WO2011078708A1

WO2011078708A1 - Carbon plaster board

Info

Publication number: WO2011078708A1
Application number: PCT/NZ2010/000265
Authority: WO
Inventors: Gordon John Palmer Lidgard
Original assignee: Carbon Credit Corporation New Zealand Limited
Priority date: 2009-12-24
Filing date: 2010-12-23
Publication date: 2011-06-30

Abstract

The invention is concerned with gypsum-based plaster board or gypsum cardboards or other gypsum plaster mouldings that incorporate carbon, and preferably charcoal in the form of either powder or granules or both, as a component or filler of the gypsum core, for use as building components in any buildings for walls, ceilings or other enclosed space liners such as cupboards, duct ways, and any other suitable construction applications. The present invention is concerned with methods of producing such gypsum-based plaster, and also the resulting plaster boards themselves. Using charcoal in plaster boards or mouldings provides building components with some or all of the properties of charcoal such as: improved thermal insulation, air purification, removal of odours, shielding attenuation, sound proofing, emission of far-infrared rays and anions, and/or adsorption of volatile organic compounds used in paints and adhesives.

Description

"CARBON PLASTER BOARD" FIELD OF THE INVENTION

The invention relates to plaster boards and in particular to carbon based plaster boards. BACKGROUND OF THE INVENTION

Many different types of board are used in the building and construction industry. Plasterboards are commonly used for finish construction of interior walls and ceilings of buildings. Panels of plasterboard are made of gypsum plaster/plaster of paris pressed between two thick sheets of paper. Gypsum plaster/plaster of Paris is the semi-hydrous form of calcium sulphate (CaS04^-1/2 H20). Commonly raw gypsum, CaS04-2 H20, is used and should be calcined before use.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

It is an object of the present invention to provide plaster board with desirable properties and/or methods of producing such plaster boards, and/ or or to at least provide the public with a useful choice.

SUMMARY OF INVENTION

In a first aspect the invention may broadly be said to consist of a method of forming a board comprising the steps of: mixing gypsum plaster, charcoal and water to form a plasterboard mixture and allowing the plasterboard mixture to set, wherein the charcoal comprises charcoal powder.

Preferably the method further comprising prior to allowing the mixture to set, placing the plasterboard mixture between two sheets of cover material

Preferably the step of mixing further comprises mixing at least one foaming agent with the gypsum plaster, the charcoal and the water. Preferably the step of mixing comprises:

mixing the gypsum plaster, the charcoal powder, and the water in a mixer and adding a preformed foam comprising one or more foaming agents and water.

Alternatively the step of mixing comprises:

mixing the gypsum plaster, the charcoal powder, a foaming agent and the water in a mixer to form a slurry, and then adding compressed gas to the slurry to create air entrainment.

Preferably the foaming agent is sodium lauryl sulphate.

Preferably the step of mixing is carried out in an air entrainment mixer.

In one embodiment the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal powder to 0.6 - 2 parts water.

Preferably the dry mass based proportions of the plasterboard mixture are 1.0 part gypsum plaster to 0.5 parts charcoal powder to 1.0 part water.

In one embodiment the charcoal further comprises charcoal granules.

r

Preferably the step of mixing comprises:

mixing the gypsum plaster, the charcoal powder, a foaming agent and the water in an air entrainment mixer to form a first mixture, and

passing the first mixture into a second mixer, and

mixing the charcoal granules with the first mixture in the second mixer to form the plasterboard mixture.

Preferably the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01 - 0.75 parts charcoal powder to 0.01 - 0.75 parts charcoal granules to 0.6 - 1.25 parts water.

Preferably the dry mass based proportions of the plasterboard mixture are 2.0 parts gypsum plaster to 0.25 parts charcoal powder to 0.25 parts charcoal granules to 0.9 parts water. In one embodiment the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.5— 1.5 charcoal to 0.5— 1.5 water, and wherein the charcoal is charcoal powder or charcoal powder and charcoal granules.

Preferably the dry mass based proportions of the plasterboard mixture are 2.0 parts water to 1.0 part charcoal to 1.0 part water.

In one embodiment the dry mass based proportions of the plasterboard mixture are 1.5 - 2.5 parts gypsum plaster to 0.5 - 0.9 parts charcoal powder to 0.1- 0.5 parts charcoal granules to 1 - 1.5 parts water.

Preferably the proportions of the plasterboard mixture are 2.0 parts gypsum plaster to 0.7 parts charcoal powder to 0.3 parts charcoal granules to 1.25 parts water.

In one embodiment the step of mixing consists of: mixing gypsum plaster, charcoal granules and water to form a facing layer plasterboard mixture, and mixing gypsum plaster, the charcoal powder and water to form a backing layer plasterboard mixture.

Preferably the step of placing the plasterboard mixture between two sheets of cover material comprises: extruding the facing layer mixture onto a sheet of cover material, and extruding the backing layer mixture onto the facing layer mixture.

Preferably the dry mass based proportions of the facing layer mixture are 2.5— 3.5. parts gypsum plaster to 0.01— 1.5 parts charcoal granules to 0.01— 1.5 parts water and the dry mass based proportions of the backing layer mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal powder to 1 - 2 parts water.

Preferably the dry mass based proportion of the facing layer mixture are 3.0 parts gypsum plaster to 1.0 part charcoal granules to 1.0 part water and the dry mass based proportions of the backing layer mixture are 2.0 parts gypsum plaster to 1.0 part charcoal powder to 1.5 parts water.

The charcoal granules may consist of fine and medium grade granules.

Alternatively, the charcoal granules consist of coarse grade granules. Preferably the method of forming the board further comprises removing a sheet of cover material adjacent the facing layer after the mixtures have set and shaving an exposed surface of the facing layer to expose the charcoal.

Preferably for any one of the above embodiments at least a portion of the charcoal is hydrated to increase the mass of the charcoal prior to mixing the charcoal with water and gypsum plaster.

In any one of the above embodiments, the charcoal may be soaked in water for a period of time to hydrate the charcoal. The water may be at boiling temperature. Alternatively, the charcoal is placed in a vacuum chamber and water is applied under pressure to the chamber to replace air voids and hydrate the charcoal.

Preferably the step of placing the plasterboard mixture between two sheets of cover material comprises extruding the plasterboard mixture in between the sheets of cover material and pressing on either side of the sheets of cover material at a moulding station to form a mould.

Preferably the step of exteuding comprises: forming an edge mix of charcoal, gypsum plaster and water, wherein the charcoal comprises charcoal powder or fine grade charcoal granules or both, extruding the edge mix along the edges of the sheets of cover material, extruding one or more plasterboard mixtures within the edge mix before being pressed and formed into a mould.

Preferably the method of forming the board further comprises after forming the mould, allowing the mould to set, and cutting the mould into one or more boards to be placed in a baking kiln for a period of time to harden.

Preferably prior to mixing charcoal is filtered through a sieve screen having a mesh width of 0.4- 0.5mm to collect the charcoal powder for mixing.

Alternatively or in addition prior, to mixing charcoal is exposed to a blower to separate and collect the charcoal powder for mixing.

In a second aspect the invention may broadly be said to consist of a board formed from using any of the above methods. In a third aspect the invention may broadly be said to consist of a method of forming a board comprising the steps of: mixing gypsum plaster, charcoal and water to form a plasterboard mixture and allowing the plasterboard mixture to set, wherein the charcoal comprises charcoal granules.

Preferably the method further comprises prior to allowing the mixture to set, placing the plasterboard mixture between two sheets of cover material.

In one embodiment the plasterboard mixture comprises only fine and medium grade charcoal granules.

Preferably the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal granules to 0.5— 2 parts water.

Preferably the dry mass based proportions of the plasterboard mixture are 1.0 part gypsum plaster to 0.5 parts charcoal granules to 1.0 part water.

In one embodiment the plasterboard mixture comprises course grade charcoal granules.

Preferably the dry mass based proportions of the plasterboard mixture are 1.0— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal granules to 0.5— 2 parts water.

Preferably the dry mass based proportions of the plasterboard mixture are 1.3 - 2.0 part gypsum plaster to 1.0 parts charcoal granules to 0.8 - 1.0 part water.

In one embodiment the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 1.5 charcoal to 0.5 - 1.5 water.

Preferably in any one of the above embodiments of the second aspect at least a portion of the charcoal is hydrated to increase the mass of the charcoal prior to mixing the charcoal with water and gypsum plaster.

In any one of the above embodiments the charcoal may be soaked in water for a period of time to hydrate the charcoal. The water may be at boiling temperature. Alternatively the charcoal is placed in a vacuum chamber and water is applied under pressure to the chamber to replace air voids and hydrate the charcoal.

Preferably the step of placing the plasterboard mixture between two sheets of cover material comprises: extruding the plasterboard mixture between two sheets of cover material and pressing on either side of the sheets to form a mould.

Preferably the method further comprises: forming an edge mix of charcoal, gypsum plaster and water, wherein the charcoal comprises charcoal powder or fine grade charcoal granules or both, and extruding the edge mix along the edges of the sheets of cover material, the plasterboard mixture then being is extruded within the edge mix before being pressed and formed into a mould.

Preferably the method further comprising after forming the mould, the steps of allowing the mould to set, and cutting the mould into one or more boards to be placed in a baking kiln for a period of time to harden.

In a fourth aspect the invention may broadly be said to consist of a board formed from any one of the methods of the third aspect.

The terms plaster or gypsum plaster or plaster of Paris as used in this specification mean gypsum plaster.

The term plasterboard is also commonly also known as drywall, gypsum board, wallboard, Gibraltar board or gib (GIB being a trademark of Winstone Wallboards), rock lath, Sheetrock, gyproc, pladur (Spain), rigips (Germany and central Europe), alcipan (Turkey) placoplatre (France), and its use in this specification is intended to cover all of the above terms as well as others names known in the industry for the same product. When reference is made to any such board in the specification it is also intended to cover gypsum plaster mouldings and gypsum plaster cardboards.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

The term "comprising" as used in this specification and claims means "consisting at least in part of. When interpreting each statement in this specification and claims that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which:

Figure la is a flow chart showing a method of forming a plaster board of the invention;

Figure lb shows a production line for forming a board using the method of figure la;

Figure 2 is a flow chart showing a method of forming a generic plaster mix of the invention;

Figure 3 is a flow chart showing a method of grounding and separating charcoal; _*

Figure 4 is a flow chart showing the steps of forming a plaster mix for a mixed graded carbon board embodiment of the invention;

Figure 5 is a flow chart showing the steps of extruding a plaster mix of a dual density impact board embodiment of the invention;

Figure 6 is a flow chart showing the steps of preventing floating and of mixing and extruding a plaster mix of a dual density decorative board embodiment of the invention;

Figure 7 is a flow chart showing the initial steps of forming a plaster board of the invention having an edge mix; Figure 8 shows an image of a decorative board embodiment of the invention;

Figure 9 shows a perspective view of a plaster board of the invention;

Figure 10 shows a cross sectional view of a dual density board incorporating an edge mix;

Figure 11 is a graph demonstrating moisture adsorption in carbon and standard type gypsum plasterboards;

Figure. 12 is a graph demonstrating moisture adsorption in carbon and standard type gypsum plasterboards in thermal insulation test; and

Figure 13 is a graph demonstrating fire resistant properties of carbon and standard type gypsum plasterboards.

DISCLOSURE OF THE INVENTION

Referring to figure 9, the invention is concerned with gypsum-based plaster board 1 or gypsum cardboards or other gypsum plaster mouldings (hereinafter: "plaster board") that incorporate carbon, and preferably charcoal in the form of either powder 3a or granules 3b or both, as a component or filler of the gypsum core 2, for use as building components in any buildings for walls, ceilings or other enclosed space liners such as cupboards, duct ways, and any other suitable construction applications. The plaster board 1 will generally comprises a facing and backing sheet (4 and 5 respectively) but as will be described later on in the specification the facing sheet may not be required for certain boards. The present invention is concerned with methods of producing such gypsum-based plaster, and also the resulting plaster boards themselves.

Using charcoal in the boards or mouldings provides these building components with some or all of the properties of charcoal such as: improved thermal insulation, air purification, removal of odours, shielding attenuation, sound proofing, emission of far-infrared rays and anions, and/or adsorption of volatile organic compounds used in paints and adhesives. Furthermore, by using charcoal the invention provides a means of sequestering carbon, and also a means of providing a building component with some or all of the properties of charcoal. Density of Charcoal and Methods of Production

There are many different ways to make charcoal, most of which involve baking biomass in the absence of air to drive off volatile gasses, leaving carbon behind. This process is called thermal decomposition, or carbonisation, and it comes in three main varieties: pyrolysis, gasification and hydrothermal carbonization. These methods produce energy in the form of gas or oil along with the charcoal. The term charcoal is intended to include biochar and other forms of charcoal produced using methods known in the art.

The applicant's tests described in this document are related (but not limited to), charcoal produced by the carbonisation of tree wood.

There are two broad categories of charcoal: black charcoal (low/ medium density) and white charcoal (high density).

Black charcoal is the most common and has a relatively low to medium density and floats well in water. Black charcoal is usually used in barbeques, metal smelting and blacksmithing. One common method of making black charcoal involves carbonising wood at temperatures between approximately 400°C and 700°C, sealing the kiln in which the wood is carbonised until burning stops and slowly dissipating the heat. The final density of the charcoal produced varies depending on the type and density of wood and pyrolysis method used. Typical good quality hard wood medium density charcoal is approximately 0.6g/ml. Densities of black charcoal however typically range between 0.4g/ml and 0.75g/ml. In this specification, the term black charcoal refers to such relatively low/ medium density charcoals either produced using a method similar to that described above or using a different method but resulting in similar densities. Preferably whatever method used, the black charcoal has a density of between 0.4g/ml and 0.75g/ml.

White charcoal is a relatively high density type charcoal, also known as "binchotan". The traditional method of making white charcoal (developed in Wakayama, Japan a few centuries ago) involves harvesting hard and dense wood (such as oak for example) that is cut to a suitable size and then using a kiln to char the dense wood at a relatively low temperature (around 400-500°C) and/ or with no oxygen for some time (this can be up to eight days for example). Small wood branches from the harvested wood can be used to create a heat fire and heat the kiln. After the so called 'soaking period' the wood becomes carbonised at which point near the end of the process the temperature of the kiln is raised to around 1000°C or more to make the wood orange hot. The charcoal is then pulled out and quickly smothered with a cooling powder. This sudden drop in temperature stops the combustion process. The powder may be a mix of damp sand, soil and ash for example; however any other suitable incombustible fine material could be used instead. This gives a whitish residue on the surface of the hard charcoal, hence the name "white charcoal". The charcoal can be separated and dusted at this point to give the desired high density white charcoal. More modern methods follow the same principle, but can raise the temperature of the dense wood to 1200°C for an extended period, and excluding oxygen prior to rapid cooling. This gives a very hard charcoal with especially high free carbon content. High density white charcoal that is of relatively good quality typically has a cut surface that shines like black diamonds and gives a metallic ring when struck.

A good grade of these high density type charcoals typically will not tend to float in water, with a dry density of approximately 1.06g/ml. In this specification however, high density charcoal can be broadly classified as having a dry density of 0.75g/ml or higher, but preferably 0.9g/ml or higher. Japanese Oak Quercus philyl raeoides and Indonesian Red Mangrove, (Kachi) Rhi^ophora piculata are examples of wood used to make such charcoals.

As will be discussed in more detail later on in the specification, these specially prepared high density charcoals may be preferred in some embodiments of carbon plasterboards. For instance, high density charcoal (dependent on granule size) is capable of eliminating or at least reducing the floating effect of charcoal in the plaster mix.

Charcoal Size

Charcoal can be prepared for use in the plaster board manufacture process by either crushing or milling. The crushing or milling process provides charcoal of differing particle sizes. Particle sizes within a specified range are called grades in this specification, (or fractions); for example: charcoal particle sizes from 0.5mm average diameter to 2.5mm average diameter, are called: 0.5-2.5 fine grade. On average, this fine grade will be retained on a sieve with a mesh size of around 0.4mm, but will pass through a mesh size of around 2.3mm.

For this specification we will use the term grades and consider separating the charcoal into four grades for comparative purposes, each grade may provide the board with specific properties. However the grades used in practice may be different in size and distribution and any combination of grades may be used separately or in any combination to make a board with the desired properties. Charcoal Powder

1. Powder Grade

Charcoal powder is the finest grade of the milled or crushed charcoal, consisting of particles that will pass through a fine sieve screen having a mesh width of approximately 0.4— 0.5 mm, therefore will have a particle size of a few microns or less and up to (but not limited to) approximately 0.5mm average diameter.

Charcoal Granules

2. Fine Grade

Charcoal particle sizes from 0.5mm average diameter to 2.5mm average diameter. This fine grade will be retained on a sieve screen having a mesh width of approximately 0.4 - 0.5 mm, but will pass through a screens having a mesh width of approximately 2.2— 2.7mm.

3. Medium Grade

Charcoal particle sizes from 2.3mm average diameter, to 6.5mm average diameter. This medium grade will be retained on a sieve screen having a mesh width of approximately 2.4— 2.7 mm, but will pass through a screen having a mesh width of approximately 5.5— 6.5 mm.

4. Coarse Grade

Charcoal particle sizes from 5mm average diameter to 12mm average diameter. This course grade will be retained on a sieve with a screen having a mesh width of approximately 5.5— 6.5 mm, but will pass through a screen having a mesh width of approximately 9.5 - 10.5 mm.

In particular there are two classes of charcoal that can be differentiated in this specification, charcoal powder and charcoal granules. Charcoal powder refers to the powder grade whereas the term "Charcoal granules" refers to charcoal of fine grade, medium grade or coarse grade or any ^~ combination thereof being used as one of the components in the plaster mix. Charcoal granules can also refer to any other charcoal grade larger than coarse grade if required by the particular application. Unless otherwise stated, the term charcoal granules is intended to refer to charcoal particles of fine grade, medium grade or coarse grade or any combination thereof.

The charcoal sizes above are indicated in average diameter value, which means charcoal granules and powder particles can take on any shape provided they filter through the appropriate sized sieve. It will be appreciated that future production methods of charcoal possibly utilizing wood chips or other organic material and continuous carbonation kilns may produce grades of charcoal of sufficient qualities that may not require additional milling, crashing, grading or sieving prior to inclusion in the plaster mix.

For a standard type board, any type of charcoal may be used, for example biochar crop waste or rice husk charcoal. For specialty boards with enhanced properties as described for decorative and high adsorption boards, wood charcoal is preferred.

Overview of board production

Plaster boards are generally produced on continuously operating belt processing lines, from plaster and additives for the gypsum core and from high-grade thick paper or cardboard as the outer covers. Referring to figures la, lb and 2, a typical method of forming a plaster board of the invention will now be described. As shown at step 1100 a plaster mix is first formed comprising the gypsum and the additives which comprise charcoal.

Figure 2 shows the steps 1110 to 1170 associated with forming the plaster mix (step 1100 of Figure 1). Figure lb shows a production line for gypsum plasterboard with charcoal as an additive. Both figures will be referred to in the following description with steps of figure 2 being referred to using the same reference numerals as corresponding steps in figure lb. In the production of plaster boards, first the gypsum is ground 1110 and rotary kilns 1115 are used to calcinate the raw gypsum rock 1120. Other additives are prepared and weighed 1130 ready to be added to a mixer such as a pin mixer 1135. Water is heated at step 1140 in conventional boilers or large commercial water heaters to produce hot water to mix with the dry calcinated gypsum. Charcoal is added to the plaster and water mixture at this point 1150, in a manner to described for various embodiments with reference to Figures 4 to 8. Other water reducers/bonding agents/additives already prepared are also added 1160 and the ingredients are all mixed together 1170 to form the plaster mix 1100. The ingredients can be mixed in any order suitable for the application. Due to the large difference in density between the charcoal particles and the plaster particles; there is a great tendency for the mixed ingredients to settle out even in dry form. For this reason it is preferable that the ingredients are weighed and added separately into the mixer at step 1170 (typically a pin mixer), just prior to placement or extruding on the moulding station 1175.

Other additives could be in the case of a fire-resistant rated wallboard, fibreglass fibres. For water resistant grades, other additives and special papers are used. There are also outdoor grades and special high-strength products that require other kinds of additives and papers, or even fibreglass panels.

As stated above the charcoal is preferably wood charcoal produced by carbonation of wood, but could also include various types of biochar. The charcoal used to form the plaster mix above can be in the form of charcoal powder or granules or both. Each form, when added to the mix, provides the board with different properties as will be described with reference to various embodiments described below.

Referring to Figure 3, a preferred method for forming different sizes of charcoal is shown. The charcoal is first ground in a suitable crushing or cutting mill 2100, producing typically charcoal particles of varying sizes. The particles of different diameters are then separated out according to the board specification requirements. To separate the powder particles from the charcoal granules (i.e. the larger granules), one or more screens or sieves (preferably vibrating screen sieves) having an appropriate mesh width of approximately 0.4 - 0.5mm can be used (step 2200). The screens will only allow the charcoal powder 2210 to filter through. Alternatively a blower type separator could be used at 2200 to separate and collect d e powder particles. The granules 2220 can also be separated into a number of grades at step 2300, for example (but not limited to) three grades; a fine grade 2305, a medium grade 2310 and a coarse grade 2315. Again, as will be apparent from the embodiments discussed further in the specification, each grade used provides the board with specific properties. Screens or sieves can be used to filter the coarser grades into the three grades. For the fine grade, one or more screens having a mesh width of approximately 2.2 - 2.7mm (and preferably 2.5mm) can be used producing charcoal particles sized from 0.5mm average diameter to 2.5mm average diameter. For the medium grade, one or more screens having a mesh width of approximately 5.5— 6.5 mm (and preferably 6mm) can be used, producing charcoal particles having a diameter of between approximately 2.3 mm to 6.5mm. For the coarse grade, one or more screens having a mesh width of 9.5— 10.5 mm (and preferably 10mm) can be used, producing particles having a diameter of between 5 - 12mm.

Referring back to figures la and lb, once or while the plaster mix is being formed at step 1100, as described with reference to figure 2, the paper or card that forms the visible side of the board is initially supplied from below. The paper or card is scored for shaping the edges 1180. At the same time paper or card is supplied from above, the plaster is extruded between the two sheets of paper or other cover material (step 1200), and it passes through a series of rollers and presses to form its shape (step 1300), i.e. plaster is extruded onto a moulding station 1175. Preferably small pin-holes are cut into the top-side of the paper at 1400 to allow water vapour to escape when the board is in the baking kiln 11 0. Without the small holes, the steam may blow the paper off the sheet and the bond between the plaster and paper would be lost. Note that the mixture is not necessarily extruded between two sheets of paper or cover material but this is the preferred embodiment. Alternatively, the mixture could be extruded onto a moulding station having a open mould base and a roller for instance. Other methods of moulding the mixture into the desired shape board can be employed and are not intended to be excluded by the invention.

In the preferred finished product 1600, the paper or other cover material that forms the visible side of the board may be on one or both sides of the board depending on the type of charcoal used (some embodiments can afford a fully exposed decorative surface as will be described further). The cover material used can be any one of paper, cardboard, breathable textile wallpaper or paper wallpaper or any other suitable textile made from organic and/or inorganic, natural or synthetic fibers such as fiberglass, cotton, wool felt, and/or any other sheet material: wood veneer, plastic, acrylic, polyurethane, resin, metal foil and/or a suitable membrane such as latex or paint, and/or any other and/ or combination of and/ or perforated version/ s of the cover material/s.

A possible variation of plaster board to that described above has two kinds of plaster. This is termed "dual plaster board". Along the edges of the sheet, pure gypsum plaster is extruded between the paper or card. In the middle of the sheet, an air entrainment additive, usually some kind of foaming agent, is used (such as sodium lauryl sulphate) in combination with the gypsum plaster. The air entrainment makes the gypsum lighter without significant degradation to its strength. Air entrainment and boards having an edge mix will be described in more detail in their respective sections further below.

Once this is done, the board is ready for setting and baking. Plaster board lines are very long, because it takes some minutes for the chemical reaction in the gypsum plaster to harden the mixture sufficiendy for the board to be cut and transferred into the bake oven 190 for drying. It may take four to six minutes for the board to stiffen, if the production line speed is 70 meters per . minute or more, there is a need for a very long line.

The baking is preferably done in a special kiln 1190 with many decks (step 1500). Long sheets of board are stacked into the kiln 1190, each having to stay inside for the required reside time to remove excess water. The high temperature also speeds the chemical reaction that hardens the board. Too much heat cannot be applied too quickly because the chemical reaction will not occur correctly and the required strength will not be achieved. It is therefore preferable that baking is carried out using the correct temperature profile. The invention is not intended to be limited in scope to a specific temperature or temperature profile for mixing, curing and baking the plaster boards/mixtures and any temperature/s for achieving the desired plaster boards/mixtures can be used in the manufacture process.

Types of boards produced

The above describes a broad method of forming a gypsum plaster and charcoal based board. The following is a list of nine different types of charcoal plaster boards which have been produced for testing. Two boards (1 and 2) are of solely charcoal powder type, two (3 and 4) are of solely charcoal granule type and five others (5-9) are a mixture of the two types of charcoal sizes.

1. Carbon powder board

2. Carbon powder board with air entrainment and/ or porous carbon board

3. Charcoal granule board - · ^'

4. Course grade carbon board -

5. Mixed grade carbon board

6. Graded carbon board

7. Dual density impact carbon board

8. Dual density decorative carbon board (exposed surface)

9. Absorptive carbon board (coarse with carbon powder, air entrainment and exposed surface) ,

Each of the above boards can be produced using the general method described with reference to figures 1 to 3, with the constituent components combined in quantities as described in the "recipes" below.

The recipes and any associated modified methods of forming the boards will now be described for each of these boards. The invention is not intended to be limited to an of these recipes. Similar mixtures producing the same or similar results are intended to be covered by the scope of the invention.

Charcoal density varies depending on source material and pyrolysis method and temperature. The recipes below are intended for a wood charcoal with approximately 3.2 times the volume as the gypsum plaster of the same weight. The board preparation recipes given below are dry mass based and the added water is mass based.

For simplicity the proportions of ingredients are given in parts (or proportions). For example: 2 parts plaster : 1 part charcoal : 1.5 parts water @ 40°C

Could be made up to:

Gypsum plaster (gypsum plaster) 400Kg

Graded Charcoal lmm— 6mm 200Kg

Potable Water @ 40°C 300Kg

It will be appreciated that any actual quantities of constituent components (ingredients) could be used, in the correct proportions. It will be appreciated that the proportions do not have to be exact. Rather, the proportions shown are indicative and in each case one preferred option. The proportions could vary however the following are preferred embodiments of the invention.

It will be appreciated that additional additives would be added as is normal in the art of commercial plaster board production, such as water reducers. These additives may have the effect of changing the proportions of ingredients in the recipe and changing mixing or extruding methods and properties of the resultant board.

The water temperature has an effect on the set rate of the mixture; a higher temperature can speed the set rate, and makes drying of the board faster. In commercial production the temperatures would vary to suit the speed of the production line and the ambient temperature of the other components. The invention is not intended to be limited to a specific water temperature and the temperature used in the experiments below is only exemplary.

Carbon Powder Type Boards

Two types of boards with mainly powder grade charcoal were produced and tested. The addition of charcoal powder in the plaster board mixtures gives the board any one or more of the following characteristics: improved thermal insulation, improved air purification, improved humidity absorption and release, improved removal of odours, adsorption of volatile organic compounds, shielding attenuation, noise reducing properties, strength, and impact resistance whilst not compromising fire resistance. Using dry charcoal powder (preferably under 0.1 mm 0, but containing particles up to 0.5mm 0) of either relatively low or relatively high density charcoal or both eliminates floating in the carbon plaster mix. Charcoal powder is also easy to include in the mix with no problems in using existing plaster board manufacturing equipment with just minor modifications needed to make carbon powder plasterboard. The powder generally makes a darker mixture. Air entrainment and creating a foam work well in a charcoal powder mix, even with high levels of charcoal inclusion. These properties of charcoal powder make it desirable to use in most applications of carbon plaster boards.

The applicant has discovered that charcoal powder adheres to gypsum plaster exceedingly well, giving improved characteristics in all aspects of board performance

Using charcoal powder increases the porosity of the plaster board. This presents the benefit of improved gaseous exchange permitting the properties of charcoal to be realised, in particular in odour absorption (see test 1 at the end of this specification) and absorption of harmful organic chemicals such as formaldehyde emitted from building materials (see test 3) and acetaldehyde contained in cigarette smoke (see test 2). The charcoal powder board has excellent humidity conditioning performance permitting passive humidity control in buildings utilising these boards. In humid conditions the charcoal within the board absorbs moisture from the atmosphere, then in dry conditions the water is re-released into the atmosphere (see test 4).

To enhance the gaseous exchange between the atmosphere and the charcoal within the board it is possible to make a porous carbon plaster. The porous carbon plaster board is formed using a foaming agent mix that forms porous walls that run together as the board is extruded in the moulding station and that collapse during curing. This porous carbon plaster board may also be formed using gas injection techniques together will low rates of foaming agents. The result is a breathable plaster (see foaming agents section below).

1. Carbon Powder Board

Ingredient Gypsum plaster Charcoal Powder Water @ 40'C

Proportion 1.5 - 2.5 0.01 - 1.5 0.6 - 2

Preferred 1.0 0.5 - 1.5 (more 1.0

preferably 0.5) The plaster and the board are formed using the method outlined in figures 2 and 1 respectively (and as described in detail above). The water is added at step 1140 and the charcoal powder at 150, and mixed in a standard manner at step 1170 of figure 1.

The above recipe results in a plaster board with improved thermal insulation, shielding attenuation, noise reducing properties, strength, impact resistance and that does not compromising fire resistance (see tests 5, 6, and 7 at me end of this specification).

2. Carbon powder plasterboard with air entrainment

Ingredient Gypsum Charcoal Foaming Water @ 40

plaster Powder Agent

Proportion 1.5 - 2.5 0.01 - 1.5 0.0001 - 0.06 0.6 - 2

Preferred 1.0 0.5— 1.5 (more 0.001 1.0

preferably 0.5)

The charcoal powder in this mixture is mixed with gypsum plaster and a foaming additive (i.e. foaming additive added at step 1160 of fig. 2). The ingredients are mixed at step 1170 in a beater type or high shear mixer to produce air entrapped plaster for light weight boards with good thermal insulating properties (see test 6).

The added foaming agent is preferably (and typically) Sodium lauryl sulphate. All ingredients (plaster, charcoal powder, foaming agents and water) are preferably mixed in an air entrainment mixer to form this specific plaster mix. An air entrainment mixer is preferably a high shear type or beater type mixer, but may also include mixers that incorporate compressed gas injection and other types of mixtures that have the capability of forming air bubbles within the plaster mixture.

The board of this embodiment will have similar weight and strength characteristics as conventional plaster boards but added thermal insulating properties. When air entrainment is desired mostly charcoal powder and fine granules of charcoal are preferred. Larger particles of charcoal reduce the air entrainment ability and fineness of air bubbles. Air entrainment makes the plaster lighter without significant degradation to its strength.

The porous air entrainment method is preferred however other methods may be used as outlined in the Air Entrainment' section further below. This board can be produced using a single plaster mix as outlined by the method of figure 1 (and as described in detail above), or it can be formed with a separate edge mix which is not air entrained as will be described in more detail in the 'Edge Mix' section below.

Note that in this specification a foaming agent means a chemical compound which facilitates the formation of foam or helps foam maintain its integrity by strengthening individual foam bubbles, or enhancing foam mixtures colloidal stability by inhibiting the coalescence of bubbles. Foaming agents are used in plaster board manufacture to facilitate air entrainment in the gypsum core mix giving a lighter weight board which is cheaper to produce and easier to handle.

A broad spectrum of chemicals can act as foaming agents. In all cases, they act as surfactants, reducing surface tension like detergents, or soaps. Foarning agents that can be used are of the low sudsing type soaps, (some high sudsing types interfere with the gypsum setting reaction), or pre blended soap mixtures of one or more soaps. Examples of foaming agents that can be used by the present invention include: sodium lauryl sulfate, sodium lauryl ether sulfate, alpha-olefin sulfonates, alkali, ammonium or emanolamine salts of sulfuric esters of hydroxyalkylated alcohols or hydroxyalkylated alkyl phenols, various salts of alkyl ethoxy sulfates.

The composition of the foaming agent can have an impact on the integrity of foam. Some foams tend to be very stiff and firm, with bubbles which have extremely strong walls. Others are softer, running together and collapsing over time. Different properties can be brought out with the selection of an appropriate foaming agent or mixture of agents. In one embodiment a more porous plaster board can be formed using a foaming agent mix with softer bubble walls that run together as the board is extruded in the moulding station and collapse during curing. This enhances the absorptive properties of the charcoal within the board. This porous plaster may also be formed using gas injection techniques together will low rates of foaming agents.

Charcoal Granule Type Boards

The addition of charcoal granules in the plaster board mixtures gives the boards any one or more of the following characteristics: improved thermal insulation, improved humidity absorption and release, improved air purification, odour removal properties, adsorption of volatile organic compounds, shielding attenuation, noise reducing properties, emission of far-infrared rays and anions, strength, impact resistance, and light weight whilst not compromising fire resistance. The level of improved insulation, shielding attenuation and noise reducing ability is proportional to the amount of charcoal in the mix.

The level of improved humidity absorption and release, removal of odours, and/ or adsorption of volatile organic compounds, and impact resistance is increased if higher concentrations of charcoal are added near the facing surface. In some embodiments the facing surface is shaved, ground or perforated to increase emission of far-infrared rays and anions. Perforation includes punching, moulding or drilling holes, as in acoustic and/ or ceiling boards.

The medium grade or a combination of charcoal grades can be mixed with plaster to produce high impact resistance, and sound proofing boards (see test 5 and 7).

The coarse grade or a combination of charcoal grades can be used to make high adsorption, decorative and dual density boards which are both surface impact resistant and thermally insulating and reasonably light weight. The surface of these boards can be shaved or cut to produce a decorative black and white, high absorbing board typically for ceilings (see tests 1—7).

3. Carbon Granule board

Ingredient Gypsum plaster Charcoal Granules - Fine, Water @ 40° C

Medium and Course grades

0.5 - 12mm 0

Proportion 1.5 - 2.5 0.01 - 1.5 0.5 - 1.5

Preferred 2.0 0.5— 1.5 (more preferably 1.0) 1.0

This recipe uses charcoal granules which are preferably 0.5— 6mm in diameter but can include coarse granules as well. Fine, medium and course grade granules can be gathered at 2305, 2310 and 2315 using the process shown in figure 3 for example. The plaster mix and the board are formed using the processes shown in figures 2 and 1 respectively. This recipe can produce a slighdy lighter weight board without using air entrainment (although air entrainment could still be used), giving impact and fire resistance. The weight of the board depends on the quantity and density of the charcoal used. The carbon granule board also possesses good acoustic reduction properties for soundproofing. Lower water content can be achieved with this mixture which speeds up the drying process and reduces the energy required for production, thus reducing cost.

4. Coarse grade carbon board

Ingredient Gypsum plaster Charcoal Granules Water @ 40°C

5 - 12mm 0

Proportion 1.0 - 2.5 0.01 - 1-.5 0.5 - 1.5

Preferred 1.3 - 2.0 0.5 - 1.5 (more 0.8 - 1.0

preferably 1.0)

This recipe uses coarse grade charcoal granules which are preferably 5— 12mm in diameter. These can be gathered at 2315 using the process shown in figure 3. The plaster mix and the board are formed using the processes shown in figures 2 and 1 respectively. This recipe can produce a slightly lighter weight board without using air entrainment, giving excellent impact resistance, improved diermal insulation, humidity absorption and release, and air purification. The weight of the board depends on the density of the charcoal used. The graded carbon board also possesses some acoustic reduction properties for soundproofing.

It will be appreciated that air entrainment could be incorporated with air injection or pre manufactured foam entrainment methods or any other method as described in the 'Air Entrainment' section below.

In production of this type of board, one of the main problems is the lower density charcoal floating in the plaster mix. It is therefore preferred that a method of preventing floating such as hydration or any other method discussed under the 'Preventing Floating' section below is used during production.

In one embodiment floating is reduced by lowering the water content which speeds up the drying process and reduces the energy required for drying.

As will be described in more detail further below, this board can also be shaved or cut to produce a decorative surface. At higher rates of charcoal inclusion it is difficult to achieve a smooth surface, but could still be used as a decorative or acoustic board. Chatcoal Powder + Charcoal Granule Type Boards

In several other embodiments, charcoal powder and charcoal granules can both be included in the mixture to benefit from both selections of properties mentioned above.

5. Mixed grade carbon board with air entrainment

Ingredient Gypsum Charcoal Charcoal Water @

plaster Powder Granules 40°C

Proportion 1.5 - 2.5 0.01 - 0.75 0.01 - 0.75 0.6 - 1.25

Preferred 2.0 0.25-0.75 (more 0.25-0.75 (more 0.9

preferably 0.25) preferably 0.25)

In production of this particular board the mixing process discussed above with reference to figure 2 is slightly modified. Before the charcoal is added at step 1150 the charcoal is first separated into powder and granules using sieves or blowers as discussed above with reference to figure 3 (i.e. resulting in powder 2210 and granules 2220). The mixing is carried out in two stages. At step 1150 of figure 2, the charcoal powder is added and at step 1170 the plaster, the powder and the foaming agents are all mixed in an air entrainment mixer. Referring now to figure 4, the process of figure 2 is then extended. The above mixture is then passed into a second mixer at step 1175 where the charcoal granules are mixed just prior to formation (1100) and extrusion of the plaster at 1200.

The above air entrainment method is preferred however other methods may be used as outlined in the 'Air Entrainment' section further below.

This board can be formed from a single plaster mix or it can be formed with a separate edge mix as will be described in more detail in the 'Edge Mix' section further below. 6. Graded carbon board

Ingredient Gypsum plaster Any combination of: Charcoal - Water @ 40°C

Powder and Charcoal Granules

- Fine, Medium and Course

grades

0 - 12mm 0

Proportion 1.5 - 2.5 ^: 0.01 - 1.5 ^' 0.5 - 1.5 ^~~

Preferred 2 ^~~ 0.5 - 1.5 (more preferably 1.0) θ

This recipe can use any combination and any proportion of charcoal powder and/or granules of any grades and can include only one type or both of charcoal powder and granules. Charcoal powder and fine, medium and coarse granules can be gathered at 2210 and at 2305/2310/2315 respectively using the process shown in figure 3. The plaster mix and the board are formed using the processes shown in figures 2 and 1 respectively. This recipe can produce a slightly lighter weight board without using air entrainment, giving impact and fire resistance. The weight of the board depends on the density of the charcoal used. The graded carbon board also possesses some acoustic reduction properties for soundproofing (see test 7).

Air entrainment can still be used in alternative embodiments as outlined in the 'Air Entrainment' section below.

Lower water content can be achieved with this mixture which speeds up the drying process and reduces the energy required for production, thus reducing cost.

Dual density impact carbon board

Facing Layer Gypsum plaster Medium and/ or Water @ 4(TC

Ingredients Course Charcoal

Granules

2.3 - 6.5mm 0

- 5 - 12mm 0

Proportion 2.5 - 3.5 0.01 - 1.5 0.5 - 1.5

Preferred 3.0 0.5 - 1.5 (more 1.0

preferably 1.0)

Backing Layer Gypsum plaster Charcoal Powder Water @ 40°C

Ingredients

Proportion 1.5 - 2.5 0.01 - 1.5 1 - 2

Preferred 2.0 0.5 - 1.5 (more 1.5

preferably 1.0)

A high performance board can be produced by adding two different kinds of plaster mix to the main body. These are distributed in the correct location and evenly using moulding stations. As shown in figure 5, step 1200 of the process described with reference to figure 1 is broken up into several steps. A plaster mix facing layer containing the charcoal granules is first spread onto the sheet of cover material (paper or card for example) that forms the visible side of the board (facing side) at step 1220. At 1230, the mix containing charcoal powder and preferably an air entrainment agent (as described above for 2) is extruded on top of the facing layer and optionally along with the backing sheet of cover material (paper or card for example).

The advantage of this type of laminated style board is that it can produce a hard impact resistant surface. It also provides a high concentration of charcoal chips at the surface, which can be exposed by shaving, grinding or perforating the surface to enhance the properties of charcoal within the board, and produce a decorative effect (discussed in more detail for 8 below). The backing side includes powdered charcoal and air entrainment to make the board lighter in weight and more thermally insulating. The backing side may also include some fine grade granules. The facing mixture does not need to be limited to just using coarse charcoal (charcoal granules) mixed with gypsum plaster, it may contain charcoal powder, air entrainment or other additives to modify the properties of the board.

In production of this type of board, one possible problem is the lower density charcoal floating in the plaster mix. It is therefore preferred that a method of preventing floating such as hydration or any other method discussed . under the 'Preventing Floating' section below is used during production.

This board can be produced using a single plaster mix or it can be formed with a separate edge mix as will be described in more detail in the 'Edge Mix' section further below.

8. Dual density decorative carbon board (exposed surface)

Facing Layer Gypsum plaster Charcoal Granules Water @ 40°C

Ingredients 5 - 12mm 0

Proportion 2.5 - 3.5 0.1 - 1.5 0.5 - 1.5

Preferred 3.0 0.5 - 1.5 (more 1.0 - preferably 1.0)

Backing Layer Gypsum plaster Charcoal Powder Water @ 40°C

Ingredients

Proportion 1.5 - 2.5 0.01 - 1.5 1 - 2

Preferred 2.0 0.5 — 1.5 (more 1.5

preferably 1.0)

This board is similar to the dual density impact board described in 6 above, except that the facing layer is exposed rather than covered by a paper, card or textile finishing surface. The exposed face can be left natural or finished with some form of coating applied, typically, but not limited to paint. The exposed surface can also be shaved or ground or perforated to expose the charcoal giving differing decorative effect depending on the composition of the mix, and possible addition of pigments. Plain gypsum 300 and charcoal lumps 310 give a nice black and white mosaic pattern as shown in Figure 8. The ground surface can be left natural or finished with some form of coating depending on the properties desired in the finished product.

In production of these exposed surface boards, a sheet of cover material is still required for the facing surface of the facing layer to make the board. The facing cover material can then be removed to eliminate excessive waste. A plastic sheet or fine grade paper can be used for example and these could be removed just after the board had initially set. In commercial production, a special facing conveyer belt is used in the moulding and extruding station which extends to the setting section of the production line. Once the gypsum charcoal mixture has set sufficiendy the belt would be peeled off and returned to the moulding station as a continuous belt. As it is returned the belt would be cleaned and a non stick releasing compound applied, such as graphite or silicone. It may however be found that a belt with a Teflon surface may not require a releasing compound.

This process enables coarse charcoal chips to be used to make decorative boards with high absorptive characteristics, and can also be used to solve the difficulty of producing a smooth surface in recipe 4, without the need to hydrate the charcoal.

It will be appreciated that air entrainment could be incorporated in either the facing layer or backing layer or both possibly using different air entrainment methods (such as compressed air injection or pre manufactured foam entrainment methods ) as described in the 'Air entrainment' section below.

This board can be produced using a separate edge mix as will be described in more detail in the 'Edge Mix' section further below. 9. Absorptive carbon board (coarse with carbon powder, air entrainment and exposed surface)

Ingredient Gypsum plaster Charcoal Charcoal Water @

Powder Granules 40°C

Proportion 1.5 - 2.5 0.5 - 0.9 0.1 - 0,5 1 - 1.5

Preferred 2.0 0.7 0.3 1.25

The method of production of this board similar to that described for the mixed grade carbon board in 5.

The facing surface of this board can be finished in several ways, either using a porous paper or textile or other material, or alternatively a skinless cover material produced using a removable film or belt in the moulding station and setting area of the production line (as described above in 8). This facing surface is then shaved after the board has set sufficiently, to expose the charcoal granules. The facing surface outer layer can be removed by using a rotary or oscillating cutter or shaver once the board is set but still wet. Alternatively, once the board is dried it can be cut or shaved, but grinding would also be possible with the use of dust extracting equipment. In yet another alternative, the surface could be perforated (by drilling or punching) or moulding a decorative pattern in the surface to better expose the charcoal and to improve the acoustic properties of the board.

Alternatively, the board can be made twice as thick as the desired final board (plus preferably the thickness of the saw) and then cut in half through the flat plain of the board. This would produce two boards, each with one exposed and cut surface. It will be appreciated that the board can be made of any thickness and cut into any number of boards having similar or varying thicknesses to expose one or more cut surfaces on each board.

This board can be produced using a single plaster mix or it can be formed with a separate edge mix as will be described in more detail in the 'Edge Mix' section urther below.

In production of this type of board, one of the main problems is the lower density charcoal floating in the plaster mix. It is therefore preferred that a method of preventing floating such as hydration or any other method discussed under the 'Preventing Floating' section below is used during production. In any of the boards above that contain charcoal powder, fine grade charcoal granules may also be used in combination with the charcoal powder.

Preventing Floating

In production of charcoal granule type boards and in particular medium or coarse grade charcoal boards, one of the main problems is the lower density charcoal floating in the plaster mix. Newly produced charcoal has very little water content, however over time rain or atmospheric moisture is naturally absorbed into charcoal increasing the moisture content to usually about 5%. This gives medium density charcoal a segregated mass of approximately 300g per litre (solid mass of around 600g per litre). Dry powder gypsum plaster has a higher density of around 880g ~1200g/L, with density becoming higher once it is mixed with water meaning the lower density charcoal, and in particular the larger charcoal particles, tend to float in the plaster board mixture.

Four possible techniques for rriinimising or eliminating the effect of floating are:

1. Using charcoal powder. The small sized particles distribute the charcoal finely and somewhat evenly throughout the mixture to minimise floating. The smaller the size of the particles, the better the end result in terms of floating minimisation. The charcoal size however does also depend on the particular application.

2. In the embodiments using medium and coarse charcoal, the charcoal can be hydrated to increase the specific mass of the charcoal and thereby reducing the effects of floating.

3. A high density charcoal can be used such as white charcoal as described above on page 9.

High density charcoal has a higher specific mass of around 750g ~1000g/L thereby reducing the effects of floating.

4. Limiting the water content of the mixture will produce a relatively stiff mix. This also minimises floating. This is a mechanical method of reducing floating due to the excessive stiffness of the mix. This method however can make placement of the mixture difficult, but does reduce the drying time in the bake oven dryer.

5. Foaming the plaster slurry to reduce its density. Slurry densities can vary from lOOOg/L ~2000g/L, the lighter densities being achieved with air/gas inclusion in the form of tiny bubbles in the slurry mix.

Embodiments of this invention can use any combination of methods as described above to minimise or eliminate the effects of floating as desired by the application and the invention is not intended to be limited to any one method. Other methods also evident to those skilled in the art may also be used to minimise floating and the scope of the invention is not intended to exclude such methods.

In one embodiment, hydration of the charcoal, and in particular coarse charcoal granules, is used to minimise or eliminate the floating effect if observed.

Preferably to overcome the floating effect of charcoal the charcoal granules are hydrated in water for a substantial period prior to being mixed in with the plaster (i.e. prior to step 1150 in figure 2), allowing the charcoal to absorb a large quantity of water to greatly increase mass and minimize the floating effect. With some hydration methods charcoal will actually attain similar mass to water eliminating the floating effect of charcoal in water and effectively in the plaster mix. It is noted however that using this method of charcoal preparation will extend the drying time of the plaster board, and may even require a different drying method, such as fillet stacking the finished boards, so they can continue drying while in storage, transport and generally for the period prior to end use. They may still continue to dry while in the final application until they reach relative humidity level of the final location. -

Some of the advantages of hydration are:

a) Reduction of the floating effect which gives a more even distribution of the charcoal in the mix and allows surface finishing as described above. Hydrating the charcoal effectively waterlogs the charcoal increasing its density and minimising the floating effect to an acceptable amount. b) Hydration of charcoal powder can be useful to prevent dust inhalation while mixing.

The method of hydration can be used on any of the carbon boards above which utilise charcoal granules (mainly medium and/or coarse grade granules).

Hydrating the charcoal effectively waterlogs the charcoal increasing its density and minimising the floating effect to a negligible amount. Several methods can be employed to hydrate the charcoal: a). Soaking the charcoal in water for a period before placing in the plaster mix. Smaller granules generally do not require as long a soak period as relatively larger granules. Larger lumps of charcoal may require several months to substantially hydrate for example. In one of the experiments conducted it took a lump of hard medium/low density charcoal of dimensions 50mm x 50mm x 98mm five months to fully hydrate and increase in mass and volume by 145% and 0.2% respectively b) . Soaking the charcoal in water with an added surfactant or some type of soap or wetting agent to the water speeds the soaking process. The soaking process may be aided with the addition of a surfactant or some type of non sudsing soap or wetting agent, such as used in a washing machine or dishwasher or such as used in air entrainment. If air entrainment is not desired in the plaster mix, the charcoal is rinsed after hydration and prior to use in the mix removing excess surfactant from the charcoal surface.

c) . Soaking the charcoal in water with a raised temperature, even up to boiling point. Boiling greatly speeds the hydration process, this can be done in conjunction with soaking to achieve higher hydration rates within a given time period. Boiling may be done either at the start of the soaking period or anytime during or after the soaking period. Typically for lump grade medium density charcoal, 80% hydration can be achieved within 1 to 4 weeks.

d) . Vacuum and pressurized forcing/treating method. This method consists of placing the charcoal in a pressure chamber, removing or sucking out the air inside the chamber using a vacuum pump and then applying water under pressure to the chamber to replace the air void and hydrate the charcoal. This method quickly fills the empty pore spaces of the charcoal with water. This vacuum and pressurized forcing method is faster for all charcoal types and sizes and is the preferred method for larger commercial scale production applications.

Figure 6 shows a process that may be used to prevent floating of charcoal granules in a plaster mix. At step 1155 the charcoal is hydrated as described above. The hydrated granules are then mixed with a minimum of plaster mix (step 1221) (i.e. just enough to produce a smooth facing surface) and the charcoal is left to setde within the mix before the rest of the plaster is added. The amount of plaster used initially to mix with the hydrated charcoal varies depending on the design of moulding station and also depending on the size and quantity of charcoal used. The amount of plaster needed is preferably between 25% and 50% of the total amount of plaster used. However, as will be appreciated, for lower quantities and smaller size granules, less plaster can be used.

The rest of the process is a modified series of steps for extruding the mix in between the sheet (step 1200 in figure 1 and steps 1220 and 1230 in figure 5). After the charcoal granules have been mixed with the minimum amount of plaster (step 1221), if necessary the moulding station is vibrated (step 1222) which helps settle the charcoal chips and aids in producing a good surface with lower water content in the mix. This is allowed to partially set, prior to the rest of the plaster being added. In the case of the dual density boards the second layer of plaster and carbon mix is added at this point and placed together with the backing paper (step 1230 of figures 5 and 6). Prior to placement of the rest of the plaster or of the second layer, if necessary, the half formed board can pass through a roller (step 1223 of figure 6), which would push down any charcoal chips that have floated too high, and relocate them near the facing cover material (if used), or the surface that will be exposed. This facing layer containing the coarse chips can have a set accelerator such as potassium sulphate or Terra Alba ground gypsum added to speed the initial set (this will enable the production line to move faster and/or have a shorter first moulding station). For boards 7 and 8, along the production line at a second moulding station, the second layer of plaster and powdered (or fine) charcoal mix can be added to finish and smooth the backing layer of the board together with the backing cover material (step 1230).

The process described above enables coarse charcoal chips to be used to make decorative boards with h gh absorptive characteristics, and can also be used to solve the difficulty of producing a smooth surface in recipe 3.

It will be appreciated that any one of the above methods may be used to hydrate the charcoal and the most efficient method may differ depending on size and density of the charcoal. The scope of the invention is not intended to be limited to the method by which the charcoal is hydrated and is more concerned with the benefits hydrated charcoal presents in plasterboard production.

Hydration is not essential and in some cases the method for preventing floating can be carried out without step 1155.

Exposed surface decorative boards

For the exposed surface boards described above (mainly 8 and 9) it is possible to make different coloured boards by mixing a coloured additive with the plaster mix in the facing layer. Two materials suitable to colour the mix are: dry powder metallic oxides, usually used as additives for colouring Portland cement and predispersed pigments for colouring latex paints.

Furthermore tumbling the charcoal chips can prepare a round or oval shaped chip to give a river stone appearance to the finished board. The chips can be tumbled either just together with other charcoal; or alternatively some small abrasive balls or other harder substance can be added in a ball mill style of tumbler. Alternatively wet tumbling can be used when hydrated charcoal is desired.

The exposed face can be coated with a protective paint type coating or permeable paint like material or emulsion, or have a permeable paper of fabric glued to the surface. Alternatively or in addition the exposed surface can be perforated. Aif Entrainment

For any of the boards above, the methods described for air entrainment are the preferred methods but the scope of this invention is not intended to be limited to such methods.

Air entrainment has many desirable features and can be achieved using a variety of methods:

1. The charcoal powder grade can be mixed with gypsum plaster and a foaming additive, mixed in a beater type mixer to produce air entrapped plaster for light weight boards with good thermal insulating properties. This mixture can also be used as the backing mixture of the high absorbing boards (dual density boards).

2. Air entrainment can be produced using compressed air injection together or in addition with a foaming agent, charcoal powder or a mixed grade of charcoal can be used using this system of air entrainment. In this method gypsum plaster, the charcoal, a foaming agent and the water are mixed in a mixer to form a slurry, and then compressed gas is added to the slurry to create air entrainment.

3. Air entrainment can be produced using pre-formed foam, or a foam and water blend, can be mixed with the plaster, charcoal, additive and water composition, either replacing some or all of the water content. This can occur firsdy together in the mixer, or alternatively secondly, if a second low shear mixer is used to blend in the foam, producing a higher volume of air entrainment. Charcoal powder or a mixed grade of charcoal can be used using this system of air entrainment.

Any of the above methods or any other suitable method known in the art may be used to provide any of the boards of this invention with air entrainment.

Additives

In some embodiments of the charcoal plasterboard additives are added to the gypsum slurry that forms the core of the board that is sandwiched between two sheets of heavy paper or other cover sheet material. Additives can include: an additive to assist in forming larger foam core bubbles, starches (to help adherence to the paper sheet covers), polycarboxylate ether dispersants, naphthalene sulfonate, fibers (typically paper and / or fiberglass, plasticizer, finely ground gypsum crystal as an accelerator, EDTA, starch or other chelate as a retarder, various additives that may increase mildew and/ or fire resistance (fiberglass or vermiculite), wax emulsion or silanes (for lower water absorption) and water.

Edge Mix

In the embodiments above (especially those having air entrainment properties), the boards are preferably formed from two different kinds of plaster mix. As shown in figure 10 along the edges of the sheet (4 and 5), pure gypsum plaster 1 with charcoal powder or fine granules is extruded between the paper (or other textile material) and in the middle of the sheet the plasterboard recipe outlined in the embodiment is used. The recipe will preferably contain an air entrainment additive (generally some kind of soap), typically sodium lauryl sulphate/ Liquid glycerine is also preferably used to assist the foaming agent as stated above for the air entrainment boards.

The beginning of the process shown in figure 1 can therefore be modified such that two forms of plaster are used to form the board. Referring to figure 7, two forms of plaster are formed at steps 1100a and 1100b respectively. Pure gypsum plaster with charcoal powder is formed at 1100a and a plaster mix of a specific recipe (preferably with air entrainment additive) is formed at 1100b. The edge mix is first extruded along the edges and between the sheet layers at 1200a, followed by the specific plasterboard mix at 1200b. The process of extrusion of the specific plasterboard mix and the rest of the process for forming the board will be as outlined above for each of the specific plasterboard recipes. The specific plasterboard mix can be for example: the air entrainment mix of board 2, either one of the mixed grade mixes of boards 5 or 9 or as shown in figure 10 either one of the dual density mixes of boards 7 and 8 having a facing layer 12 with charcoal granules 3b and a backing layer 13 with charcoal powder 3a mixed.

Note figure 10 shows a dual density mixed board having an edge mix. The middle layers 12 and 13 can alternatively be a single layer of plaster mix as defined for the rest of the boards above.

Carbon Neutral and offset calculation

Plaster board manufacture produces large amounts of green house gases in its production, mainly C0₂. Carbon plaster boards offset the carbon emissions produced by plaster board production and in some compositions can be made to be carbon neutral in terms of C0₂ emissions. When high density charcoal is used, greater amounts of carbon can be incorporated. The resulting high carbon concrete can sequester greater amounts of C0₂ than that taken to produce it. Carbon dioxide is the most common green house gas, to remove it from the atmosphere it can be converted into a solid form of carbon using plants to form biomass which is then pyrolysed into charcoal. The calculation of how much C02 is stored in charcoal is as follows:

Carbon dioxides molecular formula is C02 with an atomic mass of 44g/mol.

Oxygen, O, has an atomic mass of 16g/ mol.

Carbon, C, an atomic mass of 12g/ mol.

44÷ 2 = 3.666

Therefore for every one tonne of carbon, 3.67 tonne ofiC02 have been captured.

Charcoal is typically between 85% and 98% carbon, with the remainder consisting of volatile chemicals and ash. If we take an average figure of 91.5% carbon content of charcoal; 1 tonne of kiln dry charcoal represents the equivalent of (3.67 x 91.5%) = 3.36 tonnes of C02.

Charcoal does absorb moisture from the atmosphere and if it is not stored or transported under cover it can have moisture added by rain. Generally most commercially available charcoal has a moisture content of 3.5 to 5%, however it can be as high as 10%. This should be taken into account when calculating the amount of charcoal required for the desired offset effect.

The invention therefore provides a method of sequestering carbon for a long period of time.

Variations

The above recipes are typical mixtures, however smaller proportion of charcoal powder can be used to make a cheaper board. If a higher proportion of charcoal is used the charcoals properties within the board will increase and the board will sequester more carbon. However, higher proportions of charcoal may create production difficulties in maintaining good surface quality and board strength.

The boards above are made using thick paper card as facing and backing cover materials, however a variety of papers or textiles could be used, depending on the final application of the board. For example a porous paper could be used on the absorptive board rather than shaving the surface.

The temperature of water mixed with plaster affects the set time of the plaster and may also contribute to faster drying times along the production line and in the bake oven. Gypsum has a maximum solubility between die temperatures of 22 °C and 37 °C, preferably the mix temperature is therefore kept within this range. Having the plaster mix at around 37 °C gives the fastest set time, so adding slightly higher temperature water at say at 40 °C (as in the boards above) or higher compensates for a lower temperature of the other ingredients (water temperature is adjusted depending on the ambient temperature of the other ingredients) to give a mix of around 37 °C. Other temperatures may therefore produce good plaster boards, and may also be used in a commercial operation. The invention is therefore not intended to be limited to any of the above specified temperatures.

Certification Regime

This invention also relates to a proposed new Certification and validation regime to monitor carbon inclusion in building products for use to certify and register for carbon offsets or credits along with compliance with building codes of practice.

Utilising charcoal in large amounts in plaster board and other building products is a new concept, it could therefore require a new certification regime to verify suitability as a structural component of buildings in terms of strength, porosity and moisture stability, and suitability of use. This certification scheme would also allow for systems and procedures that can be used to certify and verify carbon inclusion that can be registered for carbon offsets or credits under the CDM (Clean Development Mechanism) of the Kyoto protocol and United Nations Framework Convention on Climate Change (UNFCCC).

One possible form of the certification regime would be to issue a certificate of compliance that can be issued to users (customers) of carbon plaster board.

The certificate will detail the weight of carbon used in the mix and a test certificate that the mix meets recognised mix criteria and fulfils the strength and permeability tests if necessary.

Because the test details the weight of carbon utilised and sequestered then this certification program can be a registered project in the CDM, then carbon credits can be issued. Record of carbon used will be available to the manufacturing company to receive the carbon credits. This gives the manufacturing companies an incentive to sell the carbon based product. Experimental Boards and Tests

Dual density impact carbon board

Firstly samples of this board were prepared to be used in the experiments below. The test board was made 12.5mm in thickness using medium density "black type" charcoal made from hardwood, Indonesia. Charcoal Density was 0.59g/ml.

Facing Layer Gypsum plaster Charcoal Granules Water @ 40° C

Ingredients 5 - 12mm 0 [no dispersant or

Coarse Grade superplasticizer was

used]

Proportion 3.0 1.0 1.5

Weight Used 3.0kg 1.0kg 1.5

Backing Layer' Gypsum plaster Charcoal Powder Water Foam

Ingredients @ 40°C Agent

sodium

lauryl

sulphate

Proportion 3.0 1.0 1.3 0.01

Weight Used 3.0kg 0.1kg 1.3kg 0.01

A plaster mix facing layer containing the charcoal granules is first spread onto the sheet of cover material (white paper) that forms the visible side of the board (facing side) at step 1220. At 1230, the mix containing charcoal powder and an air entrainment agent (sodium lauryl sulphate) is mixed with a large electric cake mixer at high speed with two whisk attachments each with four blades, this foamed mix is extruded on top of the facing layer along with the backing sheet of cover material (white paper), this is then rolled to make an even surface, then allowed to set for a period of 15 minute before being removed from the mould base. It was allowed to air dry @ 25 °C for 8 weeks prior to being used for testing purposes (a cure/dry time of one year was allowed for the impact test). The weight of this board was 15.08kg per square meter. Carbon powder board with air entrainment

Firstly samples of this board were prepared to be used in the experiments below. The test board was made 12.5mm in thickness using medium density "black type" charcoal made from hardwood, Indonesia. Charcoal Density was 0.59g/ ml.

Ingredients. Gypsum plaster Charcoal Powder Water Foam

@ 40°C Agent

sodium

lauryl

sulphate

Proportion 1.0 0.5 1.0 0.002

Weight Used 2.0kg 1.0kg 2.0kg 0.004

A plaster mix containing charcoal powder and an air entrainment agent (sodium lauryl sulphate) is mixed with a large electric cake mixer at high speed with two whisk attachments each with four blades, this foamed mix is extruded on top of the facing paper along with the backing sheet of cover material (white paper), this is then rolled to make an even surface, then allowed to set for a period of 15 minute before being removed from the mould base. It was allowed to air dry @ 25°C for 8 weeks prior to being used for testing purposes (a cure/dry time of one year was allowed for me impact test). The weight of this board was 11.1kg per square meter.

Carbon Granule board

Firstly samples of this board were prepared to be used in the experiments below. The test board was made 12.5mm in thickness using medium density "black type" charcoal made from hardwood, Indonesia. Charcoal Density 0.59g/ml

Ingredient Gypsum plaster Charcoal Granules - Fine, Water @ 40 °C

Medium and Course grades [no dispersant of

superplasticizer

0.5 - 12mm 0

was used]

Proportion 2.0 1.0 1.0 - Weight used 3kg 1.5kg 1.5kg

This recipe uses charcoal granules which are preferably 0.5 - 6mm in diameter but did include coarse granules up to 12mm in diameter. Fine, medium and course grade granules can be gathered at 2305, 2310 and 2315 using the process shown in figure 3 for example. The plaster mix and the board are formed using the processes shown in 1100, 1200, 1300 in figure 1. This recipe produced a lighter weight board without using air entrainment giving impact and acoustic reduction properties while mamtaining fire resistance. The weight of the board made is 11.9kg per square meter.

Lower water content can be achieved with this mixture if a water dispersant (superplasticizer) is used.

The following tests were performed to compare the properties of some of the above embodiments against each other and/ or against normal gypsum plasterboard without charcoal.

Test l

Aim: To compare carbon plasterboards effectiveness at removing odours and/or adsorb volatile organic compounds against standard contemporary commercially produced gypsum plasterboard. Method: Two lidded boxes were made with inside dimension of 300mm square floor and 200mm high walls. The 300mm square lid was hinged, all joints were taped. One box was made from Dual density impact carbon plasterboard 12.5mm in thickness, with the granular charcoal face inside; the second box was made from commercially produced standard gypsum plasterboard 12.5mm in thickness.

A glass dish 70mm 0 that contained 0.2ml of perfume was placed in each box for a period of 60 seconds, with the lid closed, the glass dish of perfume was then removed and the lid immediately shut. After a period of one hour the boxes were opened and a sniff test was performed.

Results

The box made from Dual density impact carbon plasterboard had no residual smell of perfume after the one hour period.

The box made from commercially produced gypsum plasterboard had a very detectable residual smell of perfume after the one^hour period. After a two hour period the perfume could still be smelt in this box if the lid was left shut after the first sniff test was performed.

Conclusion

This was a simple test but effectively demonstrates that plasterboard with granular charcoal mix on the facing surface is able to remove odours, and/or adsorb volatile organic compounds much more effectively than standard gypsum plasterboard.

Test 2

Aim and method was the same as for test 1, however a lighted cigarette replaced the perfume the glass dish. The dish with the lighted cigarette was placed in each box for a period of seconds, with the lid closed, the glass dish with the lighted cigarette was then removed and the lid immediately shut. After a period of one hour the boxes were opened and a sniff test was performed.

Results

The box made from Dual density impact carbon plasterboard had no residual smell of cigarette smoke after the one hour period.

The box made from commercially produced gypsum plasterboard had a very detectable residual smell of cigarette smoke after the one hour period. After a two hour period the cigarette smoke could still be smelt in this box if the lid was left shut after the first sniff test was performed.

Conclusion

This test effectively demonstrates that plasterboard with granular charcoal mix on the facing surface is able to remove the odour of cigarette smoke and/ or adsorb harmful organic compounds contained in cigarette smoke such as acetaldehyde much more effectively than standard gypsum plasterboard.

Test 3

Aim and method was the same as for test 1, however the boxes were filled- with five 150mm square sheets of 12.5mm thick plywood. The plywood was newly manufactured and freshly cut to size, this replaced the perfume in the glass dish. The plywood was placed in each box for a period of 60 seconds, with the lid closed, the plywood was then removed and the lid immediately shut. After a period of one hour the boxes were opened and a sniff test was performed.

Results

The box made from Dual density impact carbon plasterboard had no residual smell of plywood after the one hour period.

The box made from commercially produced gypsum plasterboard had a detectable residual smell of plywood after the one hour period. After a two hour period the plywood could still just be smelt in this box if the lid was left shut after the first sniff test was performed, (plywood has a smell of cut wood and urea formaldehyde glue).

Conclusion

This test effectively demonstrates that plasterboard with granular charcoal mix on the facing surface is able to remove the odour of new plywood and/ or adsorb harmful organic compounds released from plywood such as formaldehyde much more effectively than standard gypsum plasterboard.

Urea formaldehyde glues are extensively used for interior and intermediate grade bonding, which covers the majority of hardwood plywood produced. Test 4

Aim: To compare carbon plasterboards effectiveness at absorbing atmospheric moisture and re- released against standard contemporary commercially produced gypsum plasterboard.

Method: Two lidded boxes were made with inside dimension of 300mm square floor and 200mm high walls. The 300mm square lid was hinged, all joints were taped. One box was made from Dual density impact carbon plasterboard 12.5mm in thickness, with the granular charcoal face inside; the second box was made from commercially produced standard gypsum plasterboard 12.5mm in thickness.

A glazed ceramic plate 200mm 0 that contained cotton hand towel dampened with 130g of water was placed in each box for a 12 hour period with the lid closed and the weight change due to moisture evaporation of the towel was observed along with the weight gain of the plasterboard box. Weighing was carried out every two hours. The plate and towel were removed for weighing and the lid immediately shut, the empty box was also weighed. The plate and towel were quickly replaced in the box after weighing.

After the 12 hour period, the towel was removed and the box lids left open.

Results

As shown in figure 11, the box made from Dual density impact carbon plasterboard adsorbed moisture twice as quickly as the box made from commercially produced gypsum plasterboard. After the 12 hour period, the towel was removed and the box lids left open. The box made with carbon plasterboard took only four hours to loose 3g of weight gained by adsorbing moisture, while the box made from gypsum plasterboard took 4 hours to loose 3g of adsorbed moisture. Conclusion

Some moisture loss was apparent as the boxes were opened for weighing, however this would simulate the normal ventilation and opening and closing of doors in a typical house. This test effectively demonstrates that plasterboard with granular charcoal mix on the facing surface is able to impart humidity conditioning performance or passive humidity control in buildings utilising these boards. In humid conditions the charcoal within the board absorbs moisture from the atmosphere, then in dry conditions the water is re-released into the atmosphere.

Excellent humidity absorption reduces dew condensation, the result is a decrease of mould and mildew due to lower adherence or airborne dust on the board surface. Test 5

Aim: To compare the surface indentation resistance of dual density impact carbon plasterboard, carbon powder plasterboard, carbon granule plasterboard against standard contemporary commercially produced gypsum plasterboard.

Method: Samples of the boards to be tested were prepared (dimension of 200mm square and 12.5mm thick) and placed on a flat steel surface. A round 10mm 0 die is placed on the board and a lkg weight is dropped onto the die from a height of 1 meter. This test is carried out 3 times and the indentations measured with an average of all three tests giving the result. The test samples were cured and dried together for a period of one year prior to testing, the commercially produced gypsum board was purchased one year prior to testing and may have been a few months old at the time of purchase.

Results

The surface indentation of dual density impact carbon plasterboard was .1mm

The surface indentation of carbon powder plasterboard was 2.1mm

The surface indentation of carbon granule plasterboard was 2.0mm

The surface indentation of standard gypsum plasterboard was 4.2mm

Conclusion

This test effectively demonstrates that plasterboard with granular and / or powder charcoal mix on the facing surface is able to withstand impact from small hard objects much more effectively than standard gypsum plasterboard.

Test 6

Aim: To compare carbon plasterboards effectiveness as an insulating material against standard contemporary commercially produced gypsum plasterboard.

Method: Sheets of plasterboard were framed up to be able to replace house windows. Four frames were made to simultaneously test four different boards at the same window location. The first used Dual density impact carbon plasterboard, 12.5mm in thickness, with the granular charcoal face inside; the second frame used carbon granule plasterboard, 12.5mm in thickness, the third frame used commercially produced standard gypsum plasterboard 12.5mm in thickness, the fourth frame used carbon powder plasterboard with air-entrainment, 12.5mm in thickness

The frames were stored inside at a constant room temperature of 18.4 °C, at the start of the test they were installed in the open window frame, the outside air temperature was a constant 8.4 °C so the temperature difference between inside and out was 10 C. Surface temperature readings were taken at 20min intervals using a digital infrared sensor. Inside humidity was 58%.

Results Figure 12 shows the granular carbon plasterboard had the best insulation characteristics by retaining heat for the longest period of time. All carbon plasterboards outperformed the standard gypsum plasterboard which used air-entrainment to form the gypsum core.

Conclusion

Carbon plaster boards with high levels of carbon granules in the mix provide good insulation characteristics. All carbon plaster boards are better insulators than standard gypsum plasterboard.

Test 7

Aim: To compare carbon plasterboards effectiveness as a sound insulating material against standard contemporary commercially produced gypsum plasterboard.

Method: A sound proof box was prepared that contained a sound absorbing lining, the box had no lid. Four lids were made from the following plasterboards:

Dual density impact carbon plasterboard, 12.5mm iri thickness, with the granular charcoal face inside; carbon granule plasterboard, 12.5mm in thickness; carbon powder plasterboard with air- entrainment, 12.5mm in thickness; commercially produced standard gypsum plasterboard 12.5mm in thickness. A loud alarm clock was placed in the box and the various lids put on and the sound transmission through the lid observed.

Results All lids did a good job at reducing the sound level of the alarm, however the carbon plaster boards all reduced the alarm volume slightly more than the commercially produced standard gypsum plasterboard.

Conclusion

All carbon plaster boards provide good sound insulation characteristics. Test 8

Aim: To test carbon plasterboards effectiveness as fire resistant material compared to standard contemporary commercially produced gypsum plasterboard.

Method: Sheets of plasterboard were vertically mounted and a gas torch flame was directed onto the facing surface of the board. The flame temperature was 1450°C. This experiment was carried, out at an ambient temperature of 18°C and humidity of 58%

The following plasterboards were tested:

Dual density impact carbon plasterboard, 12.5mm in thickness, carbon granule plasterboard, 12.5mm in thickness; carbon powder plasterboard with air-entrainment, 12.5mm in thickness; commercially produced standard gypsum plasterboard 12.5mm in thickness. The plasterboards. backing side surface temperature was taken at 30 second intervals using a digital infrared sensor. Results

As shown in figure 13 all types of plasterboards performed equally as well as the standard gypsum board in terms of fire resistance by maintaining similar heat profiles. After the temperature testing concluded at 14 minutes, the flame was removed and the boards were allowed to cool. None of the boards showed any signs of igniting or smouldering.

Conclusion

The charcoal showed no sign of igniting during the term of the experiment.

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention as defined by the accompanying claims.

Claims

CLAIMS:

1. A method of forming a board comprising the steps of: mixing gypsum plaster, charcoal and water to form a plasterboard mixture and allowing the plasterboard mixture to set, wherein the charcoal comprises charcoal powder.

2. A method as claimed in claim 1 further comprising the step of placing the plasterboard mixture between two sheets of cover material prior to allowing the mixture to set.

3. A method as claimed in either one of claim 1 or claim 2 wherein the step of mixing further comprises mixing at least one foaming agent with the gypsum plaster, the charcoal and the water.

4. A method as claimed in claim 3 wherein the step of mixing comprises mixing the gypsum plaster, the -charcoal powder, and the water in a mixer and adding a pre-formed foam comprising one or more foaming agents and water.

5. A method as claimed in claim 3 wherein the step of mixing comprises: mixing the gypsum plaster, the charcoal powder, a foaming agent and the water in a mixer to form a slurry, and then adding compressed gas to the slurry to create air entrainment.

6. A method as claimed in claim any one of claims 3 to 5 wherein the foaming agent is sodium lauryl sulphate'.

7. A method as claimed in any one of claims 3 to 6 wherein the step of mixing is carried out in an air entrainment mixer.

8. A method as claimed in any one of the preceding claims wherein the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal powder to 0.6 - 2 parts water.

9. A method as claimed in claim 8 wherein the dry mass based proportions of the plasterboard mixture are 1.0 part gypsum plaster to 0.5 parts charcoal powder to 1.0 part water.

10. A method as claimed in any one of claims 1 to 7 wherein the charcoal further comprises charcoal granules.

11. A method as claimed in claim 0 wherein the step of mixing comprises:

passing the first mixture into a second mixer, and

12. A method as claimed in claim 11 wherein the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 0.75 parts charcoal powder to 0.01— 0.75 parts charcoal granules to 0.6 - 1.25 parts water.

13. A method as claimed in claim 12 wherein the dry mass based proportions of the plasterboard mixture are 2.0 parts gypsum plaster to 0.25 parts charcoal powder to 0.25 parts charcoal granules to 0.9 parts water.

14. A method as claimed in any one of claims 1 to 7 or claim 10 wherein the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01 — 1.5 charcoal to 0.5— 1.5 water.

15. A method as claimed in claim 14 wherein the dry mass based proportions of the plasterboard mixture are 2.0 parts water to 1.0 part charcoal to 1.0 part water.

16. A method as claimed in either one of claim 10 or 11 wherein the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.5 - 0.9 parts charcoal powder to 0.1- 0.5 parts charcoal granules to 1 - 1.5 parts water.

17. A method as claimed in claim 16 wherein the proportions of the plasterboard mixture are 2.0 parts gypsum plaster to 0.7 parts charcoal powder to 0.3 parts charcoal granules to 1.25 parts water.

18. A method as claimed in claim 10 wherein the step of mixing consists of: mixing gypsum plaster, the charcoal granules and water to form a facing layer plasterboard mixture, and mixing gypsum plaster, the charcoal powder and water to form a backing layer plasterboard mixture.

1 . A method as claimed in claim 18 wherein the step of placing the mixture between two sheets of cover material comprises: extruding the facing layer mixture onto a sheet of cover material, and extruding the backing layer mixture onto the facing layer mixture.

20. A method as claimed in either one of claim 18 or 19 wherein the dry mass based proportions of the facing layer mixture are 2.5— 3.5 parts gypsum plaster to 0.01 - 1.5 parts charcoal granules to 0.5— 1.5 parts water and the dry mass based proportions of the backing layer mixture are 1.5 — 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal powder to 1 - 2 parts water.

21. A method as claimed in claim 20 wherein the dry mass based proportion of the facing layer mixture are 3.0 parts gypsum plaster to 1.0 part charcoal granules to 1.0 part water and the dry mass based proportions of the backing layer mixture are 2.0 parts gypsum plaster to 1.0 part charcoal powder to.1.5 parts water.

22. A method as claimed in any one of claims 18 to 20 wherein the charcoal granules consist of fine and medium grade granules.

23. A method as claimed in any one of claims 18 to 20 wherein the charcoal granules consist of coarse grade granules.

24. A method as claimed in claim 23 wherein the method of forming the board further comprises removing the sheet of cover material adjacent the facing layer after the mixtures have set and shaving an exposed surface of the facing layer to expose the charcoal.

25. A method as claimed in any one of the preceding claims wherein at least a portion of the charcoal is hydrated to increase the mass of the charcoal prior to mixing the charcoal with water and gypsum plaster.

26. A method as claimed in claim 25 wherein the charcoal is soaked in water for a period of time to hydrate the charcoal.

27. A method as claimed in claim 25 wherein the charcoal is placed in a vacuum chamber and water is applied under pressure to the chamber to replace air voids and hydrate the charcoal.

28. A method as claimed in any ¹ one of the preceding claims wherein the step of placing the plasterboard mixture between the two sheets of cover material comprises extruding the plasterboard mixtures between the sheets of cover material and pressing on either side of the sheets of cover material at a moulding station to form a mould.

29. A method as claimed in claim 28 further comprising: forming an edge mix of charcoal, gypsum plaster and water, wherein the charcoal comprises charcoal powder or fine grade charcoal granules or both, and extruding the edge mix along the edges of the sheets of cover material, the plasterboard mixture then being extruded within the edge mix before being pressed and formed into a mould.

30. A method as claimed in claim in either one of claim 28 or 29 further comprising after forming the mould, allowing the mould to set and cutting the mould into one or more boards to be placed in a baking kiln for a period of time to harden.

31. A method as claimed in any one of the preceding claims wherein prior to mixing charcoal is filtered through a sieve screen having a mesh width of 0.4-0.5mm to collect the charcoal powder for mixing.

32. A method as claimed in any one of the preceding claims wherein prior to mixing charcoal is exposed to a blower to separate and collect the charcoal powder for mixing.

33. A board formed from using any one of the methods of claim 1 to claim 32.

34. A method of forming a board comprising the steps of: mixing gypsum plaster, charcoal and water to form a plasterboard mixture and allowing the plasterboard mixture to set, wherein the charcoal comprises charcoal granules.

35. A method as claimed in claim 34 further comprising the step of placing the plasterboard mixture between two sheets of cover material prior to allowing the plasterboard rnixture to set.

36. A method as claimed in either one of claims 34 or 35 wherein the plasterboard mixture comprises only fine and medium grade charcoal granules.

37. A method as claimed in claim 36 wherein the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal granules to 0.5 - 2 parts water.

38. A method as claimed in claim 37 wherein the dry mass based proportions of the plasterboard mixture are 1.0 part gypsum plaster to 0.5 parts charcoal granules to 1.0 part water.

39. A method as claimed in either one of claim 34 or claim 35 wherein the plasterboard mixture comprises course grade charcoal granules.

40. A method as claimed in claim 39 wherein the dry mass based proportions of the plasterboard mixture are 1.0— 2.5 parts gypsum plaster to 0.01— 1.5 parts charcoal granules to 0.5— 2 parts water.

41. A method as claimed in claim 40 wherein the dry mass based proportions of the plasterboard mixture are 1.3 - 2.0 part gypsum plaster to 1.0 parts charcoal granules to 0.8 - 1.0 part water.

42. A method as claimed in either one of claim 34 or claim 35 wherein the dry mass based proportions of the plasterboard mixture are 1.5— 2.5 parts gypsum plaster to 0.5 - 1.5 charcoal to 0.5— 1.5 water.

43. A method as claimed in claim 42 wherein the dry mass based proportions of the plasterboard mixture are 2.0 parts water to 1.0 part charcoal to 1.0 part water.

44. A method as claimed in any one of the preceding claims wherein at least a portion of the charcoal is hydrated to increase the mass of the charcoal prior to mixing the charcoal with water and gypsum plaster.

45. A method as claimed in claim 44 wherein the charcoal is soaked in water for a period of time to hydrate the charcoal.

46. A method as claimed in claim 44 wherein the charcoal is placed in a vacuum chamber and water is applied under pressure to the chamber to replace air voids and hydrate the charcoal.

47. A method as claimed in any one of claims 34 - 46 wherein the step of placing the plasterboard mixture between the two sheets of cover material comprises extruding the plasterboard mixtures between the sheets of cover material and pressing on either side of the sheets of cover material at a moulding station to form a mould.

48. A method as claimed in claim 47 further comprising: forming an edge mix of charcoal, gypsum plaster and water, wherein the charcoal comprises charcoal powder or fine grade charcoal granules or both, and extruding the edge mix along the edges of the sheets of cover material, the plasterboard mixture then being extruded within the edge mix before being pressed and formed into a mould.

49. A method as claimed in either one of claim 47 or claim 48 further comprising after forming the mould, the steps of allowing the mould to set, and cutting the mould into one or more boards to be placed in a baking kiln for a period of time to harden.

50. A board formed from any one of the methods of claim 34 to claim 49.