WO2000076859A1

WO2000076859A1 - Reinforced collapsible container

Info

Publication number: WO2000076859A1
Application number: PCT/GB2000/002300
Authority: WO
Inventors: Robert Mcgeehin
Original assignee: Rexam Plastic Packaging Limited
Priority date: 1999-06-16
Filing date: 2000-06-14
Publication date: 2000-12-21
Also published as: AU5413900A

Abstract

A closable collapsible container (30) made from stiff paperboard, the container having four side walls (33) intended to form an enclosed space when the container is erected, and having hinged flaps (32) or separate sheets to form the closure of the base or top, in which when the container (30) is in its erected form the side walls and flaps or closure sheets are held in place by securing means such as strips of adhesive tape (37, 38) for filling, storage and transport while filled, characterised in that at least the points (35, 36) at which the securing means (37, 38) are applied to the paperboard are reinforced by chemical treatment of the paperboard.

Description

REINFORCED COLLAPSIBLE CONTAINER

This invention relates to collapsible containers having reinforcement to prolong their working lives. It is particularly concerned with reinforcement of containers made of paperboard.

Sheets of paperboard, such as cardboard or stiff flat paper, are commonly used to form box-like containers for transport of various products and materials. Advantages of containers formed of paperboard sheets are that they can be stored flat until required for use, can readily be assembled into the hollow shape needed for filling, and can be recycled after emptying, provided that their opening and emptying has not caused unacceptable damage to the paperboard. They are also lightweight and relatively inexpensive.

The filled container assists in handling its contents and affords a measure of protection for them. The paperboard sheet is typically pre-formed into a "carton blank" with cuts and embossed fold lines which enable it to be folded into the desired hollow shape. A second blank with cuts and embossed fold lines is employed for containers having a separate lid.

All sides of the container are usually rectangular in shape, giving a six sided container. The four sides that in usual filling and emptying operations will be vertically disposed are permanently secured, for example by a narrow overlapping adhesive flap (glue lap) and/or associated staples, but the top and the base are typically formed of openable overlapping flaps or a separate removable sheet of card as a lid or base. An integral base is commonly made from two pairs of folded- over flaps, of which the outer pair have their adjacent borders secured together, for example by means of strips of broad adhesive tape. After the container has been filled and closed, its upper flaps or lid are similarly secured.

When the container is to be emptied, the securing means is either wrenched off or cut, to give access to the contents. If the container is to be reused or recycled after it has been emptied, the securing means has to be removed, which in the case of adhesive tape is a messy and time-consuming operation, and the removal often damages the container to the extent of leaving it unusable for anything other than scrap.

There is a considerable perceived need to recycle materials such as paperboard, both for reasons of economy and the environment, especially with a view to reducing the enormous quantities of paper products used in packaging and like duties.

Various proposals have been for the provision of recyclable collapsible containers. Our earlier patent specification WO 98/05562 relates to a closable collapsible container having two pairs of side walls, each with two projecting flaps hinged about an edge of the side wall, in which the two openings of the container formed by the side walls are intended to be securely closed by two co-operating pairs of flaps, in which the inner flaps have on their outer surfaces, near the hinge line, one part of a two-part separable non-adhesive coupling, and in which the outer flaps have on their inner surfaces the other parts of the couplings, in positions complementary to those on the inner flaps, whereby the container may be erected and collapsed secured together in their closed positions without the use of adhesive tape. This provides a convenient way of ensuring that the container may be reused repeatedly without the use of adhesive tape or of any other potentially damaging connectors for holding the co-operating flaps securely together.

The present invention aims at reinforcing those parts of the container to which securing means are attached and thereby to increase the number of fill, empty and return cycles it can undergo before being scrapped.

According to the present invention there is provided a closable collapsible container made from stiff paperboard, the container having four side walls intended to form an enclosed space when the container is erected, and having hinged flaps or separate sheets to form the closure of the base or top, in which when the container is in its erected form the side walls and flaps or closure sheets are held in place by securing means for filling, storage and transport while filled, characterised in that the points at which the securing means are applied to the paperboard are reinforced by chemical treatment of the paperboard.

In one embodiment of the invention there is provided a closable collapsible container made from stiff paperboard, the container having four side walls intended to form an enclosed space when the container is erected, and having hinged flaps or separate sheets to form the closure of the base or top, in which the side walls and flaps or closure sheets carry components of a two-component, separable, non- adhesive coupling, which components co-operate to hold the container in position for filling, storage and transport while filled, and are releasable to permit its emptying and collapsing when empty, characterised in that the points at which the respective components of the couplings are secured to the paperboard are reinforced by chemical treatment of the paperboard.

One suitable two-component, separable, non-adhesive coupling for the purposes of the invention is that sold under the trademark 'Velcro ', of which each component is made from fabric. One component presents a looped pile, while the other presents a hooked pile. When the two components are pressed together, the hooks engage the loops to hold them in a firm grip, which may be loosened and released by pulling the two components apart.

An alternative kind of two-component, separable, non-adhesive coupling is one in which the couplings are made from moulded plastics material of which the two components may be latched together.

The respective components of the couplings used in the invention on the container's walls and closure flaps on the walls or lid are secured to their respective points by means of an adhesive. The couplings are not damaged by repeated application and separation, as long as the grip between them is less than the force by which the adhesive holds them on their respective walls or flaps. In one embodiment of the invention the respective components of the coupling are colour-coded, the components to form one part of the coupling, for example the looped pile component of a Velcro® fastening, being of a different colour from the components forming the other part, for example the hooked pile component of a Velcro® fastening. The colour coding assists in correctly aligning the respective components when assembling the container. Preferred colours are orange for the looped components and yellow for the hooked components.

When using Velcro® fastenings it is preferred that the looped components should form the inner part of the coupling, i.e. being placed on the walls of the container and on the inner flaps of the base, and the hooked components should form the outer part of the coupling, i.e. be on the inner side of lid flaps and on the inner side of outer top or base flaps.

In a further embodiment of the invention there is provided a closable collapsible container made from stiff paperboard, the container having four side walls intended to form an enclosed space when the container is erected, and having hinged flaps or separate sheets to form the closure of the base or top, in which when the container is in its erected form the side walls and flaps or closure sheets are secured by adhesive tape which holds the container in position for filling, storage and transport while filled, characterised in that the points at which the adhesive tape is applied to the paperboard are reinforced by chemical treatment of the paperboard.

Examples of the paperboard used for making the container include kraft paper, test paper or a combination of these.

Reinforcement of the points at which the securing means are applied to the paperboard reduces or eliminates any tendency for the paperboard to delaminate at these points. Delamination is potentially a serious problem in creating unacceptable damage to a portion of the container, even though the remainder of the paperboard is in a good and reusable condition. Paperboard containers having the reinforced areas described and claimed herein have proved to be capable of being repeatedly recycled and indeed to permit a greater number of return trips than is achieved by untreated containers.

Suitable adhesives for attaching the securing means (whether coupling components or adhesive tape) include vegetable adhesives such as starch, dextrins, gum arabic and tragacanth; cellulosic adhesives such as methyl cellulose, ethyl cellulose and cellulose acetate; thermoplastic resins such as polyvinyl acetate, polyvinyl butyral, polystyrene and acrylic resins; fhermosetting resins such as phenol-aldehyde, urea- aldehyde and polyurethane resins; rubber adhesives such as rubber latex in a solvent; and inorganic adhesives such as sodium silicate.

When the adhesive is used with coupling components the particular combination of treatment agent for the paperboard and adhesive to bond the coupling component to the paperboard should of course be chosen from compatible materials. When used on adhesive tapes the substrate on which the adhesive is carried may be for example a flexible plastic film such as cellulose acetate or a high quality paper such as a silicone kraft paper. The side of the substrate opposite to the adhesive may carry a release coating.

In general the bond formed between the aforementioned adhesives and the paperboard is stronger than the intrinsic strength of the paperboard. The chemical treatment of the invention has the objective of increasing the strength of the paperboard to exceed that of the bond.

Suitable chemical treating agents include emulsions, solutions or dispersions of one or more of the following:

plasticised or unplasticised polyvinyl acetate homopolymer, polyvinyl ethylene copolymer, polyethylene wax, styrene butadiene copolymer, polyvinyl alcohol, methacrylate copolymers, plasticised or unplasticised vinyl acetate copolymers, ethylene acrylic acid copolymer, mineral wax, natural wax, aqueous polyethylenimine, cationic polyacrylamide, aqueous poly(amidoamine epichlorohydrin) , aqueous acrylic ester copolymers, aqueous styrene butadiene copolymer, aqueous acrylonitrile, starch and cellulose ether.

Suitable means of applying the chemical treatment agent include spraying, brushing, coating or printing. The printing may for example be flexography, conventional or offset, silk screen, gravure or letterpress.

The chemical treatment agent can if desired be applied with the assistance of a mask having an orifice or orifices in the shape of the region (s) to be treated, so as to avoid unnecessary treatment of areas beyond the said region(s) .

The quantity of chemical treatment agent applied at each region is preferably such as to be absorbed into the structure of the paperboard to a depth of one-third to one- half of its thickness. This quantity can be determined by trial on a specimen piece of the paperboard. The agent is preferably not applied through the whole thickness. Although such through application would give good strength it tends to create patches of unattractive appearance on the far side of the paperboard.

If desired the whole of the outer surface of the container can be subjected to the chemical treatment. While this increases the amount and expense of the treatment it provides a form of coating across the whole of the exposed surface of the container. This coating offers the advantages of stiffening the surface and of giving it increased impermeability and thus a degree of water- resistance. Paperboard of test grade when so treated has a quality resembling that of the more expensive kraft paper.

For many purposes however it is sufficient to apply the chemical treatment to those parts of the paperboard in the vicinity of its points of contact with the respective securing means. The treatment is preferably applied to a region which includes the area of contact with the securing means plus a border zone around the said area. The border zone provides reinforcement at the lines of greatest stress between the paperboard and securing means, namely the lines of the periphery of the said means. The border zone preferably has a width of 5 to 25 mm around the whole periphery of the said area of contact. If the treated area for use with adhesive tape is less than the whole area of the container it may be desirable to include marking to make clear the extent of the treated area and thus to ensure that the adhesive tape is applied to a treated portion. Such marking may be for example printed lines marking the boundaries of the treated area or a coloration applied to the whole of the treated area.

The particular combination of adhesive for adhesive tape and treatment agent for the paperboard should be chosen so as to permit the tape to be readily peeled from the container when it is required to open the container. The adhesive should preferably be selected as a "low-tack" adhesive having an intermediate degree of bond strength to the treated area: sufficient to maintain the container in a closed state when required, but not so strong as to create a significant risk of delamination of the paperboard. Similarly the chemical treatment agent should be selected to function as a release coating so as to facilitate the removal of the adhesive tape when required. Thus the adhesives and treatment agents for use with adhesive tape, while selected from the same general categories as those for the two-part couplings and associated paperboard, preferably have respectively lower adhesive properties and higher release properties.

The combination of a low-tack adhesive tape and release-coating treatment as above provides the desirable combination of easy peeling of the adhesive tape while retaining substantial bonding strength in the directions of stresses imposed upon the bond by the box and its contents. Low-tack adhesive tape as preferred for this duty is preferably marked as such so as to reduce the likelihood of a high tack adhesive tape being inadvertently used.

In one convenient embodiment of the invention the adhesive tape is provided with a tab at one or more ends so as to facilitate removal of the tape from the container.

The present invention is further described by way of non-limiting example with reference to the accompanying drawings, in which: Figure 1 is an isometric view of one version of container according to the present invention, being a lidded container with its lid in position.

Figure 2 is an isometric view of the container shown in Figure 1, but with its lid removed and its flaps in an intermediate position.

Figure 3 is a plan view of the lid of the container shown in Figure 1 , with its side flaps in an unfolded position.

Figure 4 is an isometric view of a second version of container according to the present invention. The container is shown in its erected state but with two pairs of upper closure flaps in an open position.

Figure 5 is a perspective view of the erected container illustrated in Figure 4 but with the flaps closed and with adhesive sealing tape in position.

The container of Figures 1 to 3, indicated generally by the reference number 2, is made from cardboard. It is shown in its loading position, with continuous upright sidewalls 4 and a base made from two pairs of overlapping flaps, i.e. a pair of inner flaps (not shown) and a pair of outer flaps 8. When closed, it further includes a lid 20. The lid 20 has a central flat portion 22, hinged flaps 24 on its shorter sides and hinged flaps 26 on its longer sides.

Secured by hot melt acrylic resin adhesive to the upper corners of the side walls 4 of the container 2 are looped Velcro® components 14, having a rectangular shape. Similar looped components are secured by adhesive to the inner flaps of the base. Correspondingly shaped and located hooked Velcro® components 16 are secured by the adhesive to the lid flaps 24 and 26, close to their respective ends, and to the inner side of the base flaps 8. The components 16 on the lid flaps 24 and 26 extend most of the distance from the flap hinge to the flap edge.

Prior to the securing of the coupling components 14 and 16, the cardboard is treated in the intended regions for the said components 14 and 16 with an emulsion of styrene butadiene copolymer as a chemical treating agent. The agent is applied by spraying and in combination with a mask. The treated areas are indicated in Figures 2 and 3 by the reference numeral 15. The respective components 14 and 16 are then secured by the polystyrene adhesive to the treated area, leaving a treated zone around each component 14, 16.

Before the container is filled, the inner flaps for the base are folded over into coplanar positions and the outer flaps 8 are pressed against the contacting surfaces of the inner flaps to hold them together. The holding action is achieved by pressing together the respective hooked components 16 on the outer flaps 8 and matching looped components on the inner flaps. After the container 2 has been filled, the lid 20 is applied to close it. The lid flaps 24 and 26 are folded into position and their hooked components 16 are pressed into contact with the matching looped components 14 on the side walls 4.

The contents of the filled container provide an 'anvil' to support the looped components while pressure is applied to the hooked components, and thus assist in achieving a firm hold between the respective hooked and looped components.

After the lid 20 has been removed, by pulling its flaps 24 and 26 away from the sidewalls 4 with sufficient force to cause the coupling components to lose their grip on each other, and the filled container has been emptied the lid flaps 24 and 26 are hinged back to a flat position and the open-box part of the container 2 is collapsed, for example by gripping a base outer flap 16 and pulling it away from the inner flap with sufficient force to separate their coupling components. The box may then be folded flat by causing the two pairs of side walls 4 to be flattened together, with their respective flaps lying in the same plane as the side walls.

The container of Figures 4 and 5 is indicated generally by the reference number 30. Made from cardboard of test quality, it comprises four continuous side walls 33 (a-d) and two sets of two pairs of overlapping closure flaps hinged to the side walls. One set of flaps forms a closable top for the container, including a pair of inner flaps 31 and a pair of outer flaps 32 (x and y). An equivalent set of two pairs of overlapping closure flaps forms a closable base for the container.

Side walls 33a and 33b are visible in the figures but side walls 33c and 33d are out of sight on the far side of the container, 33c opposite 33a and 33d opposite 33b. Side wall 33a carries a central band 35 formed by spraying polyethylene wax through a wide elongated slot in a masking stencil. Side wall 33c carries an equivalent central band (not visible in the figures). The outer flaps 32x and 32y carry similarly treated bands 36x and 36y on their outer surfaces adjacent to the edges remote from their hinges, the combined width of bands 36x and 36y being the same as the width of band 35. The (unseen) outer flaps of the base carry treated bands equivalent to 36x and 36y.

When the container is in the closed position the various central bands (35, 36x, 36y etc.) form a continuous treated zone of uniform width around the container. The polyethylene wax treatment around the band is to a depth of one third of the thickness of the cardboard.

Before the container is filled, the base inner flaps and then its outer flaps are folded over into coplanar positions, and a strip 37 of low-tack adhesive tape (carrying methyl cellulose adhesive) of lesser width than the treated zone (35, 36) is placed centrally on the said zone, extending across the base of the container and up to about one third of the height of the side walls 33a and 33c. The container is then filled and the upper set of flaps 31 and 32 are similarly folded into their closed positions, and a strip 38 of low-tack adhesive tape is placed centrally on the treated zone, extending across the top of the container and downwards by about one third of the height of the side walls 33a and 33c. One end of each of the strips 37 and 38 is provided with a plastic tab 39 to facilitate their subsequent removal.

At the delivery point the strip 37 is removed to permit opening of the flaps 31 and 32 for unloading of the contents. After unloading the strip 38 is removed and the container flattened for recycling. Flattened container boxes and lids as above can be returned to a filling point in a compact stack occupying much less space than the filled container and thus making the return much more economically viable. Containers treated and thus reinforced according to the present invention can normally be recycled for many more times than previously proposed containers before wear and tear require them to be repaired or scrapped.

The present invention thus provides a significant increase in the working life of a given container, with corresponding environmental and cost-saving advantages, especially in significantly reducing the requirements for new packaging material. The environmental advantages include savings on consumption of fuel, wood-pulp and potentially hazardous treatment chemicals used in the primary manufacture and repulping of wood-pulp. The cost savings include a saving on any packaging tax or levy.

Claims

O 00/76859CLAIMS

1. A closable collapsible container (2, 30) made from stiff paperboard, the container having four side walls (4, 33) intended to form an enclosed space when the container is erected, and having hinged flaps (16, 31 , 32) or separate sheets (20) to form the closure of the base or top, in which when the container (2, 30) is in its erected form the side walls and flaps or closure sheets are held in place by securing means (14, 16, 37, 38) for filling, storage and transport while filled, characterised in that the points at which the securing means (14, 16, 37, 38) are applied to the paperboard are reinforced by chemical treatment of the paperboard.

2. A container as claimed in claim 1, in which the adhesive is selected from one or more of vegetable adhesives such as starch, dextrins, gum arabic and tragacanth; cellulosic adhesives such as methyl cellulose, ethyl cellulose and cellulose acetate; thermoplastic resins such as polyvinyl acetate, polyvinyl butyral, polystyrene and acrylic resins; thermosetting resins such as phenol-aldehyde, urea-aldehyde and polyurethane resins; rubber adhesives such as rubber latex in a solvent; and inorganic adhesives such as sodium silicate.

3. A container as claimed in claim 1 or claim 2, in which the chemical treating agent is selected from one or more of plasticised or unplasticised polyvinyl acetate homopolymer, polyvinyl ethylene copolymer, polyethylene wax, styrene butadiene copolymer, polyvinyl alcohol, methacrylate copolymers, plasticised or unplasticised vinyl acetate copolymers, ethylene acrylic acid copolymer, mineral wax, natural wax, aqueous polyethylenimine, cationic polyacrylamide, aqueous poly(amidoamine - epichlorohydrin) , aqueous acrylic ester copolymers, aqueous styrene butadiene copolymer, aqueous acrylonitrile, starch and cellulose ether.

4. A container as claimed in any preceding claim, in which the securing means includes a two-component, separable, non-adhesive coupling (14, 16), which components co-operate to hold the container (2) in position for filling, storage and transport while filled, and are releasable to permit its emptying and collapsing when empty.

5 A container as claimed in claim 4, in which the coupling is of the type sold under the trademark 'Velcro ', of which each component is made from fabric, having one component (14) with a looped pile while the other component (16) has a hooked pile.

6. A container as claimed in claim 4, in which the coupling is made from moulded plastics material of which the two components may be latched together.

7. A container as claimed in any of claims 1 to 3, in which the securing means is adhesive tape (37, 38).

8. A container as claimed in claim 7, in which the adhesive is a "low-tack" adhesive.

9. A container as claimed in claim 7 or claim 8, in which the adhesive tape is provided with a tab (39) at one or more ends so as to facilitate removal of the tape from the container (30) .

10. A container as claimed in any of claims 6 to 8, in which the chemical treating agent function as a release coating on the paperboard.

11. A container as claimed in any preceding claim, in which the quantity of chemical treatment agent applied is absorbed into the structure of the paperboard to a depth of one-third to one-half of its thickness.

12. A container as claimed in any preceding claim, in which the chemical treating agent is applied to the parts of the paperboard in the vicinity of its intended points of contact with the coupling components (14, 16) or adhesive tape (37, 38).

13. A container as claimed in claim 12, in which the chemical treating agent is applied to a region (15, 35, 36) which includes the area of contact with the securing means plus a border zone around the said area.

14. A container as claimed in claim 13, in which the border zone preferably has a width of 5 to 25 mm around the whole periphery of the said area of contact.