IE912847A1

IE912847A1 - Cleaning composition based on 1,1-dichloro-1-fluoroethane,¹methylene chloride and methanol

Info

Publication number: IE912847A1
Application number: IE284791A
Authority: IE
Original assignee: Atochem
Priority date: 1990-08-14
Filing date: 1991-08-12
Publication date: 1992-02-26
Also published as: FI913828A0; NO912814L; NO912814D0; BR9103360A; KR920004559A; FI913828A; JPH04239599A; FR2665907B1; PT98668A; CA2048158A1; FR2665907A1; CN1059167A; EP0474528A1; AU8243991A

Abstract

To replace cleaning compositions based on 1,1,2-trichloro- 1,2,2-trifluoroethane (F113) the invention proposes a composition comprising, by weight, 60 to 98.9 % of 1,1-dichloro-1-fluoroethane (F141b), 0.1 to 39 % of methylene chloride and 1 to 39.9 % of methanol. The composition, optionally stabilised, can be employed for cleaning solid surfaces, in particular for defluxing printed circuits and for degreasing mechanical components.

Description

The present invention relates to the field of chlorofluorohydrocarbons and, more particularly, to a composition which can be employed as an agent for cleaning and degreasing solid surfaces, in particular in the defluxing and cold cleaning of printed circuits. l,l,2-Trichloro-l,2,2-trifluoroethane (known in the art under the code name F113) is widely employed in industry for cleaning and degreasing solid surfaces. Apart from its application in electronics, for cleaning soldering fluxes to remove the scouring flux which adheres to the printed circuits, it is possible to mention its applications in the degreasing of heavy metal articles and the cleaning of high quality and high precision mechanical articles such as gyroscopes and military or aerospace hardware. In its various applications F113 is in most cases used in combination with other organic solvents (for example methanol), preferably in the form of azeotropic or pseudoazeotropic mixtures which do not demix and which, when employed at reflux, have substantially the same composition in the vapour phase as in the liquid phase.

However, F113 is one of the completely halogenated chlorofluorocarbons which are at present suspected of attacking or decomposing stratospheric ozone. To solve this problem it has already been proposed to replace F113 - 3 with various hydrochlorofluorocarbons and especially with 1,1-dichloro-l-fluoroethane. This compound, known in the art under the code name F141b, is practically devoid of any destructive action on ozone.

Its application to cleaning has recently formed the subject of numerous publications, most of which are concerned with azeotropic or pseudoazeotropic compositions based on F141b and on one or more solvents; see, for example, Japanese Patent Application Publication Nos. 124,195/87 (F141b + n-propanol), 124,196/87 (F141b + methylcyclohexane), 124,197/87 (F141b + 3-methyl-l-butyn-3ol), 124,198/87 (F141b + acetonitrile + n-propanol, isobutanol or 2-butanol), 127,398/87 (F141b + isopropyl acetate + isobutanol), 132,539/89 (F141b + methanol, ethanol, isopropanol, tetrahydrofuran or methyl ethyl ketone + stabiliser), EP-A-0,325,265 (F141b + methanol or ethanol) and US-A-4,816,174 and 4,842,764 (F141b + methanol + optionally nitromethane).

In a much more general way, Japanese Patent Application Publication No. 132,693/89, relating to cleaning agents for the removal of scouring fluxes, mentions that it is possible to add to F141b one or more organic solvents chosen from hydrocarbons, alcohols, ketones and chlorinated hydrocarbons. This reference lists more than a hundred such solvents, but the only ones specifically exemplified are n-heptane, methanol, acetone IE 91/847 - 4 and trichloroethylene, in the form of binary compositions containing 75 % of F141b and 25 % of cosolvent.

The cleaning power of F141b-methanol binary combinations is not always sufficient and, for some applications, it often seems necessary to reinforce it by the addition of another solvent. The choice of this other solvent is not obvious since it is necessary that the cleaning composition should be nonflammable and should have a pseudoazeotropic behaviour.

It has now been found, according to the present invention, that it is possible to obtain this result by using methylene chloride. The cleaning compositions according to the invention are characterised in that they comprise 60 to 98.9 % of F141b, 1 to 39.9 % of methanol and 0.1 to 39 % of methylene chloride, by weight.

Compositions comprising 80 to 90 % of F141b, 1 to % of methanol and 5 to 19 % of methylene chloride, by weight, are more particularly preferred.

Although the three constituents do not form any true azeotrope, their mixtures can be employed in a cleaning machine under the same conditions as compositions based on F113. In fact, one of the main advantages of the compositions according to the invention lies in the unexpected fact that, whatever the proportion of each constituent, the composition of the vapour phase is substantially the same as that of the liquid phase. This - 5 property makes it possible to modify the solvent power of the cleaning composition and hence to adapt it at will as a function of the surface to be cleaned or degreased.

The compositions according to the invention have no 5 flash point under the standard conditions of determination and can therefore be employed without danger.

As in the known compositions based on F113, the compositions according to the invention can be advantageously stabilised against hydrolysis and/or radical attacks capable of occurring in the cleaning processes, by adding thereto a conventional stabiliser such as nitromethane, propylene oxide or a mixture of these compounds, the proportion of stabiliser typically being from 0.01 to 5 % relative to the total weight of F141b + methylene chloride + methanol.

The compositions according to the invention can be employed in the same applications and using the same techniques as the previous compositions based on F113.

The following Examples further illustrate the present invention.

EXAMPLE 1 A mixture of F141b, methylene chloride and methanol is introduced into an Annemasse ultrasonic cleaning tank in the proportions which are mentioned in the table which follows. The mixture is then placed under total reflux for an hour to bring the system to equilibrium, and then a - 6 syringe is used to take a sample of a few millilitres from the neck of the machine in which the condensate collects. The fraction collected and a sample of the contents of the tank are then analysed, after cooling, using gas phase chromatography.

The following table collates the results obtained in three tests corresponding to different mixtures according to the invention. Their examination shows that the compositions (% by weight) of the starting mixture, of the fraction collected (vapour phase) and of the tank bottoms are substantially identical. Test 1 Test 2 Test 3 Startincr mixture F141 b 86.4 80 80 15 Methylene chloride 10 10 15 Methanol 3.6 10 5 Vapour phase F141 b 86.5 80.3 83 Methylene chloride 9.9 8.7 13 20 Methanol 3.6 11 4 Tank F141 b 86.4 80 80 Methylene chloride 10 10 15 Methanol 3.6 10 5 25 Boilincr temperature (corrected for 1.013 bar) 29.9°C 30.2°C 30.3eC By way of comparison, Test 1 was reproduced but with methylene chloride replaced with other chlorinated hydrocarbons, namely 1,1,1-trichloroethane (Till), carbon tetrachloride, trichloroethylene (TRI) and perchloroethylene (PER).

Examination of the results, which are listed in the following table, shows that, in contrast to methylene chloride, these chlorinated hydrocarbons result in a vapour phase composition which is very different from that of the liquid phase.

Comparative test No. 4 5 67 1 Test Chlorinated hydrocarbon Till CC1 4 TRI PER| ch2ci Initial mixture (weight %) 1 15 - F141 b 86.4 86.4 86.4 86.4 | 86.4 - Methanol 3.6 3.6 3.6 3.6 | 3.6 - Chlorinated hydrocarbon 10 10 1010 1 10 Vapour phase (weight %) 1 - F141 b 93.2 92.7 93.2 94.9 | 86.5 20 - Methanol 4.1 4.1 4.1 4.2 | 3.6 - Chlorinated hydrocarbon 2.7 3.2 2.7 0.9 | 9.9 EXAMPLE 2 150 g of a mixture containing 86.3 % of F141b, 10 % of methylene chloride, 3.6 % of methanol and 0.1 % of nitromethane as stabiliser, by weight, are introduced into - 8 an ultrasonic cleaning tank. After the system has been placed under reflux for an hour, an aliquot of the vapour phase is sampled. Its analysis by gas phase chromatography shows the presence of nitromethane, which indicates that the mixture is stabilised in the vapour phase.

EXAMPLE 3 When Example 2 is repeated with nitromethane replaced with propylene oxide, the following results are obtained: 1 Γ 1 1 1 h 1 1 I L 1 COMPOSITION (weight %) | F141b Γ ch2ci2 1 I 1 Methanol| I c3h6o | 1 Γ |Initial mixture | 86.3 1 10 | 1 3.6 | 0.1 1 |Vapour phase | 86.4 10 1 3.58 | 0.02 | - 9 EXAMPLE 4 200 g of the composition according to Test 1 are introduced into an Annemasse ultrasonic tank and the mixture is then heated to boiling temperature.

Printed circuits coated with soldering flux and annealed in the oven for 30 seconds at 220°C, are immersed for 3 minutes in the boiling liquid under ultrasound, and are then rinsed in the vapour phase for 3 minutes.

After drying in air, soldering flux residues are found to be completely absent.

Claims

1. A composition which comprises from 60 to 98.9 % of 1,1-dichloro-l-fluoroethane, from 0.1 to 39 % of methylene chloride and from 1 to 39.9 % of methanol, by 5 weight.

2. A composition according to Claim 1, which comprises from 80 to 90 % of 1,1-dichloro-lfluoroethane, from 5 to 19 % of methylene chloride and from 1 to 15 % of methanol, by weight. 10

3. A composition according to Claim 1 or 2, which additionally comprises at least one stabiliser.

4. A composition according to Claim 3, in which the stabiliser is nitromethane, propylene oxide or a mixture of these compounds. 15

5. A composition according to Claim 3 or 4, in which the amount of stabiliser is from 0.01 to 5 % relative to the total weight of the mixture of 1,1dichloro-l-fluoroethane + methylene chloride + methanol.

6. A composition according to claim 1 20 substantially as described in any one of Examples 1 to 3.

7. A method of cleaning a solid surface which comprises applying thereto a composition as claimed in any one of claims 1 to 6.

8. A method of defluxing a printed 25 circuit or degreasing a mechanical article which comprises applying thereto a composition as claimed in any one of claims 1 to 6.