EP0090650B1

EP0090650B1 - Detergent processing

Info

Publication number: EP0090650B1
Application number: EP83301768A
Authority: EP
Inventors: Terence Allan Clarke; Richard Barrie Edwards; Graeme Neil Irving
Original assignee: Unilever NV
Current assignee: Unilever NV
Priority date: 1982-03-29
Filing date: 1983-03-29
Publication date: 1987-08-26
Also published as: ES521071A0; DK138683D0; GB8308656D0; EP0090650A1; AU552416B2; GB2118854B; DK138683A; AU1285883A; DE3373196D1; PH21765A; MY8800006A; ES8405436A1; GB2118854A; PT76465A; NO831125L; CA1201357A; FI830997L; GR78503B; BR8301599A; PT76465B

Description

Field of the invention

This invention relates to the processing of soap containing feedstocks wherein the phases present in the feedstock are controlled.

Background to the invention

It is known that certain compositions of soap bars have properties which are perceived by users and which may be modified by subjecting the soap, as a solid or semi-solid mass, to mechanical working. A well known example includes the processing of transparent soaps (US-A-2,970,116).
We have discovered that such modifications arise from changes in the composition and structure of the phases present in the soap mass. Moreover, we have found that with conventional methods such changes only occur within a limited region of the volume subjected to mechanical working.
The phases referred to herein are those detectable by X-ray investigation but include changes in the domain size of the phases present, even when no change in the proportion of phases occurs.
The present invention utilises processing conditions to achieve phase change by subjecting the soap-containing feedstock to considerable working within a specific temperature range in an efficient manner, the temperature range being sensitive to the composition.
The soap-containing compositions of the invention are sensitive to the application of shear in that they undergo phase changes when subjected to shear.
The phase structure of soaps is discussed in "Industrial Oil and Fat Products" of Bailey (Ed D Swern) Volume I, 4th Edition. The phase associated with soap leaving the drier is omega. The Applicants view the beta phase as associated with physical hardening of bars and transparency and delta phase with the improvement of lather and mush properties of a superfatted material.

General description

Examples of properties which can be changed or generated by phase changes induced by mechanical working (shear) are: i) Transparency of certain soap compositions generally containing certain components to assist in the processing or provision of transparency, for example potassium soaps, glycerol, sorbitol and castor derived soaps; ii) Improvements in mush properties and lather volume of superfatted soap which contains an amount, usually 1% to 15%, of free fatty acid. A level of free fatty acid above 5% is usually required to obtain the benefit when the moisture level is 8% to 12%. With amounts of tallow above about 70% in a tallow/coconut charge the free fatty acid is preferably present at a level of above 7.5%, more preferably above 10%; iii) Hardening soaps having a relatively low TMF (Total Fatty Matter) for example those containing an above average, say greater than 13%, amount of water; iv) Hardening soaps having a relatively high proportion of unsaturated acids. Examples of these feedstocks will be derived from tallow, palm oil and soya. These and other feedstocks provide physically soft soaps.
Processing of these soaps by conventional equipment to obtain these modifications will be difficult because the modification to properties is achieved at low efficiency. Thus several passes through a mill or prolonged working in a sigma blade mixer are necessary to obtain a transparent product.
In general, the temperature of processing to achieve the desired effect is dependent on the composition and is within the range 30°C to 55°C, although some compositions may undergo shear induced phase change outside these limits.
The present invention provides an efficient process to obtain the desired phase changes by subjecting the soap feedstock to considerable working (shear) within specific temperature ranges in an efficient manner.
The present invention relates to the processing of a shear-sensitive soap-containing detergent formulation to control the phases present in the formulation wherein all the material is subjected to substantially even shear by passing the material with thermal control at an angle through a plurality of shear zone areas formed within the detergent material bulk by relative movement of surfaces between which the material passes, the shear zone areas being formed within the material by entraining temporarily material in the surfaces so that a velocity component of the material is altered by the relative movement during entrainment.
The entraining of the material is a positive retention by a surface so that a velocity component is increased or decreased; the direction of change depends on the geometric relationship of the surface to the material flow. The relative movement will preferably be uninterrupted to ensure the shear field is constant with time.
The device used in the process from the shear zone areas in the bulk of the material and their geometry ensures all the material is constrained to move through a plurality of the areas. Formation of the shear zone areas in the bulk of the material adjacent a surface allows efficient thermal control of the process to be achieved; preferably at least one of the surfaces is in thermal contact with a means of applying heating or cooling.
The devices used in the process of the invention are enclosed and thus allow control of the labile components which could be lost during treatment in an open vessel. Examples of these components are perfumes and water. The devices are also capable of efficient thermal control; this assists in controlling loss of these components.
In one device the formulation is passed between two closely spaced mutually displaceable surfaces, each having a pattern of cavities which overlap during movement of the surfaces, so that material moved between the surfaces traces a path through cavities alternately in each surface whereby the bulk of the material passes through the shear zone generated by displacement of the surfaces.
This device provides a single shear zone between the surfaces formed by the shear zone areas.
Another device has the shear zone areas formed in material passing alternately through apertures in stator and rotor plates, the material being entrained in the apertures during passage through the plates. An equivalent construction has rotating arms or blades between which the material is entrained. A set of coplanar arms forms a surface of the invention. The surfaces must have a thickness sufficient to entrain material as it passes through the surface.
A preferred geometry for each class of devices is cylindrical. The second device may also have terminal control means in contact with at least one surface.
Cavity transfer mixers are normally prepared with a cylindrical geometry and in the preferred devices for this process the cavities are arranged to give constantly available but changing pathways through the device during mutual movement of the two surfaces. The devices having a cylindrical geometry can comprise a stator within which is journalled a rotor; the opposing faces of the stator and rotor carry the cavities through which the material passes during its passage through the device.
The device may also have a planar geometry in which opposed plane surfaces having patterns of cavities would be moved mutually, for example by rotation of one plane, so that material introduced between the surfaces at the point of rotation would move outwards and travel alternately between cavities on each surface.
Another form of cylindrical geometry maintains the inner cylinder stationary while rotating the outer cylinder. The central stator is more easily cooled, or heated if required, because the fluid connections can be made in a simple manner; the external rotor can also be cooled or heated in a relatively simple manner. It is also mechanically simpler to apply rotational energy to the external body rather than the internal cylinder. Thus this configuration has advantages in construction and use.
Material is forced through the mixer using auxiliary equipment as the rotor is turned. Examples of the auxiliary equipment are screw extruders and piston rams. The auxiliary equipment is preferably operated separately from the mixer so that the throughput and work performed on it can be separately varied. The separate operation may be carried out by arranging the auxiliary equipment to provide material for processing at an angle to the centre line of the shear-producing device. This arrangement allows rotational energy to be supplied to the device around its centre line. An in-line arrangement is more easily achieved when the external member of the device is the rotor. Separate operation of the device and auxiliary equipment assists in providing control of the processing.
In general a variety of cavity shapes can be used, for example Metal Box (UK 930 339) disclose longitudinal slots in the two surfaces. The stator and rotor may carry slots, for example six to twelve, spaced around their periphery and extending along their whole length.
EPA 0048590 describes a specific form of cavity transfer mixer and suggests its application in soap processing.
There are six applications directed to detergent processing copending with the present applications. EPA 0090644 (83301762.7) describes the processing of a superfatted soap formulation to improve the properties. EPA 0090645 (83301763.5) describes the processing of a physically soft soap feedstock to provide a hardened product. EPA 0090646 (83301764.3) describes the processing of soap compositions to reduce grittiness. EPA 0090647 (83301765.0) describes the incorporation of a volatile component in a soap composition. EPA 0090648 (83301766.8) describes the aeration of a detergent formulation. EPA 0090649 (83301767.6) describes the production of transparent soap compositions.
The soap feedstock may contain non-soap detergents in amounts which do not interfere with the desired effect. Examples of these actives are alkane sulphonates, alcohol sulphates, alkyl benzene sulphonates, alkyl sulphates, acyl isethionates, olefin sulphonates and ethoxylated alcohols.
The processed feedstock may be made into bar form using standard stamping machinery. Other solid product forms, e.g. extruded particles (noodles) and beads can be prepared from the feedstock.

Drawings

The invention will be described with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a longitudinal section of a cavity transfer mixer with cylindrical geometry;
Figure 2 is a transverse section along the line II-II on Figure 1;
Figure 3 illustrates the pattern of cavities in the device of Figure 1;
Figures 4, 5 and 7 illustrate other patterns of cavities;
Figure 6 is a transverse section through a mixer having grooves in the opposed surfaces of the device;
Figure 8 is a longitudinal section of a cavity transfer mixer in which the external cylinder forms the rotor;
Figure 9 is a longitudinal section of a device in which material is passed through a series of apertured discs, and
Figure 10 is a view of an apertured disc.

Specific description of devices

Embodiments of the devices will now be described.
A cavity transfer mixer is shown in Figure 1 in longitudinal section. This comprises a hollow cylindrical stator member 1, a cylindrical rotor member 2 journalled for rotation within the stator with a sliding fit, the facing cylindrical surfaces of the rotor and stator carrying respective pluralities of parallel, circumferentially extending rows of cavities which are disposed with:

a) the cavities in adjacent rows on the stator circumferentially offset;
b) the cavities in adjacent rows on the rotor circumferentially offset; and
c) the rows of cavities on the stator and rotor axially offset.

The pattern of cavities carried on the stator 3 and rotor 4 are illustrated on Figure 3. The cavities 3 on the stator are shown hatched. The overlap between patterns of cavities 3, 4 is also shown in Figure 2. A liquid jacket 1A is provided for the application of temperature control by the passage of heating or cooling water. A temperature control conduit 2A is provided in the rotor.
The material passing through the device moves through the cavities alternately on the opposing faces of the stator and rotor. The cavities immediately behind those shown in section are indicated by dotted profiles on Figure 1 to allow the repeating pattern to be seen.
The material flow is divided between pairs of adjacent cavities on the same rotor or stator face because of the overlapping position of the cavities on the opposite stator or rotor face.
The whole or bulk of the material flow is subjected to considerable working during its passage through the shear zone generated by the mutual displacement of the stator and rotor surfaces. The material is entrained for a short period in each cavity during passage and thus one of its velocity components is altered.
The mixer had a rotor radius of 2.54 cm with 36 hemispherical cavities (radius 0.9 cm) arranged in six rows of six cavities. The internal surface of the stator carried seven rows of six cavities to provide cavity overlap at the entry and exit. The material to be worked was injected into the device through channel 5, which communicates with the annular space between the rotor and stator, by a screw extruder. The material left the device through nozzle 6.
Figure 4 shown elongate cavities arranged in a square pattern; these cavities have the sectional profile of Figure 2. These cavities are aligned with their longitudinal axis parallel to the longitudinal axis of the device and the direction of movement of material through the device; the latter is indicated by the arrow.
Figure 5 shows a pattern of cavities having the dimensions and profile of those shown in Figures 1, 2 and 3. The cavities of Figure 5 are arranged in a square pattern with each cavity being closely spaced from four adjacent cavities on the same surface. This pattern does not provide as high a degree of overlap as given by the pattern of Figure 3. The latter has each cavity closely spaced to six cavities on the same surface, i.e. a hexagonal pattern.
Figure 6 is a section of a cavity transfer mixer having a rotor 7 rotatably positioned within the hollow stator 8 having an effective length of 10.7 cm and a diameter of 2.54 cm. The rotor carried five parallel grooves 9 of semi-circular cross section (diameter 5 mm) equally spaced around the periphery and extending parallel to the longitudinal axis along the length of the rotor. The inner cylindrical surface of the stator 8 carried eight grooves 10 of similar dimensions extending along its length and parallel to the longitudinal axis. This embodiment utilised cavities extending along the length of the stator and rotor without interruption. A temperature control jacket and its conduit were present.
Figure 7 shows a pattern of cavities wherein the cavities on the rotor, shown hatched, and stator have a larger dimension normal to the material flow; the latter is indicated by an arrow. The cavities are thus elongate. This embodiment provides a lower pressure drop over its length compared with devices of similar geometry but not having cavities positioned with a longer dimension normal, i.e. perpendicular, to the material flow. To obtain a reduction in pressure drop at least one of the surfaces must carry elongate cavities having their longer dimension normal to the material flow.
The cavity transfer mixer of Figure 8 had the external cylinder 11 journalled for rotation about central shaft 12. Temperature control jacket 13 and conduit were present but the latter is not shown because the cavities in the central shaft are shown in plan view while the rotor is sectioned. The central stator (diameter 52 mm) had three rows 14 of three cavities with partial, i.e. half cavities, at the entry and exit points. On the rotor there were four rows 15 of three cavities. The cavities on the stator and rotor were elongate with a total arc dimension of 1.5 cm normal to the material flow with hemispherical section ends of 1.2 cm radius joined by a semicircular sectioned panel of the same radius. The cavities were arranged in the pattern of Figure 7, i.e. with their long dimension normal to material flow. The rotor was driven by a chain drive to external toothed wheel 16.
A device capable of generating a series of separate shear zone areas is shown in longitudinal section in Figure 9. In inner cylindrical rotor 17 is journalled for rotation within cylindrical stator 18. The length of the device measured between the outer surfaces of the two end discs is 10 cm and the stator has an internal diameter of 6.5 cm. The stator 18 carries five inwardly directed discs 19 which are arranged alternately with four discs 20 extending outward from rotor 17.
Each of the nine discs has the pattern of apertures shown in Figure 10. The apertures 21 in the outer ring have a diameter of 0.8 cm and apertures 22 a diameter of 0.5 cm.
Material is moved through the device in the direction of the arrows by means of auxiliary apparatus, for example a soap plodder. The material passes through the apertures in the nine discs but rotation of rotor 17 causes the formation of a shear zone area between each pair of discs as the material is entrained in the apertures of each disc.
Thermal control means can be mounted on either or both the stator and rotor. A jacket 23 is shown in thermal contact with stator 18; a conduit 24 is positioned within rotor 17.
The discs 19 had a thickness of 1.0 cm and the discs 20 a thickness of 0.6 cm. The periphery of each disc was closely spaced from the adjacent surface of the stator or rotor to ensure all the material passing through the device passed through the shear zone areas.
The strength of the shear zone are at any point is proportional to the distance (d) of the point from the rotational axis. The presence of the rotor 17 occupying the central axis of the device ensures all the material is given substantially even treatment in the shear zone areas. The ratio of shear field strengths may be up to 10:1 with a narrow rotor. That is the material occupies a volume having an outer radius ten times larger than the inner radius. Preferably the device will be designed to have a ratio approaching unity, but the desirability of evenness of shear zone strength must be balanced against the requirement for a path section providing an acceptable throughput. In the device described the ratio is about two.
The provision of substantially even shear treatment along a radial dimension may also be provided by selecting the dimensions of the apertures in the discs. The shear field at a point is proportional to the distance (d) from the rotational axis and the aperture dimensions are preferably chosen so that the ratio of "d" at any point to the throughput at that point is substantially constant. This approach to the design of the apertures is applicable outside the 10:1 ratio noted previously.

Examples

Examples of processing soap-containing detergent materials will now be given:

Example I

The fats, oils and rosin were added to the nigre of the previous boil to give the required blend (74 tallow/26 coconut). The mix was then saponified using NaOH/KOH and fitted so that neat soap separated on top of the nigre and a small amount of lye. The neat soap layer was removed and additional glycerol added together with additional electrolyte. The soap was vacuum dried to a composition of
As prepared this formulation leads to opaque soap chips.
The opaque soap chips at 43°C were passed into the cavity transfer mixer of Figure 1 by use of a soap plodder at 516 g min-' and left the mixer at 49°C. Cooling water was passed through jacket 1A and conduit 2A. The mixer was operated at 120 revolutions per minute. The extruded billet had a commercially acceptable transparency equivalent to that obtained by energetically working in a sigma blade mixer for 60 minutes in the temperature range 40°C to 48°C.
Transparency was measured using the method described in US-A-3274119 (5 mm thick sample); the feedstock gave a reading of 2.5% and the product 67%. Similar results were achieved using a cavity radium of 1.2 cm.
Other configurations of cavity are shown in Figures 4, 5 and 7 with the cavity pattern on the stator shown hatched.

Example II

In this Example a degree of transparency is provided in a soap base by utilising a cavity transfer mixer having longitudinal grooves on the opposed surfaces of a rotor/stator combination with cylindrical geometry, there being a narrow gap with nominal sliding fit between rotor and stator.
The soap base used in Example I was passed through the device from a soap plodder at a rate of 28 g/min-'. The base material is moved through the device transferring alternately between the grooves in the rotor and the stator and thereby travelling through the shear layer in the material between the opposed surfaces. The temperature at extrusion was about 45°C and the rotor was driven at 100 revolutions per minute by suitable gearing from the plodder. Water cooling was applied to the stator and rotor.
The transparency was measured using the method of Example I; the feedstock base gave a reading of 2.5% and the product 11.5%. Although this transparency is unlikely to be sufficient for a commercial product it indicates a device with the geometry described produces a degree of transparency in a suitable feedstock.

Example III

The formulation described in Example I was passed through a device having the general features of construction of that described in Figure 1. The cavities had a hemi•spheriεal section with a radius of 1.2 cm and were arranged on the external stator in eight rows of six cavities arranged circumferentially. The centrally positioned rotor (diameter 52 mm) had seven rows of six cavities with partial (i.e. half) cavities at the entry and exit points.
The rotor was rotated at 125 revolutions per minute and a throughput of 490 g per minute was provided by a soap plodder. The temperature of the soap was 20°C at entry and 51°C at exit. Water cooling was applied to the stator and rotor components.
The material extruded from the device had a transmission of 69%.

Example IV

Example III was repeated with cavities having a radius of 0.7 cm. The stator carried 12 rows of cavities with 10 cavities arranged circumferentially. The rotor was turned at 75 revolutions min-¹ and a throughput of 170 g min-' was provided from a soap plodder. The input and output temperatures were 32°C and 46°C and the transmission of the final product was 69%. Water cooling was applied to the stator and rotor.

Example V

Example III was repeated using an array of cavities as illustrated in Figure V, that is with a cubic array. The cavities had a hemispherical section with a radius of 1.2 cm and were arranged on the external stator in six rows of six cavities arranged circumferentially. The centrally positioned rotor (diameter 52 mm) had five rows of six cavities with partial, i.e. half, cavities at the entry and exit points.
The rotor was rotated at 150 rpm in with a throughput of 450 g/minute provided by a soap plodder. Water cooling was applied to the stator and rotor components; the temperature of the soap was 25°C at entry and 48°C at exit.
The material extruded from the device was found to have a transmission of 69%.

Example VI

Example III was repeated using the cavity array shown in Figure 7. The cavities were elongate with a total arc dimension of 5.1 cm normal to the material flow formed with hemispherical section ends of 1.2 cm radius joined by a semicircular sectioned panel of the same radius. The cavities were arranged on the external stator in six rows of three cavities arranged circumferentially. The central rotor (diameter 52 mm) had five rows of three cavities with partial, i.e. half, cavities at the entry and exit points.
The rotor was rotated at 176 rpm in with a throughput of 460 g/minute provided by a soap plodder. Water cooling was applied to the stator and rotor components; the temperature of the soap was 25°C at entry and 47°C at exit.
The material extruded from the device had a transmission of 67%.

Example VII

Example III was repeated using the cavity array shown in Figure 4. The cavities were elongate with a total dimension of 8.4 cm parallel to the material flow and formed with hemispherical section ends of 1.2 cm radius joined by a semicircular sectioned channel of the same radius. The cavities were arranged on the external stator in three rows of six cavities arranged circumferentially. The centrally positioned rotor (diameter 52 mm) had two rows of six cavities with partial cavities at the entry and exit points.
The rotor was rotated at 176 rpm in and a throughput of 425 g/minute was provided by a soap plodder. Water cooling was applied to stator and rotor components; the temperature of the soap was 26°C at entry and 49°C at exit.
The material extruded from the device had a transmission of 64%.

Example VIII

The apparatus described in Example I was used.
A soap feedstock of 60% tallow 40% coconut with 7!% of the feedstock being present as free fatty acid was used. The soap was vacuum dried to 10% moisture and 0.6% electrolyte. The dried chips were extruded through the device with the aid of a soap plodder; the inlet temperature of the soap was 35°C and after passage through the device it was 37°C. Water cooling was applied to the stator and rotor. The rotor was operated at 50 rpm in and the throughput was 267 g min-^1. The extruded billet was cut and stamped into tablets.
The mush was measured by immersing a tablet in distilled water at ambient temperature for 2 hours and measuring the mush as the amount removed per 50 sq cm surface.
Lather was measured as the volume produced during hand washing.
The product tablets had reduced mush and increased lather compared to a commercial product prepared from the same feedstock.

Example IX

The apparatus of Example I was used with water cooling of the stator and rotor.
Tallow fat was saponified, washed, fitted and vacuum dried to 20% moisture. The chips were then extruded through the device with the aid of a soap plodder. The hardness was measured with a SUR (Berlin) penetrometer using a 9° conical needle under a total force of 200 g for 10 seconds. The results are given in the Table.

Example X

The apparatus of Example I was used with water cooling of the stator and rotor.
A soap feedstock comprising tallow 76% coconut 12% and soya bean oil 12% was prepared at a moisture content of 16.5%. The feedstock was processed as in Example III and the hardness measured.

Example XI

The apparatus of Example I was used with water cooling of the stator and rotor.
A feedstock of tallow/coconut 80/20 was prepared and then moisture increased to 18% by cold milling in additional water. The feedstock was processed as in Example IX and the hardness measured.
The treatment of these feedstocks thus produced a hardening of the bars.

Example XII

The cavity transfer mixer shown in Figure 8 was used to process the formulation of Example I. This formulation was passed through the device by means of a soap plodder at a throughput of 240 g per minute. The stator and rotor were cooled by water circulation and the rotor was turned at 148 revolutions per minute. The input and output temperatures of the material were 30°C and 46°C and the transmission of the final product was 61%.

Example XIII

The formulation of Example I was passed through the device illustrated in Figures 9 and 10 using a soap plodder. The rotor was turned at 175 rpm in and a throughput of 640 g per minute was provided by the plodder. The input and output temperatures were 27°C and 47°C with water cooling of the stator and rotor; the transmission of the product was 39%.

Example XIV

A soap feedstock of 60% tallow, 40% coconut (7.5% as free fatty acid) containing 10% moisture and 0.6% electrolyte was passed through the device illustrated in Figures 9 and 10 with the aid of a soap plodder. The soap (temperature 29°C) was passed at a rate of 216 g per minute and exited at 33°C to be cut and stamped to form tablets. Water cooling was applied to the stator and rotor. The rotor was rotated at 33 rpm in.
A tablet obtained by usual commercial processing was immersed in distilled water at 20°C for 2 hours; the layer of mush on an area of 50 sq cm was taken and weighed. The amount was 11.4 g; the tablet produced by this example gave a value of 7.0 g.

Example XV

The formulation of Example I was passed through the device illustrated in Figures 9 and 10 at a throughput of 1400 g per minute with the aid of a soap plodder; the rotor was operated at 215 rpm in. Water cooling was applied to the rotor and stator.
Under identical conditions using a penetrometer needle the feedstock gave a reading of 5.0 mm and the treated material a reading of 3.3 mm.

Examples XVI to XX

These examples utilised a cavity transfer mixing device with cavities of diameter 2.4 cm arranged circumferentially.
Eight cavities on the stator and seven cavities plus half cavities at each end on the rotor were present on the components shown in Figure 1. Water cooling was applied to the stator and rotor. The formulations, which had a relatively high water content and which contained feedstocks providing physically soft bars, are given in Table II. The results are quoted in Table III. The feedstock oils and fats are quoted as percentages of the fat charge.

Claims

1. A process for controlling the phases present in soap-containing feedstock that undergoes phase change when subjected to shear, in which the soap-containing feedstock is subjected to substantially even shear by passing the feedstock with thermal control at an angle through a plurality of shear zone areas formed within the feedstock bulk by relative movement of surfaces between which the feedstock passes, the shear zone areas being formed within the feedstock by entraining temporarily material in the surfaces so that a velocity component of the material is altered by the relative movement during entrainment.

2. A process according to Claim 1 wherein at least one of the surfaces is in thermal contact with a means of applying cooling.

3. A process according to Claim 1 or Claim 2 wherein the shear zone areas are each part of a single shear zone between the surfaces.

4. A process according to Claim 3 wherein the feedstock is passed between two closely spaced mutually displaceable surfaces, each having a pattern of cavities which overlap during movement of the surfaces, so that material moved between the surfaces traces a path through cavities alternately in each surface so that the bulk of the material passes through the shear zone generated by displacement of the surfaces.

5. A process according to Claim 1 or Claim 2 wherein the shear zone areas are formed in material passing alternately through apertures in stator and rotor surfaces, the material being entrained in the apertures during passage through the surfaces.

6. A process according to Claim 4 wherein the device has cylindrical geometry and the external cylinder is rotatable relative to the inner cylinder.

7. A process according to Claim 6 wherein the outer cylinder is in thermal contact with thermal control means.

8. A process according to any of Claims 4, 6 and 7 wherein the cavities in at least one surface are elongate with their longest dimension perpendicular to the material flow.

9. A process according to any preceding claim wherein the phase control is such that the transparency of the soap is increased.

10. A process according to any of Claims 1 to 8 wherein the phase control is such that the mush/lather properties of soap including about 1% to about 15% of free fatty acid are improved.

11. A process according to any of Claims 1 to 8 wherein the phase control is such that a soap-containing feedstock which includes above about 13% water and/or a proportion of feedstock acids providing physically soft formulations is hardened.

12. A process according to any preceding claim wherein the temperature of processing is within the range 30°C to 55°C.

13. A device for generating a shear layer in material passing through the device, comprising two closely spaced mutually displaceable surfaces each having a pattern of cavities which overlap during movement of the surfaces, so that material moved between the surfaces traces a path through cavities alternatively in each surface whereby the bulk of the material passes through the shear zone generated by displacement of the surfaces, characterised in that the cavities in at least one surface are elongate with their longest dimension perpendicular to the material flow.