PROCESS AND DEVICE FOR MAKING A CORRUGATED SHEET FOR CONTAINERS

Abstract: The present invention relates to a method of forming a laminated material comprising the steps of corrugating a paper sheet (1), and applying a liner (4) to one or both sides of the corrugated sheet, wherein the liner is a pre-made laminate of a paper backing and plastic film which is metallised on one side and corona treated on the other side. A laminating apparatus for use in the above method is also described herein, which includes a means for feeding out a paper sheet and a liner to a set of corrugating rollers (6), the liner being a pre-formed laminate of paper and plastics film, and means for uniting the paper sheet and liner immediately subsequently to the corrugation of the paper sheet.

Description: PROCESS AND DEVICE FOR MAKING A CORRUGATED SHEET FOR 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. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF INVENTION According to the present invention there is provided a method of forming a laminated material comprising the steps of corrugating a paper sheet and applying liner being a pre-made laminate of a paper backing and plastics film which is metallised on one side and corona treated on the other side. The liner can include a bi-axially orientated polyester film which is metallised on one side and corona treated on the other side. The liner can be preheated prior to its application to the paper sheet. The liner can be heated by heating rollers and adhered to the paper sheet using a PVA adhesive with the metallised film of the liner outermost. The liner can be heated by heating rollers and adhered to the paper sheet using a PVA adhesive with the metallised film of the liner innermost. According to a further aspect of the invention there is provided a laminating apparatus including means for feeding out a paper sheet and a liner to a set of corrugating rollers, the liner being a pre-formed paper laminate of paper and plastic film, and means for uniting the paper sheet and liner subsequent to the corrugation of the paper sheet. The apparatus can include means for pre-heating the paper sheet and liner prior to same being fed to the corrugating rollers. The apparatus may include means for feeding a second liner for lamination with the paper sheet. The lamination of the paper sheet and liner with the second liner can be subsequent to the lamination of the paper sheet with the liner. The lamination of the paper sheet and the liner with the second liner can be achieved with the assistance of a cluster of in-line pressure rollers. The second liner can be a laminate of a plastics film and paper. 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 materials. BRIEF DESCRIPTION OF DRAWINGS Aspects of the present invention will be described in relation to the accompanying drawing 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 preheating 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 rollers 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 apparatus 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 = 2.0 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°C) the board, because of the metallised exterior retains heat for some time, during which time care must be taken when handling the product. 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 known 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 be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims: THE CLAIMS DEFINING THE INVENTION ARE: 1. A method of forming a laminated material comprising the steps of corrugating a paper sheet and applying a liner to one or both sides of the corrugated sheet said liner being a pre-made laminate of a paper backing and plastics film which is metallised on one side and corona treated on the other side. 2. A method as claimed in claim 1 wherein the plastics film is bi-axially oriented polyester film. 3. The method of claim 1 or claim 2 wherem the liner is preheated prior to its application to the paper sheet. 4. The method of claims 1 to claim 3 wherein the liner is heated by heating rollers and adhered to the paper sheet using a PVA adhesive with the metallised film of the liner outermost. 5. The method of any one of claims 1 to 3 wherein the liner is heated by heating rollers and adhered to the paper sheet using a PVA adhesive with the metallised film of the liner innermost. 6. A method as claimed in any one of claims 1 to 5 wherein the plastics metallised liner is laminated to one side of the paper sheet as the paper laminar is fed from the corrugating rollers. 7. Laminating apparatus including means for feeding out a paper sheet and a liner to a set of corrugating rollers, the liner being a pre-formed laminate of paper and plastics film, and means for uniting the paper sheet and liner immediately subsequently to the corrugation of the paper sheet. 8. Laminating apparatus as claimed in claim 7 including means for pre-heating the paper sheet and liner prior to them being united. . Laminating apparatus as claimed in claim 7 or claim 8 including means for feeding a second liner for lamination with the first paper sheet. 10. Laminating apparatus as claimed in claim 9 wherein the lamination of the paper sheet and liner with the second liner is subsequent to the lamination of the paper sheet with the liner. 11. Laminating apparatus of 9 or claim 10 wherein the lamination of the paper sheet and the liner with the second liner is achieved with the assistance of a cluster of in-line pressure rollers. 12. Laminating apparatus as claimed in any one of claims 9 to 11 wherein the second liner is a laminate of a plastics film and paper. 13. A container formed from a laminate manufactured in accordance with the method of any one of claims 1 to 6. 14. A method of forming a laminated sheet material substantially as herein described with reference to the accompanying drawings. 15. Laminating apparatus substantially as herein described with reference to the accompanying drawings.

Inventors: HARRISON WAYNE JOHN, HARRISON, WAYNE, JOHN
Applicants: HARRISON WAYNE JOHN, INSUL BOX NZ LIMITED, HARRISON, WAYNE, JOHN, INSUL-BOX (NZ) LIMITED
Application year: 1998
Main classification: B32B29
IPC codes: B31F1, B32B3, B32B15, B32B29, B65D65