DE2102842A1 - Stabilized methyl chloroform - Google Patents

Description

Priority: January 22, 1970, 7th St.A., No. 5101

It is well known that various lower chlorinated aliphatic hydrocarbons can be used, especially for liquid and / or vapor phase metal degreasing. Because of their excellent cleaning properties, these chlorinated solvents are very suitable for technical purposes because they are non-flammable and relatively cheap. The most widely used of these solvents are carbon tetrachloride, srichlorethylene, perchlorethylene and methylchloroform (1,1,1-trichloroethane). There is particular interest in methyl chloroform, whose excellent dissolving power and low toxicity make it highly suitable for the technical cleaning (degreasing) of catals «

The penetration of methyl chloroform in the technical field, however, was genwart because of its strong i.cigung to decompose in a Ge many metals, especially aluminum, Disabled. Although other chlorinated solvents, such as perchlorethylene,

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compared to the decomposition caused by the most diverse factors nuts are also stabilized, this is

almost no settlement problem with any connection / as severe as in Case of methyl chloroform. If you do! ”! Stabilized methyl chloroform If aluminum is exposed, it will become unusable within a few minutes.

While other chlorinated solvents can thus be stabilized by means of low proportions of the most varied of compounds, tests have confirmed that there are only a limited number of compounds, We ¹ C ^-1 ".3 act as stabilizers against the decomposition of methylchloride caused by metals, and that Because of the high requirements and the limited selection, the search for improved stabilizer systems which counteracted methylchloroform and the metals treated therewith both in the liquid and in the vapor phase in the presence of a wide variety of impurities came about On the one hand, the stabilizers must be cheap, since relatively large amounts are required. On the other hand, the methyl chloroform can alternatively be provided for both liquid and vapor phase degreasing Unless other problems often arise than with vapor phase stabilization and thus different types of stabilizers would be suitable, the components must be compatible with one another within a wide temperature range.

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In many "known and commercially available stabilizer systems nitroalkanes and epoxides are used. Such stabilizer systems are only conditional for Methylchloro'forra applicable. Although many of these systems use a nitroalkane / epoxy

loading

Have "basis", the aforementioned combination acts as such not always a fully effective stabilization of methyl chlorine ο form, and it depends on the choice of the remaining components of the respective system to determine whether such an effect will ultimately be achieved is achieved.

^ ufgäbe the invention wax it, an improved, cheap multicomponent stabilizer system based on a liitro-

alkane / epoxy combination decomposition-stabilized, in particular / To provide solvents suitable for liquid and steam-phase metal degreasing. % ese task is achieved by the invention.

The invention thus relates to a methyl chloroform, which a stabilizer system based on a nitroalkane / epoxy combination contains and which is characterized in that it is used as additional stabilizer components

1.3-

A) Propylene glycol monomethyl ether and / or trioxane and / or / biox-

epan as well as, if applicable

B) methylbutynol and / or tert-amyl alcohol, if appropriate

C) a hydrocarbon and optionally at least

D) / a basic compound or its precursor,

contains.
1,3-Dioxepane is a cyclic ether of the formula OCHUa (CHp), CH ₂ .

The stabilized methyl chloroform according to the invention is suitable especially good for metal degreasing. The effectiveness of the

21028A2

thylchloroforms is caused by the presence of the aforementioned alcohols (B) is increased considerably and can be increased even further when these alcohols are used by adding a hydrocarbon (C) will. Even if the basic compound or its precursor (D) is added, a certain degreasing method can be used optimally suitable methyl chloroform can be obtained. The stabilized methyl chloroform according to the invention can by suitable Choice of stabilizer components can be adapted to the most diverse requirements in the field of metal degreasing and

Everyone ' .

can also be used for / other purposes where a stabilized Material is needed.

"Nitroalkanes" here are those conventionally used for stabilization nitroaliphatic compounds used by chlorinated solvents to understand, preferably corresponding C ^, compounds, such as nitromethane, nitroethane, 1-MItropropane or 2-electropropane.

Also under '"Epoxides" are the. conventionally in chlorinated To understand solvents used epoxides, preferably optionally substituted aliphatic C? o-epoxies. It is It is important that the boiling point of the epoxide in question does not differ significantly from that of the methyl chloroform. Specific examples of epoxides preferred according to the invention are propylene oxide, butene oxide, epichlorohydrin and methyl glycidyl ether.

• (C)
The term "hydrocarbon" / refers here to the

various hydrocarbons, such as saturated or unsaturated aliphatic or cycloaliphatic or aromatic 'carbon

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Hydrogens. Specific examples of hydrocarbons suitable according to the invention are hexane, heptane, octane, hexene, trimethylpentene, cyclopentane, cyclohexane, cyclohexene, cyclooctene and iDoluene. Depends primarily ron their boiling points and their cost or other hydrocarbons can be used erfindungsgeraäss, of course, when performed in the cold degreasing a large number is suitable these compounds.

Examples of basic compounds (») suitable according to the invention are the amines for precursors of these basic compounds Oximes and Hydrazones. The basic compounds suitable according to the invention are soluble in methyl chloroform and have a general boiling points which are similar to those of Methylchiorοform im essentially correspond. However, some of these basic compounds apparently form with the methyl chloroform and / or other components of the stabilizer system azeotropically boiling mixtures and thus change their actual measured boiling points, Specific examples of basic ones preferred according to the invention Compounds are: I-methylmorpholine, diisopropylamine, and pyrrolidine.

Although it is difficult to assign certain sanctions to the individual components of the stabilizer system used according to the invention, the propylene glycol monomethyl ether and / or 4as orioxane and / or dioxepane (A) act as a reinforcing agent / xiitroalkane / epoxy base combination. While each of the three aforementioned additives (A) appear to have approximately the same effectiveness , for practical reasons they often have different ones

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1.3-binary combinations, such as 2rioxane / X) icxei3an, are the best.

This is particularly the case when this is according to the invention stabilized methylchloroform should contain high levels of stabilizer.

While methylchloroform, which acts as a stabilizer system, a liitroalkane-epoxy combination and additionally ^ ropylene glycol monoriethyl ether and / or! contains trioxane and / or dioxepane, is effective for most purposes, the incorporable stable! - by the boiling point of the additional component

(A) limited to a certain degree. However, it was found that the effectiveness of the stabilizer system, especially its resistance to aluminum when diluted at room temperature, is improved by the further addition of methylbutynol and / or tert-amyl alcohol (B). These The effect of the alcohol component is important because a marketable product must be highly dilutable without noticeably to lose its impact. By the aforementioned component

(B) This requirement is thus met without the problem of which generally when most alcohols are used to stabilize methyl chloroform solutions when they are used Vapor phase defection occurs. The aforementioned problem arises in particular that various alcohols are effective when degreasing is carried out at room temperature, however at the reflux temperatures often damage steel or aluminum surfaces with which they are in contact. the Alcohols (B) used according to the invention - on the other hand, have excellent effectiveness.

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regulating

The / effect of the aforementioned alcohols (B) in the case of dilution is further enhanced and the distillation range of the stabilized solvent is further improved if a hydrocarbon (C), such as heptane, is also added. Of course, when such relatively inexpensive hydrocarbons are used, a reduction in the proportion of the other expensive components can result in a cost saving.

If a problem of steel corrosion in the presence of methylchloroform in the vapor phase occurs, it may be useful to add one of the basic compounds known for their suitability for this purpose as component (D) to the methylchloro-corin. The stabilized methylchloroform according to the invention can contain one or more of these basic compounds as required, regardless of whether an alcohol (B) and / or a hydrocarbon (C) is present or not.

The proportion of the stabilizer system added to the methyl chloroform is generally dimensioned in such a way that, taking into account the economic efficiency, a stabilization of the most diverse Conditions is achieved. It depends on the particular application from how high this proportion is. In general, according to the invention but 90 to S9 percent by weight of methyl chloroform and 10 to 1 percent by weight of the stabilizer system is present. The amount of the stabilizer system is preferably 4 to 6 percent by weight,

the single
Of / stabilizer components can be 0.1 to. 2 percent by weight of the

Nitroalkanes, 0.05 to 0.5 percent by weight of the epoxide, 0.1 to ■

Weight percent

3 / propylene glycol monomethyl ether and / or trioxane and / or

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1,3- / dioxepane, 0.1 to 2 percent by weight Ilethylbuti> iol and / or tertiary amyl alcohol, 0.1 to 2 percent by weight of the hydrocarbon and 0.001 to 0.1 percent by weight of the basic compound or its intermediate, each based on the stabilized Methylchloroi'orm, to be available.

The examples illustrate the invention.

The tests which are used to determine the effectiveness of the various stabilizer systems will now be explained in advance can be used.

The "aluminum scratch test ^11" consists in dipping an aluminum sheet metal strip into the methyl chloroform solution to be examined and scratching the dipped surface with a pencil with a fine tip so that a fresh surface is exposed to the solvent. This is exclusively qualitative

represent

Test is only a classification procedure /. If that stabilized Me thy! Chlorοform therefore cannot pass this test Of course, it also fails to withstand the more stringent tests described below. The aluminum scratch test will fail indicated by "bleeding", i.e. constant discoloration of the solvent, at the scratched area.

Another and more stringent test that is applied to stabilized methyl chloroform is the aforementioned scratch test has already passed the "72-hour aluminum reflux test" In this test, 100 ml of the solvent system and 0.2 ml of water are placed in one equipped with a condenser Flat-bottomed flask filled. Then there are 2 Alurainium sheet metal strips

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one of these strips is inserted into the flask while the other is suspended in the cooler, where the solvent vapor envelops the metal strip, condenses on it and drips off it during the long-term test carried out under mild reflux conditions. The aluminum reflux test also has a predominantly qualitative nature, and bad results are easily recognized by the corrosion on the aluminum and the discoloration of the solvent. Another purpose of the aluainium recirculation test is to determine the acid content of the stabilized solvent by measuring the final pH value. Y / Unless otherwise stated, all systems have a Pjj value γόη at least 7 at the beginning. At the end of the aforementioned 72 hours in the aluminum reflux test, the solvent is cooled and extracted using a ratio of 1: 1 with neutrally reacting water. The p "value of the aqueous phase is then determined. A low p _JT value of course indicates the presence of acid released by the decomposition of the solvent and thus the inadequate effectiveness of the stabilized system in preventing aluminum corrosion and solvent decomposition.

A similar test is the "steel resistance test", which is carried out in a whiteness that is very similar to that of the aforementioned aluminum / backlush test. In the steel resistance test, instead of the aluminum sheet metal strips in the piston and cooler, steel sheet metal strips are used, and a Soxhlet extraction device arranged between the piston and the cooler also contains a steel sheet metal strip. -The steel resistance test is generally quantitative, since the steel- • r

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Sheet metal strips are weighed before and after. Au. uo;, i weight loss will be the relative effectiveness of the vorechi. uorion systems certainly.

example

Table I shows a comparison of the effectiveness of various multicomponent stabilizer systems or that of a simple 'ITit roethane / epoxide system or of propylene glycol ionomethyl ether alone for stabilizing methylchloroform.

Table I.

Rehearse-
Ur. Stabilizer sys
tem Anti-
Ie,
Weight-5 » Gefcamt-
stabili-i
sator-:
men /; e, \
GevT. -ίί Aluni-
niuci-
• i: ratz-
tect,
**) 72-hour aluminum
um-xUickf lun ste ε t Cool
ler % ~
value 1 Kitroäthaii /
Butene oxide 3.6
0.4 I.
4.0 3 Pistons! 2 PGMÄ *) 2.8 2.8 2 _ - - 3 Nitroethane
Butene oxide
PGI-IÄ 0.8
0.4
2.8 4.0 1 - C. 6.0 4th Nitroethane
Butene oxide
PGI-IÄ
Trioxane 0.8 ■
0.4
2.0
0.8 4.0 1 A. C. 6.0 5 ITitroethane
Butenoxia
PGMÄ
Trioxane
Methylbutynol 0.8
0.4
2.0
0.8
1.0 5.0 1 A. A. 6.7 6th :; itroethane
Butene oxide
PGMÄ
Trioxane
tertiary amyl alcohol 0.8
0.4
1.0
0.6
1.5 4.'3 1 A. B. 7.0 A.

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*) PGIlA "- propylene glycol monolifethylethyl

**) 1 = no J'.uv. \\ 'irkv.iif-j

2 = preliminary "i *;> lic ^j } iOe hole formation

3 = standifjes "bleeding"

***) A = no corrosion

B = slight corrosion

C = severe corrosion

From the values shown in Table I it can be seen that the combination of nitroethane and butene oxide (Prr.be 1) does not pass the Alusiniun Kratr.test and is therefore unsuitable as a stabilizer system for methyl chloroform. The propylene glycol monomethyl ether (sample 2) in the aforementioned test vei'sagt It loading Λ Jteht therefore no reason to Annahne that a Korabination of -... ■ robe 1 and sample 2 is effective bsw However, as the sample 3 show ί, in using a combination of Ijitroethane, butene oxide and propylene glycol monomethyl ether as well as optionally trioxane a stabilized methyl chloroform are obtained, which, as can be seen from the improved result of the ALuninium scratch test, is completely suitable for cold degreasing processes. Samples 5 and 6 show that the stabilized methyl chloroform of Example 4 is so much improved by a further addition of ^ Hethylbuünol or tert.-amyl alcohol that the TZ- ^ hour aluminum reflux test at B conditions that simulate vapor phase degreasing, excellent results can be achieved.

Example 2

Table II shows certain outstandingly suitable ones according to the invention Listed stabilizer systems, which are a basic compound containfiii. I.s the effectiveness of these systems to

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Reduction of the corrosiveness of methyl chloroform towards steel shown. The results contained in Table II come from a comparative experiment in which only one nitroethane and methylehloroform containing butene oxide was investigated, (Results not shown) and show the reduction in the weight loss of steel sheet metal strips, which with the invention stabilized methyl chloroform.

^; Table II

Rehearse- Stabilizer system Shares, Total st $> Improvement Mr. Gewients- bilizer opposite to percent lot, Nitroethane / Wt .- ^ Butene oxide **) ¹ 7 Nitroethane 0.8 - Butene oxide 0.4 PGKA *) 1.0 Tri oxane 1.0 3.2 no 8th Nitroethane 0.8 Butene oxide 0.4 PGM 2.0 N-methylmor ph ο1in 0.025 3.2 20th 9 Nitroethane 0.8 Butene oxide 0.4 PGHiL 2.0 Methylbutynol 1.0 N-methylmorpholine 0.025 4.2 50

* Propylene glycol monomethyl ether
** Reduction of the weight loss in the steel resistance test From the results shown in Table II it can be seen that propylene glycol monomethyl ether alone has no measurable effect on the stability of methyl chloroform in the presence of steel, but that by adding a low proportion of a basic compound (N-methylmorpholine ) an improvement is achieved which is considerably higher when methylbutynol is also present.

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Example 3

A methyl chloroform solution, which is stabilized with 0.4 percent by weight of butene oxide, 1.8 percent by weight of propylene glycol ronoraethyl ether, 1 percent by weight of trioxane and 0.4 percent by weight of hitromethane shows "excellent results in the aluminum scratch test. After the 72-hour aluminum backflow test, a Achieved final pTT- * value of 6.9, and the one hung in the condenser
Sheet metal strip shows only minor corrosion spots, while the solvent remains colorless and clear,

Example 4

A methyl chloroform solution containing 0.2 percent by weight of epichlorohydrin, 0.2 percent by weight of methyl glycidyl ether, 1.8 percent by weight weight percent propylene glycol mono diethyl ether, 1 weight percent Dioxepane, 0.8 percent by weight of nitroethane and 0.005 percent by weight Diisopropylamine is stabilized, shows excellent in the aluminum scratch test and in the 72 hour aluminum backflow test Results, a final p ^ value of 7.9 is obtained, and the metal strip hung in the cooler remains undamaged, while the solvent remains colorless and clear,

Example 5

A methyl chloroforra solution containing 0.4 percent by weight of butenaxide, 1 percent by weight of propylene glycol monomethyl ether, 0.5 percent by weight of trioxane, 1.5 percent by weight of tert-amyl alcohol, 0.8 percent by weight of nitroethane, 1.5 percent by weight of heptane and 0.02 percent by weight of H- Kefchylraorpholine stab! Lined; shows in the Aluninium-Krati ^ eSt ₁ outstanding BJr ^ obui .. se.

10 c '? 1 ^{r BAÖ} OWQJNAL

After the 72 hour aluminum reflux test, the metal strip hung in the cooler shows only slight corrosion spots. The ρττ value after the test is 7.6, while the Lo i> uri £ s average remains colorless and clear.

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Claims (6)

) Claims Sr- ^ Methylchloroform, containing a Stabilisatorsyatem on the Based on a nitroalkane / epoxy combination, thereby g e - further indicates that it is used as a / Stabilisatorkciriponenten A) Propylene glycol monomethyl ether and / or trioxane and / or 1 »> -dioxepane as well as, if applicable B) methylbutinol and / or tert-amyl alcohol, if applicable C) a carbon and, if applicable at least D) / a basic compound or its precursor contains. 2. ■ methyl chloroform according to claim 1, characterized in that that the basic (s) compounds) (I)) N-Iiethylmorpholine and / or Is (are) diisopropylamine and / or pyrrolidine. 3. Methylehloroform according to claim 1 or 2, characterized in that that it contains a C-j ^ -nitroalkane as the nitroalkane. 4. Methylehloroform according to claim 1 to 3, characterized in that that it contains an optionally substituted aliphatic C-z g-epoxide as epoxide. 5. Methylehloroform according to claim 1 to 4, characterized in that that it contains 1 to 10 percent by weight, preferably 4 to 6 percent by weight, of the total stabilizer system. 6. Methylehloroform according to claim 1 to 5 »characterized in that that there is 0.1 to 2 percent by weight of the Kitroalkam, 0.05 bio 0.5 percent by weight of the Epoxius and 0.1 to "3 percent by weight of component A).,. contains. 10983 1/9235 BÄÖ ORIGINAL 7 methyl chloroform according to claim 1 to 6, characterized in that that-there is an additional 0.1 to 2 percent by weight of the component B), 0.1 to 2 percent by weight of component C) and 0.001 to 0.1 percent by weight of component D). BATH ORIGINAL 109831/2235