate, montmorillonite, dolomite, talc, mica, and mixtures thereof. 
   
   
       13 . The flexible package of  claim 1 , wherein the front and back panels includes less than about 700 parts per million fatty acid amide or other additives that can migrate to the panel surface and decrease the bond strength to the cohesive layers. 
   
   
       14 . The flexible package of  claim 1 , wherein the solvent is an organic solvent selected from the group consisting of ethyl acetate, normal propyl acetate, isopropyl acetate, methyl ethyl ketone, ethyl alcohol, normal propyl alcohol, propylene glycol, normal propyl ether, butyl acetate, toluene, cyclohexane, cyclohexanol, and mixtures thereof. 
   
   
       15 . The flexible package of  claim 1 , wherein the reclosable fastener has less than about 50 parts per million residual organic solvent. 
   
   
       16 . A reclosable fastener suitable for a package, the reclosable fastener comprising:
 a cohesive layer applied to a flexible film and having an exposed cohesive surface; and   a non-adhesive spacer layer having an outer surface and disposed adjacent the cohesive layer, the non-adhesive spacer layer protruding outwardly beyond the cohesive surface of the cohesive layer so that the cohesive surface is recessed from the outer surface of the adjacent non-adhesive spacer layer.   
   
   
       17 . The reclosable fastener of  claim 16 , wherein the adjacent non-adhesive spacer layer includes a pair of non-adhesive spacer layers each positioned adjacent a lateral side of the cohesive layer. 
   
   
       18 . The reclosable fastener of  claim 17 , wherein each of the pair of adjacent non-adhesive spacer layers are disposed on the cohesive surface of the cohesive layer. 
   
   
       19 . The reclosable fastener of  claim 17 , wherein each of the pair of adjacent non-adhesive spacer layers are disposed on the flexible film. 
   
   
       20 . The reclosable fastener of  claim 16 , wherein the adjacent non-adhesive spacer layer includes a polyamide, polyester, polyethylene, polypropylene, polybutylene, ethylene vinyl acetate, polyethylene terephthalate, ethylene vinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polystyrene, and combinations thereof. 
   
   
       21 . The reclosable fastener of  claim 16 , wherein the cohesive layer includes a thermoplastic elastomer and a diluting resin. 
   
   
       22 . The reclosable fastener of  claim 21 , wherein the thermoplastic elastomer is a compound including a styrenic block copolymer or a mixture of styrenic block copolymers and the diluting resin is ethylene vinyl acetate. 
   
   
       23 . The reclosable fastener of  claim 22 , wherein the compound includes minor amounts of plasticizers, fillers, antioxidants, or mixtures thereof. 
   
   
       24 . The reclosable fastener of  claim 22 , wherein the styrenic block copolymer is selected from the group consisting of SIS block copolymers based on styrene and isoprene, SBS block copolymers based on styrene and butadiene, SEBS block copolymers with a hydrogenated midblock of styrene-ethylene/butylenes-styrene, SEPS block copolymers with a hydrogenated midblock of styrene-ethylene/propylene-styrene, and mixtures thereof. 
   
   
       25 . The reclosable fastener of  claim 16 , wherein the cohesive surface has a cohesive bond strength of about 100 g/inch to about 700 g/inch. 
   
   
       26 . The reclosable fastener of  claim 25 , wherein the cohesive surface has a tack level not exceeding about 5 psi when preloaded with about 4.5 pounds and not exceeding about 15 psi when preloaded with about 10 pounds. 
   
   
       27 . The reclosable fastener of  claim 16 , wherein a gap of about 2.5 to about 50 microns is formed between the outer surface of the adjacent non-adhesive spacer layer and the cohesive surface of the cohesive layer. 
   
   
       28 . The reclosable fastener of  claim 16 , further comprising opposing first and second reclosable fasteners, the cohesive surface of the first reclosable fastener opposing the cohesive surface of the second reclosable fastener. 
   
   
       29 . A flexible package having a reclosable fastener, the flexible package comprising:
 opposing front and back panels; and   a reclosable fastener on each of the front and back panels, each reclosable fastener including a cohesive layer disposed on the panel and having an outer surface spaced a first distance from the panel, a non-adhesive layer adjacent the cohesive layer and having an outer surface spaced a second distance greater than the first distance from the panel so that the cohesive layer is substantially recessed from the outer surface of the non-adhesive layer, and at least a portion of the outer surfaces of the cohesive layers cohesively engaged to each other to form a closed package.   
   
   
       30 . The flexible container of  claim 29 , wherein the first distance the outer surface of the cohesive layer is spaced from the panel is about 2.5 to about 50 microns. 
   
   
       31 . The flexible container of  claim 29 , wherein the second distance the outer surface of the non-adhesive layer is spaced from the panel is about 2.5 to about 100 microns. 
   
   
       32 . The reclosable fastener of  claim 29 , wherein the non-adhesive layer is disposed on the outer surface of the cohesive layer. 
   
   
       33 . The reclosable fastener of  claim 29 , wherein the non-adhesive layer is disposed on the panel. 
   
   
       34 . The reclosable fastener of  claim 33 , wherein the thickness of the cohesive layer is about 2.5 to about 50 microns and the thickness of the non-adhesive layer is about 5 to about 100 microns. 
   
   
       35 . The reclosable fastener of  claim 29 , wherein the non-adhesive layer includes a polyolefin, polyamide, polyester, polyethylene, polypropylene, polybutylene, ethylene vinyl acetate, polyethylene terephthalate, polyvinyl chloride, ethylene vinyl alcohol, polyvinylidene chloride, polyvinyl alcohol, polystyrene, and combinations thereof. 
   
   
       36 . The reclosable fastener of  claim 29 , wherein the cohesive layer includes a thermoplastic elastomer or a mixture of thermoplastic elastomers selected from the group consisting of a styrenic block copolymer or a mixture of styrenic block copolymers. 
   
   
       37 . The flexible container of  claim 29 , wherein the cohesive layer has a cohesive bond strength of about 100 g/inch to about 700 g/inch. 
   
   
       38 . The flexible container of  claim 37 , wherein the cohesive layer has a tack level not exceeding about 5 psi when preloaded with about 4.5 pounds and not exceeding about 15 psi when preloaded with about 10 pounds. 
   
   
       39 . A method of forming a flexible package having a reclosable fastener, the method comprising:
 moving a flexible film longitudinally in a machine direction;   applying first and second strips of a thermoplastic elastomer containing solution intermittently to the flexible sheet and transverse to the machine direction, the first and second strips being spaced a first gap along the machine direction;   applying a third strip of the thermoplastic elastomer containing solution intermittently to the flexible sheet and parallel to one of the first and second strips, the third strip being spaced a second gap smaller than the first gap from one of the first or second strips;   applying a strip of a polyolefin solution adjacent to each of the intermittent thermoplastic elastomer strips in a manner such that an outer surface of a dried thermoplastic elastomer strip is recessed from an outer surface of a dried polyolefin strip; and   drying the thermoplastic elastomer strips and the polyolefin strips.   
   
   
       40 . The method of  claim 39 , further comprising forming the flexible film into the flexible package such that one of the intermittent thermoplastic elastomer strips faces another of the intermittent thermoplastic elastomer strips to form the reclosable fastener. 
   
   
       41 . The method of  claim 39 , wherein a percent solids of the thermoplastic elastomer containing solution is less than the percent solids of the polyolefin solution so that the dried thermoplastic elastomer strip has a smaller thickness than the dried adjacent polyolefin strip. 
   
   
       42 . The method of  claim 41 , wherein the thermoplastic elastomer containing solution has a percent solids ranging from about 25 to about 45 percent. 
   
   
       43 . The method of  claim 42 , wherein the polyolefin solution has a percent solids ranging from about 45 to about 65 percent. 
   
   
       44 . The method of  claim 29 , wherein the non-adhesive layer is applied to the outer surface of the cohesive layer. 
   
   
       45 . The method of  claim 29 , wherein the non-adhesive layer is applied to the flexible film. 
   
   
       46 . A method of forming a flexible package having a reclosable fastener, the method comprising:
 moving a flexible film longitudinally in a machine direction;   applying first and second strips of a thermoplastic elastomer containing solution intermittently to the flexible sheet and transverse to the machine direction, the first and second strips being spaced a first gap along the machine direction;   applying a third strip of the thermoplastic elastomer containing solution intermittently to the flexible sheet and parallel to one of the first and second strips; and   drying the thermoplastic elastomer strips to form the reclosable fastener.   
   
   
       47 . The method of  claim 46 , wherein the thermoplastic elastomer containing solution includes about 25 to about 45 percent solids solution of a styrenic block copolymer and a secondary resin in an organic solvent.