GB2214923A - Soap compositions - Google Patents

Abstract

Sulphite or perborate bleach is incorporated into soap bars formed from a composition which is at least 30% by weight soap. The bleach is stabilized by the presence of a stabilizing agent which is preferable magnesium silicate. The composition may include a phosphate and free falty acids.

Description

SOAP COMPOSITIONS This invention relates to soap compositions where the soap is in the form of substantially solid shaped articles, normally bars.

It is conventional to include bleaches in European heavy duty powdered detergent compositions for normal laundering.

In such products the reactive bleach, which is dry blended into the formulation, is in separate particles from the other components of the composition. Such separation from other components of the composition helps to protect the bleach from decomposition through reaction with other components. It is not normal to incorporate bleaches into soap bars. It would be expected that the intimate contact between the bleach and soap (which normally contains unsaturation) would lead to decomposition of the bleach.

Nevertheless, the present applicants consider that a soap bar containing bleach would be desirable, especially in a soap bar of the type used for hand-laundering of clothes in countries where hand-laundering is prevalent.

We have now found that, contrary to expectation, some commercial bleaching agents can be incorporated into a soap composition under certain conditions, without the expedient of coating the bleach particles with an inert protective coating - which is one way in which stability of the bleach might be achieved.

Broadly, the present invention resides in the incorporation of bleach in a composition to be used for the formation of substantially solid, shaped soap bars.

The applicants have found that commercial grade sodium orthophosphate, which is a conventional material to incorporate as a builder, leads to bleach instability. In this invention, either the amount of sodium orthophosphate is held to below 5*, better below 3%, by weight of the composition or a stabilizer for the bleach is included in the composition. The preferred stabilizer is magnesium silicate which may be accompanied by an organic complexing agent, e.g. in an amount up to 15* of the magnesium silicate. Of course, orthophosphate may be entirely absent, and stabilizer may be used even when orthophosphate is at a level below 3% by weight of the composition.

Other salts such as carbonate are preferably kept to a low level so that the total level of salts is below 5%, better below 3%, by weight of the composition, or if any salts are present to above this level it is preferable to include bleach stabilizer.

Inert fillers such as calcite or kaolin may also be included in the soap composition in amounts ranging up to 50% by weight of the total formulation.

It will generally be the case that soap is the only detergent active present, or is the preponderant active with only minor amounts of non-soap detergent. Soap normally contains moisture, and so the quantity of soap (on a dry weight basis) and moisture together will generally be over 50% by weight of the composition. The dry weight of soap will generally be at least 30% by weight of the composition.

Generally, the soap used will be one or a mixture of alkali metal salts of C8 to C22 saturated or unsaturated fatty acids. Sodium salts will normally be based on mixed acids such as an 80/20 tallow/coconut soap which includes unsaturation. A soap of this type may well have trace amounts of added metal sequestrants such as orthophosphoric acid, ethylene diamine tetraacetic acid (EDTA) and ethane hydroxy diphosphonic acid (EHDP) added during manufacture to prevent rancidity.

In preferred forms, soap will be present in the compositions used for making said described soap bars in amounts such that the dry weight of soap is 35-75% by weight of the whole composition.

The moisture content of these preferred embodiments of the invention will generally range from a minimum of 3 wt% up to a level of 35 wt%. Preferably, the soap bars are manufactured with not more than 25 wt% moisture.

It is preferred that the bleach employed in the compositions of this invention is either perborate, particularly perborate monohydrate, or sulphite. The amount of bleach may generally be 2 to 50 wt% of the composition, preferably 5 to 15 wt%.

The amount of perborate is conveniently expressed in terms of the amount of available oxygen i.e. the amount of oxygen which can theoretically be delivered upon application of the soap bar to laundry. The amount of perborate monohydrate, when used in the compositions of the present invention, may be equivalent to an amount of available oxygen corresponding to 0.32 to 8.0 wt% (based on the whole composition).

We have found that when the bleach is sulphite it is advantageous to include fatty acid. It is desirable to hold the level of fatty acid below 10% by weight of the composition, or else to include a bleach stabilizer and a bar structurant. Again the preferred stabilizer is magnesium silicate.

As mentioned, when a bleach stabilizer is included, the stabilizing agent is preferably magnesium silicate.

Magnesium silicate may be provided in the composition by the incorporation of 'Magilex 808' made by Rhone-Poulenc and which comprises magnesium silicate doped with 8% of an organic complexing agent. The 'Magilex 808' is preferably provided in these embodiments of the invention at levels of between 0.5 and 5 wt (based on the whole composition).

Embodiments of the present invention will now be described by way of example only with reference to the following Example.

Example 1 Shaped soap bars were made according to the compositions set out in the following Table 1. All constituents are given in weight % amounts with respect to the final bar compositions.

TABLE 1 % W/W Ingredients A B C (comparative) Soap 80/20 Tallow/Coconut 65.5 40 38 (dry weight basis) Perborate monohydrate 15.7 16 16 Water 18.8 30 30 Sucrose - 4 4 Orthophosphate - 10 10 'Magilex 808' - - 2 Each composition was prepared by mixing the soap and nonbleach ingredients at or above 50 C in a Z-blade mixer. The dough produced was then cooled to below 40"C and the perborate monohydrate or sulphite added. After mixing in for about 5 minutes the bleach-containing dough was made into bars by compression or by passing through an extruder.

The soap used was a commercial 80/20 tallow/coconut soap containing (based on the soap) 0.024 wt% ethylene diamine tetra-acetic acid (EDTA), 0.018 wt% ethane hydroxy diphosphonic acid (EHDP) and 0.012 wt% orthophosphoric acid.

Sample bars were stored, at ambient and elevated temperatures, and wrapped in glassine paper to prevent moisture loss or gain. Some bars were over-wrapped with sealed plastic bags. At intervals, the amount of bleach remaining was determined. The amounts of perborate monohydrate remaining are shown graphically in the accompanying Figures 1 and 2.

As can be seen from these Figures, the composition of the comparative Example B, whose results appear in Figure 2a, displayed much lower bleach stability than the phosphatefree Example A, although improved stability can be achieved by including Magilex 808 (Example C).

Example 2 A generally similar procedure to Example 1 was carried out, using sodium sulphite as the bleach.

The soap employed was again an 80/20 tallow/coconut soap containing, based on the soap, 0.024 wt% EDTA, 0.018 wt% EHDP, and 0.012 wt orthophosphoric acid.

Compositions are as set out in Table 2 below.

TABLE 2 % W/W Ingredients D E F G (comparative) Soap 80/20 Tallow/Coconut 59.5 45.0 53.3 56.5 (dry weight basis) Sodium sulphite 15 15 15 15 Water 25.5 30 25.5 20 Orthophosphate - 10 Free fatty acid - - 6.2 6.5 (80/20 Tallow/Coconut) Magilex 808 - - - 2.0 Sample bars were stored, at ambient and elevated temperatures, wrapped in glassine paper and in some cases over-wrapped in sealed plastic bags. At intervals the amounts of remaining sulphite bleach were determined.

Results are shown in the accompanying Figures 3-6.

As can be seen, compositions E and F, respectively containing orthophosphate and free fatty acid, displayed lower bleach stability than composition D or the Magilexcontaining composition G.

Claims (11)

1. A substantially solid soap bar formed from a composition comprising at least 30% by weight soap, with said soap being present in an amount greater than the amount of non-soap detergent (if any), wherein the composition also contains bleach, and either the amount of inorganic phosphate (if any) is below 5% by weight of the composition, or the composition contains a stabilizing agent for said bleach, in addition to inorganic phosphate.

2. A soap bar according to claim 1 or claim 2 wherein the stabilizing agent is magnesium silicate.

3. A soap bar according to claim 2 wherein the amount of magnesium silicate included in the composition is at least 0.5% by weight of the composition.

4. A soap bar according to any one of the preceding claims wherein the total amount of inorganic salts (if any) is below 5% by weight of the composition.

5. A soap bar according to any one of the preceding claims wherein the soap comprises alkali metal salts of C8 to 2 2 fatty acids, including unsaturated fatty acids.

6. A soap bar according to claim 4 wherein the soap is an 80/20 tallow/coconut soap.

7. A soap bar according to any one of the preceding claims wherein the bleach is perborate.

8. A soap bar according to any one of claims 1 to 6 wherein the bleach is sulphite.

9. A soap bar according to claim 8 wherein the amount of free fatty acid (if any) is less than 10% by weight of the composition notably 0.5 to 6%.

10. A substantially solid, shaped soap bar according to any one of the preceding claims wherein the composition contains: a) soap 35-70% b) water 3-35% c) bleach 2-50t d) phosphate not over 5% e) free fatty acid 0-10t (where the percentages are by weight of the whole composition).

11. A substantially solid, shaped soap bar substantially as any described herein.