GB2186883A - Soap bars - Google Patents

Abstract

Hard soap bars with a water content of 10-33% and containing proteases can be made with a firmness and structure and enzyme stability by inclusion therein of a stabilising system containing a boron compound such as borax, a polyol such as propylene glycol, an organic acid or salt thereof such as formate, citrate or a mixture of succinic, adipic and glutaric acid, and an alkali metal salt of an inorganic acid such as sodium sulphate.

Description

SPECIFICATION Soap bars with enzymes The present invention relates to hard soap bars which contain enzymes incorporated therein.

Many decades ago it had already been suggested in the prior art to incorporate enzymes in soap bars, see GB Patent Specification 265,024. According to this reference, both the enzymes and the soap bar should be dehydrated to a water content of 10% or less, in order to avoid stability problems of the enzymes in the soap bars.

The present invention is particularly concerned with soap bars which contain substantial amounts of water, typically 10 to 33% and more preferably 10 to 25% of water, and which also contain enzymes incorporated therein.

At present, enzyme preparations for use in detergent products are generally manufactured in either liquid form, or in the form of highly water-soluble granules. Both forms of enzyme preparations can be used.

Incorporating such enzyme preparations in soap bars, however, leads to insufficient enzyme stability due to the simultaneous presence of significant amounts of water in the bar. To improve the enzyme stability in detergent products, quite a number of enzyme-stabilizing agents have been proposed, but we have found that these cannot be simply used in soap bars because they affect the desired soap structure and firmness.

Hence, it is an object of the present invention to provide a soap bar containing substantial amounts of water, typically 10-33% or more preferably 10-25% water, and with enzymes incorporated therein using either a liquid or a granular enzyme preparation, said bar having a satisfactory structure and firmness, and having satisfactory enzyme stability.

We have now found that the above object can be achieved by inclusion in such an enzymecontaining soap bar of a mixture of a boron compound, a polyol, an organic acid or its alkali metal salt and an alkali metal salt of an inorganic acid, not being a boron compound, as hereinafter more specifically detailed. With this mixture, satisfactory results both as regards enzyme stability as well as regards bar structure and firmness are obtained, in contrast with other enzyme-stabilising or firmness-improving additives, as will be shown hereafter.

The boron compound is boric acid, boric oxide or an alkali metal borate, especially borax. The polyol is an aliphatic polyol with 2-6 carbon atoms and 2-6 hydroxyl groups, especially propylene glycol. The organic acid is an aliphatic mono-, di- or tricarboxylic acid, especially formic acid, succinic acid, adipic acid, glutaric acid or citric acid or commerically sold mixtures of such acids (e.g. Sokalan DCS). Examples of the alkali metal salts of inorganic acids, not being a boron compound, are sodium sulphate, sodium chloride, sodium carbonate, sodium bicarbonate, sodium phosphate.

The boron compound is used in an amount of 0.1 to 10%, preferably 0.5 to 5%, the polyol in an amount of 0.1 to 10%, preferably 0.5 to 5%, the organic acid in an amount of 0.1 to 10%, preferably 0.5 to 5%, and the alkali metal salt of the inorganic acid, not being a boron compound, in an amount of 0.1 to 5%, preferably 0.25 to 2.5%, all percentages being by weight of the soap bar.

It has also been found that the polyol can be partly replaced by a sugar such as sucrose in the soap bar with the retention of good enzyme stability and bar firmness of the bars.

The soap bar itself can be any conventional soap bar, either made from distilled fatty acids or from oils and fats in well-known ways. The soaps can also be superfatted, i:e. contain some free fatty acids. The soap bar may further contain usual ingredients such as fillers, perfumes, antioxidants, optical breaches and so on. Also non-soap detergents may be included. As previously mentioned, the soap bar usually has a water content between 10 and 33%, preferably between 10 and 25%. The total fatty matter content is normally between 55 and 85%; lower fatty matter contents can also be employed provided appropriate inorganic fillers, for example kaolin, clay, are also used to maintain the content of the aqueous phase within the usual amount.

The enzymes that are incorporated in the soap bars are the usual proteolytic enzymes. These enzymes are well known in the detergent art, and typical examples thereof are bacterial proteases such as Alcalase, Maxatase, Esperase, Savinase, Kazusase, which are all commercially available proteases. Other enzymes may be included as well, such as amylases, cellulases and oxidases.

In general, the amount of protease incorporated in the soap bar is such that it corresponds with a proteolytic activity of 0.1 to 100 GU/mg of the soap bar, preferably 0.5 to 20 GU/mg, most preferably 1.0 to 10 GU/mg (GU/mg=glycine unit/mg).

A glycine unit is defined as the enzyme activity which under standard conditions during a 15 minute incubation at 40"C with N-acetyl casein as substrate produces an amount of NH2-groups equivalent to 1,um of glycine.

It has been found that particular benefits are obtained with the invention if the protease is Savinase. Compared with e.g. Alcalase, a soap bar with Savinase gives similar bar ,structure and better enzyme stability, which is unexpected since Alcalase in a soap solution is more stable than Savinase.

The invention will further be illustrated by way of examples.

Example 1 Into a hard sodium soap, made from a mixture of 80% tallow fatty acids and 20% coconut oil fatty acids having a water content of 15 to 26% and a total fatty matter content of 63.6-67.7%, were mixed Savinase 8.0L in an amount equivalent to about 8 GU/mg of the bar, and the stabilizing ingredients before the plodding stage of the soap production line. Different bars were made with varying additives as shown below.

At regular intervals during storage of the bars, the residual enzyme activity was measured (storage conditions of the bars were: wrapped bars stored at room temperature. The results were as follows: Total Residual Fatty enzyme Hardness Moisture Matter activity (yield content (TFM) after stress) (%) (%) 28 days (103.N.M-2) (in %) 1) enzyme-containing soap bar: not no additives 26.3 67.7 0 determined 2) enzyme-containing 5% kaolin+ 1% Sokalan DCS 23.3 65.2 19 210 3) enzyme-containing soap bar with 1% Sokalan DCS (succinic+adipic acid + glutaric acid) and 2% sodium sulphate 24.4 66.9 20 400 4) enzyme-containing soap bar with 1% Sokalan DCS (succinic +adipic acid + glutaric acid) and 2% sodium sulphate +2% borax 24.9 64.7 16 300 5) enzyme-containing soap bar with 1% (succinic + adipic +glutaric acid) and 2% sodium sulphqte +2% borax+2% propylene glycol 24.3 63.6 90 430 Example 2 Hard soap bars were made from: (i) Conventional soap (82% tallow; 18% coconut oil) produced by pan saponification-herei- nafter coded conventional soap.

(ii) Soap produced by chemical splitting followed by a distillation procedure-hereinafter coded DFA soap.

(iii) Soap produced from a mixture of tallow soap 53.3% and rosin (about 26.7%)-hereinafter coded rosin soap, containing 12.5% water.

All soaps were neutralised with 0.15% orthophosphoric acid, mixed with Savinase 8.0L (about 8 GU/mg of the bar) and the stabilizing ingredient before being plodded on a soap production line.

The enzyme-stabilizing and bar-hardening mixture consisted of sodium formate (2%), borax (2%), propylene glycol (2%) and sodium sulphate (1%).

At regular intervals during storage of the bars, the residual enzyme activity was measured (bars were stored wrapped at 30"C). The results were as follows: Composition Moisture content TFM Storage time (days)

( *) (%) 6 14 21 27 41 47/48 95 1) Conventional bar, 15-20% aqueous phase about 70% TFM 17.5 68.7 - 85 - 96 87 - 90 2) DFA bar 15-20% aqueous phase about 70% TFM 18.7 67.5 81 - 84 - - 73 3) Rosin bar 12.5 - - 94 - - - 92 - Example 3 Hard soap bars were produced from conventional soap (82% tallow, 18% coconut oil) produced by pan saponification, by neutralisation with 0.15% orthophosphoric acid, mjxing with Savinase 8.0L (about 8 GU/mg of the bar) and adding the stabilising ingredients before plodding on a soap production line.

Different bars were made with different enzyme-stabilising and bar-hardening additives as shown below. The water content was about 18% and the total fatty matter content 65-69%.

Bars were stored wrapped at 30 C. At regular intervals during storage of the bars the residual enzyme activity was measured.

Composition Storage time (days) 14 27 41 1) Enzyme-containing soap bar with sodium formate (2%), borax (2%) 82 83 79.

propylene glycol (2%), sodium sulphate (1%) (moisture 17.5%, TFM 68.7%) 2) Enzyme-containing soap bar with sodium formate (2%), borax (2%), 89 92 85 propylene glycol (2%), sucrose (5%), sodium sulphate (1%) (moisture 17.4%, TFM 64.1%) 3) Enzyme-containing soap bar with borax (2%), propylene glycol (2%), 87 84 75 sucrose (5%), sodium sulphate (1%) (moisture 18.7%, TFM 64.8%) Example 4 A soap bar as in Example 3 and containing 2% sodium formate, 2% borax, 2% propylene glycol and 1% sodium sulphate (TFM 68%) was tested for hardness and compared with a conventional hard soap bar (TFM 76.4%), using a hardness-measuring method with a penetrometer.After 7 days' storage at 30 C, the bar of the invention showed a hardness index of 981 N.m-2.103, and the control 1151 N.m 2.103.

Example 5 Bars according to Example 3, 15-20% aqueous phase, about 70% TFM, but with different proteases (at about 10 GU/mg of the bar), were stored at room temperature, 30 C and 37 C and the residual enzyme activity was measured after 56/57 days. The following results were obtained: Bar with room temp. 30"C 37"C TFM pH Savinase 72% 90% 96% 67.7 9.8 Alcalase 65% 81% 72% 68.8 9.6 Esperase 67% 83% 83% 70.9 9.6 Comparing these data with enzyme stability test measurements (1 h.; 30"C) of these enzymes in aqueous solutions at pH 9.6 of the same soap gave half-life time as follows:: Savinase Esperase Alcalase 5 g/l dissolved soap no bar containing no 118 min. 113 min. detectable stabilisers. loss 5 g/l dissolved soap no bar plus the equivalent 140 min. 130 min. detectable of 2% sodium formate, 2% loss 2% borax, 2% propylene glycol in the bar.

20 g/l dissolved soap no bar plus the equivalent 59 min. not detectable of 2% sodium formate, determined loss 2% borax, 2% propylene glycol in the bar.

Contrary to expectation based on solution stabilities, the Savinase-containing bar is the most stable one of the three.

Example 6 The stability of Savinase 8.0L (about 8 GU/mg of the bar) was measured in undried soap bars made from 80% tallow fatty acids and 20% coconut oil fatty acids with various stabilising additives. The bars also contained 0.12 w/w % of phosphoric acid.

The following results were obtained:

Storage time (days) at 37 C Additive Moisture TFM content 0 3 4 5 8 13 23 28 36 1. none 63.9 29.7 0 2. phosphoric acid 65.6 27.8 69.7 0 3. phosphoric acid + system 1 61.0 27.8 84.8 0 4. phosphoric acid + system 2 58.0 29.0 97.4 67.4 51.2 44.9 5. phosphoric acid + system 3 54.9 27.4 113.4 87.2 76.0 62.3 51.1 system 1 : 2% sodium citrate, 2% sucrose, 1% sodium sulphate system 2 : 2% sodium citrate, 2% borax, 2% propylene glycol, 1% sodium sulphate system 3 : 2% sodium formate, 2% borax, 2% propylene glycol, 5% sucrose, 1% sodium sulphate

Claims (7)

1. A hard soap bar containing 10-33% by weight of water, and proteolytic enzymes in an amount of 0.1-100 glycine units per milligramme of the bar, and a stabilising system containing a mixture of a boron compound, a polyol, an organic acid or its alkali metal salt, and an alkali metal salt of an inorganic acid which is not a boron compound.

2. A soap bar according to claim 1, wherein the boron compound is borax, the polyol is propylene glycol, the organic acid is a mixture of succinic, adipic and glutaric acid, and the alkali metal salt of an inorganic acid is sodium sulphate.

3. A soap bar according to claim 1, wherein the alkali metal salt of the organic acid is sodium formate or sodium citrate.

4. A soap bar according to claims 1-3, wherein the boron compound is used in an amount of 0.1-10% by weight, the polyol in an amount of 0.1-10% by weight, the organic acid or salt thereof in an amount of 0.1-10% by weight, and the alkali rrietal salt of the inorganic acid in an amount of 0.1-5% by weight of the bar.

5. A soap bar according to claims 1-4, wherein the polyol is partly replaced by a sugar.

6. A soap bar according to claims 1-5, wherein the protease is a bacterial protease.

7. A soap bar according to claims 1-6, substantially as described in the Examples.