Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/76—Making non-permanent or releasable joints
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
  • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
  • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
  • B29C65/3604—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
  • B29C65/3656—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint being a layer of a multilayer part to be joined, e.g. for joining plastic-metal laminates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/01—General aspects dealing with the joint area or with the area to be joined
  • B29C66/05—Particular design of joint configurations
  • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
  • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
  • B29C66/112—Single lapped joints
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/01—General aspects dealing with the joint area or with the area to be joined
  • B29C66/05—Particular design of joint configurations
  • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
  • B29C66/13—Single flanged joints; Fin-type joints; Single hem joints; Edge joints; Interpenetrating fingered joints; Other specific particular designs of joint cross-sections not provided for in groups B29C66/11 - B29C66/12
  • B29C66/131—Single flanged joints, i.e. one of the parts to be joined being rigid and flanged in the joint area
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/01—General aspects dealing with the joint area or with the area to be joined
  • B29C66/05—Particular design of joint configurations
  • B29C66/20—Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines
  • B29C66/24—Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines said joint lines being closed or non-straight
  • B29C66/242—Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines said joint lines being closed or non-straight said joint lines being closed, i.e. forming closed contours
  • B29C66/2422—Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines said joint lines being closed or non-straight said joint lines being closed, i.e. forming closed contours being circular, oval or elliptical
  • B29C66/24221—Particular design of joint configurations particular design of the joint lines, e.g. of the weld lines said joint lines being closed or non-straight said joint lines being closed, i.e. forming closed contours being circular, oval or elliptical being circular
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
  • B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
  • B29C66/53—Joining single elements to tubular articles, hollow articles or bars
  • B29C66/534—Joining single elements to open ends of tubular or hollow articles or to the ends of bars
  • B29C66/5346—Joining single elements to open ends of tubular or hollow articles or to the ends of bars said single elements being substantially flat
  • B29C66/53461—Joining single elements to open ends of tubular or hollow articles or to the ends of bars said single elements being substantially flat joining substantially flat covers and/or substantially flat bottoms to open ends of container bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
  • B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
  • B29C66/54—Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles
  • B29C66/542—Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles joining hollow covers or hollow bottoms to open ends of container bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
  • B29C66/61—Joining from or joining on the inside
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D77/00—Packages formed by enclosing articles or materials in preformed containers, e.g. boxes, cartons, sacks or bags
  • B65D77/22—Details
  • B65D77/30—Opening or contents-removing devices added or incorporated during filling or closing of containers
  • B65D77/38—Weakened closure seams
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
  • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/01—General aspects dealing with the joint area or with the area to be joined
  • B29C66/05—Particular design of joint configurations
  • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
  • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
  • B29C66/112—Single lapped joints
  • B29C66/1122—Single lap to lap joints, i.e. overlap joints
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/71—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C66/00—General aspects of processes or apparatus for joining preformed parts
  • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
  • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
  • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
  • B29C66/7234—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer
  • B29C66/72341—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer for gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
  • B29K2023/04—Polymers of ethylene
  • B29K2023/08—Copolymers of ethylene
  • B29K2023/083—EVA, i.e. ethylene vinyl acetate copolymer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
  • B29K2023/10—Polymers of propylene
  • B29K2023/12—PP, i.e. polypropylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2705/00—Use of metals, their alloys or their compounds, for preformed parts, e.g. for inserts
  • B29K2705/02—Aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2009/00—Layered products
  • B29L2009/003—Layered products comprising a metal layer

Definitions

• This invention relates to heat sealed closures employing multi-phase polymer blends. More particularly, it relates to closures providing a peel-away lid such as disclosed in the above-identified patent application, and in U.S. Patent Nos. 3,946,872, 4,890,758, 5,069,355 and 5,125,528.
• Patent No. 5,125,528 discloses flexible end panels which are heat sealed to end rings during the molding process of the end rings. The end rings are then applied to the opening of a pack ⁇ age. The lids in this patent are removed by tearing along pre- imprinted score lines.
• the prior art additionally discloses adhesively bonding the flexible lid to a container rim or to an end panel which is then affixed to the container with the lid being torn off at the adhe ⁇ sive, rupturing it during the process.
• the pre-scored systems do not provide any indication of the integrity of the seal achieved between the flexible lid and the end panel or lip of the container.
• the containers employing defoliation either are complicated to assemble or do not provide for precise defoliation at the seal, and again, none of these systems provide a means for easily testing the integrity of the seals of the flexible lid to the end panel or rim of the container.
• multi-phase polymer blends are utilized in either the flexible lid or an end panel to which the lid is heat-sealed.
• the first of the polymers employed has an affinity for the material to which it is to be heat sealed during the heat-sealing process.
• the second polymer is chosen such that it moves away from the surface being heat sealed and forms a region adjacent to the heat seal in which the second polymer predominates.
• the two polymers are chosen such that the second polymer concentration forms a weakened portion such that upon opening the container, the sealed surface of the polymer blend pulls away from the concentrated portion adjacent the seal in a controlled fashion, depositing a rather precise thickness layer of the first polymer onto the lid, or the end panel, or the con ⁇ tainer lip to which the multi-polymer blend has been heat sealed.
• I employ a blend of polypropylene and poly ⁇ ethylene where the polypropylene is sealed to a polypropylene or metal surface.
• the polypropylene concentrates at the heat seal and displaces the polyethylene which concentrates adjacent the heat seal and provides the weakened portion.
• a polar polymer is added such as ethylene vinyl acetate and the polypropylene is treated with maleic anhydride so that it will bond to the metal.
• the invention contemplates the use of other incompatible polymer mixtures such as polypropylene and nylon, styrene and polyethylene, polyethyleneterephthalate (PET) or PETG and poly- propylene.
• incompatible polymer mixtures such as polypropylene and nylon, styrene and polyethylene, polyethyleneterephthalate (PET) or PETG and poly- propylene.
• PET polyethyleneterephthalate
• PET polyethyleneterephthalate
• PET polyethyleneterephthalate
• poly- propylene any incompatible mixture wherein a first component selectively diffuses to the seal and forms a stronger bond there than the cohesion of the second component or its adhesion to the first component is within the invention.
• Another object of the invention is to provide such closures providing a unique telltale when opened, showing that they have been completely sealed to the container or to a frame member or end panel attached to the container.
• Still another object of the invention is to provide such closures that may be applied directly to metal and plastic by heat sealing.
• Still another object of the invention is to provide such closures of the type disclosed in the above-identified U.S. Pat ⁇ ent Application and U.S. Patent No. 5,125,528.
• the invention accordingly comprises the features of con ⁇ struction, elements, and arrangements of parts, articles of manu ⁇ facture possessing the features, properties and relations of elements, and several steps and the relation of one or more of said steps with respect to each of the others, and possessing the characteristics, properties, and the relations of components which will be exemplified in the article, constructions and meth ⁇ ods hereinafter described.
• the scope of the invention will be indicated in the claims.
• FIGURE 1 is a top view of a container closure according to my invention
• FIGURE 2 is a partial cross-sectional and diagrammatic view taken along line 2-2 of Figure 1 ;
• FIGURE 3 is a cross-sectional view of a mold in which a solid polymer ring, according to the invention, is molded and heat sealed to a peelable lid;
• FIGURE 4 is a diagrammatic partial cross-sectional view of a heat seal according to the invention.
• FIGURE 5 is a cross-sectional view, partially cut away of a closure, according to my invention, applied to a prior art con ⁇ tainer having a plastic sealing surface;
• FIGURE 6 is a cross-sectional view, partially cut away of a lid, according to my invention, applied to a container having a metallic surface.
• a closure according to the in ⁇ vention, is generally indicated at 20. It comprises a ring por ⁇ tion 22, and a lid portion 24.
• the lid portion 24 is provided with a ring pull 26, which may be temporarily affixed to the lid portion 24 at heat seals 28.
• the lid portion 24 is sealed against the ring portion 22, at a heat seal indicated at 30.
• the ring part 22 is provided with a annuler portion generally indicated at 32 for sealing to a metal can of aluminum of tinned steel. This is preferably accomplished by means of induction heating of the metal can.
• the ring portion 22 is provided with an upstanding portion, generally indicated at 34, which provides for stacking of the cans after the ring por ⁇ tion 22 is applied to the cans.
• Ribs, 36 are provided so that the assembled closures 20 may be stacked before application to the cans.
• the ring part 22 when the ring part 22 is injec ⁇ tion-molded against the lid part 24 of the two incompatible poly ⁇ mers forming the ring part 22, concentrates under the seal 30, as generally indicated at 38, and the other component polymer con ⁇ centrates at portion 40, indicated below portion 38.
• the rela ⁇ tive sizes of the portions 38 and 40 to the parts 22 and 24, are greatly exaggerated in FIGURE 2 for the purpose of illustrating same.
• the portion 38 has a high proportion of the polymer which strongly seals to the bottom surface of part 24 with an adhesion which is either greater than the cohesion of the portion 40 wherein the second polymer component of ring 22 is concentrated or the adhesion at interface between portions 38 and 40.
• the ring 22 is injection-molded against the lid 24 in a mold 42 shown in FIGURE 3.
• the injection molding process In order to allow for the migration and concentration of the polymer component having the greatest affinity for the lid 24 onto the portion 38 under the lid (see FIGURE 2) , the injection molding process must be such that it does not stir the two compo ⁇ nents together during the flow of the plastic melt of the ring 22 within the mold 42. I have found that laminar flow is required of the liquid plastic melt in the mold 22 so that mixing of the portions 38 and 40 does not occur, which would destroy the integ ⁇ rity of the telltale portion 38.
• the lid 24 in many instances, is comprised of multiple layers of polymer mate ⁇ rials providing vapor, gas barriers, etc. As more fully pointed out below, I prefer that the lower surface 44 of the lid 24, be of the same plastic material as that component of the ring 22 which migrates and concentrates in the telltale portion 38.
• plastic parts 46 and 48 are shown which have been heat-sealed together in an area under the arrow 50 in the conventional manner. Again, shown exaggerated in size, a portion 52 adjacent the interface 54 between parts 46 and 48 contains a concentration of the polymer having the greatest affinity for part 48 and a surrounding higher concentration indicated at 56 of the other polymer comprising part 46.
• the other polymer or the interface between the other polymer and the polymer having a higher concentration in portion 52 is weaker and when parts 46 and 48 are peeled apart, the portion 52 will stick to part 48, providing a telltale.
• a lid, generally indicated at 58 is heat sealed to a metal can, generally indicated at 60.
• the metal can comprises, for example, a 4 mil aluminium portion 62 to which polypropylene has been applied in a 2 mil layer, as indicated at 64.
• the peelable lid 58 comprises an upper portion 66 which may be one or more layers provide vapor barrier, gas barrier, strength, etc. to the lid 58.
• the lower surface layer 68 comprises polypropylene and another incompatible polymer such as polyethylene, in accordance with the invention.
• the lid 58 is sealed to the can body 60 as generally indicated at 70. In accordance with the invention, when the lid 58 is peeled away from the can body 60, a portion of the lower surface of the layer 68 will remain adhered to the polypropylene layer 64 at the seal 72.
• a peelable lid may be directly heat- sealed to a can body 76 of metal, either by heat-sealing or by induction heating of the can body 76, by spin sealing, by ultra sonic sealing, or the like.
• the lid 74 is again formed of upper layers, generally indicated at 78, appropriate for the use of the container, and a lower surface layer 80 of two incompatible plas ⁇ tics, one of which has an affinity for the can 76 during heat sealing or during induction heating of the can 76, again forming a concentrated layer 82 which will remain adhered to the can 76 when the lid 74 is peeled away.
• the following composition of materials for the ring part 22 is preferred. It consists essentially, by weight, of about 30% polypropylene copolymer, about 36% polypro ⁇ pylene homopolymer, about 9% low density polyethylene, about 15% high-density polyethylene, about 9% ethylene vinyl acetate and about 1% green color concentrate.
• the part 22 has a nice appear ⁇ ance and provides a telltale that contrasts nicely with a white polypropylene lid surface.
• the homo- and co-polymer polypro ⁇ pylene has been reacted with maleic anhydride.
• the concentration of maleic anhydride in the total mixture is less than .8% the FDA limit, in the range of about .2 to about .4% and preferably about ** (&
• the polypropylene layer 68 which seals to the polypropylene layer 64 on the can 60 and leaves a telltale thereon when peeled away, two compositions work well.
• the preferred one consists essentially, by weight, of about 8.75% ethylene vinyl acetate, about 15% high density poly ⁇ ethylene, about 8.75% low density polyethylene, about 40% poly ⁇ propylene homo-polymer, and about 27.5% polypropylene co-polymer.
• Another consists essentially, by weight, of about 7% ethylene vinyl acetate, 13.5% high density polyethylene, about 7% low- density polyethylene, about 35% polypropylene homo-polymer and about 37.5% polypropylene co-polymer.
• the latter formula is a little harder to peel, but provides a stronger seal. A minor amount of colorant and filler may be added as desired.
• Sheet material of either of these latter compositions may be directly sealed to a can body 76 as shown in FIGURE 6, by re ⁇ acting the polypropylene with maleic anhydride prior to mixing.
• the polypropylene layer surface 44 of the lid 24 in FIGURES 1 and 2 may be polypropylene co-polymer supplied by Exxon Chem ⁇ ical Company as Escorene ⁇ PD7341N.
• the polypropylene that has wet the polypropylene surface is cohesively bonded thereto with a stronger bond than either exists in the volume of higher concentration of EVA and polyeth ⁇ ylene or at the interface between this concentration and the polypropylene adhered to the surface 44.
• the formulas given above provide a telltale layer of poly ⁇ propylene which is preferably colored, on the surface of the peeled-away lid 24, which has a thickness of about _ mil.
• the EVA synergistically cooperates with the maleated polypropylene .
• the EVA remains attached to the metal when the seal is broken, thus providing a telltale that a hermetic seal has been achieved.
• maleated polypropylene itself exhibits fair adhe ⁇ sion to metal
• an elastic polymer to the mixture reduced the stress between the metal and the maleated polypropylene. Since this material (ethylene vinyl acetate) is also polar, it accelerates the bonding of the maleated polypro ⁇ pylene to the metal and provides good adhesion.
• an excel ⁇ lent compromise may be achieved between the need for the polypro ⁇ pylene to be treated at a high temperature during canning and to be perhaps kept in cold storage or left out in the cold during winter transportation.
• the co-polymer contains a rubber such as ethylene propylene rubber (EPR) .
• Polyethylene is excellent for this purpose since it reduces the cohesive strength of the material and causes the peel value to drop, as does the ethylene vinyl acetate. The proportions are adjusted to achieve the appropriate peel value.
• High density polyethylene stiffens the plastic, and this makes it more stable at high temperatures, while low density polyethylene makes it more flexible.
• the ratio is adjusted ap-monttely for the intended use.
• the ethylene vinyl acetate When the ethylene vinyl acetate is blended with the maleated polypropylene, the ethylene vinyl acetate tends to gather around the maleic anhydride groups. When the material is melted and comes in contact with a metal surface, the ethylene vinyl acetate wets the polar surface and the anhydride and the carboxy groups react with the metal surface to form a chemical bond. When the metal and the material is cooled, the shrinkage of the plastic creates tension on the bond and tries to dislodge the bond. The presence of ethylene vinyl acetate because of its resilience, minimizes the tension on the bond. Additionally, the rubber, such as ethylene propylene rubber which is present in the poly ⁇ propylene co-polymer, improves the bond by minimizing the stresses on the bond. Other rubbers, such as polyisobutalin or polybutadyene can be used in addition to ethylene vinyl acetate or in place of it, to improve the adhesion.
• polar polymers containing ethylene besides ethylene vinyl acetate could be used, such as ethylene acrylic acid or ethylene methacrylic acid.
• RUNS 1-20 are suitable for the ring 22 in Figures 1 and 2.
• RUN 21 is suitable for the lid surface 68 in Figure 5.
• (H) indicates homo-polymer.
• the rest of the identification of type is the identification used by the supplier.
• compositions of the invention comprise about 50% to 80% of a first polymer, preferably polypropylene, of about 20% to about 50% of a second polymer, preferably polyethylene, and about 10% of polymers comprising ethylene and acetate groups.
• the polypropylene comprises from about 20% to about 80% polypro ⁇ pylene homo-polymers.
• the composition comprises up to about 40% low-density polyethylene and up to about 40% high-density poly ⁇ propylene.
• ingredients or compounds recited in the singular are intended to include compatible mixtures of such ingredients wherever the sense permits .
• ring as used in the following claims, I mean any closed loop of material of a shape conforming to the shape of the package body to which it is to be affixed.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Closures For Containers (AREA)

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• 1994
  • 1994-01-31 EP EP94911374A patent/EP0680447A4/de not_active Withdrawn
  • 1994-01-31 AU AU63914/94A patent/AU6391494A/en not_active Abandoned
  • 1994-01-31 WO PCT/US1994/001122 patent/WO1994016963A1/en not_active Ceased

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