STABILIZED BROMINATED ALKANE SOLVENT

Abstract: A stabilized solvent composition which is comprised of: a solvent portion which includes at least 90 wt.% n-propyl bromide; and a 1,4-dioxane-free stabilizer system which includes nitroalkane, 1,2-butylene oxide and 1,3-dioxolane. The solvent composition is useful as a degreaser and cleaner in both cold and vapor cleaning systems.

Description: STABILIZED BROMINATED ALKANE SOLVENT Background of the Invention: This invention relates to a novel, high performance solvent composition based upon a brominated alkane solvent and a 1 ,4-dioxane-free stabilizer system. The degreasing and cleaning industries are presently facing a ban on the use of 1 , 1 , 1 - trichloroethane (TCE) as a deterging solvent. The ban is based upon 1,1,1-trichloethane's relatively high ODP (Ozone Depletion Potential). Several alternatives have been suggested, but most have been rejected due to the lack of high solvent function, cost, toxicity, andflammability. One alternative, n-propyl bromide, looks to be ideal. It has a low and acceptable Ozone Depletion Potential. It has been shown that its solvent function is similar to that of 1,1,1 -trichloroethane and that it can be made relatively pure, say 99+ wt%, at an acceptable cost. Further, n-propyl bromide shows promise in toxicity tests. There is some confusion in the art as to its flammability, but recent testing has shown that it can be considered non-flammable. Experimental work shows that n-propyl bromide can be used in both cold and vapor cleaning systems. Surprisingly, it has been learned that n-propyl bromide is fairly stable when used at low temperatures, say temperatures up to 55° C. Tests have shown that in cold cleaning systems, n-propyl bromide needs little, if any, stabilization. However, if n-propyl bromide is used in vapor cleaning systems, then stabilization is necessary. The higher temperatures, say 69-71° C, can lead to the corrosion of metals such as steel, aluminum, titanium and magnesium. It is believed that the metal catalyzes the dehydrobromination of the n-propyl bromide to yield HBr which in turn is available to corrode the metal. The prior art is replete with stabilizers to attenuate the catalytic activity of the metal and/or to deactivate any hydrogen halide produced. The art is most instructive in the area that was of high interest, i.e., the area concerning chlorohydrocarbon solvents. Much less art is available in the area of bromohydrocarbon solvents. Due to the newly discovered attractiveness of brominated solvents, the art is just now vigorously investigating the selection of the best combination of brominated solvent and stabilizing system. The combination possibilities are innumerable, but the advantage will go to the discoverer of that ideal match between a particular brominated solvent and a particular stabilizing system. Not all of the old prior art solvent system components are now considered to be acceptable candidates due to present day concerns about health and the environment. For example, an old and very common stabilizing component, 1 ,4-dioxane, is not now favored due to health concerns. It is, therefore, an object of this invention to provide a degreasing and cleaning solvent which is highly efficacious and which is friendly to both the user and the environment. The Invention: This invention relates to a stabilized degreasing and cleaning solvent composition which is comprised of a solvent portion which includes at least 90 wt% n-propyl bromide; and a 1 ,4- dioxane-free stabilizer system which includes nitroalkane, 1 ,2-butylene oxide and 1 ,3-dioxolane composition. Except as indicated to be otherwise, the wt% and ppm values used herein are based upon the total weight of the solvent composition. Preferably, the n-propyl bromide is supplied to the composition as 99+ wt% n-propyl bromide, with the most common impurity being iso-propyl bromide. The wt% and ppm recited in this paragraph are based on the total weight of n-propyl bromide and impurities. Commercially suitable n-propyl bromide may be accompanied by as much as 6 wt% iso-propyl bromide. n-Propyl bromide of much less purity is permissible, but not desired. The iso-propyl bromide impurity is naturally found in the raw n-propyl bromide product, but its presence can be attenuated by distillation. It is not a benign impurity as it is very much less stable than n- propyl bromide and, thus, can result in aggressive corrosion. A typical raw n-propyl bromide product will contain 96 wt% n-propyl bromide and 4 wt% iso-propyl bromide. For vapor degreasing and cleaning, the preferred iso-propyl bromide content will be kept low, say within the range of from 0.01 to 0.5 wt%. n-Propyl bromide can be purchased commercially from Albemarle Corporation, Richmond, Virginia. The solvent system is, as before noted, 1 ,4-dioxane-free, that is, it comprises no more than an impurity amount of the solvent composition, say less than 500 ppm. It is preferred that no 1 ,4-dioxane whatsoever be present in the solvent composition. The nitroalkane constituent of the solvent system preferably is nitromethane, nitroethane or mixtures thereof. The most preferred is nitromethane. The amount of nitroalkane used will generally be within the range of from 0.045 to 1.0 wt%. A preferred amount will be within the range of from 0.25 to 1.0 wt% and most preferably from 0.3 to 0.6 wt%. The 1 ,2-butylene oxide constituent will be generally present in an amount within the range of from 0.045 to 1.0 wt%, and preferably present within the range of from 0.25 wt% to 1.0 wt% and most preferably from 0.3 to 0.6 wt%. Amounts within the range of from 0.1 to 10.0 wt% are suitable for the 1,3-dioxolane constituent. Preferred amounts are within the range of from 2.0 to 6.0 wt%. It is within the scope of this invention for the solvent compositions of this invention to be used in the presence of an in conjunction with other solvents or solvent systems and additives. For example, the solvent compositions of this invention can be mixed with a solvent such as hexane or n-butyl bromide. An exemplary additive is an anti-rust additive. The solvent composition of this invention may comprise from less than 50 to more than 90 wt% of the total weight of the solvent composition of this invention and the other solvent or solvent system or additive. Quantitatively, the solvent compositions of this invention, as before noted, will contain at least 90 wt% n-propyl bromide, with the balance including impurities, e.g., iso-propyl bromide, the stabilizer system of this invention, and any other additives desired by the practitioner. A typical solvent composition in which the n-propyl bromide used is not particularly pure, will contain 90-92 wt% n-propyl bromide, 4-6 wt% iso-propyl bromide, 0.25-1.0 wt% nitromethane, 0.25-1.0 wt% 1,2-butylene oxide and 2.0-6.0 wt% 1 ,3-dioxolane. If the n-propyl oxide is of high purity, then the n-propyl bromide could be 94-97 wt% of the solvent composition. The solvent compositions of this invention are suitable for use in cold cleaning applications and in vapor cleaning operations. The former, are generally characterized by immersion of the article to be cleaned in the solvent composition at a temperature which is usually within the range of from room temperature to 55° C. Vapor cleaning is characterized by passing the article to be cleaned through a vapor of the solvent composition, with the article at a temperature which causes condensation of the vapor on its surfaces. The condensate effects its cleaning function and then drips off. The vapor temperatures are generally approximate to the boiling point of the solvent composition, which in the instant case will be around 65 to 75° C depending upon the particular quantitative and qualitative identity of the solvent composition being used. For a solvent composition where the n-propyl bromide content is very high, say above 95 wt%, the boiling point will be around 69-72° C. The following illustrates the efficacious nature of a solvent composition of this invention. It is not intended for the Example to be taken, in any way, as limiting the scope of the inventions described herein. EXAMPLE A solvent composition was prepared by mixing the following ingredients together: 96.5 wt% n-propyl bromide 2.5 wt% 1,3-dioxolane 0.5 wt% 1,2-butylene oxide 0.5 wt% nitromethane Aluminum alloy (2024), magnesium (AZ-3 IB) and titanium (MIL-T-9046) test coupons were polished with emery cloth until bright, shiny and free of tarnish. The polished coupons were then washed with soap followed by rinsing with distilled water. The rinsed coupons were dried with acetone without being handled by bare hands. The dried coupons were then immersed in the solvent composition for 24 hours. The solvent composition was maintained at reflux during the immersion period. After the 24-hour period, the coupons were recovered, cooled and visually examined for corrosion. No corrosion was observed.

Claims: CLAIMS 1. A stabilized solvent composition which is comprised of: a solvent portion which includes at least 90 wt% n-propyl bromide; and a 1 ,4-dioxane-free stabilizer system portion which includes nitroalkane, 1,2-butylene oxide and 1,3-dioxolane. 2. The solvent composition of Claim 1 wherein the nitroalkane is nitromethane, nitroethane or a mixture thereof. 3. The solvent composition of Claim 1 wherein the nitroalkane is nitromethane. 4. The solvent composition of Claim 1 wherein the solvent portion includes 90 to 92 wt% n-propyl bromide. 5. The solvent composition of Claim 1 wherein the solvent portion includes 94 to 98 wt% n-propyl bromide. 6. The solvent composition of Claim 1 wherein the solvent portion includes 0.045 to 1.0 wt% nitroalkane, 0.045 to 1.0 wt% 1,2-butylene oxide and 2.0-6.0 wt% 1,3-dioxolane. 7. The solvent composition of Claim 6 wherein the solvent portion includes 90 to 92 wt% n-propyl bromide. 8. The solvent composition of Claim 6 wherein the solvent portion includes 94 to 98 wt% n-propyl bromide. 9. A process for cleaning an article which comprises immersing the article in a solvent composition comprised of a solvent portion which includes at least 90 wt% n-propyl bromide; and a 1 ,4-dioxane-free stabilizer system portion which includes nitroalkane, 1,2- butylene oxide and 1,3-dioxolane, said solvent composition being at a temperature within the range of from room temperature to 55° C. 10. A process for cleaning an article which comprises exposing the article to the vapor emanating from a boiling body of a solvent composition comprised of a solvent portion which includes at least 90 wt% n-propyl bromide; and a 1 ,4-dioxane-free stabilizer system portion which includes nitroalkane, 1,2-butylene oxide and 1 ,3-dioxolane.

Inventors: LEE BURNELL, RIDDLE JAMES M, LEE, BURNELL, RIDDLE, JAMES, M.
Applicants: ALBEMARLE CORP, ALBEMARLE CORPORATION
Application year: 1997
Main classification: C11D7
IPC codes: C11D7, C23G5