Field of the invention The present invention relates to a composition comprising monoethylene glycol, monoammonium phosphate, water and optionally hydrogen borate for use as a fire retardant. The present invention also relates to a method of preparing said composition and a method of using said composition as a fire retardant. The present invention further relates to a method of imparting fire resistance to a substrate by applying said composition and to a fire resistant substrate.

Background of the invention

Residential and commercial fires annually claim the lives of hundreds of people and cause damage to property. As a result attention has focused on methods of eliminating or reducing the risk of fire by substituting combustible materials with fire resistant materials whenever possible. One approach is to treat combustible materials with a fire retardant composition, thereby rendering them less susceptible to burning. A number of such fire retardant compositions are known.

For example, US4514327 discloses a fire retardant composition for wood and fabric products, comprising ammonium sulfate, borax, boric acid, monoammonium phosphate and water. EP0146122 discloses a fire retardant composition for cellulosic substrates, comprising boric acid, an alkali metal borate, ammonium phosphate and water. US5405555 discloses a fire retardant composition for cellulosic materials, comprising ammonium sulfate, borax, boric acid, hydrogen peroxide, water and optionally a surfactant and/or an alkyl phthalate ester. US5151127 discloses a composition which preserves or protects wood and cellulose products against deterioration due to mould, fungi, insects, weather, fire and flames. The composition comprises boric acid, a water-based acrylic resin, water and optionally borax, urea, magnesium chloride, ammonium polyphosphate, ammonium thiosulfate and triethylamine. US4725382 discloses a fire retardant composition for wood products, comprising boric acid, diammonium phosphate, monoammonium phosphate and water. WO02/102926 discloses a fire retardant composition for wood-based panels, comprising a tertiary amine, boric acid or a borate, a phosphate and water. WO91/00327 discloses a fire retardant composition for wood and cellulosic products comprising boric acid and water.

However, the known fire retardant compositions have various disadvantages. For example, many fire retardant compositions are detrimental to the physical or mechanical properties of the substrate to which they are applied, for example causing the substrate to loose strength. Often the fire retardant compositions leave an unsightly deposit or residue on the substrate making it less aesthetically attractive. Moreover many fire retardant compositions are acidic and/or corrosive and/or hazardous to humans, which makes them unsafe to handle and limits their applicability.

Another problem is the environmental safety of the fire retardant compositions. Many fire retardant compositions comprise halogenated compounds, which are not only unsafe to handle, but can also emit toxic gases in the presence of fire. Toxic gases are frequently more dangerous to humans than the fire itself. Consequently, not only should the fire retardant compositions reduce substantially the flammability of the substrate, but they should also be safe to humans during flaming conditions. It would therefore be desirable to have a fire retardant composition which does not suffer from the disadvantages of the prior art compositions. The present invention provides an improved fire retardant composition.

It is an object of the present invention to provide a composition which is halogen-free, non-acidic, non-corrosive, eco-friendly, non-hazardous and/ or non-toxic. It is another object of the present invention to provide a composition which has good mechanical properties, for example, it is easy to apply, it penetrates a substrate well, it is easily absorbed by a substrate, and/or it has a good weathering performance. It is also an object of the present invention to provide a composition which renders a substrate fire resistant in the sense that the substrate burns less or more slowly or with less heat or in the sense that the substrate emits less toxic gas during burning. It is an object of the present invention to provide a composition which imparts this fire resistance without negatively affecting the physical or mechanical properties of the substrate. Summary of the invention

As used herein throughout the specification and claims, the term "fire retardant" composition refers to a composition which, when applied to a substrate, renders the substrate fire resistant. The term "fire resistant" substrate refers to a substrate which, when it is subjected to a flame or fire, burns less or more slowly or with less heat or emits less toxic gas, compared to the same substrate to which the composition has not been applied. In other words, a "fire resistant" substrate is less susceptible to burning and/ or less likely to emit toxic gas when it does burn, compared to the same substrate to which the composition has not been applied.

A first aspect of the present invention provides a composition comprising monoethylene glycol, monoammonium phosphate and water. Optionally the composition further comprises hydrogen borate. Preferably the composition consists essentially of or consists of monoethylene glycol, monoammonium phosphate and water. Alternatively, preferably the composition consists essentially of or consists of monoethylene glycol, monoammonium phosphate, water and a gelling agent. The composition is preferably a fire retardant composition. Preferably the composition of the first aspect of the present invention is a solution or a gel. If the composition is a gel, it preferably further comprises a gelling agent such as carboxymethyl cellulose.

If the composition of the first aspect of the present invention is a solution, it preferably comprises or consists essentially of or consists of:

(a) 1-35% by weight monoethylene glycol,

(b) 0-30% by weight hydrogen borate,

(c) 0.5-40% by weight monoammonium phosphate, and

(d) 35-98% by weight water.

More preferably, if the composition of the first aspect of the present invention is a solution, it comprises or consists essentially of or consists of:

(a) 1-30% by weight monoethylene glycol,

(b) 0-25% by weight hydrogen borate,

(c) 0.5-30% by weight monoammonium phosphate, and

(d) 35-98% by weight water. In one embodiment, the composition of the first aspect of the present invention comprises more than about 20% monoammonium phosphate by weight of the composition excluding water. In another embodiment, the composition comprises more than about 30% monoammonium phosphate by weight of the composition excluding water. In another embodiment, the composition comprises more than about 35% monoammonium phosphate by weight of the composition excluding water.

Preferably the composition of the first aspect of the present invention does not comprise any halogenated compounds. Preferably the composition does not comprise a carboxylic acid or a salt thereof. Preferably the composition does not comprise a sulfamic acid or a salt thereof.

Preferably the composition of the first aspect of the present invention has a pH of about 4-7·

Preferably the composition of the first aspect of the present invention is suitable for use as a fire retardant. A second aspect of the present invention provides a composition comprising monoethylene glycol, hydrogen borate, monoammonium phosphate and water. Preferably the composition consists essentially of or consists of monoethylene glycol, hydrogen borate, monoammonium phosphate and water. Alternatively, preferably the composition consists essentially of or consists of monoethylene glycol, hydrogen borate, monoammonium phosphate, water and a gelling agent. The composition is preferably a fire retardant composition.

Preferably the composition of the second aspect of the present invention is a solution or a gel. If the composition is a gel, it preferably further comprises a gelling agent such as carboxymethyl cellulose.

If the composition of the second aspect of the present invention is a solution, it preferably comprises or consists essentially of or consists of:

(a) 1-20% by weight monoethylene glycol,

(b) 1-30% by weight hydrogen borate,

(c) 8-40% by weight monoammonium phosphate, and (d) 35-90% by weight water.

More preferably, if the composition of the second aspect of the present invention is a solution, it comprises or consists essentially of or consists of:

(a) 2-15% by weight monoethylene glycol,

(b) 2-25% by weight hydrogen borate,

(c) 10-40% by weight monoammonium phosphate, and

(d) 35-85% by weight water. Preferably the composition of the second aspect of the present invention comprises more than about 20% monoammonium phosphate by weight of the composition excluding water. More preferably, the composition comprises more than about 30% monoammonium phosphate by weight of the composition excluding water. Most preferably, the composition comprises more than about 35% monoammonium phosphate by weight of the composition excluding water.

Preferably the composition of the second aspect of the present invention does not comprise any halogenated compounds. Preferably the composition does not comprise a carboxylic acid or a salt thereof. Preferably the composition does not comprise a sulfamic acid or a salt thereof.

Preferably the composition of the second aspect of the present invention has a pH of about 4-7. Preferably the composition of the second aspect of the present invention is suitable for use as a fire retardant.

A third aspect of the present invention provides a method of preparing a composition according to the first or second aspect of the present invention, wherein the method comprises mixing monoethylene glycol, monoammonium phosphate, water and optionally hydrogen borate in any order.

Preferably the monoethylene glycol, monoammonium phosphate, water and optionally hydrogen borate are mixed to form a solution or a gel. Preferably the method is carried out at room temperature. Optionally the reaction mixture may be heated up to 50°C.

Preferably the method comprises the steps of:

(a) dissolving monoammonium phosphate in water, and

(b) adding monoethylene glycol to the solution obtained in step (a).

Alternatively, preferably the method comprises the steps of:

(a) dissolving hydrogen borate in water,

(b) adding monoammonium phosphate to the solution obtained in step (a), and

(c) adding monoethylene glycol to the solution obtained in step (b).

A fourth aspect of the present invention provides a method of using a composition according to the first or second aspect of the present invention as a fire retardant, the method comprising the step of applying the composition to a substrate.

The fourth aspect of the present invention also provides a method of imparting fire resistance to a substrate, the method comprising the step of applying a composition according to the first or second aspect of the present invention to the substrate.

Preferably the treated substrate has a substrate : composition weight ratio of from 1:2 to 150: 1 after drying, preferably from 1:1 to 100:1, preferably from 1:1 to 80:1.

Preferably the composition is applied to the substrate in order to render it less susceptible to burning and/ or less likely to emit toxic gas when it does burn.

Preferably the substrate is a cellulose based substrate (such as paper, carton, timber, wood, MDF, HDF or laminated flooring), a sponge, a foam or a fabric (such as cotton, wool, rayon or polyester).

The composition may be applied to the substrate by any suitable method, including but not limited to dipping, soaking, coating, spraying, brushing, rolling, pouring, immersing, submerging, impregnating or pressure impregnating. Preferably the composition is applied to the substrate, followed by drying the substrate. A fifth aspect of the present invention provides a substrate to which a composition according to the first or second aspect of the present invention has been applied.

Preferably the substrate is a cellulose based substrate (such as paper, carton, timber, wood, MDF, HDF or laminated flooring), a sponge, a foam or a fabric (such as cotton, wool, rayon or polyester).

The composition may be applied to the substrate by any suitable method, including but not limited to dipping, soaking, coating, spraying, brushing, rolling, pouring, immersing, submerging, impregnating or pressure impregnating. Preferably the composition is applied to the substrate, followed by drying the substrate.

Preferably applying the composition to the substrate has rendered the substrate less susceptible to burning and/or less likely to emit toxic gas when it does burn. Preferably when the substrate is subjected to fire, the substrate burns less or more slowly or with less heat or emits less toxic gas, compared to the same substrate to which the composition has not been applied.

Detailed description of the invention

The composition of the present invention comprises monoethylene glycol (H0CH ₂ CH ₂ 0H), monoammonium phosphate (NH ₄ H ₂ P0 ₄ ), water and preferably hydrogen borate (H ₃ B0 ₃ ). Without wishing to be bound by theory, it is believed that when a substrate treated with a composition according to the present invention, is subjected to a flame or fire, the monoammonium phosphate reduces the amount of oxygen on the surface of the substrate and prevents oxygen from penetrating the substrate, such that the substrate only carbonizes but does not burn. The high heat resistance of hydrogen borate is believed to slow down heat transfer and to delay the substrate from reaching burning temperature. Hydrogen borate is also believed to increase the heat resistance of substrates and to suspend water molecules in cellulose based substrates. It is further believed that the presence of the monoethylene glycol in the composition of the present invention provides the composition with its good mechanical properties and weathering performance. Example l

Hydrogen borate (300g) was dissolved in water (io,oooml) with stirring. Then monoammonium phosphate (2,ooog) was added to the solution under stirring. Finally monoethylene glycol (300ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature.

Example 2 Hydrogen borate (200g) was dissolved in water (500ml) with stirring. Then monoammonium phosphate (200g) was added to the solution under stirring. Finally monoethylene glycol (90ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature. Example 3

An ecru woven fabric (80% cotton) was dipped into the solution obtained in example 1. lkg of fabric absorbed about 200g of the solution of example 1. The fabric was dried at room temperature for 24 hours. Then the fabric was subjected to a naked flame. The emitted gas was tested for the presence of tris(2,3-dibromopropyl) phosphate (TRIS), polybrominated biphenyl (PBB), tris(i-aziridinyl) phosphine oxide (TEPA), pentabromo diphenyl ether (pentaBDE), octabromo diphenyl ether (octaBDE), hexabromocylcododecane (HBCDD), decabromo diphenyl ether (decaBDE), tris(2- chloroethyl) phosphate (TCEP) and short-chained chlorinated paraffins (C10-C13). None of these compounds were detected (detection limit 5ppm).

Example 4

Oak was dipped into the solution obtained in example 1 for 12 hours. 200g of oak absorbed about 75g of the solution of example 1. The oak was dried at room temperature for 24 hours. Then treated and untreated oak samples were subjected to a burning test using a gas-fired radiant heat panel with pilot flame ignition. The results of this burning test are summarised in Table 1. Parameter Untreated oak Treated oak

(average of 3 specimens) (average of 3 specimens)

Critical flux at 6.74 18.20 extinguishment, CFE (kW/ m ² )

Heat for sustained burning, 0.81 4.70

Total heat release, Q _t (MJ) 0.48 0.38

Peak heat release, % (kW) 1.94 1-37

Burning droplets no no

Table 1

Example 5

Fabric (80% cotton) was dipped into the solution obtained in example 1. ikg of fabric absorbed about 200g of the solution of example 1. The fabric was dried at room temperature for 24 hours. Then treated and untreated fabric samples were subjected to a burning test using a gas-fired radiant heat panel with pilot flame ignition. The results of this burning test are summarised in Table 2.

Table 2 Example 6

Oak was dipped into the solution obtained in example ι for 12 hours. 200g of oak absorbed about 75g of the solution of example 1. The oak was dried at room temperature for 24 hours. Then the treated oak was tested according to BS 476 Part 7 "Surface spread of flames". The treated oak was classified as class 2.

Example 7 A composite of upholstery foam and fabric (80% cotton) was dipped into the solution obtained in example 1. The composite was dried at room temperature for 24 hours. Then treated and untreated composite samples were tested according to BS 5852 Crib 5 Test. The weight of the tested composites (after drying) is summarised in Table 3. The untreated composite failed the test, the treated composite passed the test.

Table 3

Example 8 Fabric (80% cotton) was dipped into the solution obtained in example 1. ikg of fabric absorbed about 200g of the solution of example 1. The fabric was dried at room temperature for 24 hours. Then treated and untreated fabric samples were tested according to BS 5438: 1989 Test 2A "Limited flame spread: face ignition". The results of this test are summarised in Table 4. Parameter Untreated fabric Treated fabric

(average of 3 specimens) (average of 3 specimens)

Flame application time 10 seconds in 10 seconds in 10 seconds in 10 seconds in warp direction weft direction warp direction weft direction

Duration of flaming after 79-7 64.7 73-3 114.7 removal of ignition source

(sec)

Duration of afterglow (sec) N/A N/A N/A No

Glowing reaches upper N/A N/A No No edge or one of vertical

edges

Occurrence of any flaming Yes Yes No Yes debris

Flame reaches upper edge Yes Yes Yes Yes

Flame reaches vertical Yes Yes Yes Yes edge

Hole develops which Yes Yes Yes Yes extends to upper edge or

one of vertical edges

Maximum extent of any 160 160 160 160 hole in horizontal

direction (mm)

Maximum extent of any 200 200 200 200 hole in vertical direction

(mm)

Maximum damaged length 200 200 200 200 (ignoring any surface

effects such as scorching

or smoke deposition)

Table 4

Example Q

Oak was dipped into the solution obtained in example 1 for 12 hours. 200g of oak absorbed about 75g of the solution of example 1. The oak was dried at room temperature for 24 hours. Upholstery foam was dipped into the solution obtained in example 1. 200g of foam absorbed about 200g of the solution of example 1. The foam was dried at room temperature for 24 hours. Corrugated cardboard was sprayed with the solution obtained in example 1. i50g of cardboard absorbed about log of the solution of example 1. The cardboard was dried at room temperature for 24 hours. Then the treated and untreated materials were tested according to TS EN 60695-11-10 (Fire hazard testing - Part 11-10: Test flames - 50W horizontal and vertical flame test methods). The results of this test are summarised in Table 5. Material Vertical burning Horizontal burning classification classification (average of 5 specimens) (average of 3 specimens)

Untreated oak None not tested

Untreated cardboard V-2 not tested

Untreated foam ignited immediately and melted and ignited immediately and melted and burned completely within a few burned completely within a few seconds seconds

Treated oak V-0 not tested

Treated cardboard V-i not tested

Treated foam None HB40

Table 5

The treated and untreated materials were also tested according to DIN 4102-1 (Fire behaviour of building materials and elements - Classification of building materials - Requirements and testing - Subclause 6.2 Class B2 Materials). The results of the edge ignition test are summarised in Table 6 and the results of the surface ignition test are summarised in Table 7.

Table 6 Observation Untreated Untreated Untreated Treated Treated Treated oak cardboard foam oak cardboard foam

Number of 5 5 5 0 0 0 specimens

flamed

Number of 0 0 0 5 5 5 specimens not

flamed

Span time - 15-25 <5 - - - (sec)

Did molten no no yes no no no dripping

occur?

Did filter no no yes no no no paper get

flamed?

Table 7

The results shown in Tables 6 and 7 indicate that the DIN 4102-1 fire classes of the untreated materials are B2 or worse and that treatment with the composition of the present invention improved their fire classes to better than B2.

The tests according to TS EN 60695-11-10 and DIN 4102-1 both showed that application of the composition of the present invention improved the resistance of all three materials to ignition and flame spread.

Example 10

Hydrogen borate (7g) was dissolved in water (650ml) with stirring. Then monoammonium phosphate (8g) was added to the solution under stirring. Finally monoethylene glycol (200ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature.

Example 11

Hydrogen borate (log) was dissolved in water (700ml) with stirring. Then monoammonium phosphate (8g) was added to the solution under stirring. Finally monoethylene glycol (120ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature. Example 12

Hydrogen borate (2g) was dissolved in water (800ml) with stirring. Then monoammonium phosphate (8g) was added to the solution under stirring. Finally monoethylene glycol (100ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature.

Example 13 Monoammonium phosphate (28g) was dissolved in water (700ml) with stirring. Then monoethylene glycol (20ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature.

Example 14

Hydrogen borate (lg) was dissolved in water (800ml) with stirring. Then monoammonium phosphate (i8g) was added to the solution under stirring. Finally monoethylene glycol (10ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature.

Example 15

Hydrogen borate (2.5g) was dissolved in water (750ml) with stirring. Then monoammonium phosphate (20g) was added to the solution under stirring. Finally monoethylene glycol (25ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature.

Example 16 Hydrogen borate (5g) was dissolved in water (750ml) with stirring. Then monoammonium phosphate (i5g) was added to the solution under stirring. Finally monoethylene glycol (50ml) was added to the solution under stirring to obtain a final solution. The process was carried out at room temperature. Example 17

Oak was dipped into the solution obtained in example 16 for 12 hours. 200g of oak absorbed about 75g of the solution of example 16. The oak was dried under sun conditions for 4 hours. Then oak samples (three specimens, each with dimensions 75 mm x 75 mm and a maximum thickness of 25 mm) were subjected to a smoke generation test conducted in accordance with ISO 5659:1994, Part 2, and a toxicity test conducted by use of FTIR. The results of the smoke generation test are given as the specific optical density of smoke (DS) as defined below. The test results are given as Dm, the average of the DS _ma x for three tests.

DS = (V/(AL))logio(IO/I)

where V = total volume of the chamber (m ³ )

A = exposed area of the specimen (m ² )

L = optical length (m) of smoke measurement

10 = light intensity before the test

I = light intensity during the test (after absorption by the smoke) The results of the smoke generation test are summarised in Table 8, the results of the toxicity test in Table 9.

Table 8

Gas species Average concentration in each mode (ppm)

25 kW/m ² 25 kW/m ² 50 kW/m ² without without with pilot flame pilot flame pilot flame

Carbon monoxide (CO) 130 38 159

Hydrogen chloride (HC1) 154 5 45

Hydrogen bromide (HBR) not detected not detected not detected

Hydrogen cyanide (HCN) 5 1 1

Hydrogen fluoride (HF) not detected not detected not detected

Sulphur dioxide (S0 ₂ ) 10 2 2

Nitrous fumes (NO _x ) not detected not detected not detected

Table 9

The results shown in Tables 8 and 9 indicate that the tested oak samples passed the smoke generation test and the toxicity test.

It will be understood that the present invention has been described above by way of example only. The examples are not intended to limit the scope of the invention. Various modifications and embodiments can be made without departing from the scope and spirit of the invention, which is defined by the following claims only.