WO1996028378A1

WO1996028378A1 - Cork closure having a durable liquid impermeable coat so to prevent tainting

Info

Publication number: WO1996028378A1
Application number: PCT/AU1996/000146
Authority: WO
Inventors: George Galloway Dewar
Original assignee: Dewco Investments Pty Ltd
Current assignee: Dewco Investments Pty Ltd
Priority date: 1995-03-16
Filing date: 1996-03-15
Publication date: 1996-09-19
Anticipated expiration: 1997-09-16
Also published as: AUPN177495A0

Abstract

A closure for a container having an opening, comprising a mass of cork wholly or partially encapsulated in at least one durable, liquid-impermeable coat of a coating material(s) so as to isolate any taint-producing agents present in the mass of cork from the contents of the container. The term 'durable, liquid-impermeable coat' refers to coats that are sufficiently enduring to remain liquid-impermeable following sealing insertion of the coated closure into the opening of the container.

Description

CORK CLOSURE HAVING A DURABLE LIQUID IMPERMEABLE COAT SO TO PREVENT TAINTING

This invention relates to closures for containers, particularly wine bottles. 5 Wine bottle closures made from natural cork can be the source of chemicals which may produce mouldy taints in the contents of the bottle. These chemicals (such as trichloroanisoles) may originate from the bleaching process used for cork which involves treatment with chlorine or other chloro compounds and/or oxalic acid. Wine which has been exposed to such 10 chemicals is described as being "corked", and it has been estimated that up to 10% of all bottles of wine sold worldwide may be corked in this manner.

This problem has been exacerbated in recent years due to the increasing use of corks made from agglomerated particles of recycled corks. Whilst having significant cost advantages over "virgin" cork closures, these so-called "agglo" 15 corks appear to have a greater tendency to taint wine, probably, in part, as a result of the glue used.

Consequently, the wine industry is in great need of methods and/or closures which avoid the tainting problems associated with corks. To this end, two alternative closures have been proposed, namely the screw-cap "stelvin" 20 closures and plastic "champagne-style" corks. Whilst these types of closures produce an excellent seal, their use has been limited to low grade wines due to their poor aesthetic qualities.

It is now proposed that cork closures may be encapsulated in a coating material(s) so that the wine is prevented from directly contacting the cork, 25 thereby avoiding the possibility of producing taints.

Accordingly, the present invention provides a closure which may be sealingly inserted into an opening in a container, comprising a mass of cork wholly or partially encapsulated in at least one durable, liquid-impermeable coat of a coating material(s) so as to isolate any taint-producing agents present 30 in said mass of cork from the contents of the container.

With regard to the durable, liquid-impermeable coat, the term "durable" is to be taken to mean that the coat is sufficiently enduring to remain liquid- impermeable following sealing insertion of the closure into the opening of the container. 35 The coating material(s) is preferably selected from the group consisting of polyethylene dispersions, modified polyethylene dispersions and gels of polymers such as ethylene vinyl acetate copolymer (EVA), solutions and dispersions of poly(vinylidene chloride) and its copolymers (e.g. foamed and non-foamed PVC), polyure thanes, acrylic latexes, lacquers and dispersions and various silicones. The coating material may also be selected from "covering" materials such as thermoformed films, particularly tubular thermoformed films. Most preferably, the coating material(s) are selected from the group consisting of PVC's and polyure thanes.

It is clear from the above, that the closures according to the invention may have multiple coats of coating material(s). In such closures, each coating may be the same or different in composition. Including multiple coatings, may also assist in the production of closures having a more uniformly smooth surface (which may enhance the sealing qualities of the closure). Harder coating materials such as some PNDC's and hard acrylics may also be machined using a polishing brush or the like to provide a smooth surface. The PVC's also show low friction qualities which can assist in the insertion and extraction of the closure from the opening of a container. These low friction qualities may also be varied by adjusting the amount and/or kind of plasticiser used or extenders (in the case of polyurethanes).

Standard cork and "agglo" closures are often coated with very thin layers of paraffin wax or silicone to assist insertion and extraction, however, it is clear that these materials and/or the thickness of the coat, are not sufficiently durable to form a liquid-impermeable coat, as tainting problems are still observed.

Very thin layers of paraffin wax and/or silicone may be similarly coated onto the outside of closures according to the present invention in order to assist insertion and extraction.

Where the contents of the container is a food or beverage, the coating material(s) would be selected from those which are "food-contact approved".

The total thickness of the coat(s) may vary depending on the application of the closure from 0.1 to 5.0 mm or more. For wine bottle applications, the total thickness of the coat(s) is preferable 0.2 to 2.0mm, more preferably 0.2 to 0.5mm.

To apply the coating material(s) to the mass of cork, it may be necessary to dry (e.g. by microwave or hot air tumbling) or pre-treat the mass to improve adhesion or incorporation. The pre-treatment(s) may be selected from chlorine treatment, UN treatment and other oxidising treatments. The coating material(s) may be applied onto the mass of cork by dipping, spraying and/or injection moulding.

The coat(s) may only be applied to a portion of the surface of the mass of cork. For example, the coat(s) may only be applied to the face(s) of the closure that is likely to contact the contents of the container.

The cork used in the closure may be sterilised by means of the conventional treatments with chlorine or other-chloro compounds and/or oxalic acid, as well as by other means. Where the closure comprises particles of cork, the individual particles maybe encapsulated in at least one durable, liquid impermeable coats of coating material(s).

Closures according to the invention may be readily adapted to be suitable for sealing openings in many different kinds of containers. However, the closures are primarily intended for use in the wine and spirits industry, and particularly for sealing wine barrels and wine bottles. Accordingly, the closures are hereinafter described in respect to their use in sealing wine bottles.

Depending upon the desired thickness of the coat(s), closures according to the invention for use in sealing wine bottles may be produced using standard cork closures as purchased from a cork supplier. Where thicker coating(s) are required (e.g. 2.0 to 3.0mm) it may be necessary to use corks of reduced diameter otherwise the closure may be too difficult to insert or extract.

Preparation of Coated Cork Closures 1. PNC Plastisol Coatings

Two suitable PNC plastisols are W.R. Grace AD07-2126.3 (which does not foam when heated to 180°C for 5 minutes) and Daraseal 700 (Sicpa) (which foams under these conditions). The coating may be achieved by first pouring plastisol, (7g for 48mm cork length) into a cylindrical aluminium mould, 48mm deep with an internal diameter of 20mm. A cork of 20mm diameter is then lowered carefully into the mould to within 4mm of the bottom. The mould and its contents is then heated in a fast-recovery oven at (180°C for non- foaming and 200°C for foaming) for 5 minutes, followed by cooling before removal of the coated cork. The base of the mould is unscrewed and the cork removed. When the non-foaming PNC is used the coated cork will have a PVC layer approximately 1mm thick around the diameter and 2mm thick at the bottom. When the foamable plastisol is used the foam layer will be approximately 1.5mm thick at the sides and 3-4mm thick at the bottom. The non-foaming plastisol is essentially transparent and light pink in colour so that the cork will be seen inside the coating. The foam layer is white and opaque.

2. Latex Coatings

Cork may be coated in latex (e.g. Glascol C36, Michelman X300) by dipping into a container of latex leaving the top uncoated if desired. The cork is then removed and placed immediately into a fast recovery oven at 105°C for five minutes, then re-immersed in the latex and placed in a fast recovery oven at 95°C for five minutes.

3. Thermoformed Skin Coatings

Corks of 20mm diameter and 48mm length or as required may be covered with a commercial laminating adhesive (e.g. Lamal, Coates Bros, Sydney) and coated by thermoforming a skin of Surlyn (Du Pont plastics) ionomer film around them on a commercial blister packing machine. To prevent creasing of the skin, tubular forms of thermoformed skin may be used.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:-

1. A closure which may be sealingly inserted into an opening in a container, comprising a mass of cork wholly or partially encapsulated in at least one durable, liquid-impermeable coat of a coating material(s) so as to isolate any taint-producing agents present in said mass of cork from the contents of the container.

2. A closure according to claim 1 wherein the coating material(s) is selected from the group consisting of polyethylene dispersions, modified polyethylene dispersions, gels of polymers, solutions and dispersions of poly(vinylidene chloride)(PVC's) and its copolymers, polyurethanes, acrylic latexes, lacquers and dispersions, thermoformed films and silicones.

3. A closure according to claim 2 wherein the coating material(s) is selected from the group consisting of ethylene vinyl acetate, acrylic latexes, PVC's and polyurethanes.

4. A closure according to claim 3 wherein the coating material(s) is selected from the group consisting of PVC's and polyurethanes.

5. A closure according to any one of the preceding claims wherein the mass of cork is wholly or partially encapsulated in multiple durable, liquid- impermeable coats of a coating material(s).

6. A closure according to any one of the preceding claims wherein the mass of cork is wholly encapsulated in said at least one durable, liquid- impermeable coat of a coating material(s).

7. A closure according to any one of the preceding claims wherein the total thickness of the coat(s) is 0.1 to 5.0mm.

8. A closure according to claim 7 wherein the total thickness of the coat(s) is 0.2 to 2.0mm.

9. A closure according to claim 8 wherein the total thickness of the coat(s) is 0.2 to 0.5mm.