The problem to which this invention is directed relates to the difficulty of providing a container for food that has a number of characteristics which make it suitable for particular types of food, in particular environments.

The description itself is in relation to abalone but it is not intended that the food item itself should be necessary restricted to abalone or even crustacean or gastropod varieties or even marine varieties.

BACKGROUND ART A first difficulty is that a container is required to hold food in a preserved status for a substantial period of time.

However, it is more desirable if this time could be longer rather than shorter and in a particular case for instance, in abalone, because of the selling and purchasing season, that preservation could be sustained over a longer than two year period.

A second problem relates to the need for any material to be able to withstand and maintain its shape and desirable characteristics through a period of substantially elevated temperature during which for instance, the food when within the container can be subjected to retort temperatures and pressures.

A third problem is that a container should be able to provide a good view through the material of the container of the food within the container to assist in first external visual examination of the food for an intending purchaser and also for stockists to ensure that the food itself is maintaining its preserved and good quality status. In order for the best customer impression to be gained, the container should be clear and not opaque.

This is of particular importance for high value foods such as abalone, especially where a significant substitution risk is perceived to exist. Buyer confidence is much greater with a transparent container.

A further problem is in relation to the fragility of the material for instance, where this might be from a fragile material such as glass as compared to an alternate, more robust material such as many plastics materials.

Further, it is useful that the container be rigid walled. This improves the retail display characteristics of the container. It also enhances the consumer perception of a high value product.

The challenge has been such that hitherto there has not appeared to be any material which will provide an adequate combination of these characteristics that would provide an answer to the problem.

A solution to the problem is of significant value insofar that this would then provide a desirable container which would provide a long lasting preservation for contained foods which had been previously retorted within the container and which would be visibly viewable through clear or transparent surfaces, would form a rigid sided container and finally not be a fragile material.

DISCLOSURE OF THE INVENTION The discovery of this invention has been that we have found a material which has hitherto not been considered for this particular application and has been found to exhibit a desirable combination of qualities which make it highly suitable for the application.

This is especially the case where the material is moulded as an injection moulded article, and is chosen to have walls of an appropriate thickness to reduce oxygen transmission rates and is able to be closed by engagemerit of a twist or screw top.

Accordingly, in one form of this invention, although this need not necessarily be the only or indeed the broadest form of this, there is proposed a food container having an integral injection moulded body with clear or transparent side wall or walls and bottom and an uppermost screw thread where the plastics material is substantially comprised of polyethylene naphthalate (PEN), and where the wall or walls and bottom are such that the plastics material inhibits oxygen transfer therethrough to

the less than 3 cc/day/m2 at standard atmospheric pressure and 75% relative humidity, said container having a wall thickness not exceeding 4mm.

In preference, the container is a rigid walled container.

In preference, the plastics material after moulding and cooling has been further subject to a maintained temperature in excess of 110 degrees Celsius for a period of at least fifty minutes.

In preference, the wall or walls of the container are of a hollow cylindrical shape.

In reference, there is an outwardly extending collar immediately below the uppermost screw thread.

A method of manufacture of a food container wherein there are included the steps of integrally injection moulding a body of the container with transparent side wall or walls and bottom and an uppermost screw thread from a plastics material being substantially comprised of polyethylene naphthalate (PEN), and subsequently after a cooling of the injected body subjecting the body to a further sustained elevated temperature of at least 110 degrees Celsius for a period of at least fifty minutes.

The PEN material is recommended for use in blow moulding of food containers, but I have discovered that it is suitable for use for producing injection moulded food containers.

In preference, the subjecting of the body to the further elevated temperature occurs with food in a liquid being held within the body during such further step so that the temperature effects a sterilization of the food at the same time.

In a market for high value foods with powerful and trusted brands there is considerable incentive for substitution and counterfeiting. In such a market, a resealable container may be detrimental to a brand owner if it is possible to refill the container, bearing genuine trade marks, with counterfeit product. This is particularly serious if the container itself becomes a trade mark.

Accordingly, it is preferred that a second exposure to retort temperature and pressure should cause distortion of the container, such that a seal cannot be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to drawings wherein: Figure 1 is a perspective view of a container made in accordance with the invention; and Figure 2 is a cross-section view of a container made in accordance with the invention.

BEST MODE FOR CARRYING OUT THE INVENTION Referring to the figures, there is a container 1 with a sidewall 2 defining a cavity 3 adapted to contain food to be preserved. This cavity is a slightly tapered cylinder, closed at one end by a bottom 4 which is integrally formed with the sidewall.

There is a collar 5 extending outward below an upper lip 6 of the container.

Between the collar 5 and the lip 6 there are screw threads 7 integrally moulded into the sidewall. This lip serves to ensure that the lids of containers, when packed, do not contact each other or other adjacent surfaces. Such contact may cause the lids to unscrew during transport.

The screw threads 7 are adapted to engage a lid (not shown) and to hold the lid down against the lip 6 to facilitate a long lasting, airtight closure.

Turning to Figure 2 it can-be seen that the sidewall 2 and integral bottom 4 are approximately of uniform thickness, of about 2 mm. This thickness is chosen to ensure that the requirements of a food container are met. The choice of thickness affects oxygen permeability, which must be less than 3 cc/day/m2 at 75% relative humidity in order to ensure the required two-year shelf life.

Transparency is also affected by wall thickness. Sufficient transparency to meet the requirements for attractiveness to consumers is provided in this embodiment.

The material from which the container is made. is polyethylene naphthalate (PEN).

In particular, in this embodiment, a material manufactured by M&G Polymers USA is used. This is HiPERTUFF 9000 Polyester Resin which is a 2,6 Dimethyl Naphthalate-based polyethylene naphthalate homopolymer resin, although other suppliers are known to exist.

The sidewall 2 is sufficiently robust to survive retorting once, but, in this embodiment, will not to survive a second retorting without distortion. This helps to prevent counterfeit re-use of the container.

The material PEN has further useful characteristics. It will fluoresce under ultra-violet light, thus making its use easy to detect.

The container is formed by injection moulding.

After forming and cooling, the container is then filled with product on a conventional filling line. Any foodstuff may be canned into the container, but it is particularly suited to high value foodstuffs such as abalone.

The filled container then undergoes a retorting process being subject to a maintained temperature in excess of 110 degrees Celsius for a period of at least fifty minutes. The PEN material has the further useful characteristic that such exposure to retorting temperatures improves the visual clarity of the sidewalls.

Should an attempt be made to refill the containers for counterfeit reuse, exposure to retorting temperatures for a second time will cause the container to distort, making it difficult to seal.

Throughout this specification the purpose has been to illustrate the invention and not to limit this.