WO1993016245A1

WO1993016245A1 - Plate for sound absorption and method for manufacturing such a plate

Info

Publication number: WO1993016245A1
Application number: PCT/DK1993/000056
Authority: WO
Inventors: Inge Bodil Elmstroem Soerensen
Original assignee: Inge Bodil Elmstroem Soerensen
Priority date: 1992-02-13
Filing date: 1993-02-15
Publication date: 1993-08-19
Also published as: AU3493893A; DK17592A; DK17592D0

Abstract

Board (1) for sound absorption where the board is made of fibre layers (2) in which gypsum plaster is embedded. These fibres form layers in level with the board. The fibres may be made of a wide variety of materials, such as plastics, mineral materials, ceramic materials and other synthetic or natural materials. The reinforcing effect of the fibres results in the board obtaining high strength and stability even with small thicknesses of the board.

Description

PLATE FOR SOUND ABSORPTION AND METHOD FOR MANUFACTURING SUCH A PLATE.

Background of the Invention.

The present invention relates to a board for sound absorp- tion.

Boards to be used for sound absorption are primarily known in the form of plane plasterboards which may optionally be perforated. Furthermore, the plasterboards may be provided with one or more variations of sound absorbing sheets.

Plasterboards of the above mentioned type consist of a plate which is made exclusively of gypsum plaster. On these boards a layer of paper is generally adhered to each side to protect the surface of the board during handling and to avoid that the gypsum plaster emits dust or comes off. Such boards are widely used in the construction industry for partition walls where the porosity of the gypsum plaster provides good sound absorption. In order to obtain suffi- cient strength of boards used as wall material, they have a thickness of at least 5 mm and normally of approximately 10 mm. Often more boards are combined, surface against surface, in order to obtain increased strength and better sound absorption. Alternatively, the plasterboards may be provided with one or more layers of external or internal layers of fibres to increase the strength or the fire- retardative properties. The plasterboards are generally advantageous compared to for example chip boards, as they cannot burn.

When plasterboards are used for ceilings and on existing walls or as shields between noisy localities, they are often perforated. The optimum effect is achieved when the boards are placed at some distance from the wall or the ceiling. Some of the sound to be absorbed passes through the perforations, hits the massive wall or the ceiling behind and is reverberated. The reverberated sound will hit the back of the plasterboard and will thus not be reflected back into the room. This lowers the noise level noticeably. The back side of the boards may furthermore be provided with a sound absorbing sheet. This sound absorbing sheet may be produced in various materials and thicknesses. Thus it is possible to control which frequency ranges are to be the most effectively attenuated. The sound absorbing sheet may be made of a non-woven material which ensures a uniform and diffuse sound absorption. Instead of a sound absorbing sheet, batts made from mineral- or glass wool may also be used. They, too, will provide a diffuse sound absorption and at the same time insulate the room. This type of construction will, however, be unprofitable as plasterboards provided with such batts will be considerably thicker, heavier, and more complicated to mount.

Instead of gypsum plaster based boards for sound absorption batts or sheets based on fibres of various materials may be used. Their form may optionally be stabilized by exposing the batts or the sheets to pressure, heat or ultra-violet rays.

These batts or sheets have limited self-supporting capacity, and therefore they are intended to be permanently attached to the wall or the ceiling, to be mounted on a further building element as for example shuttering walls, by extension on a frame or simply by hanging freely from walls or from ceilings.

EP-Patent Application No. 0,295,925 describes a thin sound absorbing sheet which may be produced from a large variety of materials. Exemplary materials comprise woven or non- woven sheets of synthetic fibres, of glass or mineral wool fibres, resin bonded fibres or granular sheets, sheets made of foam materials or sheets made of thin sheets of metal, plastics, paper or other materials. It is a common feature of the proposed sheets made of various materials that they are not self-supporting and therefore they have to be extended between bars or in frames or hung freely. It is therefore a relatively protracted process to hang them and they cannot tolerate to be exposed to any particular loads. Furthermore, the sheets have not sufficient strength for lighting fixtures, paintings or the like to be arranged in or on the sheets.

Furthermore, for sound absorption, independant glass or mineral wool batts consisting of non-woven fibres bound with some sort of adhesive agent are used. These batts have a certain self-supporting capacity and the batts are adhered directly onto the wall or the ceiling, or as mentioned before, onto additional construction elements, such as shuttering walls.

The difference between plasterboards and sound absorbing sheets or batts is that the plasterboards are self- supporting presenting, however, the disadvantage of a relatively large board thickness, and thus a large volume per area unit for each board which makes them heavy and difficult to handle. Sound absorbing sheets and batts, on the contrary, are considerably lighter and easier to_. handle, but their self-supporting capacity is very limited. This lack of self-supporting capacity renders the mounting thereof more difficult as it will be necessary, as mentioned above, to use further elements such as frames, girders or thread elements to keep the sheets or batts extended. Other batts require, as mentioned, to be adhered directly to the wall, shuttering wall or the ceiling.

It is thus the object of the present invention to provide a board for sound absorption which combines the advantages of conventional plasterboards by being self-supporting, with the advantages of sound absorbing sheets and batts having such small thickness and mass per area unit, that the deformability of the board is increased relative to known plasterboards, and at the same time to obtain considerably easier handling of the board compared to the known plaster¬ boards. This object is obtained with a board which is characterized in that it comprises one or more layers of fibrous material and that gypsum plaster is embedded into each of the fibrous layers and extends in a belt which is of approximately the same thickness as the thickness of the fibrous layer.

It is also the purpose to provide methods for the manufac¬ ture of such plasterboard.

A first method is characterized in that the board is shaped in fixed, completely or partially closed moulding equipment consisting of an upper and a lower mutually displaceable mould half, that gypsum plaster and fibrous material are poured into the open mould, following which the form is closed, in that water or aqueous vapour is conducted to the mould, whereupon the board is removed from the mould after a certain stabilizing period.

Another method is characterized in that the board is shaped in fixed, open moulding equipment in that a moistened plasterboard with fibrous material is conducted through open moulding equipment, such as rolls, which impart to the plasterboard the desired cross-sectional profile.

In this way, a board of fibres is produced, the self- supporting capacity and stability of which are moreover maintained as compared to ordinary known fibre sheets, and having a considerably smaller thickness and thus less mass per area unit of the board than other known fibre- reinforced plasterboards.

Furthermore, the board according to the invention is advantageous in that the fibres keep the individual components of the board in place if a board should be exposed to such charges that the material is broken. Because of the smaller thickness of the board, the broken part may subsequently be repaired by moulding new gypsum plaster into the fracture. The board will then be ready for use again with the same appearance as before the fracture. Unless the fibre reinforcement is broken if the board is fractured, the board will, after such repair, possess the same strength as before the fracture.

As distinct from this, plasterboards of the known type cannot be repaired in a satisfactory manner because of their substantially larger thickness. Mending a known plasterboard of ordinary thickness will entail that only a limited part of the fracture surface is bonded. This is due to the fact that the large board thickness will not allow complete moistening of the board around the fracture. Such complete moistening, however, is necessary to ensure that a mended board obtains the same strength as a new board.

The fibrous material which is used in the board according to the invention may advantageously be non-woven fibres so that the board obtains uniform strength in all directions of the board plane.

Alternatively, the fibrous material may consist of woven fibres which are so arranged that the fibres are orientated in a given direction, for example lengthwise and crosswise of the board.

The fibrous material may be produced from a large variety of different materials which may be used in the layers individually or in combination. The preferred materials or combinations of material comprise synthetic and natural fibres, hightec fibre, such as oxidated acrylic fibres, tensioned or untensioned polyester fibres, acrylic fibres in combination with heterophyllic fibres, synthetic and natural fibres in combination with binding fibres, such as synthetic resin, non-inflammable fibres, fibres impregnated with fire-retardants , such as gypsum plaster, synthetic resin or another synthetic binders. As distinct from the known plasterboards but similar to sound absorbing sheets the major part of the sound absorption is achieved in the board itself and not behind the board. For the known plasterboards the major part of the sound absorption, however, is effected behind the board, by the sound passing through the board or the perforation thereof and is reflected and "fades out" between the wall behind or the ceiling above and the back side of the plasterboard.

In order to create a better sound absorption and optionally to achieve a higher strength of the board, the board may advantageously be pressed into shape to make profiles in the board, which provide better sound absorption or sound reflection, for example a wave form. Such a profiled board may furthermore give an aesthetically appealing look by breaking the uniformity of plane surfaces. Furthermore, it is also possible to break the light to avoid disturbing light reflections from the boards.

The board according to the invention may, like the known plasterboards, optionally be perforated and/or provided with sound absorbing sheets or batts. Furthermore, it will be possible to dye the board and to provide it with a covering sheet or foil made of cardboard, paper, metal or other material which may i.a. be part of the board decoration. The board may in particular cases be impregnated to make the board resistant to dry rot, bacteria or algae.

The board is suitable for use in many types of rooms, both climatized and chilled and hot rooms. The board may thus be used in offices, residential rooms, gymnasia, swim baths, concert halls etc.

Brief Description of the Drawings.

The invention will now be further explained with reference to the accompanying drawings, wherein Fig. 1 shows a section through an embodiment of a plasterboard according to the invention, Fig. 2 shows a perspective view of an embodiment of a plasterboard coated with foil, and Fig. 3 shows a perspective view of an embodiment of a profiled plasterboard, and Fig. 4 shows a further embodiment of a profiled plasterboard.

Fig. 1 illustrates an embodiment according^" to the invention consisting of a board 1, which herein has three layers of embedded fibrous material 2. The exterior 3 of the board 1 is gypsum plaster and the layers of fibrous material 2 will be comprised within the gypsum plaster.

The dimension of the board in its plane and across its plane, respectively, is primarily determined by the fibrous material used and the number of layers of this material. For illustrating purposes, however, the ratio between the thickness of the fibre- and gypsum plaster layers, respectively, are distorted in the figure. The gypsum plaster will, in the correct embodiment, according to the invention, have a thickness which is approximately identical with the thickness of the fibre layers, as stated in claim 1 and not as illustrated, be of a considerably larger thickness. The length, width and thickness of the board is determined both empirically from the requirements to handling, transportation, weight etc. , and empirically from the requirements to strength, elasticity and other physical properties of the board.

The board according to the invention will have a thickness smaller than the known plasterboards. It will be from 2 to 15 mm.

The number of layers will primarily be determined empirically, depending on the desired physical properties of the board, and on the fibrous material used. Thus, the number of layers will be from 1 to 10, preferably, however, from 3 to 6.

The fibrous material will, as mentioned above, preferably be layers of non-woven fibres. The fibres may be produced from a large variety of materials depending on the purpose for which the board is to be used.

It applies to a wide variety fibres of plastics that they will be inexpensive, but the strength of these fibres will be limited. Furthermore, these fibres will be relatively elastic. The board will further burn or melt in case of fire. Boards with plastic fibres therefore will be most suitable where there is no requirements that the boards be non-inflammable, and where the risk of the boards being exposed to large loads is small.

An exception, however, is the special types of plastics such as kevlar and mylar which are developed to obtain high strength. Fibres of these materials will have a very high strength, which, however, may be unnecessarily high in many cases relative to the strength of the gypsum plaster proper used in the board. These special plastic fibres, however, will still present the disadvantage that they are inflammable.

Fibres of glass or other ceramic materials will have high strength, but will also be more expensive than most plastics fibres. Boards with glass or mineral fibres or ceramic fibres will therefore be suitable for use in boards which may optionally be exposed to great loads. As the inflammability of ceramic materials is very low, the boards may also be used where requirements are made for high resistance to fire.

Fibres of other synthetic or natural materials as for example cotton and asbestos fibres may also be used in the plasterboards according to the invention for the manufacture of boards which are to comply with special requirements, wishes and price levels. Likewise, it will be possible to combine fibres of various materials and thereby utilize the individual properties of the various materials in the same board.

In Fig. 1 the board shown, as mentioned before, is for illustrating purposes with the major part consisting of gypsum plaster and the plaster layers 2 constituting a smaller part. It will, however, be possible to let the plaster layers constitute the major part, optionally it all, of the board 1, and where the gypsum plaster only provides a plane, even surface. With such an embodiment, however, it will be necessary to stabilize the fibre layers, as there is not enough gypsum plaster to fix the fibres. This stabilization and fixation of the fibre layers may be carried out with various means, such as synthetic resin or caoutchouc or other means of reinforcement which advantageously are non-inflammable.

The board according to the invention may be manufactured according to known methods which presently are used within the trade. A modification of these methods, however, should be carried out to ensure that the fibrous material is embedded in the gypsum plaster.

A possible method of manufacture is to shape the board in moulding equipment with the profile to be imparted to the relevant board. According to a preferred embodiment the mould will preferably be heated to approximately 200°C and furnished with a number of nozzles through which water or steam is supplied. Gypsum plaster powder and fibrous material are alternatingly poured into the lower half of the mould following which the upper half of the mould is lowered. Water or steam is, within a given time, supplied to the closed mould. Between the two halves of the mould a pressure of approximately 1 . 10⁶ N/m² prevails. After a certain stabilizing time, preferably 5 minutes, the shaped board is lifted out of the mould. Then the board is dried either in the open or in drying kilns.

The above mentioned process may very well be carried out in a running production line and the board may be shaped to desired profiles by rolling while the board is still moist and workable. How to handle the boards technically during production as well as the moulding process itself is comprised by the techniques already used in the trade.

Fig. 2 shows an embodiment where the board 1 is coated with various types of coating foils or sheets 4 to comply with special requirements to the board.

It may be metal- or plastics foils which make the board steam impermeable; sheets of paper which, like the known plasterboards, prevent that the board emits dust, comes off or is damaged when handled; sound absorbing sheet which enhances the attenuation of certain frequencies; or simply tapestry or the like which makes the board more attractive.

These various foils and sheets 4 will preferably be applied to the board 1 by glueing, but other adhesion methods may be used where glueing is undesirable. The application of the foils or sheets will preferably be carried out after the board is stabilized and dried, but may, when possible, be carried out before the final shaping and drying.

Fig. 3 illustrates an embodiment of a profiled board. The profile of the board shown is a wave profile but it is possible to impart all sorts of profiles to the board, which are not beyond the mouldability of the gypsum plaster and/or the fibres. Some profiles, like for example the wave profile shown, may be manufactured by rolling, while other profiles may only be shaped in fixed, closed moulds. The profile may be chosen according to aesthetic criteria for manufacturing boards with broken surfaces, which give a visually pleasant impression or the profile may be chosen according to sound and/or light criteria for manufacturing boards, which reflect sound and/or light in a given manner.

Thus, fig. 4 illustrates another embodiment of a profiled board l where the profile is constituted of planes 5 situated in different levels. The board is asymmetrical around an axis 6. Thereby, a pattern may be created by mounting several boards next to each other and orientating them in different directions. The pattern may be systematical or it may be unsystematical depending on the visual impression to be made. Apart from the purely visual difference relative to for example plane boards these boards also provide an acoustic difference. A more diffuse reflection of the sound is obtained in the room where they are mounted as the boards 5 in an asymmetric pattern reflect the sound in different directions, even though the sound has the same angle of incidence to the ground level of the board 7.

Above, the board according to the invention was described in such a way that the various embodiments in addition to those shown on the drawings, are also comprised within the scope of the present invention, but the alternatives and combinations mentioned of fibrous material, the possible moulding processes, the foils or sheets to be secured to the board, and the various profiles into which the board may be shaped, should be seen as exemplary non-limiting embodiments of the construction, shape, production, and use of the board.

Claims

C L A I M S.

1. A board for sound absorption, c h a r a c t e r i z e d in that it comprises one or more layers (2) of fibrous material and that gypsum plaster is embedded into each of the fibrous layers and extends in a belt which is of approximately the same thickness as the thickness of the fibrous layer.

2. A board according to claim 1, c h a r a c t e r i z e d in that the fibrous material comprises non-woven fibres.

3. A board according to claim 1, c h a r a c t e r i z e d in that the fibrous material consisting of woven fibres oriented in at least one pre-determined direction in a given layer (2) .

4. A board according to any one of the preceding claims, c h a r a c t e r i z e d in that the mass ratio of the fibrous material to the gypsum plaster is 4:1.

5. A board according to any one of the preceding claims, c h a r a c t e r i z e d in that the number of fibrous layers used is from 1 to 10, preferably from 3 to 6, and that the thickness of the board is from 2 to 15 mm.

6. A board according to any one of the preceding claims, c h a r a c t e r i z e d in that the fibrous material consists of a plastics material.

7. A board according to any one of the preceding claims, c h a r a c t e r i z e d in that a covering foil or covering sheet (4) is secured to one or both sides of the board.

8. A board according to any one of the preceding claims, c h a r a c t e r i z e d in that the board is perforated and is furnished with sound absorbing sheets or sound absorbing batts.

9. A method for the manufacture of a board according to claim 1, c h a r a c t e r i z e d in that the board is shaped in fixed, completely or partially closed moulding equipment consisting of an upper and a lower mutually displaceable mould half, that gypsum plaster and fibrous material are poured into the open mould, following which the form is closed, in that water or aqueous vapour is conducted to the mould, whereupon the board is removed from the mould after a certain stabilizing period.

10. A method for the manufacture of a board according to claim 1, c h a r a c t e r i z e d in that the board is shaped in fixed, open moulding equipment in that a moistened board is conducted through open moulding equipment, such as rolls, which impart to the plasterboard the desired cross-sectional profile.