The present invention relates to a process for producing transparent soap material comprising one or more functional additives by subjecting shear-sensitive soap material to transparency-generating working as well as to transparent soap material comprising functional additives thus obtained, particularly shaped transparent soap bars, noodles or pellets.

Soap bars which are transparent have an aesthetic appeal to consumers, also because transparency is sometimes associated with "naturalness". Therefore, there is a demand for transparent soap bars.

Methods of making transparent soap have been described in Unites States Patent Specification US-A-2,970,116 (Lever Brothers Company) and more recently in European Patent Specification EP-B-0,090,649 (Unilever). Basically, these methods comprise subjecting a shear-sensitive soap material to working, during which the mechanical energy is converted into heat energy, to such an extent that the temperature of the material is raised so that transparency is developed throughout the material. Although good transparent soap bars can be obtained in an economical way by using these methods, there is the disadvantage that under the conditions of high shear and elevated temperature the necessary functional additives, particularly perfume material, are seriously reduced in quality. Accordingly, the perfume release is often very low and higher levels of perfume are necessary to improve this. An increase in the level of perfume leads to poor transparency and difficult processing occurs.

In order to solve this problem for germicides, it has, for example, been proposed in United States Patent Specification US-A-3,969,259 (Lever Brothers Company) to

dissolve the germicide in the normally liquid perfume substances and to incorporate this solution into the soap at an early stage of the processing following the step of drying the neat soap and prior to extrusion of the plodded soap. The solution is added at a time sufficiently ahead of the extrusion step to allow thorough mixing throughout the soap mass. In general, the solution is added to the soap mass prior to completion of the working thereof, which is performed in a mixer, in which the temperature is raised, owing to the shearing and the working of the soap mass. Although the specific germicide can be incorporated into the soap without giving rise to specks of undispersed germicide, the amount of working of the soap mass comprising the sensitive functional additives is still such that the quality of the final bar is at risk.

A production line for the manufacture of transparent soap bars usually comprises a mixer, then a multiple roller mill and a vacuum refiner/plodder, followed by a ^" cutter and a stamper. In the manufacture of transparent soap noodles or bars, a batch of soap is usually recirculated over part of the production line to impart sufficient shear energy to bring the soap into a transparent state.

During extensive investigations it has been found that the total amount of shear energy necessary for obtaining a perfumed, transparent good quality soap bar can be split into the energy required to bring the soap into a transparent state and the energy which is required to dissolve the perfume (or any other shear- and/or heat- sensitive functional additive) in the soap. It was found that, using high perfume levels and perfumes which act as lubricants, it was sometimes hardly possible to obtain a transparent product at all, and in any case the number of recycles over the production line became unacceptably high. It turned out that, if the perfume was added after the production of a transparent soap noodle, a far better

transparent, perfumed product could be obtained. Also higher levels of perfume, sometimes up to double or more of the original amount, could be incorporated into the soap noodles, irrespective of the perfume quality, and also appreciably less shearing and working were needed to obtain transparency in the soap before the addition of the perfume. Also the form stability (plastic behaviour) of the soap proved to be better.

Therefore, the present invention relates to a process for producing transparent soap material comprising one or more functional additives by subjecting shear-sensitive soap material to transparency-generating shearing and working, which is characterized in that first the required degree of transparency is imparted to the soap material, after which an effective amount of the functional additive is mixed with the transparent soap material and, optionally, the final mixture obtained is converted into shaped form.

The final mixture may be converted into bars, noodles, pellets or any other suitable form or shape by methods known per se .

It is known from British Patent Specifications GB-A- 2,126,604 and GB-A-2,126,603 (Colgate-Palmolive Comp.) how to prepare translucent soap bars or cakes with functional additives. "Transparent" has been qualified as the ability to read 14 point bold face type through a 0.25 inch or 6.4 mm soap thickness. It has also been described in these patent specifications that perfume and any other desired adjuvants which will not objectionably opacify the mix are added to translucent soap material or material capable of being converted to translucent form with a reasonable amount of working. This implies, however, that the functional additives will be subjected to mechanical shear, which may detrimentally affect their final function. It is the merit of the present invention that first a transparent

soap is produced (which goes further than a translucent soap!) and only then the functional additives are incorporated. This problem and its solution have not been recognised or suggested in these patent specifications.

The functional additive may be selected from the group consisting of antioxidants, such as tocopherols, BHA, BHT and the like; chelating agents, such as EDTA and the like; colouring agents; deodorants; dyes; emollients; enzymes; foam boosters, which may be selected from anionic, amphoteric, nonionic and certain cationic surfactants, such as sodium cocoyl isethionate, sodium lauryl ether sulphate and the like; foam stabilizers; germicides; lathering agents; moisturizers; optical dyes; pearlescers; perfumes; sequestering agents; skin conditioners, such as dimerized fatty acids; solvents such as propylene glycol, glycerol, sorbitol, at least partially hydrogenated sugars and the like; stabilizers; superfatting agents, such as fatty acids; UV absorbers and mixtures of these functional additives.

The functional additives may be used in any desired quantity to effect the desired functional characteristics, and usually minor amounts from about 0.01% by weight up to 10% by weight are used. Some of the additives such as, for instance, foam boosters, foam stabilizers or solvents, may be used in larger amounts of up to 50% by weight or more.

The soap material comprises a mixture of soluble soaps and insoluble soaps. By "soluble" soaps are to be understood throughout this specification and the attached claims : the salts of saturated monocarboxylic acids or fatty acids having from 8 to 14 carbon atoms and additionally the salts of at least ono-unsaturated monocarboxylic or fatty acids having from 8 to 22 carbon atoms. By "insoluble" soaps are to be understood throughout this specification and the attached claims : the salts of saturated monocarboxylic or

fatty acids having from 16 to 24 carbon atoms. The salts of the monocarboxylic or fatty acids are preferably sodium salts, but small amounts of potassium soaps, ammonium soaps or alkanolamine soaps may also be present. The selection of the soaps depends on availability and cost, but suitable soaps are derived from coconut oil, palm kernel oil, tallow, hydrogenated tallow, palm oil, and the like and mixtures thereof.

The soap material may also comprise a crystallization modifier, such as hydroxystearic acid, polymerized unsaturated fatty acids, like dimerized and/or trimerized fatty acids, iso-stearic acid and their alkali metal soaps.

The soap material may also comprise an effective amount of one or more synthetic or non-soap detergents, which may be of the anionic, nonionic, amphoteric or cationic type, or mixtures thereof. Usually, up to 25% by weight of the total composition of synthetic or non-soap detergent is used.

Suitable cationic detergents include quaternary ammonium compounds, such as stearyl dimethyl benzyl ammonium chloride, and the like.

Suitable amphoteric detergents include the alkyl-β- iminodipropionates and iminopropionates and long-chain imidazole derivatives.

Suitable anionic detergents include the alkyl aryl sulphonates, such as C ₁₀ -C, ₅ alkyl benzene sulphonates; the olefin sulphonate salts; the C _n) -C ₂₀ paraffin sulphonate salts; the C ₈ -C ₂₂ fatty acyl sarcosinates; the C ₈ -C ₂₂ fatty acyl isethionates and C _ii -C ₂₂ fatty acyl N-methyl taurides; the C _κ -C ₂₂ fatty acid alkanol amides; the C ₈ -C ₂₀ alkyl sulphates and the sulphate esters of the reaction product of 1-20 moles of an alkylene oxide with 2 to 5 carbon atoms and a saturated, straight- or branched-chain aliphatic

monohydric C ₈ -C ₂₀ alcohol, such as sodium lauryl ether sulphate.

Suitable nonionic detergents include the reaction products of 1-50 moles of C ₂ -C ₄ alkylene oxide with C ₈ -C ₂₀ primary or secondary alkanols, with dihydric alcohols, and the like.

The shear-sensitive soap material is subjected to shearing and working in a manner known per se , such as according to European Patent Specification EP-B-0, 090,649 (Unilever) or United States Patent Specification US-A-2,970, 116 (Lever Brothers Company) .

The method according to the present invention has the following advantages : a higher level of perfume and also different types of perfumes can be incorporated, the final soap bar is less sticky so that higher stamping rates are possible, the form stability of the soap is better, there is less rework on the soap-manufacturing line and particularly this method offers a far greater flexibility in the further conversion into a finished soap bar than the prior art processes.

The invention will now be illustrated by the following Examples.

EXAMPLE I

A soap formulation was prepared, consisting of: 56.4% by weight of sodium soap of palm oil fatty acids, 14.1% by weight of sodium soap of palm kernel fatty acids, 2.5% by weight of free palm oil fatty acids, 5% by weight of sorbitol, 7% by weight of glycerol and 15.1% by weight of water. Hereafter, 1% by weight of perfume, based on the weight of the soap present, was admixed.

After mixing for 5 minutes, the temperature of the composition was 22.5°C. 5 Kg of the soap composition was passed once through a triple roll mill having a gap setting of 200 microns between roll 1 and roll 2 and 100 microns between roll 2 and roll 3. The temperature of the composition after passage was 26.6°C. Subsequently the composition was passed through a laboratory Mazzoni M-100 duplex refiner/plodder with refining sieves of 0.5 mm and provided with a rectangular extrusion die of ^" 45 mm x 19 mm at the end of the conical outlet. The cylinder temperatures were set at 30°C and the cone temperature was 57°C. The speed of the plodder screw was fixed at 2.5 (related to rotation speed) . The temperature of the composition after passage through the duplex refiner/plodder was 37.3°C. The output velocity was 44.5 kg/h. The transparency of a soap bar obtained from this composition was 1.8. The transparency was evaluated by measuring the light absorption of a slice of soap having a thickness of 18.5 mm and expressing this value as a percentage of the light transmission of a matted glass standard, using a reflectometer according to Dr B.Lange, Type LMG 008. The transmission of the standard compared to air is 8.3% and this value is taken as 100% throughout the measurements. A transparency value of 15 is generally rated as acceptable for transparent soaps.

In a second experiment, the same soap composition (without added perfume) was first imparted a transparency value of 8.3 by passing it 4 times through the laboratory Mazzoni M-100 duplex refiner/plodder, and 5 kg of this transparent soap having a moisture content of 13.4% by weight was mixed with the same amount of perfume of the same type as previously mentioned. After mixing, the temperature of the soap composition was 21.4°C. After 1 passage through the triple roll mill, the temperature of the soap composition was 27.5°C and after 1 passage through the duplex refiner/plodder the temperature was 37.1°C. The transparency of a soap bar obtained from this composition was 24.9 and the output velocity was 55.8 kg/h.

EXAMPLE II

The same soap formulation as in Example I, but now having a moisture content of 14.8% by weight and using 3% by weight (based on the total amount of soap present) "of the same perfume as in Example I, was processed on a laboratory

Mazzoni M-100 refiner/plodder with refining sieves of 0.5 mm and having the same die as in Example I. The cylinder temperature was set at 30°C and the cone temperature was 57°C. The speed of the plodder screw was fixed at 2.5 (related to rotation speed) .

5 Kg of the soap formulation was used and this batch was recycled 4 times and thereafter recycled for 5 and 10 minutes, respectively, at a reduced pressure of 40 mm Hg (cycles 5 and 6) . The following results were obtained:

The output velocity was 24.8 kg/h and the final transparency of the soap was 4.5 (measured with a 20 mm thickness soap bar) .

When the experiment was repeated, but using soap having a moisture content of 13.2% by weight and a transparency value of 8.3, the following results were obtained :

The output velocity was 43.6 kg/h and the final transparency was 45.5 (measured with a 20 mm thickness soap bar) .