GB2490539A

GB2490539A - Laminated packaging sheet comprising stiff and hygroscopic fibre layers

Info

Publication number: GB2490539A
Application number: GB1107548.8A
Authority: GB
Inventors: Angela Frances Morris
Original assignee: WOOL PACKAGING Co Ltd
Current assignee: WOOL PACKAGING Co Ltd
Priority date: 2011-05-06
Filing date: 2011-05-06
Publication date: 2012-11-07
Also published as: GB201107548D0

Abstract

The laminated packaging sheet comprises a stiff (rigid) layer of board, preferably cardboard, and a pliable liner secured to one side of the board. The liner comprises hygroscopic strands, preferably felted wool. The strands are compressed from their natural condition and retained in that compressed condition, preferably by needle stitching, to thereby trap air between them. Preferably the wool felt liner is fixed to the corrugated cardboard by a soluble adhesive, especially starch.

Description

Packaging Laminates This invention relates to packaging laminates and in particular sheets of such laminates that can be cut and bent to form e.g. cartons of varying shapes and sizes.

It is well known, such as from US patent number 4,765,534, to make packaging laminates in the form of corrugated cardboard in which the stiffness of the laminate is improved by the corrugations being sandwiched between respectively opposite outer layers of paper or cardboard glued to the outermost edges of the corrugations, which not only improves stiffness or rigidity but also provides a degree of impact resistance and thermal insulation. For these reasons conventional cartons for e.g. the fast food industry, such as pizza delivery cartons, are made of corrugated cardboard laminate, typically with one side of the laminate embossed or otherwise printed over with marketing information such as branding. Whilst these cartons are very cheap to produce and offer limited protection against mechanical damage to the contents, as well as being reasonably efficient for the purposes of keeping the contents warm until delivery has been made, the natural tendency of the cardboard to absorb some of the moisture from the pizza, leading to the risk of the pizza lid sagging, but not 1:'> 20 enough to absorb all the moisture from the pizza, which thereby rapidly becomes soggy throughout. The effects of both of these disadvantages increases over time so that there is a practical limit on how long it can take to deliver a freshly baked pizza before its condition or the condition of the cardboard pizza box is unacceptable to the consumer.

It is also well known from e.g. US patent number 1601625 that the hygroscopic qualities of natural wool can be used in packaging in order to absorb moisture and/or to thermally insulate the contents, such as by the use of layers of wool fixed to the walls of a cardboard pizza storage carton as is shown in W02010/119140. However, as will be appreciated, the relatively bulky nature of wool can take up significant volume within the packaging and requires containment in e.g. individual pockets or pillows, one for each wall of the storage carton, which increases the complexity of the packaging and is conducive to mass manufacture only for specifically dimensioned and shaped cartons, where the crease lines are between respectively adjacent pockets or pillows of wool.

Packaging of the foregoing type can find use in many industry sectors, such as in the medical field where pharmaceuticals or donor organs are required to be transported over relatively long periods, such as 24 to 48 hours, but where it is essential to keep the contents of the packaging within a relatively closely defined thermal range. This may be hot, warm, cool or cold, depending upon the contents of the packaging but where, in each case, the hygroscopic properties of wool are able to assist in providing the necessary insulation and minimising the thermal gradient until delivery of the package.

The present invention is derived from the realisation that there is a need for a cost effective laminate sheet which obviates the disadvantages referred to above and which may conveniently be used for producing packaging with excellent thermal characteristics and which does not substantially degrade the stiffness or rigidity of the packaging over its intended period of use.

According to a first aspect of the invention there is provided laminated packaging sheet for forming into a generally rigid insulated package, the sheet comprising a relatively stiff layer of board, such as corrugated cardboard, and a pliable liner secured to one side of the board, the liner being comprised of hygroscopic strands, such as felted wool, the strands being compressed from their natural condition and retained in that compressed condition, such as by needle stitching, to thereby trap air between the strands and act as a heat insulant, the strands also acting to, in use, absorb moisture therewithin or thereupon.

With this arrangement, the laminated sheet can be mass produced and subsequently cut and formed from a roll into packaging of any required shape without the need, separately, to provide insulation within the package or its contents, which may be initially hot, in the case of fast foods such as pizzas, or initially cold in the case of e.g. medicines, where the packaging may take the form of inner liners for containers made of other materials, such as metal or plastic, for transporting quantities of medicines or other material while keeping them within a required temperature and/or humidity range.

Advantageously, the hygroscopic strands are aligned, such as by felting, and, following compression, they are held in their compressed condition, such as by needle stitching, i.e. by driving hooked needles through the strands and pulling the needles out, thereby snagging some of the strands so that, instead of being aligned with the rest of the strands they are at least partially orientated transverse thereto. Conveniently, the strands may comprise a layered mix of different material, such as virgin wool for forming an outer layer and recycled wool or other material in an inner layer.

Example

Two square samples of pure wool were tested using a Fox 200 heat flow meter manufactured by LaserComp, Inc, with each sample being approximately mm2 and weighing approximately 28g. One sample was uncompressed and had a thickness of 35mm, whereas the other sample was compressed to a thickness of about 10mm. Ambient temperature was 21°C with relative humidity at 67%. The thermal plates were set at 0°C and +20°C respectively to produce a mean temperature of 10°C with water being used as the coolant to maintain these plates to within 0.03°C by means of Peltier heating and cooling. Each initial test run lasted well over 2.5 hours, during which each sample gained weight by about 0.2gms, (later tests were well over 7 hours, although it was found that by 2 hours equilibrium was generally reached). At the end of each initial test the Lambda values (W/m.°K) were, respectively, 0.0396 and 0.02983.

These tests showed conclusively and counter-intuitively that compression of the wool actually increased its thermal insulation properties, and was sufficient to show that compressed wool or wool composites can be used in packaging without seriously compromising the available space for the packaged item or the hygroscopic properties of the wool. Later tests confirmed this general principal.

A moisture permeable layer, such as a paper layer, may advantageously . 20 cover the liner so as to prevent or inhibit the hygroscopic strands from touching the contents of e.g. a carton manufactured using the laminated sheet, which carton may thereafter be recyclable or fully compostable.

Conveniently, the liner is fixed to the corrugated board by a soluble adhesive, such as starch, so that above a chosen level of water content the adhesive dissolves when e.g. the carton has been composted.

The invention also extends in a second aspect to pre-cut sheets of insulated board provided with e.g. mitres or other pre-cut shapes by which connected sections of board can thereafter be bent to form cartons having the internal shape of another container into which the board is then placed to provide thermal insulation. This is particularly advantageous where e.g. robust plastics or metal containers are being used to transport delicate goods such as human tissue or medicines requiring residence during transport within a tightly defined range of temperatures, such as between 4°-8° C for a relatively long period of time, such as 48 hours. In a similar vein, fresh food, such as meat, fish, fruit and vegetables, can be transported in strong but lightweight bins or other such containers so that they are able to withstand the mechanical handling stresses during transport, while the goods themselves are cocooned within an easily replaceable carton made from the laminated sheet of the invention, which therefore assists in protecting the contents of the carton from mechanical shock, insulates the contents sufficiently to ensure that they arrive at their destination still within the required temperature range and ensures that the correct level of humidity is maintained.

The invention in a further aspect also extends to a carton made from laminated sheet according to the invention in which the outer walls are corrugated board, such as cardboard, and the inner walls are comprised of or include hygroscopic strands as the liner, either with or without a protective but permeable cover for the liner.

In a still further aspect the invention also extends to drink containers insulated by compressed wool or wool substitute forming part of the walls of the container, or alternatively to a drink container holder for providing insulation for e.g. hot or cold drinks within a conventional drinks container, such as a paper or plastics cup.

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Claims

Claims 1. A laminated packaging sheet for forming into a generally rigid insulated package, the sheet comprising a relatively stiff layer of board, such as corrugated cardboard, and a pliable liner secured to one side of the board, the liner being comprised of hygroscopic strands, such as felted wool, the strands being compressed from their natural condition and retained in that compressed condition, such as by needle stitching, to thereby trap air between the strands and act as a heat insulant, the strands also acting to, in use, absorb moisture therewithin or thereupon. c\J
2. A packaging sheet according to Claim 1 wherein the hygroscopic strands are aligned, such as by felting, and, following compression, they are held in their compressed condition, such as by needle stitching.

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3. A packaging sheet according to Claim I or Claim 2 wherein the strands comprise a layered mix of different material, such as virgin wool for forming an outer layer and recycled wool or other material in an inner layer.
4. A packaging sheet according to any preceding Claim including a moisture permeable layer, such as a paper layer covers the liner so as to prevent or inhibit the hygroscopic strands from touching the contents of e.g. a carton manufactured using the laminated sheet.
5. A packaging sheet according to Claim 4 wherein the liner is fixed to the corrugated board by a soluble adhesive, such as starch, so that above a chosen level of water content the adhesive dissolves when e.g. the carton has been com posted.
6. A pre-cut sheet of insulated board according to any preceding Claim provided with e.g. mitres or other pre-cut shapes by which connected sections of board can thereafter be bent to form cartons having the internal shape of another container into which the board is then placed to provide thermal insulation.
7. A carton made from laminated sheet according to any preceding Claim in which the outer walls are corrugated board, such as cardboard, and the inner walls are comprised of or include hygroscopic strands as the liner, either with or without a protective but permeable cover for the liner.
8. A drink container insulated by compressed wool or wool substitute c\J forming part of the walls of the container.C\J
9. A drink container holder insulated by compressed wool or wool substitute for providing insulation for e.g. hot or cold drinks within a conventional drinks container, such as a paper or plastics cup.