GB1603867A

GB1603867A - Fire extinguisher formulation

Info

Publication number: GB1603867A
Application number: GB3685077A
Authority: GB
Original assignee: Thacker D A
Current assignee: Thacker D A
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-12-02

Description

(54) FIRE EXTINGUISHER FORMULATION (71) 1, DEREK AUBREY THACKER, a British subject, of Blue Seas, 47 Southdean Drive, Middleton, Bognor Regis, West Sussex, P022 7TB, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to fire extinguisher formulations and more particularly to those based on trichlorofluoromethane, CCI3F, hereinafter referred to as F,l, for use in fire extinguishers and fire extinguishing systems.

F11 and a related compound Fl2 (dichlorodifluoromethane CCI2F2) are incombustible, non-toxic organic compounds which have quite low boiling points, 25"C and -29.8"C, respectively.

Their physical and chemical properties suggest their suitability for use in fire extinguishing formulations, but it has been found in practice to be difficult to utilise these compounds effectively to extinguish fires.

In order to be really effective a fire extinguishing formulation should be capable of being projected into the seat of a fire from some distance away, e.g. about 12 feet, without the jet or spray being dispersed before it reaches the fire. Also the formulation should undergo some endothermic process on being heated by the fire in order to abstract heat from the fire, and then form a heavy inert blanket over the seat of the fire to exclude oxygen from the area.

It has been known to use F11 in liquid fire extinguishing formulations using liquified Fl2 as the gaseous propellant, but only as a diluent for other more expensive fire extinguishing compounds like BCF (dibromodifluoromethane CBr2F2). Even in these formulations, the effectiveness of the F11 in extinguishing the fire is only slight because of the evaporation of the F11 from the droplets of the formulation as they travel to the fire. This is a major problem when using F11 as the major component in a formulation. The result of such evaporation is that the area of the fire hit by the jet or spray is large with consequential loss in the effective "wetting" of the area.Also the average droplet size of the formulation at the seat of the fire is small which results in a reduction in the quantity of heat abstrated from the fire.

In an attempt to overcome this problem it has been suggested to use a high pressure of Fl2 or other propellant, e.g. CO2 or N2, in order to reduce the time taken for the liquid droplets to reach the fire and also to provide a significant cooling effect due to the sudden expansion of the high pressure gas through the nozzle. As a result, however, the average droplet size of the liquid leaving the nozzle of the extinguisher is greatly reduced when compared to the size of droplets of liquid leaving the same nozzle under a lower pressure, and thus the advantages gained by using high pressure are minimal.Furthermore, the container for the fire extinguishing formulation has to be expensively strengthened in order to avoid the danger of the extinguisher exploding on becoming heated, e.g. in the fire itself or when supplied to tropical countries.

When designing a fire extinguisher for use in the home, in the office or in public transport, therefore, it is highly desirable that the extinguisher should only be pressurised to a small extent and yet be capable of throwing an effective spray of liquid some 12 feet to the seat of the fire.

Although conventional BCF extinguishers are capable of meeting these requirements, a very serious disadvantage of BCF is that when subjected to pyrolysis in a fire, hydrogen bromide is given off in significant quantities. This gas is highly toxic and is fatal in even small quantities in, for example, a room in which a person is attempting to extinguish a fire.

It has now been found that F11 can be used as the major component optionally in combination with Fl2, in a fire extinguisher formulation if a certain additive is present with the F11 to reduce greatly the volatility of the F11 droplets as they travel to the fire.

The selection of the additives is important.

The final formulation must be completely homogeneous to ensure uniform effectiveness of the extinguisher when in use. It must be completely free of water to avoid any decomposition of the Fll. It must be non-toxic in its liquid form and must not produce any hydrogen bromide on pyrolysis. It must be electrically nonconductive and have a high electrical breakdown voltage so that the formulation can be used to tackle electrical fires without any danger of current passing back through the spray from the fire to the extinguisher.

Finally the formulation must have a specific gravity sufficient to allow the extinguisher to be pressurised to a comparatively low pressure, e.g. from 25 to 45 psig.

In accordance with the present invention there is provided a homogeneous fire extinguishing composition comprising trichlorofluoromethane and an additive in an amount of up to 1 part in 400 parts, preferably from 1 part in 800 parts to 1 part in 400 parts, based on the total weight of the composition, wherein the additive comprises at least one mono-terpene; the composition being essentially free of water.

Preferably the additive includes at least one essential oil, such as a citrus oil or pinene, optionally together with a solvent for the mono-terpene(s), e.g. an aromatic solvent such as isopropyl-benzene either alone or admixed with toluene in a weight ratio of e.g. 1:0.75 to 1:1.5.

When an essential oil is present the total weight of essential oil is between 25% and 75% by weight of the additive, and when a solvent is present the total weight of solvent is between 10% and 30% by weight of the additive.

Desirably the specific gravity of the composition is 1.5+0.1.

A particularly effective additive for F11 has been discovered which has the following composition: weight percent Mono-terpene 35 Isopropylenzene 10 Toluene 15 Special Mixture HMD6 40 Any individual mono-terpene or mixture of mono-terpenes is useful in the present additive. Special Mixture HMD6 is the trade name of a commercially available material manufactured and sold by Norken Supplies of Kings Lynn, Norfolk.

The present invention, also provides a fire extinguisher containing a composition of the present invention when pressurised by an inert gas such as carbon dioxide, nitrogen or dichlorodifluoromethane.

To prepare the most preferred composition of the present invention, the mono-terpene and the Special Mixture are combined and then the isopropylb-enzene and toluene are added and homogenised.

This mixture is then added to the Fll. This homogeneous liquid can then be used to fill the fire extinguisher container to a level sufficiently low to allow approximately 20 percent by volume head-space for the propellant. The container is then pressurised with Fl2 from 25 to 45 psig, optionally including carbon dioxide or nitrogen for over-pressurisation. Carbon dioxide is preferred since if the container gets heated, although CO2 possesses a greater coefficient of thermal expansion than N2, the increased pressure causes the gas to dissolve in the liquid composition.

Thus the increase in pressure that results through heating is only minimal.

The most effective ratio of F11 to F.2 has been found to be 80:20 percent by volume-the Fl2 being a liquid at room temperature and at a pressure of from 25 to 45 psig. The most effective ratio of additive to FIJFl2 mixture has been found to be 1 part by weight of additive per 600 parts by weight of mixture. The extent of overpressurisation is not critical and depends on the particular field of use of the extinguisher and on the size of the container used.

It has been found that the above composition can be used in conventional low pressure spray-type fire extinguishers without any need to modify their nozzles and yet it will produce a jet or spray which can travel some 12 feet to the seat of a fire without significant dispersion of the liquid.

The droplets formed are quite heavy and can reach the fire without significant reduction in their size through evaporation, so that the area hit by the jet or spray is comparatively small and is thus well wetted by the composition. On reaching the fire, the droplets of F11 evaporate so taking heat away from the fire and form a heavy oxygen-excluding blanket around the fire.

Furthermore the additive present in the composition does not cause any staining of objects or fabrics which have been wetted by the composition. This is of particular importance when the fire has occurred in stock which is easily damaged by, for example, water from conventional fire extinguishing equipment.

On pyrolysis, the present composition does not produce any hydrogen bromide and, although a very small quantity of toxic phosgene is produced as with other commercially available formulations, the operator can extinguish the fire in a closed room without any danger to his health.

Since the residue from the composition of this invention after evaporation possesses a slight, although not unpleasant smell, it is obvious to personnel at the scene of the fire that an extinguisher has been used and it encourages the personnel to ventilate the room after the fire has been extinguished.

WHAT I CLAIM IS: 1. A homogeneous fire extinguishing composition comprising trichlorofluormethane and an additive in an amount of up to 1 part in 400 parts based on the total weight of the composition, wherein the additive comprises at least one mono-terpene; the composition being essentially free of water.

2. A composition as claimed in claim 1 wherein the additive includes at least one essential oil.

3. A composition as claimed in claim 2 wherein the essential oil is a citrus oil.

4. A composition as claimed in claim 2 wherein the essential oil is pinene.

5. A composition as claimed in any one of the preceding claims wherein the additive includes a solvent for the mono-terpene(s).

6. A composition as claimed in claim 5 wherein the solvent is an aromatic solvent.

7. A composition as claimed in claim 6 wherein the solvent is isopropyl-benzene.

8. A composition as claimed in claim 6 wherein the solvent is a mixture of isopropyl-benzene and toluene.

9. A composition as claimed in claim 8 wherein the ratio by weight of isopropylbenzene to toluene in the solvent mixture is from 1:0.75 to 1:1.5.

10. A composition as claimed in any one of the preceding claims wherein the additive is present in an amount of from 1 part in 800 parts to 1 part in 400 parts, based on the total weight of the composition; all parts being by weight.

I I. A composition as claimed in claim 10 wherein the additive is present in an amount of about 1 part by weight in 600 parts by weight, based on the total weight of the composition.

12. A composition as claimed in any one of the preceding claims wherein when an essential oil is present the total weight of essential oil is between 25% and 75% by weight of the additive.

13. A composition as claimed in any one of the preceding claims wherein when a solvent is present the total weight of solvent is between 10% and 30% by weight of the additive.

14. A composition as claimed in any one of the preceding claims having a specific gravity of 1.5+0.1.

15. A composition as claimed in claim 1 substantially as hereinbefore described.

16. A fire extinguisher containing a composition as claimed in any one of the preceding claims and pressurised by an inert gas.

17. An extinguisher as claimed in claim 16 wherein the inert gas is carbon dioxide or nitrogen.

18. An extinguisher as claimed in claim 16 wherein the inert gas is dichlorodifluoromethane.

19. An extinguisher as claimed in any one of claims 16 to 18 when pressurised to from 25 to 45 psig.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. slight, although not unpleasant smell, it is obvious to personnel at the scene of the fire that an extinguisher has been used and it encourages the personnel to ventilate the room after the fire has been extinguished. WHAT I CLAIM IS:

1. A homogeneous fire extinguishing composition comprising trichlorofluormethane and an additive in an amount of up to 1 part in 400 parts based on the total weight of the composition, wherein the additive comprises at least one mono-terpene; the composition being essentially free of water.

4. A composition as claimed in claim 2 wherein the essential oil is pinene.