GB2038865A

GB2038865A - Solvent Cleaning Composition

Info

Publication number: GB2038865A
Application number: GB7942318A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1978-12-13
Filing date: 1979-12-07
Publication date: 1980-07-30
Also published as: GB2038865B

Abstract

A cleaning composition for printed circuit boards consists of the azeotropic mixture of 1,1,2-trichloro- 1,2,2-trifluoroethane, a lower aliphatic monohydric alcohol together with a polyol, such as trihydroxymethyl ethane, trihydroxymethyl propane or trihydroxymethyl nitromethane.

Description

SPECIFICATION Cleaning Composition This invention relates to a cleaning composition comprising 1,1,2-trichloro-1,2,2,- triflurorethane and an aliphatic alcohol.

It is well known that constant boiling mixtures otherwise known as azeotropic mixtures of 1,1,2 trichloro-1 2,2,-trifluoroethane and the lower aliphatic alcohols for example, methanol, ethanol and isopropyl alcohol are useful for a variety of cleaning purposes for example in the cleaning of printed circuit boards to remove flux. However such mixtures may not be entirely satisfactory for cleaning printed circuit boards since often they do not remove all the flux, especially the more modern fluxes which are very difficult to remove.

It is an object of the present invention to provide a cleaning composition approximating to the azeotropic mixture of 1,1 ,2-trichloro-1 ,2,2- trifluoroethane and lower aliphatic alochols but which also contains a special additive whereby improved cleaning effects can be obtained.

According to the present invention we provide a cleaning composition comprising the approximate azetropic mixture of 1,1,2-trichloro 1 2,2-trifluoroethane and a monohydric lower aliphatic alcohol characterised in that it contains as additive a polyol of formula C(W) (X) (Y) (Z) wherein (W) and (X) which may be the same or different are each a hydroxyalkyl group or hydroxyalkoxy group each having 1 to 8 carbon atoms or a hydroxyalkylene group having 2 to 8 carbon atoms and (Y) and (Z) which may be the same or different are each a hydroxyalkyl group having 1 to 8 carbon atoms, a hydroxyalkylene group having 2 to 8 carbon atoms, hydrogen, an alkyl group having 1 to 8 carbon atoms, an alkylene group having 2 to 8 carbon atoms, or a nitro-group.

The preferred polyols are triols in which one of the groups (Y) and (Z) is an alkyl group.

Preferably the alkyl chain of the hydroxyalkyl or hydroxyalkoxy group and the alkylene chain of the hydroxyalkylene group contain 1 to 6 carbon atoms and 2 to 6 carbon atoms, respectively. The hydroxyalkyl and hydroxyalkylene group may contain more than one hydroxyl group and the hydroxyl group(s) may be attached to any one of the carbon atoms in the alkyl or alkylene chain.

Preferably a hydroxy group is attached to a terminal carbon atom.

When (W) is a hydroxyalkyl group one or more of (X) (Y) and (Z) is/are very suitably hydroxyalkyl groups. Such hydroxyalkyl groups are usually the same as (W), suitably the 2-hydroxyethyl group.

Typical examples of the polyol (triol) additives of the present compositions are 1,1 1 -tri(hydroxy methyl)-ethane, CH3C(CH2OH)3, and 1,1 ,1-tri (hydroxymethyl)-propane, CH3CH2C(CH20H)3.

Other polyol (diol) additives of the composition are those wherein (W) is a hydroxyalkyl group, (X) is a hydroxyalkoxy group (both suitably containing 1 to 6 carbon atoms) and (Y) and (Z) are each hydrogen. An example of the diol additives is one wherein (W) is a hydroxymethyl group and (X) is a hydroxypropoxy group, that is, diethylene glycol (H0CH2CH2OCH2CH2OH). Another example of a diol additive is one wherein (W) is a hydroxyethyl group and (X) is a hydroxypropoxy group that is, dipropylene glycol (CH3CH(OH)CH20CH2CH(OH)CH3).

The additive in the present cleaning composition preferably boils at temperatures above 10000 and is non-volatile under the conditions of use.

The phrase approximate azeotropic mixture means those mixtures which boil within +20C of the azeotropic mixture. Preferably the mixture boils with + 1 C of the azeotropic mixtures. More preferably the azeotropic mixture itself is employed.

If desired mixtures of monohydric aliphatic alcohols may be used. Preferably a monohydric aliphatic alcohol is employed having 1 to 3 carbon atoms. More preferably the aliphatic alcohol is methyl alcohol, ethyl alcohol or commercially available sources of ethyl alcohol containing 4% to 5% of methyl alcohol.

Quite small amounts of the polyol additive are required to obtain the improved cleaning effect in the present cleaning compositions. Usually there is employed at least 0.01% by weight of said additive in making up the cleaning effect in the present cleaning compositions for example, 0.01% to 1% by weight. Greater proportion by weight, may be used but there is no advantage in using a proportion greater than 1% since no further advantage is gained and greater proportions of additives necessarily lead to higher cost.

The compositions may if desired contain small amounts of other adjuvants, for example, a small amount of conventional stabilisers for the mixture of 1,1 ,2-trichloro-1 ,2,2-trifluoroethane and the monohydric lower aliphatic alcohol, for instance a small amount of a mononitroalkane, e.g.

nitromethane.

The compositions of the present invention may be used in conventional operating techniques.

Preferably the composition is employed at the boil. The contaminated article may be immersed in the cleaning composition or jetted with a spray of the cleaning composition. Suitably also the article after treatment with the cleaning composition is rinsed with a composition containing the trichlorotrifluoroethane and alcohol, suitably the azeotropic composition which may contain the polyol additive. The compositions are useful for a variety of cleaning purposes, for example in the removal of flux and other contaminants from articles. They are also useful in the removal of water from contaminated articles.

The present invention includes within its scope a process for making cleaning compositions characterised by incorporating the polyol additive and if desired with other additives into mixtures of 1,1 ,2-trichloro- 1 ,2,2-trifluoro ethane and said monohydric aliphatic alcohol. The invention also includes a method of cleaning contaminated articles by bringing them into contact with the cleaning composition as described hereinbefore.

The invention is illustrated by the following Examples. Where percentages are mentioned they are by weight.

Example 1 A conventional stainless steel degreasing unit was employed having a cleaning compartment and a rinsing compartment and a condenser running round the upper portion of the walls of the unit. The cleaning and rinsing compartments were both 25 cms long by 1 5 cms wide. Into the cleaning compartment there was placed to a depth of 10 cms a cleaning composition comprising a mixture of 1,1 2-trichloro 1,2,2trifluoroethane (95.0%), ethyl alcohol (4.5%), 1,1,1 -tri(hydroxymethyl)-ethane (0.5%) and nitromethane (0.05%).

Into the rinsing compartment an amount of a similar cleaning composition also initially containing 1 , 1 1 -tri(hydroxymethyl)-ethane (0.5%) was placed to a depth of 20 cms. The composition in both compartments was heated to boiling, the vapours were condensed and the condensate fed to the rinsing compartment. There was an overflow of composition from rinsing to cleaning compartment so that the polyol additive was removed from the rinsing compartment and passed to the cleaning compartment.

Printed circuit boards (size 5 cms by 2.5 cms) having a substrate of epoxy resin glass mat laminate and contaminated with a flux known as 'Zeva'C40 ('Zeva' is a Trade Mark) were dipped for periods of from 21 minute to 1 minute firstly in the cleaning compartment and then in the rinsing compartment. Printed boards which had been coated with a flux known as Fry's R8 were similarly treated.

The treated boards were all found to be perfectly clean and in particular were free from flux.

Comparison By way of comparison the above procedure was repeated but with merely the azeotropic mixture of 1,1,2- trichloro-1,2,2trifluoroethane and ethyl alcohol. After treatment the boards still showed presence of small amounts of flux and of white powder.

Example 2 The procedure of Example 1 was repeated except that the cleaning composition was a mixture of 1,1 ,2-trichloro-1 ,2,2-trifluoroethane (93.1%), methyl alcohol (6.4%), 2,2,2tri(hydroxymethyl)-propane and nitromethane (0.05%).

The treated boards were found to be perfectly clean and in particular were free from flux. Comparison By way of comparison the procedure of Example 2 was repeated but with merely the azeotropic mixture of 1,1,2-trichloro- 1,2,2trifluoroethane and methyl alcohol. After treatment the boards showed the presence of small amounts of flux and of a white powder.

Example 3 The procedure of example 2 was repeated except that the cleaning composition was a mixture of 1,1 2-trichloro- 1 ,2,2-trifluoroethane (93.1%), methyl alcohol (6.4%) and 1,1,1-tri (hydroxymethyl)-nitromethane NO2C(CH20H)3(O.5%).

The treated boards were found to be clean and were free from flux.

Claims

1. A cleaning composition comprising the approximate azetropic mixture of 1,1,2-trichloro 1 ,2,2,-trifluoroethane and a monohydric lower aliphatic alcohol characterised in that it contains as additive a polyol of formula C(W) (X) (Y) (Z) wherein (W) and (X) which may be the same or different are each a hydroxyalkyl group or hydroxyalkoxy group each having 1 to 8 carbon atoms on a hydroxyalkylene group having 2 to 8 carbon atoms and (Y) and (Z) which may be the same or different are each a hydroxyalkyl group having 1 to 8 carbon atoms, a hydroxyalkylene group having 2 to 8 carbon atoms, hydrogen, an alkyl group having 1 to 8 carbon atoms, an alkylene group having 2 to 8 carbon atoms or a nitro-group.

2. A composition as claimed in claim 1 in which the polyols are triols and in which one of the groups (Y) and (Z) is an alkyl group.

3. A composition as claimed in claim 1 or claim 2 in which the alkyl chain of the hydroxyalkyl or hydroxalkoxy group and the alkylene chain of the hydroxyalkylene group contain 1 to 6 carbon atoms and 2 to 6 carbon atoms, respectively.

4. A composition as claimed in any of the proceding claims in which a hydroxy group is attached to a terminal carbon atom of a hydroxyalkyl or hydroxyalkylene group.

5. A composition as claimed in any of the preceding claims in which (W) is a hydroxyalkyl group and one or more of the groups (X), (Y), and (Z) is the same hydroxyalkyl group.

6. A composition as claimed in claim 5 in which the hydroxyalkyl group is a hydroxymethyl group.

7. A composition as claimed in claim 6 in which the polyol is 1,1,1 -tri(hydroxymethyl)- ethane.

8. A composition as claimed in claim 6 in which the polyol is 1,1,1 ,-tri(hydroxymethyl) propane.

9. A composition as claimed in any of the preceding claims in which the polyols are diols wherein (W) is a hydroxyalkyl group, (X) is a hydroxyalkoxy group and (Y) and (Z) are each hydrogen.

10. A composition as claimed in clain 9 in which the diol is diethylene glycol.

11. A composition as claimed in claim 9 in which the diol is dipropylene glycol.

12. A composition as claimed in any one of the preceding claims in which the polyol boils at temperatures above 1 0O0C.

13. A composition as claimed in any one of the preceding claims in which the polyol is present in proportions of 0.01% to 1% by weight with reference to the total weight of the cleaning composition.

14. A composition as claimed in any of the preceding claims in which the monohydric lower aliphatic alcohol contains 1 to 3 carbon atoms.

1 5. A process for making cleaning compositions characterised by incorporating into the approximate azeotropic mixture of 1,1,2 trichloro-1 ,2,2,-trifluoroethane and a monohydric lower aliphatic alcohol a polyol as described in any of the preceding claims 1 to 14.

1 6. A method of cleaning contaminated articles by bringing them into contact with a cleaning composition as described in any of the preceding claims 1 to 12.