CA2070255A1 - Container sealing - Google Patents

Container sealing

Info

Publication number
CA2070255A1
CA2070255A1 CA002070255A CA2070255A CA2070255A1 CA 2070255 A1 CA2070255 A1 CA 2070255A1 CA 002070255 A CA002070255 A CA 002070255A CA 2070255 A CA2070255 A CA 2070255A CA 2070255 A1 CA2070255 A1 CA 2070255A1
Authority
CA
Canada
Prior art keywords
container
closure member
sealant
container body
composition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002070255A
Other languages
French (fr)
Inventor
Robert W. Fox
Eric H. White
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shell Canada Ltd
Original Assignee
Robert W. Fox
Eric H. White
Shell Canada Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert W. Fox, Eric H. White, Shell Canada Limited filed Critical Robert W. Fox
Publication of CA2070255A1 publication Critical patent/CA2070255A1/en
Abandoned legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B65CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65DCONTAINERS 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
    • B65D77/00Packages formed by enclosing articles or materials in preformed containers, e.g. boxes, cartons, sacks or bags
    • B65D77/10Container closures formed after filling
    • B65D77/20Container closures formed after filling by applying separate lids or covers, i.e. flexible membrane or foil-like covers
    • B65D77/2024Container closures formed after filling by applying separate lids or covers, i.e. flexible membrane or foil-like covers the cover being welded or adhered to the container
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21DWORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D51/00Making hollow objects
    • B21D51/16Making hollow objects characterised by the use of the objects
    • B21D51/38Making inlet or outlet arrangements of cans, tins, baths, bottles, or other vessels; Making can ends; Making closures
    • B21D51/44Making closures, e.g. caps
    • B21D51/46Placing sealings or sealing material

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
  • Closures For Containers (AREA)
  • Rigid Containers With Two Or More Constituent Elements (AREA)

Abstract

ABSTRACT

CONTAINER SEALING

A sealed container comprises a container body, an end closure member and a sealant therebetween, in which the sealant is bonded to the body and to the closure member by a bond having a peel/bond strength (as herein defined) of at least 30 Newtons.
A strong bond of this type can be obtained by providing an end closure member which carried a composition that can be activated indirectly, e.g. by induction-heating, to form a sealant bonded to the closure member and also to the container body.

Description

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CONTAINER SEALING

This invention relates to the sealing of containers, and in particular to the material that is used to provide a seal between a container body and an end closure, as well as to a process for forming a seal.
Much research has gone into the problem of providing a secure seal between containers and corresponding end closures. A seal must be formed between these two components after the container is ~0 filled with, say, a beverage or microwavable food. It is of course important to ensure that the contents of the sealed container do not leak out, and also to prevent bacteriological or other contamination of the contents from the ambient atmosphere.
The container may be of metal or plastic material. The closure member is usually of metal. It will often include a ring-pull or other frangible portion, in order to allow ready access to the contents.
~0 It is conventional to crimp or otherwise form the end closure onto a flange at the open end of the container, and to provide a sealant composition between the two components. Metal cans formed in this way are described in, for example, US-A-3403813, 2 ~

US-A-3774560, US-A-3882763 and US-A-4089283; reference to these specifications will show various forms, and procedures for forming, container-closure seals.
In US-A-3403813, the sealant is atactic amorphous polypropylene; it states that this material has viscosity characteristics such that it provides a permanently tacky sealant between the can end and can body. In US-A-3774560, an expandable foam seam-sealing compound is used, which expands, on 10 heating, to fill voids that may be present in the seam area.
Despite these various proposals, sealed containers of the type described suffer from various disadvantages. Firstly, it is difficult to fill all 15 the voids that may be formed during sealing, especially when the two components are respectively of metal and plastics. Secondly, the compressive force that is applied when bringing the two components into contact leads to the possibility of buckling of 20 relatively weak containers, e.g. of plastics.
Thirdly, the stress imposed by the forming of the respective components at the area of sealing means that multi-layer plastics materials may delaminate during seaming, when the curl overlap between 25 container and closure takes place.
According to a first aspect of the present invention, in a sealed container comprising a container body, an end closure member and a sealant therebetween, the sealant is bonded to the body and to 30 the closure me~ber by a bond having a peel/bond strength of at least 30, e.g. up to 50, 75, 100 or more, Newtons, by a flat seal peel test which involves flat-sealing a 15 mm wide strip of coated aluminium to a 15 mm wide strip of polypropylene, as used in a 2 ~3 7 ~ 2 ~ r~

container; the samples are then peeled apart at an angle of 180 and at a speed of -100 mm/min.
According to a second aspect of the present invention, an end closure member, of the type suitable for sealing to a container body, carries a composition that can be activated indirectly to form a sealant bonded to the closure member and also to a container body.
According to a third aspect of the present invention, a method for producing a sealed container comprises seaming a container body and an end closure member with an indirectly-activatable composition therebetween, and activating the composition so that it forms bonds to the closure member and to the container body.
The present invention is based on the utility of a strong bond between the container body and the sealant, and between the sealant and the end closure.
This is in contrast to the previous use of materials 20 which have various properties but are designed primarily to prevent the passage of contaminants in and/or contents out. Further, by contrast with the known system of treating a sealant composition to foam it in situ, the present invention can involve the use Of an activatable material to form the desired bond.
The effect of the strong bond is to provide several important advantages to products and processes of the present invention. Firstly, the burst strength of the sealed container is enhanced. Secondly, the fact that a strong bond can be formed with plastics material indirectly means that little compressive force is needed when bringing the components together;
the system is therefore as useful for plastics as metal containers. Thirdly, the sealant fixes the relative positions of the components in the sealed 2 ~7 container and resists the forces that are built in during crimping; this is a particular advantage when using plastics laminates that are liable to delaminate. By creating a weld between the materials, the strength of the finished seam will be increased even if delamination has taken place during seaming.
Unlike unsealed containers, further delamination will be restricted and therefore a much stronger and higher integrity container will result.
In general terms, the nature of the container body and closure member may be conventional. The container will usually be provided with a flange at its open end, to facilitate the contact between the components. The closure member may be formed with a ring-pull or other frangible portion.
The components may be combined in conventional manner, e.g. using chucks and rolls to press the components together. A hermetic joint is formed by interlocking the edges to both the closure and container components. The joint is generally produced in two operations, a sealing compound having already been introduced between the other components, e.g. by forming a layer thereof on the closure member. The first operation forms a metal/plastic or metal/metal curl/overlap, while the second operation flattens them to produce the required seam. This operation may be followed, if necessary or desired, by activation of the sealant, e.g. by induction heating, to a temperature of, ay, 150 to 200C.
Examples of sealant materials than can be used in the invention include the following:
Polymers that can be extruded onto aluminium or steel sheet: these include polypropylene, polyethylene and polybutylene;
Morprime-based systems;

2~7a2~

Polyolefinic resins: these are mainly modified ethylene acrylates (trade names include Admer, Modic and Bynel);
PE-CTFE;
PE-TFE;
PTFE;
EVA;
MAA:
EAA;
Ionomers: and Modylene P/A (carboxylic acid-modified PP).
By way of example, the invention will be described below in connection with a plastics or polypropylene container and a metal or aluminium end closure, although steel is an alternative metal, and of course the invention is applicable to metal container-metal end systems.
As already indicated, a Morprime/polypropylene or other material can be applied to one of the metal or plastics components, and most suitably to a metal closure member. It can be applied as a lacquer, by way of replacement for a conventional epoxy lacquer.
A primary aim of the lacquer i8 to provide a, say, polypropylene/aluminium weld in the area of the double seam, and to provide protection of aluminium from attack by acids, e.g. in the container contents.
A suitable lacquer may comprise a dispersion of modified polypropylene or other polymer in a blend of high boiling solvents. The polypropylene can be 30 blended with epoxy resins to provide excellent adhesion to aluminium and steel and can be used to make high strength laminations to polypropylene.
The sealant may be applied in an overall coating process. Alternatively, the sealant may be applied selectively. For example, a heat-sealing material may 2~7~2~

be applied only to the flange overlap area on the aluminium or other closure member.
In either case, bonding between a polypropylene flange and an aluminium end can be formed indireGtly.
For example, fusion is crea~ed by passing the seamed container through an induction field. The energy can be focused on the area of overlap by coil design, causing the aluminium to heat, and resulting in the lacquer melting and fusing to the polypropylene.
Conventional contact heating systems or ultrasonics could create the same effect as induction sealing. An important advantage of induction sealing is that the time taken to create the bond is very short, and will therefore not significantly affect 15 existing canning line speeds. Other suitable heating systems include sonic welding, induction welding, radio-freguency welding, conduction welding, spin-welding and impulse sealing.
In addition to the advantages described above, 20 the present invention may allow greater potential for the reduction of problems associated with reverse seam wrinkles. It may also provide wider seaming operating windows. All these advantages and effects can be achieved without any significant reduction of 25 conventional double-seaming line speeds with a heat-sealing system.
The following Example illustrates the invention.

ExamPle Aluminium sheet was hand-coated with a Morprime lacquer. The Morprime lacquer basically consists of an epoxy lacquer containing a polypropylene suspension. The lacquer was applied as a thin film and cured to the surface in an oven.

2~2~

The sheets were converted to ends and seamed onto 30 cm. diameter containers, and induction-sealed using a system supplied by Stanelco.
For testing, the containers were split into two groups. One group was tested without retorting, and the other group was retorted at 121C and then tested.
The containers were tested by assessing their burst strength. The burst test involves introducing compressed air into the container in a controlled manner, and recording the pressure needed to rupture the pack's seal.
The results of the burst tests are given below:

Unretorted Containers _ Conventional Induction-double-seamed sealed -1st OP seam only very low 193 kPa .
2nd OP seam131 kPa 234 kPa Retorted Containers -Conventional Induction-double-seamed sealed 1st OP seam only very low 213 kPa 2nd OP seam124 kPa 207 kPa _ These results show that the induction-sealed containers not only possess a burst strength twice that of conventionally-seamed containers, but also possess equivalent bond strengths when only seamed with the first operation (OP) seaming roll.

2~702~

In the flat seal peel test described above, results of 30-40 Newtons have been obtained by operation in accordance with the invention.

Claims (9)

1. A sealed container comprising a container body, an end closure member and a sealant therebetween, in which the sealant is bonded to the body and to the closure member by a bond having a peel/bond strength (as herein defined) of at least 30 Newtons.
2. A container according to claim 1, in which the container body and the end closure member are each of metal.
3. A container according to claim 1, in which the container body is of plastics and the end closure member is of metal.
4. A container according to claim 1, 2 or 3, in which the sealant comprises polypropylene.
5. An end closure member, of the type suitable for sealing to a container body, which carried a composition that can be activated indirectly to form a sealant bonded to the closure member and also to a container body.
6. A member according to claim 5, in which the sealant comprises polypropylene.
7. A member according to claim 5 to 6, in which the composition can be activated by induction-heating.
8. A method for producing a sealed container, which comprises seaming a container body and an end closure member with an indirectly-activatable composition therebetween, and activating the composition so that it forms bonds to the closure member and to the container body.
9. A method according to claim 8, in which the composition is activated by induction-heating.
CA002070255A 1991-06-03 1992-06-02 Container sealing Abandoned CA2070255A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9111873.7 1991-06-03
GB919111873A GB9111873D0 (en) 1991-06-03 1991-06-03 Container sealing

Publications (1)

Publication Number Publication Date
CA2070255A1 true CA2070255A1 (en) 1992-12-04

Family

ID=10695986

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002070255A Abandoned CA2070255A1 (en) 1991-06-03 1992-06-02 Container sealing

Country Status (7)

Country Link
EP (1) EP0518411A1 (en)
JP (1) JPH05213360A (en)
AU (1) AU1720892A (en)
CA (1) CA2070255A1 (en)
GB (1) GB9111873D0 (en)
IE (1) IE921692A1 (en)
ZA (1) ZA923837B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4239894A1 (en) * 1992-11-29 1994-06-01 Ucb Transpac Nv Gastight vacuum pack for coffee, cocoa, nuts, etc - comprises inner and outer envelopes laminated together with adhesive in such a way that delamination occurs when pack is opened
ES2377333T3 (en) 2006-12-20 2012-03-26 Selig Sealing Products, Inc. Stratified

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2994455A (en) * 1959-08-05 1961-08-01 Gen Mills Inc Metallic containers
GB2064468B (en) * 1979-12-08 1984-10-10 Metal Box Co Ltd Container seams
US4526290A (en) * 1983-10-19 1985-07-02 Ball Corporation Flanged container

Also Published As

Publication number Publication date
ZA923837B (en) 1993-11-26
JPH05213360A (en) 1993-08-24
EP0518411A1 (en) 1992-12-16
IE921692A1 (en) 1992-12-16
GB9111873D0 (en) 1991-07-24
AU1720892A (en) 1992-12-10

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Legal Events

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