WO2002042576A1

WO2002042576A1 - A sound reducing board and a process for the manufacture of the board

Info

Publication number: WO2002042576A1
Application number: PCT/DK2001/000775
Authority: WO
Inventors: John Christian Asmussen; Claus Voigt Andersen
Original assignee: Rockwool International A/S
Priority date: 2000-11-24
Filing date: 2001-11-21
Publication date: 2002-05-30
Also published as: AU2002223516A1

Abstract

The invention relates to a sound reducing board for recuding sound of different level. The sound reducing board comprising two or more layers, a first layer in the form of a rigid layer and a second layer of mineral fibres. The invention also relates to the manufacture of such board as well as a ceiling panel system comprising such boards and a noise abatement barrier comprising such board.

Description

A sound reducing board and a process for the manufacture of the board

The present invention relates to a sound reducing board for reducing sound of different level. The invention also relates to the manufacture of such board as well as a ceiling panel system comprising such boards and a noise abatement barrier comprising such board.

It is generally known in the technique of sound reduction that the larger the sound absorbing surface area the larger the sound absorption potential. It is also generally known that porous materials in general have a high absorption coefficient.

Thus, it is known to use material with high absorption coefficient in rooms or towards areas where sound reduction is needed. However, in order to have a safe sound reduction in environment with varying sound or noise load, the sound reduction through the material has to be calculated on the peak load. Even when using materials with high absorption potential, i.e. good absorption^" properties for a given thickness relative to the absorption properties for other materials with similar thickness, this often results in that the necessary thickness of the material for obtaining a satisfactorily sound reduction through the material is undesirably or even unacceptable high.

DK patent application PA19960713 discloses a sound reducing wall composed of mineral fiber material encapsulated in a perforated cover. The mineral fiber material is highly sound absorbing, and, thus, when the wall is placed along a railroad or a similar noising traffic line the noise emitted from the traffic is absorbed by the wall. However, in order to be able to absorb the noise during the peak load of noise, the wall must be undesirable thick e.g. 150 mm or even 200 mm.

It is also known to use panels having a first layer of mineral fibres and a second layer of gypsum for buildings e.g. as ceiling panels such as described in US 5,202,174. Such panels are, however, relatively expensive, due to the gypsum, and in certain applications the gypsum/mineral fiber plates do not have a satisfactory shielding against sound. If such panel for instance are build into a false ceiling the sound from one room may pass into the mineral fiber material and being reflected by the gypsum layer and the non-absorbed sound will be returned to the room.

On the other hand if the panels in the suspended or dropped ceiling were prepared from highly absorbing mineral fiber material and the suspended ceiling constituted a suspended ceiling for two or more rooms, which was separated by a wall which extended from the floor to somewhere between the suspended ceiling and the base ceiling, the sound would enter into the mineral fibers, and the non-absorbed part, which in many circumstances could be very substantial, would pass along the space between the base ceiling and the suspended ceiling and through the mineral fiber plate into another room. The sound reduction or shielding would, thus, be inadequate .

The object* of the invention is, thus, to provide a sound reduction board, which does not have drawbacks as discussed above.

A further object is to provide a sound reduction board, which can reduce the passing of sound to an acceptable degree even when the sound load is very varying, and at the same time be optimized with respect to cost and thickness .

As it will be explained in the following, these and other objects are solved by the board as defined in the claims.

The invention is based on the discovering that the use of a specific high density rigid layer of mineral fiber material in a specific combination with one or more mineral fiber layers of lower density in noise barrier systems result in an optimized combination of reflecting and absorbing noise whereby the amount transferred from one space to another may be reduced using such noise barrier systems.

The invention concerns a sound reducing board comprising two or more layers, wherein at least one first layer designated a rigid layer, comprises mineral material bound together by an organic binding agent, and has a mean density of at least 300 kg/m³, preferably of at least 450 kg/m³. By the term * rigid layer" is meant a mineral fiber containing layer having a density above 300 kg/m³ whereby a layer with a relatively high compressive strength is obtained. Thereby the rigid layer has a high compressive strength relative to the other mineral fiber layers with densities below 300 kg/m³. Due to the high density and the high compressive strength, compressing of the rigid layer needs high forces and is almost impossibly if the density of the rigid layer exceed 1000 kg/m⁰.

For most applications the rigid layer should preferably have a mean density of at least 500 kg/m preferably of at least 800 kg/m³. The higher the density of rigid layer, the higher is the sound reflecting property. However, the thickness also influences this sound reflecting property. Thus, it is preferred that the rigid layer has a thickness of between 2 and 12 mm, more preferably between 3 and 7 mm.

Due to the high density of the rigid layer its ability to absorb water and moisture is very low. If the sound reducing board is for use in moist or wet environments it is, however preferred that the rigid layer is hydrophobic e.g. by being treated with oil, as it is generally known in the art.

The sound reducing board further comprises a second layer of mineral fibres comprising mineral fibres and a binding agent, and has a mean density which is lower than the mean density of the rigid layer.

In a first aspect of the invention the sound reducing board is particularly for use as a ceiling plate in a suspended ceiling. In this first aspect it is particularly preferred that the second mineral fibre layer of the sound reducing board has a mean density of between 50 and 350 kg/m³, preferably between 80 and 120 kg/m³, and preferably has a thickness of between 10 and 40 mm, more preferably between 15 and 30 mm.

The sound reducing board of this first aspect preferably comprises a third layer adjacent to the other side of rigid layer to thereby providing a board of a rigid layer sandwiched between the second and the third mineral fiber layer. This third layer comprises mineral fibres and a binding agent, and has a mean density, which is lower than the mean density of the rigid layer. The thickness of the second and the third mineral fiber layer may preferably be substantially equal to each other, but they may also be different. One or both of the second and third layers may e.g. be in the form of a dual density mineral fiber layer.

By a dual density mineral fiber layer is meant a mineral fiber layer composed of two sub-layers placed adjacent to each other and having different densities.

The dual density layer or layers in this first aspect of the invention should preferably have a mean density of between 50 and 350 kg/m", preferably between 80 and 120 kg/m³, and preferably has a total thickness of between 10 and 40 mm, more preferably between 15 and 30 mm. The higher density layer of the dual density layer should preferably be placed adjacent to the rigid layer and the lower density layer of the dual density layer should preferably have a porous or corrugated surface.

The sound reducing board according to the first aspect of the invention may preferably be profiled along its edges to thereby constitute ceiling panels ready for being applied into a grid or similar mounting means.

For further information references is made to EP application Nos. 00610029.1, 0209953, 0979908, DE application No. 1939904 and US patent No. 3,708,941.

The invention, thus, also relates to a ceiling panel system for a suspended ceiling comprising a grid and two or more panels for inserting into the grid, wherein said two or more panels being in the form of two or more sound reducing board, preferably according to the first aspect of the sound reducing board according to the invention.

It is preferred that the ceiling panels are adapted to be placed in the grid so that the rigid layer is the uppermost layer. Thereby is provided a particularly noise reducing ceiling panel system.

When noise is passing from the room beneath the ceiling panel system according to the invention, a part of the noise will be absorbed by the second and optional third mineral fiber layer (s) of the panels. Of the remaining part of noise a first part will be reflected by the rigid layer, and be returned through the second and optional third layer, a second part of noise will be absorbed by the rigid layer and a third part of noise will pass through the rigid layer and strike the base ceiling where again some of the noise will be returned and some of the noise will be reflected and returned towards the rigid layer. By adjusting the density of the rigid layer the relative proportion of noise not absorbed by the second and third layer can be adjusted so that for a given total thickness of panel an optimal ceiling plate can be provided.

In a second aspect of the sound reducing board according to the invention the sound reducing board is particularly for use as or in a noise abatement barrier particularly for preventing noise from passing from one side of the barrier to the other side of the barrier e.g. a road noise barrier as will be described later on. In this second aspect the second layer mineral fibre layer preferably have a mean density of between 50 and 300 kg/m³, more preferably between 80 and 220 kg/m³. The thickness of the second mineral fiber layer should preferably be between 10 and 250 mm.

In this second aspect of the invention the sound reducing board should preferably comprise a third layer adjacent to the second layer, wherein this third layer comprises mineral fibres and a binding agent, and has a mean density which is lower than the mean density of the second layer.

The total thickness of the rigid layer, the second and the third mineral fiber layers should preferably be between 60 and 300 mm, more preferably between 70 and 240 mm.

The sound reducing board according to this second aspect of the invention is particularly useful in a noise abatement barrier system for being placed along roads, railways or similar noising traffic lines. In order to improve the appearance of such noise abatement barrier the third and optionally also the second mineral fiber layers of the sound reducing board used in the noise abatement barrier may preferably be water absorbing, hydrophilic layer or layers or a further layer may be hydrophilic layer may be placed upon the third mineral fiber layer e.g. a layer of grodan®.

In order to provide a further protection between the hydrophilic layers and the rigid layer, an airtight and optionally watertight material e.g. a polymeric film or closed pore foam may be placed between the hydrophilic mineral fiber layer (S) and the rigid mineral fiber layer.

In a variation of this second aspect the third mineral fiber layer is replaced by a secondary rigid layer which on its outer surface, i.e. the surface turning away from the second mineral fiber layer, is provided with small depressions or pinholes having a depth of between 1 mm to the thickness of the secondary rigid layer, preferably a depth of between 3 and 10 mm. The pinholes may preferably have an average diameter of 0.5 to 5 mm. Preferably at least 10 % of the surface area of the outer surface of the secondary rigid layer is constituted by pin holes, more preferably 20-30 % of the surface area of the outer surface of the secondary rigid layer is constituted by pin holes .

In a third aspect of the invention the sound reducing board is particularly for use as or in a noise abatement barrier particularly for preventing noise from passing from one side of the barrier to the other side of the barrier and visa verse e.g. a wall noise barrier as will be described later on. In this third aspect the sound reducing board preferably comprises a further rigid layer adjacent to the second layer, said further rigid layer comprises a mineral material and an organic binding agent, and has a mean density of at least 500 kg/m⁰, preferably of at least 800 kg/m³. The two rigid layers may preferably have equal density and equal thickness.

In this third aspect it is preferred that the second mineral fiber layer of the sound reducing board is in the form of two second sub-layers having substantially equal mean density and substantially equal thickness. The mean density of the two sub-layers of the second layer should preferably be between 50 and 350 kg/m³, more preferably between 80 and 150 kg/m³, and the thickness of the two sub-layers, respectively, of the second layer should preferably be between 10 and 120 mm, more preferably between 30 and 80 mm.

In a preferred embodiment of this third aspect each of the second sub-layers should preferably be in the form of a dual density mineral fiber layer as defined above. This dual density layers should preferably comprise a first dual density layer with a density below 150 kg/m³, and a second dual density layer with a density above 150 kg/m³, wherein the first dual densities layers of said two second sub-lay being placed adjacent to each other.

It is particularly preferred that the two rigid layers, respectively, have thicknesses between 2 and 5 mm.

In an embodiment of the sound reducing board in this third aspect, the outer surface or surfaces of one or both of the two rigid layers i.e. the surface (s) turning away from the second mineral fiber layer may be provided with small depressions or pinholes having a depth of at least 1 mm, preferably the pinholes goes through the entire thickness of the rigid layer (s). The pinholes may preferably have an average diameter of 0.5 to 5 mm. Preferably at least 10 % of the surface area of the outer surface (s) of the rigid layer (s) is constituted by pin holes, more preferably 20-30 % of the surface area of the outer surface (s) of the rigid layer (s) is constituted by pin holes.

The invention, thus, also relates to a noise abatement barrier comprising one or preferably more of the sound reducing boards preferably of the sound reducing board of the second and/or third aspect of the invention.

The noise abatement barrier may in the second aspect may preferably comprise a number of boards collected to each other to provide one barrier e.g. by use of assembling fittings, a grid system or simply by using adhesive.

If the boards comprises a third layer it is particularly preferred the third layers of the boards are displaced with respect to the second layers so that as many connection lines between adjacent second layers are covered by the third layer. The barrier preferably have two major side surfaces, an upper surface and a lower surface, wherein at least the major part of at least one of the major surfaces being covered with a perforated outer cover. It is particularly preferred that at least the area on one of the major surfaces adjacent the lower surface being covered with a perforated outer cover.

Also it is preferred that the perforated cover on at least one of the major surfaces on one or more boards comprises one or more protrusions or flanges for mounting the wall to the ground directly or indirectly e.g. via holding profiles, which is attached to the ground or similar means.

This noise abatement barrier according to the second aspect is particularly for use a barrier against noise from a road a rail way or similar noising traffic.

The perforated outer cover as well as the means for anchoring the noise abatement barrier to the ground may preferably as described in DK PA 199600713.

In use the rigid layer should be turned against the noising area. Thereby, a large amount of noise will be reflected toward the noising area e.g. the road, and the other part of the noise will be transferred into the material where it will be absorbed. The amount of noise passing through the noise abatement barrier will be relatively small.

The noise abatement barrier may in the third aspect may preferably be in the form of a noise barrier wall, which comprises several boards, wherein each board has two major side surfaces, and four minor sides, the boards being assembled to each other along their respective minor sides using assembling fittings, to provide a substantially plane noise barrier wall. It is preferred that two or more of the layers are displaced towards each other so that no connection lines between boards goes directly crosswise through the wall.

The assembly fittings may e.g. be in the form of an adhesive, adhesive tape or double tape, profiles or similar well-known means. In a preferred embodiment of the noise abatement barrier the barrier is made from two or more sound reducing boards which is profiled along the edges adapted to be placed against each other, preferably the edges comprise one or more groove whereby the sound reducing boards can be placed in a grid or profile system so that the surface of the final noise abatement barrier is substantially plane, and simultaneously the sound reducing board can be solidly fixed in the grid or profile system. The upper and the lower edge surface of the noise abatement barrier may preferably be supported by a beam or similar means.

The noise abatement barrier in the form of a noise abatement wall may also be prepared as one single sound reducing board.

The noise abatement wall may e.g. be covered with a tackable layer as described in US 5,665,447.

The sound reducing board according to the invention may in general be prepared as described in PCT/DK/00282.

The method according to the invention as defined in the claims, thus, has the advantage that it is possible to apply a rigid surface layer more precisely than with known techniques and also it is possible to apply a layer, which is relatively thin. The variation of the density of the rigid layer can be minimized to +/- 5 % and the variation of the thickness of the layer can be minimized to +/- 0,5 mm. The application of dry bulk material with a dry powder binder minimizes the risk of wet spots. The dry process furthermore has the advantage that no evaporation of water is required. This results in increased capacity of the curing- or hardening oven.

The application of the rigid surface layer is independent of the spinning machines, which results in increased capacity of the plant. The rigid surface layer may be constituted by mineral fibre waste, and thereby the present invention also solves a waste problem.

By applying an organic binder to a composition comprising significant amounts of one or more mineral materials allowing for a tight packing of the material, it has surprisingly proven possible to produce very dense and strong surface layers for sound reducing board products, even if these layers are produced very thin.

The advantageous strength and sound reflection properties are thought to be at least partly due to the fact that organic binding agents tend to create a less brittle bonding between the constituents than the prior art inorganic binders such as geo-polymers, silica based binders and colloid phosphoric acid based binders.

The high strength is also believed to be at least partly due to the use of mineral material of high bulk density in the composition. It has surprisingly been found that such material allows for a compact and dense packing of the rigid layer composition which together with the use of organic binding agent appears to lead to a significantly higher strength and increased ability to reflect sound than provided by e.g. the mere compressed fibre layers of the prior art as well as the inorganically bound layers.

The rigid surface layer of the product according to the invention also exhibit the advantages of being essentially insoluble in water after curing or hardening as well as being thermally stable; both properties being beneficial for outdoors use.

The type and amount of organic binding agent in the rigid layer (s) and the binding agent in the second and optionally third mineral fiber layer (s) may preferably be as described in PCT/DK/00282.

Furthermore, as the rigid surface layer according to the invention is more dense and strong, it is also more dimensionally stable, homogenous and even, which efficiently reduces the amount of adhesive or paint necessary to cover the surface sufficiently. As the rigid surface layer is very cohesive it also provides excellent basis for adhesion thereto.

Any grained mineral material and/or combinations of mineral materials which essentially provide for the above defined properties of the rigid layer can be used according to the invention. Preferred materials and combinations of materials are as described in PCT/DK/00282.

The term bulk density is defined as the density of the bulk layer after the bulk surface material is distributed on the mineral fiber insulating base layer and cured or hardened to the finishing product. The difference of the density of the material before distributing it to the mineral fiber insulating base layer and after the curing or hardening may be up to 50 % . A further advantage of the mineral fibre product according to the invention is that the rigid surface layer is open to diffusion. This has proven highly advantageous where the product is used outdoors e.g. as a noise abatement barrier. Where the sound reducing board according to the invention comprises a rigid surface layer open to diffusion any water penetrating the material will diffuse and distribute itself, and when evaporating escape through any available channels.

The sound reducing board according to the invention, particularly in its first and second aspect for use as a ceiling panel or for use as a noise abatement barrier e.g. along a traffic line may e.g. be provided with a surface coating in form of a woven or non-woven textile, preferably a non-woven fleece. This has proven to add significantly to the tensile strength of the layer as well as reducing the amount of dust which otherwise might be released from the product depending on its composition.

Preferred textiles may be as described in PCT/DK/00282.

The sound reducing board as well as the ceiling panel and noise abatement barrier according to the invention can be shaped in any way known in the art of mineral fibre insulating materials, however, the products are preferably in the form of substantially rectangular boards/collection of boards.

The process for the manufacture of a sound reducing board according to the invention comprises the steps of a) providing one or more mineral fiber insulating base layers comprising a binding agent, said layer having an average density of 50-350 kg/m⁰, b) providing one or more bulk layer materials with an average bulk density of at least 300 kg/m°, preferably at least 450 kg/m³ and comprising a substantially homogenous mixture of at least one mineral material and an organic binding agent, c) distributing the bulk layer material on at least one surface of the mineral fibre insulating base layer, d) curing or hardening the organic binding agent within the bulk layer material to form a rigid layer.

The mineral fiber layer or layers made by step a may constitute the second and/or third mineral fiber layers or part of them in case they are dual density layers.

In general it is preferred that the bulk material comprises 3-35 weight-% uncured organic binding agent in step b) , wherein this binding agent is cured in step d) .

Although it is generally desirable to apply as little water as possible in order to save the energy and/or time it takes to remove it, it has surprisingly been found that the strength of the rigid surface layer can be improved significantly by applying up to around 30 weight-%, preferably 10 weight-% water in the bulk surface layer material before setting the binding agent. Preferably an amount of 0.5-8 weight-% and even more preferably around 1-5 weight-% water is added to the material .

Furthermore, it has in particular proven advantageous to dissolve or disperse at least part of the binding agent in the water before applying it to the bulk composition.

According to one preferred embodiment of the process according to the invention as much as possible of the binding agent is suspended in the water, however, it has proven expedient to use suspensions having a binder content of no more than around 60 weight-%. Preferably the suspension has a binder content of around 20-60 weight-%.

According to another preferred embodiment of the invention it is preferred to mix around 50-100 weight-% of the binding agent to the bulk material in a substantially dry pulverous form and supply the remaining part of the binding agent as an aqueous suspension immediately prior to or substantially at the same time, or less than lo minutes before or after, preferably less than 5 minutes before or after the bulk surface layer material is distributed onto the surface of the insulating layer. This has i.a. proven to significantly increase the delamination strength between the insulating layer and the rigid surface layer.

The term describing the binder to be in substantially dry pulverous form or an essentially dry powder, means that the binder is pulverous and contains less than 10 weight- % of water, preferably less than 5 weight-% of water and more preferably less than 2 weight-% of water.

A further advantage of applying some water or other liquid to the bulk surface layer material is that it greatly reduces the amount of dust released from the material until the binding agent in the material eventually is set and the rigid layer thereby formed.

A similar dust reducing effect can also be achieved according to the invention by using an amount of other liquids, preferably mineral/silicone oils, which can be supplied in an amount of 0-3 weight-%, preferably 0.1-1 weight-% and more preferably 0.2-0.6 weight-%. Such oils can also be employed in order to increase the rigid surface layers hydrophobic properties or for other purposes. The hydrophobic properties can also be controlled by adding a corresponding amount of silicone resin or the like to the bulk surface material.

The mineral material used in the bulk surface material is preferably present in an amount of at least 40 weight-%, preferred in an amount of 40-97 weight-%, more preferably in an amount of 50-95 weight-% and even more preferably in an amount of 80-92 weight-%.

The mineral material used in the bulk surface material preferably comprises one or more constituents selected from the previously discussed groups of hard, soft, absorbing and ultra high density minerals as disclosed in PCT/DK/00282. The minerals are preferably essentially inorganic.

Before the application of the bulk surface layer material onto the surface of the insulating layer the non-hardened bulk material should have a density of at least 150 kg/m³. The optimal density of the non-hardened bulk material depends largely on the composition of the bulk material. The more fiber material included in the bulk material, the lower may the density of the non-hardened bulk material be. In general it is preferred that the density of the non-hardened bulk material is sufficient high to result in the desired bulk density as described above .

The high density provided by mineral material used in the bulk surface material can be obtained by using material which per se has a high bulk density such as described in PCT/DK/00282. Particularly it is preferred that the bulk layer material comprises 40-95 weight-% mineral material, which is preferably obtained by milling mineral fibres to an average fibre length of less than 50 mm, more preferably less than 150 μm. The bulk layer material may preferably further comprise 40-97 weight-% of quartz sand, and more preferably the bulk layer material also comprises 5-20 weight-% organic binder.

In general it is preferred that the bulk layer material comprises at least 1 % by weight of fibres having a length of at least 3 mm.

For mixing any pulverous binding agent, mineral material and any further constituents to obtain the bulk surface layer material any known means for mixing essentially dry particulate material of high bulk density can be used. However, the methods described in PCT/DK/00282 are preferred.

For an even distribution of the bulk surface layer material onto the surface of the insulating layer it is preferable to first feed the material to a box feeder as described in PCT/DK/00282.

It has according to an embodiment of the invention proven particularly expedient to straighten out or smoothen the top surface of the insulating layer before the application of the bulk surface layer material eventually forming the rigid surface layer. This has been found to lead to more even rigid surface layers.

Such conditioning can be performed using rollers as described in PCT/DK/00282. In case it is preferred to have the rigid surface layer on the bottom surface of the insulating layer, it is possible to feed the insulating layer onto a conveyor already being covered by a substantially uniform layer of bulk surface layer material. It is also possible to obtain rigid surface layers at both the top and bottom surface by doing both and otherwise proceed as disclosed above .

The sound reducing board may e.g. be composed by laminating layers as produced above with other layers in any known manner. In case of a dual or ulti density insulating layer, it is preferably obtained essentially as disclosed in DK 155 163 or PCT/DK99/00152.

The sound reducing board or the ceiling panel according to the invention may e.g. be produced by applying a third layer, on the second side of the rigid layer prior to or after hardening of the binder or alternatively the third layer may be laminated with the rigid layer after hardening of both layers.

The noise abatement barrier or the sound reducing board therefore may e.g. be produced by laminating two boards each comprising a rigid layer, a second mineral fiber layer and optionally a third mineral fiber layer together with the rigid layers outwardly e.g. as described in US 5,665,447. Alternatively the layers may be applied to each other prior to hardening of the materials.

If the base layer comprises two sub-layers having different densities, the first insulating layer may preferably have a thickness of 10-300 mm and a density of 50-150 kg/m³, and the second insulating layer may preferably have a thickness of 10-40 mm and a density of 120-300 kg/m³. In the process according to the invention particular when the boards are for use as noise abatement barrier, the base layer, may preferably be provided with a reinforcement material prior to the application of the bulk layer material and/or the bulk layer material being provided with a reinforcement material prior to, during or after distribution onto the base layer, wherein said reinforcement material preferably being in the form of a layer of woven or non-woven textile or a perforated cover layer, preferably in the form of a net or grit of metal, panels of wood and/or carbon fibres.

According to the present invention it is particularly preferable to apply the bulk surface layer material onto the insulating layer prior to the curing of any curable binding agent within the insulating layer. In this way the binder in all layers is cured at substantially the same time thus saving energy, equipment and process steps. The difference in the time of curing of the binders in all layers should be less than 10 minutes, preferably less than 5 minutes. A particularly preferred way to obtain these advantages according to the invention is to apply the bulk surface layer material onto the top surface of the mineral fibre web produced according to e.g. one of the above mentioned methods substantially immediately prior to the web enters the curing oven for heat curing. It is however, possible to apply the bulk surface layer material on a pre-cured mineral fibre insulating layer, separately curing the bulk material and thereby obtain the product according to the invention.

The curing may preferably be performed as described in PCT/DK/00282 The term fibre as used herein designates any oblong structure or particle having a length at least 3 times its average diameter.

All mineral fibre insulating layers mentioned in the present application are preferably non-woven mineral fibre webs.

The term mineral fibre as used herein comprises all types of man-made mineral fibres, such as rock, glass or slag fibres, in particular fibres used in materials for the above mentioned purposes, and as filler in cement, plastics or other substances, or which are used as culture medium for plants. In particular rock fibres have proven suitable for the purposes of the present invention.

The term rock fibre as used herein designates fibres as defined in PCT/DK/00282.

The term binding agent or binder as used herein comprises any material which is suited as binding agent in mineral fibre materials for the above products. Organic binding agents according to the invention in particular comprise phenol formaldehyde, phenol urea, acrylic-copolymer, resorsinol, furane and/or melamine resin, a furan resin as described in WO 99/38372, and are preferably irreversibly curable by heat setting or other means for setting binders known in the art .

All percentages are where nothing else is stated or evident meant as weight-% of the total weight of the composition in question. However, fibre length fractions are generally counted as the number of fibres falling within a certain category compared to the total number of counted fibres . The fibre dimensions mentioned herein are measured using a Scanning Electron Microscope (SEM) and simple image analysis as described in PCT/DK/00282.

The amounts of water addressed herein are meant as relating to essentially free water and/or more or less separately admixed water. Bound water in optional substances such as MgOH or the like is not included.

The physical properties of the products mentioned herein are measured according to the standard EN 12430.

The invention will in the following be further illustrated by means of figures.

In the following embodiments of the invention will be further described with references to the drawings.

Figure 1 shows a sound reducing board according to the first aspect of the invention.

Figure 2 shows a cross section of a noise abatement barrier according to the second aspect of the invention.

Figure 3 shows a section of a noise abatement barrier according to the third aspect of the invention.

The sound reducing board 1 shown in figure 1 is in the form of a ceiling panel, for use in a suspended ceiling system. The sound reducing board comprises a rigid mineral fiber containing layer 2 sandwiched between a second 3 and a third 4 mineral fiber layers with lower densities than the rigid mineral fiber layer. The third mineral fiber layer 4 is supposed to turn upwardly against the basic ceiling in the suspended ceiling. The higher the density of the rigid mineral fiber layer 2 is, e.g. above 800 kg/m³, the less need is there for the third mineral fiber layer 4, as the amount of noise passing through the sound reducing board 1 will be reduced accordingly. In the shown embodiment the third mineral fiber layer 4 has a thickness, which is about half the thickness of the second mineral fiber layer 3.

The noise abatement barrier 20 shown in figure 2 can be build from one or more sound reducing board according to the invention. In figure 2 only a section of the noise abatement barrier can be seen. The noise abatement barrier comprises a relatively thin rigid mineral fiber layer 21, a second and a third mineral fiber layer 22, 23 and a cover layer 24 which may be a vlis or a mineral fiber layer, preferably having a composition and density as the third mineral fiber layer. The outer surfaces of the third mineral fiber layer and the cover layer may preferably be covered with a metal net 25. In a particularly preferred embodiment the rigid mineral fiber layer 21 has a thickness about 5 mm and a density about 1000 kg/m°, the second mineral fiber layer 22 has a thickness about 30 mm and a density about 200 kg/m⁰, the third mineral fiber layer 23 has a thickness about 50 mm and a density about 10 kg/m³, and the cover layer 24 is a mineral fiber layer with a thickness about 10 mm and a density about 145 kg/m³. An aluminum foil may preferably be placed between the rigid layer 21 and the cover layer 24.

The cross section of the noise abatement barrier 30 shown in figure 3 comprise two 35, 36 or more (not shown) sound reducing board connected to each other. The sound reducing boards 35, 36 comprise 6 layers symmetrically placed respectively to each other. The two outer layers is rigid mineral fiber layers and the intermediate second layer comprise an middle layer 33 composed of two identical layers 33, 33 connected to each other, and two further layers 32 placed on each side of the middle layer 33. The sound reducing board 35,36 is connected together by using profiles 34.

Claims

Claims :

1. A sound reducing board comprising two or more layers, a first layer in the form of a rigid layer and a second layer of mineral fibres, wherein said rigid layer comprises mineral material bound together by an organic binding agent, and has a mean density of at least 300 kg/m³, preferably of at least 450 kg/m³, and wherein said second layer comprises mineral fibres and a binding agent, and has a mean density which is lower than the mean density of the rigid layer.

2. A sound reducing board according to claim 1 wherein said rigid layer has a mean density of at least 500 kg/m³, preferably of at least 800 kg/m³.

3. A sound reducing board according to claim 2 wherein said rigid layer has a thickness of between 2 and 12 mm, preferably between 3 and 7 mm.

4. A sound reducing board according to claims 2 or 3 wherein said second mineral fibre layer has a mean density of between 50 and 350 kg/m³, preferably between 80 and 120 kg/m³, and preferably has a thickness of between 10 and 40 mm, more preferably between 15 and 30 mm.

5. A sound reducing board according to anyone of the claims 2-4 wherein said sound reducing board comprises a third layer adjacent to the rigid layer, wherein said third layer comprises mineral fibres and a binding agent, and has a mean density which is lower than the mean density of the rigid layer.

6. A sound reducing board according to anyone of the claims 2-5, wherein at least one of the second and third layers being in the form of a dual density mineral fiber layer, having a mean density of between 50 and 350 kg/m°, preferably between 80 and 120 kg/m³, and preferably has a total thickness of between 10 and 40 mm, more preferably between 15 and 30 mm.

7. A sound reducing board according to claims 2 or 3 wherein said second layer mineral fibre layer has a mean density of between 50 and 300 kg/m³, preferably between 80 and 220 kg/m³, and preferably has a thickness of between 10 and 250 mm.

8. A sound reducing board according to anyone of the claims 2,3 and 7 wherein said sound reducing board comprises a third layer adjacent to the second layer, wherein said third layer comprises mineral fibres and a binding agent, and has a mean density which is lower than the mean density of the second layer.

9. A sound reducing board according to claim 8, wherein the total thickness of the rigid layer the second and the third mineral fiber layers is between 60 and 300 mm, preferably between 70 and 240 mm.

10. A sound reducing board according to anyone of the claims 2 and 3 wherein said sound reducing board comprises a secondary rigid layer adjacent to the second layer, said secondary rigid layer comprises an outer surfaces defined as the surface turning away from the second mineral fiber layer, said outer surface being provided with pinholes having a depth of 1 mm to 1mm less than the thickness of the secondary rigid layer.

11. A sound reducing board according to anyone of the claims 2 and 3 wherein said sound reducing board comprises a further rigid layer adjacent to the second layer, said further rigid layer comprises a mineral material and an organic binding agent, and has a mean density of at least 500 kg/m³, preferably of at least 800 kg/m° .

12. A sound reducing board according to claim 11, wherein said second mineral fiber layer being in the form of two second sub-layers having substantially equal mean density and substantially equal thickness, said mean density preferably being between 50 and 350 kg/m³, preferably between 80 and 150 kg/m³, and said thickness preferably being between 10 and 120 mm, more preferably between 30 and 80 mm.

13. A sound reducing board according to claim 12, wherein each of said second sub-layers being in the form of a dual density mineral fiber layer, having two layers with different densities wherein a first dual density layer preferably has a density below 150 kg/m³, and the other dual density layer preferably has a density above 150 kg/m°, said first dual densities layers of said two second sub-lay being placed adjacent to each other.

14. A sound reducing board according to anyone of the claims 11-13 wherein said rigid layers, respectively, have thicknesses between 2 and 5 mm

15. A process for the manufacture of a sound reducing board as defined in anyone of the claims 1-14, said process comprising the steps of

a) providing one or more mineral fiber insulating base layers comprising a binding agent, said layer having an average density of 50-350 kg/m³, b) providing one or more bulk layer materials with an average bulk density of at least 300 kg/m³, preferably at least 450 kg/m³ and comprising a substantially homogenous mixture of at least one mineral material and an organic binding agent, c) distributing the bulk layer material on at least one surface of the mineral fibre insulating base layer, d) curing or hardening the organic binding agent within the bulk layer material to form a rigid layer.

16. A process according to claim 15, wherein the bulk layer material comprises less than 30 weight-% water, preferably less than 10 weight-% water, even more preferably 1-5 weight-% water.

17. A process according to any of the preceding claims 15-16, wherein the bulk material comprises 3-35 weight-% uncured organic binding agent in step b) , said binding agent being cured in step d) .

18. A process according to any of the preceding claims 15-17, wherein the organic binding agent is provided in two or more steps, including one step of providing the organic binding agent as an essentially dry powder, said process preferably comprises the step of providing the organic binding agent as an essentially dry powder to the bulk layer material at substantially the same time as the material is distributed on the insulating base layer.

19. A process according to any of the preceding claims 15-18, wherein the bulk layer material comprises 40-97 weight-% mineral material, said mineral material preferably being obtained by milling mineral fibres to an average fibre length of less than 50 mm, preferably less than 150 μm.

20. A process according to any of the preceding claims 15-19, wherein the bulk layer material comprises 40-95 weight-% of quartz sand, and preferably said bulk layer material comprises 5-20 weight-% organic binder.

21. A process according to any of the preceding claims 15-20, wherein the bulk layer material comprises at least

1 % by weight of fibres having a length of at least 3 mm.

22. A process according to any of the preceding claims 15-21, wherein the base layer comprises two sub-layers having different densities and where the first insulating has a thickness of 10-300 mm and a density of 50-150 kg/m³, and the second insulating layer has a thickness of 10-40 mm and a density of 120-300 kg/m³.

23. A process according to any of the preceding claims 15-22, wherein the base layer being provided with a reinforcement material prior to the application of the bulk layer material and/or the bulk layer material being provided with a reinforcement material prior to, during or after distribution onto the base layer, wherein said reinforcement material preferably being in the form of a layer of woven or non-woven textile or a perforated cover layer, preferably in the form of a net or grit of metal, panels of wood and/or carbon fibres.

24. A ceiling panel system for a suspended ceiling comprising a grid and two or panels for inserting into the grid wherein said two or more panels being in the form of two or more boards as defined in anyone of the claims 1 to 13, preferably as defined in anyone of the claims 2-6.

25. A ceiling panel system according to claim 24 wherein two or more panels are adapted to be placed in the grid so that the rigid layer is the uppermost layer.

26. A noise abatement barrier comprising one or more boards as defined in anyone of the claims 1 to 14, preferably as defined in anyone of the claims 7-10.

2 . A noise abatement barrier according to claim 26 comprising one or more boards as defined in anyone of the claims 7 to 10 wherein one or more boards have two major side surfaces, an upper surface and a lower surface, at least the major part of at least one of the major surfaces being covered with a perforated outer cover, preferably at least the area on one of the major surfaces adjacent the lower surface being covered with a perforated outer cover.

28. A noise abatement barrier according to claim 25 preferably as defined in anyone of the claims 10-13, said noise abatement barrier being in the form of a noise barrier wall, and comprising several boards, wherein each board has two major side surfaces, and four minor sides, the boards being assembled to each other along their respective minor sides using assembling fittings, to provide a substantially plane noise barrier wall.