The present invention relates to a system and a method for continuous casting of castable compositions such as soaps, detergent tablets and the like, and in particular to a system and method for continuous casting of such compositions involving quick and efficient solidification and shaping during traverse of the melt through a series of moulds .

Soap or non-soap detergent based shaped articles are conventionally known to be produced by way of extrusion or by casting routes.

The extrusion process usually involves a plodder or extruder to take care of the shaping of the article. By continuous extrusion of the soap/non-soap detergent through the extruder, continuous production of logs or billets can be obtained which can subsequently be stamped and shaped into tablets or bars.

As compared to the aforediscussed extrusion route which favours a continuous operation for production of soap or non-soap articles, the casting route is usually required for producing soaps with high formulation flexibility such as transparent soaps and those with high liquid content, which cannot be readily processed following the extrusion route.

GB 597322 discloses an improved method of making soap bars or tablets by rapidly chilling molten 63 % soap so as to solidify the soap within a few seconds, and thereafter

without subjecting it to a drying operation plodding the solidifying soap, where one or more steps are taken to increase the degree to which the soap mass is compacted during plodding. Importantly, the above process teaches that the solidification of the molten soap be effected by rapid chilling in a matter of few seconds, instead of by frame, slab or bar-cooling. Such rapid chilling produces soap which is firm and tough, and possesses adequate solidity and plasticity for satisfactory plodding and stamping.

WO 03/0125110 Al describes a continuous process for casting of soaps and the like comprising the steps of: (i) filling a continuous tube of flexible material with a melt of the castable compositions, where the tube acts as a sleeve to the composition such that the desired cross section area of the filled sleeve is obtained i.e. independent of its perimeter, and (ii) solidifying and simultaneously shaping the melt by cooling the sleeve in or on a suitable mould. The process produces cast-in-sleeve logs that can be cut into billets/tablets, and optionally flow wrapped.

It would be apparent from the above that such casting processes can be categorized under batch or at best a semi- continuous operation, since cooling of the filled pack is proposed as a separate unit operation. Further, separate shaping of the filled pack is required, which is again complex and adds to the production time. These operations are also found to be labour and capital intensive as compared to the extrusion process.

To overcome these difficulties in the prior art, our co- pending application 1218/MUM/2003 describes a system and a process for continuous casting of melt-cast products such as soaps, detergents and the like comprising: i. a substantially vertically disposable mould unit to favour solidification/casting of the melt cast composition during an upstream motion through the mould unit; ii. the mould unit being operatively connected at its lower end to a supply source of the melt-cast composition; iii. means for controlling the temperature of the melt in the mould. unit to achieve the desired solidification and shaping during traverse of the melt from the bottom of the mould towards the top thereof which is adapted to eject the formed cast product .

This co-pending application allowed for a vastly improved system and method for continuously casting castable compositions by way of traverse of the molten composition in a stationery mould while achieving uniform and complete filling of the mould free of dead regions and/or air pockets while having the much desired flexibility in manufacture and high throughput rates. However, it was found that scale up of the process to larger cross-sectional areas for the castable composition made the cooling and solidification of the castable composition increasingly difficult. With the use of moulds of larger cross-sectional areas, which were cooled by cooling jackets, it was found that the portions of the composition close to the jacket solidified faster while

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the core was still liquid. To overcome this problem, it was required that moulds of very long length be provided to ensure complete solidification of the composition.

The present invention provides for a system and process to overcome this problem, thus providing for quick and efficient method of cooling and solidifying the molten castable composition and/or providing for much shorter mould lengths .

It is thus the basic object of the present invention to be able to provide for a simple and continuous system and process for casting of castable compositions including soaps, detergent tablets, deodorant, confectionery and the like which would avoid the limitations of batch process and/or the semi continuous processes of casting presently available to the art.

Another object of the present invention is to be able to provide for a simple and effective system and method of continuous casting and shaping of soap or detergent products which would enable quicker and more efficient methods of cooling and solidifying the molten castable composition in a continuous manner.

Yet further object of the present invention is to be able to provide for a system and a method for continuous casting and shaping of castable products such as soap, detergents and the like, which while providing quick and efficient cooling and solidification of the composition minimizes the overall length of the moulds to ensure a compact manufacturing unit.

Thus according to a first aspect of the present invention, there is provided a system for continuous casting of castable products comprising:

(i) more than one (e.g. two to ten, conveniently two to three, four, five or six) substantially coaxial and serially disposed mould units; (ii) each mould unit having a larger cross sectional area compared to the preceeding unit; (iii) the mould units operatively connected at their inlet ends to a supply source of molten castable composition; and

(iv) means for controlling the temperature of the mould units .

A preferred aspect of the invention comprises substantially vertically disposed mould units.

The mould units as above are further preferably adapted such that the same subsequent to the upstream solidification /casting of the melt in its vertically disposed position can be gradually brought to a horizontal direction to favour ejection of the solid/cast product in the horizontal direction.

Also the system for continuous casting of melt-cast products can advantageously comprise a high-surface area heat exchanger provided ahead of the shaping moulds to improve the efficiency of cooling and throughput.

In accordance with a preferred aspect of the present invention the system for continuous casting of castable products comprises:

(i) more than one substantially co-axial and serially disposed mould units;

(ii) each mould unit having a larger cross sectional area compared to the preceeding unit; (iii) the mould units operatively connected at its lower end to a supply source of the melt of the composition;

(iv) means for controlling the temperature of the moulds comprising cooling jackets on the moulds having means for continuous supply of coolant there-through .

As per a preferred aspect of the system of the present invention, to favour effective cooling, the system is adapted to feed the coolant at the lower end of the cooling jacket and exit at the upper end.

In accordance with a further preferred aspect of the present invention, the means for controlling the temperature of the moulds such as the cooling jacket is adapted to have distinct temperature zones to facilitate selective temperature control of the melt during its traverse in the mould.

Additionally, in order to facilitate the release of the formed product while exiting from the last mould unit, in accordance with a further aspect, there is provided a

heating zone near the exit of the last mould unit to improve the slip of the bar and its throughput. Importantly, the vertical disposition of the moulds is preferred due to the uniform filling of the moulds with the molten composition from the bottom of the mould to form the cast bars free of problems of air pockets, and thereby achieve consistently good quality products.

In the above system according to a further aspect, the coaxially and serially disposed jacketed moulds each of a larger cross sectional area compared to the preceding mould includes means for selective injection of benefit/aesthetic agents in the formulation during the solidification/shaping process while it traverses the mould units, which cannot be achieved in case of any of known batch as well as the conventional slip casting systems. This aspect allows for different types of benefit agents to be introduced in different cross-sections of the composition. The viscosity of the cast soap material would vary along the flow direction due to cooling, and therefore the injected material with a wide range of viscosity can be used by appropriately choosing the injection point or points.

In accordance with another aspect of the present invention, there is provided a method for continuous casting of castable compositions comprising:

(i) supplying a molten castable composition through the inlet ends of each of the substantially coaxial and serially disposed mould units, each mould unit having a larger cross sectional area compared to the preceding mould unit;

(ii) cooling and solidifying the melt as it traverses through the mould; (iii) feeding the shaped solid from the exit end of one mould unit to the inlet end of the succeeding mould unit; and

(iv) ejecting the cast product from the exit end of the last mould unit.

In accordance with a preferred aspect of the present invention, in the above method for continuous casting of castable products the temperature of the mould units is controlled by regulating the temperature and/or flow rate of the coolant through jackets of the moulds.

Advantageously, in a preferred aspect of the process of the invention, the continuous production of cast bars is achieved by way of vertically upward, controlled filling and stage-wise cooling and solidification of the solid product, starting with the core while increasingly building up the cross-sectional area in jacketed moulds.

As and when desired the cross-sectional shape of the last mould is capable of being changed by change over of releasably secured mould (s) to obtain shaped bars of desired cross section thorough a continuous process. This provides for a simple mechanism for obtaining continuously shaped bars of varied cross section through a simple route, and with less involvement of labour.

The above method is simple, cost-effective (avoids wastages and recycling of wastes) and ensures production of shaped

bars repeatedly and continuously avoiding uneven bar and/or recycling of the product to attend uniformity in manufacture. Thus the above method of on-line continuous generation of bars by sequentially increasing the cross-section in a stage- wise manner in mould units serially disposed provides for efficient cooling and solidification without the need for unduly long mould lengths. Moreover, by way of a possible selective injection mechanism, benefit/aesthetic agents such as for example colouring agents slurry to provide stripes and/or benefit agents which can be introduced during the casting process in the mould units. This is never possible in case of batch processes, or in the case of the flexible sleeve casting presently available as a continuous casting method.

Following the above process of the invention, in continuous casting a secondary material can be continuously injected into the main bar while keeping it segregated. The viscosity of the cast soap material will vary along the flow direction due to cooling, and therefore the injected material with a wide range of viscosity can be used by appropriately choosing the injection position during traverse of the cast formulation through the jacketed mould.

Using the above system and the method of the invention, different products can be cast such as soaps, detergents, deodorants or confectioneries including non-quick setting materials at high throughput rates. The process is particularly preferred for home and personal care compositions such as soap and detergent bars.

Any conventional castable detergent composition is suitable for the process of the invention. This would allow much desired high formulation flexibility by way of a controlled continuous casting. The particularly preferred soap composition includes saturated fatty acid soap, detergent actives and possibly up to 60 % water with or without other additives and benefit agents.

The detergent actives suitable include any non-soap detergent actives or the salts of unsaturated fatty acids. Non-soap detergent actives are suitably selected from anionic, nonionic, cationic, amphoteric or zwitterionic surfactants or their mixtures.

The benefit/aesthetic agents which can be incorporated /injected during the casting include:

Liquid skin benefit agents or additives, including materials such as anti-ageing compounds, emollients, moisturizers, sunscreens, and any other known benefit agent. Solubilisers are suitable additives for use in the detergent composition include monohydric and polyhydric alcohols such as propylene glycol, sorbitol, glycerin, etc.

The melt-cast formulation can also include other optional ingredients such as hair conditioning agents, fillers, colours, perfume, opacifier, preservatives, one or more water insoluble particulate materials such as talc, kaolin, polysaccharides and other conventional ingredients.

For the selective solidification and shaping the mould temperature can be regulated based on the melt, which can be of any suitable temperature, such as up to 120 ⁰ C, preferably between 40 ⁰ C and 90 ⁰ C.

According to yet another aspect of the invention, there is provided a system for continuous casting of castable products comprising:

(i) more than one substantially parallel mould units operatively connected at its inlet end to supply source of melt of a composition and means for controlling the temperature of the substantially parallel mould units;

(ii) the substantially-parallel mould units operatively connected at their outlet ends to a mould unit, the mould unit operatively connected at its inlet end to a supply source of melt of the composition and having means for controlling the temperature of the mould unit.

A particularly desirable configuration of the substantially parallel mould units is that of a shell and tube type heat exchanger.

The details of invention, its objects and advantages are explained hereunder in greater detail with reference to the non-limiting accompanying figures wherein:

- Figure 1 is a schematic illustration of the front-view of a system for the continuous on-line production of soap bars in accordance with the present invention;

- Figure 2 is a schematic illustration of the sectional view of the soap bar produced with the system of invention as per Figure 1;

- Figure 3 is a schematic illustration of the front view of another aspect of the invention comprising substantially parallel mould units feeding into another mould unit in series; and

- Figure 4 is a schematic illustration of the sectional view of the soap bar produced with the system of invention as per Figure 3.

As shown in Figure 1, the system for continuous casting in accordance with the present invention involves three ^• jacketed moulds (MLDl, MLD2, MLD3) which are substantially co-axial and serially disposed with respect to each other.

Cooling jackets (CJl, CJ2, CJ3) are respectively provided on the three mould units which surround the moulds, and are provided with cooling means through the respective coolant entries (CEl, CE2, and CE3) at the bottom and the coolant exits (COl, CO2, C03) at the respective top.

The three moulds units as shown in the Figure 1 are selectively vertically disposed to facilitate a vertically upward feed of the soap melt from the bottom of the mould for the continuous casting. To facilitate such feeding of the mould from the bottom for the casting process the soap melt is metered into the mould (MLDl) through the bottom through inlet (Mil) from a tank (FT) by use of a metering pump (Pl) . Similarly inlets MI2 and MI3 are provided for

metering the soap melt to moulds MLD2 and MLD3 through pumps P2 and P3 respectively.

The system also includes injection means (IM) disposed in relation to the mould MLD3 to favour selective injection of colouring/benefit/aesthetic agents in the soap during its traverse through that mould unit.

In use, soap melt is pumped upwardly through mould MLDl using pump Pl through inlet means Mil. The soap melt cools and solidifies as it traverses upward through mould MLDl as coolant is passed through jacket CJl. A solid bar with cross-section Sl as shown in Figure 2 is formed and enters mould MLD2. At this point, soap melt is pumped into mould MLD2 through inlet means MI2 using pump P2. The soap melt cools and solidifies due to coolant being passed through jacket CJ2 and forms a soap bar with a cross-section of S2. The bar with cross-section S2 thus formed enters mould MLD2.

At this point soap melt is pumped into mould MLD3 through inlet means MI3 using pump P3. The soap melt cools around the bar with cross section S2 due to coolant being passed through jacket CJ3. As the melt traverses up the mould MLD3, an aesthetic agent e.g. colour is injected into the melt through injection means IM and solidifies along with the melt to form a soap bar with a cross-section of S3 which is ejected from the top of MLD3. As is evident from the Figure 3, the cross-sectional shape of Sl and S2 can be different, e.g. the cross-sectional shape of Sl and S2 can be circular while the cross-sectional shape of S3 may be oval. In this illustration, the region between S2 and S3 is

selectively coloured, thereby giving the visual aesthetic appeal to the product .

As shown in Figure 3, the system for continuous casting in accordance with another aspect of the present invention involves two substantially parallel moulds (MLDIl, MLD12) disposed in a shell and tube heat-exchanger type configuration. The moulds MLDIl and MLD12 form the tubes while the shell CJIl functions as the cooling jacket provided with coolant entry (CEIl) at the bottom and the coolant exit (COIl) at the top. The two moulds units as shown in Figure 3 are selectively vertically disposed to facilitate a vertically upward feed of the soap melt from the bottom of the mould for the continuous casting.

To facilitate such feeding of the moulds from the bottom for the casting process, the soap melt is metered into the moulds (MLDIl and MLD12) through the bottom from a tank (FT2) by use of a metering pump (P21) . The exit of the moulds MLDIl and MLD12 feed into the mould MLD 21 serially disposed with respect to the moulds MLDIl and MLD12. Mould MLD21 is operatively connected at its inlet end to a supply source of melt of another castable soap composition from tank FT3 through pump P22. Mould MLD21 is provided with a cooling jacket CJ21 having coolant inlet CE21 and coolant outlet C021.

When in use, the composition from the tank FT2 is metered into moulds MLDIl and MLD12 through pump P21. The soap bars solidify as they pass upwardly through the moulds MLDIl and MLD21 due to the flow of coolant through shell CJIl. The

solids bars from MLDIl and MLD12 enter mould MLD21. A different castable soap composition from FT3 is pumped using pump P22 into mould MLD21. The second castable soap composition solidifies in mould MLD21 around bars formed in MLDIl and MLD12 to exit from the exit end of MLD21. The cross sectional view of the soap bar formed is shown in Figure 4.

Importantly, the above system and method of the invention advantageously provides for continuous casting for soap/detergent bars and the like wherein the cooling and solidification of the composition is quickly and more efficiently achieved with minimum length of the moulds.