EP0639139A4

EP0639139A4 - Moulded container.

Info

Publication number: EP0639139A4
Application number: EP93911680A
Authority: EP
Inventors: Alex Ong; John Mammoliti; Ross Chiodo
Original assignee: Visy Board Properties Pty Ltd; Visy Board Pty Ltd
Current assignee: Visy Board Properties Pty Ltd; Visy Board Pty Ltd
Priority date: 1992-05-08
Filing date: 1993-05-03
Publication date: 1997-01-29
Also published as: NZ252645A; JPH08504705A; EP0639139A1; CA2135280A1; WO1993023294A1

Abstract

A moulded tray comprising a blank of single-face corrugated board having a liner element (L) and a corrugated element (C) moulded to define a base (1), an upstanding side wall (2) and an outwardly directed rim (3), the base (1) and side wall (2) and the side wall (2) and the rim (3) being connected by smoothly radiussed regions (4 and 5) whereby the currugated element (C) substantially retains its integrity in the radiussed regions to thereby provide a moulded tray having increased rigidity.

Description

MOULDED CONTAINER Field of the Invention

This invention relates to moulded containers suitable for supporting for display and containing food and other products. The invention finds application in a wide range of containers, including moulded trays for food products such as meats, cakes and various forms of so-called fast-foods, and lidded containers suitable for food products such as hamburgers, pizzas and all other forms of fast-foods.

Background of the Invention

Food products such as meats, cakes etc. are usually displayed in supermarkets on shallow trays covered by a plastic film. The most widely used tray is the moulded polystyrene foam tray which is durable and may be manufactured at relatively low cost. Similarly, containers having integrally hinged or separate lids are also moulded from polystyrene foam and are widely used to package fast-foods such as hamburgers.

Moulded polystyrene foam trays and containers are being increasingly criticized for their impact on pollution of the environment and their lack of recyclability. However, until the present invention, few if any practical alternatives of comparable cost have been developed by the packaging industry. For example, moulded trays and integrally hinged lidded containers, such as hamburger cartons, have been made from so- called box board, but such trays and containers are prohibitively expensive when made from sufficiently rigid box board materials. When made from lighter box board materials, the trays and containers have insufficient strength to provide an acceptable alternative to the polystyrene foam products.

Single-face corrugated board is widely used in the packaging industry as a cushioning material. It is not traditionally used to form cartons or boxes, although proposals have been made in AU-B-30298/63 (277947) to use modified single-face corrugated board for this purpose, and in AU-B-44160/64 (284298) to use multi-ply wound single-face board to form tubular containers. Neither of these proposals has found commercial acceptance due to the greater strength and more widely accepted use of standard (double-face) corrugated board in the packaging industry. It has never been proposed to make moulded containers or trays from single-face corrugated board, the expectation being that it would not be possible to form moulded containers and trays from such material. It has been surprisingly found by the present applicant that by moulding single-face corrugated board in a particular configuration, containers and trays are able to be moulded in a manner which retains its shape for the typical life of such a product and provides a product having acceptable strength properties.

Summary of the invention

The invention provides a moulded container or tray suitable for food products, comprising a blank of single-face corrugated board having a liner element and a corrugated element moulded to define a base, an upstanding side wall and a rim, characterized by smoothly radiussed regions between the base and said side wall said corrugated element substantially retaining its integrity in said radiussed regions to provide a moulded container or tray of the required rigidity.

By moulding the container or tray from single-face corrugated board and maintaining, by means of the smoothly radiussed regions, the integrity of the corrugations in the corrugated element of the board except at the corners where deformation must occur to shape the product, a product having equivalent or superior rigidity when compared with a moulded polystyrene foam product is produced with none of the environmental disadvantages associated with moulded polystyrene foam products.

The container or tray is preferably moulded from single-face corrugated board which has been coated to increase its water and heat resistance and to further increase its rigidity and to retain its moulded shape, although advantage may be gained by coating only the corrugated element. Various acrylic or modified cryϋc resins known in the packaging industry may be used for this purpose and have the advantage that they are biodegradable and approved for use in the food industry.

In one preferred embodiment described in greater detail below, the invention finds application as a food product tray. However, the invention is equally applicable to other moulded containers, such as hamburger and pizza containers having integrally hinged lids and shaped in the nature of a so-called clam shell container.

The invention further provides a method of forming a moulded container or tray comprising the steps of forming a shaped blank from single-face corrugated board having a liner element and a corrugated element, moulding the blank under heat and pressure to form a moulded container or tray having a base, an upstanding side wall and rim, said moulding being performed to provide smoothly radiussed regions between the base and the side wall to maintain the integrity of the corrugated element in these regions to thereby form a moulded container or tray having the required rigidity.

In a preferred form of the invention, the single face corrugated board is preferably made from paper which has been treated to increase its resistance to moisture and heat and increases the rigidity of the moulded product. A suitable coating comprises any one of numerous acrylic or modified acrylic resins used in the packaging industry.

Brief description of the drawings

In the accompanying drawings:

Figure 1 is a perspective view of a moulded tray embodying the invention;

Figure 2 is a plan view of the moulded tray, and

Figure 3 is a side elevation showing a half section through the corrugations.

Description of preferred embodiment

Referring to the drawings, a moulded tray embodying the invention is seen to comprise a base portion 1, a side portion 2 and a rim portion 3, with the base and side portions 1 and 2 connected by a smoothly radiussed portion 4 and the side portion and rim portion 2 and 3 connected by a further smoothly radiussed portion 5. The tray is moulded from a shaped blank of single- face corrugated board having a liner medium M and a corrugated medium C, with the corrugations directed inwardly of the tray. By moulding the tray with smoothly radiussed portions 4 and 5, the integrity of the corrugations of the corrugated medium C in these regions is substantially maintained thereby producing a moulded product having superior rigidity.

The blank is creased in the regions which will be occupied by the corners of the moulded tray to reduce cracking of the board in these regions and to promote retention of the moulded shape. The creases are clearly visible in figures 1 and 3 of the drawings.

To increase the resistance to moisture and heat of the moulded tray and to further increase the rigidity of the tray, the single face board is preferably coated with an acrylic resin or a modified acrylic resin of the type commonly used in the packaging industry. The coating is most conveniently performed on the paper medium which subsequently defines the liner and the corrugated medium in the single face board blank. By modified acrylic resin is intended acrylic resins to which a cross linking agent known in the art has been added to increase the hardness of the resultant coating, or modified base resins, such as styrenated acrylic resins.

The moulding process is performed under heat and pressure, and to reduce the likelihood of cracks developing in the corrugated board product, the blank should have a moisture content substantially falling in the range eight to ten per cent. Generous clearances are maintained between the male and female platens of the moulding die to further ensure the integrity of the corrugations in the corrugated medium C at all regions of the product except at the corners referred to above where the blank is pre-creased to encourage bunching of the material to define the desired shape of the moulded tray.

Coating of the single-face board with a suitable acrylic resin or modified acrylic resin is preferably performed before the liners are corrugated and glued together. The use of a coated product not only improves the retention of the moulded shape and increases the rigidity of the product but also reduces the likelihood of cracking of the board by providing a seal to the exposed paper surface and allowing the paper and coating to soften and flex under the heat and pressure used in the moulding process. After moulding, the coating cools and hardens to maintain the moulded shape and to increase the rigidity of the product.

It will be appreciated from the above that products manufactured in accordance with the invention have the following advantages:

1. They have equivalent or superior strength when compared with moulded polystyrene foam products,

2. They have adequate resistance to moisture and heat,

3. They may be made from recycled materials which are biodegradable and may in turn be recycled.

4. The positioning of the corrugations inside the container reduces food adhesion and increases insulative properties, and may obviate the need for blood absorbing inserts such as are used in the packaging of meat. The ability of the corrugated medium to absorb such liquids may be controlled by modifying the coating applied to the corrugated medium.

Claims

The claims defining the invention are as follows:

1. A moulded container or tray suitable for food products, comprising a blank of single-face corrugated board having a liner element and a corrugated element moulded to define a base, an upstanding side wall and a rim, characterized by smoothly radiussed regions between the base and said side wall, said corrugated element substantially retaining its integrity in said radiussed regions to provide a moulded container or tray of the required rigidity.

2. The container or tray of claim 1, wherein said rim has an outwardly directed portion connected to said side wall by further smoothly radiussed regions.

3. The container or tray of claim 1 or 2, wherein at least said corrugated element has a coating to increase its resistance to moisture and heat and to further increase its rigidity and to retain its moulded shape.

4. The container or tray of claim 3, wherein the coating is a selected acrylic resin coating or a modified acrylic resin coating.

5. The container of any preceding claim, further comprising a lid moulded in a similar form to said container and hinged to said container along part of its rim.

6. A method of forming a moulded container or tray comprising the steps of forming a shaped blank from single-face corrugated board having a liner element and a corrugated element, moulding the blank under heat and pressure to form a moulded container or tray having a base, an upstanding side wall and rim, said moulding being performed to provide smoothly radiussed region between the base and the side wall to maintain the integrity of the corrugated element in these regions to thereby form a moulded container or tray having the required rigidity.

7. The method of claim 6, furthering comprising moulding the blank to form an outwardly directed rim connected to said side wall by further smoothly radiussed regions.

8. The method of claim 6 or 7, further comprising the step of coating at least the corrugated element of said blank to increase its resistance to moisture and heat and to increase the rigidity of the moulded product and to retain its moulded shape.

9. The method of claim 8, wherein the coating is a selected acrylic resin coating or a modified acrylic resin coating.