Field of the Invention

The present invention relates to a system and a process for continuous casting of melt cast compositions such as soaps, detergent tablets and the like. In particular, the invention relates to a system and method for continuous casting of such melt cast compositions involving solidification and shaping of the melt-cast composition during traverse of the melt through a mould which favours continuous and effective mould filling and release as well as flexibility in generating a wide range of cast products.

Background and Prior Art

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 involve a plodder or extruder to take care of compaction and shaping of the article and 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.

Contrary to the above-discussed extrusion route which allows a continuous operation for production of soap or non-soap articles, the casting route is usually used for producing soaps with high formulation flexibility such as transparent or translucent soaps and those with high liquid content, which cannot be readily processed following the extrusion route.

US-A-2, 385,322 discloses a machine for solidifying and stacking a material that may be extruded and solidified comprising means to extrude said material and means to receive and support the extruder material while it is solidified, means for feeding a rack into position to receive the solidified material, means to automatically feed a second rack into said position as the preceding rack is filled, means to severe the extruded stick and means to feed a rack passed the severing means whereby the severed product may be placed on the rack. The system is basically a highly mechanized and complex mould filling, solidification and release system.

GB-A-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 produce soap which is firm and tough and possess adequate solidity and plasticity for satisfactory plodding and stamping.

EP-A-321,179 discloses a method of casting soap or detergent wherein liquid or semi liquid soap is filled into a pack made of flexible film such that the material occupies the whole of the pack. The pack is then tightly sealed to extrude air and the material is allowed to set in

the pack to obtain cast-in-pack tablets. This process helps in producing a continuous string of packed soap sachets. The process although refers to a continuous methods of casting requires sealing and pressurizing of individual sachets and is supposed to significantly slow down the throughput rates. Moreover, the process essentially calls for the use of extendable or shrinkable polymers to avoid formation of wrinkles on the cast tablets.

WO-A-03/0125110 refers to yet another 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, (ii) solidifying and simultaneously shaping the said melt by cooling the said sleeve in or on a suitable mould. The process produces cast-in-sleeves logs that can be cut into billets/ tablets and optionally flow rapped.

It would be apparent from the above that the known casting processes of the prior art can be categorized to be batch or at best semi-continuous methods since cooling of the filled pack is proposed as a separate unit operation. Furthermore, separate shaping of the filled pack is required, which is again complex and adds to the production time. Thus, while the casting routes presently available in the art, do provide for greater flexibility in formulation with high levels of water and/or benefit agent contents, these routes are found to be labour and capital intensive

as compared to the extrusion process due to their batch or at best semi-continuous mode of operation.

Methods involving mechanized mould filling and release mechanism or flexible moulds where the material sets in the mould and is cut along with the mould material have also been developed, but such processes also include the separate stages of filling, setting and releasing/cutting for obtaining the shaped bar, resulting in complexities in control. Such processes also affect the productivity and require high capital investment due to the need for sophisticated machinery and equipment.

In our co-pending application 1218/MUM/2003, a novel system has been disclosed 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 said mould unit; (ii) said mould unit being operatively connected at its lower end to a supply source of the melt-cast composition and (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 said mould towards the top thereof which top is adapted to eject the formed cast product .

In that co-pending application, it was disclosed that the vertical disposition of the jacketed mould and the filling of the mould for the continuous casting from the bottom to exit cast/formed bars from the top is necessary in order to provide for uniform and complete filling of the mould

jacket and achieve consistent product form free of problems of air pockets and/or any required re-circulation during startup.

After extensive experimentation, the present inventors have now found that it is not essential to have the mould in the substantially vertical direction for complete filling of the mould and that continuously cast bars and products of highly uniform shape free of problems of air pockets and/or any re-circulation during startup, can be produced in a consistent manner from substantially horizontal or inclined moulds.

The present inventors have solved this problem of non- uniform filling of the horizontal or inclined mould with the molten solution and the possible subsequent problem of air-pockets in the cast bar, by providing a means for bringing about a resistance to the flow of the molten solution during the start-up stage.

Objects of the Invention

It is thus the basic object of the present invention to provide a simple and continuous system and process for casting of setting materials including non-quick setting materials such as soaps, detergent tablets, deodorant, confectionery and the like, which process would avoid the limitations of the batch processes and/or the semi continuous processes of casting presently available to the art.

Another object of the present invention is to provide a simple and cost-effective continuous casting system and

process which would enable on-line continuous production of shaped products such as soaps, detergent tablets and the like without the need for separate unit operations for cooling and shaping of the product in the moulds and which favour solidifying and shaping of the molten soap during a simple traverse of the soap through a selective cooling- plus-moulding unit.

Another object of the present invention is to provide a simple and effective system and method of continuous casting and shaping of soap, detergent products, which enable greater flexibility in controlling the characteristics of the product form such as those required for obtaining special quality product like soaps with high solvent content such as transparent or translucent cast bar and/or with advantageous benefit/aesthetic agent incorporation.

Yet further object of the present invention is to provide a system and a method for continuous casting and shaping of castable products such as soap, detergents and the like, which involve minimal labour and facilitate automated production of cast and shaped bars of wide variety.

Yet further object of the present invention is to provide a system and method of continuous casting for product such as soap/detergents and the like, which favour achieving various shapes of bars by mere replacement of a mould unit in the system thereby imparting greater flexibility and convenience of continuous casting of such products.

Another object of the present invention is directed to provide a system and method of continuous casting of soaps/ detergents which avoid wastage and need for recycling and favour cost-effective continuous on-line production of shaped bars/articles.

Yet further object of the present invention is to provide a system and method for manufacturing cast products continuously which would enable selective incorporation of colour/benefit/ aesthetic agents into the product formed at desired levels and/or at desired locations/dispersion without disturbing the continuous production, thereby overcoming limitations in adding such benefit/aesthetic agents in the conventional casting process including batch or the semi-continuous processes presently available.

Yet another object of the present invention is to provide a system and method for continuous casting of melt-cast formulations in moulds while ensuring product exit from the mould in the horizontal direction, thereby enabling simple and effective downstream operations like shaping, stamping and cutting, which are preferably carried out on surfaces in the horizontal direction.

Summary of the Invention Thus, according to one aspect of the present invention there is provided a system for continuous casting of melt- cast products such as soaps, detergents and the like, comprising: i. a substantially horizontal or inclined mould unit to favour solidification/casting of the melt-cast composition during its traverse through said mould

unit, said mould unit being operatively connected at its inlet end to a supply source of the melt-cast composition ; ii. means for controlling the temperature of the melt-cast composition in the mould unit to achieve the desired solidification and shaping during traverse of said composition from the inlet end of said mould towards the outlet end thereof, said outlet end being adapted to eject the formed cast product; and iii. means for providing a resistance to flow of the melt- cast composition to ensure uniform filling up of the said composition, substantially free of air pockets, in the mould during the startup of the said system.

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

Preferably, the system of the invention comprises: i. a horizontally disposed mould unit, said mould unit being operatively connected at its inlet end to a supply source for the melt-cast composition; ii. means for controlling the temperature in the mould unit to achieve the desired cooling comprising a cooling jacket located on the mould and having means for continuous supply of coolant there-through to facilitate on-line cooling, solidification and shaping of the melt-cast composition during its traverse from the inlet end of the mould to the outlet end, and iii. means for providing a resistance to flow of the melt- cast composition to ensure uniform fill-up of the said

composition in the mould, substantially free of air- pockets during the startup of the said system.

It is particularly preferred that the melt-cast composition is not subjected to high thermal shocks, especially at the inlet end of the mould. This is preferably achieved by ensuring a low and controlled thermal gradient on the melt- cast composition during its traverse from the inlet to the outlet end of the mould.

In accordance with a further preferred aspect of the present invention, the means for controlling the temperature of the melt-cast composition in the mould such as the cooling jacket is adapted so as to produce a selective temperature gradient or distinct temperature zones through which the composition is allowed to traverse in the mould. AS a result, selective temperature control of melt-cast composition is facilitated so as to achieve said solidification and shaping based upon the constitution of the soap formulation.

Additionally, in order to facilitate the release of the formed product while exiting from the mould, a heating zone is preferably provided near the exit of the jacketed mould/caster to improve the slip of the bar and its throughput.

The operative connections of the mould in the system can be selectively provided to facilitate replacement of the mould by a different one depending upon the desired cross-section of the cast product.

In the above preferred system of the invention, the jacketed mould selectively includes means for selective injection of benefit/aesthetic agents in the soap formulation during the solidification/shaping process while it traverses the mould unit which cannot be achieved in case of any of the known batch as well as the conventional slip casting systems. Importantly, the possibility of varied temperature gradient in the jacketed mould and such provision for injection of benefit/aesthetic agents together facilitate providing even in case of continuous casting, injection of any secondary material into the main bar while keeping it segregated. 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.

Importantly, the system of the present invention effectively provides for the first time, by way of a continuous moulding system, a mechanism which would favour solidification and shaping of the soap during its traverse in the selective mould unit advantageously utilizing the relative flow between the melt and mould surface. This clearly deviates from the conventional attempt to either mechanize mould filling and/or release mechanism or using flexible moulds to allow setting of material in the mould to be cut off with the mould material .

The means for providing a resistance to flow of the melt to ensure uniform fill-up of the melt in the mould, substantially free of air-pockets, during the startup of the system, is preferably achieved by filling a part of the

mould towards the outlet end of the mould with the solidified composition. Alternately, any mechanical means for example a piston means or a plug means having a frictional resistance along the internal walls of the mould similar to the resistance experienced by the solidified composition may be provided during the startup stage along a length at the outlet end of the mould. The length along which the resistance to flow is provided, closer to the outlet end of the mould, is preferably equal to or greater more than the length over which the cast composition has substantially solidified during the steady - state operation.

In accordance with another aspect of the present invention there is provided a method for continuous casting of melt- cast compositions such as soaps, detergents and the like, comprising: (i) supplying a molten melt-cast composition through a substantially horizontal or inclined mould unit having temperature control means from the inlet end and allowing the composition to traverse towards the outlet end in the mould while providing a resistance to flow of the melt-cast composition during the startup of the process and (ii) controlling the mould temperature to thereby favour solidification and shaping of the composition into cast product in the mould which cast product ejects from the outlet end of the mould unit.

In accordance with the preferred aspect of the present invention, in the above method for continuous casting of melt-cast products such as soaps, detergents and the like

the mould unit temperature is controlled by regulating the means for controlling the temperature in the mould unit to achieve the desired casting. In particular in case of a jacketed mould having means for continuous supply of coolant there-through, the coolant temperature and/or its path can be regulated to facilitate on-line differential cooling to favour solidification and shaping based on the type of melt composition.

Advantageously, in the above process of the invention, the continuous production of cast bars is achieved by way of controlled filling of the soap melt in the substantially horizontal or inclined mould. Such a method that provides for a resistance to flow of the melt at the start-up of the process was found to take care of any problems of air pockets and non-uniform filling.

As mentioned above, by way of the above method it is possible to selectively regulate the temperature in the cooling jacket and to provide for a selective temperature gradient during the cooling of the melt to achieve the cast. The zone of the jacketed mould just adjacent the exit/outlet of the formed bars can be selectively heated by a heating mechanism to facilitate the non-stick and easy throughput of the bars.

As and when desired the cross section of the mould can be selectively changed by simple change over of the releasable secured mould to obtain shaped bars of desired cross section through 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 wastage's and recycling of wastes) and ensures production of shaped bars repeatedly and continuously avoiding uneven bar and/or recycling of the product to attain uniformity in manufacture.

Thus the above method of on-line continuous generation of bars would facilitate, controlling the temperature gradient during the cooling of the melt during the casting process thereby facilitate maintaining desired forms and constitution of the product. Moreover, by way of a possible selective injection mechanism, benefit/aesthetic agents or soap of different composition/colour for example colouring agents, slurry to provide stripes and/or benefit agents can be introduced during the casting process in the mould unit which is never possible in case of batch processes or in 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 including soap 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 method of the invention, different products can be cast such as a soap, detergent, deodorant 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 melt-cast 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 include saturated fatty acid soap, detergent actives and possibly upto 60% water with or without other additives and benefit agents.

The detergent actives suitable for use in the invention 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 benefit agents/additives and liquid skin benefit materials such as anti-aging compounds, emollients, moisturizers, and sunscreens. Solubilisers as suitable additives for use in the detergent composition include monohydric and polyhydric alcohols such as propylene glycol, sorbitol, and glycerin.

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 to 90 ⁰ C.

Brief Description Of The Drawings

The details of invention, its objects and advantages are explained hereunder in greater detail in relation to non- limiting accompanying Figure 1 which is a schematic illustration of the system for the continuous on-line production of soap/detergent bars in accordance with the present invention.

As shown in figure 1, the system for such continuous casting in accordance with the present invention basically involves a jacketed mould (1) which is covered by the cooling jacket (2) as a tube in tube arrangement. The cooling jacket, which surrounds the mould, is provided with cooling means such as the coolant entry (3) and the coolant exit (4) . The coolant can be pumped co-currently or counter currently or in cross-flow. The mould (1) as shown in the figure is preferably and selectively horizontally disposed to facilitate a horizontal feed of the soap melt from the inlet end of the mould for the continuous casting. To facilitate such feeding of the mould from the inlet end for the casting process, the soap melt is metered into the mould (1) through the inlet end by operative connection of the inlet (5) of the mould to the soap melt source (6) through a metering pump (7) . In accordance with a preferred aspect of the invention, multiple parallel tubes are used, either with individual cooling jackets or a bank of tubes can be cooled using an

outer shell as in a multi-tube heat exchanger. The tubes are preferably in rectangular or triangular pitch. An appropriate multi-head metering pump or individual pumps for each tube may be used.

Advantageously, in accordance with the preferred aspect of the system of the invention, the moulding jacket is adapted to facilitate a desired temperature gradient for the soap melt during its traverse from the inlet end of the mould and until it exits as the formed bar from the outlet. For this purpose, effective temperature control gadgets can be provided which can facilitate attaining such temperature gradient depending upon the soap formulation to be formed.

The system can also include injection means (8) selectively disposed in relation to the mould to favour selective injection of colouring/benefit/aesthetic agents or even soap of different composition/colour in the soap during its traverse through the mould unit. Importantly, the- selective provision of temperature gradient and the disposition of the injection means would favour flexibility in obtaining on-line continuous production of shaped bars with varied constitution, structure, characteristic and appearance.

The method of on-line production of such shaped bars involving the above system is simple and continuous. For the convenience of start up for effective uniform filling of the mould unit (1) with the liquid melt, a substantial length of the mould (e.g. 30 to 50%) of the mould unit at the outlet end is filled with the solidified soap composition (9) . To carry out the method, the soap melt

through the metering pump is continuously fed from the inlet end of the mould unit. Thereafter, the soap melt is forced through the mould unit (1) and in the process the same is selectively cooled to the desired extent and at desired stages during its traverse through the mould to facilitate solidification and shaping maintaining the desired constitution and character of the formed bar. Advantageously, as indicated above, depending upon the soap composition and the characteristics/appearance desired various colouring/benefit/ aesthetic agents could be introduced by injection into the soap during its motion in the mould. Finally, the formed bars exit as cast bars (10) from the outlet of the mould.

Importantly, the above system and method of the invention advantageously provide for a continuous casting for soap/detergent bars and the like wherein the casting of the formulation i.e. the solidification and shaping is achieved during the traverse of the formulation in a stationery mould. This makes for advantageous use of the system of continuous moulding where there is a relative flow between the liquid and the mould material .

Moreover, the temperature gradient in the cooling jacket and the possibility of injection of colour/benefit/aesthetic agents during the moulding which are not possible when using either the batch process or the continuous sleeve casting process, can be attained by way of the present invention. As a result, considerable flexibility in manufacture as well as the possibility of preparing a wide variety of formulations can be obtained when using the continuous cast route of the present

invention, while it can be ensured that the desired throughput is achieved.

The horizontal or inclined mould allows the system of the invention to be more convenient and practical, especially when using a bank of moulds with different geometric and spatial layouts.

Cutting and conveying of the solidified bars produced by the system of the invention can be carried out by conveying them in a direction which is different from the direction of the outlet of the mould e.g. in a direction perpendicular to the bar outlet from the mould.

The invention will now be demonstrated with the help of the following non-limiting examples.

Example-1

Molten soap was prepared in a jacketed vessel heated using hot water/steam, as shown in Figure-1. A batch of 30 kg soap was prepared. A 1.5 meter long horizontal mould of circular cross-section and of 48 mm diameter was provided with 4 stage cooling jackets each of about 30 cm long each. The casting operation was started by filling the mould over 0.5 meter towards the outlet of the mould with solidified soap composition. The soap melt was pumped through the mould using a gear pump. Hot water of 55°C was used in the 1 ^st cooling jacket, water of 25°C was used in the intermediate cooling jackets, and chilled water of 10 ⁰ C was used in the final jacket near the outlet. Solid soap bars with acceptable properties were cast out continuously at a rate of ~7 kg/hr.

Example-2

An experiment was carried out as per Example - 1 except that -55 kg molten soap was cast. A 3.6 meter long horizontal mould of circular cross-section of 48 mm diameter was provided with 5 stage cooling jackets. Solid soap bars with acceptable properties were cast out continuously at a rate of 18-21 kg/hr.

Example-3 An experiment was carried out as per Example - 1 except that 100 kg soap was used. A 6 meter long horizontal mould of circular cross-section of 48 mm diameter was provided with 9 cooling jackets. Solid soap bars with acceptable properties were cast out continuously at a rate of around 35 kg/hr.