GB2036065A

GB2036065A - Solvent Cleaning Composition

Info

Publication number: GB2036065A
Application number: GB7941090A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1978-12-08
Filing date: 1979-11-28
Publication date: 1980-06-25
Also published as: GB2036065B

Abstract

A cleaning composition for the removal of fluxes comprises the azeotropic mixture of 1,1 ,2-trichloro- 1,2,2-trifluoroethane and a lower aliphatic alcohol together with a substituted amine having at least one hydroxyalkyl, hydroxyalkylene or hydroxyalkoxyalkyl substituent attached to the amine nitrogen atom.

Description

SPECIFICATION Cleaning Composition This invention relates to a cleaning composition comprising 1,1 ,2-trichloro-1 2,2-tri- fluoroethane 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 be not 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 alcohols but which also contains a special additive whereby improved cleaning effects can be obtained.

According to the present invention we provide a cleaning composition characterised in that it comprises the approximate azeotropic mixture of 1,1 ,2-trichloro-1 2,2-trifluoroethane and a lower aliphatic alcohol and containing as additive a substituted aliphatic amine having at least one hydroxyalkyl or hydroxyalkylene or hydroxyalkoxy alkyl substituent having up to 8 carbon atoms attached to the amine nitrogen atom.

Preferably the substituted aliphatic amine is of the formula NXYZ wherein X is selected from a hydroxyalkyl group of hydroxyalkoxy group each having 1 to 8 carbon atoms or a hydroxyalkylene group having 2 to 8 carbon atoms and Y and Z 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 or an alkylene group having 2 to 8 carbon atoms. When X, Y and Z is a hydroxyalkyl group or hydroxyalkylene group X, Y and Z may be the same or different.

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

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

Suitably X is a hydroxyalkyl group for example the 2-hydroxyethyl group. When one or both Y and Z is/are hydroxyalkyl groups they are usually the same as X, suitably the 2-hydroxyethyl group.

Typical examples of the substituted amines useful in the present cleaning composition include diisopropanol amine, triethanolamine and triisopropanol amine. Another suitable additive is (2-dimethyla mino)-ethyl 2-hydroxyethyl ether, (CH3)2NCH2CH2OCH2CH2OH, that is, a substituted amine wherein the X substituent is a hydroxyalkoxy substituent.

The additive in the present cleaning composition preferably boils at temperatures above 1 000C and is non-volatile under the conditions of use of the composition.

The phrase approximate azeotropic mixture means these mixtures which boil within + 20C of the azeotropic mixture. Preferably the mixture boils within + 1 OC of the azeotropic mixture.

More preferably the azeotropic mixture itself is employed.

If desired mixtures of aliphatic alcohols may be used. Preferably an 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 as impurity.

Quite small amounts of the 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 additive in making up the cleaning composition, for example 0.01% to 1% by weight. Greater proportion by weight of the additive, for example up to 3% 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 described hereinbefore are efficient cleaning agents. They are, however, capable of improvement in respect of stability when the compositions are used in contact with metals, for example a metal such as copper or alloys thereof containing a high proportion of copper. This may happen for example when the cleaning composition contacts pipe work made of copper and contacts articles to be cleaned which themselves are made of copper or have copper members attached thereto. Under such conditions, slight discolouration of the composition due to presence of copper may occur. This is not desirable in the cleaning procedure.

According to a further feature of the invention there is provided a cleaning composition of improved stability in the presence of metals such as copper, which composition comprises the approximate azeotropic mixture of 1,1 ,2-trichloro1 ,2,2-trifluoroethane and a lower aliphatic alcohol, a substituted aliphatic amine additive as hereinbefore described and a benzotriazole or a benzimidazole.

By the terms "a benzotriazole" or "a benzimidazole" as used throughout this specification there are meant compounds having the generic formulae:

respectively, where R1, R2, R3 and R4 may be hydrogen or an alkyl radical having 1 to 6 carbon atoms. It is preferred to use the non-alkyl substituted materials, that is, benzotriazole and benzimidazole. Of these it is preferred to use benzotriazole.

The amount of benzotriazole or benzimidazole in the cleaning compositions need only be quite small. Usually there is present 0.005% w/w to 1% w/w of a benzotriazole or a benzimidazole based on the cleaning composition. In such proportions the benzotriazole and the benzimidazole is soluble in the approximately azeotropic mixture of the trichlorotrifluoroethane and alcohol.

The compositions may if desired contain small amounts of other adjuvants, for example, a small amount of conventional stabilizers for the mixture of 1,1 ,2-trichloro-1 2,2-trifluoroethane and 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 substituted amine additive and benzotriazole or benzimidazole or other additives if desired. 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 substituted amine additive if desired with benzotriazole or benzimidazole or other additives into the approximate azeotropic mixtures of 1,1,2 trichlorol ,2,2-trifluoroethane and said lower aliphatic alcohols. 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 ,2,2- trifluoroethane (95.0%), ethyl alcohol (4.5%) and 0.5% of triethanolamine.

Into the rinsing compartment an amount of the same cleaning composition also initially containing the triethanolamine (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 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 1/2 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 fiux.

Comparison By way of comparison the above procedure was repeated with the azeotropic mixture of 1,1 ,2-trichloro-1 2,2-trifluoroethane and ethyl alcohol not containing said triethanolamine additive. After treatment the boards still showed presence of small amounts of flux and of a 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%) and triethanolamine (0.5%).

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 with the azeotropic mixture of 1,1,2-trichloro-l ,2,2-trifluoroethane and methyl alcohol not containing triethanolamine. After treatment the boards showed the presence of small amounts of flux and of a white powder.

Example 3 The procedure described in Example 1 was repeated using the cleaning composition therein described except that diisopropanolamine (0.5%) was used instead of triethanolamine.

Example 4 A conventional stainless steel degreasing unit was employed having a cleaning compartment and a rinsing compartment and a condenser consisting of copper pipework running around the upper portions of the walls of the unit. The cleaning and rinsing compartments were both 25 cms long by 15 cms wide, and contained drainage connections fitted to facilitate cleaning out of the plant after use. These connections were fabricated of copper. Into the cleaning compartment was placed to a depth of 10 cm a cleaning composition comprising a mixture of 1,1 ,2-trichloro-1 ,2,2-trifluoroethane (94.5%), ethyl alcohol (4.5%), triethanolamine (0.5%), benzotriazole (0.5%) and nitromethane (0.05%).

Into the rinsing compartment an amount of the same cleaning composition also initially containing 1 , 1 ,2-trichloro-1 ,2,2-trifluoroethane, ethyl alcohol, triethanolamine, benzotriazole and nitromethane 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 cleaning composition from rinsing to cleaning compartment so that triethanolamine and benzotriazole were removed from the rinsing compartment and passed to the cleaning compartment.

Printed circuit boards (size 5 cms by 2.6 cms) having a substrate of epoxy resin glass mat laminate and contaminated with a flux known as 'Zeva' C40 ('Zeva' is a Registered Trade Mark) were dipped for periods of from 1/2 minute to 1 minute firstly in the cleaning compartment and then in the rinsing compartment. Printed boards which were contaminated with a flux known as Fry's R8 were similarly treated.

The degreasing unit was operated for a period of 230 hours. After that time there was still no discolouration of the cleaning composition which might have been expected due to presence of copper and the treated boards were found to be free from flux. The treated boards were found to be perfectly clean.

Claims

1. A cleaning composition characterized in that it comprises the approximate azeotropic mixture of 1,1 ,2-trichloro-1 ,2,2-trifluoroethane and a lower aliphatic alcohol and containing as additive a substituted aliphatic amine having at least one hydroxyalkyl or hydroxyalkylene or hydroxyalkoxy substituent having 1 to 8 carbon atoms attached to the amine nitrogen atom.

2. A composition as claimed in Claim 1 in which the substituted aliphatic amine is of the formula NXYZ wherein X is selected from 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 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 or an alkylene group having 2 to 8 carbon atoms.

3. A composition as claimed in Claim 2 wherein the alkyl chain of the hydroxyalkyl 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 Claim 1 or Claim 2 in which a hydroxyl group is attached to a terminal carbon atom of the alkyl or alkylene chain.

5. A composition as claimed in any of the preceding Claims 2 to 4 in which X is a hydroxyalkyl group.

6. A composition as claimed in Claim 5 in which both Y and Z are hydroxyalkyl groups.

7. A composition as claimed in Claim 6 or Claim 7 in which the hydroxyalkyl group is a 2hydroxyethyl group.

8. A composition as claimed in Claim 7 in which the substituted aliphatic amine is triethanolamine.

9. A composition as claimed in any of the preceding claims in which the substituted aliphatic amine boils at temperatures above 1000C.

10. A composition as claimed in any of the preceding claims in which the additive is present in proportions of 0.01% to 3% by weight with reference to the total cleaning composition.

11. A composition as claimed in any of the preceding claims which also contains a benzotriazole or benzimidazole.

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

13. A process for making cleaning compositions characterised by incorporating into an approximate azeotropic mixture of 1,1,2 trichloro-1 2,2-trifluoroethane and a lower aliphatic alcohol a substituted aliphatic amine as described in any of the preceding Claims 1 to 12.

14. 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.