AU2002100782B4 - Ceiling panels - Google Patents

Description

19/84/2004 14:54 +613-9B90-1337 PATENT ATTORNEY SERV PAGE 04118 CEUIING PANELS This innovation relate to ceiling panels, particularly ceiling tiles, used within buildings.

As used throughout this specification, the expression "ceiling panel" or "ceiling tile" encompasses building panels or tiles used for other purposes where the properties of ceiling panels or ceiling tiles make them suitable. For example, such properties can include aesthetic characteristics, insulating (thernal and/or acoustic) properties, dimensional characteristics and physical integrity (although structural strength is usually not a property of ceiling panels or ceiling tiles, sufficient integrity for enabling handling and use to form a ceiling or ceiling lining or cladding is required), low costs, fire retardant properties, wetting or liquid absorbency without compromising physical integrity, pest or rodent or micro-organism resistant properties, etc. Building panels having at least some of these kinds of properties can be used for example as wall panels, in lightweight movable partitions or screens, or in other (usually non-structural) applications. Such panels can also be used as notice boards, as insulation infill (e.g.

behind surface panels or layers), as a core material having a surface layer adhered or laminated thereto, as packing material for storage or freight of goods.

In Australian patent specification No, AU-48947/93 there is described a process for manufacturing bodies composed of a binder mixed with a feed mateTial including rice hulls and/or particles obtained by comminting rice hulls. The binder comprises a beat curable composition. The mixture of the f ed material and binder is formed into the generally desired shape of the body e.g. in a mould or in a press, and the binder is cured to form an adherent body having substantially the required shape, e.g. by applying to the formed shape an RF field of a suitable frequency and intensity and for a suitable period of time to cause dielectric heating within the mixture so as to cure the binder to form the

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COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19 19/04/2004 14:54 +613-9890-1337 PTN TEE EVPG 51 PATENT ATTORNEY SERV PAGE 05/18 final adhierent body. The body is then removed from the mould or press. Reference may be made to this patent Specification for further background information particularly in relation to rice hulls and their properties and preparation, and for information about binders, and for infornation about techniques for forming bodies using rice hulls and binders. The contents of that specification are incorporated herein in full! by crossreference.

A Aurther patent specification AU-199670802 by the present application further describes processes for forming bodies using rice huls This patent specification is also incorporated herein in full by cross-reference for the purpose of providing further background information about rice hulls and their preparation, binders and their use, and methods for forming bodies including panels and the possible parameters of such forming operations. Some relevant parts from the specification AU-199670802 are repeated and elaborated further herein.

It is an object of the present innovation to provide ceiling panels made using rice is hulls and having useful and advantageous properties.

According to the present innovation there is provided a ceiling panel composed of aparticulate filler having a large proportion of rice hulls and a binder which is mixed with the particulate filler and -which is set or cured to bind the filler particles together to form a panel having sufficient integrity to be handled and maintain its shape during hadling and use, the mixture of the filler and the binder having been fonned into a generally desired shape and setting or curing of the binder being at least initiated or progressed while the mnixture is in the desired shape, the ceiling panel including a coating which is applied to the pan~el on at least one face thereof, the coating providing additional binding where applied to the panel, the coating being applied without substantially filling or sealing interstices between filler particles whereby desired 2 COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19 19/04/2004 14:54 +613-9890-1337 PATENT ATTORNEY SERV PAGE 06/18 aesthetic and insulating properties of the panel before being coated are maintained to a significant extent after the coating is applied.

The ceiling panel, before being coated, may be made by a method which includes the steps of forming a mixture of the particulate filler and the binder, forming the mixture into a generally desired shape for formation of the ceiling panel, locating the mixture in that shape in a curing zone, applying pressure to the opposite faces of the shape and, while maintaining the pressure, simultaneously applying heat to the shape at both faces, the application of heat to both faces of the shape being substantially simultaneously initiated and continued so as to avoid a differential heating effect on the opposite faces prior to the application of pressure thereby.

In the product of the present innovation, a large proportion of rice hulls is used in the particulate filler so as to utilise the advantageous properties of rice hulls, particularly insulating properties (both acoustic and thermal insulating properties), light weight, fire resistant and water resistant properties, as well as aesthetic properties of panels made from rice hulls. However, reference to a "large proportion" office hulls being used is not intended to necessarily mean that the greater proportion, i.e. greater than 50%, of rice hulls constitutes the particulate filler. Lower percentages may be useable provided significant advantages arising from the properties of rice hulls are characterising the product as a result of the use of that proportion of rice hulls, In the preferred product of the present innovation, whole or untreated rice hulls form at least a substantial proportion of the filler material since whole rice hulls provide the sound and/or thermal insulation as a result of the cavities therein. The reference to "whole" or "untreated" rice hulls is referring to rice hulls after whole rice heads have been threshed to separate the edible grains. "Raw" rice hulls after the threshing operation can have for example between 5% and 10% by weight of fine particles having 3 COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19 19/04/2804 14:54 +613-9990-1337 PATENT ATTORNEY SERV PAGE 07/18 the consistency of dust. Preferably fines or dust particles are removed before mixing of the rice hulls with the binder. The process and purpose is further described in AU- 199670802.

Preferably, the manufacturing process further includes separating or inactivating any whole rice grains in the initial feed material. Bulk or raw rice hulls material can have up to 5% of whole rice grains mixed in the hulls, the percentage varying widely depending on the efficiency of the threshing and winnowing processes used to separate the hulls. Whole rice grains mixed 4 COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19 04/10/2002 20:e3 +613-9890-1337PAETTORYSEVAG 062 PATENT ATTORNEY SERV PAGE 08/25 within the feed material, if mixed with the binder and bound into tefia aderent body, can create problems with use of the product, particularly if the rice seeds remain capable of germinating. For example, if whole rice grains are formed into the body and the body at any stage is exposed to water, including high humidity, the seeds if viable could germinate leading to structural and/or aesthetic physical defects in the product.

The raw feed material may be fluidised in a vessel so that the dense whole gains tend to accumulate at the bottom of the vessel making their removal possible, Preferably any whole rice grains in the mixture are inactivated by raising the body to a temperature sufficient to sterilise or inactivate any viable seeds, e.g. during the step of raising the temperature of the formed shape. The temperature throuShout the body may be raised to greater than 80'C and preferably to greater than 90*0.

The process for forming a body of rice hulls may be improved by generally processing the particulate feed material so that the density and/or composition of the mixture formed of the particulate feed material and binder is substantially uniform i.e. irthomogeneities are substantially removed. This processing preferably includes removal of relatively dense particles including contaminating dirt or mineral particles, and preferably removal of whole rice grains as discussed above. The process of making the mixture as uniform as possible preferably also includes removal of fines or dust privies as discussed above.

If desired, the mixture may include additional fillers or substances so as to ittilise available feed materials and/or contribute desired properties to the final product. For example, fllers such as straw (which may be chopped or otherwise treated to desirable lengths), hemp fibres, or other cellulose fibres may be incorporated in the feed material together with the whole rice hulls. Fillers or other additves having long fibres can help to 19/04/2004 14:54 +613-9890-1337 PTN TOtE EVPG 81 PATENT ATTORNEY SERV PAGE 08/18 bind the rice hulls and can add tensile strength to the final product. Fire retardants, pesticides, fungicides, colouring agents are examples of other additives. If the rice hulls constitute a high proportion, eg. over about 80%, of the filler particles, the addition of fire retardant may not be necessary since rice hulls do not support combustion, at least at normally experienced fire temperatures. This is believed to be due to the high silica content of rice hulls. The rice hulls tend to char rather than burn and this property of rice hulls is advantageous for ceiling panels or ceiling tiles and for other uses where this combustion resistant property is useful.

The process preferably utilises a binder which sets at an elevaed temperature although non-thenno setting binders can be used if desired-. The binder may be suitable thermosetting or thenino-curing resin binder such as a urea, formaldehyde or phenolic resin which incorporates a suitable catalyst. The preferred process includes the step of raising the temperature, preferably throughout the thickness of the mixture of the rice hulls and binder when the mixture is formed in the generally desired shape, which may i s be the final desired shape or an intermediate shape.

In the process, the mixture may be formned into the generally desired shape for formation of the ceiling panel in a batch process using a mould or die. For example the step of locating the mixture in the generally desired shape in the curing zone and the step of Conning the mixture into the generally desired shape may be effectively combined by feeding the mnixture into the mould which will when closed, constitute the curing zone.

However preferably the process is either a continuous or intermittent process in which the mixture is conveyed into and through the curing zone. In the preferred process, the step of locating the mixture -in the curing zone includes conveying the mixture in the generally COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19 04/10/2002 20:03 +613-9990-1337PAET TORYSRVAG PATENT ATTORNEY SERV PAGE 10/25 desired shape e.g. as a mat of mixture into the curing zone on a support surface, the curing zone being defined between opposed upper and lower pressure members which apply pressure to the shape on the support surface when located between the pressure members, the heating of the mixtur on the support surface occurring when the pressure members are compressing the shape on the support surface, the support surface being maintaned out of substantial heat exchange relationship with the lower one of the pressure members and the upper surface of the shape on the support surface being maintained out of substantial heat exchange relationship with the upper one of the pressure members so as to avoid any substantial differential heating effect on either surface of the shape until the pressure members apply pressure to the shape on the support surface.

This process of conveying the mixture into the curing zone may be a substantially continuous process in which the support surface comprises a support conveyor which conveys the mixture formed on the su'pport conveyor into the curing zone where the mixture is compressed as it is conveyed into and through the space between the opposed upper and lower pressure members. The upper and lower pressure members need not be movable but a tapering mouth may lead into the space between the pressure members which are spaced by a distance equal to the desired thickness of the final panel.

However in an alternative and preferred embodiment, the mixture is formed on a support surface, which may be a conveyor or other support base, and the mixture is conveyed into a curing zone defined between opposed and spaced apart upper and lower pressure members when the movement of the support surface is paused. The pressure members are then relatively moved towards each other to apply the pressure to the shape. With this aan~gement, the pressure members would be relatively tnoved apart. at the end of a heating 04/10/2002 20:03 +613-9890-1337PAET TORYSEVAG 1/2 PATENT ATTORNEY SERV PAGE 11/25 cycle when the binder has cured or has cured sufficiently for the body to retain the desired shape, e.g. the desired shape of the finished ceiling panel, whereafter the support surface is moved out of the curing zone, The maintenance of the support surface out of any substantial heat exchange relationship with the lower one of the pressure members and simultaneously out of heat exchange relationship with the upper pressure member during the process of locatinag the mixture in the curing zone is desirable to avoid any significant differential heating effect on either surface of the shape until the pressure members appiy pressure to the shape on the support surface.

it has been found that if some heating of, say, the lower surface of the shape on the support surface occurs e.g. due to the support surface contacting the lower pressure member through which heat is applied as the support surface is conveying the shape into the curing zone, some curing of the binder at the lower surface occurs prior to the application of pressure, and when the pressure is applied to compress the mixture, the binder at the lower surface has at least partially already cured. This leads to a "mnemory effect" causing the panel to curl upwardly after the product is removed from between the pressure members and moved out of the curing zone. The memory effect is believed to be a result of curing occurring in the centre and upper surface of the body while under pressure within the curing zone but at least some portion at the lower surface having already been cured by the time the pressure is applied. The rice hulls at the lower surface expand again after release of the pressure if the binder had cured before the pressure was applied and this causes the panel to bow upwardly. The converse would occur if the upper surface experienced any substantial 04/10/2002 28:03 +613-9690-1337PAET TORE SEYAE 1/2 PATENT ATTORNEY SERV PAGE 12/25 heating to cause at least some significant curing of the binder at the upper surface prior to the pressure being applied and prior to the heaing in the centre and at the lower surface.

Hence the Process is Preferably controlled So that differential heating on either surface of the shape is avoided prior to compression of the shape. In the preferred embodiment this is Preferably achieved by maintaining the support surface away from any significant heat exchange relationship with the lower pressure member by conduction of heat as a result of contact with that surface) and avoiding substantial heating of the upper surface from the upper pressure member by radiant heating if the upper surface is close to the upper pressure member). Once the shape is compressed between the pressure members it is not significant if the heating rates of the upper and lower surfaces differ since the entire mixture will be under pressure and the binder will cure to hold the final product in that shape. it is the partial curing of binder of uncompressed mixture prior to curing of the opposite face and remainder of the shape when under pressure that causes the bowing.

It has been found that the differential heating prior to pressure being applied leading to bowing of the forned product is primarily a problem with thinner panels, i.e. having thicknesses that will be expected to be useful for ceilig panels and ceiling tiles. Such thicknesses will generally be in the range of about 12 to 20mm. Substantially ticker panels are less likely to experience warping because the forces developed by the memory effect are unlikely to be sufficient to bow the panel.

The application of heat to the shape when compressed in the curing zone may be achieved by any suitable means or proces. For formation of typical thicknesses of ceiling panels (about 12-20 nan), conductive heating of the surfaces of the pressure members is thie most convenient and is effective to achieve the curing to, create a panel having sufficient 04/10/2002 20:03 +613-9898-1337PAET TORE SEYAE 1/2 PATENT ATTORNEY SERV PAGE 13/25 integrity to be handled and to maintain its shape during handling and use. As in AU-1 99670802, complete curing of the binder is not necessarily achieved in the curing zone and the product may be removed and processed under separate conditions to effect substantially complete curing of the binder so as to achieve maximum strength and integrity of the product. Further reference may be made to AU-199670802 for descriptions of other heating mechanisms, including RE inductive heating. That document also provides descriptions of extrusion processes which can be useable with the present innovation.

The process may include addition of a pH adj usting material, e.g. an alkaline material so as to adjust the pH of the final forned product. Natural rice hulls in their raw state can have a pH of about 7.7, although this can vary depkedng on the source of the rice crop.

However the binders, or the catalysts used in binders, are often acidic so that the final pH of the formed product can be for example in the range 5.9 to 6.3.

By adjusting the pH of the mixture, e.g. by adjusting the pH of the liquid binder, the formed body may have any desired pH consistent with the purpose for which the body is to be used. For most applications, e.g. products for the building industry, a substantially neutra pH, e.g. in the range 6.5 to 7.2 will be preferred. Addition of dolomite or lime, or like material, to the binder or to the muixture at the time of forming the mixture of the feed material and binder, may be sufficient to increase the pH to the desired level. Chemical pH adjusting agents may likewise be used. pH testing of the initial raw feed material is preferable so that the amount of pH adjusting additive can be determined to compensate for differing pH of the initial raw feed material- The panel formed by compressing a mixture composed of a high percentage of rice hulls, particularly substantially whole rice hulls, has a surface which has a random but 04/10/2002 20:03 +613-9890-1337PAET TTNySEYAG 142 PATENT ATTORNEY SERV PAGE 14/25 subst'antially uniform Pattern of concavities and passages formed by the shape of the rice hulls themnselves and by the interstices between the rice hulls (and other particulate fillers if used). This surface pattern as well as the cavities within the thickness of the panel contribute substantially to the acoustic insulating properties of the panel. The cavities throughout the thickness also contribute substantially to the thermal insulating properties. The surfacc pattern is desirable for ceiling panels or tiles. The surface pattern if desired can be augmented by subsequent puncturing of the surface e.g. by a tinied roller, although this is not believed necessary for most possible applications of the product of the present innovation (unlike prior ceiling tiles forned primarily of cellulose fibres). Patterns and/or edge profiles can be machined into the surfaces or edges e.g. by routing.

Although, the ceiling panels are desirably formed initially in the desired thickness the ceiling panels may be made of slices from a thicker slab of bound mixture. Slices of the desired thickness and size can be cut from the slab for the required ceiling panels. Such panels could then be machined to the required pattern and, if desired, shape of border.

Preferably the surfaces, or at least one of the opposed broad faces, of the panel are coated with a suitable coating material so as to Provide additional binding where applied to the panel- This binding effect need not necessarily be significant structurally, i.e. to enhance the integrity to enable the panel to be handled and used, but may be sufficient to bind the surface to reduce the particles being dislodged or particles Whiing from the surface during handling, installation and during subsequent periods of use. That is, the coating may comprise little more than an effective surface sealer or binder for materials included in the composition of the panel. The coating is applied so as not to substantially fill or seal 04/10/2002 20:03 +613-9890-1337 PATENT ATTORNEY SERV PAGE 15/25 interstices between particles of filler so that the desirable aesthetic and insulating properties of the panel prior to coating are substantially maintained after the coating is applied.

In the preferred embodiment, the coating is a powder coating which is applied to the surface of the panel in powder form, e.g. using conventional powder coating processes which usually involve electrostatically charging the particles so that they are attracted to and electrostatically adhere to the surface of the panel. The powder coating is subsequently cured or fused so as to permanently adhere to the panel and to other particles whereby the coating is stabilised. Powder coating does not result in any substantial penetration of the coating material into the particulate filler material or into the interstices between the particles of filler, thereby retaining the aesthetic and insulating properties. This is unlike liquid based coating such as paints, resins, varnishes, lacquers, or even plaster in high water or slurry form. Liquid based coating processes usually involve substantial absorption of the coating material as soon as the coating spray is applied and this results in substantial closing of the passages and interstices and filling of concavities. Powder coating will more closely follow the existing surface contours and will fuse in the same condition. The accompanying illustrations, mentioned below, show in Figs, 2 and 3, the overall pattern or texture of a ceiling tile manufactured in accordance with the present innovation, including in Fig. 3 a magnified close up view of a portion of the surface which has been powder coated and the coating fused in accordance with the preferred embodiment.

The thickness, shape and profile of the ceiling panel can be determined during the curing process, e.g. by providing pressure members which function to dies to define the shape of the panel formed. This can be an alternative to machining, such as routing, For example the shape can be compressed to a greater extent to a reduced thickness around the 04/18/2002 20:03 +613-9890-1337PTETAORYSEVPE 1/2 PATENT ATTORNEY SERV PAGE 16/25 edges or along some edges of the panel being formed. This production of a denser and thinner edge portion of the panel can provide greater stuctural strength at the edges. Also, such profiled edges may be useful for installing the ceiling panels e.g. where they are used in suspended ceiling systems having suspended linear straps on which the tile edges rest to form a ceiling. The accompanying illustrations depict a ceiling tile having such profiled edges.

Although the denser thinner edge or border around or across the panel may be formed into the ceiling panel at the forming station, prior to or concurrently with the pressing or other methods of forming the ceiling panel, this same edging or border or pattern on the panel surface(s) could be machined or mouted into the ceiling panel, this would result in a board or ceiling tile of uniform density, irrespective of patterned surface or edging.

Possible and preferred features of the present innovation and invention are illustrated in the accompanying figures. However it is to be understood that the features illustrated in or described wit reference to the figures are not to be construed as limniting on the scope of the innovation or invention. In the figures: Fig. 1 shows schematically a flow chart for a sequence of process operations according to the preferred embodiment of the present innovation, Fig. 2 shows a ceiling panel or a fragment of a ceiling panel according to the present innovation, and Fig. 3 shows a magnified detail of a corner of a ceiling panel according to the present innovation which has been powder coated.

The sequence and nature of the proces and operations depicted in the flow chart of Fig. 1 can be understood by referring to the preceding description of the present innovations and inventions.

04/10/2002 20:03 +613-9890-1337PAET TORYSEYAG 172 PATENT ATTORNEY SERV PAGE 17/25 The resulting product depicted in Figs. 2 and 3 has good integrity for handling and use and the surface coating seals and reduces dislodgement of particles during handling and use, The coating also increases the integrity and strength of the product.

Ceiling tiles used at present in buildings are often made from cellulose material (e.g.

pulverised or pulped paper) mixed with gypsum and other additives and produced by making a slurry which is spread and dried. Such ceiling tiles are intolerant to wetting and any exposure to liquid causes staining and loss of integrity. Ceramic ceiling tiles are known but these are expensive and heavy. On the other hand, the ceiling tile produced according to the present innovation and depicted in Figs. 2 and 3 has high liquid tolerance as the rice hulls ame inherendly highly water resistant as are the binders that are preferably used, whether thenno setting or non-thermo setting. A ceiling tile manufactured according to the present innovation has been placed in boiling water for 24 hours, resulting in only very small swelling (about occurring but without loss of any significant internal bonding strength.

After the 24 hour exposure in boiling water and allowing to dry, the tile showed no evident physical change in shap or strength. The surface coating enables cleaning by washing if any staining occurs.

It wil be appreciated that variations and modifications to the product and processes described herein can be made- For example only, variations are possible with details of the composition of the particulate filler (subject to maintenance of the large proportion of rice hulls), the types of binder used to meet the requirements for the manufacture and for the final product, and process parameters in the manufacture.

For example sound absorption or reflection properties of a ceiling tile can be tailored to provide attenuation or reflection of particular frequencies of sound and sound pressure 04/10/2002 20:03 +613-9890-1337PAET TORYSRVPG 182 PATENT ATTORNEY SERV PAGE 18/25 levels, Such properties can be adjusted by changing the thickness and density of the panel and also by selection of the coating applied to the surface. Also, the patterning of the surface can be modified as mentioned herein tQ modify properties.

It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and preferred embodiment(s) of the invention as herein described without departing from the spirit and scope of the innovation and invention as defined in the claims.

Claims (5)

1. A ceiling panel composed of a particulate filler having a large proportion of rice hulls and a binder which is mixed with the Particulate filler and which is set or cured to bind the filler particles together to form a panel having sufficient integrity to be handled and maintain its shape during handling and use, the mixture of the filler and the binder having been formed into a generally desired shape and setting or curing of the binder being at least initiated or progressed while the mixture is in the desired shape, the ceiling panel including a cating which is applied to the panel on at least one face thereof, the coating providing additional binding wh1ere applied to the panel, the coating being applied without substantially filling or sealing interstices between filler particles whereby desired aesthetic and insulating properties of the panel before being coated are maintained to a significant extent after the coating is applied.

2. The ceiling panel of Claim 1 wherein the coating is a powder coating which is applied in powder forn to the panel and is subsequently cured or fused to adhere and to stabilise the coating without substantial penetration into the particles of' the filler or into interstices between particles of the filler.

3. The ceiling panel of Claim 1 or 2 wherein edges of the panel have a reduced thickness compared to the major part of the surtee area, the reduced thickness edges being formed during manufacture by compressing the edges to a greater extent to produce denser thinner edge portions providing greater structural strength at those edges. 16 COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19 19/04/2004 14:54 +613-9890-1337 PATENT ATTORNEY SERV PAGE 10/18

4. The ceiling panel of Claim 1 or 2 wherein edges of the panel have a reduced thickness compared to the major part of the surface area, the reduced thickness edges being formed after manufacture of the panel by machining into the panel edges-

5. A ceiling panel as claimed in Claim 1 and substantially as herein before described with particular reference to Figs. 2 and 3 of the drawings, Dated this 19* day of April 2004 PATENT ATTORNEY SERVICES Attorneys for RICHARD L LEWELLIN 17 COMS ID No: SMBI-00712519 Received by IP Australia: Time 15:05 Date 2004-04-19