FR2700776A1 - Stabilized cleaning composition based on 1,1-dichloro-1-fluoroethane and methanol. - Google Patents

Abstract

Dimethoxymethane or 1,3-dioxolane is used as stabilizer of a composition based on 1,1-dichloro-1-fluoroethane and methanol, intended for cleaning solid surfaces.

Description

-1 - f STABILIZED CLEANING COMPOSITION BASED ON

  1,1-DICHLORO-1-FLUOROETHANE AND METHANOL

  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 an agent for cleaning and degreasing solid surfaces, in particular in the defluxing of circuits

  printing and degreasing of mechanical parts.

  1,1,2-Trichloro-1,2,2-trifluoroethane, known in the art under the designation F 113, is widely used in industry for cleaning and degreasing solid surfaces It is, however, part of perhalogenated chlorofluorocarbons (CFC) suspected of attacking and degrading stratospheric ozone, and will therefore have to be replaced in the short term by substitutes with little or no

  destructive effect with respect to ozone, such as 1,1-dichloro-1fluoroethane.

  The latter compound, known in the art under the designation F 141 b, has, like F 113, the advantage of forming with methanol an azeotropic composition which is 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 F 113 or F 141 b, it is necessary to stabilize the azeotropic composition to avoid attack of the metals by methanol leading to the formation of hydrogen Nitromethane is usually used to stabilize the azeotropic composition F 113-methanol and this same compound has also been proposed in the patent

  US 4,816,174 as stabilizer of the azeotropic composition F 141 b methanol.

  As other compounds capable of being used to stabilize this azeotropic composition, US Pat. No. 4,842,764 mentions secondary and tertiary amines, olefins and cycloolefins, alkylene oxides,

  sulfoxides, sulfones, nitrites and nitriles, and acetylenic alcohols or ethers.

  Document JP 2 273 632 cited above indicates, without specifying their role, that

  other constituents can be added to the azeotropic composition F 141 b-

  methanol and, as such, lists various compounds including ethers such as methylcellosolve, tetrahydrofuran and 1,4-dioxane These last two ethers have also been studied, along with around sixty other compounds of very various, as inhibitors of the reaction of aluminum with

  chlorinated solvents such as 1,1-dichloroethane, 1,1,1trichloroethane, 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).

  -2 - It has now been found that dimethoxymethane and 1,3dioxolane are excellent stabilizers for compositions F 14 lbmethanol They indeed make it possible to inhibit the reaction of methanol with light metals such as aluminum and magnesium ( very sensitive) and exhibit in this respect a behavior very different from 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 F 141 b and methanol, characterized in that it contains, as stabilizer, from 0.01 to 1% (preferably 0.1 to 0, 5%) of dimethoxymethane or 1,3-dioxolane

  relative to the total weight of methanol and F 141 b.

  In the compositions according to the invention, the weight proportion of methanol is advantageously between 0.2 and 10% and that of F 141 b between 99.8 and 90% A more particularly preferred composition is that in which the respective proportions of methanol and of F 141 b correspond substantially to the azeotropic composition, that is to say 3 to 5% of methanol and 97 to 95% of

F 141 b.

  The compositions according to the invention do not have a flash point under standard conditions of determination and can therefore be used without danger in the machines usually used for cleaning weld fluxes, 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 (ie 12 g) of 1,3-dioxolane to 5 liters of azeotropic mixture F 141 b methanol (96% FI 41 b and 4% methanol), then this composition is introduced into a small BRANSON cleaning machine and brought to reflux 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 fraction collected, which indicates that the composition according to the invention is also stabilized in phase

steam.

-3-

EXAMPLE 2

  Example I 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 condensate returns by

  Gas chromatography indicates that the vapor phase has stabilized.

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 reveals no difference compared to the initial composition, thus demonstrating the inhibitory effect of the

  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 an ultrasound generator, 125 ml of the composition of Example 1 are introduced, then the

liquid when boiling.

  Five standardized test circuits (model IPC-B-25), coated with rosin-based solder flux (flux R 8 F from the company ALPHAMETAL), annealed at 230 C during COMPOSITION (% by weight) F 141 b Methanol 1.3- dioxolane Initial mixture 95.8 4 0.2 Fraction collected 96.08 3.8 0.12 COMPOSITION (% by weight) F 141 b Methanol dimethoxymethane Initial mixture 95.62 3.98 0.40 Fraction collected 95.77 3.99 0.24 -4- 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 level 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 pg eq Na CI / cm 2, is very

  below the threshold (2.5 pg eq Na CI / 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 pg eq Na CI / cm 2.

-5-

Claims (4)

  1 Cleaning composition based on 1,1-dichloro-1-fluoroethane and methanol, characterized in that it contains, as stabilizer, 0.01 to 1% of dimethoxymethane or 1,3-dioxolane by relative 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 1,3-dioxolane is between 0.1 and 0.5%.   3 Composition according to claim 1 or 2, in which methanol   represents 0.2 to 10%, preferably 3 to 5%, of the total weight of methanol and 1.1- 1-dichloro-fluoroethane.   4 Application of a composition according to one of claims I to 3 to cleaning of solid surfaces.   Application according to claim 4 for defluxing printed circuits and   degreasing of mechanical parts.