Board Material and Method of Manufacture

This invention relates to board material and a method of manufacture of board material. The invention also relates to a carton formed using the board material and a method of manufacturing a carton.

Although the following description refers almost exclusively to board material that is used to form a carton in the form of a tube, it will be appreciated by persons skilled in the art that the board material of the present invention can be used for any suitable purpose and can be used to form any shaped carton.

Tubular shaped cartons are well known in the field of packaging and carton manufacture for the containment of a variety of items, particularly for the containment of food and drink items, such as wine or spirit bottles, crisps and/or the like. A conventional method of manufacture of a tubular shaped carton is to take a single sheet of board material with a tab portion along a free edge thereof, and fold the board material such that the free edge with the tab portion is brought into engagement with an opposite free edge of the board material. The tab portion is adhered to the opposite free edge to form a tubular sleeve. A problem with this type of carton is that is lacks strength and rigidity and the shape of the carton is typically maintained by one or more items located in the carton in use.

In an attempt to overcome the abovementioned problem, it is known to form a tubular shaped carton using laminate board material, typically comprising two or more layers of board material, to provide greater strength and rigidity to the carton walls. The carton is formed in a similar manner to the single board material carton but it is still found that the shape of the carton is not maintained and is easily collapsible when empty. As such, end pieces are typically required, such as base and top inserts, to maintain the tubular shape of the carton. This increases the cost of the product and the complexity of the manufacturing process.

A further known process is described in GB2294021. In this process, two single board panels are adhered together using a water based adhesive and, whilst the adhesive is still wet, the laminate board panels are formed around a suitably shaped mandrel and are left to dry. The panels dry in the shape of the mandrel, such that when die panels are removed from the mandrel, they typically retain the shape of the mandrel. However, a problem with this process is that it is time consuming and dius relatively expensive since it requires the panels to remain on the mandrel until the adhesive is dry. In addition, the cartons can often not be formed at the site of filling of die cartons due to it being a health hazard to have wet adhesive near food products.

It is therefore an aim of the present invention to provide a method of forming board material which overcomes the abovementioned problems.

It is a further aim of the present invention to provide board material formed using an improved method.

It is a yet further aim of the present invention to provide a carton which overcomes the abovementioned problems.

It is a yet further aim of the present invention to provide a method of manufacture of a carton which overcomes the abovementioned problems.

According to a first aspect of the present invention there is provided a method of forming board material, said board material formed by applying adhesive means to at least one surface of said board material, wherein the adhesive means has a composition such mat, on application of heat thereto, the board material is changed is from a first, substantially flexible condition to a second, relatively rigid condition.

Preferably the adhesive means is allowed to dry prior to application of heat thereto. Thus, the adhesive means is typically applied at the point of manufacture of die board material and, when dry, can be easily transported

to any remote location for construction, use and/or application of heat thereto.

Preferably the adhesive means is irreversibly changed following the application of heat thereto.

In one embodiment the adhesive means is in the form of or includes a cross linked polymer. The application of heat to the polymer results in a change in the chemical structure of said cross linked polymer.

In one embodiment the final board material comprises a single ply or layer of board material. Preferably the adhesive means is impregnated into the board material.

In one embodiment the final board material includes at least two layers of board material which are adhered together using said adhesive means. Preferably the adhesive means is located between said layers of board material. Further preferably the at least two layers of board material are brought into overlapping engagement with each other and adhered.

In one embodiment, the board material is moved, folded and/or assembled from a sheet or substantially two dimensional form to a shaped or substantially three dimensional form prior to application of heat thereto.

In one embodiment a carton can be constructed using said board material. The shape of the carton is relatively flexible until the application of heat thereto, after which the board material or carton is provided with rigidity and strength and the shape of the carton is maintained. The adhesive means is preferably allowed to dry prior to application of heat thereto.

Preferably the cross linked polymer adhesive includes a pre-determined concentration of PVA (polyvinyl acetate).

In one embodiment the heat applied to the board material raises the temperature of the board material at least above room temperature (i.e. above approximately 18-23°C). Preferably the temperature is at least 80 degrees C.

In one embodiment die carton is formed on a mandrel or other suitable support means which allow the shape of the carton to be retained whilst place thereon or therewidi. Preferably the heat is applied to the carton just prior to or when on said mandrel or other support means.

Preferably the carton is in the form of a tubular carton.

In one embodiment pressure is applied to the board material and/or carton in addition to said heat. The pressure is preferably applied when said carton is being formed on a mandrel or other suitable support means. Further preferably the heat and pressure are applied substantially simultaneously

In one embodiment the thickness of each of the board material layers when at least two layers are provided is approximately 450μm in thickness, thereby forming a final board material of approximately 950μm in diickness.

The adhesive is typically provided substantially evenly over substantially an entire surface of one or at least two material layers of board material.

According to a furmer aspect of the present invention there is provided board material formed using the method described above.

According to yet further aspect of the present invention there is provided a method of manufacturing a carton formed from board material using the abovedescribed meύiod.

According to a further aspect of the present invention there is provided a carton formed from board material. In a further aspect there is provided a carton blank for forming the carton.

According to a yet further aspect of the present invention there is provided a method of manufacturing a carton, said carton formed from board material and said board material formed from at least one panel member with adhesive means, said method including the steps of moving said board material when said adhesive is dry to form one or more walls of said carton in a required shape, applying heat to said board material when in said required carton shape and said adhesive means being such that the application of said heat changes the board material from a first, substantially flexible condition to a second, relatively rigid condition, thereby maintaining the board material in the required carton shape.

According to a further aspect of the present invention there is provided a method of manufacturing a carton, said carton formed from board material and said board material formed from at least two panel members with an adhesive means lying therebetween, said method including the steps of moving said board material when said adhesive is dry to form one or more walls of said carton in a required shape, applying heat to said board material when in said required carton shape and said adhesive means being such that the application of said heat changes the board material from a first, substantially flexible condition to a second, relatively rigid condition, thereby maintaining the board material in the required carton shape.

Preferably the board material is formed by applying the adhesive to one panel of said board material and placing the other panel of board material onto the first in substantially overlapping arrangement with the adhesive sandwiched between the two sheets or panels of board material.

In one embodiment, once the final board material is formed the application of heat thereto results in a change in the chemical structure of said cross linked polymer adhesive and changes the board material from a first, substantially flexible condition to a second, relatively rigid condition.

In one embodiment the board material is formed into a three dimensional shape when in a substantially flexible condition by any of pressing, twisting, creasing , moulding or forming or any combination thereof.

An embodiment of the present invention will now be described with reference to the accompanying figures, wherein:

Figure 1 illustrates a simplistic view of formation of the board material used to construct the carton;

Figures 2a-2d illustrate the steps involved in formation of a carton from the board material formed in figure 1.

Referring to figure 1, laminated board material 2 is formed of approximately 950μm in thickness by bringing two panels 4, 6 of board material of approximately 450μm thickness together in overlapping relationship from rolls 5, 7 on which the panels are initially wound, applying adhesive 8 to an inner surface 9 of panel 6 prior to engagement with board material panel 4 and applying pressure to the overlapping board material panels via rollers 10, 12 to adhere the panels together. The board material is allowed to dry and is then used for carton construction. When dry, the board material can be transported to any suitable location and can be used in any suitable environment, such as in a food processing plant and/or the like.

The adhesive can be applied via any suitable method and said adhesive is typically provided substantially evenly over the entire inner surface 9 of panel 6. The adhesive used to form the lamination in one embodiment is a heat sensitive PVA including a cross linked co-polymer. However it should be appreciated that the adhesive used may be a single part or 2 part cross linking adhesive or, in another embodiment may be non cross linking.

In the illustrated example, a carton construction 14 is formed from a single blank 16 of laminated board material 2, as shown in figures 2a-2d. Blank 16 includes a front panel 18, joined to side wall panel 20 along fold line 22. A

rear panel 24 is joined to an opposite edge of side wall panel 20 along fold line 26. A further side wall panel 28 is joined to rear panel 24 along fold line 30. A tab portion 32 is joined to side wall panel 28 along fold line 34. The blank is folded along the fold lines 22, 26, 30, 34 and tab portion 32 is adhered to an inner surface of front panel 18 to form a sleeve or carton 14. The resulting carton has a first open end 36 and a second open end 38. It will be appreciated that any shaped carton can be formed with any number of blanks and can have closed ends and/or the like if required.

The carton 14 is then located over a mandrel 38 widi the carton in heated condition or the same may be heated when on the mandrel, as shown in figure 2c. Application of heat to the carton causes the cross linked copolymer adhesive located between the board panels to irreversibly change in chemical structure. This chemical structure solidifies the adhesive and changes the board material panels 4, 6 from a substantially flexible condition to a substantially rigid condition. As such, the resulting tubular carton 40 is formed from carton 14 on removal from the mandrel and has permanently taken up the shape of the mandrel, thereby forming a carton which is substantially strong and rigid and of the required shape.

The adhesive coating may be supplied in solution, dispersion or emulsion form or hot melt as a thermoplastic polymer system. After cross linking the polymer system may become non-diermoplastic (thermoset) but may retain a degree of thermoplasticity at elevated temperatures.

The adhesive coating used may also be modified for particular manufacturing or end use applications and can vary in terms of film hardness, glass transition temperature, modulus, tensile strength, flexibility, colour, feel, open time, viscosity, solids content, pH, gloss, abrasion resistance, shear resistance, peel resistance, wet or dry tack, UV resistance, and/or plasticiser migration resistance.

Furthermore, although the drawings how the formation of a two ply board material, in another embodiment of the invention, a single ply board

material may be used in which at least one of the planar surfaces of the board material has a layer of the adhesive applied thereto, preferably in a manner to be impregnated into the board material. The subsequent application of heat to the same results in a similar reaction and ability to form the same as described above.

It should also be appreciated that although the example shows the forming of the board material around a mandrel, other means may be used to change the shape of the board material, such as for example, creasing of the material, and/or twisting and/or pressing or any combination of those or indeed any other suitable forming method.

Thus, the present invention allows a substantially rigid board material and, in one embodiment, carton or other required final form, to be formed without requiring wet adhesive to be present during the carton construction stage, although a small amount can be used, if required, for adhering a tab to a wall of the carton. It should also be appreciated that the final product may be adapted to suit particular uses of the same and/or to meet food and/or drug standards.