AU700323B3 - Improvements in or relating to containers - Google Patents

Description

P:\WPDOCS\DYS\SPECIE\678370.PPD 3/3/98 -1- IMPROVEMENTS IN OR RELATING TO CONTAINERS TECHNICAL FIELD This invention relates to containers and in particular containers used for transportation and storing chilled or frozen foods.

BACKGROUND ART Chilled or frozen foods are commonly packed in insulated containers. In one example expanded foams are commonly used for providing insulation properties. The material however has low impact resistance and is not generally regarded as having sufficient structural integrity for packaging applications and as a result the foam is often protected by an outside box. In addition, expanded foams are not approved for food contact applications and food within such containers consequently needs to be bagged or wrapped.

Metal foils are also used in packaging situations to provide insulation properties.

The use of expanded foam insulation materials in packaging is not regarded as ideal because the material is bulky and in addition there are recognised disposal problems.

Metal foils present manufacturing problems, additional costs, physical properties are not compatible with machinery and standard processing techniques and consequently tend to be used only for smaller higher value items.

As an alternative packaging material, cardboard has good natural insulation qualities, which can be improved if a board is laminated, lamination also improving strength.

It is an object of the present invention to provide a method and apparatus for producing insulated containers with corrugated board as a core material.

P:\WPDOCS\DYS\SPECIE\678370.PPD 3/11198 -2- Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

According to one aspect of the present invention there is provided a method of forming a laminated sheet material comprising the steps of corrugating a paper laminar while applying a plastics metallised liner to one or both sides of the corrugated laminar.

Preferably, the plastic metallised liner is a pre-made laminate of a paper backing with metallised polyester film.

Preferably, the liner includes a bi-axially orientated polyester film which is metallised on one side and corona treated on the other side.

Preferably, the liner is preheated prior to its application to the paper laminar.

Preferably, in one form the liner is heated by heating rollers and adhered to the laminar using a PVA adhesive with the metallised film of the liner outermost.

Preferably, in another form the liner is heated by heating rollers and adhered to the laminar using a PVA adhesive with the metallised film of the liner innermost.

According to another aspect of the present invention there is provided a laminating apparatus including means for feeding out a first laminate and a liner to a set of corrugating rollers the laminar being paper and the liner being a pre-formed laminate of paper and plastic film, the apparatus uniting the laminate and liner subsequent to the corrugation of the paper laminar.

Preferably, the apparatus includes means for preheating the laminar and liner prior to them being fed to the corrugating rollers.

p:\WpDOCS\DYS\SPECIE\67837.PPD 28/9/98 -3- Preferably, the apparatus includes means for feeding a second liner for lamination with the first laminar and the liner.

Preferably, the lamination of the paper laminar and liner with the second liner is subsequent to the lamination of the paper laminar with the liner.

Preferably, the lamination of the paper laminar and the liner with the second liner is achieved with the assistance of a cluster of in-line pressure rollers.

10 Preferably, the second liner is a laminate of a plastics film and paper.

oo The paper used to form the laminate can be of various thicknesses and grades and within the definition of paper it is intended to include thicker semi-rigid paper sheets (cardboard) and recycled and composite sheet materials including cellulose fibres derived from a variety of 15 materials.

BRIEF DESCRIPTION OF DRAWING Aspects of the present invention will be described in relation to the accompanying drawing 20 which is a schematic side view of apparatus in accordance with the present invention set up to produce a two or three ply laminate.

BEST MODES FOR CARRYING OUT THE INVENTION With respect to the drawing a roll of paper 1 is threaded over a heating roller 2 and fed to corrugating rollers 6. Simultaneously a liner material is fed from a roll 4 over a pre-heating roller 5 to the corrugating rollers 6 and laminated to one side of corrugated laminar 7 with the laminar being fed via rollers 8, 9 to nip rollers 10, where (optionally) a liner 11 from a roll 12 is fed via pre-heating roller 13 to the nip rolls 10 to provide a lining to the other side of the laminar. A cluster of crushing and heating rollers 14 are positioned downstream of the nip rollers 10 through which the completed laminar is fed. Downstream of the lamination

I

P:\WPDOCS\DYS\SPECIE\678370.PPD 3/3/98 -4apparatus the completed laminate is stored and cured prior to cutting into box blanks.

Containers can be erected from the box blanks.

The paper 1 can be selected from a range of kraft and recycled papers. The liner film has high gas barrier properties, high reflectivity to light and radiant heat, low permeability to gases and water vapour, it is attractive and decorative, exhibits good abrasion resistance and can be characterised or specified as 1. Thickness, 12 Micron 2. Tensile strength, 29800 kg/mm 2 3. Tear strength 7 MD 4. Coefficient of friction 0.6 (film to film) 5. WVTR g/m 2 /24hr The process of laminating the polyester laminate to any of the kraft liners is a reel to reel process using PVA adhesive, applied at normal room temperature at approximately 70 metres per minute.

Three reels of paper are delivered to the corrugator for loading one or two liners and one laminar.

The metallised side of the kraft liner can be threaded over the pre-heaters with the metallised side facing outwards or inwards (this avoids any likelihood of scuffing the metallised surface).

Care must be taken to avoid scuffing if the inwards method is used.

An ideal corrugating speed is between 90 and 120 metres per minute.

At normal corrugating temperature (130 160 0 C) the board, because of the metallised exterior retains heat from some time, during which time care must be taken when handling the product.

p:\WpDOCS\DYS\SECI\678370.PPD 3/3/98 The converting process (making of a finished box) cannot take place until 24 hours after corrugating. This time is necessary for the curing process i.e. cooling of the board and the moisture balance to finalise.

Whilst it has been know to laminate sheet material such as cardboard with plastics film in the past, this has never been done using a corrugator. Despite advice to the contrary our process has made this possible, the key factor we believe being the pre-made liner material, a laminate of polyester metallised film and a light paper backing. The paper backing resists stretching and minimises the distribution of heat during the laminating process.

Aspects of the present invention have been described by way of example only and it should o be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

P:\WPDOCS\DYS\SPECIE\678370.PPD 3/11/98 -6- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method of forming a laminated sheet material including the steps of corrugating a paper laminar while applying a plastics metallised liner to one or both sides of the corrugated laminar.

2. The method of claim 1 wherein the plastic metallised liner is a pre-made laminate of a paper backing with metallised polyester film.

10 3. The method of claim 1 or claim 2 wherein the liner includes a bi-axially orientated polyester film which is metallised on one side and corona treated on the other side.

Dated this 3rd day of November, 1998 15 INSUL-BOX (NZ) LIMITED By Their Patent Attorneys DAVIES COLLISON CAVE