JPS5852967B2 - Method for stabilizing methyl chloroform - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for stabilizing methylchloroform.

More specifically, the present invention relates to a method of dramatically improving the stability of methyl chloroform by adding a co-stabilizer to methyl chloroform stabilized with a stabilizer.

Methyl chloroform (1,1,1-1-lichloroethane)
is a nonflammable solvent with excellent dissolving power, and is used for cleaning metals.
Widely used as a general industrial solvent.

Furthermore, methylchloroform has lower physiological toxicity than perchlorethylene or trichlorethylene, and is an excellent solvent in terms of pollution and hygiene.

However, methylchloroform is inferior to perchlorethylene and trichlorethylene in terms of stability.

Also, while perchlorethylene and trichlorethylene are unsaturated chlorinated hydrocarbons, methylchloroform is a saturated chlorinated hydrocarbon, so it cannot be discussed in the same way as perchlorethylene and trichlorethylene as a stabilizer. .

Decomposition of methylchloroform occurs due to the action of metals and heat.

For example, in the case of metal cleaning, methyl chloroform begins to decompose due to the catalytic action of the metal, and once this decomposition begins, it progresses in a chain reaction.

Furthermore, the decomposition is further accelerated by heating or in the presence of water.

As a result, hydrogen chloride and the like are generated, which corrode the metals and equipment being cleaned.

Particularly in the case of vapor degreasing and cleaning of metals, methyl chloroform is always distilled under heat, which is a harsh condition for the stability of methyl chloroform.

There is a need for methyl chloroform that is sufficiently stabilized to withstand this vapor degreasing process for extended periods of time.

Conventionally, various stabilizers for methyl chloroform have been known.

For example, typical examples include cyclic ethers, saturated alcohols, unsaturated alcohols, nitroalkanes, alkylene oxides, carboxylic acid esters, nitriles, phenols, amines, etc., used alone or in combination of two or more.

However, methyl chloroform stabilized with these conventional stabilizers is still not sufficiently stable.

When metals are actually vapor degreased and cleaned, methyl chloroform is always distilled under heat, and it is difficult to prevent some water from getting mixed into the solvent.

Therefore, it is necessary to demonstrate satisfactory stability in a test that corresponds to actual working conditions, that is, a test conducted under harsh conditions in which methyl chloroform containing some water is heated under reflux for a long time in the presence of metal pieces. However, such methylchloroform has not been found.

Therefore, the present inventors conducted studies to further improve the stability of methyl chloroform containing conventional stabilizers.

As a result, methyl chloroform stabilized by a conventional stabilizer is further combined with -R1\ general formula N''-0H R2/ (wherein R1 and R2 are a hydrogen atom, an alkyl group having 6 or less carbon atoms, or a cyclic alkyl group). It has been found that the stability of methylchloroform can be significantly improved by adding one or more selected from hydroxylamines or salts thereof.

The characteristics of the methyl chloroform stabilized according to the present invention are that it cannot be used under the harsh conditions of actual use, namely, heating under reflux for a long time in the presence of metal pieces with methyl chloroform mixed with some water. The purpose is to exhibit a sufficient stabilizing effect.

This is extremely important when methylchloroform is used industrially.

R1\ In the present invention, the hydroxylamines represented by the general formula N-0H R2/ (wherein R1 and R2 represent a hydrogen atom, an alkyl group or a cyclic alkyl group having 6 or less carbon atoms) include, for example, N-methyl Hydroxylamine, N,N-dimethylhydroxylamine,
N-methyl/N-ethylhydroxylamine, N-ethylhydroxylamine, N,N-diethylhydroxylamine, N.

N-dipropylhydroxylamine, N,N-te
rt-7'' hydroxylamine, N-cyclohexylhydroxylamine, etc. can be used, and the salts of hydroxylamine include, for example, sulfate, nitrate, hydrochloride, phosphate, sulfamate, acetate, and oxalate. , maleate, fumarate, salicylate, chloroacetate, etc. can be used.

Particularly preferred among these is N,N-diethylhydroxylamine or its salts.

Any amount of costabilizer added to stabilized methyl chloroform is effective, but it is appropriate to add from o, ooi to 1% by weight in view of the balance between stabilizing effect and cost.

The type of methyl chloroform stabilizer used in combination with the co-stabilizer is not particularly limited, and all conventionally known stabilizers may be used.

Typical conventionally known stabilizers include the following, and in many cases, two or more of these stabilizers are used in combination, and the amount of each stabilizer added is 0.1 to 5% by weight. is common.

Cyclic ethers: 1,4-dioxane, 1°3-dioxane, tetrahydrofuran, l.

3.5-1-lioxane, Saturated alcohols: Methyl alcohol Ethyl alcohol, tert-7” methyl alcohol Unsaturated alcohols: Allyl alcohol, Flopargyl alcohol Nitroalkanes: Nitromethane, nitroethane, nitropropane, Alkylene oxides: Propylene oxide, butylene oxide, epichlorohydrin nitriles: acrylonitrile, acetonitrile, propionitrile carboxylic acid esters: ethyl acetate, methyl acetate, methylpropionate, methylphenol methacrylate:
Phenol, cresol, 2.6-tert-butyl-para-cresol Tmines, diallylamine, cyclohexylamine, n-butylamine, etc. nigericidyl ethers, glycidyl esters, amides, imides Examples of the present invention are given below. Although the present invention will be specifically explained using examples and comparative examples, the present invention is not limited only to these examples.

Note that all percentages in Examples and Comparative Examples are expressed by weight.

Example Methyl chloroform 201 is placed in a 500-sized Erlenmeyer flask equipped with a reflux condenser, a predetermined amount of stabilizer is added, and then 0.5 ml of water is added.

To this, iron (Fe), aluminum (Al), zinc (Zn), which was polished with sandpaper in advance, washed and dried.
Place three types of metal pieces (2 x 15 x 50 mm), one each in the gas phase and liquid phase inside the flask, and
Place in a constant temperature bath maintained at ~98°C and heat under reflux for 24 hours.

After 24 hours, the liquid is cooled and the corrosion state of the test piece is observed.

For convenience, the state of corrosion of the Test 1 specimen was classified into the following five stages and evaluated.

A: No corrosion B: Slight corrosion is observed.

C: Considerable corrosion is observed.

D: Significant corrosion.

E: Fully corroded.

The results of the examples are shown in Table 1.

Comparative Example The results of the comparative example, which was tested in the same manner as the example, are shown in the second example.
Shown in the table.

As can be seen from the comparison between Tables 1 and 2, by adding the co-stabilizer of the present invention to methyl chloroform stabilized with a conventional stabilizer, the It is clear that the stability of methyl chloroform is dramatically improved.

Claims (1)

[Scope of Claims] 1. To methyl chloroform stabilized with a stabilizer, a co-stabilizer of the general formula 1% (wherein R1 and R2 are a hydrogen atom, an alkyl group having 6 or less carbon atoms, or a cyclic alkyl group) is added. A method for stabilizing methylchloroform, which comprises adding one or more selected from the hydroxylamines or salts thereof shown in the following. 2. The stabilization method according to claim 1, wherein at least one type of stabilizer is cyclic ethers, alcohols, nitroalkanes, alkylene oxides, carboxylic acid esters, or phenols.