CA1043817A

CA1043817A - Stabilized methylchloroform

Info

Publication number: CA1043817A
Application number: CA176,891A
Authority: CA
Inventors: Wesley L. Archer; Elbert L. Simpson; Raymond T. Gerard
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1972-08-16
Filing date: 1973-07-19
Publication date: 1978-12-05
Also published as: AU5838073A; JPS5640691B2; BR7306269D0; FR2196309A1; DE2340662A1; BE803675A; GB1439970A; JPS4992004A; FR2196309B1; NL7310711A

Abstract

ABSTRACT
A stable 1,1,1-trichloroethane composition con-taining, based on total composition weight, a) about 0.2 to about 1.2 weight percent of a C3-8 monoepoxide, C3-8 monochloroepoxide or mixture of such epoxides; and b) about 3.8 to about 4.8 weight percent of a mixture of one component from each group: 1) nitromethane; 2) 1,1-dimethoxyethane or t-butyl alcohol, and 3) dioxene, trioxane, or dioxolane, in the proportions set forth in drawings with the provision that the 1,1-dimethoxyethane-nitromethane-dioxolane system is employed in a concentration of 4.3 to 4.8 weight percent.
The above compositions are stable in the presence of the metals aluminum, zinc, iron and their alloys, both in the liquid and vapor state of the compositions. The compositions do not partition in a manner to concentrate the low boiling stabilizers in the vapor or the high boiling stabilizers in the liquid even after refluxing over extended periods of time accompanied by frequent additions of make-up volumes of stabilized 1,1,1-trichloroethane.

Description

~3t~ 7 This invention concerns a stabilized 1J 1 trichloroethane (methyl chloroform) composition.
l,l,l-Trichloroethane has become a promising solvent for the metal working and textile industries because of its low toxicity and good ecological properties and is being widely used by industry to replace both trichloroethylene and perchloroethylene. However, 1,1,1-trichloroethane is known to exhibit a high degree of in-stability in the presence of aluminum, iron, or alloys thereof, and when inhibitors are present to increase sta-bility, then often zinc becomes a problem. Various com-pounds and mixtures of compounds for stabilizing the 901-~ent, particularly in the pre~ence of aluminum, have been proposed. While a few of the prior stabilizer~ are used commercially, none exhibit the degree of stabilizing effect which is necessary if the solvent is to be used in an un-restricted manner by industry, especially in vapor de-greasing. The criteria for establishing a commercial -~
grade of l,l,l-trichloroethane which has unrestricted utility in industry should include an equal degree of stability of the liquid and its vaporsJ less than about ten percent total inhibitors, and a substantial ability to be distilled without loss of stability by concentration of the low boiler~ in the overhead and high boilers in the bottoms of the still, and the like. Even today these criteria are not all found in the commercial compositions.
This invention provides compositions which are effective at concentrations of from between about four to about six percent and which meet the criteria set out above.
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~3~17 Accordingl~, the present invention provides a l,l,l-trichloro-ethane composition comprising as essential stabilizers against metal induced degradation: a) 0.2 to 1.2 weight percent of a C3 8 monoepoxide, mono-chloro monoepoxide or mixture of epoxides, and b) 3.8 to 4.8 weight percent of a mixture of one component from each group: 1) l,l-dimethoxy-ethane or t-butyl alcohol, 2) dioxene, dioxolane or trioxane, and 3) nitro-methane in the proportions within the shaded areas of Figures 1-5, the stabili~ers being added in amounts to keep the composition stabilized against undesirable degradation and partitioning in both the liquid and the vapour form, with the provision that the l,l-dimethoxyethane-nitromethane-dioxolane system is employed in a concentration of 4.3 to 4.8 weight percent.
Figures 1-5 represent graphic illustrations of compositions of the named three-component systems which, when employed in accordance with the present invention, provide the protection of the solvent, both liquid and vapor, and metal in contact with the solvent, both liquid and vapor.
The vertical line shaded area in each figure represents the compositions of the named ingredients which are effective at 3.8 weight percent of a mixture of the three ingredients in the proportions derivable from the graph. The 45 left_angled lined shaded area and the vertical lined area together represent the compositions of the named ingredients which are effective at 4.3 percent of a mixture of the three ingredients in the proportions derivable from the graph which fall within the scope of the present invention. The 45 right-angled lined shaded area plus the left-angled lined shaded area - plus the vertical lined shaded area represent the compositions of the named ingredients which are effective at about 4.8 weight percent of a mixture of the three ingredients in the proportions derivable from the graph. The compositions within the shaded areas and which contain the additional stabilizer noted above, an epoxide, are stable in their liquid form as well as their vaporous form, can be distilled with the distillate being stable to attack on and by metals, can be repeatedly vaporized and condensed, as in vapor de-greasing, without loss of stability, and can be partially lost, as in vapor degreasing, with frequent make-up added without build-up of high boilers in the liquid.
The useful epoxides include propylene oxide, butyl-ene oxide, isobutylene oxide, the pentylene oxides, the hexylene oxides, heptylene oxides, the octylene oxides and their monochloro derivatives, such as epichlorohydrin. The ;
preferred epoxides are propylene oxide, epichlorohydrin, butylene oxide, isobutylene oxide and mixtures of these oxides.
It has now been found that with the exception noted at page 2 line lO above, l,l,l-trichloroethane containing from 3.8 to about 4.8 percent by weight of one of the compo-sitions within the shaded areas as shown in Figures 1-5 of the drawings in combination with about 0.2 to about 1.2 ? percent by weight of a C3 8 monoepoxide or chloromonoepoxide will be stable against deterioration in the presence of - - :
- metals, particularly aluminum, zinc, iron, or alloys thereof in the liquid state and/or vapor state under the use con-:. . .
ditions encountered in industry. Thus, compositions of , l,l,l-trichloroethane containing one of the compositions ;
illustrated in the figures of the drawings and epoxide will remain substantially colorless, without deterioration or attack upon aluminum, whether in the liquid or vapor state, . 30 longer than known stabilized ~-: ~' ''' '.,`: ' ' '' ., ''`''' ',' ~.
16,059-F -3- ~-~)43~
compositions. Tests indicate that inhibitors which are illustrated in the figures of the drawings will satisfactorily stabilize l,l,l-trichloroethane in the vapor and liquid state without, through partitioning, lo~s of inhibitors or build-up of inhibitors to a degree to affect stability and/or safety, will permit di~tillation without los~ of inhibitors to below the safe level and will tolerate the presence of the common acidic contaminants, grease, oil, and metal fines without losing their inhibit-ing qualities.

ExamPles A series of tests was conducted to determine the partitioning properties of the ~everal compounds here employed. The apparatus consisted of a one liter, round bottom flask. To this flask was attached a one liter, round bottom flask which had been altered by placing a glas~ pipe through the bottom extending to a point in the interior such that the flask would hold 450 ml. of liquid to the upper lip of the pipe. The exterior portion of the pipe extending from the bottom was fitted into the neck of the first flask. A water condenser was fitted to the neck of the dified flask in a manner such that ; condensate dripping from its interior wall will fall into the body of liquid retained in the upper flask.
oPeration-Nine hundred milliliters of the solvent composi-tion (l,l,l-trichloroethane plus the enumerated inhibitor) under study was placed into the bottom flask. The entire apparatus was covered with aluminum foil to exclude light and to retain some warmth in the overhead flask, su~h as ~
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~3~L7 occurs in the warm dip of a degreaser. Heat was applied to the lower fla~k and a moderate reflux rate maintained for 24 hours.
At the end of this period, the apparatus was allowed to ~ool and the two solvent portions analyzed for stabilizer concentrations and aliquots ~ubjected to a "Blender Test" as hereinafter defined.
In this manner, there i~ obtained the data to calculate a factor representing the proportion of the inhibitor which will go overhead with the vapors and that proportion which will remain behind in the sump liquid in a conventional vapor degreaser. The factors determined by this experiment are referred to a~ partitioning factors for the top and bottom. The partitioning factor~ were determined by analyzing the top fraction and the bottom fraction of the partitioning experiment for each inhibitor, determining the percent inhibitor in each of the top and bottom fractions and normRlizing these values to a decimal value on the basis of that fraction of solvent to a unit (100% basis). Thus, for dioxolane, it was determined that ca. 55 weight percent of the inhibitor in the original ~ composition was found in the top fraction of the partition-; ing experiment t50% by volume of the original amount) and ca. 45 weight percent wa~ found in the bottom fraction.
Normalizing the~e value~:

Top Partitioning Factor = 0.55 = 1.1 ; 5 ....
Bottom Partitioning Factor = 0.45 = 0.9 ~' .. . . .
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The partitioning factors for each inhibitor were run - several times, and the average of the values obtained from these several runs was calculated. The values for each inhibitor under consideration are set forth below:

Partition Factor Partition Factor as Percent in:
Top Bottom Top Bottom Dioxolane 1.06 0.9 55 45 DMEl 1.16 0.88 55.8 44.2 ~Ml 1.28 0.72 64.7 35.3 BOl 1.2 0.8 60 40 1. DME = l,l-Dimethoxyethane; NM = ~itromethane; and BO = Butylene Oxide : :
The "Blender Test" comprises placing 100 ml. of the composition being tested, at room temperature, in a blender with 10 grams of aluminum chip~ and running ;
the blender for 10 minutes, then filtering the sample and determining the APHA color of the filtrate.
The results of such testing e~tablished the minimum concentration of each inhibitor which was required to be present in an original composition to enable the condensate of the vapors as well as the sump to be essentially nonreactive to aluminum. Table 1 gives the results obtained employing only the named inhibitor and l,l,l-trichloroethane.
The concentration for APHA color of ~1000 is chosen as the criterion for substantially no reaction after the "Blender Test." The analysis for inhibition in the top fraction and bottom fraction i8 set forth in percent of inhibitor found. The minimum concentration for protection in top and bottom is found by dividing 16,059-F -6-~U'~3~
the value determined as the concentration for APHA
color <1000 by the smallest partitioning factor for ` -the inhibitor.
Thus, for dioxolane:
Minimum concentration for dioxolane = <1000 APHA conc.
Partition Fraction 4.0 = 4,4.

The final concentration in each of the top and bottom of a system empIoying the minimum concentration is found in the la~t column.

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:~V~3~-7 To demonstrate the effectiveness of the compositions of the present invention against build-up of high boiling components in the sump as well as to demonstrate that the loss of low boiling components is not such as to impair stability in the sump or create toxic or hazardous vapor mixtures, a series of calculation~
are set forth in Table 2 based upon partitioning data -- actually obtained as shown above for each component.
The calculations are based on observations and experiences in operating commercial degreasers. Thus, in commercial operations, a degreaser of about 4 gallons (15 liters) capacity having an electric heating coil in the bottom -and cold water condensing coils about the upper interior . . . .
walls is operated in a manner such that over a period of . :; ., .
lS about one week about 1/2 of the initial charge of solvent is lost. The original solvent charge was l,l,l-trichloro-.:
ethane plus 2.8 wt. % dioxolane, 0.8 wt. % l,l-dimethoxy-` ethane, 0.5 wt. % nitromethane, and 0.5 wt. % butylene : . :
oxide. Replacement of the solvent lost on a once-a-week i;
basis with fresh stabilized composition over a 2 nth period would result in the compositions set forth in Table 2, in the sump (Col. 4), the vapor from the sump at the end of each week (Col. 5) and the ma~e-up to original volume at the end o each week (Col. 6).
All calculations are normalized to 100 percentage basis; thus, when 50/O of the original solvent composition is lost or vaporized, the Qump contains a weight of `~ inhibitor in one-half of the original volume. Therefore, the new percentage of inhibitor is obtained by dividing the actual weight percent in the fraction under consideration ` . :"
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3~7 ~y a fraction which reflect3 the solvent weight under consideration, e.g., 100 grams of ~olvent containing 2.8 weight percent dioxolane would have, when 50 weight percent is lost, 2.8 x 0.45 = 2.53 weight percent dioxolane o,5 (100% basis) 2.8 i9 the percent dioxolane.
0.45 is the percent dioxolane remaining in the sump as determined by partitioning data.
0.5 is the weight percent solvent remaining.
Similarly, the inhibitor in the solvent lost (e.g., as vapor) is calculated as follows:

2.8 x 0.55 = 3.08 weight percent dioxolane 0 5 (lOOYo basis) In the table, in order to have linear calculation~, the following formula is u~ed:
% wt. inhibitor x % partitioning x 2 = % wt. inhibitor (100% basis) The calculation~ to obtain the data ~et forth in Table 2 are:
Col. 3 - Original weight percent (Col. 1) times percent inhibitor to the top (obtained in partitioning experiment~) to obtain actual weight of each inhibitor lost in the vapor lost to the atmosphere. The figure in parenthesis is the percent by weight of inhibitor in the lost qolvent on a 100% wt. ba~
Col. 4 - Original weight percent (Col. 1) times percent inhibitor in the bottomq partitioning to obtain actual weight of each inhibitor remaining in sump as solvent i9 lost. The figure in parenthesis is the percent by weight of inhibitor in the qump on a 100% wt. basis.

16,059-F -10-~.. . . ,.~.. . ., . ., . . . . . ., . ~ .. -Col. 5 - Weight o~ itor in vapor from ~ump after loss of 50% of original solvent volume, Col. 4 times - percent inhibitor to the top. The figure in parenthesis is the weight percent of inhibitor in the tops on a 100% basis.
Col. 6 - Total inhibitor in sump after addition of enough fresh solvent to make-up sump to original volume with material containing original weight percent of each inhibitor. Col. 4 actual weight percent plu~ actual weight percent in make-up volume (e.g., for dioxane, 1.4); thus, 2.14 (from Col. 4) plus 1.4 = 3.54 of Col. 6.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A 1,1,1-Trichloroethane composition comprising as essential stabilizers against metal induced degradation: a) 0.2 to 1.2 weight percent of a C3-8 monoepoxide, monochloro monoepoxide or mixture of epoxides, and b) 3.8 to 4.8 weight percent of a mixture of one component from each group: 1) 1,1-dimethoxyethane or t-butyl alcohol, 2) dioxene, dioxolane or trioxane, and 3) nitromethane in the proportions within the shaded areas of Figures 1-5, the stabilizers being added in amounts to keep the composition stabilized against undesirable degradation and partitioning in both the liquid and the vapour form, with the provision that the 1,1-dimethoxyethane-nitromethane-dioxolane system is employed in a concentration of 4.3 to 4.8 weight percent.

2. A composition according to claim 1 wherein the nitromethane is present in a concentration of at least 0.25 weight percent.

3. A composition according to claim 1 wherein the components in (b) are nitromethane, dioxene and 1,1-dimethoxyethane in the proportions within the shaded areas of Figure 1.

4. A composition according to claim 1 wherein the components in (b) are dioxolane, nitromethane and 1,1-dimethoxyethane and are present in a total concentration of 4.3 to 4.8 percent in the proportions within the shaded areas of Figure 2.

5. A composition according to claim 1 wherein the components in (b) are trioxane, nitromethane and 1,1-dimethoxyethane in the proportions within the shaded areas of Figure 3.

6. A composition according to claim 1 wherein (a) is butylene oxide and the components in (b) are dioxene, tertiary butyl alcohol and nitro-methane in the proportions within the shaded areas of Figure 4.

7. A composition according to claim 1 wherein (a) is butylene oxide and the components in (b) are trioxane, tertiary butyl alcohol and nitro-methane in the proportions within the shaded areas of Figure 5.