EP0609125B1 - Stabilized cleaning composition based on 1,1-dichloro-1-fluoroethane and methanol - Google Patents

Description

The present invention relates to the field of chlorofluorinated hydrocarbons and more particularly relates to a stabilized composition based on 1,1-dichloro-1-fluoroethane and methanol, usable as a cleaning and degreasing of solid surfaces, in particular in defluxing circuits printing and degreasing of mechanical parts.

1,1,2-Trichloro-1,2,2-trifluoroethane, known in the art as designation F113, is widely used in the industry for cleaning and degreasing of solid surfaces. It is however part of the chlorofluorocarbons perhalogens (CFCs) suspected of attacking and degrading stratospheric ozone, and will therefore have to be replaced in the short term by substitutes having little or no destructive effect with respect to ozone, such as 1,1-dichloro-1-fluoroethane.

The latter compound, known in the art under the designation F141b, has the advantage, like F113, of forming a composition with methanol azeotropic particularly useful for cleaning operations (patents EP 325,265, US 4,842,764 and JP 2,273,632).

Whether the chlorofluorinated hydrocarbon associated with methanol is F113 or F141b, it is necessary to stabilize the azeotropic composition to avoid attack of metals by methanol leading to the formation of hydrogen. The nitromethane is usually used to stabilize the azeotropic composition F113-methanol and this same compound has also been proposed in the patent US 4,816,174 as stabilizer of the azeotropic composition F141b-methanol. As other compounds capable of being used to stabilize this azeotropic composition, US Pat. No. 4,842,764 mentions the amines secondary and tertiary, olefins and cycloolefins, alkylene oxides, sulfoxides, sulfones, nitrites and nitriles, and acetylenic alcohols or ethers.

Document US-A-5 124 063 describes degreasing compositions comprising F-141b, methanol, dichlorotrifluoroethane and an alkane having 5 to 6 carbon atoms, can be stabilized with (in particular) 1,4-dioxane or dimethoxyethane.

Document JP 2 273 632 cited above indicates, without specifying their role, that other constituents can be added to the azeotropic composition F141b-methanol and, as such, lists various compounds including ethers such as methylcellosolve, tetrahydrofuran and 1,4-dioxane. These last two ethers have have also been studied, along with sixty other compounds of very diverse in nature, as inhibitors of the reaction of aluminum with chlorinated solvents such as 1,1-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane or the 10/90 toluene / dichloromethane mixture (W.L. Archer, "Comparison of chlorinated solvent-aluminumm reaction inhibitors", Ind. Eng. Chem. Prod. Res. Dev., Vol. 18 (2) 1979, 131-135).

It has now been found that dimethoxymethane and 1,3-dioxolane are excellent stabilizers for F141b-methanol compositions. They allow indeed to inhibit the reaction of methanol with light metals such as aluminum and magnesium (very sensitive) and exhibit very different behavior in this respect that of very similar compounds such as dimethoxyethane, diethyl ether, methyl tert-butyl ether, furan and tetrahydrofuran.

The subject of the invention is therefore a cleaning composition based on F141b and methanol, characterized in that it contains, as a stabilizer, 0.01 to 1% (preferably 0.1 to 0.5%) of dimethoxymethane or 1,3-dioxolane based on the total weight of methanol and F141b.

In the compositions according to the invention, the proportion by weight of methanol is advantageously between 0.2 and 10% and that of F141b between 99.8 and 90%. A more particularly preferred composition is that in which the respective proportions of methanol and F141b correspond approximately to the azeotropic composition, ie 3 to 5% of methanol and 97 to 95% of F141b.

The compositions according to the invention do not have a flash point in the standard determination conditions and can therefore be used safely in machines usually used for cleaning welding fluxes, the degreasing heavy metal parts or cleaning mechanical parts high quality and high accuracy such as, for example, gyroscopes and military or aerospace equipment.

The following examples illustrate the invention without limiting it.

EXAMPLE 1

A composition according to the invention is prepared by adding 0.2% by weight (i.e. 12 g) of 1,3-dioxolane to 5 liters of azeotropic mixture F141b-methanol (96% F141b and 4% methanol), then this composition is introduced into a small BRANSON cleaning machine and reflux door for 4 hours to that the system is in balance.

An aliquat of the condensate return is then taken and analyzed by vapor phase chromatography. Examination of the results reported in the following table shows the presence of 1,3-dioxolane in the collected fraction, which indicates that the composition according to the invention is also stabilized in the vapor phase. COMPOSITION (% by weight) F141b Methanol 1,3-dioxolane Initial mix 95.8 4 0.2 Collected fraction 96.08 3.8 0.12

EXAMPLE 2

Example 1 is repeated, replacing the 12 g of 1,3-dioxolane with 24 g of dimethoxymethane (0.4% by weight). After 4 hours of reflux so that the system is in equilibrium, the analysis of a fraction of the condensate returns by gas chromatography indicates that the vapor phase is stabilized. COMPOSITION (% by weight) F141b Methanol dimethoxymethane Initial mix 95.62 3.98 0.40 Collected fraction 95.77 3.99 0.24

EXAMPLE 3

100 ml of the composition are introduced into a 250 ml flask. Example 1 and 0.25 g of activated magnesium, then the mixture is brought to reflux. After a week of reflux, the analysis of the composition does not reveal any difference from the initial composition, thus demonstrating the inhibitory effect of 1,3-dioxolane on the reaction of magnesium and methanol.

It is the same if we replace 1,3-dioxolane by the same proportion of dimethoxymethane.

On the contrary, if we replace 1,3-dioxolane with the same proportion of methyl tert-butyl ether, furan, diethyl ether, dimethoxyethane or tetrahydrofuran, the reaction between magnesium and methanol starts at reflux.

EXAMPLE 4

In a small single-tank laboratory machine equipped with a generator 125 ml of the composition of Example 1 are introduced, then the liquid when boiling.

Five standardized test circuits (IPC-B-25 model), coated with solder flux rosin-based (R8F flux from ALPHAMETAL), annealed at 230 ° C for 30 seconds and cooled, are immersed for 3 minutes in the liquid to boil under ultrasound, then rinse in the vapor phase for 3 minutes.

After air drying, the quality of the cleaning is evaluated by determining the ionic residue rate according to the standard procedure IPC-TM 650 n ° 2.3.25 and 2.3.26 and according to the MIL-STD-2000 standard. The value obtained, 1.87 µg eq.NaCl / cm ² , is much lower than the threshold (2.5 µg eq. NaCl / cm ² ) tolerated in the field of electronics.

EXAMPLE 5

Example 4 is repeated, but with the composition of Example 2 stabilized at dimethoxymethane.

The rate of ionic residue is then 1.86 μg eq. NaCl / cm ² .

Claims (5)

1. Cleaning composition based on 1,1-dichloro-1-fluoroethane and methanol, characterized in that it contains, as stabilizing agent, from 0.01 to 1 % of dimethoxymethane or of 1,3-dioxolane with respect to the total weight of methanol and 1,1-dichloro-1-fluoroethane.
2. Composition according to Claim 1, in which the proportion of dimethoxymethane or of 1,3-dioxolane is between 0.1 and 0.5 %.
3. Composition according to Claim 1 or 2, in which the methanol represents 0.2 to 10 %, preferably 3 to 5 %, of the total weight of methanol and of 1,1-dichloro-1-fluoroethane.
4. Application of a composition according to one of Claims 1 to 3 to cleaning solid surfaces.
5. Application according to Claim 4 to defluxing printed circuits and to degreasing mechanical components.