GB2103567A - Improvements in packaging - Google Patents

Abstract

A packaging method involves introducing into the interspace between a container and an object to be packaged a plurality of energy absorbing, e.g. polystyrene, particles. At least some of the particles are coated with a heat activatable adhesive which is warmed and allowed to set to bond the particles together to form a coherent package.

Description

SPECIFICATION Improvements in packaging This invention relates to the packaging of objects particularly fragile objects, awkwardly shaped objects and heavy high density objects in rigid outer containers for storage and/or transport. The invention deals with the creation of a resilient barrier between the exterior of the objects and the interior walls of the outer rigid container.

Various proposals have been made for creating this barrier. For example: 1) By linking the object to the walls by separately attached elastic members, e.g.

springs or elastic bands or textile strips. This procedure is costly.

2) By packing the space between the object and the walls with resilient units or granules; this packaging is not stable and the object can settle through the packing by vibration in transit.

3) As (2) but developed shapes of granules so as to interlock one with the other. Again this procedure is rather costly and difficult to pack and still rather unstable.

4) Elastic foam cast in situ by chemical reaction, e.g. polyurethane. This procedure is costly and involves handling multicomponent chemical systems with at least one dangerously toxic substance. There are considerable problems in keeping the object submerged during foaming operation because of upthrust.

According to the present invention there is provided a method of packaging an object in a container such method comprising the step of introducing into the space between the container and the object a plurality of resilient energy absorbing particles, at least some of which are coated with a heat-activatable adhesive and activating the adhesive thereby causing the particles to adhere together into a solid mass.

The particles may be soft granules for example granulated scrap foamed plastics or the like.

This adhesive can be coated at low temper- ature by using a solution or, preferably, an emulsion in water applied to the granular material by conventional means, e.g. a rotating inclined vessel, and the water or solvent evaporated by a current of air. Alternatively the adhesive can be a wax, preferably a microcrystalline wax which is warmed and melted to apply it to the particles. The coated particles are then cooled to set the wax.

The resultant dry granules which are free flowiny and easy to handle and store can be introduced into the gap between objects by pouring. Once the gap is filled with granules the adhesives can be activated for example by blowing warm air through the bed of granules which promptly stick together. This can be achieved by blowing warm air down through one side of the pack and forcing the air to return up through the other side by introducing a septum or divider such as card or board roughly cut to the shape of the container and object. Otherwise the warm air can be introduced through perforations in the base of the outer rigid container.

In another procedure in accordance with the invention the granules are warmed, or maintained warm, prior to introduction into the container.

The adhesive can be activated by alternative means, for example by RF heating.

The following Examples illustrate the invention: EXAMPLE I Expanded polystyrene in the form of spherical beads was prepared by the customary hot water treatment of suspension polymerised styrene containing volatile solvent blowing agent. It was taken to its full degree of expansion in this manner so as to produce soft generally spherical resiliently flexible heads of maximum size (3-5 mm) and minimum density (20-25 grams per litre). A coating pan, otherwise known to the confectionary or pharmaceutical trades as a "sweetie barrel" was about one third filled with the polystyrene beads and set into rotation.The contents were warmed to about 60 C by the action of a hot air jet whereupon a sufficient amount of microcrystalline wax was added, as a slow stream of melt liquid at just above its melting point, to produce a very thin uniform coating over the surface of the beads. The hot air stream was replaced by a cold air stream and the rotation of the coating pan maintained until the wax had hardened yielding a free flowing product being lightly wax coated expanded polystyrene spherical beads.

The beads were applied to a packaging operation by part filling a traditional fibre drum with the spheres, placing on the surface of the initial layer the delicate article to be protectively packaged itself enveloped in a simple plastic film overwrap, and then completing the filling of the drum with the freely flowing beads. The packing process was completed by passing through the bed of beads a stream of preheated air generated conveniently by an industrial hot air blower combin ing a fan with electrical resistance heating elements. The air stream was introduced through a temporary aperture in the base of the drum and very rapidly raised the wax coating to its melting point because of the very low thermal conductivity of the expanded polystyrene beads and the fibre drum.As soon as the wax had softened sufficiently the hot air was replaced by cold air which rapidly caused the wax to solidify and lock the gran ules into a solid energy absorbing mass thus preventing the delicate packaged object from displacement during the subsequent move ments of the drum. Because of the low mechanical strength of the wax band it was very easy to break the granular mass away from the packaged article when so required. Of course the process could be reversed by reheating the granules if preferred.

A variation is to use the particles for packaging immediately after coating before the was is cooled and solidified. This avoids the need for the activating step after packaging.

Another convenient variation is to warm the particles to activate the adhesive immediately prior to packaging. Thus warmed particles are introduced into a container, the article placed in position and the container then filled with warmed particles which are cooled or allowed to cool to set as above.

EXAMPLE II Soft polyurethane foam crumb derived from the shredding of scrap or surplus upholstery products was classified by sieving to yield a reasonably uniform granular product of particle diameter between 5 and 10 mm diameter.

A suitable charge of this material was loaded into a coating pan and set into motion with simultaneous introduction of a stream of hot air. When the granules had reached a temperature of 30-40"C, polyvinyl acetate emulsion of flexible film forming quality and about 40% solids content was introduced into the pan by spraying at such a rate as to ensure the progressive creation of a uniform coating of polymer on the surfaces of the granules without undue penetration and without reducing the whole to a wet mass. When the granules were uniformly thinly coated the air supply was adjusted to provide cooling air and eventually a free flowing granular solid was discharged by tilting the pan further from its operating position. This product was applied as in Example I to fill the space between a fragile article and its outer box or drum. In this instance a simple card divider was inserted in the container during the filling operation so cut as to accommodate the fragile article amidships and to provide a port between the divided halves near the base of the container. By this means it was possible to introduce the hot air needed to soften the polyvinyl acetate coating of the granules by blowing downwards through an aperture in a temporary half cover to the container top ensuring passage of the hot air down one side of the drum, across through the low part in the dividing septum, and up through the other half, once again the effect was to bond the elastic granules into a firm bed of sufficient strength to avoid the possibility of the packaged object moving during transport but yet weak enough to be readily torn apart for unpacking purposes.

Claims (9)

1. A method of packaging an object in a container such method comprising the step of introducing into the space between the container and the object a plurality of resilient energy absorbing particles, at least some of which are coated with a heat-activatable adhesive and activating the adhesive thereby causing the particles to adhere together into a solid mass.

2. A method as claimed in Claim 1 wherein the particles are introduced into the said space with the adhesive inactivated.

3. A method as claimed in Claim 1 wherein the adhesive is a thermoplastic substance such as wax and is applied to the particles in melted form and is cooled to provide a dry packaging material.

4. A method as claimed in Claim 3 wherein the dry particles are warmed to melt the adhesive prior to introduction into the container.

5. A method as claimed in either Claim 1 or Claim 2 wherein the adhesive is applied to the granules by evaporation from a solution or an emulsion.

6. A method as claimed in any of the preceding claims wherein the particles are of resiliently flexible plastics material, for example foamed material.

7. A packaging method substantially as described in the Examples.

8. A package prepared by a method as claimed in any of the preceding claims.

9. A packaging material comprising a plurality of resiliently flexible particles at least some of which are coated with a heat activatable resin.