BUILDING MEMBER

Abstract: A building member (1) comprises a load bearing element (4, 6) comprising a strip of compressed mineral wool having a density of at least 50 kg/m<3>. The load bearing elements may form a frame element of a wall panel which further comprises a central insulating zone (9) of relatively less compressed mineral fibre, facing layers of sheet material and (2, 3) extending across the surface of the panel and sandwiching the mineral fibre load bearing element. The facing layers are bonded to the load bearing elements, and, if desired, the insulation in the central zone, using bonding agent which cures whilst the sandwich of materials is subjected to compression, for instance whilst being vibrated.

Description: BUILDING MEMBER The present invention relates to the use of a compressed mineral fibre strip as a structural element, for example for use in a prefabricated building. A wall panel for a prefabricated building is required to have heat insulating properties, be economical and, especially if it is required to act as a support for upper storeys or for the roof, to have adequate characteristics of tensile and compressive strength. Usually, these characteristics of strength are provided by separate beams or elements in the wall panel which are made of wood or metal. Mineral fibre, for instance, rockwool or glass wool is a well known insulator. Low density batts, for instance up to 50 kg/m 3 usually around 20 kg/m 3 , have been fitted within various building panels such as wall units for prefabricated or other buildings. Batts of mineral fibre of higher densities have been used in some applications. Usually the batts are used in combination with load bearing members that support any vertical load that has to be supported. Thus the batts can be used as, for instance, in-filling between concrete, brick, wooden or metal columns or within a load bearing framework of, for instance, wood. In instances where no significant load is to be applied along the length of the batts (for instance as roofing or ceiling ne-is) they have been used alone, i.e. without lengthwise load bearing members. CH-A-649803 discloses a sheet insulating element comprising a frame of relatively compressed fibrous material surrounding an area of insulating material which may also comprise fibrous material which may also comprise fibrous material. The fibres of the material used for the frame are arranged perpendicular to the plane of the sheet. The element comprises only the fibrous frame and insulating material inside the frame. The frame is said to be capable of bearing loads directed perpendicularly to the sheet. US-A-4490955 discloses structural wall panels comprising moulded fibrous material and binder shaped to cover the entire area on one side of the panel and having frame components along opposite vertical sides into which are moulded longitudinal recesses for receiving wood or metal structural elements. The area between the vertical fibrous frame elements may be filled with insulating material and a sheet of gypsum board or dry wall may be fitted across the panel on the side opposite the side covered by moulded fibrous material using nails or screws attached to the wood or metal strips. A facing layer may also be fixed across the moulded fibrous layer and held in place by screws or nails fixed into the wood or metal strip The fibrous material has a density in the range about 100 to 300 kg/m 3 . EP-A-0396306 discloses a sandwich panel element comprising a mineral wool core sandwiched between and bonded to sheet material skins. The mineral wool core is formed of elongate strips of mineral wool arranged side by side, the longitudinal direction of the strips being the horizontal when the panel is in use. The fibres of the mineral wool extend generally transverse to the planes of the sheet material skins which is said to improve adhesion of the core to the sheets. The panels may be provided with securing elements for attachment to a separate support structure. WO-A-8706966 discloses an acoustic and thermal insulation panel comprising a frame of fibre-reinforced inorganic binder (such as cement or calcium silicate) surrounding a batch of mineral fibres in which the fibres may be partially immobilised by adhesive. The panel also comprises lamina of reinforced inorganic binder, metal sheets and facing sheets and the components are adhered together using a fire resistant adhesive. A building member according to the invention is selected from panels, corner pieces, posts and struts and comprises mineral wool and is characterised in that it includes a load bearing element that comprises a strip of compressed mineral wool having a density of at least 50 kg/m . The invention includes the new use, as a structural element, of a compressed mineral wool element having a density of at least 50, preferably at least 100, kg/m 3 . By referring to use as a structural element, it is meant that the element is load bearing in use, and normally it is load bearing in a substantially vertical position. The mineral fibre element should have a density of at least 50 kg/m , preferably at least 100 kg/m and often at least 120 kg/m . Usually the density is less than 200 kg/m . The most preferred density range for the element is 120-180 kg/m 3 . The mineral wool may be rockwool or slag wool, but is preferably of glass wool. Glass wool fibres tend to be longer than fibres of rockwool and elements made from it tend to be correspondingly stronger for the same density or degree of incorporation of binder. Preferably the fibres are arranged predominantly across the thickness of the strip, ie transverse to the load. The mineral fibre element used in the invention preferably comprises a strip of material, for instance having a generally rectangular cross section and being elongated. The strip is often used in its load bearing capacity such that it extends in a substantially vertical direction. The strip usually has a cross section with dimensions of at least 20 mm, preferably at least 25 or 30 mm in each direction. Preferably the greater dimension of the cross section is at least 50 mm and often at least 60 or 70 mm, for instance around 80 mm. It can however be larger, for instance up to 100 mm, or even 150 mm. Often the strip has a rectangular cross-section with a lesser dimension of from 10-100 mm and a larger dimension of from 50-150 mm. The strip should be formed mainly of the compressed mineral wool fibre but it must contain some bonding agent, and typically it contains more than 70% by weight mineral wool fibres and up to 30% by weight bonding agent, most preferably 80-95% by weight mineral wool fibres and 5-20% by weight bonding agent based on the total amount of bonding agent in the wool. Generally bonding agent is applied to the wool both during manufacture of the wool itself and in the manufacture of the structural element from the wool, for instance during its incorporation into a building member. The amount of bonding agent incorporated during manufacture is usually in the range 3- 30% by weight, more often in the range 5-20% by weight, for instance between 8 and 15% by weight based on the total weight of preformed wool. Extra bonding agent can thus be applied to a strip of pre-formed mineral wool (which contains some bonding agent throughout its volume) , generally by application to one or more of the outer surfaces of the strip and migration of the bonding agent towards the centre. Accordingly the amount of bonding agent in the zone adjacent the face(s) to which bonding agent is applied is significantly more than the amount of bonding agent at the central zone of the strip. Preferably the strip is sandwiched between and bonded to layers of sheet material. The bonding of the strip to the sheet material, and the distribution of bonding agent within the strip, is best achieved by applying liquid bonding agent between the sheet material and an adjacent surface of the strip and then compressing the sandwich of sheet materials and strip and curing the bonding agent. This compression may raise the density of the strip to the desired final value. Preferably the curing is conducted using high frequency welding techniques since these promote the migration of the liquid bonding agent into the central zone of the strip. The building member is of particular use as a component of a prefabricated building, for instance as a wall panel, ceiling panel or roof panel. Although the building member is preferably a panel, the invention also includes building members that are struts, posts or corner pieces. The invention is of particular use in a wall panel where it is required to bear substantially vertical loads. When used in a panel, the element is generally in the form of a preformed strip which extends, for instance along any or all of the edges of the panel or lies adjacent the panel edges. In a wall panel, for instance, the strips of compressed mineral fibre preferably extend along the longitudinal edges, namely the edges which stand in a substantially vertical position in use. Strips may also extend along the substantially horizontal edges. Additional strips may be provided for added strength which extend in a substantially vertical position when the wall panel is in use, for instance mid-way between the two vertical edges. The strip is usually sandwiched between a pair of sheet elements that can either be panel facing elements or facing elements for a strut or corner piece and is preferably adhered to the sheet elements by curing the bonding agent whilst the components are under compression. The bonding agent is preferably one which is water and weather resistant, suitable agents being known in themselves. The bonding agent is generally organic-based although it may comprise some inorgsnic material. The bonding agent is preferably used in the production of the building component of the invention in the form of a curable liquid. The bonding agent is applied to adjoining surfaces of the building component prior to their being joined together. It may be supplied as a continuous film to one or both surfaces, usually it is applied discontinuously for instance as strips. Most often it is applied to the surface adjoining the mineral wool strip and not to the strip itself. Particularly advantageous properties are achieved if the components are subjected to vibration during compression since this allows the liquid adhesive to become dispersed in the mineral fibre element. Dispersion of bonding agent is improved still more if the liquid, curable bonding agent is foamable and is caused to foam whilst the compression and vibration is being carried out. Preferably the bonding agent and the curing process are such as to allow the bonding agent to penetrate at least 1mm and up to 10mm into the mineral wool, for instance 2-5mm. The extra bonding agent is, for instance, applied at a rate in the range 1-50 g/m of adjoining surface area, preferably in the range 2-20 g/m , more preferably in the range 2-10 g/m 2 . One suitable bonding agent is a liquid polyurethane adhesive which is caused to foam on contact with water. The bonding agent is conveniently applied as stripes onto the surface of the element to be bonded to the mineral wool strip, is then sprayed with water before assembly and compression in a heated vibrating press. Curing may be carried out at raised temperature, for instance of at least 40°C, preferably at least 50°C, for instance up to 70 or 80°C. The curing by compression, vibration and/or heating may be carried out for a period of a few minutes up to several hours. Usually a period of less than one hour is adequate and often less than 30 or 20 minutes allows sufficient curing and migration of the adhesion. The sheet material used as facing elements, eg to form a panel according to the invention, can be, for instance, of wood, usually plywood, plastics, plasterboard or metal. The space between the pair of sheet materials is generally not completely filled by the dense mineral fibre element, as these need only form strips adjacent the edges of a panel. Preferably, for optimal heat and sound insulation, that space may be filled by insulating material, for instance comprising a sheet or sheets of lower density mineral fibre. The density of such material is for instance less than 40 or 30 kg/m . A pair of such sheets with an airgap between them for sound insulation is of particular utility. These insulating elements may be bonded to some of the other elements of the panel, for instance by application of liquid bonding agent between opposing surfaces prior to assembly and curing of the bonding agent for the structural fibre element. Usually, however it is unnecessary for the insulation to be bonded within the panel. The dense mineral fibre strip of a panel may extend to some or all of the edges of the panel. The panel may be formed by sandwiching the strip or strips of mineral fibre between a pair of sheet components, such that the strip extends beyond the edge of one or both sheets and subsequently trimming the strip to the desired size. The trimming operation may include the provision of a machined profile 1 in the edge of the mineral fibre strip which is of utility in the subsequent application of the panel. For instance the profile may be for co-operation with other components of a prefabricated building, such as the foundation, corner units, door or window units, ceiling or roof units. If desired, edging elements of wood or plastics may be inserted outside the strip of compressed mineral wool fibre so as to provide a weather proof edge to the building member. Generally, however, this is unnecessary and the strip of compressed mineral wool, usually including bonding agent, can provide an accurately machined outer edge to the building member. The building members of the invention are of particular value in the construction of prefabricated buildings of the general type described in my copending applications publications WO-A-90/03477 and WO-A-90/03475, the contents of which are incorporated herein by reference. The building member of the present invention thus preferably constitutes a wall panel which co-operates with the components of a prefabricated building described in those two publications. In another preferred aspect, the building member of the present invention is a corner piece that may be formed solely of the strip of compressed mineral wool or may be formed of two vertical strips interconnected by a corner piece of facing panels or other suitable material. In order to provide a weather proof seal between adjacent building members of the present invention, a strip of mastic may be sealed between adjacent edges of adjacent building members (often between adjacent edges of adjacent strips of compressed mineral wool) . Instead of or in addition to providing mastic, a tongue and groove configuration may be provided between adjacent edges either by having a groove in each adjacent edge with a strip of material filling the adjacent grooves, or by having a projection on one edge fitting within a groove in the adjacent edge. One embodiment of the invention is further illustrated in the accompanying drawings in which : Figure 1 is an isometric schematic diagram of one corner of a wall panel from the front and one side; Figure 2 is a section along line II-II of figure 1; and Figure 3 is a section along line III-III of figure 1. A wall unit 1 comprises a pair of sheets 2, 3, for instance formed of plasterboard or plywood, in this embodiment one being formed of each of those types of material. Between the sheets is fixed a strip of mineral fibre material 4 which extends along the bottom horizontal edge of the panel. A similar strip extends along the top horizontal edge of the panel. Into the strip 4 a groove 5 is machined which, in use, co-operates with a ridge, provided for instance in a foundation beam of the building, or, where the strip is at the top edge of the panel, with roof components. The strip is formed of fibre glass, having a density of 125 kg/m . There is also provided between the sheets a strip of mineral fibre material 6 adjacent the vertical edge of the panel. There is a similar strip extending between the sheets at the other vertical edge of the panel and also midway between the edges. These vertical strips are formed, for instance, of the same material as the horizontal strip 4, that is 125 kg/m 3 density glass wool. In order for the strips of mineral fibre to have optimal strength they are preferably cut so that the fibres lie in a direction extending along the longer dimension of the strips section. The strips in this preferred embodiment have a cross sections of about 40 by 80 mm. The vertical strips have extremely favourable load bearing capabilities. Between the sheet materials at the very edge of the panel there is provided a vertical strip of wood 7. This strip has a groove 8 machined into its outward surface which co-operates, as groove 5, with another component of the building. In the space between the sheet materials not taken up by the high density mineral fibre strips there is provided insulating material 9, which acts to insulate against nose and/or heat transmission. In the preferred panel the insulating material comprises a sheet of low density (eg around 20 kg/m 3 ) mineral wool. For optimal noise insulating a pair of sheets of low density mineral wool are used with an intervening air gap. In the panel the sheet materials 2, 3 and the strip materials 4, 6, 7 are held together by the provision of adhesive at their adjoining surfaces. The panel is produced by assembling the components with liquid curable adhesive. In the preferred embodiment the liquid bonding agent comprises a foamable polyurethane. It is applied to the plasterboard and plywood sheets 2, 3 in stripes at the areas where the sheets contact the strip materials 4, 6 and 7 only. It is applied at an overall rate of about 2-3 g/m 2 surface area. The polyurethane is caused to foam by being sprayed with water and the components are then assembled and placed into a high frequency vibrating press. This may be carried out in a heated press of known type conventionally used for high frequency welding, for instance of wood components. For the polyurethane bonding agent it has been found suitable to effect the pressure over a period of, for instance, 10-20 minutes for instance about 17 minutes, whilst heating the materials to a temperature between 50 and 60°C.

Claims: CLAIMS 1. A building member comprising mineral wool characterised in that it includes a load bearing element that comprises a strip of compressed mineral wool having a density of at least 50 kg/m . 2. A member according to claim 1 in which the compressed mineral wool has a density of 100-200 kg/m 3 , preferably 120-180 kg/m 3 . 3. A member according to claim 1 in which the fibres of the mineral wool are arranged predominantly transverse to the direction of load bearing. 4. A member according to any preceding claim in which the strip has a cross-sectional area of 20-100 mm by 50-150 mm. 5. A member according to any preceding claim in which the strip is formed from 70-100% by weight mineral wool fibres and 30-0% by weight bonding agent, preferably 80-95% by weight mineral fibres and 20-5% by weight bonding agent. 6. A member according to claim 5 in which the strip is sandwiched between and bonded by bonding agent to facing layers of sheet material, and the fibres are arranged predominantly to extend across the thickness of the strip between the layers of sheet material. 7. A member according to claim 6 in which the strip comprises bonding agent applied during manufacture of the wool and which is dispersed throughout the strip's volume and also extra bonding agent which is located primarily adjacent to the surface of the sheet material to which the strip is bonded. 8. A member according to claim 7 in which the bonding has been achieved by applying liquid bonding agent between each sheet and the adjacent surface of the strip assembling the sandwich of sheet-strip-sheet and then compressing the sandwich and curing the bonding agent. 9. A member according to claim 8 in which the curing is by high frequency curing. 10. A member according to claim 8 or 9 in which the density of the strip during the assembly is less than the final density in the building member and the compression raises the density to the final density. 11. A method of making a member according to any of claims 6-10 in which bonding agent is applied to surfaces of the sheet materials adjoining the strip, the components are assembled to form the sandwich and the bonding agent is cured under compression. 12. A method according to claim 11 in which the compression is carried out whilst heating and/or subjecting the sandwich to high frequency vibration. 13. A method according to claim 11 or 12 in which the bonding agent is a liquid, optional foamable, adhesive. 14. A building panel according to any preceding claim that comprises at least two of the said load bearing elements each extending along a longitudinal edge of the panel, and the faces of the panel are formed of panel facing material that is bonded to the strips. 15. A prefabricated building formed from one or more building members according to any preceding claim as wall panels or corner pieces or struts or posts. 16. Use of a strip of compressed mineral wool having a density of at least 50 kg/m 3 , preferably 100-200 kg/m as a load bearing element in a prefabricated building.

Inventors: LARSEN PETER WIMMELMANN, LARSEN, PETER, WIMMELMANN
Applicants: JONES HELEN MARJORIE MEREDITH, WIMMELMANN LARSEN PETER, JONES, HELEN, MARJORIE, MEREDITH, LARSEN, PETER, WIMMELMANN
Application year: 1991
Main classification: E04C2
IPC codes: E04C2