WO1997020599A1

WO1997020599A1 - Fire extinguishing methods and blends utilizing fluorinated hydrocarbon ethers

Info

Publication number: WO1997020599A1
Application number: PCT/US1996/019133
Authority: WO
Inventors: Lawrence R. Grzyll; Dwight D. Back; Charlie Ramos; Nidal A. Samad
Original assignee: Mainstream Engineering Corp
Current assignee: Mainstream Engineering Corp
Priority date: 1995-12-04
Filing date: 1996-12-04
Publication date: 1997-06-12
Anticipated expiration: 1998-06-04
Also published as: AU1127297A

Abstract

Fluorinated ethers are effective fire extinguishing agents, with flame extinguishing concentrations comparable to those of conventional Halons. Fluorinated ethers have similar volatility, residue levels, materials compatibility characteristics, and safety characteristics as conventional Halons, and they are also environmentally acceptable.

Description

FIRE EXTINGUISHING METHODS AND BLENDS UTILIZING FLUORINATED HYDROCARBON ETHERS

CROSS-REFERENCE TO RELATED APPLICATIONS

Thxs application is a contmuation-in-part of Application Serial No. 08/519 , 809 filed on August 25, 1995 m the name of Lawrence Robert Grzyll et al . for FIRE EXTINGUISHING METHODS AND BLENDS UTILIZING UNSATURATED PERFLUOROCARBONS, the sub ect matter of which is incorporated herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to fire extinguishing methods and blends utilizing fully or partially fluorinated C₂ to C₈ organic ethers.

The use of halogenated chemical agents containing combinations of fluorine, chlorine, bromine, iodine, and hydrogen is well-known. The most common of these agents are Halon 1301 (CF₃Br) , Halon 1211 (CF₂ClBr) , and Halon 2402

{CF₂BrCF₂Br) . These three agents are thought to be effective at fire extinguishment because they decompose in the f re and interfere with the normal chain reactions of the fire combustion process (i.e. they are chain terminators) .

Known extinguishing agents also possess the volatility that makes them useful for total flooding applications or streaming applications in portable fire extinguishers They are clean agents; this means that they leave no residue upon evaporation or during fire suppression They are also nonreactive to the majority of metals and nonmetals with which they come into contact with during use. They are also safe agents, having toxicity characteristics suitable for occupied spaces during their use .

The above-mentioned three Halon agents are, however, believed to be capable of destroying the ozone layer. Hence, their manufacture has been banned by recent environmental regulations. They are also thought to contribute to global warming because their atmospheric lifetime is sufficiently long that they persist in the atmosphere and absorb solar radiation.

In an effort to solve this problem, U.S. Patent No.

5,124,053 describes the use of saturated, higher fluorinated hydrofluorocarbons and blends thereof with other agents for use in fire extinguishing methods and apparatus. Specifically, U.S. Patent No. 5,124,053 describes the use of saturated C₂ or C₃ higher fluorinated hydrocarbons of the formula C_xH_yF_z, where x is 2 or 3 , y is 1 or 2 , and z is 5, 6, or 7 : where y is 1 and z is 5 when x is 2 and where z is 6 or 7 when x is 3. Because these compounds contain no chlorine or bromine, they have zero ozone depletion potential. The compounds are also asserted not to pose a threat as greenhouse warming gases and also have toxicity characteristics suitable for use in occupied spaces. However, they must be used at much higher flame extinguishing concentrations than the common halons .

Adcock et al . , Fluorinated Ethers, A New Family of

Halon, presented at the International CFC and Halon Alternatives Conference, Baltimore, Maryland, December 3-5, 1991, briefly discusses fluorinated ethers, such as perfluoro-tetrahydrof ran and trifluorome hyl- difluoromethyl ether, as halon alternatives useful as fire extinguishants . As with U.S. Patent No. 5,124,053, they must also be used at higher flame extinguishing concentrations than the common halons. It is an object of the present invention to provide a fire extinguishing method that extinguishes fires as effectively as the common Halons by using a minimum concentration to extinguish a fire, and that has similar volatility, residue levels, materials compatibility characteristics, and safety characteristics, and yet is environmentally acceptable.

It is a further object of this invention to provide blends of fluorinated ethers and other fire extinguishing agents, such as conventional fire extinguishing agents or saturated or unsaturated perfluorocarbons-, that share the useful properties described above but are environmentally acceptable .

These objectives have been achieved with the recognition that fluorinated C₂ to C₈ organic ethers are effective fire extinguishing agents at concentrations similar to those of the well-known Halons. However, these materials also have no chlorine or bromine constituents, and thus, have zero ozone depletion potential.

We have also found that because these compounds contain oxygen and hydrogen for non-perfluoro-ether carbons, they are much less stable and are susceptible to breakdown in the lower atmosphere, and thus do not pose a threat as a greenhouse warming gas .

Specific C₂ to C₈ perfluoroethers and fluorinated ethers which are useful include compounds of the formula C_xF_yH_zO_w for which x is equal or greater than 2 and less than or equal to 8, and w is greater than zero. For non- cyclic compounds, y=2x+2-z, and for cyclic compounds y will be greater than or equal to 2x-z, and less than or equal to 2x+2-z. Specific non-cyclic and cyclic fluorinated ethers which are useful include difluoromethyl-2 , 2, 2- trifluoroethyl ether (CF₃-CH₂-0-CHF₂) , heptafluoropropyl- 1, 2, 2, 2-tetrafluoroethyl ether (CF₃-CF₂-CF₂-0-CHF-CF₃) , and perfluoro-2-butyltetrahydrofuran (CF₃-CF₂-CF₂-CF₂-C₄F₇0) .

These compounds may be used alone, in mixture with one another, or in mixture with other fire extinguishing agents or gases. These agents may be applied using the standard fire extinguishing application techniques and methods used for the standard Halons. These agents may be used in total flooding applications or systems where an entire enclosed region is subjected to the agent, or they may be used in portable fire extinguishing equipment. The agents may be pressurized with nitrogen or another inert gas to ensure adequate flow of the agent through the fire suppression system.

These agents should be used at a minimum concentration to effectively extinguish a fire. This exact concentration depends on several variables, including the exact agent or blend used, the combustion material, and the combustion of fire conditions and scenario. The best laboratory results have been found where the agent is employed at a concentration of at least 3% (v/v) . The maximum concentration employed is determined, generally speaking, by economics and safety. Of course, in unoccupied areas, where no living things are present, the maximum concentration can be increased.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

The fire suppression effectiveness of difluoromethyl- 2, 2, 2-trifluoroethyl ether, heptafluoropropyl-1, 2 , 2, 2- tetraf 1uoroethy1 ether, and perfluoro-2- butyltetrahydrofuran were demonstrated in a dynamic test using a glass cup burner apparatus and test procedure with n-heptane and air being supplied to the burner. Vapor of the agent being tested, generated by vaporizing the agent with heat, was mixed with air and introduced to the flame. The concentration of the agent in the air mixture was slowly increased until the flame was extinguished; this is referred to as the flame extinguishing concentration (FEC) . Table 1 provides a summary of the data for difluoromethyl- 2 , 2, 2-trifluoroethyl ether, heptafluoropropyl-1, 2, 2 , 2- tetraf1uoroethy1 ether, and perfluoro-2- butyltetrahydrofuran and compares this data to published values for the standard Halons and for some of the fire suppression agents described in U.S. Patent No. 5,124,053 and Adcock et al . , Fluorinated Ethers, A New Family of Halons . Table 1 shows that, in terms of flame extinguishing concentration, the compounds of this invention are more effective agents than the compounds described in U.S. Patent No. 5,124,053 and Adcock et al . for n-heptane diffusion flames in the cup burner.

TABLE 1 - Extinguishment of n-Heptane Diffusion Flame

Agent Air Flow Agent Flow FEC (cc/min) (cc/min) (% v/v) difluoromethyl-2, 2,2- 8,687 1, 121 11.7 trifluoroethyl ether¹ heptafluoropropyl-1,2,2,2- 6,373 247 3.7 tetrafluoroethyl ether¹ perfluoro-2- 6,373 224 3.5 butyltetrahydrofuran¹

CF,CFHCF₃ ² 16,200 1,506 9.3

CF₃CF₂H² 16,200 1,033 6.4 perfluoro-tetrahydrofuran³ 16, 000 1, 241 7.2 trifluoromethyl- 16, 000 1, 506 8.6 difluoromethyl ether³

HALON 13Ol⁴ 16,200 510 3.1

HALON 1211" 16,200 546 3.4

¹ indicates compounds of the present invention indicates compounds described in U.S. Patent No. 5,124,053

³ indicates compounds described by Adcock et al .

⁴ standard commercial Halons

The residue level of difluoromethyl-2 , 2 , 2- trifluoroethyl ether, heptafluoropropyl - 1 , 2 , 2 , 2 - t e t raf 1 uoroe t hy1 ether, and perfluoro-2- butyltetrahydrofuran were experimentally measured using a method recommended by NIST (NIST Technical Note 1278) . Namely, the measurements were performed by filling 1 cc of the fluids in a crucible that had previously been cleaned and weighed. The agent was then heated and allowed to evaporate. The weight percent residue of the agent was then calculated from the weight of the crucible before and after the test. Difluoromethyl-2 , 2 , 2-trifluoroethyl ether was found to have a residue of 0.02% (w/w) , heptafluoropropyl-1, 2 , 2 , 2-tetrafluoroethyl ether had a measured residue of 0.00% (w/w) , and perfluoro-2- butyltetrahydrofuran was found to have a residue level of 0.00% (w/w) . These levels are acceptable for fire suppression agents according to NIST (NIST Technical Note 1278) . In any case, it is desirable that the residue level of the fluorinated ether be no more than about 1.00% (w/w) .

The materials compatibility of difluoromethyl-2, 2, 2- trifluoroethyl ether, heptafluoropropyl-1 , 2 , 2 , 2- tetraf luoroethyl ether, and perfluoro-2- butyltetrahydrofuran with metals and nonmetals were experimentally demonstrated using an ASTM-derived method and found to be acceptable. The test apparatus was a thick-walled glass pressure tube that had a glass thread at the top and a threaded plunger valve that allowed for evacuating the tube and charging the tube with another fluid under pressure. The tube was 17.8 cm in length and had an OD (outside diameter) of 25.4 mm. The metals and nonmetals tested were Nitronic 40, copper CDA 172, aluminum 6061-T6, 1020 alloy steel, Teflon TFE, silicon rubber, Buna-N, and Viton. Circular coupons of these materials had been procured that measure 1/2" OD, 1/16" thick, with a 9/64" OD hole in the center. A Teflon rod passed through this hole and suspended the coupon, small Teflon spacers separated the coupons on the Teflon rod. Two coupons from each material were mounted on the Teflon rod and placed in the test container. The tube with the test samples was then evacuated and charged with the candidate agent so that each of the test coupons was covered with liquid agent. The test time was set for one month, and the test temperature was set at room temperature .

Each metal coupon was cleaned ultrasonically with acetone and isopropanol, dried, and weighed to the nearest 0.1 mg prior to mounting on the Teflon rod. After the test, the metal coupons were cleaned, examined under a microscope, and weighed to determine the corrosion rate according to the equation below. mil \__ ⁵ • 35x1 0⁵ ( w_i -w_f

Corrosi on ra te year j A td

where: w_i= initial weight (g) w_f= final weight (g)

A = area of coupon (in ) t = time (h)

D = metal density (g/ml)

The nonmetal samples were cleaned prior to the test in a soap/water solution, dried, and weighed to the nearest 0.1 mg prior to mounting on the Teflon rod. After the test the nonmetal coupons were cleaned, examined under a microscope, and their dimensions were measured with a micrometer to determine if any swelling had occurred.

Tables 2 and 3 present the results of these materials compatibility tests. In Table 2, which presents the results of the materials compatibility tests for the metals, the corrosion rates listed are average values for the two metal samples of each material. The values with a "less-than" ("<") symbol correspond to a mass change less than the sensitivity of the balance (± 0.1 mg) . Table 3 presents the results of the materials compatibility tests for the nonmetal samples tested. A compatibility rating was defined based on the percentage change in the thickness of the sample before and after the test . Mass changes and diameter changes of the sample were also measured during the test, and were found to correlate highly with the change in sample thickness. Percent mass changes correlated to percent thickness changes by an average factor of 6.1 (R²=0.96) , percent diametric changes correlated to percent thickness changes by an average factor of 0.57 (R =0.92) . TABLE 2 - Corrosion Rates (mm/year x 10⁴) with Metals

Agent 1020 AL CU CDA Nitronic Steel 6061-T6 172 40 difluoromethyl-2, 2,2- 169 21.1 81.1 3.58 trifluoroethyl ether heptafluoropropyl- <1.85 <10.6 <31.7 21.5 1,2,2, 2-tetrafluoroethyl ether perfluoro-2- 85 <10.6 63.4 <3.58 butyltetrahydrofuran

TABLE 3 - Materials Compatibility Results for Nonmetals

Agent Buna-N Silicon Viton Teflon Rubber difluoromethyl-2, 2,2- B C D A trifluoroethyl ether heptafluoropropyl-1,2,2,2- A B C B tetrafluoroethyl ether perfluoro-2- A C A B butyltetrahydro uran

A: negligible effect (0-2% thickness change)

B: minor effect (2-5% thickness change)

C: moderate effect (5-15% thickness change)

D: severe effect (>15% thickness change and/or breakage) j

The toxicity characteristics of difluoromethyl-2 , 2, 2- trifluoroethyl ether, heptafluoropropyl-1 , 2 , 2 , 2- tetraf 1uoroethy1 ether, and perfluoro-2- butyltetrahydrofuran were also estimated using structural property relations. Accordingly, the 4-hour lethal concentration (LC₅₀) for difluoromethyl-2, 2, 2-trifluoroethyl ether, heptafluoropropyl-1, 2, 2, 2-tetrafluoroethyl ether, and perfluoro-2-butyltetrahydrofuran was estimated to be 2.7, 2.5, and 12.4% (v/v) , respectively. Similarly, the cardiac sensitization "no observable adverse effect level" was estimated to be 7.5, 21.6, and 6.5% (v/v) , respectively. Moreover, the low toxicity of perfluoro-2- butyltetrahydrofuran might also be inferred from its prior use as a blood substitute (see NIST Technical Note 1279) . Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.

Claims

What is claimed is :

1. A method of extinguishing a fire, comprising the steps of introducing to the fire a fire extinguishing composition consisting of at least one fluorinated ether selected from the group consisting of fully fluorinated and partially fluorinated ether having the formula

C_xF_yH₂0,

where x is equal to or greater than 2 and less than or equal to 8 , w is greater than zero, y is between or equal to 2x-z and 2x+2-z, and z is 0, 1, 2 or 3 ,

and maintaining a concentration sufficient to extinguish the fire.

2. The method of claim 1, wherein the fluorinated ether is selected from the group consisting of difluoromethyl-2 , 2 , 2 -trif luoroethyl ether, heptaf luoropropyl-1 , 2 , 2 , 2-tetraf luoroethyl ether, and perf luoro- 2 -butyltetrahydrofuran.

3. The method of claim 1, wherein the composition is a mixture of at least two fluorinated ethers .

4. The method of claim 3, wherein each of the fluorinated ethers is selected from the group consisting of difluoromethyl-2 , 2 , 2-trifluoroethyl ether, heptaf luoropropyl -1 , 2 , 2 , 2-tetraf luoroethyl ether, and perf luoro- 2 -butyltetrahydrofuran .

5. A method of extinguishing a fire, comprising the steps of introducing to the fire a fire extinguishing composition consisting of at least one fully fluorinated or partially fluorinated ether having the formula ^Cx^Fy^HzC

where x is equal to or greater than 2 and less than or equal to 8, w is greater than zero, y is between or equal to 2x-z and 2x+2-z, and z is 0, 1, 2 or 3, and

at least one conventional fire extinguishing agent,

and maintaining a concentration sufficient to extinguish the fire.

6. A method of extinguishing a fire, comprising the steps of introducing to the fire a fire extinguishing composition consisting of at least one fully fluorinated or partially fluorinated ether having the formula

CχFyH-0,

where x is equal to or greater than 2 and less than or equal to 8, w is greater than zero, y is between or equal to 2x-z and 2x+2-z, and z is 0, 1, 2 or 3 , and

at least one saturated or unsaturated perf luorocarbon,

and maintaining a concentration sufficient to extinguish the fire.

7. The method of claim 5, wherein the fluorinated ether is selected from the group consisting of difluoromethyl-2 , 2 , 2-trifluoroethyl ether, heptaf luoropropyl-1, 2 , 2 , 2-tetraf luoroethyl ether, and perf luoro -2 -butyltetrahydrof ran.

8. The method of claim 6, wherein the fluorinated ether is selected from the group consisting of difluoromethyl-2 , 2 , 2-trif luoroethyl ether, heptafluoropropyl-l, 2, 2, 2-tetrafluoroethyl ether, and perfluoro-2-butyltetrahydrofuran.

9. The method of claim 1, wherein the step of introducing to the fire the fire extinguishing composition comprises introduction by total flooding.

10. The method of claim 1, wherein the step of introducing to the fire the fire extinguishing composition comprises introduction by streaming.

11. The method of claim 1, wherein the step of introducing to the fire the fire extinguishing composition occurs in an enclosed region.

12. The method of claim 1, wherein the step of introducing to the fire the fire extinguishing composition includes using an inert gas to pressurize the composition sufficiently to maintain an adequate flow of the composition toward the fire.

13. The method of claim 1, wherein the fluorinated ether has a residue of no more than about 1.00% (w/w) .

14. The method of claim 1, wherein the fire extinguishing composition is compatible with metals and nonmetals .

15. The method of claim 4, wherein the fluorinated ether has a concentration of at most about 11.7% (v/v) .

16. The method of claim 15, wherein the concentration is less than about 6.9% (v/v) .

17. The method of claim 1, wherein the step of introducing to the fire the fire extinguishing composition includes using an inert gas to pressurize the composition sufficiently to maintain an adequate flow of the composition toward the fire.

18. The method of claim 1, wherein the step of introducing to the fire the fire extinguishing composition includes providing the composition in a portable fire extinguishing equipment.

19. A method of using at least one fluorinated ether having the formula C_xF_yH_z0_w, where x is equal to or greater than 2 and less than or equal to 8, w is greater than zero, y is between or equal to 2x-z and 2x+2-z, and z is 0, 1, 2 or 3, comprising the step of incorporating an effective amount of the composition to a fire until the fire is extinguished.

20. The method of claim 19, wherein the fluorinated ether is selected from the group consisting of difluoromethyl-2 , 2 , 2-trifluoroethyl ether, heptafluoropropyl-1, 2 , 2 , 2-tetrafluoroethyl ether, and perfluoro-2-butyltetrahydrofuran.

21. The method of claim 19, wherein the fluorinated ether has a concentration of at most about 10% (v/v) .

22. The method of claim 19, wherein the fluorinated ether has a residue of no more than about 1.00% (w/w) .