Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Reexamination Certificate
2000-06-16
2002-02-26
Anthony, Joseph D. (Department: 1714)
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
C252S405000, C252S407000, C252S390000, C252S394000, C252S396000, C510S265000, C510S266000, C510S273000, C570S109000, C570S110000, C570S111000, C570S114000, C570S121000
Reexamination Certificate
active
06350395
ABSTRACT:
The present invention concerns a stabilizer composition, particularly a stabilizer composition for halogenated hydrocarbons, such as perchloroethylene.
Halogenated hydrocarbons containing 1 to 3 carbon atoms, such as perchloroethylene, are used in several applications, such as dry-cleaning of textiles or degreasing of metals. However, it is well known that trichloroethylene or perchloroethylene tends to decompose when they are exposed to heat, oxygen, light or water, particularly if metals or metal salts are present. Mainly acidic products, such as hydrochloric acid, are produced during decomposition.
Therefore, it is common in the industry to add a stabilizer to halogenated hydrocarbons containing 1 to 3 carbon atoms, such as perchloroethylene.
German Offenlegungsschrift DE-A-24 49 667 (equivalent to U.S. Pat. No. 4,034,051) discloses that perchloroethylene is stabilized by the addition of 0.001 to 0.01 weight percent of an N-alkyl morpholine and 0.001 to 0.01 weight percent of an alkyl phenol.
German Offenlegungsschrift DE-A-32 46 886 relates to a process for stabilizing perchloroethylene wherein 1,2-epoxycyclooctane and/or 1,2-5,6-diepoxycyclooctane in addition to known epoxides, such as cyclohexene oxide, are added to perchloroethylene as stabilizers. Additionally amines, preferably triethylamine, diisopropylamine, dimethylisobutylamine, sec.-butylamine, pentylamine, isopentylamine, 5-methyl-2-hexane-amine, diisobutylamine, N-methylpyrrole or N-methyl morpholine can be used as stabilizers. Other stabilizers are ethers, such as dialkyl ethers, olefins, such as diisobutylene, or alkyl phenols, such as p-cresol.
German Offenlegungsschrift DE-A-39 22 135 relates to the use of cyclopentene oxide for stabilizing perchloroethylene. The same amines as in German Offenlegungsschrift DE-A-32 46 886 and alkyl phenols, such as p-cresol, o-cresol or p-tert.-butyl phenol are mentioned as additional stabilizers. A stabilizer mixture containing cyclopentene oxide, N-alkyl morpholine, diisopropylamine and alkyl phenol is said to be preferred.
German Offenlegungsschrift DE-A-28 11 779 relates to stabilized perchloroethylene which contains 0.001 to 0.01 weight percent of alkyl phenols, 0.0005 to 0.002 weight percent of diisopropylamine and 0.05 to 0.5 weight percent of cyclohexene oxide. DE-A-28 11 779 discloses that strong corrosion is observed with a stabilizer composition comprising aniline, N-methylmorpoline, p-tert.-butylphenol and cyclohexene oxide.
U.S. Pat. No. 3,424,805 suggests stabilization of chlorinated hydrocarbons by addition of an aliphatic diamine or polyamine. It is taught that the stabilizing effect can be increased by the addition of an aliphatic monoamine, such as diisopropylamine or pyrrole or N-alkyl pyrrole, such as N-methyl pyrrole. Unfortunately, the suggested amine combinations often do not provide satisfactory results for stabilizing perchloroethylene.
U.S. Pat. No. 4,942,267 discloses a stabilizer composition for perchloroethylene which comprises a cyclic alkyl amine, an alcohol of 3 to 7 carbon atoms and an olefin component. It mentions that the stabilizer composition may be combined with an aliphatic or aromatic amine, nitrogen containing materials, such as pyrroles, cyclic ethers and aromatic compounds containing a phenol group.
East German Patent 111 198 discloses a mixture of 20 to 160 g of thymol, 20 to 150 mL of triethanolamine, 20 to 150 mL of morpholine and 0 to 55 mL of triethylamine as a stabilizer per 1000 L of perchloroethylene. A mixture of 50 g of thymol, 45 mL of triethylamine, 30 mL of morpholine and 345 mL of trichloroethylene is suggested for stabilizing 1000 L of trichloroethylene. Unfortunately, when perchloroethylene or trichloroethylene containing triethanolamine as a stabilizer is used for degreasing non-ferrous heavy metals, such as copper, aluminum or brass, spots are left on the metals.
UK Patent Application GB 2 069 995 discloses a stabilizer for dichloromethane which contains methyl alcohol and small amounts of diisopropylamine and/or benzylethylamine and/or triethylamine.
Unfortunately, perchloroethylene which has been stabilized as suggested in the prior art above does not meet the requirements of the industry for many applications. Often the capacity of the stabilizer is reduced over time which is made apparent by a decrease of alkalinity of the stabilized perchloroethylene.
A new stabilizer composition has been found which is very effective for stabilizing halogenated hydrocarbons against decrease of alkalinity.
Accordingly, one aspect of the present invention is a stabilizer composition which comprises
a) an N-alkyl morpholine and
b) a straight-chain or cyclic aliphatic amine containing no heteroatoms other than N with a boiling point of at least 150° C.
Another aspect of the present invention is a stabilized halogenated hydrocarbon which comprises this stabilizer composition.
Yet another aspect of the present invention is a method of stabilizing a halogenated hydrocarbon against degradation by adding an effective amount of this stabilizer composition.
Yet another aspect of the present invention is the use as stabilizer for a halogenated hydrocarbon of a) an N-alkyl morpholine and b) a straight-chain or cyclic aliphatic amine containing no heteroatoms other than N with a boiling point of at least 150° C.
The accompanying
FIG. 1
illustrates the decrease of alkalinity of various perchloroethylenes stabilized according to the present invention and according to the prior art during distillation and recycling of the distillate over an extended period of time.
The stabilizer composition of the present invention preferably comprises
a) from 20 to 99, more preferably from 50 to 95, most preferably from 60 to 90 percent of an N-alkyl morpholine and
b) from 1 to 80, more preferably from 5 to 50, most preferably from 10 to 40 percent of a straight-chain or cyclic aliphatic amine containing no heteroatoms other than N with a boiling point of at least 150° C., based on the total weight of a) and b).
The alkyl group in the N-alkyl morpholine is preferably a straight-chain or branched alkyl group of from 1 to 6, more preferably 1 to 4, most preferably 1 to 3 carbon atoms, such as methyl, ethyl, n-propyl or isopropyl. The ethyl group and particularly the methyl group are preferred. The ring carbon atoms in the N-alkyl morpholines can be substituted, for example with alkyl groups of from 1 to 4 carbon atoms, preferably methyl. N-ethyl morpholine or, more preferably, N-methyl morpholine is the most preferred compound a) of the stabilizer composition of the present invention. The stabilizer composition of the present invention contains one or more N-alkyl morpholines.
The amine b) in the stabilizer composition of the present invention has a boiling point of at least 150° C., more preferably at least 160° C., most preferably at least 180° C., measured at atmospheric pressure. The amine b) contains no heteroatoms other than N. The amine can be a primary, secondary or tertiary straight-chain or cyclic aliphatic amine. Preferably, the amine is saturated. Secondary and tertiary amines are preferred. Mono-, di- or triamines are useful, provided that they have an above-mentioned boiling point. More preferably, the amine b) contains two or more amino groups. Preferably, the pKa of the amine b) is from 7.5 to 11, more preferably from 8 to 9.5. Particularly preferred amines are those with two amino groups of which the first pKa value is above 11 and the second pKa is from 7.5 to 11.
Preferred amines b) are 1-aminoheptane, n-octyl amine, tert.-octyl amine, tetramethylene diamine, hexamethylene diamine, 1,8-octane diamine, 4-aminomethyl-1,8-octane diamine, hexamethylene tetraamine, 1,4-diazabicyclo[2.2.2]octane, 1,3,5-triethylhexahydro-1,3,5-triazine or N,N,N′,N′,N″-pentamethyldiethylene-triamine. Of these amines 1,4-diazabicyclo[2.2.2]octane, 1,3,5-triethylhexahydro-1,3,5-triazine, N,N,N′,N′,N″-pentamethyldiethylene-triamine and 4-aminomethyl-1,8-octane diamine are the most preferred ones.
The stabiliz
Anthony Joseph D.
The Dow Chemical Company
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