BACKGROUND AND PRIOR ART Modern laundry detergent compositions contain many ingredients, each performing a separate function. The majority of ingredients perform their function by their behaviour in solution. However also, ingredients are added in granular form to achieve an additional benefit, such as carrying a liquid component or to achieve a certain bulk density. Furthermore certain granular components can provide a significant additional benefit if they have a controlled microstructure. This may, for example, be to encapsulate a volatile ingredient to be released during use or to provide controlled sequential release of layered ingredients. However, one potential problem with such materials is that they are difficult to manufacture, especially on the large scale that is required of a laundry detergent composition.

US 4,804, 505 discloses a screw extruder operated in such a way as to maintain the specific mechanical energy at a constant level.

US 2001/0036503 Al discloses an extrusion process for producing encapsulated flavour or fragrances for use in the foods industry.

The present inventors have discovered that screw extrusion provides good control of microstructure and that relatively fragile compositions can be effectively produced with careful control of operating parameters.

The present invention provides a process for the manufacture of a structured material for use in a detergent composition, wherein the structured material is extruded in a screw extruder with a specific mechanical energy input of less than 75 kJ/kg.

DETAILED DESCRIPTION OF THE INVENTION Screw Extruders Screw extruders are used in a wide range of applications.

One such application is the generation of particles for use in detergent compositions. Screw extruders are particularly useful if it is desired to produce particles with a controlled microstructure as the extrusion process is more controlled and much less random'than, for example, a granulation process. However, due to the high formation pressures experienced in a screw extruder, the materials processed must usually be quite resistant to shear damage.

It is therefore quite challenging to produce relatively shear-sensitive compositions which have a controlled microstructure.

In order to achieve a reasonable commercially viable throughput, a screw diameter of at least 40 mm is required.

Generally a maximum of around 125 mm is appropriate.

Ideally the throughput is greater than 50 kg/hr, preferably greater than 100 kg/hr.

Preferably the screw extruder is a twin extruder as this provides better heat transfer.

Specific Mechanical Energy The specific mechanical energy relates to the amount of energy consumed by the screw extruder during operation per mass of material extruded. The skilled person is familiar with this term and it can be calculated by the following relationship: SME (J/kg) = Torque (Nm) x Screw Speed (r/min) Throughput (kg/min) Typical values of SME for screw extruders range from 300 to 1000 kJ/kg. For the present invention it is essential that an SME of less than 75 kJ/kg is used. Preferably it is less than 60, preferably less than 40, more preferably less than 30, desirably less than 20, advantageously less than 10 kJ/kg.

Structured Materials The structured materials which are produced by the method of the present invention are suitable for use in a detergent composition. That means that they would provide some useful function towards the cleaning and/or treatment of fabric materials during use.

The term structured means that the material has chemical or physical discontinuities within it on a length scale of from 1 to 200 micrometres, preferably from 10 to 100 micrometres.

Preferably the discontinuities are regular or ordered. The length scale of discontinuity can be determined by X-ray tomography or alternatively by invasive microscopic techniques.

Preferably the structure of the structured material is sensitive enough to suffer shear damage to the structure if the process were operated at a specific mechanical energy input of 300 kJ/kg, preferably at 200 kJ/kg, more preferably at 100 kJ/kg, most preferably at 75 kJ/kg.

Preferably the structure material comprises a glassy material with a glass transition temperature of greater than 0°C, preferably greater than 40°C, more preferably greater than 80°C. Suitable materials are sucrose, glucose, lactose, maltose, fructose, ribose, dextrose, isomalt, sorbitol, mannitol, xylitol, lactitol, maltitol, pentatol, arabinose, pentose, xylose, galactose, hydrogenated corn syrup, maltodextrin, agar, carrageenan, gums, polydextrose and derivitives amd mixtures thereof.

Preferably the structured material which is extruded comprises particles dispersed within a continuous medium.

Preferably this continuous medium is the glassy material as described above.

Preferably the structured material which is extruded comprises particles dispersed within a continuous medium.

Preferably these are polymer particles such as polybutylmethacrylate.

In a preferred embodiment the structured material comprises a laundry benefit agent e. g. , perfume. If perfume is present then it is particularly preferred that it is preserved within a continuous medium, preferably the glassy material, and preferably the perfume is present in the discrete particles as described above.

Detergent Compositions The extrudates produced by the present invention are suitable for use in detergent compositions. Preferably the detergent compositions are particulate and suitable for use as a laundry detergent used for everyday fabric cleaning.

Typically the extrudates produced by the present invention are present in such detergent compositions at a level of from 0.1 to 10 wt%, preferably from 0.5 to 5 wt%, of the detergent composition.

EXAMPLES Step 1: Preparation of Polymeric Particles A conventional emulsion based polymerisation is employed to produce a suspension of polymer (Poly butyl methacrylate) with a mean particle size of 70 to 120 microns in aqueous medium (may include part of continuous medium comprising of Maltose syrup). The maximum concentration of polymer in the suspension is about 40 wt%, which is limited by the viscosity of the system.

Step 2: Feed Preparation to Screw Extruder The emulsion made as in step 1 is then mixed and dispersed efficiently in an agitator with a laundry benefit agent (in this case, perfume) in a ratio of 1: 1 based on polymer weight. The feed composition is subsequently adjusted to around 20 wt% by manipulating ratio of continuous medium to final polymer concentration. It is clearly critical to maintain a certain level of moisture in feed to reduce viscosity of feed so that it can be handled by a suitable gear pump and ensure uniform dosing to the extruder.

Step 3: Preparation of Structured Particles A twin co-rotating screw extruder (L/D ratio of 40-45) is used to prepare the structured particles in the desired particle size range (500 microns to 1500 microns) for post mixing in a laundry detergent product. The extruder is configured by assembly of modular screw elements of

appropriate pitches to give desired flow and pressure profile. Further, the external surface is heated (either electrical or oil medium) to maintain desired temperature profile along the section from feed end to product end. The temperature conditions are set to remove moisture from feed to final product moisture less than 2 wt%. In order to facilitate higher moisture removal, four degassing sections are used, two operated at atmospheric pressure and other two operated under vacuum (0.3 to 0.7 bar). The product end of extruder is fitted with a suitable die design to produce strands of 0.8 to 1.0 mm diameter and a face cutter assembly to cut the strands into particles at an appropriate speed (variable up to 3000 rpm). It is desirable to cool the particles subsequently in a fluid bed operating at low velocity and the particles are directly fed onto a vibro- sieve to collect the product and remove any oversize particles.

The following results show the measured particle size of the structured particles when added to water. A high value of the volume-surface mean diameter (d3, 2) indicates that the structured material satisfactorily broke down in solution.

A low value indicates that shear damage was caused and subsequent break down in solution did not occur.

Screw Extruder Size: 24 mm Example Throughput Torque Nm Screw speed SME kJ/Kg Dispersion Kg/min (rpm) D3, 2 1 0. 036 6. 0 50 8. 13 99. 7 A 0.050 6.0 700 84.23 226.3 B 0.050 9.20 600 110.34 128.4 2 0.050 9.38 300 56.29 59.5 3 0.050 10.64 100 21.28 66.7 4 0.071 4.0 75 4.22 52.7 5 0.071 8.63 150 18.22 64.1

Screw Extruder Size: 44 mm Example Throughput Torque Nm Screw speed SME kJ/Kg Dispersion Kg/min (rpm) D3,2 6 0.583 50.88 200 18.50 83.3 7 0.583 42.40 125 9.64 86.9 8 0.700 50.88 225 16.35 93.5 9 0.700 67.84 300 29.07 72.3 10 0.700 50.88 200 15.66 103.2 11 0.850 50.88 400 23.94 81.2 C 0. 333 80.75 325 78.00 594.6 Screw Extruder size: 65 mm Example Throughput Torque Nm Screw speed SME kJ/Kg Dispersion Kg/min (rpm) D3, 2 14 1. 248 140. 00 175 19. 63 56. 8 15 1.320 196. 00 150 22.27 67.2 16 1.332 224.00 150 25.23 71.3 17 1.656 168.00 300 30.43 64.1 18 1.680 140.00 250 20.83 74.8 19 1.788 252.00 248 34.95 83.4 20 1.920 280.00 300 43.75 98.8

From the above tables, it is quite clear that with increasing SME, the dispersibility of particles in a laundry washing process decreases due to poor structuring of particles possibly caused by higher shear in extrusion.