AU2004100988B4

AU2004100988B4 - A process of manufacturing a coated shaped article

Info

Publication number: AU2004100988B4
Application number: AU2004100988A
Authority: AU
Inventors: George Panek
Original assignee: MULTIPAC SYSTEMS Pty Ltd
Current assignee: MULTIPAC SYSTEMS Pty Ltd
Priority date: 2004-11-18
Filing date: 2004-11-18
Publication date: 2005-01-20
Anticipated expiration: 2012-11-18
Also published as: AU2004100988A4

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION

PATENT

Invention Title: A process of manufacturing a coated shaped article The following statement is a full description of this invention, including the best method of performing it known to us: Freehills Patent Trade Mark Attorneys Melbourne 004572530 004561331 2 A process of manufacturing a coated shaped article 0 Z Field of the invention 00 This invention relates to a process of manufacturing a coated shaped article and the coated shaped article formed from that process. The invention is particularly suited to 00 00 5 the production of coated shaped containers from Kraft paper, but is not limited to this application.

OBackground of the invention For the transport, storage and handling of granular products, it is popular to use tubular packages made of Kraft paper. Such drums may also be used for transporting liquid or semi-liquid products such as pulp or processed food. For convenience, the tubular packages are generally cylindrical drums but octagonal, hexagonal, square or other cross-section drums may be formed.

The drums are typically manufactured by rolling fibrous material such as Kraft paper from a roll on to a mandrel to form a rotating drum. Prior to the paper being applied to the mandrel, glue is applied to the outer surface of the web of the paper to adhere the layers of the Kraft paper together to form the side wall of the drum.

These shaped drums are then affixed with a base and lid and used as containers for transport and storage.

In order to improve the weather proof properties of such shaped articles, low density polyethylene backed Kraft paper (polymer layer 22 on Kraft paper layer 21 in Figure 2) has been separately rolled on to the outer surface of the shaped article prior to the base and lid being affixed. As the outer surface of the drum already has an applied layer of adhesive, the polyethylene backed Kraft paper is able to be applied directly after the side wall forming operation has been performed with the polyethylene layer forming the outer layer of the side wall.

While a polyethylene layer provides some protection from the weather by weatherproofing the drum, the polyethylene layer is very soft and easily ruptured. Furthermore 004561331 3 the backing layer for the polyethylene layer will often be printed with letters or a colour background to make the drums more easily identified or enable drums with a differently O coloured outer wall to be produced. However the printing on to the backing layer S beneath the polypropylene layer results in poor adhesion between the polyethylene 00 layer and the backing layer resulting in poor adhesion between the polyethylene layer and backing layer. Thus the poor wear qualities of the polyethylene layer and the poor 00 o00 adhesion between the polyethylene layer and the backing layer effects the useable life of the shaped containers formed by this process.

Furthermore, as the polymer layer is to be applied to a curved surface from a roll of N 10 material, attempts to use a more rigid or stronger polymer layer to adhere to the underlying Kraft paper layer have not been able to maintain the adhesive bond between the polymer layer and the Kraft paper. Hence, attempts to use a stronger polymer onto Kraft paper have been unsuccessful.

Summary of the Invention The applicant has found that by applying a multilayered surface layer comprising a layer of polyethylene terephthalate, a layer of a polymeric material such as low density polyethylene and a backing layer of fibrous materials such as Kraft paper, a stronger more weather resistant and wear resistant drum can be produced.

Accordingly, in one embodiment of the invention there is provided a process for preparing a coated article comprising the steps of forming a shaped article from a roll of planar fibrous material by applying adhesive to one surface of the planar fibrous material and rolling the fibrous material on to a mandrel, the shaped article being formed of a plurality of layers of the fibrous material adhered together by the adhesive, and applying to the shaped article a multilayered planar material comprising a fibrous backing layer, a polymer intermediary layer, and a polyethyleneterephthalate layer, the polyethylene terephthalate layer forming the outer most layer of the coated article.

In one embodiment of the invention the planar fibrous material is Kraft paper. The polyethylene terephthalate layer is bonded to the Kraft paper by the low density polyethylene which acts as a bonding medium. The bonding medium may further 004561331 4 O include a dye suitable for use with low density polyethylene and optionally a UV c stabiliser. The applicant has found that by adding the dye to the polyethylene layer o rather than applying a colorant as a print to the fibrous backing layer, better adhesion is S obtained between the polyethylene terephthalate layer and the Kraft paper using the 00 (oo polyethylene as the bonding medium.

00 The combination of the polyethylene terephthalate layer, the polyethylene layer and the 00 backing layer enables an extremely high wearing surface to be formed on the shaped S article enhancing the structural characteristics of the resulting coated article.

C Brief description of the drawings Further features, objects and advantages of the present invention will become more apparent from the following description of the preferred embodiment and accompanying drawings in which: Figure 1 is a schematic drawing illustrating the process by which a shaped article is formed from Kraft paper and a coating layer applied to the shaped article; Figure 2 is a schematic view of a polyethylene layer applied to a Kraft paper layer; and Figure 3 is a schematic view of a PET layer applied to a Kraft paper layer with a polyethylene intermediary layer acting as a bonding layer.

In order to form a shaped article from a roll of fibrous material such as Kraft paper 1 the roll is placed on a spindle which allows the Kraft paper to rotate and feed through a series of rollers 2. The Kraft paper is typically 250-300 grams per square meter high performance. The tension in the web of fibrous material is adjusted by means of a tension roller 3. The outer side of the web of Kraft paper passes over a glue roller 4 before passing through nip roller 6 and on to mandrel 5. The tension in the web prior to the glue roller is adjusted by means of a glue application roller 7. Once the end of the Kraft paper is fed on to the mandrel 5, the mandrel rotates producing a rotating shaped article. The shaped article is rotated a sufficient amount of time to produce a side wall for the shaped article having a sufficient ply thickness to provide the required strength in the side walls of the produced article. The applicant has found that by rotating the drum 004561331 O 8-10 times thus producing an 8-10 ply thickness for the side wall sufficient structural c properties are present in the side wall of the resulting drum. The preferred number of o windings of Kraft paper is 9.15 times. As the adhesive is applied to the outer surface of S the Kraft paper, the respective layers of the Kraft paper are glued together by the oo 00 adhesive applied to the previous layer. In this way, a container of sufficient strength is produced to not only be self supporting but also contain the intended materials within o00 o00 the container.

One of the problems with forming containers from rolled or coiled materials is the difficulties of adhering the outer polymeric layer (PET) to the Kraft paper. The applicant has found that by using a multi layered material comprising a fibrous backing layer, an intermediate polymer layer and a PET outer layer, a stronger bond exists between the respective layers than would exist if the outer layer were adhered directly to the Kraft paper layer.

Hence without the intermediate polymer layer, the outer layer would adhere poorly to the Kraft paper backing layer.

The adhesive used to glue the layers of the drum together to form the 8-10 ply thick side wall is generally a polyvinylacetate adhesive which is applied directly to the web of Kraft paper. Thee water based adhesive used to glue the layers of the drum together relies on the moisture evaporating from the system causing the dispersed polymer particles to coalesce, set and dry to form a fibre tearing bond. A PVA adhesive useful in the present invention is supplied under the trade name Resyn 232.0220 by National Starch Chemical Pty Ltd. As the PET/PE/paper layer is more rigid than a conventional PE/paper layer it is necessary for the adhesive to form a stronger bond with.

Following the final layer of Kraft paper being applied to form the shaped article which is typically a tube or cylinder of Kraft paper on the mandrel a layer of glue is exposed on the outer surface.

To the shaped article, a layer of multilayered material is applied. The material is supplied by a roller 10 which feeds a web of the sheet material through rollers 11 and nip roller 12 to the shaped article on mandrel 5. As mentioned about, and shown in 004561331 6 S Figure 2 the multi layered material comprises a backing layer 31, an intermediate polymer layer 32 which is preferably low density polyethylene and a polyethylene 0 terephthalate outer layer 33. The multi layered material according to a preferred form of the invention is 165 grams per square meter high performance Kraft paper (although 00 145 gsm paper can be used) laminated using 16-24 m gsm low density polyethylene as the bonding medium to 12 pm (18 gsm) PET film. The LDPE layer includes 2 gsm of 00oo 00 specified colour master batch (grey/blue/black/red/white) supplied as fine powder and 0 compounded with the LDPE polymer. The LDPE and PET polymer mixes may also be provided with up to 0.6 wt% of a UV stabiliser to protect the polymer from long term sun 0 10 exposure and UV breakdown.

Claims

3. The process of claim 2 wherein the fibrous backing layer is Kraft paper and the layer of low density polyethylene bonds the polyethylene terephthalate layer, the low density polyethylene layer.
4. The process of claim 3 wherein low density the polyethylene layer includes a colour dye and UV stabiliser. A coated shaped articled formed by the process according to any one of claims 1 to 4 comprising a plurality of layers of fibrous material held together by an adhesive, and a polyethylene intermediate layer and a polyethylene terephthalate outer layer. Dated 17 December 2004 Freehills Patent Trade Mark Attorneys Patent Attorneys for the Applicant: Multipac Systems Pty Ltd COMS ID No: SBMI 01044508 Received by IP Australia: Time (Him) 14.54 Date (Y-M-d 204-12-17