GB2071687A - Compositions containing 1,1,1- trichloroethane - Google Patents

Abstract

A composition useful for drying articles and if desired cleaning them comprising 1,1,1-trichloroethane containing an alkali metal or alkaline earth metal petroleum sulphonate and a sorbitan ester. Water may be emulsified in the composition.

Description

SPECIFICATION Drying and cleaning composition This invention relates to a drying and cleaning composition based on 1 , 1 , 1 -trichloroethane.

1,1,1 -trichloroethane is used on a large scale in industry as a solvent for cleaning articles, for example for removing oily, greasy and resinous contaminants from metal and other articles. It has a low boiling point and low toxicity and its use for the drying of wetted articles would be desirable.

However 1,1,1 -trichloroethane cannot be used effectively either at ambient temperature or at the boil for the removal of water froin wet articles.

Also, 1,1 1-trichloroethane does not effectively remove water-soluble contaminants from articles.

We have now found that the properties of 1,1,1-trichloroethane can be modified by the incorporation of certain additives to provide a composition in which water can be emulsified such that the composition is useful for drying wet articles. The compositions, including those containing water emulsified therein are useful for cleaning articles.

According to the present invention there is provided a composition comprising 1,1,1trichloroethane containing an alkali or alkaline earth metal salt of a petroleum sulphonic acid and a sorbitan ester.

The alkali metal or alkaline earth metal salts of petroleum sulphonic acids are well known and are generally referred to as alkali metal or alkaline earth metal petroleum sulphonates, which term will be used hereinafter. Preferably there is employed an alkali metal petroleum sulphonate, especially a sodium petroleum sulphonate. The petroleum sulphonates may be made synthetically, for example by sulphonation of petroleum fractions. Typical petroleum sulphonates, which are useful in the present compositions, are those of molecular weight from 300 to 700.

The ester grouping of the sorbitan ester, which may be a mono or poly-esters (e.g. a tri-ester) preferably contains from 10 to 25 carbon atoms and may be ethylenically saturated or unsaturated. Sorbitan monostearate is a particularly preferred ester for use in the present compositions.

The ratio by weight of the petroleum sulphonate salt to the sorbitan ester may vary widely but is usually in the range 1:3 to 5:1 i.e.

from 0.3 to 5 parts by weight of the petroleum sulphonate salt per 1 part by weight of the sorbitan ester. Preferably there is employed a ratio of the petroleum sulphonate salt to the sorbitan ester of at least 1:1 and especially in the range of from 1.5:1 to 3.5:1.

Only small amounts of the petroleum sulphonate and the sorbitan ester need be employed in the compositions. Usually the additives are present in amounts such that the combined weight of the additives is from 0.5% to 5% by weight of the composition, preferably from 1% to 3% by weight.

Water and other aqueous media are effectively emulsified in the compositions and the emulsion is stable both at ambient temperatures and at the boil. Wet objects can be passed through the composition, especially the boiling composition, to leave them essentially completely dry.

The well known tendency of 1,1,1trichloroethane to decompose by hydrolysis in the presence of water is reduced by the presence of the petroleum sulphonate salt and the sorbitan ester.

The compositions of the invention are useful as drying and/or cleaning compositions for articles, depending to some extent upon the amount of water present in the composition. Large amounts of water may be emulsified, for example 40% by weight or even higher based on the weight of the emulsion, and provided the emulsion is capable of emulsifying further amounts of water it can be used to dry wet articles. Thus the compositions may contain from 0% by weight of water up to 40% by weight or even higher of water.

In a composition intended primarily for drying articles, we prefer to maintain the amount of water emulsified therein at a low level, for example usually below 4% by weight of the composition. For drying uses, we especially prefer to start with compositions essentially free from water and to control the amount of water emulsified in the composition in use at below about 4% by weight of the composition. Removal of water from the composition is usually by azeotropic distillation, for example by using the composition at the boil.

In a composition intended primarily for cleaning articles, especially for removing water-soluble contaminants and tenaciously adhering contaminants such as jewellers' rouge, we prefer compositions containing a higher proportion of emulsified water, for example greater than 7% by weight of water based on the composition and up to 40% by weight or even more of water.

Compositions containing large amounts of water are still useful for removing oily and greasy contaminants from articles.

In addition to the petroleum sulphonate salt and the sorbitan ester, the compositions may contain one or more conventional stabilisers, for example to stabilise 1,1,1 -trichloroethane against decomposition induced by the presence of metals, especially zinc and aluminium, or by heat and/or light. For example it may be desirable to stabilise the solvent to inhibit attack on the solvent by the metal articles being cleaned or by the metal of which the treatment tanks are made. Examples of conventional stabilising additives which may usefully be included in the compositions are nitroalkanes, epoxides, amines, alkanolamines, cyclic ethers, ketones and alcohols. In addition to these conventional stabilisers other compounds known primarily as brightening agents for copper and brass may be added, if desired.

Articles to be dried and/or cleaned are simply immersed in the solvent compositions for a suitable period of time, for example from 30 to 60 seconds. Preferably the articles are immersed in the boiling composition. The articles are removed and rinsed, conveniently in 1,1,1 -trichloroethane or the vapour thereof. In using boiling compositions, the azeotrope of water and 1,1,1 trichloroethane which is distilled off is condensed and the phases separated; the water phase is usually passed to drain and the solvent phase is returned to the rinsing compartment. If used for removing tenaciously adherent contaminants or water soluble contaminants, the cleaning composition may be used at the boil or at ambient temperature with mechanical or ultrasonic agitation.

If the composition is employed at ambient temperature to clean articles, a small amount of water may be carried over into the rinsing compartment. The solvent in the latter compartment is used at the boil so that any water carried over into this compartment is removed by azeotropic distillation. If the cleaning composition is used at the boil, the or part of the water recovered by azeotropic distillation may be returned to the cleaning compartment.

All kinds of articles including glass, metal, and plastic articles not damaged by 1,1,1trichloroethane may be dried and if desired cleaned using the compositions of the invention.

Absorbent articles may be dried and/or cleaned.

The present invention includes within its scope a method of drying articles and a method of cleaning articles using the compositions hereinbefore described.

The following examples illustrate the invention EXAMPLE 1 A composition suitable for drying wet articles was made up by incorporating a sodium petroleum sulphonate (1.7% by weight of the composition) and sorbitan monostearate (0.8% by weight of the composition) into 1,1,1trichloroethane containing conventional stabilisers. The sodium petroleum sulphonate is available under the Trade Name 'Petromor' L60 from Burmah Castrol Limited. The sorbitan monostearate is available under the Trade Mark 'Span' 60 from Honeywill Atlas.

The drying composition was used to dry wet gauzes. A conventional stainless steel tank was employed having a compartment for the drying composition, a rinsing compartment, a condenser consisting of stainless steel pipework running round the upper portion of the tank and a separator for condensed solvent and water. The drying and rinsing compartments were both 25 cm long by 15 cm wide. The drying composition was placed in the drying compartment to a depth of approximately 25 cm.

1,1,1 -trichloroethane containing conventional stabilisers was placed in the rinsing compartment to a depth of approximately 25 cm. The drying composition and the solvent in the rinse compartment were heated to boiling, and the vapours emmitted were condensed and separated into two phases. The solvent phase was passed to the rinsing compartment.

Water was passed intermittently (25 mls at about 5 minute intervals) into the drying compartment to determine whether the emulsion thereby produced was stable and to determine whether wet articles were dried by the composition in the presence of water. The process was operated over a period of 689 hours. The volume of water added over a 24 hour period was approximately 7 litres and approximately 7 litres water were removed over the same period from the separator.

Pieces of wet gauze were immersed from time to time firstly in the drying composition and then in the rinsing compartment, each for a period of 30 seconds. The gauzes were found to be essentially dry in all cases, the emulsion was stable and the solvent composition did not become discoloured.

COMPARISON By way of comparison the above drying procedure was repeated except that the petroleum sulphonate salt and the sorbitan stearate were not added to the 1,1,1 -trichloroethane. The pieces of wet gauze were not dried satisfactorily. After 200 hours of the operation the acid acceptance value of the solvent (that is the capability of the solvent to absorb acid) was only 75% of the acid acceptance value of the drying composition containing the petroleum sulphonate salt and the sorbitan ester after the same period of use.

EXAMPLE 2 A cleaning composition comprising 60% by weight of the drying composition described in Example 1 and 40% by weight of water, was placed to a depth of about 25 cms in the cleaning compartment of a conventional stainless steel tank as described in Example 1. 1,1,1trichloroethane containing conventional stabilisers was placed in the rinsing compartment to a depth of about 25 cms. The contents of both compartments were heated to boiling. The vapour emitted from the compartments were condensed and the phases were separated. The solvent was passed to the rinsing compartment.

The water was passed to a tank from which it displaced an equal volume of fresh water which in turn was passed to the cleaning compartment.

Spoonblanks contaminated with jewellers rouge were dipped firstly in the cleaning compartment and then in the rinsing compartment, each for a period of 30 seconds.

The spoonblanks were cleaned satisfactorily.

Claims (10)

1. A composition comprising 1,1,1trichloroethane containing an alkali metal or alkaline earth metal salt of a petroleum sulphonic acid and a sorbitan ester.

2. A composition as claimed in claim 1 in which the ratio by weight of the petroleum sulphonate salt to the sorbitan ester is in the range of from 1:3 to 5:1.

3. A composition as claimed in claim 1 or claim 2 in which the combined weight of the petroleum sulphonate salt and the sorbitan ester is from 0.5% to 5% by weight of the compositions.

4. A composition as claimed in any one of claims 1 to 3 which is an emulsion of water in 1,1,1 -trichloroethane.

5. A composition as claimed in claim 4 in which the amount of water is up to 40% by weight of the composition.

6. A drying composition as claimed in claim 5 in which the amount of water is less than 4% by weight of the composition.

7. A cleaning composition as claimed in claim 5 in which the amount of water is from 7% to 40% by weight of the composition.

8. A method of drying articles and if desired cleaning them which comprises immersing the articles in a composition as claimed in any one of claims 1 to 7.

9. A method of cleaning articles and if desired drying them which comprises immersing the articles in a composition as claimed in any one of claims 1 to 7.

10. A method as claimed in claim 8 or claim 9 in which the articles are immersed in the boiling composition.

1 A method as claimed in claim 8, 9, or 10 in which the articles are rinsed subsequently in boiling 1,1,1 -trichloioethane or the vapour thereof.