DE2164259B2 - - Google Patents

Description

1,1,1-trichloroethane is widely used as a commercial solvent for cleaning metals It is not used as a solvent for oils such as cutting oil, machine oil or lubricants only has a good dissolving power, but is also non-flammable and has a lower toxicity, than the rest of the chlorinated hydrocarbons, and since it is neither light nor oxygen rapid is decomposed. However, when 1,1,1-trichloroethane comes into contact with metals and especially with Aluminum, it reacts with these very quickly and forms hydrochloric acid and a brownish tan-colored material decomposed2: t. It is therefore common to use 1,1,1-trichloroethane different Add stabilizers to prevent this decomposition.

Numerous organic compounds are either individually or combined as 1,1,1-trichloroethane Stabilizers added. However, this 1,1,1-trichloroethane containing stabilizers is under extreme conditions Conditions, such as steam cleaning and ultrasonic cleaning, in contact with such M ^ metals, such as aluminum, iron, zinc and brass, it is difficult to get results with it which are satisfactory in every way. The differences in the cleaning conditions also have an effect in the various workshops on the stability of 1,1,1-trichloroethane. For example, the Stability of 1,1,1-trichloroethane, which contains the same stabilizer, under so different conditions, such as the type and size of the cleaning machine, the heating method, the type and The size of the metals to be cleaned, the size and accumulation of the pieces of metal, the type of cutting oil, the method of distillation and recovery, the number of purifications and the amount depending on the added water.

If 1,1,1-trichloroethane is used as a metal cleaning agent, water is added to it not desirable as this leads to the hydrolysis of 1,1,1-trichloroethane. Especially in one system. in the presence of aluminum and water together, 1,1,1-trichloroethane decomposes accelerated. Therefore, the addition of water to 1,1,1-trichloroethane usually becomes very little deems desirable. In practice, however, the 1,1,1-trichloroethane vapor is cooled and condensed the moisture in the air in the cooler of the steam cleaning machine also gradually condensed in this cooler, until finally the water content of the 1,1,1-trichloroethane the saturation state reached In addition, there are some cutting oils that are water-soluble and if these are used in the machining of a metal part, it follows that that a small amount of water adheres to the machined part. This metal part is now using When 1,1,1-trichloroethane is cleaned, water is added to it. Since water enters the cleaning system in this way, the stability of the 1,1,1-trichloroethane leaves nothing to be desired strong after, which leads to the fact that either decomposition of the 1,1,1-trichloroethane takes place or the surface of the metal becomes susceptible to rust.

The object of the present invention is to provide 1,1,1-trichloroethane that is not only effective against aluminum, but also is stabilized against such metals as iron, zinc and brass.

Another object of the invention is to provide a stabilized 1,1,1-trichloroethane which is improved Has stability when used in systems containing water.

The invention thus provides a stabilized 1,1,1-trichloroethane, which, based on 1,1,1-trichloroethane, 0.1 to 5.0 percent by weight and preferably 1 to 4 percent by weight 1,4-dioxane, 0.01 to 1.0 percent by weight and preferably 0.1 to 0.5 percent by weight acrylonitrile, 0.05 to 3.0 percent by weight and preferably 0.1 to 1.0 percent by weight of an alkyl acetate, which has 1 to 5 carbon atoms in the alkyl group, and 0.05 to 3.0 percent by weight and preferably 0.1 to 1.0 percent by weight of a nitroalkane containing 1 to 3 carbon atoms.

Usable alkyl acetates are, for example, methyl acetate, ethyl acetate and propyl acetate; Ethyl acetate is special preferred.

Nitromethane and nitroethane are particularly suitable as nitroalkanes.

A small amount of a phenolic antioxidant can also be added to keep it oxidative Prevent decomposition of the stabilizer.

The following examples serve to illustrate the invention.

The following test methods 1 and 2 were used in the examples:

Test method 1 is a reflux corrosion test using the Conditions are similar to those in a real cleaning machine. On the other hand, the test method represents 2 represents a test to determine the corrosion caused by the hydrolysis of 1,1,1-trichloroethane is caused. In this case, the test is carried out with a volume ratio of the 1,1,1-trichloroethane test liquid to water of 1: 1 and carried out in the state where the water layer is above the 1,1,1-trichloroethane layer stands, i.e. in the stage the presence of a large excess of water (in practice, water cannot be so large in Quantities are available). This test is used to determine the stability of the invention 1,1,1-trichloroethane under such conditions. Because in a system with excess water, like that described, migration of the stabilizer in the water, solution of 1,1,1-trichloroethane in the water and hydrolysis of 1,1,1-trichloroethane take place, this can be used as a method of testing stability of 1,1,1-trichloroethane, under extreme conditions, viewed from a different point of view will.

2 134

Examples

Test method 1
Corrosion test by refluxing

Three 100 ml flasks, each equipped with a reflux condenser, are each charged with 100 ml of 1,1,1-trichloroethane test liquids which contain the stabilizers shown in Table 1 in the amounts indicated, whereupon 0.1 ml of water is added. Two aluminum test pieces (measuring 40 × 20 × 5 mm), the surface of which has been carefully polished, are then placed in each tub. One piece is placed in the test liquid and another similar test piece is suspended in the vapor phase. This flask is then immersed in a bath heated to 12O ⁰ C oil bath and heated under reflux, either until the decomposition of 1,1,1-trichloroethane is taking place or for the prescribed period of time (50 hours). The test pieces are then cooled to room temperature and the state of corrosion is determined. Furthermore, to determine the extent of the decomposition of the test liquid, the pH of the liquid is measured before and after the test. The same test is done with iron and brass. The results obtained are shown in Table 2.

In the table, the symbol O means that none Corrosion has occurred while the symbol Δ indicates either partial corrosion or loss des Gianzes has occurred, and the symbol χ means that the test piece has been corroded.

Method for determining the pH value

50 ml of the test liquid and 50 ml of pure water (pH 6.0) are placed in a separating funnel, then carefully shaken and allowed to settle. Then the top layer is removed and their pH value is determined with a pH meter

Table 1

attempt

Control 1.
Control 2.
Control 3.
Control 4.
Control 5,

Example 1.
Example 2.
Example 3.
Example 4.

Stabilizer (weight percent)

1,4-dioxane

3.0 3.0 2.5 3.0 3.0

3.0

2.5
3.0
2.5

Acrylonitrile

0.3

0.3 0.3 *)

0.3 0.3 0.3 0.3

Ethyl acetate

0.5 0.5 0.5

0.5

1.0

0.3 ** 0.5

Nitromethane

0.3 0.3

0.3

0.3 0.3 0.3 0.5 ***)

*) Acetonitrile is added instead of acrylonitrile.

**) Propyl acetate is added instead of ethyl acetate.

** ·) Nitroethane is added instead of nitromethane.

Table 2
Corrosion test by heating under reflux

attempt

metal
in the
liquid

Control 1
Control 2
Control 3
Control 4
Control 5

Example 1 .,

Example 2.,

Example 3 ..

Example 4 ..

aluminum

O O O O O

O O O O

metal
in the
Vapor phase

Δ
O

O O O

O O O O

PH
the liquid

before after

(3.0
6.1
5.9
5.8
5.8

5.9
5.8
5.8
5.9

3.5 5.2 5.1 5.2 5.5

5.8

5.7 5.7 5.7 iron

Metal in the liquid

O O O O

OOOO metal
in the
Vapor phase

Δ
Δ
Δ
O
O

O O O O

pH

the liquid
before after

6.0
6.1
5.9
5.8
5.8

5.9
5.8
5.8
5.9

3.7
4.7
4.4
5.1
5.4

5.8
5.8
5.6

5.7

Brass

metal
in the
liquid

O
χ χ

O O O O

Metal in the vapor phase

O χ

O O O O

pH of the liquid

before after

6.0 6.1 5.9 5.8 5.8

5.9 5.8 5.8 5.9

5.5 3.5 3.7 5.5 5.9

5.6 5.7 5.6 5.6

Test method 2 Corrosion test by hydrolysis of 1,1,1-trichloroethane

The 1,1,1-trichloroethane test liquid is with Water mixed in a volume ratio of 1: 1, whereupon 150 ml of the mixture is placed in a 200 ml flask and after careful Stir, allow to settle for about a minute.

There is a separation into an upper and a lower layer. An aluminum test piece (dimensions 40 20 χ χ 5 mm) whose surface was carefully polished, it is then immersed in the lower layer and 1,1,1-trichloroethane in a temperature-constant-container maintained at 5O ⁰ C is introduced for 5 hours. At the end of this period, the state of corrosion of the aluminum test piece is determined. The results are shown in Table 3.

Table 3
Corrosion test by hydrolysis

attempt

Composition of the stabilizer (percent by weight) 1,4-Dioxane Acrylonitrile Ethylacetate Nitromethane State of the test piece

Control 1.
Konirolle 2.

Example 1 ..
Example 2 ..

3.0
3.0

3.0
2.5

0.3 0.3

0.3 0.3

0.5

0.5 0.5

From the results compiled in Tables 1 and 2 it can be seen that the inventive, stabilized 1,1,1-trichloroethane no corrosion of aluminum, iron and brass when Test produced by refluxing and thus proving its excellent stability.

From Table 3 it can be seen that the 4 types of stabilizers added to the 1,1,1-trichloroethane become, due to the synergistic effect of this, excellent stability even in the case of presence an excess of water.

the whole surface is black a large part of the surface is black

0.3 about half of the surface is brown

0.5 about half of the surface is brown

Test report
There were comparative tests with

a) Trichloroethane, containing 4 percent by volume of dioxane and 0.1 percent by volume of nitromethane, and

b) trichloroethane, containing 4 percent by weight of dioxane, 0.1 percent by weight of nitromethane, 0.01 percent by weight Acrylonitrile and 0.05 percent by weight methyl acetate

carried out.

The results obtained according to test method 1 above are shown in Table 4 below summarized.

Tabel

metal
in the
Fluid
speed aluminum the Flü
before λ
sweetness
thereafter Meiall
in the
Fluid
speed iron P.
the Flü
before H
sweetness
thereafter metal
in the
Fluid
speed Brass Pl
the Flü
before sweetness
thereafter attempt O metal
in the
steam
phase 6.0 4.9 O metal
in the
steam
phase 6.0 4.5 X metal
in the
steam
phase 6.0 3.5 a O O 6.0 5.5 O Λ 6.0 5.5 O X 6.0 5.5 b O O Λ

The characters O, Δ and χ have the meaning given above.

The results obtained according to test method 2 are summarized in Table 5 below.

Tabel

attempt

Composition of the stabilizer (%) * 1,4-dioxane nitromethane acrylonitrile ethyl acetate

Condition of the test piece

4.0
4.0

*) a: volume percent,
b: weight percent.

0.1
0.1

0.01

most of the surface is black about two thirds of the surface is brown

The above experiments show that the object according to the invention, 1,1,1-trichloroethane, does not is stabilized only against aluminum but also against other metals, d. H. a general purpose stabilizer for Metals to be supplied cannot be dissolved according to British patent specification 832 055.

Claims (1)

Claim: Stabilized 1,1,1-Trichloräthaii, thereby characterized in that it, based on 1,1,1-trichloroethane, 0.1 to 5.0 percent by weight 1,4-dioxane, 0.01 to 1.0 weight percent acrylonitrile 0.05 to 3.0 weight percent of an alkyl acetate having 1 to 5 carbon atoms in the alkyl group and 0.05 to 3.0 weight percent of a nitroalkane containing 1 to 3 carbon atoms has, contains.