GB2377931A

GB2377931A - Thermally insulating materials

Info

Publication number: GB2377931A
Application number: GB0223211A
Authority: GB
Inventors: Branko Richard Babic
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-07-07
Filing date: 1999-07-07
Publication date: 2003-01-29
Anticipated expiration: 2019-07-07
Also published as: GB0223211D0; GB2377931B

Abstract

A thermally insulating composition comprises a high temperature tolerating cement, ideally a calcium aluminate cement, and a refractory material ideally chosen form fine clay, cordierite, zirconia, exfoliated clay, glass, ceramic, vermiculite, perlite, silicon carbide, a nitrate, basalt, brick or a mixture thereof. The composition is made into a useful material by forming into the appropriate shape and heating the composition to over 1200 {C for over 24 hours. Also disclosed is a material comprising a homogenous mixture of particles and a matrix binder which only just coats the particles, wherein in the first embodiment the binder is selected from bitumen, phenolics, ureas, melamines, epoxides, polyurethanes, polypropylenes, rubbers, latex, acrylics, silicones or tar, whilst the particles may be expanded polystyrene, recycled plastic, rubber, perlite or vermiculite; in the second embodiment the binder is a ceramic whilst the particles are hydrocarbon based and in the third embodiment the binder is metal.

Description

LOW DENSITY MATERIALS The present invention relates to materials which have a matrix and a particle suspended in the matrix. The matrix can either be an organic or an inorganic binder.

Specific materials of this general class of materials have been previously disclosed in September 1996 at the 5th International Conference on Inorganic Bonded Wood and Fibre Composite Materials, Volume 5, pp 49-63, and the PIRA Conference in October 1996 and published in their conference proceedings, Volume 1, Uses for Non-Wood Fibres, Cement-Cellulose Composites.

- The above papers describe materials with a cement matrix. Ground organic particles with a particle diameter of up to 5 mm are suspended in the cement matrix.

Other products can be created by mixing exfoliated clays or ash with cement, gypsum and suspended particles.

This technology derived from work on damp-proofing materials, where it was shown that large quantities of air in cement mixers did not cause any significant loss of

crushing strength It was hard to control the size of the air vacuoles in the mix Expanded polystyrene was added to the mix to perform the same function as the air vacuole This work was done using expanded polystyrene beads of lmm and less in diameter.

The materials developed during this work are known as STYROCRETE or STYROCEM (suspended polystyrene particles), CORKCRETE or CORKCEM (cork), STRAWCRETE or STRAWCEM (straw), WOODCRETE or WOODCEM (sawdusr), PAPF, RCRPTE or PAPERCEM (paper), CELLUCRETE or CELLUCEM (general

. -

cellulose). The "CRETEs" have a particle diameter of less than 5mm and the"CEMs" have a particle diameter of less than. Imm.., These materials produce considerable advantages. They are lighter than conventional cement, they can have gdocfreretardaLnt properties, low thermal and electrical conductivity and a high heat tolerance. Their fire retardant properties and heat tolerance stem from the fact that the matrix is heat tolerant and has a very low thermal conductivity. The low thermal conductivity is enhanced by the suspended particles in the matrix.

Slabs of cement with expanded polystyrene particles have now been made with 50% by volume recycled expanded polystyrene. Thus, the weight of the slabs is reduced by nearly 50%. These slabs are useful for the home DIY market. Also, garden ornaments, coping stones for the building industry and low density garden wall decorative screens have been manufactured using this material Cladding sections also benefit from the reduction in weight.

Further improvements have been made to these types of materials, The rigidity of inorganic matrixes can-br reduced by adding about 2% by weight of styrene type material to inorganic clays. More or less styrene can be added depending on the required end properties.

In addition, water repellent preparations can be added to prevent ingress of moisture into the finished products or materials made with the inorganic matrixes It has been mentioned above that not only styrene particles can be suspended in the matrix. Cellulose materials can be used instead. It has been disclosed in the above referenced papers that cellulose materials can retard the setting of cements The curing of cement based materials is dependent on the'chemistry of the cements and their additives

As an example only, the curing of calcium aluminate cement (a specialist cement used in high temperature-applications) ; or Portland cement (a conventional cement used in construction), in the presence of ce cellulose retarders is dependent on the number of molecules of water of crystallisation, attached to the cement molecule In the presence of sugars, tannins, lignins, cellulose molecules and other polyhydroxy molecules, the setting properties are retarded so that the crystal structure of the cement cannot form This retardation effect is attributed to the establishment of hydrogen bonding between hydroxyl group of the retardingmo1ecule and the water molecules attached to the cement molecule The water of crystaisatton sation plays a vital part in the stability of the cement crystal and the number of wåter molecutes, (being part of the cement molecule) affects the properties of the cement crystal to a considerable extent. The cement crystal cannot form properly if the number of water molecules attached to the cement molecule is too large. Controlling the number of molecules of water of crystallisation is therefore a factor which controls the rate of crystal formation and therefore the rate of setting of a given cannent.

Heat can be used to reduce the quantity of water in the slurry in an effort to achieve the optimum water of crystallisation. Heating the slurry to 80 C from about 8 hours achieves the required state for Portland cement type binders.

- I.- When CAC is used, heating to 800C for about 2 hours allows the cement to achieve most of its ultimate strength.

In the presence of retarding additives such as cellulose fibres, there is retardation

of this settiii, of this setting process For Portland cements-heating at 80 C for 24 hours. drives off enough water to allow cement crystals to form. Higher temperatures can be used (eg.

I SO'C) to speed up the removal of water from the slurry, The time for die d : tvmg off f'. v. c'' reduced at higher temperatures,

When CAC is used as a binder m the presence ofcellulosic fibres, adding the Lithium Carbonate accelerator, facilitates the formation of the crystal phase within 2 hours of kiln drying. Most of the final strength of this cement is achieved within this time span The problem of retardation with cellulose based materials has been recognised

in the above described publication. In a first aspect, the present invention provides a .., . r method of making a low density material, method comprising the steps of : a) mixing cement powder with Water to form a mixture, b) adding organic or inorganic particles to the mixture, and c) heating the product of (b) to drive off the excess water This serves to drive off the surplus water molecules and allows the cement to set by achieving a thermo-dynamically stable state. It may be preferred to continue heating the cement mixture for a prolonged period ag. 12-24hrs. In this case, as a number of water molecules is gradually reduced, the cement is able to align itself in proper relationship for it to crystallise into a thermo-dynamically stable state The setting of the cement is therefore-a process whereby the cement molecules are hydrated and achieve a lower energy state in the crystallised form they possess in the slurry state. The number of water molecules attached to the cement molecule in the slurry state, exercise a vital roll in the change of phase leading to the crystallised thermo-dynamically stable state.

It is more preferable if in the method @@cording to the first aspect of the present invention, the product of (b) is heated to above 60 C.

If the cement is calcium aluminate cement, it is preferable if the product of (b) is head to a temperature in the range of 700C to, 900C.

If the cement is Portland cement it, is preferable if the product of step (b) is heated to a temperature in the range of 1700C to 1900C.

,. ; > -, - Recently it has been surprisingly found that a small amount of accelerator needs to be used in the setting of such cements. Therefore, it is preferable if the method comprises the step of adding an accelerator. The accelerator used with calcium aluminate cement is Lithium Carbonate. In the construction industry all measurements are in weight so that composite materials are weight batched.

Accelerated calcium aluminate cement preferably requires about 0. 05% ie. typically 0.04% to 0. 06% of Lithium Carbonate by weight of added cement, to provide accelerated setting of Calcium aluminate cement.

The cement and water content is determined by the manufacturer's instructions for preparing the cement in the conventional manner, ie. no particles added. When using cellulose particles, the cellulose is usually saturated before adding to the cement.

I r.

It has been mentioned above that these types of materials can have suspended organic panicules with diameters of less than 5 mm, and in some cases preferably less than 1 mm. It is expensive to reduce organic materials to the required size. Most of the

cost is incurred where, (for example, the reduction of straw to a suitable size particle) requires the use of heavy duty milling machinery : The wear and tear and the grinding components is very heavy because there is a high silicone content in the fibres.

" r..',.'. \,'. I " It is preferable if the organic materials are reduced using a cryogen such as liquid nitrogen In this method, organic particles (straw, for example) are immersed in liquid nitrogen to solidify into a very brittle state. The very low temperatures required to liquefy nitrogen, freezes the straw cells into a rigid form that cannot flex. In this state, the straw is passed between crushing rollers to shatter the structure into tiny particles. The arrangement and design of the crushers controls the size of the particles resulting from the process. Particles of any size can be produced by this method.

The larger sized particles that are to'be, coated in the various matrixes for use as a loose fire retardant insulating material can be mechanically sieved or separated by cyclotron separators.

The various fractions resuiting from tha fracturing process can be separated into various grades suitable for the various proposed material design. If the larger size panicles are to be further reduced, these fraction can be recirculated into the liquid nitrogen and passed through the rollers again.

The fractured material is delivered the evaporating containers designed within machinery, where the temperature is allowed to rise. The liquid nitrogen vaporises to be recirculated and condensed into liquid and used repeatedly. The dry fractured straw is then moved and subjected to cyctotronic air flow or vortex separators tu separate the fractured particles into various receptacles for predetermined sizes. This process has the advantage that no grinding is involved and the wear and tear on the crushers is minimal.

Liquid nitrogen does not wet the cellulose material being fractured. As the temperature is allowed to increase from the cryogenic temperature, the liqu@d nitrogen changes state from its liquid phase into the vapour phase (-77K) The gas evaporates from the straw particles, and the cryogenised straw remains in a powdered or panicle state.

The reduction of cellulose matter in. this way becomes cost effective for many industrial processes, be it for the paper industry or the manufacture of a cement bonded material.

This technique can also be used to make small particles of polystyrene from second hand expanded polystyrene packaging'etc Also, tyres can be used to produce small hydrocarbon particles.

The usefulness of the above technology developed to produce low density cements continues to be extended, The addition of expanded polystyrene and the other

group of materials consisting of hydrocarbon and cellulose additives as a means of controlling the size of the vacuoles is proving exceptionally useful for further applications A new class of materials has now boan-developed based on the above principles-

Thesematerialshaveanorganic matrix. They possess some fire retardant properties but appear exceptionally useful for padding or protective purposes ; a group of materials that have very low density. They are generally hydrophobic.

In a second aspect, the present invention provides a material comprising a substantially homogenous mixture of particles with diameters of less than 5 mm and an organic material which serves as an organic matrix and binder for the parricies.

Preferably, the organic matrix is chosen from one or more of the following : bitumen, polyesters, phenolics, ureas, melamines, epoxides, etc and known viscous hydrocarbon matrixes such as polymers, polypropylenes, polyurethanes, fibbers, latex, plastics, acrylics, resins, silicone rubbers and tar. Tar is a waste product from oil distillation. Therefore, tar is a particularly preferable matrix, The above list is not exhaustive, the-organic matrix can be any synthetic or natural material that can be mixed with a particle to produce pliable, resilient, or hard materials that have a very low density and lend themselves to considerable number of different applications.

The suspended particle can either be organic, inorganic or a combination of I., both A particular example of this type of material has an elastomeric matrix with expanded polystyrene or recycled plastics, rubbers, synthomers and expeditcd inotranic

materials as additives. This material is pliable and also possesses the low density and heat resident properties of the so-called "crete" group of materials Preferably, the diameter of the particles is between lm and 5mm. Mixtures of different particle sizes can be used.

More preferably, the particles make up between 99.5% by volume and 25% by volume of the total volume of the compound. The quantities used determine the properties of the finished product. Cellucrete has 30% by volume of cellulose additive.

Because the quantity of the binder material is compared to the volume of the particles, these materials typically have a very small "heat sink capacity".

Preferably, the elastomeric matrix is art acrylic, a rubber or a plastic.

If the suspended particle is polystyrene, beads or sanded or re-processed , . - expanded polystyrene can be used. Also, recycled plastics, rubbers (e g. tyres etc) or other recycled materials can be used.

These materials can be applied to designs for protective padding, cushioning, sound absorption systems and the like.

In all cases, the addition of expanded polystyrene provides a physical entity

which can be coated by the matrix to control the size of the vacuole. The size of the added bead controls the size of the vacuoles in the material. Inorganic materials such as ceramic clays, (or glass) silicone based aerated spheres such as "floaters" can also be used to provide a measured vacuole.

The relationship between the size-of the-beads and the strength of the material is proportional. Strength decreases as the size of the beads increase. The smaller the size

of the bead, the greater the surface area oftne b'eads and the greater the volume of The matrix materials th ; 1t have to be used to cover all the particles. Therefore, it is

preferable if the diameter of the particle is m the range of 2. 5mm to 3. 5mm. The

.. . particles can be separated by the method discussed in the published papers or discussed earlier in this document.

Materials according to a second aspect of the present invention have a continuity of matrix that makes them useful for punctureproof tyres on vehicles Such materials can be used on their own or in combination with other reinforcing materials to provide a variety of designed materials for specific-uses. They can encase OTher materials to provide an outer resilient component.

Experiments with the above concept materials continues and in situations where soft organic matrixes such as rubber, polyurethanes, plastics and other available organic

-" matrixes need to be used because of their flexible characteristics, very novel features have emerged.

A mixture of the above matrixes e. g. rubber, pre vulcanised rubber solution, or vulcanised rubber, when mixed, for example, with powdered perlite, provides a novel material that has"smart"characteristics. The density of the rubber matrix increases during heat stress, the greater the amount of heat the greater the density increase. This in fact is a passive phenomenon due to the expansion of air trapped in the exfoliated material used as an example only, perlite, vermiculite, expanded polystyrene or any of

the aforementioned additives whose space expands to compress the rubber matrix. Compression of the matrix increases the density of the matrix. This is also seen in other organic matrix materials. However, it should be noted that as the total volume of the heat stressed material increases, the surfacejayers are obviously stretched and become less dense.

The other useful characteristic of these materials is the crust formation of the

heat damaged area of material. In this case, the organic material is burnt at the surface and as the organic material melts the inorganic perlite or vermiciilite powder or particl-q-f ; ibout I nim to I im emerge ouof th matrix to"coagulate"al the surface

of the damaged area of the material. As more of the organic matrix is oxidised in the fire, more additive is freed from the matrix to add to the thickness of the inorganic "crust". The inorganic "crust" soon forms an impermeable "membrane" which retards the ingress of oxygen into the heat stressed material and retards the rate of burning.

These materials therefore achieve fire retardant properties because much of the impinging heat is reflected by the"Crust"area of inorganic additive protecting the rubber matrix of the product. Another advantage is realised in that, the temperature gradient within the material is decreased,'and hence the rate of damage is also decreased.

A very useful range of soft fire retardant materials is obtained These materials can be used as fire retardant mastics. By manufacturing components made from the above mixes of organic matrixes and inorganic additives a new group of"smart" materials is produced, These materials increase their density as they are heat stressed and from "coagulates" of inorganic crusts only in areas of damage which are severe enough to burn the organic material. When silicone rubber matrixes are used, temperatures of less than 1000'C can effectively be contained without being damaged.

The above group of materials can be pumped into conduits and openings, interfacial spaces, cavities and the like to form fire retardant protection for electrical. ventilation ducts etc. The containment of fires in a given compartment being the object of the exercise.

The low density of the organic matrix and the inorganic panicle material provides a material which can be used to seal junctions between construction elements

in vibrating structures. The advantage of this non hard fire retardant material is that the material adheres to all structurasl components it is in contact with and forms a fire retardant movable seal. The fact that the components of the structure are vibrating or moving about prevents fire ingress from one compartment into another because the organic matrix allows movement to occur without fracturing the matrix. Such materials arc id ! y suhabe to moving structures and may even be desirable to airborne utilities,

The"crust"formation can be achieved with other materials such as ground sand and pulverised ash and other materials that can be properly prepared in the less than I mm. The exfoliated days such M vermieulite and perlite are well established and easily available materials that can be used but many other additives are available and it is only a matter of practicality as to which of the many materials are used for the above purpose.

Above materials can be used as a first fine of defence in fire retardant applications in ducts and through openings. By making rubber composite plugs in this material, the plug can retard the egress of fires from one space into another.

These organic matrix materials allow the design of a multitude of components designed to provide fire retardant structures for the ducting and shaft opening required for electric cables, plumbing fittings and other such conduits having to pass through the separating structure from one space into another.

The use of specially prepared cables would be of benefit in situations where fire retardation was desirable. The earlier described mixtures of organic and inorganic additives can act as heat reflectors when applied to services or electrical cables as coatings or factory applied coverings. A suitable formulation of the plastic coatings applied to electrical wires, can be modified with the addition of, for example, the perlite dust. The mixture is used to coat the electrical cables to provide fire retardant coatings to electrical wires and the like. This system can also be used to provide coatings to

structural members such as girders, trunking for electrical cables and other services etc.

Materials according to a second aspect of-the present invention can be preferably used in end pieces for cable ducting. Thus, in a third aspect, the present invention provides an end piece for cable ducting comprising a block of material according to a second aspect of the present invention with at least one hole through the block of -'.,. , - - - r'rcrial for insenion nf a cable therethrough.

More preferably, the block of material of the end piece comprises two separable sections which abut along a line of attachment and said at least one hole lies on said line of attachment. Even more preferably, the end piece comprises more than two separable sections and said holes lie on the lines of attachment of the separable sections.

In a preferred example of the end piece, the block of material comprises two sections which a hingeably mounted to one another such that the two sections meet at a line of attachment and said at least one hole lies on the line of attachment. Even more preferably, the end piece comprises more than two separable sections and said holes lie on the lines of attachment of the separable sections., The usefulness of the above system for soft matrix materials exrends to the mastics specifically designed to expand as they are subjected to heat stress These so called intumescent systems work on the principal that vaporised water trapped 1I1 the material which is released to increase the volume of the bulk of the material to manifest the intumescent. Other intumescent systems work by heated gas expanding the mass of the material.

Water filled expanded polystyrene or spheres, saturated perlite and vermiculite dust coated in this elastomeric matrix can provide a great deal of water in fire situations. Similarly, the spheres can be manufactured in inen gas atmospheres and become filled with inert gas. Hence, the spheres can be used as inert gas carriers Therefore, in materials according to'a'second aspect of the present invention, it is preferable if the particle is a carrier containing an expandable substance. To clarify the above, and for the avoidance of doubt, an expandable substance in this context is taken to mean a material which has a larger thermal coefficient of expansion than the material of the panicle Therefore, on heating, the expandable substance expands at a quicker rate than that of the particle or carrier and eventually bursts out of the particle Typically, the expandable substance will either be water or an inen gas.

As an example only, water escapee'from a carrier eg. an expanded polystyrene bead when the carrier melts or bursts dlle'tQ-. hea. t stress, Intumescent mastics and other such materials are usually made from a mixture of compounds that are poor thermal conductors and can be vermiculite, carbon phosphates or other preparations and contain an expanding component These components are carried within the organic. component that can be acrylic or a number

of other components suitable for the purpose. In a fire, the trapped water expands to force the mass of the material to expand giving the intumescent effect. The organic matrix burns very slowly.

In order to maximise the effectiveness of the organic materials used in such materials, the addition of poor conductors to'the Mixture considerably reduces the heat transfer across the material, If additives of 1 mm to 1 11m are added to intumescent mastics heat ingress during a fire is reduced. If for example expanded vermiculite or perlite is added in any proportion to the intumescent mastic, the amount of heat transferred across the material is proportional to the amount of exfoliated material added.

Experiments have shown that even at a 50% mixture of expanded vermiculite to 50% intumescent mastic provides an intumescent mastic material that degrades at a slower rate than existing intumescent materials under the same conditions The addition of poor conductors to intumescent mastic materials be they vermiculite, carbon, perlite, floaters, carbon phosphate, or other composites is measurably better in reflecting the impinging heat when compared to the existing intumescent mastic formulations. Such additions have a very beneficial effect to the longevity of intumescent and other mastic and organic hased matrix materials, The rate of heat transfer across the matena ! Is lower in these materials than similar materials not containing the poor conductor additives

These low density materials 111$9 open. up the possibility of providing technology to build unsinkable flotation vessels.

For this use, bitumens provide a particularly useful matrix although any organic matrix could be used as a binder. Bitumens are long established materials in the maritime industry. Flotation vessels can be made which use materials with bitumen matrixes and glass spheres, ceramic spheres. expanded polystyrene, vermiculite, perlite and other exfoliated clays or synthetic exfoliated materials as the particle, Bitumens are hydrophobic and do not degrade in sea or fresh water. Other matrixes can also be used and even two stage matrixes can be used i. e. a hardening compound, eg, as used in epoxy resins, to provide hard, inflexible low density materials.

In a fourth aspect, the present invention provides a flotation vessel comprising a material in accordance with a second aspect of the present invention-

If the matrix is tar and the particles are inorganic particles, the method preferably comprises the step of heating the tar to over 1000"C prior to mixing. If the matrix is a silicon based rubber composite and the panicles are an inorganic exfoliated material, the silicon based rubber composite preferably forms between 40% to 60% by volume of the total mixture.

According to a fifth aspect, the present invention provides a method of making a low density material comprising the step of : Mixing particles of inorganic or organic material with a diameter of less than 5mm with an organic component which serves as a matrix and a binder Preferably, the matrix is water based bitufnen. More preferably the water based bitumen forms between 5 and 15% of the total volume.

Alternatively, the matrix can be à öifúmën compound with a melting point of

- -'. between 70 C and 90"C, the method funher comprises the step of heating the compound to above the melting point prior to the step of mixing the compound with the particles, More preferably, the bitumen compound forms between 30% to 40% of the total volume of the mixture.

Materials according to a second aspect of the present invention can be used to produce synthetic materials for the clothing industry, Polymers provide a substantial number of composites which are useful in the material industry. Cloths made from these polymers such as polyamides (nylons), polyesters, viscose, polypropylcncs,

rayon, the various resins etc., can all be usefully applied to the above technology The present invention can also be used to provide an absorbent material which can be used for nappies, kitchen towels, swabs, blotting paper, feminine towels, industrial absorbent socks etc.

Therefore, in a preferred embodiment, the matrix comprises two sheets which

face one another, the surfaces of the sheets which face one another being rough, and the particle5 being dispersed on the roughened faces of the sheets.

More preferably, the matrix of the present invention is paper and the panicies are provided by suspended straw particles.

The development of this absorbent material arose out of experiments working with wet mixtures and slurries with cellulose components. It was found, rhat an excessive amount of water was needed to achieve wetting and in many cases, the mixed water required well over 50% of the volume of straw used.

This was found to be due to the cellular nature of cellulose based materials. ! n straw, a very large proportion of the total volume is cavernulated. In a living plant. the

cells are full of cytoplasm which shrink and-recede when the plant is dried. 'he inside

of the cells becomes a cavity with a given capacity. The number of cells ill a given unit

.. J.. will therefore have a given volumetric capacity, the sum of which constitutes the largest volume of any given straw substrate- The absorbent material uses the fact-that the porosity of the cell walls allows the

cavities to fill up with fluid before and in preference to free water being available on the surface of the material. This is an extremely useful property. Not only can such a property be used for filtering purposes, but the sheer volume of liquid absorbed and held, makes straw in many ways an idea. ! absorption material.

Maximum absorption is achieved by preparing straw by the cryogenic method previously described. Straw reduced to a flour, (e. particles with a diameter of less than 1 mm, has the best absorption characteristic. The cells absorb fluid by capillary action into the cell cavities. Wetting the surfttce of the very small panicles lakes up more fluid and the particle interspace absorbs yet more of the available fluid The volume of liquid held by the above mechanism can be about equal in these materials to the volume of the straw flour.

A large number of applications lend themselves a very high absorption properties ; Industrial spillage can be contained, absorbed and swept up, contaminations of many accidental of other spillages can be contained by the above preparalion.

In biological applications, the absorbent properties of straw can be applied to manufacture swabs for surgical applications, dressings, incontinence pads, babies nappies, feminine towels, applicators, liners etc.

In other applications e. g, industrial -and domestic siruations, absorbent towels, wipes, toilet paper, absorbent pads of many sorts, blotting applications etc lend themselves to mind. Absorbent paper mixtures of many sorts can be manufactured using this technique.

It is interesting to note that fibres from different parts of this plant have different properties. As an example only, fibres obtalr1ed1rom the root systems tend to be stronger than fibres that are obtained from the trunk or branches.

With this in mind it is possible to use cellulose fibres that are obtained from root systems to manufacture"tough"paper that may'make it suitable for applications where a lot of wear and tear is expected. Tough paper can have many uses in paper items which require a lot of mechanical strength.

The strength of this paper is derive4. from the additional cross-links that are

achieved via the carbon 6 side chain of-the glucose base unit in cellulose. The number of these cross links is greater in root cellulose than in trunk or branch cellulose.

The manufacturing process can-be tailored to the material composition and its intended use. fn the paper industry, it may be desirable to sandwich a straw Dour filling in between layers of suitable paper for the intended use. In biological applications, the straw flour can be sandwiched between linen layers suitable for the rigors of sterilisation technology. In industrial applications, the material may be loose or sandwiched in suitable compositions or incorporated into the fabric of the material.

In at ! cases, the movement of the fluid should be free via the linings, 10 allow the capillary forces to move liquid from one space into another. Once the liquid is

inside the cells, fluid movement is restricted by surface tension forces Many cellulose fibres are available which lend themselves to the above uses.

The intended use for the absorbent properties at the straw flour will dictate the composition, texture, adhesive methodology,'h. ape etc of the finished product, Straw, which is made from sugar molecules, is a very nutritious material Many micro-organisms thrive on the cellulose material once it becomes wet. For this reason, straw base biological or medical products must be sterilised prior to use and kcpt drv

during storage. In a dry state, the products have an indefinite storage lifetime Once wet, the products should not be used for extended periods but discarded and replaced with a fresh product. For industrial use, the straw can be wetted and dried complete ! y The straw component does not suffer serious degradation by repeated wetting and drying. Such products can only be stored in very dry conditions.

The processing of straw can be achieved in many ways, but the end requirement will dictate the process. All straw can be bleached to provide while flour material that has no odour and does not release any coloration on being wetted. Textures of the straw can be controlled by mixing straws. Others can be controlled by chemical additives or by using different varieties of straw or mixing with scented biological materials such as herbs or woods eg. pine wood particles. Such material are totally 'green'environmentally and wholly decompose to useful organic nutrients.

The way the straw is processed will depend on the degree to which the liquids arc absorbed onto the particle. In all cases, the smaller the particle, the greater the surface area of the particle. In grinding technology, the straws are ripped apart to give varying sized particles. The ripping effect produces a rough surface which produces a large surface area. The way that the straw (including linseed soraw, hemp straws) and other highly cellular cellulose base materials are broken up will depend on the purpose to which the end product is intended to be used.

A large number of treatments are available for the preparation of these process straws. If. as an example only, the straw is to be utilised as an absorbent material for sophisticated uses, where the natural smell of the straw is not acceptable, such as feminine towels, baby nappies etc. , the straw can be treated chemically not only to remove the smell hut also to break up the cellular structure of the straws to increase the total surface area of the particles.

The product can be treated chemically to stenose the material so as t.o exclude all living organisms The straws can be chemically treated to remove the nature ! colour

of the straw. A useful chemical to achieve these results is sodium peroxide which is a strong oxidising agent. Many other oxidising agents exist for the above sterilising and bleaching effect Straws have a waxy type material on. the surface and this has the effect of forcing water (or some other liquid) to form spherical droplets of water that hold the shape because of the high surface tension. To reduce this effect, a suitable wetting agent can be used to coat the surface of the processed particles so that the rate of wetting of the particles is increased. It this way, the absorbency of the material becomes faster in effect. If the'wetting'agent is an organic solvent, the resultant material will be hydrophobic. Thus, it can selectively absorb organic spillages such as oil, petrol, paraffins etc.

The use of straw is very advantageous, not only because it is a naturally occurring material always available in -surpluS "quantities but, because, provided it is not subject to microbial activity, it has an extended stable structure that lasts for thousands of years. Straw does not decay readily In asepdc conditions.

v Straw in its various forms can have many applications For example, it can be used for decorative purposes. The technology which sandwiches straw particles between sheets of paper can also be extended to provide decorative materials that have a variety of straw particles embedded within the materials.

The above absorbent material should not only be limited to straw particles. For example, other absorbent materials such as vermiculite, perlite or other exfoliated inorganic materials, organically based hollow cellulose or plastic base materials can also be used Also. other organic materials can be used instead of paper. For example, cotton, silk, hemp, wool can all be used. Also, inorganic materials such as nylon could be used in place of paper.

The relationship between particle size and the surface are of the particles is well established (see, the earlier referenced~papers),. Fpr best results, i. e. for the maximum absorption of liquids, the particles need to be small. All small particles will absorb liquid not only because of the wetting effect, but the cellular fragments provide hollows which fill out, i e. provide the receptacle for the liquid in question. Therefore, it was not surprising that in recent experiments, when expanded polystyrene reclaimed material was sanded down to a fine powder, it absorbed large quantities of liquid. A wetting agent increases the rate of wetting.

All material with the cellular form manifest the same absorbent property. It is an interesting observation that the material with a high surface tension such as expanded polystyrene and the waxy coats on the surface of some cellulose materials act as hydrophobic gates. These gates repel water borne or water based liquids but absorb in preference hydrophobic liquids such as oils and fatty based liquids.

The use of surfactants is proven advantageous because it improves the rate at which particles are wetted. A cheap anionic or cationic or amphoteric surfactant is very effective at wetting the waxy and hydrophobic materials to reduce surface tension Frothing occurs when surfactant or soaps are added to water solution and an antifrothing agent is effective in reducing foaming of surfactant treated mixtures. Air vacuoles generally weaken the strength of the finished materials,

I. I- Preferably, the straw particles are dispersed in a suitable adhesive material or sandwiched between sheets of paper or other suitable containment material.

A further class of materials has been found where a light weight ceramic material is made by suspending an organic particle within the ceramic matrix.

Therefore, in a sixth aspect, the present invention provides a thermal1y in$ulating material which comprises a substantially homogeneous mixture of hydrocarbon particles suspended in a ceramic matrix.

It is more preferable for high temperturis work i. e. above 1200 C, if the ceramic matrix is made from cordierite clay, zirkonia clay or a suitable fine clay The material of the sixth aspect of the invention achieves its fire retardant properties by virtue of the fact that it has an inorganically based matrix. It does not crack during excessive heat stress because the bridges between one particle and another are extremely thin and expand g an even rate.

Because the bridges between the particles are so thin, they act as a physical barrier to conducted heat. Only small quantities of heat or electrical energy can cross the thin laminar of the matrix between the vacuoles. The process of conduction of heat energy across the laminar is slow. The effect'is increased by using materials, matrixes and fillers which are poor conductors of heat energy.

The resistance to thermal shock is obtained by reducing the quantity of the matrix material in the product. Failing of conventional fired clay materials once subjected to thermal shock occurs because of extreme stress imposed on the molecular bonds holding the material together. In conventional clay products, the sum of the forces in the material in the thermal shock conditions is sufficient to exceed the strength of the chemical bonds holding the material together-The chemical bonds breaks to signal the structural failure of the material. By reducing the quantity of the material in the product the magnitude of the forces is considerably reduced. By reducing the quantity of clay material in any given volume to a predetermined value, the sum of the expansive forces becomes insufficient to break the chemical bond binding the material matrix together and no shattering occurs. The highly aerated material is said to be able to tolerate thermal shocks.

The present invention according to a. sixth aspect is particularly of use in the lining of kilns. Aerated fire clay bricks can be made which require considerably less

heat energy to bring the furnace to the working temperature than conventional lining materials.

In addition to the supporting structure, fire clay supports and tripods and platforms can also be made of the aerated fired clay composites All these materials can have their mass reduced by anything up to 80% of the conventional items performing similar functions in kilns, The reduction in the quantity of heat energy required to raise kiln temperature to working levels are very considerable. In higher temperature clay products of about 12000C, exfoliated vermiculite can be used, The aerated ntaterial resultant from the burning of coal products in power stations such as the Floaters or Atmospheres, silicon oxide, glass, ceramic, perlite, can be used. C ! sy such as cordierite used for the manufacture of catalytic converters substrates or zirkon a silicon carbide or nitrate materials form good matrixes for high temperature applications.

The use of a ceramic or porcelain matrix can be applied to manufacture teapots, mugs, vegetable dishes, tureens or other containers designed to retain heat in the food industry or any similar use. The use can be extended to sheet materials for lining, coating, moulding to any shape for example hot water carrying pipes, furnace furniture and structure such as furnace supports and fire clay bricks

This technology can also be extended to metals. Therefore, in a seventh aspect, the present invention provides a material which comprises a substantially homogeneous mixture of particles suspended in a metal matrix. The particles can be inorganic or organic. In the case of organic particles, the material can be fabricated using metal vapour technology. Alternatively, the melal cowting is applied using metal suspensions and the like,

The present invention will now be explained in more detail by reference to the following non-limiting preferred embodiments and with reference to the accompanying drawings, in which Figure 1 shows a material in accordance with a second aspect of the present invention; Figure 2 shows another exampb of a material in accordance with a present invention ; Figure 3 shows two exfoliated particles which can be used to produce the present invention ; Figure 4 shows a material in a. ccordan c with the second aspect of the present invention with crust fonnation ; Figure 5 shows reclaimed particles which can be used as a particle in the present invention; Figure 6 shows a duct for electric cables or other services using a material in accordance with the present invention, Figure 7 shows end pieces for the duct shown in Figure 6, made of a material according to a second aspect of the invention ;, Figure 8 and Figure 9 show respective grommet sections of the duct shown in Figure 6 ;

Figure 10 shows a grommet suitable for use with the duct of Figure Figure 11 shows a grommet for assembly with the duct of Figure 12; Figure 12 shows the arrangement of plug grommet 29,31, 32, 34, 40,43 and 45 positioned at the forward end of a. service duct ; Figure 13 shows how two different size wires can be accommodated in a grommet ; Figure 14 shows the openings allowing the body section to be pulled apart ; Figure 15 illustrates the rear plug grommets corresponding to the arrangement of Figure 12 ; Figures 16 and 17 shows mirror images corresponding to the views of Figures 11 and 14; Figure 18 shows a further example of a grommet design ; Figures 19, 20 and 21 show details'of components of the grommet construction of Figure 18 in perspective, Figure 22 shows an example of a duct casing suitable for use with the duct of

Figure 6 that has dimensions standardised to a. standard building matenal e. g. brick size or its multiples ; Figure 23 shows how the duct casing of Figure 22 can be incorporated into a wall ;

Figure 24 shows how a plurality of ducts using a material according to the present invention may be incorporated into a wall.

Figure 25 shows two roughened pieces of paper with straw particles in

accordance with a aspect of the present invention ; . I I.

Figure 26 shows the two pieces of paper of figure 25 partially fanned ; and Figure 27 shows the two pieces of paper of figures 25 and 26 joined Figure 28 shows a plurality of electrical cables housed in a material according to a second aspect of the present invention; Figure 29 shows a steel girder which is coated with a material in accordance with the present invention ; Figure 30 shows a cooker hob which uses a material in accordance with the present invention as an insulator ; and Figure 31 shows a flotation vessel iraccordance with the present invention.

Figures 1 and 2 show particles 201 which are coated with a matrix 203 In Figure 1, the particles 201 were mixed with a bitumen based matrix 203 The particles-were mixed using a conventional mixer such as a paddle mixer or a worm screw type mixer. Both of these types of mixers aim coat all of the particles 201. The particles were mixed until it was observed that they were all coated. For this example, 100 litres water based bitumen was mixed with 980 titres of expanded polystyrene beads. rh volume of the finished product is almost a 100% expanded polystyrene 201.

The matrix 203 just coats the surface. Very little matrix 203 is located in the interparticulate spaces 205.

The exampiss shown in Figure 2 also use a bitumen matrix. However, here a larger volume of bitumen was used (compared to that discussed above) and a low melting point bitumen compound was used. The melting point of the bitumen compound is 80DC. Therefore, the matrix can be liquefied by heating it to above SO'C-

500 litres of viscous bitumen was mixed with 750 litres of expanded polystyrene. A solid end product was produced which had a homogeneous distribution of matrix and particles. The end product is ridged with little flexibility. However, in the slurry state, the mixture can be moulded to exactly the shape of the cavity or mould used. In contrast to Figure 1, the matrix 203 is seen to occupy the inter-particulate spaces 205.

About 250 litres of the matrix 203 is situated in the inter-particulare spaces 205 For this example, the size of the beads was between Imm and 5mm.

The above two examples have bean discussed in relation to bitumen. However, it would be appreciated by a person skilled in the art that it could be repeated using similar quantities of any suitable matrix discussed in this specification The quantity of the matrix used is CQntrol1d as a means of providing the propenies of the finished product. If the matrix is the largest component, the coating will be heavy and the properties of the matrix material will predominate,

Figure 3 shows two fibres 211 and 213. Many fabrics for clothing, household I furnishings etc are produced by weaving fibres which are made by extrusion processes In Figure 3a, fibre 211 has a controlled viscosity matrix which is mixed with the particles wirh a diameter of about I um ( (0. 5 m). The matrix and particle mixtures then extruded to form fibres. The particles here are exfoliated particles However, it is

thermal materials or flotation safety garments. The outer surface of fibre 211 has been teased to provide additional softness.

The fibre shown in Figure 3b is similar to that shown in Figure 3a However, fibre 213 has a smooth surface 215 as opposed to a teased surface 212 Figure 4 shows a "smart-type" material 221 which forms a crust 223 when it is subjected to extreme heat. The smart type material 221 has an organic elastomeric matrix 225 suspended in this matrix are exfoliated inorganic particles 227 such as perlite or vermiculite, When the material 221 is subjected to extreme heat eg, in a fire, the elastomeric matrix 225 oxidises and the particles 227 are released from the matrix 225- The released particles 227 form clumps of exfoliated material which stick together to form a low density heat retardant barrier or crust 223. The formation of such a crust 223 retards the ingress of heat into the deeper layers of the material 221. This has the effect of reducing the rate of damage to the body of the material. Adjacent areas of the material remain unaffected. The crust 223 is only formed in areas of the material where the heat intensity is high enough to oxidise the elastomeric matrix 225.

The structures shown in Figures 1 to 4 show perfectly round particles. Figure 5 shows a material where the particles are reclaimed particles 231. Reclaimed particles do not have a round shape. The diameter of such particles is taken to be the width of a particle. The matrix 233 coats the outside of these particles. In this particular example, no matrix is seen in the inter-particle spaces 235. See Fig I Figure 6 represents a schematic cross section of a duct for electric cabines or other services, Item I is the casing of the duct in any shape or form, 2 and 3 are organically based matrix prepared end pieces through which, pass the electric cables to traverse the space in the duct. Items 4,5 and 6 are electric cables or any other service traversing the space. The space 7 is filled with, a cement organic marerial with suspended polystyrene beads hereinafter referred to as "the crete mater al" Items 8 and

9 are vent holes for the egress ofpressur 'd.'Tcta nuter ! np lumped under

pressure via opening 10. Space 7 is full when the crete material emerges via 8 & 9 The crete material is allowed to set and the cavity is protected against fires migrating from one space via the cavity into the adjaC : l1tipace or room, Figure 7 represents a schematic arrangement of one of the two organically prepared end pieces 2,3 of Figure 1. The end pieces 1, 2,3 are made from an assembly of individual pieces which are so designed that holes 13, 14 and 15 through the substance of the end pieces 2,3 separate any suitable distance across the traversing section but ideally across the diameter of the section. The holes 13,14 and 15 can be any size shape or form and any number depending on the proposed use One of the sections has an open access hole at the bottom of the assembly for pumping the crete material type slurry into cavity 7, Figure 6. As the slurry fills up the space 7, being under pressure, it emerges out of the only openings in the section at the vent holes 8 and 9, see Figure 6. Figure 7 demonstrates the component via which the"slurries"are pumped into the ducts at hole 17. Hole 16 is the vent hole allowing the displaced air to

escape from the cavity space 7, Figure 1. Section 11 is the body of the plug and items 13, 14 & 15 are holes for services. Item 12 of Figure 7 is the grommet periphery abutting the cavity in the structure.

Figures 8 and 9 illustrate the four sections 18. 19, 23 and 24 in this unit which comprise the plug and allows explanations to the method of application-Figure 9

comprises the other of the two plug sections 23, 24 which does not have the injection hole in the bottom section of section 24. Installation of this design is initiated by placing section 24 into duct 1 of Figure 6. The electric cables are then situated in the holes 25. The section 23 is placed above the cables. The cables are thus sandwiched between section 23 and 24. Further cables are sandwiched between section 23 and 19 as section 19 is places above section 23 and pressed into position Services arc Hrmly "clamped"by the elastomeric properties ofthe matrix, in the holes 13, 14, 15 provided between sections 18, 19,23 and 24. The final'stage of installation is achieved by positioning the services into holes 20 and compressing the last piece 18 of this arrangement into the duct, see 1 of Figure All the cables are thus sandwiched in

between the pieces of the plug and because'the plug material is made from the organic material the compressed plug fonn a tight plug holding the services in place and separated from each other.

Provision is made for the non use of holes which might be surplice to need If plugs are made with more holes than is required, a small plug designed to block off the hole is inserted into the hole instead of the cable ! Once both ends of the plug are positioned, the cavity is pumped full of organic matrix material and the assembly is left to set.

A most effective fire egress system is established by the above arrangement.

Similar use can be applied, for gas or water or liquid tight plugs.

Modifications to the arrangement of end pieces and their components are possible. As an example, the forward plug end pieces (as shown in Figure 7), in addition to four or more members can be designed to have structural pieces complemented by any number of interchangeable"Crommets"that are designed with one or more holes through its substance to serve one or more of the services passing through it. The grommet is designed with a split section through the middle of its mass or however otherwise is the more convenient access for the service.

The grommet is basically a hinged gate type of structure that is designed ro open

along it's central axis to allow insertion of the services to be encased in the fire retardant material. As an example only Figure 14 illustrates a grommet 45 designed to accommodate only two services, The grommet 45 is split along it's axis 46 so that the two halves can open up like the pages of a book. The services are then inserted i1HO the holes and the two halves of the grommet closed to enclosed the service member The grommet 45 is then positioned in the plug assembly and the various members of the plug assembled to provide the arrangement in Figure 7. The plug forms a tight junction with services passing through the grommet substance to be tightly held in place Any

number of grommets can be provided and different grommets can be designed to have different sized holes of any shape or form. The grommets can be of the same circumventional dimension or they can be of different sizes. Grommets can be designed to be mirror images to provide symmetry in the alignment of services. A service passing through the front grommet emerges in the same line through the back plug grommet. The grommets can for ease of alignment and assembly have additional features. The provision of a tongue and groove arrangement so that as the individual members of the plug are assembled, they slot into the tongue and groove sections 10 sir in line within the opening and exit holes of the service duct.

The assembly of the forward and back plugs is similar. In Figure 12 the plug section 29 is positioned at the bottom of the containing service duct. Sections 31 and

34 are then placed in the perpendicular position and the grommets assembled with the services passing through the holes. Finally section 32 is forced into position to complete the assembly and form a tight junction'to close off the opening of the duct.

The procedure is repeated for the back plug (Figure 15).

The grommets are designed to accommodate services and in the case of electrical wiring the grommet in Figure 13 allows two different sized wires to be accommodated Holes 41 allow a tight fit for a given size and holes 39 and 40 allow for a larger wire or service to pass through the substance. The body of the grommet 38 is a one piece grommet that has slits along the central axes of the accommodating hole so that the sections of the grommet can be lifted open to allow positioning of services Figure 11 demonstrates a three section grommet with the sectioned component 42 separating the sections 43 and the third section.

Figure 14 illustrates the openings 46 and 47 that allows the body section 45 to be pulled apart to allow the positioning of services.

Figure 15 illustrates the back plug of the unit. Sections 49 to 52 comprise the mirror image of the front plug design. Grommets 57 in Figure 10, 58 Figure 16 and 59

in Figure 17 illustrate mirror image sections. that complement the grommets in the front plug. Item 30 in Figure 12 is a hole via which is injected the fire retardant the crete material or any of the other suitable fire. retardant materials which are preferred such as the mixtures of the organic and inorganic materials specified earlier. In both the front and the back plug there are bleeder holes, Figure 12, item 33 and Figure 15 item 56, that allow the displaced air to vent out of the duct. The cavity in between the plugs is pumped full of the fire retardant material.

The grommet design will be dictated by the dimensions and configurations of the duct designs. It is intended to provide a complete system for the prevention of fire egress form one compartment into another. The provision of specially designed ducts in c-operation with the service installation industry and in consideration of their requirements, might be optimised into one or multiples of ducts assembled into partitioning walls. The provision of the fire retardant"smart"organic matrix grommets and the Styrocrete will provide a permanent fire check at these points. A further example of grommet design is illustrated in Figure 18.

Styrocrete pumping access is achieved. via 61 and terminated when the pumped material of choice emerges under pressure from 58. Service containing grommet 62, 63, 64, 65,'66, 67 are arranged in any combination required by the service industries.

Three dimensional grommet presentation is demonstrated in Figures 19, 20, and 21 items 69,70 and 71 respectively, The duct casing can be of any thick ! 1ess,' shape or form, and can be made from any suitable material, metal, synthetic, or composite substances available to the industry. In Figure 22, and as an example only, a rectangular box shape 100 is illustrated that is designed to fit standard building material construction technology.

Figure 23 illustrates the rectangular metal box incorporated intn a walt buih of

, g blocks. Th (-. blor., ks iri-bui standard building btocks. The block's ! tr ? bu'lt according to standard regulations and a

box is installed at the desired level in the wall. Mortar 74, is used to build in the box as illustrated and the block 72, construction continued along and above service duct box.

The metal duct 73, accommodates the services passing from one compartment into another. The services are circumvented by the grommets 75 and 78, each as an example only, providing four opening 76, 79. The grommets open via slits e g, 77 and are assembled within the duct according to site requirements.

In Figure 23 the smaller grommet is established at the top of the duct and being separated at 80 from the lower grommet. Once the services are installed Styrocrete concept material of choice is pumped inro the duct via hole 81 and once the material emerges under pressure at 82 the compartment is full. The fire retardant material is allowed to set and the service will provide a. permanent fire check.

The designed ducts can be made to any specification required and where desirable a composition of ducts can be assembled.

I Figure 24 illustrates as an example only, a multiple arrangement of 6 ducts 83, 84, 85, 86, 87and 88, built into a wall. The use is similar to the above description as in Figure 18 but allows for many more services to-pass through the wall.

Figures 25,26 and 27 show an example of another embodiment of the present invention. Sheets of paper I and 2 are roughened on one side to release fibres of cellulose 3, Straw particles are sprinkled onto the surface and are trapped within the feltwork fibre 3. The straw particles 4, are trapped within the feltwork fibres 3 and interspersed with trapped air volumes 5.

Figure 26 demonstrates the compounding of materials into double sided sheets. n Sheets 1 and 2 are brought together to form a single sheet of material between which are trapped particles of the absorbent material. Figure 26 demonstrates the compiling of sheets 1 and 2, in trapping within the cellulose fibre 3, the straw particles 4 The

feltwork also creates a large number of air volumes S which are interspersed amongst the fibres Figure 27 demonstrates the completed article which in its various forms can act as an emergency mopping up product for spillages.

Figure 28 shows a plurality of electrical cables 301. The pluraliry of cables are incased in a smart material 303 (such as that described with reference to Figure 4), The particles used here contain an expandable substance such as an inert gas or water If the cable is exposed to extreme heat, the particles move to the surface (as explained with relation to figure 4). However, the panicles also release either the inert gas or water This provides a further barrier to the progress of the fire.

\. Figure 29 shows a steel girder 311 which is coated 313 by brush, trowel or spray technology with a smart material (as explained with reference to figure 4) Figure 30 shows a cooker hob 341. The hob is separated from the surface of the cooker 343 via a steel finishing member 345 and an insulator member 347 The

insulating member 347 is made from exfoliated inorganic particles in a ceramic clay, CD fire clay or calcium alumina cement matrix.

Figure 31 shows a flotation vessel 351. The flotation vessel has a carrying space 353 and two flotation members 355 and 357. Flotation chamber 355 and 357 are filled

with an organic matrix material such a bitumen which is mixed with expanded polystyrene particles, An additional flotation chamber 359 which is at the base Of The vessel can also be filled with the low intensity material if extra buoyancy is required Flotation vessel 351 can be used to carry passengers safely, manufacture of unsinkable rescue vessels, recreation boats, commercial applications whereby booms, buoys and other maritime equipment, displacement members for flotation strucwres etc

Low Density Materials The refinement of industrially scaled quantities continues and the results of the finished product analyses show that the mix i6 commercially valid.

In the commercial quantities regime one part high alumina cement is mixed with 3.2 parts of exfoliated clay (Fibo) and 2. 8 parts of brick or crushed volcanic ash (Basalt) or similar or other usable commercially available refractory grade materials were mixed in a paddle mixer for 90 seconds and just enough water added to produce a mix that was transferred into a block manufacturing machine. The machine produced building blocks of 440 215 100mm nominal dimensioned blocks that were allowed to set. Samples of these blocks were crushed at intervals, see enclosed graph, and the crushing strength recorded. The blocks were then transferred in a kiln heated to one thousand degrees centigrade and the blocks heated for 24 hours.

The above mix was made with refractory grade materials and was

seen to withstand high temperatures for a prolonged period. The ratio : 1 : 6 HAC Fondu : Mixed aggregate (low density) was seen to be suitable for the manufacture of the high temperature tolerating cements.

It was also confirmed by the above procedure that a similar mixture but using sand or limestone as the fines material component in the mix, was not suitable for high temperature tolerating building material. The chemistry of the limestone broke down and the building material failed in use. Similarly it was seen that the sand used was also unstable at high temperature. The chemistry of the sand molecules was unstable at high temperature and the material failed in use.

Building materials used for high temperatures therefore must use components all of which are capable of tolerating high heat stress, if the total material composition is to withstand high heat stress.

The tested technology therefore is well suited to tolerating high heat stress in whatever form it is composited. As an example only, the walls that are intended to be built using high heat tolerating building blocks using exfoliated backed clays mixed with crushed brick or vOlcanic'fine materials in the above ration, can be extended to producing similarly batched materials but made entirely from the fine grade of material, ie. a mixture of materials whose particle size is 3mm to dust in diameter.

Depending on the crushing strength of the finished product, the ratio of materials can be varied within certain parameters In all cases it is aimed in the specified technology to produce a mortar that is made from the sana ration of components as that used for the building bloc The intention is to produce materials that have similar coefficients of expansion so that as the structure is subjected to high heat stress all the components of the structure will expand and contract at a similar rate. This compatibility of materials will reduce the rate of cracking in any fire as the materials are subjected to heat stress.

As a further extension to the concept tha renders and plasterers used in conjunction with these blocks and mortars can also be made from a similar fines material so that the render also has high heat tolerating properties.

The number of products deaignod to tolarate high heat stress can be extended to provide a great number of building materials and as a further example only, pla9terboard can also be made from the above fines mix. In this casa the boards so produced will be used for permanent fire retardant check for partitions, lining of other materials or forming ceilings etc.

Test data is available to confirm that materials produced in this way tolerate high temperatures for prolonged periods. As an example only, a buiding block was heated for 24 hours, continuously, at 1000 C, and tested for structuarl integrety. The block did not suffer in any way because of exposure to the heat stres.

The crushing strength of these blocks is summarised in Graph 1.

Claims

Document : 864837 CLAIMS FOR DIVISIONAL APPLICATION:

1. A composition for forming a thermally insulating material, comprising: (a) a high temperature tolerating cement; and (b) a refractory material or a mixture thereof.

2. A composition according to claim 1, wherein components (a) and (b) are present in a weight ratio of about 1: 6.

3. A composition according to claim 1 or claim 2, wherein the high temperature tolerating cement is calcium aluminate cement.

4. A composition according to claim 1 or claim 2, wherein the refractory material is selected from the group consisting of fine clay, cordierite clay, zirconia clay, exfoliated clay, glass, ceramic, vermiculite, perlite, silicon carbide, nitrate material, basalt, brick, and mixtures thereof

5. A composition according to claim 4, wherein the refractory material includes an exfoliated clay.

6. A composition according to claim 5, wherein the refractory material comprises a mixture of an exfoliated clay and a component selected from the group consisting of basalt and brick.

7. A composition according to claim 6, comprising about 1 part by weight calcium aluminate cement, about 3.2 parts by weight of an exfoliated clay, and about 2.8 parts by weight of a component selected from the group consisting of basalt and brick.

8. A composition according to any preceding claim, wherein the particle size of the refractory material is 3mm or less.

9. A composition according to any preceding claim, formed into a block.

10. A method of making a thermally insulating material, comprising: (a) preparing a composition according to any one of claims 1 to 9; (b) optionally, forming the composition into a block; and (c) subjecting the composition or block to heating.

11. A method according to claim 10, wherein, in step (c), the composition or block is heated in a kiln.

12. A method according to claim 10 or claim 11, wherein, in step (c), the composition or block is heated to a temperature of about 1200 C.

13. A method according to any one of claims 10 to 12, wherein, in step (c), the composition or block is heated for about 24 hours.

14. A thermally insulating material obtainable according to the method according to any one of claims 10 to 13.

15. An article formed from the thermally insulating material of claim 14.

16. An article according to claim 15, selected from the group consisting of bricks, furnace furniture and structure, pipes and containers.

17. A composition for forming a thermally insulating material substantially as described and illustrated herein.

18. A method of making a thermally insulating material substantially as described and illustrated herein.

19. A thermally insulating material substantially as described and illustrated herein.

20. An article formed from a thermally insulating material, substantially as described and illustrated herein.