Field of the Invention

[0001] This invention relates to a building composition, for example for form- ing structural and decorative components, and in particular to materials which can be readily recycled for re-use when the building is no longer required. The composition can also be used to form packaging. The hardened composition is readily recyclable.

Background to the Invention

[0002] The use of waste and recycled materials as a filler for building materials is well-known. For example, power station ash has been used for the manufacture of building blocks, and recycled glass particles have also been used in building products. Typically, the binder used for these types of product has been cement-based or, more recently, resin-based. While these have proved generally satisfactory for some construction uses, they present a problem when the building is altered or demolished, because they typically require high-powered crushing machines to reduce the blocks and other components to particles for re-use or disposal.

[0003] Cavity wall insulation introduced into existing cavity walls is typically in the form of expanded plastics beads, for example polystyrene beads, which are carried into the cavity from a suitable injection point by a current of air. This enables the cavity to be filled from a relatively small number of injection points, minimising disruption to the building during the operation. While this method does afford a significant improvement in the insulative properties of the walls, it does have a disadvantage, in that when the building, or part of it, is demolished for redevelopment, this releases a large quantity of individual beads which can be carried readily by the wind to pollute the surroundings. While arrangements can be made to extract at least some of the beads before demolition takes place, this is a difficult operation, and is unlikely to remove all the beads, leaving some to escape when demolition takes place. [0004] A common problem in public places is the painting of graffiti on buildings and other structures. This requires considerable work, and therefore cost, to remove. It is known to provide coatings to make it more difficult for the graffiti to adhere to the surfaces, and therefore easier to clean off, but these coatings can adversely affect the appearance of the surfaces, particularly as the coatings age.

[0005] Expanded polystyrene and the like is extensively used in packaging materials, being light in weight and strong enough to provide protection to items during shipping. However, the disposal of packaging materials of this type cre- ates a considerable problem, because of its high volume, relative to its mass, and the difficulty in re-using the material. A large amount of the material therefore ends up in landfill, which is an increasingly costly means of disposal. It is also very slow to degrade, and if broken up can be carried by the wind and left in unsightly deposits.

Summary of the Invention

[0006] The present invention provides a building composition comprising a filler mixed with a hardenable binder which, when hardened, is soluble in water at elevated temperatures.

[0007] The binder may be thermosetting, or it may be an aqueous film- forming material. Alternatively, the binder may be caused to harden by the addition of a catalyst or by exposure to ultra-violet radiation (for thin films or components). The binder is preferably cellulose- or starch-based, or polyvinyl alcohol based, and curing of the binder may be effected using warm air or steam.

[0008] "Elevated temperatures", in the context of the invention, means tem- peratures in excess of normal ambient temperatures, and preferably in the range 50° to 90° C. The binder, when hardened, is not significantly soluble in water at ambient temperatures

[0009] The filler may be sand, or aggregate, or the like, or hollow beads. The hollow beads may be expanded polystyrene or other plastics, or glass or ceramic bubbles. The beads may have a mean size of up to 10mm, preferably below 5mm, for insulation applications, or very fine, with particle sizes less than 1 mnn, for surface coating compositions. Other possible filler materials included perlite or vermiculite, and comminuted waste glass. Fibres, for example of plastics, minerals or glass, may also be incorporated to improve the strength of the hardened composition [0010] The invention also provides building components formed by moulding a composition according to the invention, and allowing or causing the composition to harden. For example, the composition may be cast into blocks, and sheets may be formed if required by slicing the blocks. Alternatively, the composition may be extruded to form continuous lengths of any desired profile, the extruded material being cut to form sections of any desired length. Warm air may be used to hasten the hardening of the extruded material.

[0011] The composition may be used as a paint, for example as an anti- graffiti paint which can be removed from the surface, along with any graffiti, by the application of hot water. Alternatively, a composition of the invention may be used as a temporary mortar or concrete, or as a rendering or finishing coat applied by trowel or float to a wall or other building surface.

[0012] A method of cavity wall insulation may comprise injecting into the cavity a composition according to the invention comprising expanded plastics beads. A very light coating of the binder would be sufficient to hold the beads together in the event of demolition of the cavity wall, permitting the material to be recovered and treated with hot water to remove the binder and permit re-use of the beads. For example, the binder could be sprayed into the cavity with the polystyrene or other plastics beads, suitably from a separate nozzle within or alongside the nozzle conventionally used for injection of the beads.

[0013] It would also be possible to use the composition to form an external insulation layer on an existing building which does not have a cavity, either by attaching boards formed from the composition and containing expanded plastics beads or other hollow beads, to the outside surface of the building, or by spraying on the composition in slurry form and allowing it to harden. A protective layer of waterproofing material can then be applied in either case. [0014] Similarly, loft insulation could be achieved by the spraying of an insulating composition according to the invention. After hardening, the composition would be dust-free and stable, and the introduction into the composition of fire- inhibitors and the like would ensure its safety in use.

[0015] The use of cellulose- or starch-based or polyvinyl alcohol-based ad- hesives or the like means that the treatment of the hardened material with hot water to recover the beads does not produce any environmentally harmful residues; the wash water can be disposed of in the sewerage system without special treatment. [0016] The composition including hollow plastics beads may be moulded to form packaging materials for use in protecting products in transit, for example fragile products such as TVs and computer monitors. When the products are unpacked at their destination, the packaging can be treated with hot water to wash away the set binder, allowing the beads to be collected in bulk for re-use in further packaging. New binder can be added and the resultant composition moulded to provide custom packaging components. The re-usability of the beads could conveniently be indicated by manufacturing the beads with a suitable dye or pigment added, for example colouring the beads green.

[0017] The composition of the invention may be rendered fire-resistant by incorporating such materials as cement powder.