GB2034741A - Soap powder - Google Patents

Abstract

A soap powder in which the soap blend contains a high proportion of water-soluble salts of unsaturated fatty acids. The proportions of the fatty acids in the mixture from which the soap is made are: 5-60% by weight of one or more fatty acids having 14 fewer carbon atoms, 5-32% by weight of one or more saturated fatty acids having more than 14 carbon atoms, 35-90% by weight of one or more unsaturated fatty acids having 14 or more carbon atoms. The resulting soap has improved water-solubility whilst its detergency is maintained.

Description

SPECIFICATION Soap powder compositions This invention relates to a soap powder.

In the United Kingdom fabric washing powder market two popular products are formulated to contain major quantities of soap. Ths success of these products is largely dependent on the good detergency of soap and on the fact that washing powders based on it tend to leave clothing feeling softer than that which has been washed in powders based on synthetic anionic and/or nonionic detergents.

There is, however, a technical problem with soap, namely that it is not easy to obtain satisfactory dissolution, particularly at low temperatures. There are two aspects of this problem; first there is the problem of wetting characteristics, some characteristics leading to formation of dots or gels. Secondly, even when the wetting characteristics of the soap powder are satisfactory, there remains the problem of the inherent poor solubility of soap, particularly at low temperatures.

This invention is concerned with the inherent poor solubility of soap.

We have discovered that there are significant differences between the water-solubilities and detergent efficiences of soaps of different chain lengths and degrees of unsaturation within the normal range, particularly the range C,2 to C22, which is used in the manufacture of soap powder, and that by careful selection of composition solubility can be improved while keeping detergency at a high level.

Accordingly, the present invention provides a soap powder comprising from 1 5 to 60% by weight of a mixture of water-soluble salts, preferably the sodium salts of Cl2-C22 fatty acids wherein the mixture comprises From 5 to 60% of one or more fatty acids having 14 or fewer carbon atoms; from 5 to 32% of one or more saturated fatty acids having more than 14 carbon atoms; from 35 to 90% of one or more unsaturated fatty acids having 14 or more carbon atoms.

For brevity, the fatty acids identified above are henceforth referred to as follows: Group A ACx4 saturated or unsaturated Group B > Ca4 saturated Group C > Ca4 unsaturated and the relative amounts of these three groups present in any composition can be represented graphically as shown in the accompanying drawings. Only two co-ordinates are necessary since it is assumed that the balance of the composition consists entirely of Group C fatty acids.

Referring to Figure 1, the composition broadly defined above is represented by the rectangle ACDF.

It is preferred that the selected mixture of water-soluble salts of C,2~22 fatty acids has the composition represented by the area ABDEF of Figure 1, and particularly that it has a composition represented by the area ABEF, since compositions lying within these areas exhibit a more pronounced superiority over the prior art compositions represented by the area UVWZ and particularly by point X, than do compositions outside these areas.

The manner in which the desired compositions are formulated will be determined mainly by cost considerations within certain guidelines but these compositions cannot be obtained by using only the ciassic soap-making materials coconut oil, palm kernel oil or tallow. Coconut oil and palm kernel oil are rich in the Group A fatty acids and tallow class fats are rich in the saturated and unsaturated fatty acids of Groups B and C. Groundnut oil is the preferred source to enhance Group C fatty acid content since this is high in oleic acid content and relatively low in linoleic and linolenic acids. There are a number of other oils relatively rich in Group C acids. These include, but are not confined to, soyabean oil, sunflower oil, rapeseed oil, and cottonseed oil.Because these oils are rather prone to oxidation (due to their high linoleic/linolenic contents) they are best used together with a suitable antioxidant.

For best results we specify oils which are free from linolenic acid and prefer to use oils which provide a fatty acid composition in the final soap powder which contains a total of no more than 50% by weight of linoleic and linolenic acids. When the total content of these acids is frpm 20 to 50% by weight we recommend the use of a suitable antioxidant. We have found ethanel -hydroxy-1, 1 -diphosphonic acid or ethylene diamine tetraacetic acid, or a mixture thereof, to be suitable antioxidants. Besides the naturally-occuring oils, certain commercially available technical grade fatty acids can be used also.

In order to obtain good solubility from the soap powders of this invention it is preferable to choose a mixture of fatty acids whose water-soluble sodium salts have a Krafft temperature of from 30-350C.

preferably no higher than 250C.

Krafft temperature is defined by Lloyd I Osipow in 'Surface Chemistry, Theory and Industrial Application', published by Rheinhold of New York, 1962, and this definition is adopted for the purposes of this specification. To summarise the definition, the Krafft temperature can be regarded as the temperature above which there is a rapid increase in solubility of the surfactant in question due to formation of micelles.

The soap powder of the invention may, and usually will, contain a detergency builder compound.

Any detergency builder may be used, either a phosphate-based builder such as sodium tripolyphosphate, sodium pyrophosphate or sodium orthophosphate, or a mixture thereof, or any one of the compounds which has been suggested recently as a result of pressure from those wishing to reduce phosphate contents of effluents. Typical of these are sodium citrate, alumino-silicates, both crystalline and amorphous, and a host of organic chelating compounds, prominent amongst which are nitrilotriacetic acid, which has been used commercially in some countries, alkenyl succinate salts and salts of carboxymethyloxysuccinic acid, and salts of dipicolinic acid. These detergency builder compounds can be used in any desired combination so that the desired calcium/magnesium building capacity is achieved at the level of phosphorus, if any, which is permitted or required.

Bearing in mind that soap formulations are to a large extent self-building, the amount of detergency builder compound required will normally be between 5 and 25% by weight of the whole powder formulation when the amount of soap is between 25 and 60% by weight, as is preferred.

The detergency builder which is preferred, for reasons of cost-effectiveness, is sodium tripolyphosphate. When this substance is used, the weight ratio, water-soluble salt of C,2-C22 fatty acids:sodium tripolyphosphate may be from 10:1 to 1:2, preferably 9:1 to 3:1.

The soap powders of the invention may contain other materials in conventional amounts. For example, they may contain a bleaching material, either an oxygen bleach such as sodium perborate or sodium percarbonate, or a chlorine bleach such as sodium di- or tri-chloroisocyanurate, or mixtures thereof. These materials may be present in amounts of from 10 to 30% by weight of the powder, preferably 15 to 25%, when the bleaching material is sodium perborate or sodium percarbonate and from 5 to 20% by weight when it is a chlorine bleach such as sodium dichloroisocyanurate.

Antiredeposition agents, such as sodium carboxymethyl cellulose, fillers such as sodium sulphate or sodium carboxymethyl cellulose, fillers such as sodium sulphate or sodium carbonate, corrosion inhibitors such as sodium silicate, lime soap dispersants such as nonionic surfactants, alkanolamides, alkali metal ether sulphates and betaines, optical brightening agents, coloured speckles and perfumes, may also be present in amounts varying from 0.1 to 15%, preferably 0.1 to 5% by weight Moisture may be present in an amount of up to 15%.

The soap powder may be made by any of the conventional methods known to those skilled in the art, which include slurry-making, spray-drying, dry-dosing and spraying of fatty acids directly onto solid components of the powders.

The invention will be further illustrated by reference to the following Examples.

EXAMPLE 1 Five soap powders containing 45% by weight of soap, 10% by weight of sodium tripolyphosphate, 9% by weight of sodium silicate (Na2O:SiO2, 2:1), 25% by weight of sodium perborate, were prepared by conventional spray-cooling and dry-dosing techniques.

The fatty acid compositions of the soap were as defined by the points 1 to 4, which have Krafft temperatures below 250C, and X (prior art composition) of Figure 1 of the accompanying drawings.

In a first experiment, the solubility of each of the powders was determined. The results, expressed as a percentage of the powder remaining undissolved, are shown in Table 1.

TABLE 1

Solubility at 20'C Formulation (% insolubles) X 20 1 7 2 6 3 9 4 7 In a second experiment the detergencies of the soap powders were determined.The procedure used was to measure the difference in refiectance between washed and unwashed test cloths, and to express the results as a percentage, percentage detergency being defined as: % detergency =tOOx Reflectance of Washed Cloth Reflectance of Unwashed Cloth Reflectance of Unsoiled Cloth Reflectance of Unwashed Cloth Washed conditions, using Terg-O-Tometers (Trade Mark) were at a temperature of 600C and water hardness of 260 (French). the test cloths were WFK cloths soiled with a mixed inorganic/synthetic sebum soil. The results are shown in Table 2.

TABLE 2

Detergencies % Formulation 5 g/l 8 g/l | 8 g/l X 35 T 40 42 1 42 44 46 2 46 48 48 3 43 45 47 4 40 43 47 EXAMPLE 2 Washing solutions containing (i) 6 x 10-3 and (ii) 3 x 10-3 moles soap/litre in combination with 1.4 x 10-3 moles/litre of sodium tripolyphosphate and 1.8 x 10-3 moles/litre sodium silicate (Na2O:SiO2 2:1) were prepared. These solutions were then used to wash WFK test cloth soiled with a mixed inorganic/synthetic sebum soil in Terg-O-Tometers (Registered Trade Mark). The washing conditions used were: Wash temperature 600C Water hardness 260 French Five experiments were performed using pairs of solutions containing Group A fatty acid soap/Group C fatty acid soap ratios of (a) 100/0, (b) 90/10, (c) 80/20, (d) 50/50 and (e) 0/100. In a sixth control experiment, a washing solution containing 1.4 x 10-3 moles/litre of sodium tripolyphosphate and 1.8 x 10-3 moles/litre of sodium silicate without any soaps was used to wash WFK cloths under conditions similar to those described already. The difference in reflectance between washed and unwashed cloths was measured. The results are shown graphically in Figure 2 of the accompanying drawings and show the beneficial effect of detergency of using soap formulations containing 35% or more Group C soap.

Claims (6)

1. A soap powder comprising from 1 5 to 60% by weight of a mixture of water-soluble salts of Cur2~22 fatty acids wherein the mixture comprises (i) from 5 to 60% by weight of one or more fatty acids having 14 or fewer carbon atoms; (ii) from 5 to 32% by weight of one or more saturated fatty acids having more than 14 carbon atoms; (iii) from 35 to 90% by weight of one or more unsaturated fatty acids having 14 or more carbon atoms.

2. A soap powder according to claim 1, wherein the composition of the mixture of fatty acids is that represented by the area ABDEF of Figure 1 of the accompanying drawings.

3. A soap powder according to claim 2, wherein the composition of the mixture of fatty acids is that represented by the area ABEF of Figure 1 of the accompanying drawings.

4. A soap powder according to any of the preceding claims, additionally comprising from 525% of a detergency builder.

5. A soap powder according to claim 4, wherein the detergency builder comprises sodium tripolyphosphate and the weight ratio water-soluble salt of C12 22 fatty acid: sodium tripolyphosphate is from 10:1 to 1:2.

6. A soap powder comprising 35% or more of an unsaturated fatty acid having 14 or more carbon atoms, substantially as hereinbefore described with reference to and as illustrated in any one of the compositions in Examples 1 and 2.