SEALANT

The present invention relates to a sealant and, in particular, to a flexible and compressible sealant.

In the mining industry, there is a need to (a) stop gasses from entering the work area from old workings or ribs and (b) to direct clean fresh air to the working space instead of it being dissipated in areas of the mine which do not require ventilation at present but which may at a later date require ventilation.

The control of air/gas flow is usually performed by constructing what are referred to in the industry as either a permanent or a temporary stopping, and overcasts. Temporary stoppings are used when either the areas must be opened up again for working at a later date or where there is only a short term requirement for air and gas control prior to the area being mined through.

Permanent stoppings are, as the name implies, intended to remain in place into the future and most frequently are used to seal off worked out areas of the mine. They are usually constructed of substantive materials such as concrete blocks, bricks or formed in place concrete and can be of various thicknesses.

Overca., s can be described as a method of constructing what would normally be a road intersection so that one roadway subsequently passes beneath the other. Walls are constructed to prevent the airflow in one roadway from intermingling with the air in the other roadway. These walls, while not being as substantial as those for permanent stoppings are usually more substantial than temporary stoppings. Overcasts can be subjected to the same stresses and forces as temporary and permanent stoppings while also being subject to much more passing traffic, and its resultant vibrations.

Ribs can be described as that part of the coal seam or strata which forms the wall of the tunnel or heading. This is normally solid and as such allows no air or gas movement. There are situations where through stress or

movement or faults the rib becomes porous, allowing movement of gas and/or air through the rib. To prevent or stop this, a sealant is applied to that section of the rib which has, or is likely to develop porosity. As with stoppings, the flexibility of this sealant product allows it to accommodate small cracks and the addition of a reinforcing agent allows the product to bridge large gaps. The ability of the product to build to a considerable thickness before slumping and adjust to accommodate drying shrinkage allows the applicator to fill or bridge cracks and gaps during application, particularly where a reinforcing supporting mesh is applied.

Both temporary and permanent stoppings and overcasts are subjected to considerable stresses due to the pressure applied to them by the weight of the rock and coal stratas above and to the side of the immediate area. These stresses, which come about by mining actions, can be transmitted over a distance and are considerable, in the order of tonnes. This causes not only roof movement but also floor heave and wall (rib) spall. The largest of these movements usually comes about through floor heave. When pressures are transmitted from the surrounding strata to the floor which, being the weakest point, can be pushed up into the roadway (drive or heading) .

Permanent stoppings, although constructed of more substantial materials, during their life can be subject to pressures and stresses greater than their compressive and tensile strength. Because of their rigid construction they therefore can crack due to movement of their surround caused by the pressures described above. Then cracks allow ingress or escape of gas and air.

Temporary stoppings are constructed from a variety of materials all essentially of a light weight and usually not capable of withstanding much stress or movement. The most common type consists of a frame to which is attached a variety of materials such as plasterboard, brattice cloth, conveyor belting, mild steel sheeting, expanded

metal lath, plywood, hession etc. However, other materials have and are being used. It has been past practice to coat these materials or surrounds with a cementitious/plaster product to seal any gaps around and within the structure. On setting these products essentially form a seal. Due to the normal rigidity of these structures and the sealant materials used in both permanent and temporary stopping, cracks occur which then permits ingress of gas or escape of air. Consequences of this can be one or all of:

1. danger to human life due to gas ingress (explositon/suffocation)

2. loss of control of ventilation air

3. high maintenance costs due to the repair of the damage or to completely reconstruct the stopping. To date, sealant products for mine application have been found to possess a multitude of side effects which can render the product unsuitable or reduce its useful life. In addition they may only be effective in adhering to a limited number of substrates. Some develop fine cracks due to stresses caused by shrinkage during drying or slight movement through air pressure fluctuations and movement of the surrounding strata. These cracks result in air leakages. Larger movements of the surrounding strata result in significant cracks which stay open due to the inelasticity or rigidity of the products.

Other products have been rejected because they either contain solvents or give off harmful gasses during application or emit large volume of highly toxic gasses if exposed to flame. However, other products:

(a) have gh weight and require substantive support,

(b) generc-ce heat due to chemical reactions which can cause spontaneous combustion within the product or with other substances,

(c) require solvents to wash down equipment or spills,

(d) are powdered products which require mixing on site with consequent dust exposure to applicators and

other workers and/or require cumbersome mixing equipment,

(e) can result in chemical burns from setting reactions (cement burn) ,

(f) are unable to bond to a wide range of substrates i.e. polypropylene, rubber, mild steel plate etc,

(g) during emergencies difficult to cut through or remove, (h) require frequent maintenance and often require complete replacement.

In one broad form the invention comprises a sealant adapted to form an air or gas stop comprising an emulsion of high molecular weight polymer, with or without plasticisers as required.

Preferably for mine use a flame retardant is used.

The high molecular weight polymer, commonly referred to as a latex can be the result of polymerizing acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, esters of acrylic and methacrylic acid, vinyl chloride, vinyladine chloride, butadiene, styrene, maleic, adipic, dibasic or fumaric acids and esters of the same and the like. The polymers can be homopolymers or copolymers of the above described monomers. Other polymers employed can be those based on naturally occurring isoprenes of the Hevea family which can be treated so as to cross link on removal of water or inclusion of various salts. These emulsion polymers are commonly available in different grades depending on the ultimate properties desired. They have in common the fact that they form films at room temperatures, alone or in the presence of plasticisers. The properties of the film depend on the chemical composition of the same.

Therefore as the embodiments of the present invention are flexible, compressible and extensible, they provide seals which can have the following properties: (a) Stretch to accommodate movement of the substrate and to bridge small cracks.

(b) With the addition of a reinforcing medium of greater strength than the bond of the product to the substrate, the product will hold its shape and bridge substantial gaps while still bonding to and being supported by the rest of the substrate.

(c) The ability to flex around a radius without cracking, allows the product to fold to accommodate a much smaller volume while maintaining integrity.

(d) By nature of the fillers and binders the ability to be able to crush (again allowing the product to conform to a smaller volume) while still maintaining integrity.

(e) By nature the binders and surfactants used, the ability adhering to a wide range of substrates which includes most polymers, wood, coal, metal, textiles, concrete, rock, glass, etc.

(f) By selection of binder and filler ratios, the various embodiments range from having no porosity to being highly porous.

(g) By incorporation of flame retarders and anti static agents, flame retardancy and anti static properties can be adjusted to meet the requirements of the various statutory authorities.

(h) By incorporation of various pigments, not only can flame resistance be increased but also colour can be used for visual enhancement e.g. white pigment or a colour can be incorporated to identify what form or type of substrate the embodiment has been coated onto or to signify the particular formulation of the coating itself.

(i) A foaming agent can be incorporated during manufacture or just prior to application such that:

1. air will be entrained during spray application or,

2. air can be whipped into the product by vigorous mixing just prior to application. This results in an embodiment which is extended so as to enable either a thicker coat to be applied before slumping or to give a greater coverage for a given weight of product.

(j) By incorporation of lightweight fillers and/or thixotropic agents, the embodiment is able to be formulated to give various applied thickness before slump, (k) By incorporation of fibrous fillers the product is able to bridge openings in the reinforcing medium during application as well as reinforcement of the sealant. (1) Initial set of the sealant can be accelerated if required by mixing into the sealant just prior to application an accelerator such as cement or plaster, as examples, or addition of the accelerator and mixing into the sealant inside the spray nozzle during application such as ammonium acetate or citric acid as examples. The preferred embodiment of the present invention provides a product which employes familiar techniques of application in the mining industry for the application of this flame retarded and anti-static, flexible, compressible and extensible material to a variety of substrates to form a coating or seal. Other objects and advantages of the invention will in part be obvious and in part appear hereinafter.

The flexibility of this embodiment also provides for new types of temporary stopping which will maintain a high degree of seal even when subjected to movement and floor heave, as follows:

1. Flexible substrate such as brattice cloth, suitably flame retarded woven or non woven fabric, mesh, rubber sheeting, etc. attached to a rope which is fixed to the ribs and roof by a variety of means. The rope being spring-loaded such that as a result of floor heave or roof or rib movement the spring extends or compresses, thus keeping the substrate in contact with the floor roof and ribs. Thus maintaining a seal in conjunction with the flexible sealant applied to the substrate and or around the edges. 2. Flexible substrate such as in 1. above, attached to the roof by means of fasteners or attached to a "w" strap and fastened to the ribs by pins, etc. driven into the coal/rock. The bottom edge not being fastened but can be lapped along the floor or weighted down by use of weights affixed to the material or pockets which are attached to the material which can be filled on site with suitable material such as rock and coal fragments. Thus keeping the bottom edge in contact with the floor and adjusting to and conforming to any changed volume as a result of movement such as floor heave maintaining a seal in conjunction with the flexible sealant applied to the substrate and/or around the edges.

3. Framework as is used in construction of existing stoppings which does not have a rigid floor support, leaving a gap of, for example, approximately one meter in the centre from the floor to the first rigid member of the structure. The lower section being covered by a flexible substrate as described in 1. above and the bottom edge kept in contact with the floor by means of methods described in 1. and 2. above.

4. In mines which are not subjected to floor heave or significant movement or in construction activities. Using a substrate as described in 1. above which can be fastened on all edges and thus form a seal in conjunction with the flexible sealant applied to the substrate and/or around the edges.

5. Flexible substrate such as in 1 above coated with flexible sealant and allowed to cure prior to installation. Such that the stopping is essentially prefabricated. This allows for rapid installation of a stopping or overcast with the majority of the sealant already cured and only requiring flexible sealant to be applied to the edges and joints for a complete seal on installation.

6. Flexible substrate such as in 1 above with designs as in 1 to 5 above but having a panel or panels where the joints in the flexible substrate are overlapped and fastened together at the overlaps with a resealable fastening system such as Velcro (R) or adhesive as examples. With a flexible sealant applied to the

substrate and around the edges. This allows the joints fastened with the resealable fastening system to burst open if subjected to sudden over-pressure caused by roof falls or blasting, thus releasing the pressure without destroying the structure. Resealing is easily achieved by pressing the edges with the resealable fastening system together and if required applying more sealant over the top of the joints.

The above 1 to 6 also can be incorporated in the construction of overcasts and can be used as such with the same benefits as described in 1 to 6 above.

It should be obvious that modification and alterations could be carried out to the above examples without departing from the spirit and scope of the present invention.

The following is a general description of variations in additives in embodiment of sealants of the present invention:

Suitable flame retardants are aluminium tri-hydrate, partly hydrated magnesium calcium carbonate, intumescent compounds and brominated or chlorinated chemical compounds used singularly or in combination depending upon the type of binder, the ratio of binder to filler and degree of flame retardation required.

The performance of the sealant is enhanced by the use of selected lightweight fillers for bulk, insulative properties, for flame retardancy and ability to build to thick coating (high build) without slumping. The active lightweight fillers are hollow microspheres either silica based or polymer based, perlite or vermiculite. When the sealant is required to have

high bulk, this can be achieved by the inclusion of flame retarded polystyrene beads in various proportions and size depending upon the bulk required. Other filler found beneficial to control viscosity or flame resistance and/or gap fillers include Kaolin, Bentonite, clay (ball or fireclay) , Gypsum, Mica, talc, silica, calcium carbonate, Magnesium carbonate, etc.

Pigments for colouring or whiteness to impart high reflection to reduce heat load are selected from titanium dioxide and barium sulphate. Pigments, when very high conductivity is required, are selected from the conductive carbon black. Pigments for colour are selected from inorganic or organic, either dispersed or non dispersed pigments suitable for the mediums and can be either of a fugitive or permanent nature. Antistatic performance can be enhanced by use of any of the propriety anti statics for the relative polymers, examples are the latrostat (Registered Trade Mark) and elactiv (Registered Trade Mark) ranges of anti-statics.

The combination of flame retardant agents and fillers are supported in a suspension with a protective agent and thus is in the form for blending in a binder, polymer resin latex, so that when the composition is dried and cured in place, a very useful seal is obtained which is durable, can flex and stretch, is suitably fire retarded and anti-static to meet with statutory approval. Will adhere to a wide variety of substrates and produce a seal which has no, to low porosity.

The incorporation of a suitable reinforcing mesh into the sealant during application, allows the product to bridge large

openings or to accommodate large cracks by restraining the sealant and allowing the bond to break between the substrate and the product in the region of high stress and movement thus bridging the crack while still adhering to and being supported by a substantial part of the substrate, thus maintaining an intact seal.

The flexibility of the sealant, which enables it to bend around a radius and which can be formulated, depending on the latex selected, to bend flat on itself, allows us to construct a new type of stopping which is not rigidly supported where it contacts the floor area and where the support medium is in itself flexible. When a floor heave results in considerable upward movement resulting in a much smaller area to be sealed, the sealant by folding or crushing, can accommodate the changed area while still maintaining its sealing properties.

When used to seal a flexible substrate, which has not been fixed to the floor, sudden over-pressure caused by roof falls or blasting will exceed the strength of the sealant. This allows the bottom edge to burst open, thus releasing the pressure, without destroying the structure of the stopping, which can occur with stoppings constructed from rigid materials. Resealing, when necessary, is achieved by pushing the substrate .back into place and applying more sealant to the edges.

The pigments, the supplementary fire retarding compoun' and antioxidants are first dispersed in liquid containing a wetting agent and an anti foam by adding them slowly to the liquid phase under strong agitation with a high speed, high

shear mixer. After addition of the solids is completed, the resultant dispersion is stabilised by adding a quantity of a protective agent such as carboxy methyl cellulose of selected molecular weight to achieve optimum viscosity and prevent the particles from settling. This is then transferred to a medium to low shear mixer where the polymer is added slowly to the mix and stirring is continued until uniformly mixed.

This is then transferred to a planetary or paddle or ribbon blender or any mixer suitable for mixing to paste consistency, the remainder of the fire retardant fillers are added slowly during mixing and allowed to uniformly mix. Then followed by the addition of lightweight and other fillers which are slowly added during mixing and allowed to uniformly mix.

The resultant mix is then tested for viscosity and hold up and adjusted accordingly by the addition of thicking agents or liquid as required. To this is then slowly added, as required, either foaming agents and/or chopped reinforcing fibres which are then folded in or dispersed using low speed to minimise air entrainment until uniformly mixed. The product is then placed in drums or pails.

Application of the sealant can be by any of the conventional pump spray mechanisms commonly employed for pumping grouts and sealants with the inclusion of a spray nozzle to spray the sealant onto the substrate and/or reinforcing material to the desired thickness. The sealant can be applied to the substrate and reinforcing medium by trowel in a similar manner to plaster or cement render. Application can also be by mechanical means such as when rotating spring loaded

fingers pick up the sealant from a container and throw the sealant onto the substrate. However applied, the sealant can be finished off if desired, using any of the methods commonly used in finishing off plaster or cement.

The sealant is then allowed to remain under the prevailing atmosphere conditions until it has set. The resultant material is flame retarded and anti static when tested using the commonly used flamability and anti static tests applied by the relevant authorities and flame retardancy and anti static is not lost after immersion in or exposure to running water over a period of time.

Description of Preferred Embodiments

The present invention utilises polymers commonly referred to as synthetic and natural lattices, and are commercially available materials. The synthetic lattices are obtained by homo or co-polymerisation of monomers of the general class.

R _χ - CH = CH - R ₂ where R.. and R _? can be the same or different and can be selected among ³ H, Cl, Br, CHJ-, Cn - Hm where n is 1 to 5 and M = 2 _n + 1, COOH, CONH ₂ , CN, CH = CH ₂ , CgH ₅ and the like.

The preferred synthetic monomers are alkyl esters of acrylic and methacrylic acids, acryl and methacryl amides, acrylonitrile, acrylic and methacrylic acids, maleic, adipic, dibasic or fumaric acids and alkyl esters of the same, vinyl and vinylidince chlorides, styrene and butadiene. Due to the infinite number of possible combinations we will class the polymers in the following groups:

(a) Acrylic lattices, mainly homo or co-polymers of alkyl esters of acrylic or methacrylic acid which can also contain acrylic or methacrylic acid, acrylonitrile, acrylamide, m-methylol acrylamide, vinyl and vinyladine chlorides and the like. The alkyl group of the esters can also contain hydroxyl groups. The presence of reactive groups, such as HO, CONH ₂ , COOH suggests the possibility of further cross linking leading to a higher molecular weight and a much more stable polymer. These types of polymers are referred to as cross-linking, self cross-linking or thermosetting lattices.

(b) Acrylonitrile lattices where the major ingredient is acrylonitrile which can be found as homo polymers or co-polymers as in (a) .

(c) Vinylchloride lattice where the major constitutuent is the monomer homopolymerised or co-polymerised as in (a) .

(d) Vinylidine chloride lattices.

(e) ABS (acrylonitrile-butadiene-styrene) lattices where these three monomers are the principal ingredients and can also be co-polymerised with other monomers as in (a) .

(f) SBR (Styrene-butadiene-rubber) lattices either carboxilated or not.

(g) Polymers obtained by the reaction of polyisocyanate or an aliphatic polyol which can be a polyether, a polyester or a polycaprolactone. The preferred polymer being an anionic aliphatic polyester polyurethane having a molecular weight in excess of 3,000 commonly referred to as a polyurethane.

The preferred natural polymers are those lattices produced by Hevea braziliensis but other sources are known to include goldenrod, kok-soghyz and parthenium agentatum. Essentially these latexes under destructive distillation yield among other products a hydrocarbon called isoprene and the resultant latex can be described as a linear polymer of isoprene with a variety of chemical end groups largely determined by the natural source of the product. By addition of various compounds, best known to the supplier of these lattices, these lattices can be, on drying, made to cross link and form films at room temperature which have properties ideally suited as the binder in this product.

The reason for blending these various polymers is to achieve polymers with varying film properties, although it is not a prerequisite that this be done as some individual polymers have shown suitable properties without blending.

Blending of various polymers products effects such as:

(a) Flexibility of the film which can vary from soft to hard and from tacky to dry. This parameter is measured by the glass transition temperature (TG) . One way of describing this is in ^* C and can range from -100 to +100°C. As a general rule the lower the TG the softer and more flexible, the film.

(b) Solvent swelling resistance. Polymers are known to swell when wetted with organic liquids. This property is improved by introducing cross linkable sites onto the molecule of the polymer or the swelling is used to impart greater flexibility and compressibility to the product.

(c) Film strength which can be altered by changing the molecular weight of the polymer or by the introduction of cross linkable sites which can be made to react by heat and/or catalysts.

(d) Adhesion of the film. The property is very important since the ability of the product to bond to a wide variety of substrates will greatly depend on it.

The preferred sealant is essentially air dry, self crosslinking and therefore a single pack product. It is part of this invention that catalysts or crosslinking agents can be added just prior to application to speed up the process of setting. There are many commercially available catalysts or crosslinking agents available each specific to the polymer or polymer combination selected. The polymer need not be in emulsion form, pure polymers or polymer in a non aqueous media can be utilised to produce a suitable sealant.

The preferred flame retardant fillers are aluminium tri hydrate, partly hydrated magnesium calcium carbonate, intumescent compounds and brominated or chlorinated organic chemical compounds either alone or in combination, depending upon the particular properties each of these impart to the sealant.

Aluminium tri hydrate produces a blanketing gas at a lower temperature and acts as a smoke depressant and ash promoter while the partly hydrated magnesium calcium carbonate continues to gas at more elevated temperatures by evolution of CO,,. Intumescence compounds are mixtures of catalysts carbonific materials with phosporous esterifiable sites and if

necessary a blowing agent. The catalyst decomposes with the application of heat to form phosphoric acid (such as ammonium polyphosphate melamine phosphate or polyphosphorylamide as examples). Most importantly it must decompose to yield high levels of phosphoric acid below the decomposition point of the carbonific material.

The phosphoric acid reacts with the carbonific material, examples of which can be carbohydrates, proteins or polyfunctional alcohols (such as starch, casein and pentaerythritol as examples) . The resultant ester then begins to decompose. The esterification releases water, then decomposition creates large volumes of carbon, more water, carbon monoxide, non flammable gases and more acid for esterification, creating a carbonaceous char.

The blowing agent when used decomposes, yielding large volumes of non-flammable gases causing the carbonaceous char to bubble and foam, forming a thick insulative mat. More than one blowing agent can be used to extend the foam. Lower temperature reacting agents are selected from amides and amines (such as dicyandiamide, urea, melamine and guanidine as examples) . At higher temperatures halogenated products form suitable reacting agents (such as chlorinated paraffins, rubbers and polymers) . Prefered components are ammonium polyphosphate, pentaerythritol melamine, chlorinated paraffin and poiyvinyl chloride.

Flame retardancy can be achieved or enhanced by use of halogenated and/or phosphorus bearing compounds and/or ammonium polyphosphates and/or magnesium hydroxide, and/or barium

metaborate monohydrate, etc.

In most cases outlined below the bromine compound as given which can be readily substituted by the chlorine compound.

(a) polybrominated benzenes

(b) Polybromo monoalkyl benzenes

(c) polybromo dialkyl benzenes

(d) polybrominated phenols

(e) polybrominated biphenyls

(f) polybrominated trerphenyls

(g) polybrominated analine

(h) polybrominated aromatic mono and polyacids anhydrides or esters (i) chlorinated rubbers (j) chlorinated paraffins (k) Bis hexachlorocyclopentadieno octane (Dechlorane +)

With the halogenated compounds there is utilised a synergist which reacts with the halogenated compounds at the flame temperatures inducing its decomposition and liberating a non inflammable gas which forms a blanket around the product displacing oxygen from the vicinity of the products thus impeding the oxidation process of combustion. These synergists are normally metallic oxides of the general formula.

Where Me can be Al, Ga, Si, Ge, As, Sb, Bi, Ti, Zr and the like and n is the volume of the metal in its oxidised state. Especially are the oxides of aluminium, germanium, antimony and titanium useful. It has been found that these oxides must be of the same fine particle size as the halogenated compounds.

The synergist is blended with the halogentated compound during the formulation of the product. The ratio of the halogenated compound to synergist has been found to be 3 to 20 parts of halogen to each part of metallic oxide preferably 4 to 6 parts to 1 part give satisfactory results.

It is part of the invention that used in combination with the above the partly hydrated magnesium calcium carbonate or magnesium carbonate or calcium carbonate reacts with acids produced by interaction between the halogen gases and water thus reducing noxious by-products associated with the use of halogenated compounds.

Reinforcing Medium used in conjunction with the sealant Several reinforcing mediums have been found to be successful in part and can be used singly or in combination.

These are:

1. Fibreglass fibres or carbon fibre, as scrim or leno weave or knitted of various constructions depending on the strength and mesh size for the particular application.

2. Polymer fibres and tapes as scrim, plain or leno weave or knitted of various construction depending upon the strength and mesh openings required for the particular application.

3. Polymer mesh either as extruded or stretched in one or both directions to draw or orientate the molecules to impart improved physical properties. Again a wide variety of weight and mesh openings are suitable depending on the strength and mesh size required for the

particular application.

4. PVC coated fibreglass or polyester fibre as scrim, leno or plain weave also in various weights and mesh openings suitable for the particular application.

5. Woven or welded metallic wire in various weights and mesh openings suitable for the application.

6. Non woven fibreglass or polymer products as a mat either heat welded or glued together in various densities and weights suitable for the particular application.

Polymers found suitable have been of the olefine group, poiyvinyl group, polyimide group, cellulose group, polyester group and polyamide group, either as homo or copolymers and as mono component or multi component filaments or tapes. Fibres of the cellulose group which are naturally occurring can also be used in point 2. above.

Any of the above which have been suitably treated so as to be flame retarded and reduce air permeability such as, Rheem (R) , Brattice cloth.

There are many commercially available fastening systems that can be used in conjunction with the sealant and reinforcing medium to:

(a) support and reinforce it where higher tear or burst strength than the sealant used on its own is required.

(b) act as a constraint to the sealant to enable the bond to the substrate to break when subjected to excessive movement. Thus allowing the sealant to remain intact and

bridge large cracks or openings while still being supported by the rest of the substrate.

(c) metallic or conductive reinforcing (carbon fibre) enables static charge to be more readily dissipated from the sealant.

(d) The reinforcing materials flexibility allows the sealant to fold or crush upon itself when subjected to excessive force or compression. Also this allows for a new type of stopping to be constructed which adjusts by folding or collapsing of the sealant and reinforcing to a smaller area or volume, or "pops" open around the edges if subjected to sudden over pressure without destruction of the stopping or overcast.

Reinforcing medium used within the sealant Where required the sealant can be reinforced by short lengths of various materials either incorporated during manufacture or mixed in just prior to application. As well as acting as a reinforcing medium, the sealant, when sprayed or trowelled onto a suitable reinforcing mesh, results in some of the fibres not passing through the mesh but laying across the opening, blocking the opening so that as a consequence, only a part of the product passed through the mesh and the remainder builds up on the surface of the mesh to give the required build.

Materials which can be incorporated in this sealant, during or after manufacture, are short lengths of cellulose fibres, carbon fibres, fibreglass, metal fibres and man made fibre. Metal fibre and conductive carbon fibres, by virtue of their conductivity, can also dissipate static electricity as

well as reinforce the sealant.

If it is needed to stabilize the product sufficiently against oxidative degredation during warehousing production, shipment and to protect it during use and to a very limited degree, act as a flame retardant, a range of anti oxidants are available. For example suitable types are those having a hindered phenol moiety which is the active functionability of the molecule such as the IRGANOX range from Ciba-Geigy and WINGSTAY from Goodyear. In the formulations used IRGANOX 565, 1024, 1520, 1010, 1035, 1076 and 1330 are effective, particularly used individually and in combination and also as protection against copper ions which can affect the stability of some of the polymers and physical properties of the product after application.

Pigments used as whiteners, inert fillers and/or colour, can be any of the dispersable pigments. Typical suitable examples are: Titanium dioxide, Zinc Oxide, Barytes, Diazo yellow, Dibromoanthanthron red, Phthalocyanine blue, Phthalocyanine green, Carbon black and red, yellow, black iron oxide and Chromium oxide green as examples.

Suitable emulsion stabilizers are used to protect a latex emulsion during manufacture. Suitable products are ethoxilates and sulphanates and alkyl polyethylene glycol either or esters such as the teric range from ICI or the Emulan range from BASF, as examples.

Suitable thickening agents are used to support and maintain the stability of the product during manufacture and subsequently to adjust the viscosity of the final product to allow the product to be applied as a thick coat without

slumping. These products can be either a mineral or organic product. Organic thickeners can be either cellulosic or associative or polymeric. Suitable thickeners have been found to be fumed silica, clays such as bentonite, hydroxy methyl cellulose (methocel) Carboxilated acrylic co-polymers, polyacrylates, blends of PEG esters and aluminium acetates as examples.

Suitable coalescing agents are used to reduce the film forming temperature of the polymers. Typical examples of agents used are Ethylene ether or Butyl ethers of diethylene glycol such as butyl isonol, 2,2 diethoxyacetophenone, tri methlpentandiol and triaryl phosphates as examples.

Suitable defoamers are utilized as processing aids and are added to reduce foaming during application when a high density non porous product is required. There are many commercially available defoamers on the market from which either short life or long life types are selected for use in this product.

Suitable dispersing agents are selected from those commercially available to assist with dispersing of pigments and fillers in the formulation.

It is a requirement for mine application that the product does not continue to glow for more than a short time after flame is removed from the product. If required the addition of borates to the product enables the product to meet the requirements of afterglow suppression.

Suitable plasticisers are incorporated to reduce the glass transition temperatures of the various polymers to

improve their flexibility and extensibility. A range of commercially available plasticisers are available. Of these those which are phosphate ester based or chlorinated, have been found to reduce flammability of the various polymers as well as improving their flexibility and extensibility.

The addition of Zinc phosphate or Calcium Zinc Molybdate or Zinc Oxide, alone or in combination, have been found to reduce smoke emissions. The use of Aluminium tri hydrate and/or magnesium hydroxy carbonate also have been found to reduce smoke emissions although that is not their prime roll in the product.

Suitable anti static agents include polyether ester - amides nonyl phenyl phosphates and alkali-metal salts of alkyl phosphates as examples. Many of these products have a dual role in being used also as dispersing agents, fire retardants and stabilising agents during manufacturing of the products.

Suitable compressive fillers are selected from glass or silica microballoons or spheres, flame retarded foamed styrene, perlite, vermiculite and phenolic or polymer microspheres. Use of these fillers allows the product to be both light in weight and also crush under pressure into a smaller volume. Flame retarding agents can be encapsulated into polymeric or wax spheres when those flame retardants are of such a nature as to be incompatible with other components in the formulation. This allows the incorporation of water soluble salts as flame retardants which would otherwise leach out of the product on exposure to water or incorporation salts or liquids which although suitable flame retarders would react with either the

binder or fillers.

Suitable inert fillers have been found to be one or more of the following: of various particle sizes depending upon the final properties of the product required; suitable gradings are selected and blended to give the desired packing density of the total filler content in the final product.

Barium sulphate, potassium aluminium silicate, magnesium silicate, calcium carbonate, hydrated aluminium silicate, hydrated calcium sulphate, silica sand, quartz flour, aluminium oxide, magnesium carbonate, calcium hydroxide, magnesium hydroxide, calcium phosphate.

Suitable foaming agents can be selected from a range of products commercially available exhibiting good foaming and bubble stability. Examples of suitable products are sulfated alkylphenononypoly - (ethyleneoxy) ethanol sodium or ammonium salts.

Internal Reinforcing Material Glass fibres chopped continuous strand or milled fibres strand length lmm to 12mm nominal of various diameters

0 to 5% w/w Cellulose fibres

1 to 3mm length nominal 0 to 1% w/w

Metal fibres filings or chopped wire of ferrous or non ferrous material - length lmm to 12mm nominal of various diameter

0 to 10% w/w Synthetic fibre staple (chopped continuous strand) strand length lmm to 18mm nominal of various diameter

0 to 5% w/w Pigments

Water dispersable pigments Titanium dioxide 0 - 30% w/w Zinc Oxide 0 - 10% w/w Other pigments for colour 0 - 5% w/w Stabilizers

Ethoxilates and Sulphonates 0 - 3% w/w Alkyl polyethylene glycol ether or ester 0 - 10% w/w Thickeners

Silicon dioxide 0 - 1% w/w Montmorillanite clay 0 - 5% w/w Hydroxy Methyl Cellulose 0 - 0.4% w/w Carboxilated Acrylic copolymers 0 - 5% w/w Modified Sodium Polyacrylate 0 - 5% w/w Coalescing Agents

Ethylene ether or Butyl ether of diethylene glycol 0 - 20% of polymer

Tri methylpentanediol 0 - 20% of polymer Defoamers

Emulsifiable hydrophobic silica type 0 - 0.3% w/w Paraffin oil based defoamer 0 - 0.3% w/w Silicon oil based defoamer 0 - 0.1% w/w

Dispersing Agents

Sodium salt of Polymeric Carboxylic acid 0 - 10% w/w

Salt of sodium polyacrylate 0 - 3% w/w

Sodium salt of napthelene formaldehyde sulphonate 0 - 0.3% w/w

Fluorinated alkyl quaternary 0 - 0.1% w/w

Afterglow Suppressant

Zinc Borate 0 - 5% w/w

Set Accelerators

Cement 0 - 20% w/w

Plaster 0 - 20% w/w

Ammonium Acetate 0 - 10% w/w

Citric Acid 0 - 10% w/w

Alum 0 - 10% w/w

Plasticisers

Alkyl Phenyl phosphate 0 - 20% of polymer w/w

Di butyl phthalate 0 - 20% of polymer w/w

Di octyl phthalate 0 - 20% of polymer w/w

Trichloro-ethyl phosphate 0 - 20% of polymer w/w

Zinc Ortho phosphate 0 - 20% of polymer w/w

Tri-methandiol 0 - 20% of polymer w/w

Chlorinated paraffin 0 - 20% of polymer w/w

Emulsified phosphate ester 0 - 20% of polymer w/w

Flame Retarders

Antimony trioxide 0 - 30% of polymer w/w

Poly halogenated materials 0 - 50% of polymer w/w

Magnesium hydroxy carbonate 0 - 60% w/w

Aluminium tri hydrate 0 - 60% w/w barium metaborate monohydrate 0 - 30% w/w

Chlorinated Paraffin or rubber 0 - 50% w/w

Red phosphorus 0 - 30% w/w

Magnesium oxychloride 0 - 50% w/w

Ammonium polyphosphate 0 - 50% of polymer

Melamine phosphate 0 - 50% of polymer

Polyphosphorylamide 0 - 50% of polymer

Carbonific Materials

Carbohydrates, protein or polyfunctional alcohol 0 - 25% e.g. pentaerythritol 0 - 25%

Blowing Agents

Urea 0 - 25%

Dicyandiamide 0 - 25%

Melamine 0 - 25%

Guanidine 0 - 25%

Chlorinated Paraffin 0 - 25%

Smoke Suppressant

Zinc Phosphate 0 - 5% w/w

Calcium Zinc Molybdate 0 - 10% w/w

Zinc Oxide 0 - 10% w/w

Anti Static Agents

Carbon Black (conductive) 0 - 45% w/w

Elective 0 - 5%

Latrostat 0 - 5%

Compressible Fillers

Glass or silican microballoons (spheres) 0 - 50% w/w

Flame retarded foamed styrene (0.5-3mm) 0 - 50% w/w

Perlite 0 - 30% w/w

Vermiculite 0 - 20% w/w

Polymer microspheres 0 - 30% w/w

Inert Fillers

Barium Sulphate 0 - 50% w/w

Potassium Aluminium Silicate 0 - 50% w/w

Magnesium Silicate 0 - 50% w/w

Calcium Carbonate 0 - 50% w/w

Hydrated Aluminium Silicate 0 - 50% w/w

Aluminium tri phosphate 0 - 50% w/w

Silica 0 - 50% w/w

Hydrated calcium sulphate 0 - 50% w/w

Quartz flour 0 - 50% w/w

Fly ash 0 - 50% w/w

Anti Oxidants and Metal Deactivators

Hindered phenol moiety complexes 0 - 2% w/w

Chealating acent 0 - 0.1% w/w

Foaming Agents

Sulfated alkylphenonoxypoly (ethyleneoxy) ethanol as sodium or ammonium salt 0 - 5% w/w

Binders

Used individually or in combination 10 - 80%

Following are some examples of formulations of sealants in accordance with embodiments of the present invention which have been found to be acceptable as a sealant in mining areas. EXAMPLE 1

¹ 0 - 20% of a S latex as an aquenous dispersion having 50-67% lids. 16 - 35% of isoprene latex as an aqueous dispersion having 50 - 65% solids.

20 - 35% of glass or silica microballoons (spheres) having a particle size ranging from 5 to 300 microns.

5 - 30% water

0.2 - 10% dispersing agent (sodium salt of polymeric carboxylic acid)

25 - 45% of aluminium tri hydrate having a particle size ranging from 5 to 300 microns.

2 - 10% of hydrated aluminium silicate or magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns

2 - 5% of glass fibres 3 - 12mm length

0.1 - 03% defoamer

1 - 2% hindered phenol moiety complex (antioxidant)

The following formulation was produced and tested.

10% of a SBR latex as an aqueous dispersion having 50-67% solids.

22% of isoprene latex as an aqueous dispersion having 50-65% solids.

20% of glass or silica microballoons (spheres) having a paticle size ranging from 5 to 300 microns.

5% water.

2.8% dispersing agent (sodium salt of polymeric carboxylic acid) .

35% of aluminium tri hydrate having a particle size ranging from 5 to 300 microns.

2% of hydrated aluminium silicate or magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns.

2% of glass fibres 3 - 12mm length.

0 .2% defoamer .

1% hindered phenol moiety complex (antioxidant) .

On curing will give an extension before break of a minimum of

25% and fold over a 25mm bar without breaking through while meeting NCB specification 245:1985. Fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 2

20 - 52% of isoprene latex as an aqueous dispersion having 50 -

65% solids content.

15 - 30% of glass or silica microballoons having a particle size ranging from 150 to 300 microns.

10 - 20% water.

2 - 10% of glass or silica microballoons having a particle size ranging from 30 to 300 microns.

0.2 - 10% dispersing agent (sodium salt of polymeric carboxylic acid) .

15 - 30% of aluminium tri hydrate having a particle size range of 50 to 300 microns.

7 - 15% of aluminium tri hydrate having a particle size range of 0.1 to 5 micron:..

1 - 10% of hydrated aluminium silicate or magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns.

0.1 - 0.3% defoamer.

1 - 2% hindered phenol moiety complex (antioxidant).

The following formulation was produced and tested:

26% of isoprene latex as an aqueous dispersion having 50-65% solids content.

20% of glass or silica microballoons having a particle size ranging from 150 to 300 microns.

12% water.

2% of glass or silica microballoons having a particle size ranging from 30 to 300 microns.

1.9% dispersing agent (sodium salt of polymeric carboxylic acid) .

25% of aluminium tri hydrate having a particle size range of 50 to 300 microns.

10% of aluminium tri hydrate having a particle size range of

0.1 to 5 microns.

2% of hydrated aluminium silicate or magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns.

0.1% defoamer.

1% hindered phenol moiety complex (antioxidant) .

On curing will give an extension before break of minimum of 25% and fold over a 25mm bar without breaking through while meeting

NCB specification 245 - 1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 3

20 - 55% SBR latex as an aqueous dispersion having a 50 - 65% solids content.

15 - 30% of glass or silica microballoons having a particle size ranging from 30 to 300 microns.

10 - 20% water.

0.2 - 10% dispersing agent.

20 - 45% aluminium tri hydrate having a particle size range of

3 to 300 microns.

0.1 - 0.3% defoamer.

1 - 2% hindered phenol moiety complex antioxidant.

The following formulation was produced and tested.

28% SBR latex as an aqueous dispersion having a 50-65% solids content.

22% of glass or silica microballoons having a particle size ranging from 30 to 3000 microns.

12% water.

1.8% dispersing agent.

35% aluminium tri hydrate having a particle size range of 3 to

300 microns.

0.2* defoamer.

1% hindered phenol moiety complex antioxidant.

On curing will give an extension before break of a minimum of

25% and fold over a 25mm bar without breaking through while meeting NCB specification 245. 1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 4

40 - 89% vinyl chloride or vinyldine chloride as a liquid aqueous dispersion having 50 to 65% solids.

0 - 10% mixed phosphate ester as plasticiser on latex volume or chlorinated paraffin as a plasticiser on latex volume.

0 - 5% titanium oxide.

0 - 5% antimony trioxide.

0 - 5% zinc borate.

10 - 30% of glass or silica microballoon having a particle size

ranging from 30 to 300 microns.

0.2 - 10% dispersing agent.

0 - 30% aluminium tri hydrate having a particle size ranging from 30 to 300 microns

0.1 - 2% defoamer.

0 - 10% hydrated aluminium silicate or magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns.

The following formulation was produced and tested.

45% vinyl chloride or vinyldine chloride as a liquid aqueous dispersion having 50-65% solids.

5% mixed phosphate ester as plasticiser on latex volume or chlorinated paraffin as a plasticiser on latex volume.

2.9% anti static agent (e.g. Elective TA) .

0.5% titanium oxide.

5% antimony trioxide.

5% zinc borate.

15% of glass or silica microballoon having a particle size ranging from 30 to 300 microns.

1.4% dispersing agent.

20% aluminium tri hydrate having a particle size ranging from

30 to 300 microns.

0.2% defoamer.

On curing will give an extension before break of a minimum of

25% and fold over a 25mm bar without breaking through while meeting NCB specifications 245.1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 5

40 - 42% acrylic styrene co-polymer as a liquid aqueous dispersion having a 50% solids content.

10 - 20% plasticiser.

0.5 - 1% titanium dioxide.

0.1 - 0.5% stabilizer (alkyl polyethylene glycol ether/ester).

1.0 - 10% dispersing agent (sodium salt of a polymeric carboxylic acid) .

0.1 - 0.5% defoamer (emulsifiable hydrophobic silica type).

5 - 10% antimony trioxide (micro dispersed) .

20 - 35% aluminium tri hydrate 0.5 to 20 microns.

15 - 25% glass or silica microballoons (spheres) having a particle size ranging from 5 to 300 microns.

The following formulation was produced and tested.

41% acrylic styrene co-polymer as a liquid aqueous dispersion having a 50% solids content.

10% plasticiser.

0.5% titanium dioxide.

3.3% stabilizer (alkyl polyethylene glycol ether/ester) .

3% dispersion agent (sodium salt of a polymeric carbonxyllic acid) .

0.2% defoamer (emulsifiable hydrophobic silica type).

10% antimony trioxide (micro dispersed) .

20% aluminium tri hydrate 0.5 to 20 microns.

15% glass or silica r croballoons (spheres) having a particle size ranging from 5 to 300 microns.

On curing will give an extension before break of a minimum of

25% and fold over a 25mm bar without breaking through while

meeting NCB specification 245.1985 fire and electric resistance properties of supported and unsupported sheeting.

EXAMPLE 6

Acrylic co-polymer as a liquid aqueous dispersion having a 54 -

56% solids content.

20 - 30% glass or silica microballoons (spheres) having a particle size ranging from 5 to 300 microns.

10 - 15% water.

0.2 - 10% dispersing agent (sodium salt of polymeric carboxyllic acid) .

25 - 45% of aluminium tri hydrate having a particle size ranging from 5 to 300 microns.

0 - 20% of magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns.

0 - 10% mixed phosphate esters as plasticisers on latex volume.

0 - 5% anti static agent

0.1 - 2% defoamers.

The following formulation was produced and tested.

34% acrylic co-polymer as a liquid aqueous dispersion having a

54-56% solids content.

20% glass or silica microballoons (spheres) having a particle size ranging from 5 to 300 microns.

10% water.

0.8% dispersing agent (sodium salt of polymeric carboxyllic acid) .

25% of aluminium tri hydrate having a particle size ranging from 5 to 300 microns.

2% of magnesium hydroxy carbonate having a particle size ranging from 0.3 to 300 microns.

5% mixed phosphate esters as plasticisers on latex volume.

3% anti static agent.

0.2% defoamers.

On curing will give an extension before break of a minimum of

25% and bend over a 25mm bar without breaking through while meeting NCB specification 245.1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 7

21% of Isoprene latex as an aqueous dispersion having 50-65% solids content.

25% of glass or silica microballoons having a particle size ranging from 150 to 300 microns.

11% of water.

0.2% of dispersing agent (sodium salt of polymeric carboxyllic acid) .

42% of aluminium tri hydrate having a particle size range of

0.1 to 300 microns.

0.8% of anti static agent (e.g. Elective TA) .

On curing will given an extension before break of a minimum of

25% and fold over a 25mm bar without breaking through while meeting NCB specification 245.1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 8

18% of Isoprene latex as an aqueous dispersion having 50-65%

solids content.

18% of glass or silica microballoons having a particle size ranging from 150 to 300 microns.

21% of calcium carbonate having a particle size ranging from 1 to 300 microns.

30% of aluminium tri hydrate having a particle size ranging from 0.1 to 300 microns.

12% of water.

0.7% of dispersing agent (sodium salt of polymeric carboxyllic acid) .

0.3% of thickening agent (modified sodium polyacrylate).

On curing will give an extension before break of a minimum of

25% and fold over 25mm bar without breaking through while meeting NCB specification 245.1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 9

24% of acrylic co-polymer as a liquid aqueous dispersion having

54-56% solids content.

19% of glass or silico microballoons having a particle size ranging from 50 to 300 microns.

8% of water.

41% of aluminium try hydrate having a particle size range of

0.1 to 300 microns.

2.9% of plasticiser (chlorinated parrafin) .

0.7% of dispersing agent (sodium salt of polymeric carboxyllic acid) .

1.2% of coalescing agent (butyl ether of diethylene glycol).

1.0% of thickening agent (modified sodium polyacrylate).

0.2% of defoamer.

2.0% of anti static (e.g. Elective TA) .

On curing will give an extension before break of a minimum of

25% and fold over a 25mm bar without breaking through while meeting NCB specification 245.1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 10

55% of vinyl chloride as a liquid aqueous dispersion having

50-65% solids.

42% of hydrated aluminium silicate having a particle size ranging from 0.1 to 500 microns.

1.3% of thickener (e.g. modified sodium polyacrylate).

1.7% of anti static agent (e.g. Elective TA) .

On curing will give an extension before break of a minimum of

25% and fold over 25mm bar without breaking through, while meeting NCB specification 245.1985 fire and electrical resistance properties of supported and unsupported sheeting.

EXAMPLE 11

22.7% of isoprene latex as an aqueous dispersion having 55-65% solids content

9.9% of water

1.5% thickening agent (modified sodium polyacrylate)

16.4% glass or silica microballoons having a particle size ranging from 150 to 300 microns.

37.9% of aluminium tri hydrate having a particle size range of

0.1 to 300 microns.

10.7% of calcium carbonate having a particle size ranging from 1 to 300 microns.

0.5% triethanolamine (plasticiser)

0.4% of dispersing agent (sodium salt of polymeric carboxyllic acid)

On curing will give an extension before break of a minimum of 25% and bend over a 25mm bar without breaking through while meeting NCB specification 245.1981 fire and electrical resistance properties of supported and unsupported sheeting. EXAMPLE 12

26.5% vinylidine chloride acrylic co-polymer having between 55-65% solids content 1.5% butyl di glycol acetate 22.4% ammonium polyphosphate 8.9% pentaerythritol

0.5% hexa menta phosphate (dispersing agent) 0.5% dispersing agent (Oraton 731 (r)) 15% of water

4.7% calcium carbonate having a particle size range from 1 to 300 microns

15% glass or silica microballoons or perlite having a particle size range from 5 to 300 microns

5% of thickening agent (modified sodium polyacrylate) On curing will give an extension before break of a minimum of 25% and bend over a 25mm bar without breaking through while meeting NCB specification 245.1981 fire and electrical resistance properties of supported and unsupported sheeting. It should be obvious that modifications and alterations could

be carried out to the above examples without departing from the spirit and scope of the present invention.