GB2298424A - Composite foam building material - Google Patents

Abstract

A lightweight thermally insulating building material is formed from a lightweight thermally insulating filler disposed within a rigid foamed plastics matrix. The filler is preferably expanded polystyrene bead, and the matrix is preferably formed from rigid foamed polyurethane. The filler occupies at least 80%, preferably at least 90%, more preferably at least 95% and most preferably between 95% and 98% by volume of the finished material. The material is formed by mixing the bead with the foamable plastics material and allowing the material to foam and set. The material may be sprayed on a surface, or may be placed in a mould, which is then closed, before the foaming takes place. Coatings may be applied to the material by placing them in the mould beforehand, so that they become integrated with the material.

Description

BUILDING MATERIAL The invention relates to a building material, and more particularly to a lightweight, thermally insulating building material.

It is already known to form panels for use in building from plastics materials. In one known form, a panel is simply formed as a solid sheet of plastics material, for example an extrusion. However, these panels tend to be fairly heavy, due to the density of the plastics material, and their thermal insulating capacity is poor. In addition, as a considerable amount of plastics material has to be used in forming the panel, they are expensive.

Further known panels are formed from a foamed plastics material, such as polystyrene or polyurethane.

These panels are much less dense than an equivalent solid panel, and have enhanced insulating capacity, but they can still be relatively expensive, and, particularly in the case of polystyrene, weak.

To form a panel from foamed polyurethane using a typical two-component system, a resin is mixed with an isocyanate, and the mixture is then introduced into a mould which is then closed. The foaming reaction takes place inside the mould, and the volume of the plastics material increases. Once the volume becomes equal to that of the mould, the foam is compressed against the mould, and this increases the strength of the panel. In order to provide a high-strength panel, it is necessary to allow for a lot of compression of the foam, which leads to the use of a large amount of polyurethane, an expensive material. Furthermore, as the foam is compressed to provide high strength, the density of the foam would be such that the thermal insulation properties would be very poor.Further, this method must be carried out quickly as it is necessary to introduce the mixture into the mould within around 40 seconds of mixing, before the foaming reaction starts.

Another known method of forming a panel from foamed plastics material is to use expanded polystyrene beads, which are placed in a mould and subjected to steam heating. This softens the beads, and they coalesce to form a panel. Such a panel is fairly light but not particularly strong, and since the volume of the panel is reduced as the beads coalesce, this method also needs a large amount of starting material.

It would be advantageous to provide a building material that is strong, lightweight and thermally insulating, and does not require large amounts of starting material.

According to a first aspect of the invention, there is provided a lightweight, thermally insulating building material, comprising a lightweight thermally insulating filler contained within a rigid foamed plastics matrix.

Such a material has the principal advantage of using less material than a material formed from a single component, and thus reduces the cost of the material.

Less plastics material is used to form the matrix than would be required to form a panel made exclusively from a foamed plastics material. Similarly, less filler material is required then would be needed if the panel were to be made exclusively from the filler material.

Further, the material can combine in an extremely advantageous manner the thermally insulating qualities of the filler with the physical strength of the plastics matrix.

The rigid foamed plastics matrix is preferably a rigid foamed polyurethane, although other rigid foamed plastics material would also be suitable.

The filler preferably constitutes at least around 85%, preferably at least around 90%, more preferably at least around 95 and most preferably around 95 to 98k of the volume of the finished material. The percentage weight of the filler is preferably in the range 15-40t.

The filler is preferably expanded polystyrene, although other lightweight fillers, such as vermiculite, perlite, lytag and pulverized fuel ash, may be used. If expanded polystyrene is used, it is preferably in the form of beads or granules. Preferably the filler particles have a mean diameter of between 0.3mm and 4mm, more preferably of between 0.3mm and imam. The bead size can be selected to vary the physical qualities, such as strength and density, of the finished material. In general the larger the filler particle size, the weaker the material will be.

The invention also extends to a method of making a building material. According to a second aspect of the invention, therefore, there is provided a method of forming a lightweight thermally insulating building material, including the steps of mixing a lightweight thermally insulating filler with a foamable plastics material, and allowing the foamable plastics material to foam and set.

Preferably, the mixture is introduced into a mould, the mould is closed, and the foamable plastics material is allowed to foam and set in the mould. The mixture may, alternatively, be sprayed or otherwise applied onto a surface and allowed to foam and set in situ.

Preferably, the foamable plastics material is formed from a two-component system, and the filler is first mixed with one of the components only, before the second component is mixed in. Preferably, the filler is first mixed with the more viscous of the components.

Preferably, the foamable plastics material is a polyurethane formed from a resin and an isocyanate, and the filler is first mixed with the resin, before the isocyanate is mixed in.

Facings or coatings may be applied to the material by introducing the facing or coating into the mould before the mixture is introduced into the mould, so that the facing or coating becomes moulded onto the material.

Alternatively, the facing or coating may be applied after moulding. It is also possible to add reinforcement materials such as metallic meshes to the mould so as to produce an integral reinforced material.

The method can be used to form articles of any shape or size, limited only by the ability to provide a mould as necessary, and the invention extends to articles such as building panels, blocks and the like formed from the material of the invention, or by the method of the invention.

Preferred embodiments of the invention will now be described by way of example only, and with reference to the accompanying figures, in which: Figure 1 shows a cross-section through a first material according to the present invention; and Figure 2 shows a cross-section through a second material according to the present invention.

In one particularly preferred embodiment, the building material is formed from a two-component polyurethane system, comprising a resin component and an isocyanate component, and a filler formed from expanded polystyrene beads. Two-component rigid polyurethane systems are well-known in the art, and further details need not, therefore, be given here. However, typically the resin is a polyol blend and the isocyanate is a mixture of diphenylmethane diisocyanate and polymeric components. In this case, the rigid polyurethane used is a variety available from Baxenden Chemicals Limited of Baxenden, Lancashire, UK under the trade name "Isofoam RMDP 8478".

To form the material, the polystyrene beads are first mixed with the resin component. The resin component is much more viscous than the isocyanate component, and as the components start to react when they are mixed together, it is important to ensure that the best possible mixing is obtained before the foaming reaction gets under way. For this reason, it is preferred to mix the beads with the resin, as it has been found to be more difficult to mix a thick component into a thinner one than it is to mix a thin component into a thicker one. Mixing the beads with the resin helps to ensure that the beads are evenly covered with the resin, which in turn helps to ensure that the finished material is more homogenous, and avoid hollow patches where the resin has not contacted the beads.

Once the resin and the beads have been mixed, the isocyanate is added and mixed in. The mixing procedure preferably takes place at ambient pressure and temperature, but if necessary can take place at higher temperatures and/or pressure.

As the components will begin to react after mixing, the mixture must be transferred to the mould as soon as possible. However, it has been found that introducing a filler in the polyurethane slows the foaming reaction time. Without a filler, the mixture must be put into the mould within about 40 seconds, but with a filler this time is extended to 2 to 4 minutes. This facilitates the moulding process. If necessary, the reaction time can be reduced by heating the mould.

It is also possible to simply mix the beads, resin and isocyanate in a single mixing step, if desired.

The mould with the mixture in it is closed, and the foaming reaction allowed to proceed. As discussed above, once the volume of the foam is the same as the volume of the mould, any further foaming will compress the foam in the mould, and this will increase the strength of the finished material. However, the filler material maintains the thermal insulation of the panel even at high compressive strengths.

Coatings, facings, reinforcements and the like can be placed in the mould before the mixture is introduced.

For example, plastics or metal members, such as corrugated sheets and the like, can be placed in the mould, and the material will adhere to them during the moulding process. Alternatively, the coating, sheeting or the like can be applied, for example bonded, to the finished material.

The material may also be used as a spray-on insulator. The mixture of beads, resin, and isocyanate is sprayed (either as a pre-mixture or so as to mix during spraying) onto a surface to be insulated, and allowed to foam and set. If the material is used in this manner, it will not be particularly strong, as the strength of the panel described above results from the pressure exerted by the mould on the foaming plastics.

However, this may not be an important consideration if insulation is the overriding requirement.

The use of a filler contained within a foamed plastics matrix reduces the cost of the material. Less plastics material is used to form the matrix than would be required to form a panel made exclusively from a foamed plastics material. Similarly, less filler material is required then would be needed if the panel were to be made exclusively from the filler material.

The filler can also include an acoustic insulator if necessary. Further additives can also be introduced into the filler to tailor the properties of the material, for example to increase its fire resistance.

The thermally insulating qualities of the material come principally from the thermally insulating filler, although there is also a contribution from the voids in the foamed plastics matrix. Expanded polystyrene is an extremely good thermal insulator, and is relatively inexpensive. Further, a panel formed of the material with expanded polystyrene as a filler is easy to cut with a circular saw or similar tool, enhancing the workability of the material. Screws can also be put into the material in much the same manner as wood.

Examples of materials according to the invention, formed from a two-component foamed polyurethane matrix and expanded polystyrene bead filler by a method as described above, will now be described.

Example 1 Resin 85g 32.7% by weight Isocyanate 85g 32.7% by weight EPS Bead 90g 34.6% by weight The average bead diameter is around 4mm, made up of around 80% of diameter 4mm or above, 10% of diameter between 2mm and 4mm, and 10% of diameter 2mm or less.

The material is produced in a closed mould, having dimensions of 300mm by 300mm by 50mm. The finished material has a density of between 30 and 50 kg/m3, with the polystyrene forming about 95% by volume of the material.

Example 2 Resin 200g 40.8% by weight Isocyanate 200g 40.8% by weight EPS Bead 90g 18.3% by weight The average bead diameter is around 1.5mm, made up of around 80% of diameter between 1.5 and 2mm, and 20% of diameter between 0.5 and 1.5mm.

The material is produced in a closed mould, whose dimensions are the same as those used in Example 1. The finished material has a density of around 100 kg/m3, with the polystyrene forming about 95% by volume of the matrial.

Example 3 Resin 350g 36.4% by weight Isocyanate 350g 36.4% by weight EPS Bead 262g 27.2% by weight The average bead diameter is around 0.3mm, made up of around 80% of diameter between 0.3mm and 0.5mm, and 20% of diameter 0.3mm or less.

The material is produced in a closed mould, whose dimensions are the same as those used in Examples 1 and 2. The finished material has a density of around 200 kg/m3, with the polystyrene forming about 95% by volume of the material.

In each of the above examples, the size of the mould was 300mm by 300mmm by 50mm.

It will be seen from the above examples that small beads give higher densities of the finished material.

The density of the finished material can be controlled by varying the bead size. Varying the bead size also varies the strength and thermal insulation abilities of the material.

Typical cross-sections of the materials in Examples 1 and 3 are shown in Figures 1 and 2 respectively.

The material shown in Figure 1, made from expanded polystyrene beads 1 in a foamed polyurethane matrix 2, has a density of approximately 30 kg/m3, and an average bead diameter of around 4mm. It will be seen that the beads are fairly well spaced from each other, creating voids 3 in the structure. The beads are held in position by the foamed polyurethane, which coats their surfaces and causes them to adhere to each other, but does not fill the spaces between them. This material has very good thermal insulating qualities, but is relatively weak. It is therefore not well suited for use as a structural building material by itself, but it can be used as non-structural panels, for example, or can have facings such as plasterboard applied to it to form insulating building panels.

The material shown in Figure 2, also made from expanded polystyrene beads 4 in a foamed polyurethane matrix 5, has a density of approximately 200 kg/m3, and an average bead diameter of around 0.3mm. The beads are much more closely packed in this material, with the spaces between them substantially filled with the foamed polyurethane. The thermal insulating qualities of this material are not quite as good as those of the material shown in Figure 1, but this material is much stronger.

It has been found that the material will retain screws which are screwed into it in the same manner as wood.

Physical tests carried on the material of example 3, with a density of around 200 kg/m3, gave the following results: Thermal conductivity 0.037 w/mK Compressive strength : 1.84 N/mm2 to 2.20 N/mm2 These properties can be varied by varying the size of the beads used and the relative proportions of the filler and the foamed plastics matrix. To produce a material having similar strength using foamed polyurethane alone would require at least 2 to 3 times the weight of polyurethane, and the material would have poorer thermal insulation qualities. Furthermore, to obtain a polystyrene material having similar thermal insulation characteristics would require 40k more polystyrene, but this material would have little strength.

The material of the invention has considerable advantages over known materials. It is substantially cheaper than known materials of similar strength, and is also thermally insulating. Since it can be provided with coatings such as plastics profiles, plasterboard, metallic mesh and sheeting and the like, it is particularly versatile, and can be used in a wide range of building applications. The material can also be glued, heat welded or otherwise bonded to itself or other materials in the same way as plastics materials.

Furthermore, in order to obtain adequate thermal insulation properties, polyurethane must frequently be foamed with potentially environmentally harmful CFC's and HCFC's. The present invention obviates the need for such products.

The material can be used to make a large variety of items, such as building panels, insulation panels, decorative mouldings, heavy duty packaging, underfloor and roofing insulation, pipe and cable insulation, boundary fencing, moulded bath and water tank insulation, moulded fish ponds, cold store insulation, panels for caravans, and cavity closures, for example for double glazing. An example of the latter is shown in Figure 2. Furthermore, the material can be painted, veneered or rendered with a concrete or plaster slurry to provide a desired surface finish.

Claims (20)

1. A lightweight, thermally insulating building material, comprising a lightweight thermally insulating filler contained within a rigid foamed plastics matrix.

2. A material as claimed in claim 1, wherein the rigid foamed plastics matrix is formed from polyurethane.

3. A material as claimed in claim 2, wherein the polyurethane is formed from a resin component and an isocyanate component, the resin component comprising a polyol blend and the isocyanate component comprising a mixture of diphenylmethane diisocyanate and polymeric components.

4. A material as claimed in any preceding claim, wherein the filler occupies at least around 85%, preferably at least around 90, more preferably at least around 95% and most preferably around 95% to 98% of the volume of the material.

5. A material as claimed in any preceding claim, wherein the filler is expanded polystyrene.

6. A material as claimed in claims 4 and 5, wherein the filler forms between 15% and 40% by weight of the material.

7. A material as claimed in any preceding claim, comprising a facing or reinforcement integrally formed therewith.

8. A method of forming a lightweight thermally insulating building material, including the steps of mixing a lightweight thermally insulating filler with a foamable plastics material, and allowing the foamable plastics material to foam and set.

9. A method as claimed in claim 8, wherein the mixture of thermally insulating filler and fdamable plastics material is introduced into a mould, the mould is closed, and the foamable plastics material is allowed to foam and set in the mould.

10. A method as claimed in claim 8, wherein the mixture of thermally insulating filler and foamable plastics material is sprayed or otherwise deposited onto a surface and allowed to foam and set in situ.

11. A method as claimed in any of claims 8 to 10, wherein the foamable plastics material is formed from a two-component system.

12. A method as claimed in claim 11, wherein the filler is first mixed with one of the components only, before the second component is mixed in.

13. A method as claimed in claim 12, wherein the filler is first mixed with the more viscous of the components.

14. A method as claimed in any of claims 8 to 13, wherein the foamable plastics material is a polyurethane formed from a resin and an isocyanate, and the filler is first mixed with the resin, before the isocyanate is mixed in.

15. A method as claimed in claim 8, or any claim appendant thereto, wherein a coating or facing is applied to the material by introducing the coating or facing into the mould before the mixture is introduced into the mould, so that the coating or facing becomes integrated with the material.

16. A method as claimed in claim 8 or any claim appendant thereto in which a reinforcement is placed in the mould.

17. An article formed from a material as claimed in any of claims 1 to 7, or formed by a method as claimed in any of claims 8 to 16.

18. An article as claimed in claim 17, wherein said article is a building panel.

19. A lightweight thermally insulating building material, comprising polystyrene beads contained within a rigid foamed polyurethane matrix, the polystyrene beads constituting between 95 and 98% of the material by volume and between 15 and 40% by weight.

20. A lightweight thermally insulating building material, comprising polystyrene beads contained within a foamed polyurethane matrix.