mcinnes patents AUSTRALIAN PATENTS ACT 1990 COMPLETE INNOVATION PATENT SPECIFICATION TITLE: Fire-Rated Paper Faced Board APPLICANT: CSR Building Products Limited Level 4, 9 Help Street Chatswood NSW 2067 INVENTOR: Bill Thompson Level 4, 9 Help Street Chatswood NSW 2067 ADDRESS FOR HODGKINSON McINNES PATENTS SERVICE: Patent & Trade Mark Attorneys Levels 21, 201 Elizabeth Street Sydney NSW 2000 HMcIP REFERENCE: PI20831AUOO 2 FIRE-RATED PAPER FACED BOARD TECHNICAL FIELD 5 The present invention relates to a fire rated paper faced construction board. The invention more particularly relates to a construction board composed of a core of gypsum plaster or stucco in combination with a relatively high proportion by weight of recycled gypsum and waste paper 10 sludge incineration ash and/or fly ash, which is encased by a heavy duty facing paper and is made in a continuous ribbon process. BACKGROUND TO THE INVENTION 15 There is a great emphasis on environmentally sustainable building techniques and building products in today's construction industry. This is particularly the case where Government bodies and agencies provide financial incentives to builders when environmentally sustainable building 20 techniques and building products are used in the construction and renovation of buildings and other structures. Accordingly, there is a great need to produce building materials that are environmentally sustainable. One particularly suitable way to ensure 25 that new building materials are environmentally sustainable is to utilise recycled materials in the manufacture of new building materials. The use of recycled materials in this way is common and is widely known in the construction industry. However, there is always a need to provide new materials with improved performance and greater levels of recycled 30 materials to ensure that new and improved environmentally sustainable products are produced. Indeed, with a greater emphasis placed on environmental sustainability, the "greener" that building materials become, 3 the greater the benefit for the builders who use these materials in the construction and renovation of buildings and the like. Within the construction industry, it has been generally known to use 5 plasterboards for the construction of non-load carrying dividing walls and as interior cladding in connection with renovation and/or insulation of exterior walls. There are three main areas in which plasterboard waste is generated in the construction industry, which are as follows: 10 1. New plaster board: during the manufacturing process parameters or machinery may cause quality problems or the like which necessitates that the production must be destroyed; 2. During construction the plaster boards are cut to fit and the cut i5 aways are usually thrown away as waste; and 3. Waste generated from the demolition of a building. Due to increased prices on the raw materials, such as "virgin" 20 gypsum to produce new plasterboard panels, as well as ever stricter environmental demands, especially regarding the control of landfill sites, the feasibility of reusing demolished materials has become economically viable and particularly encouraged. 25 It is commonly accepted within the building industry that new plasterboards that are manufactured utilising recycled waste gypsum material should only contain less than about 25 per cent by weight of recycled waste gypsum material. However, there is a desire to increase the percentage of recycled material in today's new construction boards to 30 increase the environmental sustainability of the boards and increase the "green" rating of the boards. There has therefore been some investigation into other recycled materials that can be added to construction boards to 4 increase the green rating and environmental sustainability of the boards. One particularly suitable material that has been identified is coal fly ash. Fly ash is one of the residues generated in the combustion of coal. 5 Depending upon the source and makeup of the coal being burned, the components of the fly ash produced vary considerably, but all fly ash includes substantial amounts of silica (silicon dioxide, SiO 2 ) (both amorphous and crystalline) and lime (calcium oxide, CaO). Fly ash is commonly used to supplement Portland cement in concrete production, 10 where it can bring both technological and economic benefits, and is increasingly finding use in synthesis of geopolymers and zeolites. There are two main types of fly ash, Class F fly ash and Class C fly ash. The chief difference between these classes is the amount of calcium, silica, alumina, and iron content in the ash. The chemical properties of the fly ash are 15 largely influenced by the chemical content of the coal burned (i.e., anthracite, bituminous, and lignite). The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This fly ash is pozzolanic in nature, and contains 20 less than 10% lime (CaO). Possessing pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated lime, with the presence of water in order to react and produce cementitious compounds. Alternatively, the addition of a chemical activator such as sodium silicate (water glass) to a 25 Class F ash can lead to the formation of a geopolymer. On the other hand, fly ash produced from the burning of younger lignite or sub-bituminous coal, in addition to having pozzolanic properties, also has some self-cementing properties. In the presence of water, Class C 30 fly ash will harden and gain strength over time. Class C fly ash generally contains more than 2 0 % lime (CaO). Unlike Class F, self-cementing Class C fly ash does not require an activator. Alkali and sulfate (SO 4 ) contents are generally higher in Class C fly ashes.
5 In the past, fly ash produced from coal combustion was simply entrained in flue gases and dispersed into the atmosphere. This created environmental and health concerns that prompted laws which have reduced 5 fly ash emissions to less than 1% of ash produced. Worldwide, more than 65% of fly ash produced from coal power stations is disposed of in landfills. Accordingly, there has been extensive investigation into more effective uses of this waste fly ash, rather than simply disposing of it in landfills. 10 The recycling of fly ash has become an increasing concern in recent years due to increasing landfill costs and current interest in sustainable development. In 2005, coal-fired power plants in the United States of America reported producing 71.1 million tons of fly ash, of which 29.1 million tons was reused in various applications. If the nearly 42 million tons is of unused fly ash had been recycled, it would have reduced the need for approximately 3.39x 107 m 3 of landfill space. Other environmental benefits to recycling fly ash includes reducing the demand for virgin materials that would need quarrying and substituting for materials that may be energy intensive to create (such as Portland cement). 20 The reuse of fly ash as an engineering material primarily stems from its pozzolanic nature, spherical shape, and relative uniformity. Fly ash recycling has conventionally included usage in Portland cement and groLit, embankments and structural fill, waste stabilization and solidifaction, raw 25 feed for cement clinkers, mine reclaimation, stabilization of soft soils, road sub-base, aggregate, flowable fill, mineral filler in asphaltic concrete arid other applications include cellular concrete, geopolymers, roofing tiles, paints, metal castings and filler in wood and plastic products as well as use in the manufacture of construction plasterboards. 30 For example, United States patent no. US 4,403,006 describes a gypsum board manufactured in a conventional process consisting essentially of a monolithic cellular core of set gypsum and a fibrous cover sheet 6 encasement. The gypsum core has incorporated therein fly ash in an amount of about 1 - 20% by weight of stucco in the gypsum slurry used in forming the board. The addition of the fly ash to the gypsum core greatly improves the sag resistance properties of the board. 5 Another example of utilising fly ash in manufacturing construction boards is described in United States patent no. US 4,812,169, which describes a fire-resistant, light weight construction material that is manufactured by subjecting fly ash and/or paper sludge incineration ash to 10 a swelling treatment with a mineral acid to prepare a slurry, and then kneading, shaping and hardening the slurry. Plasterboard is conventionally produced by enclosing a core of an aqueous slurry of calcined gypsum and other materials between two large 15 sheets of cover paper, also known as plasterboard liner (PBL). Various types of cover paper are known in the art. The continuous envelope enclosing the aqueous slurry is then supported on a conveyor called a "setting belt" for sufficient time to gain rigidity. After the gypsum slurry or stucco has set (i.e. reacted with the water from the aqueous slurry) and dried, the sheet is 20 transversely cut into standard sizes. This forming and cutting is typically carried out in a "continuous ribbon process". Therefore it would be advantageous to provide a construction board composed of gypsum plaster or stucco and a relatively high proportion by 25 weight of recycled waste gypsum and waste paper sludge incineration ash or fly ash encased by a heavy duty facing paper and made in a continuous ribbon process. This would overcome at least some of the disadvantages of previously known approaches in this field, or would provide a useful alternative. 30 7 SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided a fire rated paper faced construction board having a set gypsum stucco core 5 having incorporated therein in an amount greater than about 20% by weight, recycled waste gypsum material, paper sludge incineration ash and/or coal fly ash, said core having a paper lining and wherein said board is made in a continuous ribbon process. 10 Preferably, the paper lining is of a heavy duty paper lining having a density greater than or equal to 220g/m 2 to provide dent and scuff resistance. The core further includes fibre material, which is preferably a plurality is of fibreglass strands. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 20 The present invention relates to a construction board 1 composed of gypsum plaster or stucco 2 and a relatively high proportion by weight of recycled waste gypsum 3 and waste paper sludge incineration ash 4 or fly ash 5 encased by a heavy duty facing paper 6 and made in a continuous ribbon process. 25 Each of the construction boards 1 are produced by enclosing a core of an aqueous slurry of calcined gypsum or stucco 2 in combination with recycled waste gypsum material 3 and waste paper sludge incineration ash 4 and/or fly ash 5 between two large sheets of heavy duty facing paper 6, 30 also known as plasterboard liner (PBL). The waste gypsum material 3 and paper sludge incineration ash 4 and/or coal fly ash 5 are present in an amount greater than about 2 0% by weight of the calcined gypsum or stucco 2.
8 Various types of cover paper are known in the art. However, it is preferred that the facing paper is a heavy duty paper lining that provides the construction boards 1 with dent and scuff resistance. The paper lining 1 5 preferably has a density greater than or equal to 220g/m 2 , although paper of any suitable density may be utilised. The two large sheets of heavy duty facing paper 6, which form a continuous envelope that encloses the aqueous slurry are then supported on 10 a conveyor called a "setting belt" for sufficient time for the aqueous slurry of calcined gypsum or stucco 2 to gain rigidity. After the gypsum slurry or stucco 2 has set (i.e. reacted with the water from the aqueous slurry) and dried, a large sheet of construction board 1 is produced. This large sheet is transversely cut into standard sizes. This forming and cutting is typically 15 carried out in a "continuous ribbon process". In another embodiment of the present invention, whilst the waste gypsum material 3 and paper sludge incineration ash 4 and/or coal fly ash 5 are present in the construction boards 1, these materials are not necessarily 20 present in an amount greater than about 20% by weight of the calcined gypsum or stucco 2. In this embodiment of the invention, the density of the boards are greater than or equal to 1000kg/m 3 and the boards provide both fire and acoustic resistant properties. It is preferred that the boards 1 achieve a fire rating under set out under the provisions of Australian 25 standard AS/NZS1530 part 4 (or equivalent). The boards 1 according to this alternative embodiment are similarly produced by enclosing a core of an aqueous slurry of calcined gypsum or stucco 2 in combination with recycled waste gypsum material 3 and waste 30 paper sludge incineration ash 4 and/or fly ash 5 between two large sheets of heavy duty facing paper 6, also known as plasterboard liner (PBL).
9 It will be apparent that obvious variations or modifications may be made which are in accordance with the spirit of the invention and which are intended to be part of the invention, and any such obvious variations or modifications are therefore within the scope of the invention. 5 In this specification, unless the context clearly indicates otherwise, the term "comprising" has the non-exclusive meaning of the word, in the sense of "including at least" rather than the exclusive meaning in the sense of "consisting only of". The same applies with corresponding grammatical 10 changes to other forms of the word such as "comprise", "comprises" and so on. EXAMPLES 15 Two variants of the fire rated paper faced board have been produced to verify the attributes which result from high core density, the addition of fibreglass and recycled materials, and the use of heavy duty paper. 20 In the first example, a 13mm thick, high density board was produced, which was shown to meet the fire rating requirements of AS/NZS 1530.part 4 when used in frame construction. The board had a density of greater than 1000kg/m 3 and achieved higher levels of acoustic and dent resistance performance than conventional plasterboard. 25 In the second example, a board was produced with a core comprising 22% by weight recycled materials, consisting of recycled gypsum and fly ash. This product was tested and shown to meet the fire rating requirements of AS/NZS 1530.part 4 when used in frame construction. 30 10 Example 1 A first batch of construction boards were produced by enclosing a core of an aqueous slurry of calcined gypsum in an amount of 7.6kg/m 2 by 5 weight in combination with recycled waste gypsum material 0.2kg/m 2 by weight and fly ash in an amount of 30.7% by weight between two large sheets of heavy duty facing paper, having a density of 240grams/m 2 . The two large sheets of heavy duty facing paper, which forn a 10 continuous envelope that encloses the aqueous slurry were then supported on a conveyor called a "setting belt" for sufficient time for the aqueous slurry of calcined gypsum to gain rigidity. This took approximately 8 minutes. After the gypsum slurry set (i.e. reacted with the water from the aqueous slurry) and dried, a large sheet of construction board was 15 produced. This large sheet was then transversely cut into standard sizes. This forming and cutting was carried out in a "continuous ribbon process". Example 2 20 A second batch of construction boards were produced by enclosing a core of an aqueous slurry of calcined gypsum in an amount of 7.4kg/m2 in combination with recycled waste gypsum material in an amount of 0.2kg/m 2 , fly ash in an amount of 20% by weight and fibreglass strands between two large sheets of heavy duty facing paper, having a density of 25 240grams/m 2 . The slurry material used in the manufacture of these constructions boards had a fibreglass content of approximately 33g/m 2 . The two large sheets of heavy duty facing paper, which form a continuous envelope that encloses the aqueous slurry were then supported 30 on a conveyor called a "setting belt" for sufficient time for the aqueous slurry of calcined gypsum to gain rigidity. This took approximately 8 minutes. After the gypsum slurry set (i.e. reacted with the water from the aqueous slurry) and dried, a large sheet of construction board Was 11 produced. This large sheet was then transversely cut into standard sizes. This forming and cutting was carried out in a "continuous ribbon process", 5 INDUSTRIAL APPLICABILITY The invention can be utilised in a fire rated paper faced construction board. More particularly, the invention can be utilised in a construction board composed of gypsum plaster in combination with a relatively high 10 proportion by weight of recycled waste gypsum and paper sludge incineration ash and/or fly ash encased by a heavy duty facing paper that is made in a continuous ribbon process.