Closure membranes

Details Closure membranes Closure membranes

1999-06-09

2001-02-06

Newhouse, Nathan J. (Department: 3727)

Receptacles

Closures

Removable closure retained by adhesive or fusion means

C220S364000, C220S373000, C383S103000, C053S425000, C428S137000

Reexamination Certificate

active

06182850

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a closure membrane for containers which comprises an outer film and inner film with a joining layer between these two films and a sealing seam zone.
2. Background Art
It is known to place substances, for example foodstuffs, in containers and to seal off beaker-type containers with a lid such as a closure membrane, or to seal off pouches by folding and sealing. Closure membranes may e.g. be made of papers, metal foils or plastic films, or laminates of several of the same or different metals, plastics and papers. The purpose of the closure membrane is to tightly seal the container in order to prevent ingredients of the contents escaping or preventing substances from outside entering the container. There are cases in which it is undesirable to have the container completely sealed by the closure membrane, this in order to allow the pressure in the interior of the container to adjust to that of the surrounding atmosphere. This concerns in particular cases in which the contents are placed in the container, the container is sealed, and the lidded container is subjected to a thermal treatment, such as, pasteurization, sterilization or ultrapasteurization. The intention is to prevent a positive pressure forming in the container that could cause the closure membrane to tear or rupture. This can be avoided by only partially sealing the closure membrane after filling the container, and allowing substances to escape at the non-sealed region between the edge of the container and the closure membrane. Subsequently, in another stage of the process, the closure membrane is then completely sealed onto the container.
In another version, described in EP-B 0 156 404, an opening for adjusting the pressure inside the container is provided on the container; after the thermal treatment, this opening is hermetically sealed by a polymer compound which melts on application of heat. This version, however, suffers the disadvantage that the polymer compound that can be melted is situated at an exposed area which is not protected from abrasion, and the opening for compensating for pressure differences provides a direct connection between the interior of the container and the surroundings.
BROAD DESCRIPTION OF THE INVENTION
The object of the present invention is to propose a closure membrane for a container or pouch which enables a container or pouch to be sealed in a sealing or other type of closing operation and enables the thermal treatment to be performed without substantial pressure on the lidded pouch or container, whereby the parts that create the valve effect are arranged such that they are protected from mechanical influence.
That objective is achieved by way of the invention in that within the sealing seam zone at least one space free of a bonding layer is provided within the sealing seam zone between the outer film and the inner film, and within this non-bonded space the outer film features at least one opening and the inner film features at least one opening, and a reservoir of material that softens under the influence of heat is provided in the non-bonded space between the outer film and the inner film, whereby the openings in the inner film and the openings in the outer film are connected for passage of a fluid, and the openings are closed by application of heat to the closure membrane as a result of softening of the material that softens on application of heat.
DETAILED DESCRIPTION OF THE INVENTION
The outer film may be a monofilm or a composite laminate film such that the outer film of a membrane film faces outwards. The inner film may be a monofilm or a composite laminate film such that the inner film of a membrane film faces towards the interior of the container.
Various materials may be employed for the outer and inner films. For example use may be made of monofilms or laminates containing thermoplastics e.g. polyolefins such as polyethylenes or polypropylenes, polyesters such as polyalkylene-terephthalates and in particular polyethylene-terephthalate, polyvinylchloride, polycarbonates or polyamides. Further materials in film form for the inner and outer films are cellophane, metal foils such as aluminium or steel foils or papers such as coated or impregnated papers. Use may also be made of foiltype laminates or composites made up of various materials such as metal foils and plastic films, plastic films and paper or paper, plastic films and metal foils. Suitable for the outer films and in particular for the inner films are thermoplastics and coextruded polyethylenes or cast polypropylene. These plastic films are sealable. The sealable plastic films may also form a laminate or composite along with other materials. For example, coextruded polyethylene or cast polypropylene may be arranged on a substrate film. Suitable substrate films may be in the form of monofilms or composite films from the above mentioned thermoplastics. It is also possible to achieve the sealing characteristic of the closure membrane by providing a sealable organic coating or sealable thermoplastic on the surface of the inner film. In order to achieve sealing properties with aluminium foils, paper or cellophane, a coextruded plastic film may e.g. laminate coated onto the material in question.
Preferred examples of outer films are films and laminated containing or comprising polyesters, polyolefins such as polypropylenes or polyethylenes, polyamides, cellophane, aluminium foils and papers. Further examples are sealable films or films of cast polypropylene or coextruded polyethylenes.
The outer films in particular may be provided with a printed image, a graphic design or embossing etc. A printed image may be deposited on the outside or it may be deposited as a counter image on transparent or translucent films or laminates—or it may be made by a combination of direct printing and counter printing.
Preferred sealing layers are films or films of cast polypropylene or coextruded polyethylenes laminate coated onto the inner film, or it may be foils or films of coextruded plastics on aluminium, paper or cellophane, or it may be an organic sealing coating.
The outer and/or the inner films may, as required, contain a barrier layer to prevent passage of gases and vapors such as moisture, active ingredients and aromas, air, oxygen etc. Barrier layers may be e.g. films of EVOH, films containing acrylnitril copolymers or thin i.e. 5 to 500 nanometre thick vacuum deposited ceramic layers e.g. containing silicon oxide and/or aluminium oxide (deposited by chemical or physical vapour deposition) etc.
A joining layer is provided between the outer and inner films. The joining layer is advantageously an adhesive based on water-based adhesives, solvent-containing adhesives, solvent-free adhesives or a single or two component adhesive or a laminating adhesive or a bonding agent.
The adhesives may be of or contain e.g. starches, albumin, casein adhesives, cellulose ethers and cellulose esters such as methylcellulose or nitrocellulose, natural caoutchouc, synthetic caoutchouc, polyethylene, ethylene-vinylacetate copolymers, polypropylene, polyvinylester, such as polyvinylacetate, polyvinylchloride-homopolymers or copolymers such as vinylchloride and vinylacetate or vinylchloride and methacrylic acid ester polymers, polyvinylether, polyvinyl-pyrrolidon, polystyrole, polyesters, polyurethanes, poly-isocyanates, epoxy resins, phenolic resins, resorcin resins such as resorcin-formaldehyde resins and resorcinphenolic-formaldehyde resins, urea formaldehyde resins, melamine-formaldehyde resins and non-reactive resins such as colophonic resins, liquid resins, carbohydrate resins, carbamic acid ester resin or cyclohexanon resins
The adhesives may also container softeners. The adhesives may be solvent-free or may contain solvents such as e.g. benzine, toluol, xylol, methylene-chloride, trichlorethylene, trichlorethane, acetic ester, acetone-methylethyl-ketone, methyl-isobutyl-ketone or cyclohexanon. It is also possible to employ aqueous or water-free adhesives. The adhe

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