WO2019135711A1

WO2019135711A1 - A fire extinguishing formulation for dry powder fire-extinguishers and method of producing the formulation

Info

Publication number: WO2019135711A1
Application number: PCT/SG2019/050003
Authority: WO
Inventors: Hong Yan; Huining ZENG; Tao TANG
Original assignee: Agency For Science, Technology And Research
Priority date: 2018-01-03
Filing date: 2019-01-03
Publication date: 2019-07-11

Abstract

The present disclosure provides for a formulation for use in a dry powder fire extinguisher. The formulation comprises a carrier fluid and a fire-retardant intumescent silicate material disposed in the carrier fluid, wherein the fire-retardant material comprises water glass and colloidal silica, wherein the water glass and the colloidal silica are different materials. The present disclosure also provides for a fire extinguishing composition comprising the formulation for use in a dry powder fire extinguisher. The present disclosure further provides for a method of producing the formulation. The method comprises providing a liquid mixture comprising mixing colloidal silica and water glass to form a fire-retardant intumescent silicate material in a liquid mixture, wherein the water glass and the colloidal silica are different materials, drying the liquid mixture to obtain the fire-retardant intumescent silicate material, and disposing the fire-retardant intumescent silicate material in a carrier fluid to form the formulation.

Description

A FIRE EXTINGUISHING FORMULATION FOR DRY POWDER FIRE- EXTINGUISHERS AND METHOD OF PRODUCING THE FORMULATION

Cross-Reference To Related Application

[0001] This application claims the benefit of priority of Singapore Patent Application

No. 10201800057S, filed on 3 January 2018, the content of it being hereby incorporated by reference in its entirety for all purposes.

Technical Field

[0002] The present disclosure relates to a formulation for use in a dry powder fire extinguisher. The present disclosure also relates to a method of producing such a formulation.

Background

[0003] A fire extinguisher is a fire protection device used to extinguish or control smaller size fires, often in emergency situations. It is not intended for use in an out-of- control fire situation but is more suitable for emergency usage to prevent the spreading of the fire. The fire extinguisher is an important fire protection device for use at the front line of firefighting, as it helps to eliminate the spread of small fires into uncontrollable ones that may result in loss of human lives and assets.

[0004] There are various types of fire extinguisher, e.g. dry powder, carbon dioxide, water foam, etc., as different types of fire require different fire extinguishing agent to douse the fire, and using an inappropriate fire extinguishing agent may increase intensity of the fire. As an example, fires may be classified into classes A to F in Asia and FIG. 1 shows this. FIG. 1 also describes the cause for each fire and methods to extinguish each class of fire. Among the different types of fire extinguisher, dry powder fire extinguisher is an excellent choice in many circumstances as the extinguishing medium in this type of fire extinguisher is dry, which in turn allows for use in warehouses, factories, and other areas where wet types of extinguishing medium, such as water or foam, need to be avoided to minimize damage to goods and items (e.g. paper documentation). [0005] The dry powder works by forming a barrier layer on a hot surface it comes into contact with, which causes the powder particles to swell, and the barrier layer blocks out oxygen, thereby quenching the fire. However, there may be disadvantages with dry powder extinguishers. When using dry powder fire extinguishers, the dry powder may generate a dense powder cloud that reduces visibility of firefighters, and this impairs judgement on the powder’s effectiveness for extinguishing a fire or even jeopardize escape in a fire. The dry powder components may be toxic, and if inhaled, may lead to irritation of the eyes, skin, respiratory system, or even damage organs. Moreover, the dry powder has to remain in the atmosphere above the fuel in order to be effective for quenching fires. This, however, renders the dry powder susceptible to wind dispersal, which may give rise to dangerous rapid re-ignition of the fuel, and the clean-up process may become problematic after use. Use of the dry powder may result in a messy residue that may be corrosive, and due to fineness of the residue, it may also be abrasive. The abrasive powder residues may damage sensitive electronic equipment, such as circuit boards, computers, production machinery, etc. As the powder particles may damage such equipments, their removal is needed. Examples of a dry powder component, which may give rise to some or all of such adverse effects, include ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate.

[0006] Ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate are used as a dry chemical agent stored under pressure in a fire extinguisher. They tend to start decomposing at 240°C to form ammonia and phosphoric acid. The phosphoric acid acts as an acidic catalyst in the dehydration of carbon-based poly-alcohols, such as cellulose in wood. The phosphoric acid reacts with alcohol groups to form heat-unstable phosphate esters, which decompose to release carbon dioxide and regenerate the phosphoric acid. In the gaseous phase, the released carbon dioxide, which is non-flammable, dilutes the oxygen in air and the flammable decomposition products of the material that is burned, thereby helping to extinguish the fire. When the released carbon dioxide reacts and converts to a condensed phase, it may become a carbonaceous char that coats a material in a fire. The char shields, for example, any underlying material from reacting with oxygen and degrading due to the radiant heat from a fire. Despite this, phosphoric acid is extremely corrosive to ferrous metal and alloys, and may attack certain plastics, rubbers and coatings, which further damages items in a fire. Phosphoric acid may also be produced when ammonium phosphate, monoammonium phosphate, or ammonium polyphosphate, undergoes hydrolysis. It is difficult to dispose off ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate after use, as they are not easily nor conveniently separated from the superhydrophobic carrier medium of the fire extinguishing agent.

[0007] Nevertheless, as dry powder fire extinguishers are more suitable and commonly used in various circumstances, there is a need to provide for a solution that ameliorates one or more of the limitations associated with dry powder fire extinguishers as mentioned above.

Summary

[0008] In a first aspect, there is provided for a formulation for use in a dry powder fire extinguisher, the formulation comprising:

a carrier fluid; and

a fire-retardant intumescent silicate material disposed in the carrier fluid, wherein the fire-retardant intumescent silicate material comprises water glass and colloidal silica, wherein the water glass and the colloidal silica are different materials.

[0009] In another aspect, there is provided for a fire extinguishing composition comprising the formulation described in the first aspect for use in a dry powder fire extinguisher.

[0010] In another aspect, there is provided for a method of producing the formulation described in the first aspect, the method comprising:

mixing colloidal silica and water glass to form a fire-retardant intumescent silicate material in a liquid mixture, wherein the water glass and the colloidal silica are different materials;

drying the liquid mixture to obtain the fire-retardant intumescent silicate material; and

disposing the fire-retardant intumescent silicate material in a carrier fluid to form the formulation. Brief Description of the Drawings

[0011] The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present disclosure are described with reference to the following drawings, in which:

[0012] FIG. 1 shows a table indicating the causes of different classes of fire and methods to extinguish the different classes of fire.

[0013] FIG. 2 shows the thermogravimetric analysis of a fire-retardant silicate particle based on one of the embodiments disclosed herein, wherein the fire-retardant silicate particle comprises water glass and colloidal silica.

[0014] FIG. 3 shows the infra-red results of a fire-retardant silicate particle based on one of the embodiments disclosed herein, wherein the fire-retardant silicate particle comprises water glass and colloidal silica. Detailed Description

[0015] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practised.

[0016] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0017] Various embodiments of the first aspect relate to a formulation for use in a dry powder fire extinguisher. Various embodiments of the present disclosure also relate to a fire extinguishing composition comprising the formulation described in the first aspect for use in a dry powder fire extinguishing composition and a method of producing the formulation described in the first aspect.

[0018] The present formulation comprises a carrier fluid and a fire-retardant intumescent silicate material disposed in the carrier fluid, wherein the fire-retardant intumescent silicate material comprises water glass and colloidal silica, wherein the water glass and the colloidal silica are different materials.

[0019] The expression“carrier fluid” used herein refers to a substance that aids in the discharge and dispersal of the fire-retardant material from a dry powder fire extinguisher. The substance is termed a“carrier fluid” as it is storable as a pressurized liquid in a fire extinguisher and is convertible to a gas when it is discharged into the atmosphere from the fire extinguisher. The pressurized carrier fluid converts to a gas as a result of the difference in pressure between the atmosphere and the pressure at which the carrier fluid is stored in the extinguisher. In a fire extinguisher, the carrier fluid is compressed under pressure to occupy a smaller volume, which reduces the distance between the molecules of the carrier fluid and causes the carrier fluid molecules to be bound tightly to each other, thereby forming a pressurized liquid. When the pressurized liquid is discharged to atmosphere, the pressure of the atmosphere is much lesser, and this allows the carrier fluid molecules to move apart and increase the distance between each other, thereby forming a gas.

[0020] The carrier fluid may help to suppress fire as the gas is able to carry and disperse the fire-retardant material onto burning objects to quench the fire. The carrier fluid may have other advantages depending on the type of carrier fluid used. For example, in embodiments wherein the carrier fluid has no reactivity with ozone, use of the carrier fluid may not result in depletion of ozone nor harm the environment. In various embodiments, the carrier fluid is non-toxic and does not release any toxic substance when it is subjected to heat from a fire. In various embodiments, the carrier fluid may have low or zero electrical conductivity and be compatible for protecting electrical equipment when quenching fires, such that the carrier fluid does not cause electrical short circuits when electrical equipment are restarted for operation after the fire is put out. The carrier fluid, when discharged from a dry powder fire extinguisher, may not form any residue that affects visibility and hinders rescue operations in a fire.

[0021] Apart from the carrier fluid, the fire-retardant intumescent silicate material may also help to suppress fires. The fire-retardant intumescent silicate material may be disposed onto a burning or heated surface, forming a barrier layer that deprives the surface of oxygen, which in turn prevents a fire. The fire-retardant intumescent silicate material disclosed herein are advantageous over ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate, as the water glass and colloidal silica comprised therein do not form corrosive acids, and have better thermal resistance. Even though ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate are traditionally used to form dry powder compositions for extinguishing fires, they decompose at 240°C or undergo hydrolysis to form phosphoric acid, which is corrosive and can damage metals and even plastics. The fire-retardant intumescent silicate material comprising water glass and colloidal silica disclosed herein, in contrast, does not produce any corrosive acids and can withstand temperatures of up to 800°C. With a higher thermal resistance, the barrier layer formed by the fire- retardant intumescent silicate material may last longer, and this may prevent a surface from re-ignition until the fire is put out completely.

[0022] In addition to the above, the water glass and colloidal silica comprised in the fire-retardant intumescent silicate material disclosed herein are non-toxic and have low thermal conductivity. This means that the use of the fire-retardant intumescent silicate material does not cause any adverse or harmful effects on humans, such as irritation of eyes or skin, or breathing difficulties when inhaled, and the low thermal conductivity prevents a fire from spreading as it impedes heat from being transmitted.

[0023] Moreover, the intumescent silicate material is heavier as compared to conventional powder compositions for extinguishing fires comprising ammonium phosphate, monoammonium phosphate, or ammonium polyphosphate blended with amorphous silica, and this renders the cleaning up process easier as the intumescent silicate particles are less susceptible to dispersal by wind, which ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate suffer from and get carried further to areas not affected by a fire. Despite being heavier, the intumescent silicate material is nevertheless light enough to be dispersed by the carrier fluid to areas affected by a fire. In certain embodiments, the density of an intumescent silicate material may be, for example, at least 0.85 g/mL. At this density, the intumescent silicate material may be dispersed by the carrier fluid far enough to cover an area affected by fire without spreading too far out. In various embodiments, the fire-retardant intumescent silicate material may comprise or may be intumescent silicate particles.

[0024] Details of the various embodiments are now described below. [0025] According to a first aspect of the present disclosure, there is provided a formulation for use in a dry powder fire extinguisher. The formulation may be a dry powder formulation. The formulation may comprise a carrier fluid and a fire-retardant intumescent silicate material disposed in the carrier fluid, wherein the fire-retardant intumescent silicate material comprises water glass and colloidal silica, wherein the water glass and the colloidal silica are different materials.

[0026] As mentioned above, the carrier fluid may function to aid in the discharge and dispersal of the fire-retardant intumescent silicate material for quenching fire. The carrier fluid may be stored as a pressurized liquid in a fire extinguisher, which carries and disperses the fire-retardant material upon its conversion to a gas when discharged from a fire extinguisher.

[0027] In various embodiments, the carrier fluid does not result in any residue that reduces visibility even when it is mixed with the fire-retardant intumescent silicate material, hence does not affect fire rescue operations when discharged from a fire extinguisher. In addition to or apart from the above, the carrier fluid may be non-toxic and/or has low or zero electrical conductivity.

[0028] In some embodiments, the carrier fluid may be ozone-friendly. By the term “ozone-friendly”, this means that the carrier fluid comprise or may be a fluorocarbon that does not react with ozone. The term“fluorocarbon” used herein refers to an organic compound that has one or more carbon-fluorine bonds. Examples of such a carrier fluid may include fluoroalkane, fluoroalkene, fluoroketone, and aromatic compounds containing one or more carbon-fluorine bonds. According to various embodiments, the carrier fluid may comprise a fluorocarbon selected from the group consisting of perfluoro(2-methyl-3-pentanone), heptafluoropropane, hexafluoropropane, and a combination thereof. Such fluorocarbons are advantageous in that they do not lead to environmental issues, as they do not react with ozone from the atmosphere.

[0029] In the present formulation, a fire-retardant intumescent silicate material is disposed in the carrier fluid for forming a fire extinguishing composition. The resultant formulation may have the fire-retardant intumescent silicate material and the carrier fluid present in a weight ratio of 5:20 to 80:95, 5:20 to 5:45, 5:45 to 80:95, etc. If the amount of fire-retardant intumescent silicate material and/or carrier fluid exceeds this range of weight ratio, the fire-retardant intumescent silicate material and/or the carrier fluid may end up clogging the nozzle of the fire extinguisher. If the amount of fire- retardant material and/or carrier fluid falls below this range of weight ratio, performance of the fire extinguishing composition may be adversely affected. For example, the carrier fluid may not disperse the fire-retardant intumescent silicate material sufficiently if there is insufficient carrier fluid present or effectiveness of the fire-retardant material may be compromised if insufficient fire-retardant intumescent silicate material is used.

[0030] In certain embodiments, the carrier fluid and the fire-retardant intumescent silicate material may be present in a weight ratio of 9: 1. In such a ratio, the fire-retardant intumescent silicate material can be easily dispersed in the carrier fluid.

[0031] The fire-retardant intumescent silicate material may comprise water glass and colloidal silica, wherein the water glass and the colloidal silica are different materials. As used herein, the term“water glass”, which is used interchangeably with the term “glass water”, is a common name for any sodium silicate compound having the formula Na₂(Si0₂)_n0 with n to be at least 1, available in aqueous solution. Besides sodium silicate, water glass may further comprise potassium silicate and/or lithium silicate. Water may be removed from the aqueous solution upon drying to result in a glassy solid, otherwise termed herein as“water glass powder”. Accordingly, the water glass may contain silicon dioxide, sodium silicate potassium silicate, and/or lithium silicate.

[0032] The fire-retardant intumescent silicate material may further comprise colloidal silica. As used herein, the term“intumescent” refers to ability of a material to expand, swell, foam, and/or increase in volume as a result of heat exposure. Due to the increase in volume, density of the material may decrease. The intumescent silicate material may expand to at least about 2 times its original volume, such as at least about 5 times its original volume, or such as at least about 10 times its original volume, etc. While the intumescent silicate material may be formed from colloidal silica and water glass, the intumescent silicate material has a lower thermal conductivity compared to the colloidal silica and water glass, which may in turn reduce conduction of heat in a fire. This advantageously prevents a fire from spreading.

[0033] The colloidal silica may be in the form of a suspension containing fine amorphous and non-porous silica particles. The colloidal silica may be comprised of silica particles. The colloidal silica may be used as a binder for various refractory materials. The colloidal silica also has strong adhesion and high temperature resistance (1500 to l600°C). It may be used in the coating industry to enhance the strength of a coating, and it can resist dirt, dust, aging, fire, etc. The colloidal silica may be a silica sol, which is odorless, non-toxic, and may be represented by the xSi0₂ yH₂0, where x and y may be any suitable value. The colloidal silica may be particles having a diameter ranging from, for example, 10 to 20 n , and this provides considerable specific surface area for coating of the water glass. As the colloidal silica is colorless and transparent, it does not affect the true color of a covered object, and hence does not impair judgement in a fire rescue operation when used. Its viscosity is also low, which allows it to penetrate tight corners and several other places affected by fire, hence this renders the fire-retardant intumescent silicate material made from such colloidal silica advantageous, as the dispersibility and permeability is not compromised, even when mixed with other substances. When water evaporates from the colloidal silica (or silica sol), the colloidal particles remaining may adhere firmly to the surface of the object, and the silicon-oxygen bond formed between the particles renders it a good binder.

[0034] The colloidal silica and the water glass may be present in a weight ratio of 0.8: 1.2 to 1.2:0.8, 1: 1.2 to l.2:0.8, 1:1 to l.2:0.8, 1.2:1 to l.2:0.8, 0.8:l.2 to 1.2: 1, 0.8:1.2 to 1:1, 0.8: l.2 to 1:1.2, etc. The colloidal silica and the water glass are present in a weight ratio of 1: 1, according to various embodiments. In this ratio, the resultant particles forming the fire-retardant intumescent silicate material can precipitate easily in the liquid mixture that they are prepared from. If more water glass is to be present, the resultant particles may not precipitate easily in the liquid mixture.

[0035] For avoidance of doubt, it is specified herein that the water glass and the colloidal silica are different materials. The colloidal silica is composed of polymeric silicate while the water glass is composed of discrete silicate monomers. In other words, the silicate monomers of the water glass are not polymerized to become a polymeric silicate. In some instances, colloidal silica may not contain alkali metal silicates such as sodium silicate and potassium silicate, and may instead contain alkaline earth metal silicates such as magnesium silicate, and aluminosilicate. The colloidal silica may have a silica (Si0₂) content in the range of 15 to 41 wt%, 15 to 16 wt%, 20 to 21 wt %, 25 to 26 wt%, 30 to 31 wt%, 40 to 41 wt%, etc. The colloidal silica may also have a sodium oxide (Na 0) content in the range of 0.04 to 0.55 wt%, for example, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.10 wt%, 0.25 wt%, 0.40 wt%, 0.50 wt%, 0.55 wt%. The colloidal silica may have a pH value in the range of 9 to 10.5 while the water glass may be more alkaline, e.g. pH 12 to 13. The colloidal silica may have a density, for example at 25°C, ranging from 1.12 to 1.30 g/cm³, or 1.12 to 1.14 g/cm³, or 1.15 to 1.17 g/cm³, or 1.19 to 1.21 g/cm³, or 1.28 to 1.30 g/cm³, etc.

[0036] The intumescent silicate material, formed from water glass and colloidal silica, is able to withstand high temperatures of up to 800°C and hence do not decompose easily in fire. Due to their high thermal resistance, the intumescent silicate particles are able to retain their mechanical strength and do not shrink in a fire after expanding upon heat contact, even after water is evaporated from the intumescent silicate material. The intumescent silicate material may also have better resistance to dunting, deformation and chipping in a fire. These advantageous properties may arise from the strength of bonding between the silicon atom and oxygen atom.

[0037] The present disclosure also provides for a fire extinguishing composition comprising the formulation described according to the first aspect. The fire extinguishing composition may be for use in a dry powder fire extinguisher. Various embodiments of the formulation, and advantages associated with various embodiments of the formulation, as described above may be applicable to the present fire extinguishing composition, and vice versa.

[0038] In various embodiments, the formulation described according to the first aspect is storable in the dry powder fire extinguisher at a pressure of 1 to 2 MPa, 1.5 to 2 MPa, or 1 to 1.5 MPa.

[0039] The present disclosure further provides for a method of producing the formulation described according to the first aspect. The method comprises mixing colloidal silica and water glass to form a fire-retardant intumescent silicate material in a liquid mixture, wherein the water glass and the colloidal silica are different materials, drying the liquid mixture to obtain the fire-retardant intumescent silicate material, and disposing the fire-retardant intumescent silicate material in a carrier fluid to form the formulation.

[0040] Various embodiments of the formulation, and advantages associated with various embodiments of the formulation, as described above may be applicable to the present method, and vice versa. For example, embodiments regarding the fire-retardant intumescent silicate material, the colloidal silica and the carrier fluid, and their advantages, have already been described above in relation to the first aspect of the present disclosure. As already mentioned above, the intumescent silicate material is produced from mixing of the colloidal silica and water glass. It has also been described above that in various embodiments, the carrier fluid may comprise a fluorocarbon selected from the group consisting of perfluoro(2-methyl-3-pentanone), heptafluoropropane, hexafluoropropane, and a combination thereof. The use of such fluorocarbons in the present method is advantageous in that the resultant formulation does not react with ozone to deplete ozone from the atmosphere which can lead to environmental issues.

[0041] Through use of the colloidal silica disclosed here, and mixing of the colloidal silica with water glass, and through the use of such a carrier fluid, the present method circumvents the use of ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate which are traditionally used as one of the chemicals to form a dry powder composition for extinguishing fire. As already mentioned above, phosphoric acid is produced when ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate undergo hydrolysis or break down at 240°C. The phosphoric acid is corrosive and attacks metals and even plastics. As ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate are lighter than the intumescent silicate material disclosed herein, they are more susceptible to wind dispersal which can cause them to spread over a larger area that includes an area not affected by the fire, and this may render the cleaning up process difficult.

[0042] The use of a fire-retardant intumescent silicate material comprising water glass and colloidal silica according to embodiments disclosed herein is also advantageous over ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate as they do not form corrosive acids and have better thermal resistance to withstand temperatures of up to 800°C. The fire-retardant intumescent silicate material may be deposited onto a burning or heated surface, forming a barrier layer that deprives the surface of oxygen, which in turn prevents a fire. With a higher thermal resistance, the barrier layer may last longer and does not shrink even upon contact with water to prevent a surface from re-ignition until the fire is put out completely. Moreover, as the fire-retardant intumescent silicate material comprising the colloidal silica is heavier than ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate, it does not get easily dispersed to unaffected areas and this renders the cleaning up process easier. Despite being heavier, the fire-retardant intumescent silicate retardant material remains sufficiently light to be carried and dispersed by the carrier fluid.

[0043] In the present method, a liquid mixture comprising a fire-retardant intumescent silicate material may first be prepared by mixing the colloidal silica and the water glass. The fire-retardant intumescent silicate material may be formed as a precipitate in this liquid mixture. Through this mixing, the colloidal silica may be interspersed uniformly or homogeneously within the water glass. The fire-retardant intumescent silicate material advantageously attains a lower thermal conductivity due to presence of the colloidal silica that helps to reduce conduction of heat in a fire, thereby preventing fire from spreading.

[0044] The water glass may be in the form of an aqueous solution comprising sodium silicate or potassium silicate, such that when the water evaporates, the solution solidifies into a glassy solid. The glassy solid may comprise silicon dioxide, sodium silicate, potassium silicate, and/or lithium silicate. As mentioned above, such an aqueous solution may be referred to as“glass water” in the present disclosure. Hence, when the colloidal silica are mixed in such an aqueous solution, and the aqueous solution is dried out, the water glass converts into water glass powder, which is interspersed with and/or is deposited on the colloidal silica as a coating.

[0045] Various embodiments of mixing the colloidal silica and the water glass may be carried out in a weight ratio 0.8: 1.2 to 1.2:0.8, 1: 1.2 to 1.2:0.8, 1:1 to 1.2:0.8, 1.2: 1 to 1.2:0.8, 0.8: 1.2 to 1.2: 1, 0.8: 1.2 to 1:1, 0.8: 1.2 to 1: 1.2, etc. Various embodiments of mixing the colloidal silica and the water glass may be carried out in a weight ratio of 1:1. The advantage of these ratios has already been discussed above and is not iterated for brevity.

[0046] After mixing the colloidal silica and the water glass, the liquid mixture may be dried to have water glass interspersed with and/or deposited on the colloidal silica as a coating. In various embodiments, drying the liquid mixture may comprise drying the liquid mixture at a temperature of 25 to l00°C. In certain embodiments, drying the liquid mixture may comprise drying the liquid mixture at a temperature of 60°C. [0047] When the liquid mixture is dried, a fire-retardant intumescent silicate material comprising water glass and the colloidal silica, wherein the water glass and the colloidal silica are different materials, is formed. The fire-retardant intumescent silicate material may then be disposed in the carrier fluid to form the present formulation. Disposing the fire-retardant material in the carrier fluid may comprise mixing the fire-retardant intumescent silicate material and the carrier fluid in a weight ratio of 5:20 to 80:95, 5:20 to 5:45, 5:45 to 80:95, etc., according to various embodiments. In certain embodiments, disposing the fire-retardant intumescent silicate material and the carrier fluid may comprise mixing the fire-retardant intumescent silicate material and the carrier fluid in a weight ratio of 1:9. The advantage of these ratios has already been discussed above and is not iterated for brevity.

[0048] The word“substantially” does not exclude“completely” e.g. a composition which is“substantially free” from Y may be completely free from Y. Where necessary, the word“substantially” may be omitted from the definition of the invention.

[0049] In the context of various embodiments, the articles“a”,“an” and“the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0050] In the context of various embodiments, the term“about” or“approximately” as applied to a numeric value encompasses the exact value and a reasonable variance.

[0051] As used herein, the term“and/or” includes any and all combinations of one or more of the associated listed items.

[0052] Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

[0053] While the methods described above are illustrated and described as a series of steps or events, it will be appreciated that any ordering of such steps or events are not to be interpreted in a limiting sense. For example, some steps may occur in different orders and/or concurrently with other steps or events apart from those illustrated and/or described herein. In addition, not all illustrated steps may be required to implement one or more aspects or embodiments described herein. Also, one or more of the steps depicted herein may be carried out in one or more separate acts and/or phases. Examples

[0054] The present disclosure relates to a formulation with improved efficiency for extinguishing fires. The formulation may be used to form a dry powder composition for extinguishing fire.

[0055] A dry powder fire extinguishing composition, comprising the present formulation, provides superior fire extinguishing properties over those that are based on ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate. For example, it can extinguish fires at a faster speed with better efficiency and has better dry powder flow rate from a fire extinguisher.

[0056] The formulation is advantageously non-toxic, as it is made from silicate particles, which forms a dry powder for putting out fire. As the silicate powder is heavier than ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate, it is less susceptible to wind dispersal and renders the cleaning process easier after use. In spite of being heavier, the silicate powder can still disperse to small spaces in between burning objects to quench fire when sprayed from the fire extinguisher.

[0057] The present formulation, the dry powder fire extinguishing composition comprising the formulation, and the method of producing the formulation, are described in the examples below.

[0058] Example 1: Materials

[0059] The present fire extinguishing composition, as an example, includes (1) a carrier gas, which also acts as a fire suppressing fluid, and (2) fire-retardant particles. The carrier gas, in this example, may be composed of HFC-236fa clean agent and/or 3M™ Novec™ 1230, which are fluorocarbons. A fire suppressing fluid when discharged from a fire extinguisher, converts to a gas due to its thermodynamic properties, and suppresses fire by removing heat. It is often used in automatic fire suppression systems, especially in facilities housing electronic equipment and avoids damaging electronics in the way that water does. The fire suppressing fluid may be termed as fire suppressant or fire suppressing agent in the present disclosure. The terms“carrier gas” and“fire supressing fluid”, may be referred to as a“carrier fluid” in the present disclosure. The carrier fluid, in the context of the present disclosure, may be composed of fluorocarbon. Fluorocarbons used in the present disclosure are preferably those that do not react with ozone.

[0060] The weight percentage of carrier gas to particles is 90 wt% : 10 wt%, both of which are compressed under pressure. For example, 900 g of Novec™ 1230 fire suppressing fluid and 10 g of the present fire extinguishing agent were added into a can under pressure.

[0061] Example 2a: Method of Producing the Present Dry Powder Fire Extinguishing Composition Based on Sepiolite

[0062] The steps for producing the present fire extinguishing composition, using a formulation based on 90 wt% Novec™ 1230 fire suppressing fluid and 10 wt% fire extinguishing powder based on sepiolite, are described below as a non-limiting example. The wt% is based on the total weight of the fire suppressing fluid and the fire extinguishing powder.

[0063] Firstly, a mixture of glass water with sepiolite or kyanite as the bulk filler, in a weight ratio of 1:1, was prepared to form the fire extinguishing powder component.

[0064] Sepiolite is one example of a bulk filler that has low thermal conductivity and is able to reduce the conduction of heat when sprayed on fire. Sepiolite, and other suitable silicate materials, can be evenly mixed with glass water that contains the silica (silicon dioxide) to form a solution. The solution mixture was then left to dry at 60°C to form a powder of coated silicate particles. The coated silicate particles has low thermal conductivity and reduces conduction of heat when sprayed on fire as a result of the coating. The powder of coated silicate particles may be termed fire-retardant powder in the present disclosure.

[0065] Novec™ 1230 fire suppressing fluid was used as an example for the liquid (i.e. fluid) component. This fire suppressing fluid not only serves as the fire suppressing agent, but also acts as the carrier medium for dispersing the powder component evenly when discharged from a fire extinguisher.

[0066] The powder component and the liquid component were then mixed together in a weight ratio of 1:9 to form the present fire extinguishing composition. As no toxic substances are involved, this composition does not release toxic gases or materials during fire. The steps for producing the present composition are simple and straightforward. [0067] Example 2b: Method of Producing the Present Dry Powder Fire Extinguishing Composition Based on Colloidal Silica

[0068] The steps for producing the present fire extinguishing composition, using a formulation based on 90 wt% Novec™ 1230 fire suppressing fluid and 10 wt% fire extinguishing powder based on colloidal silica, are described below as a non-limiting example. The wt% is based on the total weight of the fire suppressing fluid and the fire extinguishing powder.

[0069] Firstly, a mixture of glass water with colloidal silica as the bulk filler, in a weight ratio of 1 : 1 , was prepared to form the fire extinguishing powder component.

[0070] The produced intumescent silicate particles is one example of a bulk filler that has low thermal conductivity and is able to reduce the conduction of heat when sprayed on fire. Colloidal silica, and other suitable silicate materials, can be evenly mixed with glass water that contains, e.g. silica (silicon dioxide), to form a precipitated mixture. The precipitation was then left to dry at 60°C to form a powder of coated silicate particles. The coated silicate particles has low thermal conductivity and reduces conduction of heat when sprayed on fire as a result of the coating. The powder of coated silicate particles may be termed fire-retardant powder in the present disclosure.

[0071] Novec™ 1230 fire suppressing fluid was used as an example for the liquid (i.e. fluid) component. This fire suppressing fluid not only serves as the fire suppressing agent, but also acts as the carrier medium for dispersing the powder component evenly when discharged from a fire extinguisher.

[0072] The powder component and the liquid component were then mixed together in a weight ratio of 1:9 to form the present fire extinguishing composition. As no toxic substances are involved, this composition does not release toxic gases or materials during fire. The steps for producing the present composition are simple and straightforward.

[0073] Example 3: Performance of the Present Dry Powder Fire Extinguishing Composition Based on Example 2a

[0074] A thermogravimetric analysis of the fire-retardant intumescent silicate particles is shown in FIG. 2. Based on analysis of the fire-retardant particles, it is observed that the coated silica particles can withstand high temperatures up to 800°C. [0075] An infra-red (IR) analysis of the fire-retardant intumescent silicate particles was also carried out and the result is shown in FIG. 3. Based on the the IR-spectrum in FIG. 3, the silica particles demonstrate characteristic Si-0 strong peak at the region of 1000 cm ¹ to 1100 cm ¹ and the strong peak around 1250 cm ¹ relates to Si-C.

[0076] Both data demonstrate that the coated silica particles are able to withstand high temperatures.

[0077] Example 4: Characteristics of Components Used in Present Dry Powder Fire Extinguishing Composition

[0078] The present dry powder fire extinguishing composition is advantageous for putting out class A fires. The components used to form the present composition and the method of producing the present composition have already been described above. The present dry powder fire extinguishing composition includes a carrier fluid (fire suppressing fluid) and a fire-retardant intumescent silicate material.

[0079] As described above, the carrier fluid is mixed with the fire-retardant coated silicate particles to form the present fire extinguishing composition. The carrier fluid may be a fluorocarbon, such as Novec™ 1230, HFC-227ea, HFC-236fa, FE-36™, etc. Such fire suppressing fluids may replace Halon 1301 and Halon 1211 that are conventionally used in portable fire extinguishers, as they have comparable performance and efficiency to Halon 1301 and Halon 1211, lower toxicity, as well as zero ozone depletion potential. Such fire suppressant fluids are dischargeable as a stream of gas from a fire extinguisher, carrying the fire-retardant coated silicate particles. The fire suppressing fluids are characterized by high fire suppression efficiency, low toxicity, low residue formation after use, low or no electrical conductivity, and have long term storage stability. Such fire suppressing fluids, when mixed with the fire-retardant coated silicate particles do not give rise to corrosive or abrasive residues upon spraying and this renders them ideally suitable for use with high- value assets such as computer rooms, telecommunications facilities, process control rooms, museums, archives, marine, hospitals, banks, laboratories, and airplanes, where the use of an extinguishing powder comprising ammonium phosphate, monoammonium phosphate, or ammonium polyphosphate can cause damage. As such fire suppressing fluids are electrically non-conducting, they are therefore preferred for use to protect electrical and electronic equipment, and because of their low toxicity they are employable in areas where the evacuation of personnel may be undesirable or impossible.

[0080] The other component, which is the fire-retardant intumescent silicate particles, are composed of colloidal silica that is a refractory material with very high resistance to thermal shock. The colloidal silica do not suffer from shrinkage caused by heat from fire, has mechanical strength, thermal shock resistance, and resistance to dunting, chipping and deformation. Due to such properties, the water glass coating on the silicate particles can be made thinner.

[0081] While a variety of colloidal silica exist as a result of the nature of silicon atom, which is versatile and stable due to bonding between silicon and oxygen, only resultant silicate materials that can expand significantly when heated are suitable for use as a fire extinguishing agent. Such resultant silicate materials should be able to expand to at least 2 times its original volume. If the resultant silicate materials do not expand to such an extent, they may not adequately cover a non-ignited surface to prevent it from burning, or even cover a burning surface to put out a fire.

[0082] Depending on the particle size, temperature, and heating conditions, the colloidal silica used may be represented by the formula of xSi0₂ yH₂0, where x and y may be any suitable value. Colloidal silica may comprise silica (Si0₂) and/or sodium oxide (Na₂0), and have a pH ranging from 9 to 10.5. The silica content may range from 15 to 41 wt% while the sodium oxide content may range from 0.04 to 0.55 wt%. The density of colloidal silica may be, for example at 25 °C, any value in the range of 1.12 to 1.3 g/cm³.

[0083] In the manufacture of certain refractory products, specific amounts of extinguishing particles are added to the carrier fluid to maintain volume in the finished composition.

[0084] Example 5: Summary

[0085] The present disclosure relates to a formulation for the dry chemical agent used in fire extinguishers. The agent is based on non-toxic silicate particles powder. The silicate particles are fire-retardant and is more efficient than conventional powders comprising ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate. The present formulation can be used for extinguishing class A fires. The present formulation is non-toxic and minimizes damage to asset with minimum charring occurred.

[0086] The present formulation comprise or consists of two main components.

[0087] The first is the liquid component. The liquid component used in the present disclosure may be a fluorocarbon. An example of such a fluorocarbon may be Novec™ 1230. The liquid component may act as the carrier medium for the powder component, which is the second component. In other words, the liquid component is convertible to a gas that helps disperse the fire-retardant powder. Novec™ 1230 fluid is a low global warming potential for use as a gaseous fire suppressing agent, for example, in fire sprinklers and fire extinguishers. It is a suitable replacement for conventional Halons as it does not deplete the ozone layer. The liquid component is mixed with the powder component to form the present composition.

[0088] The second component, which is the powder component as already mentioned above, is a mixture of glass water and colloidal silica. Specifically, the powder component may comprise or consists of colloidal silica coated with glass water. The glass water and colloidal silica may be in a weight ratio of 1: 1. The resultant fire- retardant intumescent silicate material may also serve as the bulk filler. The sepiolite powder, as an example, has low thermal conductivity and reduces conduction of heat when sprayed on fire. The colloidal silica can be easily mixed with glass water to form a uniform solution. The solution mixture can be left to dry at a suitable temperature, e.g. room temperature (25°C) to l00°C, to obtain the powder component.

[0089] The powder and liquid components are then mixed in a weight ratio of 1:9. The resultant mixture is then pressurized (1 to 2 MPa, which is 10 to 20 bar) into a fire extinguisher for subsequent use. This formulation is non-toxic and environmental friendly. With non-toxic components, assets caught in a fire situation are protected from phosphoric acid corrosion that arises from use of extinguishing powders comprising ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate based fire extinguishers. In addition, there is no use of hydrophobic filler and the waste processing of the fire extinguisher is therefore much easier as there is no need to separate the powder component from a hydrophobic filler.

[0090] Example 6: Commercial and Potential Applications [0091] The present fire extinguishing composition, as described above, has comparable or even better efficiency over conventional ammonium phosphate, monoammonium phosphate, and ammonium polyphosphate based extinguishers.

[0092] The present composition can be used to effectively extinguish various types of fire, especially class A fires, and prevent the fuel from re-igniting.

[0093] The present composition has low chemical reactivity, long term storage stability, low toxicity, zero ozone depletion potential, and is non-corrosive to metals and electrically non-conducting. Due to such properties, the present composition is compatible for fire extinguishers used in computer rooms, telecommunications facilities, process control rooms, museums, archives, marine, hospitals, banks, laboratories, airplanes, etc.

[0094] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

1. A formulation for use in a dry powder fire extinguisher, the formulation comprising:

a carrier fluid; and

2. The formulation of claim 1, wherein the carrier fluid and the fire-retardant intumescent silicate material are present in a weight ratio of 20:5 to 95:80.

3. The formulation of claim 1 or 2, wherein the carrier fluid and the fire-retardant intumescent silicate material are present in a weight ratio of 9: 1.

4. The formulation of any one of claims 1 to 3, wherein the colloidal silica and the water glass are present in a weight ratio of 0.8: 1.2 to 1.2:0.8.

5. The formulation of any one of claims 1 to 4, wherein the colloidal silica and the water glass are present in a weight ratio of 1 : 1.

6. The formulation of any one of claims 1 to 5, wherein the carrier fluid comprises a fluorocarbon selected from the group consisting of perfluoro(2-methyl-3-pentanone), heptafluoropropane, hexafluoropropane, and a combination thereof.

7. A fire extinguishing composition comprising the formulation of any one of claims 1 to 6 for use in a dry powder fire extinguisher.

8. The fire extinguishing composition of claim 7, wherein the formulation of any one of claims 1 to 6 is storable in the dry powder fire extinguisher at a pressure of 1 to 2 MPa.

9. A method of producing the formulation of any one of claims 1 to 7, the method comprising:

disposing the fire-retardant intumescent silicate material in a carrier fluid to form the formulation.

10. The method of claim 9, wherein mixing the colloidal silica and the water glass is carried out in a weight ratio of 0.8: 1.2 to 1.2:0.8.

11. The method of claim 9 or 10, wherein mixing the colloidal silica and the water glass is carried out in a weight ratio of 1: 1.

12. The method of any one of claims 9 to 11, wherein drying the liquid mixture comprises drying the liquid mixture at a temperature of 25 to l00°C.

13. The method of any one of claims 9 to 12, wherein drying the liquid mixture comprises drying the liquid mixture at a temperature of 60°C.

14. The method of any one of claims 9 to 13, wherein disposing the fire-retardant intumescent silicate material in the carrier fluid comprises mixing the fire-retardant intumescent silicate material and the carrier fluid in a weight ratio of 5:20 to 80:95.

15. The method of any one of claims 9 to 14, wherein disposing the fire-retardant intumescent silicate material in the carrier fluid comprises mixing the fire-retardant intumescent silicate material and the carrier fluid in a weight ratio of 1 :9.

16. The method of any one of claims 9 to 15, wherein the carrier fluid comprises a fluorocarbon selected from the group consisting of perfluoro(2-methyl-3-pentanone), heptafluoropropane, hexafluoropropane, and a combination thereof.