Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/38—Separation; Purification; Stabilisation; Use of additives
  • C07C17/42—Use of additives, e.g. for stabilisation

Definitions

• This invention relates to inhibiting the decomposition of tetrachloroethylene catalyzed by light, air, heat, moisture, and metal surfaces and more particularly relates to a composition of matter consisting essentially of tetrachloroethylene and stabilizing amounts of an acetylenic ether.
• tetrachloroethylene perchloroethylene
• perchloroethylene perchloroethylene
• tetrachloroethylene perchloroethylene
• the obtaining of such high purity tetrachlorethylene in commercial production is not generally feasible and it has been found that the impure material normally encountered incommerce decomposes when in contact with the substances noted above.
• means other than purification for preventing or inhibiting the decomposition of tetrachloroethylene and the lower chlorinated aliphatic hydrocarbons generally associated therewith must be had.
• tetrachloroethylene exposed to air, light, heat, moisture, etc. decomposes, especially in the presence of moisture, principally by way of. oxidative attack at the double bond involving a series of steps in which the ultimate products include phosgene, trichloroacetic acid, and hydrogen chloride. Itis also believed that the oxidative attack is catalyzed by light and by the products of oxidation, as a result of which, oxidative decomposition once initiated is self-catalyzing and self-sustaining.
• chloro-hydrocarbons generally associated with crude commercial tetrachloroethylene also are subject to oxidative attack and decompose to some of the same products as those formed by the oxidation of tetrachloroethylene, and at a somewhat accelerated rate, as compared to the oxidation of tetrachloroethylene. These products are then available to catalyze the decomposition of the tetrachloroethylene.
• tetrachloroethylene obtained commercially from the crude products of chlorination and chlorinolysis of lower aliphatic hydrocarbons may contain small but appreciable amounts of saturated and unsaturated chlorinated hydrocarbons, such as dichloroethylene, trichloroethylene, trichloroethane, unsymmetrical tetrachloroethane, pentachloroethane, and the like.
• chloro-hydrocarbons in themselves are relatively innocuous in solvent extraction processes in which the tetrachloroethylene is used, but the oxidation decomposition products thereof corrode metal surfaces'with which a body of tetrachloro-
• chloro oxygen-containingimpurities such as phosgene, chloroacetic acid, trichloroacetic acid, and the like, in the tetrachloroethylene, which imporities catalyze decomposition of the tetrachloroethylene.
• the problem is principally one of inhibiting theinitiation of the oxidation of the .chlorohydroearbons commonly associated with commercial tetrachloroethyllice 2 ene, as well as inhibiting the oxidation of tetra-chloroethylene itself.
• One of the objects of the present invention is to provide means for inhibiting oxidation of tetrachloroethylene and lower aliphatic chloro-hydrocarbons generally asso- .ciated therewith during exposure to air, light, heat, moisture, and metal surfaces.
• stabilizing chlorinated solvents it has been found desirable to employ a pair of stabilizing ingredients, one for the general purpose of stabilizing the solvent against the effects of air, heat and moisture and another for the purpose of stabilizing against decomposition under the influence of light.
• various stabilizers are to some extent deficient in their ability to effect the desired degree of light-stability.
• materials such as benzaldehyde, thymol, isoeugenol, ethyl alcohol, butyl alcohol, turpentine, benzene, toluene resorcinol, aniline, quinol, hydroquinone mono-methyl and monoethyl others have been employed in conjunction with the general-purpose stabilizers.
• isoeugenol has been found to be unusually effective and it is especially effective when employed in combination with the new general-purpose stabilizers of this invention.
• a further object of this invention is to pro vide a new stabilizing composition of matter and a new solvent composition including the new stabilizing composition which will be especially stable under the influences of all of the several decomposing effects, and, particularly, the eif'ect of light.
• Unstabilized chlorinated solvents as obtained from the producer, including tetrachloroethylene, may be either in relatively pure or impure condition.
• the purity of such tetrachloroethylene depends upon its age, that is, the length of time it has stood unstabilized after production withoutparticular effort being made to prevent decomposition.
• pure solvent is found to be of limited utility for many industrial needs, although further decomposition may be satisfactorily inhibited by using the stabilizers of this invention.
• some solvent is relatively fresh and is correspondingly pure and useable; such solvent requires only stabilization against further decomposition in order to be satisfactory for a number of its uses.
• the solvent requires pre-treatment of a nature such that the major portion or substantially all of the impurities are removed, prior to the addition of stabilizers so as to provide a material having a good initial level of acceptability for industrial needs.
• some solvent may not require such pre-treatment; however, those skilled in the art will understand that preferably, a solvent containing undesirable impurities is treated for the removal of any impurities prior to stabilization. Such purification may be effected as hereinafter taught.
• the present. invention is described primarily in relation to solvent materials of relatively high initial purity; It should be understood, however, that the invention is not limited in applicability to substantially pure solvents but, rather, insofar as elfecting stabilization against fur- Accordingly, the relatively irnther decomposition is concerned, the present invention is effective substantially equally, in an impure or pure solvent.
• the present invention is directed to a composition
• a composition comprising essentially tetrachloroethylene and stabilizing amounts of ethers which are characterized by the presence of at least one acetylenic bond in their structure.
• the acetylenic ethers contemplated are those selected from the group consisting of hydrocarbon acetylenic ethers, halohydrocarbon acetylenic ethers and hydroxy hydrocarbon acetylenic ethers.
• the invention is directed to such a composition including an additional ingredient effective to exert stabilizing action against the influences of light. It will be understood that the invention is not limited to a particular light stabilizer and that any of the well-known light stabilizers may be employed. Preferably, however, the invention contemplates the use of isoeugenol in combination with the new general purpose stabilizers.
• the new class of general purpose stabilizers noted immediately above namely, acetylenic ethers, have been found particularly effective in stabilizing tetrachloroethylene contaminated with minor amounts of other lower aliphatic chlorohydrocarbons, both in the liquid and in the vapor phase.
• the stabilizing effect has been found to be most pronounced and prolonged where pre-treatments which destroy the greater part of the chloro-acids and acid chlorides have been resorted to prior to the addition of the stabilizing acetylenic ether.
• the initial treatment of the crude tetrachloroethylene may include adding an organic base of the amine type and having a boiling point higher than tetrachloroethylene, for example, aniline or morpholine, in an amount from approximately 0.22.0% by Weight to the crude product, and fractionally distilling the crude mass to recover substantially all of the tetrachloroethylene as an intermediate fraction in the distillation; additional treatments may include washing the tetrachloroethylene frac tion with a solution of an inorganic base, such as an alkali metal or alkaline earth metal base, for example, sodium hydroxide, sodium carbonate, calcium hydroxide, magnesium bicarbonate, and the like, drying the washed product and distilling the dried product to recover a more highly refined tetrachloroethylene fraction.
• an organic base of the amine type and having a boiling point higher than tetrachloroethylene for example, aniline or morpholine
• additional treatments may include washing the tetrachloroethylene frac
• the purpose in using an amine, such as aniline, is to allow for the reaction of such amine with acid chloride products contained in the crude product whereby an anilide or analogous compound may form during distillation and the undesired impurity is retained in the distillation residue.
• the purpose of washing the efiluent from the initial distillation with an alkali metal or alkaline earth metal base is to remove the more volatile of the acid chloride impurities, such as hydrogen chloride, phosgene, and the like, which may not have reacted with the amine.
• the crude product may also be washed initially with a solution of an inorganic base,'such as those noted above, dried, and combined with an amine having a boiling 4 point substantially higher than tetrachloroethylene, generally in an amount from 0.2T2.0% by weight, and the mixture thus obtained distilled as described above in order to recover the purified tetrachloroethylene substantially free from chloro oxygen-containing impurities.
• an inorganic base such as those noted above
• an amine having a boiling 4 point substantially higher than tetrachloroethylene generally in an amount from 0.2T2.0% by weight
• this material may be combined with an amine, such as aniline, as noted hereinabove, and subjected to fractional distillation to recover the substantially pure tetrachloroethylene without the necessity of resorting to the treatment with a solution of an inorganic base.
• the dilute alkaline wash may be omitted even where the chloro oxygen-containing compounds are present in appreciable quantities in the crude product, but it has been found that the amount of organic amine consumed and the volume of distillation residue accumulated is excessive.
• the recovered tetrachloroethylene may be combined with a stabilizing amount of an acetylenic ether, as noted above, for example, in an amount from 0.01- 1.0% by weight of tetrachloroethylene, preferably, however, from 0.20.3% where the above pro-treatments or their equivalent have been used.
• tetrachloroethylene has been purified in a commercial operation and stabilized either with a high boiling point stabilizer, i. e., a stabilizer such as one of the amine or of the ether type having a higher boiling point than that of tetrachloroethylene, or with stabilizers which are more volatile than tetrachloroethylene, by removing such stabilizer as by chemical reaction, azeotropic distillation, or the like; the thus-treated mass is then fractionally distilled to recover the tetrachloroethylene fraction, which may be combined with an acetylenic ether, as described above, in an amount sufficient to effect stabilization, whereby the tetrachloroethylene is rendered especially suitable, due to its stability, for, degreasing or dry cleaning operations.
• a high boiling point stabilizer i. e., a stabilizer such as one of the amine or of the ether type having a higher boiling point than that of tetrachloroethylene, or with stabilizer
• acetylenic ethers for use according to this invention either mono or dihydric alcohols containing a triple bond wherein the hydroxyl groups of the compound are secured to carbon atoms which are substituted by three other substituents may be employed.
• mono or dihydric alcohols containing a triple bond wherein the hydroxyl groups of the compound are secured to carbon atoms which are substituted by three other substituents may be employed.
• straight and branched chain compounds are suitable and, within the range expressed in the previous sentence, the relative'position of the triple bond and the hydroxyl groups is not pertinent.
• propargyl alcohol propargyl carbinol
• methyl acetylenyl carbinol methyl acetylenyl carbinol
• ethyl acetylenyl carbinol 2- butyne-l-ol
• higher homologues of this series including the octyl and nonyl substituted compounds, as well as aryl substituted compounds.
• dimethyl acetylenyl carbinol and higher homologues such as diethyl, dibutyl, diamyl and similiar substituted compounds, including those having two diiferent substituents, such as methyl, ethyl acetylenyl carbinol, and the like.
• dimethyl acetylenyl carbinol and higher homologues such as diethyl, dibutyl, diamyl and similiar substituted compounds, including those having two diiferent substituents, such as methyl, ethyl acetylenyl carbinol, and the like.
• methyl butynol and methyl pentynol and of particular interest of the isomers of these compounds are respectively 2-methyl-3- butyne-Z-ol and 3-methyl-1-pentyne-3-ol.
• .diol Any readily available .diol may be employed, especially attractive examples being 2,5-dimethyl-3-hexyne-2,5-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyne-3-ol.
• Suitable organic material that are to be taken as ether derivatives of the aforementioned alcohols are hydrocarbons, either acyclic, cyclic or substituted cyclic, saturated or unsaturated, including acetylenic unsaturation.
• Such materials may also be straight or branched chain; additionally, they may' contain functional groups such, for example, as halide and hydroxyl groups.
• such materials may contain as many as ten or more carbon atoms.
• more suitable materials are those of lower molecular weight, particularly those numbering about eight or less carbon atoms.
• the selection of this portion of the ether as to molecular weight, in a great many instances of contemplated use for the stabilized solvent, is made quite agreeably in relation to the boiling point of the resulting ether that is produced.
• the derivative portion might well be selected after having determined the alcohol to be selected.
• a low molecular weight hydrocarbon should be contemplated.
• the present invention permits the use of such substitute chemical and the realization of the improved result of the invention substantially without In the present instance, it is to be expected that such difficulty would most likely arise in obtaining the basic acetylenic material as exemplified by the alcohols above mentioned since the group of organic materials above noted are generally very readily available in any quantitydesired.
• ethers that are set forth above are the lower molecular weight ethers of the above-mentioned especially suitable acetylenic alcohols such as the methyl, ethyl, propyl butyl and isoamyl ethers of, for example, propargyl alcohol, and the methyl butynols and methyl pentynols, not only because of the remarkable stabilizing efiects that they have but also because of their conformity to'the desirable boiling range of the stabilizing materials.
• suitable acetylenic alcohols such as the methyl, ethyl, propyl butyl and isoamyl ethers of, for example, propargyl alcohol, and the methyl butynols and methyl pentynols
• ethers are outstanding in this property, such for example, being the propyl, butyl, isobutyl, isoamyl ethers of propargyl alcohol, methyl, ethyl, propyl and ethers of the methyl butynols and methyl pentynols.
• any of the ethers boiling between about and C. are regarded as especially suitable.
• N-BUTYL ETHER OF METHYL BUTYNOL To 2.0 g. sodium hydroxide dissolved in 4 ml. water is added 5.5 g. 3-methyl-3-chloro-l-butyne and 30 ml. n-butyl alcohol and the resulting mixture boiled for five minutes. The mixture is allowed to cool, sodium chloride beginning to precipitate at once. When sodium chloride stops forming, 50 ml. water is added and the organic (upper) layer separated, dried, and distilled, the
• One hundred mls. of the tetrachloroethylene to be tested for stability are placed in a 300-ml. flask equipped with a ground glass joint.
• a copper strip 2.0 x 7.5 x 0.005 cm. which has been washed with concentrated hydrochloric acid, water, dried and weighed, is placed in the flask.
• 0.2 ml. of water is added.
• the flask is attached to a small Soxhlet extractor equipped with a bottom ground glass joint and a top ground glass joint.
• a bulb type condenser with a bottom ground glass joint is attached to the Soxhlet.
• An acid washed, weighed copper strip (2.0 x 7.5 x 0.005 cm.) is placed being collected.
• the water scrubber (containing 150-200 mls. H O) absorbs any HCl that does not react with the copper during the stability run.
• two filter flasks so arranged that water is pushed from one flask to the other with changes in pressure, are employed.
• the flask containing the tetrachloroethylene is heated on a heater controlled to adjust the boiling rate so that the Soxhlet extractor empties every 8-10 minutes.
• a 100-watt bulb is placed one inch from the vapor line of the-Soxhlet extractor to furnish light for the photochemical oxidation.
• the stability test is run for 72 hours.
• the aggregate loss in weight of the copper strips is a measure of the stability of the tetrachloroethylene tested.
• Example I For this example, two 100 ml. samples of unstabilized tetrachloroethylene of about four weeks age are employed. This material, due to its age, contains a substantial quantity of impurity; nevertheless, the effectiveness of the stabilizer is clearly demonstrated.
• Example 11 A similar sample tested identically and concurrently with the above but containing 0.01% by weight isoeugenol in addition to the ether loses about 9.8 mg.
• Example III Employing the same tetrachloroethylene stock as employed in Example I, a sample is prepared using phenyl propargyl ether as the stabilizer and tested concurrently with the Example I samples. The total weight loss is about 10.8 mg.
• Example IV A sample similar in all respects to that of Example 111, except that isoeugenol is present as a light stabilizer in addition to the ether, is prepared and tested concurrently with the Example I samples.
• the total weight loss is about 8.6 mg.
• a composition of matter comprising a lower molecular weight chlorinated hydrocarbon and a stabilizing amount of an acetylenic ether selected from the group consisting of hydrocarbon acetylenic ethers, halohydrocarbon acetylenic ethers and hydroxy hydrocarbon acetylenic ethers.
• a composition of matter comprising a lower molecular weight chlorinated hydrocarbon and a stabilizing amount of an acetylenic ether selected from the group consisting of hydrocarbon acetylenic ethers, halohydrocarbon acetylenic ethers and hydroxy hydrocarbon acetylenic ethers, the boiling point of which is within about 20 C. of the boiling point of the said chlorinated hydrocarbon.
• composition of matter as claimed in claim 1 which includes a light stabilizer.
• composition of matter as claimed in claim 1 which includes isoeugenol as a light stabilizer.
• composition of matter as claimed in claim 2 which includes isoeugenol as a light stabilizer.
• a composition of 'matter comprising tetrachloroethylene and a stabilizing amount of an acetylenic ether selected from the group consisting of hydrocarbon acetylenic ethers, halohydrocarbon acetylenic ethers and hydroxy hydrocarbon acetylenic ethers.
• a composition of matter comprising tetrachloroethylene and a stabilizing amount of an acetylenic ether selected from the group consisting of hydrocarbon acetylenic ethers, halohydrocarbon acetylenic ethers and hydroxy hydrocarbon acetylenic ethers, the boiling point of which ether falls within the range of about to about C.
• composition of matter asclaimed in claim 6 which includes a light stabilizer.
• composition of matter as claimed in claim 6 which includes an effective amount of isoeugenol as a light stabilizer.
• composition of matter as claimed in claim 7 which includes an effective amount of isoeugenol as a light stabilizer.

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