CA2233657A1

CA2233657A1 - Solvent system

Info

Publication number: CA2233657A1
Application number: CA002233657A
Authority: CA
Inventors: William E. Moehle; Burnell Lee
Original assignee: Individual
Current assignee: Albemarle Corp
Priority date: 1995-11-01
Filing date: 1996-10-15
Publication date: 1997-05-09
Also published as: EP0858521A1; JPH11514704A; US5665170A; WO1997016583A1

Abstract

This invention relates to non-stabilized or at least only lightly stabilized npropyl bromide-based solvent systems which are suitable for use in the presence of metals which normally and easily catalyze the dehydrobromination of brominated hydrocarbons, such as isopropyl bromide.

Description

CA 022336~7 1998-03-31 SOLVENT CLEANING PROCESS

Back~round of the Invention:
This invention relates to the sf~ tion of n-propyl bromide against the corrosion of metals in contact therewith.
n-Propyl bromide has long been recognized as a solvent suitable for degreasing and cleaning metal and plastic articles.
See ~i~k-O~hm~r~n~,yclopec~ia oJ~hen~icai 7~o~ c)k>gy, 3Id Edi~ion, Vol. 4, Page ~57, ~ohn Wiley & Sons Inc., 1978. Also, see European Patent Application No. 0 609 004 Al which C]C.S~ the use of n-propyl bromide as a deterging solvent suitable for use in metal degreasing appli~tion~. The '004 application additionally notes that bromin~ted hydrocarbons, e.g., n-propyl bromide, are inferior to chlorofluorocarbons and chlorocarbons with respect to çhemi~l stability, i.e., their corrosive effects on certain metals.
Halo~on~ted solvents are notorious for being corrosive to metals such as ~ mimlmm~gnesi~m and tit~ni1lm These metals appear to catalyze the dehydrohalogenation of the l~ solvent, which dehydrohalogenation produces halogen acid which in turn attacks the metal, severely corroding it. It has been conventionally taught that bromin~ted solvents, such as n-propyl bromide and isoplol,yl bromide, are corrosive to metals even at ambient temperatures and that they need to be stabilized with more than 0. l wt% stabilizer Typical stabilizers are nitro~lk~nl~, ethers, epoxides and amines See European Patent Application No. 0 609 004 It would be desirable if n-propyl bromide could be stabilized with stabilizer amounts less than 0. l wt% even at temperatures up to and in~ flin~ the boiling point (71~ C) of n-propyl bromide. It would also be desirable if it were discovered than at temperatures up to and below 60~ C that n-propyl bromide did not need any stabilization whatsoever. In either case, savings are realized on the reduction ofthe amount or complete ~limin~tion of stabilizer needed.

The Invention:
This invention relates to a process for cleaning an article, which process comprises:

CA 022336~7 1998-03-31 (a) cont~ctin~ the article for up to twenty-four (24) hours with unstabilized n-propyl bromide at a temperature up to 60~ C in the presence of a metal which catalyzes the dehydl ~bl u~ Lion of isopropyl bromide at such temperature.
This invention also relates to a process for rle~ning an article, which process colll~lises:
S (a) cQnt~cting the article for up to twenty-four (24) hours with n-propyl bromide in the presence of a metal which catalyzes the deh~dl ~l ~n~ a~ion of n-propyl bromide at a t~;nl~ ure within the range offrom 60 to 71~ C, the n-propyl bromide being stabilized against deh~dlol)lul~ ion ~th less ~han n 1 wt~/~ st~hi).izer.
It has now been discovered that unlike most all other bl~ln;"~iecl lower alkanes, n-propyl 10 bromide is not nearly as corrosive of metals even at high temperatures over long periods of time. As a result of this discovery, it is now possible to confidently stabilize n-propyl bromide with amounts of stabilizer heretofore not believed possible. Further, this discovery makes possible the marketing of unstabilized n-propyl bromide for use at temperatures lower than 60~ C without concem for metal corrosion. The term '~unstabilized n-propyl bromide" is used 15 to connote that those compounds normally thought of as stabilizers for n-propyl bromide are not present in the solvent system or are not present in the solvent system in a stabilizing function.
The .ct~hili7in~ function is applied in the context of washing an article at a temperature at or below 60~ C for a period of time under twenty-four (24) hours. As can be seen from the following Ex~mplç~, for such a washing, n-propyl bromide is not in need of stabilization and, 20 thus, cannot be the subject of stabilization whether stabilizers are present or not. Of course, it is most preferred that the solvent system be e~.s~nti~lly free of slalJili~ or that none be added thereto. A solvent system in which no solvent is present or in which only very minor non-fim~tic~n~l amounts are present is preferred as there is, at the very least, a cost savings realized.
The prior art reports that stabilizer functional amounts exceed 0.1 wt% and that lesser amounts 25 are not functional.
The metal referred to in the above is any metal capable of catalyzing the dehydrobro-min~tion of isopropyl bromide under the recited conditions. Exemplary metals are ~lnminllm, m~gn~ m and tit~nillm which may be the sole metal or which may be present as a con~titu~nt metal in an aUoy or ~m~lg~m Isopropyl bromide is chosen to indicate the dehydrobromination 30 activity of the metal as it is an isomer of n-propyl bromide and it exemplifies typical dehydrobro-minationofb,o",;,.~t~dcompoundsinthepresenceofsuchmetals. Thus,ifisopropylbromide CA 022336',7 1998-03-31 W O 97/16583 PCTrUS96/16452 experiences dehydroblo~ n in the presence of a metal, then that metal can be considered to offer a potential catalytic effect towards other bromin~ted species.
Corrosion offresh ~ mimlm by nearly pure n-propyl bromide does not occur until the temperature is above 60~ C and the exposure time is twenty-four (24) hours. At ambient 5 temperatures, little or no corrosion is seen. Thus, for exposure to temperatures less than 60~
C, there is no need for stabilization of the n-propyl bromide. At higher temperatures, which are equal to or higher than 60~ C and up to 71~ C, less than 0. I wt% stabilizer is needed to ~ttenu~te the corrosive eff.e~. t of n-pronyl bromide Pref.erre(1 arrlol.lnts of sta.bilizer range from 0.05 to less than 0.1 wt%. Most preferred are ~m('~nnt~ within the range of from 0.05 to 0.09 10 wt%. (The wt% is based upon the total weight of stabilizer and n-propyl bromide.) Any of the conventional stabilizers which are taught by the art to be useful in stabilizing halogenated hydrocarbon solvents are suitable for the purposes of this invention. The stabilizer may be a simple stabilizer or a cc,~ il.dlion of stabilizers. The stabilizers can be nitro~lksmf~, ethers, epoxides, amines or any co..~ -dlion thereof Preferred are the nitroalkanes, epoxides and co---bindlions thereof.
The nitroalkanes usable in the present invention include nitromethane, nitroethane, 1-nilloplupane, 2-nillop~upane and nitrobenzene. Preferred is nitromethane. They are usable either singly or in form of a mixture of two or more of them.
The ethers include 1,2-dimethyoxyethane, 1,4-dioxane, 1,3-dioxalane, diethyl ether, diisopropyl ether, dibutyl ether, trioxane, alkyl cellosolves in which the alkyl yroup has 1 to 10 carbon atoms such as methyl cellosolve, ethyl cellosolve and isopropyl cellosolve, acetal, acetone dimethyl acetal, y-butyrolactone, methyl t-butyl ether, tetrahydrofuran and N-methylpyrrole. They are usable either singularly or in the form of a mixture of two or more of them.
The epoxides include epichlorohydrin, propylene oxide, butylene oxide, cyclohexene oxide, glycidyl methyl ether, glycidyl methacrylate, pentene oxide, cyclopentene oxide and cyclohexene oxide. P,~relled is 1,2-epoxybutane. They are usable either singularly or in the form of a mixture of two or more of them.
The amines include hexylamine, octylamine, 2-ethylhexylamine, dodecylamine, ethylbutylamine, hexylmethylamine, butyloctylamine, dibutylamine, octadecylmethylamine, triethylamine, tributylamine, diethyloctylamine, tetradecyldimethylamine, diisobutylamine, CA 022336~7 1998-03-31 W O 97/16583 PCTrUS96/16452 diisopropylamine, petnylamine, N-methylmorpholine, isopropylamine, cyclohexylamine, butylamine, isobutylamine, dipropylamine, 2,2,2,6-tetramethylpiperidine, N,N-di-allyl-p-phenylPn(?~ min~, diallyamine, aniline, ethylen~ minç, propyl~n~ mine, diethylenetriarnine, tetraethylenep~.nt~min~, ben_ylamine, dibenzylamine, diphenylamine and diethylhydroxyamine.
5 They are usable either singularly or in the form of a mixture of two or more of them.
When d.oci~ning a solvent system of this invention for general use, it would be prudent to include the small amount of stabilizer mentioned above as the end-use temperature of the solvent svstern mav ~ceed 60~ C. If 5 on the other hand the practitioner knew that the end-use would not exceed 60~ C for twenty-four (24) hours, then the solvent system would not require 10 the use of a stabilizer for the n-propyl bromide.
Since it is only the n-propyl bromide that is the focus of the stabilization aspects of this invention, it should be understood that if other halogenated hydrocarbons are co-present with the n-propyl bromide, then those hydrocarbons will need to be stabilized in accordance with the significance of their presence. In the production of n-propyl bromide, there can be co-l~i produced minor amounts of other bromin~ted propanes, especially isopropyl bromide. If thepresence of these other bl ~ll~in~Led propanes is not ~tt~nl ~~te-l then their corrosive nature has to be accounted for and, if deemed n~cç~ry, stabilizer used. The amount of stabilizer used to st~hili7P. these other b,~),.lin~d propanes can be the conventional amount, e.g., from above 0.1 wt% to 15 wt%, with the wt% being based upon the total weight of the other bromin~ted 20 propane and stabilizer used for that particular bromin~te-l propane.
Generally, crude n-propyl bromide product will be 99+ wt% bromin~ted propane, 90wt% being n-propyl and the r~.m~in~l~.r being 10 to 0 wt% other bromin~ted propanes and very minor amounts of impurities. The impurities that may be found are exemplified by n-propanol, isopropanol, diisopropyl ether, di-n-propyl ether, butyl bromide, and ethyl bromide. The 25 impurities generally account for no more than 0.2 wt% of the n-propyl bromide product.
Plt;r~ d processes produce a crude n-propyl bromide product cont~ining at least 94-96 wt%
n-propyl bromide and 4-6 wt% isopropyl bromide and very minor amounts of other impurities, be they b,~J",i~ ed compounds or not. Purified n-propyl bromide can contain at least 98 wt%
n-propyl bromide and preferred, high purity n-propyl bromide can contain 99+ wt% n-propyl 30 bromide with the rçm~in~l~r being isopropyl bromide and other impurities. As an example, a crude n-propyl bromide product co"Lai~f~lg 95 wt% and 4.5 wt% isopropyl bromide and being CA 022336~7 1998-03-31 W O 97/16583 PCT~US96tl6452 used at a tell~el~ re less than 60~ C, would not need stabilizer for the n-propyl bromide but would need, say S wt%, ~l~il~t;l for the isopropyl bromide. (This last wt% being based upon the total weight of isopropyl bromide and stabilizer used.) Thus, the total stabilizer loading forthewhole ofthe crude product would only be 5 w+.% ofthe 4.5 wt% or only 0.237 wt%
S ~al~iliGel, based upon the total weight of crude product and stabilizer. As can be appreciated such a loading is extremely low and would be of economic and, perhaps, toxicological advantage. If the crude product is dçctin~ for use at say 7 l ~ C, then the total loading would the ~ nve (!.237 wt% plll~ the less than () 1 w~% used ts~.stahili~e thç n-pr- pvl bromide When using purified n-propyl bromide, say 98 wt% n-propyl bromide or above, the 10 amount of other b~- lnill~led propanes may be so low in the destined use that the ~ignific~nce of their corrosive effect may be inconsequential and, thus, there may be no need in taking into account these blull~ill~Led propanes for corrosion purposes. This phenomena is clearly evident in the for 99.5 wt% n-propyl bromide. In this case, the product would be stabilized in accordance with this invention as if it were 100 wt% n-propyl bromide.
It is also to be understood that n-propyl bromide may be used in combination with a halogenated co-solvent, such as bromochloromt-th~n~, 1,1,1-trichloroethane, tri- and perchloro-ethylene, n-butyl bromide, isobutyl bromide, n-amyl bromide, n-decyl bromide, allyl bromide, hexylene bromide and generally most other solvents of the formula CnH2n+, ~ X~ or CmH2m 2 ~
X~wherein n is 3 to lO and m is 2 to 10 and a is 1,2 or 3 and X is chlorine or bromine. It is 20 ~ rell t;d that X be exclusively bromine. Irrespective of the co-solvent used, its needs for stabilization will need to be met. However, once again, the n-propyl bromide's stabilization needs need only be met in accordance with this invention.
Non-halog~.n~tecl co-solvents may also be used in combination with n-propyl bromide and may be of ~ignific~nt benefit as most should not need stabilization as is generally required 25 ofthe non-n-propyl bromide halogenated co-solvents. Such non-halog~n~tçd co-solvents include those hydrocarbons having a solvent utility in combination with n-propyl bromide. By the term "hydrocarbon", it is meant a compound which co~ ;"~ e~ nti~lly all hydrogen and carbon con~fitu~nt~ except that it may also contain some oxygen, sulfur and/or nitrogen con~tituçnt~.
The solvent utility COIIC~;I IlS mainly solvating fats, waxes, resins, greases, and oils. Exemplary 30 hydrocarbons are hexane, benzene, toluene, cyclohexane, terpenes, such as pinene, limonene, carene, and c~mph.o.n~, acetone, meth~n~-l ethanol, isopropanol, methylethyl ketone and mixtures CA 022336~7 1998-03-31 W O 97/16583 PCT~US96/164~2 of any two or more of the foregoing. Generally, the co-solvent hydrocarbons can be found in the following classes: alkanes, alkenes, cyclo~lk~nes, cycloalkenes, aromatics, alcohols, ketones, esters, ethers, amines, mineral oils and derivatives and mixtures of the rOI eg~ g. Most pl erel I ed of the non-halog~n~ted co-solvents are hexane and the terpenes.
Irrespective of whether or not the co-solvent is halogenated, generally it will comprise from 10 to 90 wt% ofthe co-solvent system, with the balance of solvent being n-propyl bromide.
If the co-solvent is a non-h~log~n~ted hydrocarbon solvent, then the only stabilization generally neçded ~.ll b~. that pr~iously descnbed for n-r ropy] bromide product. Generally ~he co-solvent will be present in an amount within the range of from 25 to 75 wt%, and preferably within the range of from 40 to 60 wt%. The wt% for the co-solvent/n-propyl bromide combination is based upon the total weight of solvent present.
The n-propyl bromide-based solvents ofthis invention are particularly useful in deterging metal products and electronic parts. The product or part can be dipped in the solvent system which is at a temperature below its boiling point. Also, the solvent systems of this invention can be used as a vapor to effect cleansing of the products or parts. In general, the solvent systems ofthis invention are suitable for use in all those applications which have been found suitable for chlorinated hydrocarbon solvents, e.g., 1,1, l-trichloroethane, trichloroethylene, and perchloroethylene. It is a particular benefit of the solvent systems of this invention that they function well without or at least with reduced amounts of stabilizer than is taught by the prior art.
In describing the temperature at which the solvent systems of this may be used, it is noted that most degreasing and ~le~ning operations are operated at atmospheric pressure. At atmospheric pressure the boiling point will be 71~ C depending upon the elevation ofthe operation's location. Thus, vapor operations will also occur within the 7 l ~ C range. Pressurized operations may also be used and it would be expected that the stabilizer requirements of this invention would apply to temperatures up to 80-85~ C

Even though the contact time mentioned for the processes of this invention is described as being twenty-four (24) hours or less, it is generally desirable that the contact time be kept to a minimnm The preferred contact times are six (6) hours or less with a contact time of less than one (1) hour being most preferred. Depending upon the cleaning duty prescribed for the solvent systems ofthis invention, contact times less than 0.5 hours may also be suitable. If the artide to be cleaned is not heavily soiled, contact times of less than ten (10) minutes may be sufflcient.
EXAMPLES
The following tests were run by i~ el 7hlg scratched ~ mim~m strips in a beaker filled with 99.5 wt% pure n-propyl bromide. The n-propyl bromide was kept at the indicated tt;~ e ~ re for twenty-four (24) hours unless observable corrosion was observed. The lapsed ~:ime t~~ the o~servatiQn of colTosion was noted In some of the tests. stabili7er ~vas ad~1ed ~o the pure n-propyl bromide. The identity and quantity of the stabilizer is noted in the Table.
10 The wt% ~ t;- was based upon the total amount of n-propyl bromide and stabilizer present.

Examples I-VIII
ExampleNo. Stabilizer Temperature (~ C! Observation none 5 5 no corrosion after 24 hrs II none 60 no corrosion after 24 hrs III none 65 corrosion after 12 hrs IV none 71 corrosion after 4 hrs V 0.09 wt% nitromethane71 no corrosion after 24 hrs VI 0.05 wt% nitrometh~ne71 nocorrosionafter24hrs VII 0.09 wt% 1,2-epoxybutane 71 nocorrosionafter24hrs VIII 0.045 wt% nitromethane 71 nocorrosionafter24hrs 0.045 wt% 1,2-epoxybutane

Claims

1. A process for cleaning an article, which process comprises:
(a) contacting the article for up to twenty-four (24) hours with unstabilized n-propyl bromide at a temperature up to 60°C in the presence of a metal which catalyzes the dehydrobromination of isopropyl bromide at such temperature.

2. The process of Claim 1 wherein the temperature is within the range of from 20 to 60° C.

3. The process of Claim 1 wherein the metal is aluminum, magnesium or titanium.

4. The process of Claim 1 wherein the contacting occurs over a period of time less than twenty-four (24) hours.

5. A process for cleaning an article, which process comprises:
(a) contacting the article for up to twenty-four (24) hours with stabilized n-propyl bromide in the presence of a metal which catalyzes the dehydrobromination of n-propyl bromide at a temperature within the range of from 60 to 71° C, the n-propyl bromide being stabilized against dehydrobromination with less than 0.1 wt% stabilizer.

6. The process of Claim 5 wherein the contacting occurs at a temperature up to the sea-level boiling point of n-propyl bromide.

7. The process of Claim 5 wherein the metal is aluminum, magnesium or titanium.

8. The process of Claim 5 wherein the contacting occurs over a period of time less than twenty-four (24) hours.

9. The process of Claim 5 wherein the stabilizer is present in an amount within the range of from 0.05 to less than 0.1 wt%.

10. The process of Claim 5 where the stabilizer comprises nitromethane, 1,2-epoxybutane or a mixture thereof.

11. The process of Claim 5 wherein the stabilizer comprises from 0.045 to less than 0.09 wt% stabilizer.