JPH0531530B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for stabilizing 1,2-dichloro-1,1-difluoroethane (hereinafter referred to as Freon 132b). Freon 132b is nonflammable, has low toxicity, and has excellent solubility and an appropriate boiling point, so it can be used as a cleaning agent for various articles. For example, semiconductor materials such as silicone wafers and silicon chips, semiconductors such as ICs and LSIs, printed wiring boards,
Electronic and electrical equipment such as relay switches, micro motors, watches, cameras, micro bearings,
Useful as a degreasing agent for precision instruments such as lenses. (Prior Art) Freon 132b has not yet been practically used in industry, and many aspects of its properties are unknown. Among them, it exhibits a decomposition behavior different from conventional chlorine-based solvents and fluorine-based solvents that do not contain fluorine atoms or hydrogen atoms, so no sufficient method for stabilizing it is known yet. (Problems to be solved by the invention) Freon 132b is more stable than chlorinated solvents such as methyl chloroform, tetrachlorethylene, and trichlorethylene, and stabilization is not necessarily required under general usage conditions. However, its stability may still be a problem when moisture coexists or when quality requirements are high and strict, such as when cleaning electronic equipment or precision equipment. In particular, when solvents deteriorate in the presence of metal materials such as copper, zinc, and iron, which are often used in electronic/electrical equipment and precision equipment, it will also cause corrosion of these metals, and the adversely affect the quality of products. (Means for Solving the Problems) The present inventors have conducted various studies in an attempt to improve the stability of Freon 132b, and as a result, they have found a method and arrived at the present invention. That is, the present invention is a method for stabilizing 1,2-dichloro-1,1-difluoroethane, which is characterized by adding one or two selected from N-methylformoline and nitromethane and benzotriazole. Although the amount of stabilizer added in the present invention is not particularly limited, it is usually 5% by volume or less for N-methylformoline and nitromethane, and 3000 ppm by weight or less for benzotriazole based on the solvent. If the amount added is larger than this, it is not a good idea because the liquid may become colored, become precipitated as insoluble matter, or become flammable. Furthermore, the method of the present invention can also be applied to mixed solvents containing Freon 132b as a main component. In other words, mixed solvents in which a small amount of methanol, ethanol, isopropanol, isobutanol, tert-butanol, acetone, methyl ethiketone, ethyl acetate, methylene chloride, etc. are added to Freon 132b may be used as long as the solvent properties of Freon 132b are not significantly changed. Its application is possible. (Effects of the Invention) Freon 132b stabilized by the present invention and its mixed solvent have extremely high chemical stability;
Since it rarely corrodes metal materials such as copper, zinc, and iron, it can be widely used as a cleaning agent in various fields. (Example) The present invention will be explained below using examples. In addition, the stability test in Examples was conducted by the following method. Stabilizers are indicated by the following abbreviations. N-Methylmorpholine: NMM Nitromethane: NM Benzotriazole: BTA Stability test: Place 50 ml of the sample in a 100 ml glass bottle, and place a well-polished metal test piece of zinc, copper, iron, etc. in the lower half of the bottle. Pour the tube so that it touches the liquid phase, seal it, and treat it at 60℃ for 96 hours. The corrosion state of the metal piece is observed separately in the part exposed to the gas phase and the part immersed in the liquid phase. Example 1 Freon 132b containing 800 ppm of water and Table-
A stability test was conducted using zinc as a metal test piece, using samples with and without the addition of the various stabilizers shown in 1. For comparison, a stability test was also conducted on Freon 132b without any stabilizer added. The results are shown in Table-1. Example 2 The same test as in Example 1 was conducted except that copper was used as the metal test piece. The results are shown in Table-2. Example 3 The same test as in Example 1 was conducted except that iron was used as the metal test piece. The results are shown in Table-3. Example 4 NMM was added as a stabilizer to a mixed solvent of Freon 132b containing 1100 ppm by weight of water and 5% by volume of ethanol.
A stability test was conducted using iron, zinc, and copper as metal test pieces, using a sample containing 2% by volume of BTA and 100 ppm by weight of BTA in a mixed solvent. For comparison, a mixed solvent without any stabilizer was used. The results are shown in Table 4.

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Claims (1)

[Claims] 1,2-dichloro- characterized in that one or two selected from N-methylmorpholine and nitromethane and benzotriazole are added.
Method for stabilizing 1,1-difluoroethane.