The invention relates to a method of cutting or shaping cosmetic articles using a pressurised fluid.

Cosmetic articles often have fanciful shapes. The articles are generally sold in the form of individual pieces, e.g. detergent bars and deodorant sticks. The individual pieces are either made in that form itself by moulding or other suitable processes, or such pieces are cut or stamped from a larger piece.

Cosmetic articles such as detergent bars and deodorant sticks can be termed as deformable plastic articles because they generally deform upon application of pressure. The extent of deformation can be measured by some known methods. In a more widely used method, the "penetration value" is measured. This value indicates hardness of the article.

Conventional methods for shaping and cutting cosmetic articles include the use of blades and wires. Wires are used to limited extent because apparently the throughput offered by this method is very low. US 2988774A (Lever Brothers, 1961 ) discloses how a wire is used. More recent methods of cutting or shaping include the use of lasers.

One of the limitations of conventional methods and lasers is the difficulty to get sharp cuts. A disadvantage is that the finished articles are often left with deformed surfaces having striations, indentation marks and other visible defects thereon. Such an article having deformed surface may not be acceptable to consumers. This means that probability of articles being rejected at the quality control stage is high. Some newer methods of cutting or shaping detergent bars can be found in patent applications. JP 2006273975 A (Ishikawa Masahide) discloses use of laser beams on a transparent or semitransparent soap. The soap is covered with a smooth film which transmits the laser beam so as to cause gas-explosion of remaining moisture in the soap to form hollows and to draw lines and drawings with the hollows.

It is known that a pressurized fluid can be used for cutting or shaping articles. The method involves focused application of a fluid onto the article. Details of a suitable device can be found in e.g. US 2008032610A1 (KMT Waterjet Systems Inc, 2008). Generally a fluid jet or "water jet" cutting machine includes an intensifier or similar device for pressurizing the fluid (e.g., water) and a cutting head fluidly connected with the fluid intensifier and configured to direct a jet of high pressure fluid or fluid-abrasive mixture onto an object. A cutting head typically includes a nozzle fluidly connected with the intensifier, an orifice member fluidly coupled with the nozzle and formed to restrict the flow and increase the velocity thereof so as to form a fluid jet, and a wear insert connected with a body and configured to mix the fluid jet with abrasive material if needed. However, limited information is available on the use of pressurized fluid jet for cutting cosmetic articles, particularly detergent products.

EP 1418224 B1 (Unilever) discloses a biphasic laundry tablet which has two distinct regions; a first smooth region made of extruded detergent composition and a second particulate region made of compacted particulate detergent composition. The smooth region is obtained by cutting smaller pieces from a strand or a log of extruded detergent composition by use of inter-alia a water jet so as to smoother edges and better finish. Broad ranges have been disclosed for two variables; i.e. for size of the orifice (nozzle) and pressure of water.

The pressure ranges from 10,000 psi (689 bar) to 100,000 psi (6894 bar) and the nozzle sizes range from 0.025 mm to 0.25 mm. Soap and detergent formulations are tailored to suit the intended application. For example, composition and structure of a soap bar for personal wash is different from a laundry bar, although each can be termed a cleansing product or a detergent composition. For example, a cast melt soap bar has a coagel crystalline structure and a milled and plodded soap bar contains lamellar phases. Therefore the broad process parameters disclosed in EP 1418224 B1 are not suited for implementation of this technology on a factory scale without further inventive efforts. JP-02/135,300 A (SHISEIDO CO LTD) and JP-62/059,699A (MITSUI

PETROCHEMICAL IND) each discloses use of a water jet for creating a patterned cavity in a bar of soap in which letters or pieces of other soaps can be inserted. JP'699 does not term any process parameter as being critical.

However, according to the broadly disclosed conditions in JP'300, diameter of the nozzle(s) of the water jet is from 0.1 mm to 0.25 mm, the pressure of water jet is from 2400 to 3000 bar and the punching rate, or as better known in the area of water jet machines, the cutting speed at which nozzles are made to move over surface of the bar is from 100 to 70 mm/minute. A drawback of the process disclosed in JP'300 is that the significantly lower cutting speed may not always lead to bars with good surface finish and incidences of striations or indentations marks are very likely.

We have determined the cutting speed appropriate for cosmetic articles having hardness (penetrometer) in the range of 0 mm to 120 mm so as to get a smoother finish.

Accordingly in a first aspect is disclosed a method of cutting a cosmetic article including a step of bringing the article in contact with a jet of pressurised fluid sprayed from at least one nozzle having an orifice of cross-sectional area from 4.9X10 ^"4 mm ² to 750x10 ^"4 mm ² , where hardness of the article expressed as penetration value is 0 mm to 120 mm, wherein, a relative motion of 150 mm/minute to 1500 mm/minute is provided between said article and said nozzle while the article is cut.

The invention will now be explained in detail.

The method disclosed herein relates to cutting a cosmetic article, and the method includes a step of bringing the cosmetic article in contact with a jet of pressurised fluid. The term "cutting" as used herein means and includes shaping, etching, and trimming, decorating or creating contours or patterns therein so as to arrive at a second shape starting from a first shape where the second shape differs from the first. The term "cutting" also includes the other, more widely applicable meaning of severing or slicing which when used in the context of the present application means cutting or slicing a larger piece of a cosmetic article into one or more smaller pieces.

The method disclosed herein is applicable to cosmetic articles having hardness expressed as penetration value in the range of 0 mm to 35 mm. Preferred, but non-limiting examples of such cosmetic articles include a detergent product, a lipstick or a deodorant product. The method more particularly applies to detergent products.

In the case of detergent products, it is particularly preferred that the detergent product is in the form of a bar or billet. Detergent products are available for variety of uses. Personal washing and laundry are two well-known applications. Products meant for personal washing are generally and popularly known as soaps and are generally sold in the form of bars. Bars of soap contain about 60 to 80 wt% alkali metal salts of fatty acids. Such bars are manufactured by milling, plodding and stamping a semi-solid mass of soap (i.e. mixture of alkali metal salts of fatty acids) and other ingredients. Soap bars can also be made by melt-cast process. Usually transparent bars are made by this process.

A third category is non-soap detergent bars, often known as "syndet" bars or NSD bars, in which either there is no soap or only a small amount thereof, because the active component is mostly or wholly a synthetic non-soap surfactant. Generally such bars also contain a substantial amount of fillers such as starch, clay and talc. While such bars are generally used for cleaning fabrics, a sub-category is also known which is exclusively meant for cleaning dishes. These are called dishwash bars which are harder than fabric cleaning bars.

In the preparation of melt-cast soaps, it is customary to first prepare a long billet which is cut or sliced into smaller individual bars. Process for making such billets by continuous casting has been described in US201 1/278429A1 and WO2006/1 19863A1 (Unilever).

On the other hand, laundry bars and hand dish wash bars are made by cutting smaller bars from continuously extruding dough containing a blend of

ingredients. This is done in a machine called as extruder. A description of a typical extruder can be found in US4193752A (Unilever, 1980). Milled and plodded personal wash bars are also made (cut) by the same process, but there is an additional step of stamping which lends the bar a distinctive shape.

Usually in the case of melt-cast soaps, the step of cutting the billet into smaller bars is largely dependent on manual skill. A long billet of the cast detergent is pushed by an operator up to a bumper where a blade accelerates downward and cuts the billet into smaller pack-sized bars. The pressure applied by the operator while pushing the billet dictates the weight of the bars. In such cases, it is quite possible that there is wide variation in the weight of bars. This often leads to problems with quality of the bars, especially of varying bar weights which could present technical problems at the stage of stamping. Usually detergent bars are stamped with a logo which includes a trademark. If too small a bar is cut then it is not possible to stamp the logo completely. On the other hand, too large a bar usually jams the stamping moulds. This leads to an appreciable rejection rate which can be as high as 5 %. This affects overall capacity of the plant in a significant manner.

The method is particularly applicable for cutting a cosmetic article in the form of a detergent composition as exemplified by detergent bars or billets. Other equivalent acts such as shaping have been described earlier. The terms soap and detergent are generally used interchangeably and have so been used throughout this disclosure. It is preferred that composition is in the form of a billet or a bar of detergent. Description and formulation of various types of soap or detergent compositions such melt-cast soap bar, milled and plodded soap bars, aerated soap bars, soap-based laundry bars, non-soap based laundry bars (NSD bars) and hand dish wash bars can be easily found in literature.

Bars made by extrusion typically have a characteristic anisotropic internal structure with respect to the alignment of crystals as well as the overall macro- structure. In contrast, melt-cast bars have a predominantly isotropic structure because crystallization occurs during quiescent cooling and thus the alignment of crystals is minimal and there is no candle structure.

Melt cast soaps are characterized by lower soap content (i.e. mixture of alkali metal salts of fatty acids) and higher polyol content which gives such

compositions a distinctive transparent appearance. Therefore, a highly smooth and defect-free surface finish is particularly desirable for such bars. Therefore any method employed to cut the bars must provide a smooth surface with minimal indentations or striation marks. Generally such soap compositions are harder than milled and plodded bars. Deodorant products are more popular in their "stick form", which is technically a gelled product. It is preferred that the deodorant product is a gelled product. More preferably this gelled product is a deodorant stick. This product is often characterized on the basis of opacity or clarity. The formulation includes a blend of waxy materials of different melting point, whereas clear products are commonly structured by a gelling agent which in the presence of other composition components, in translucent or transparent products.

Deodorant sticks are commonly formulated as anhydrous or low water content compositions using a blend of waxy materials having different melting points. A typical deodorant stick includes from 10 to 75% by weight water; one or more gelling agents such as an alkali metal salt of a fatty acid (herein also referred to as a "soap"), preferably a C12 to C2 ₄ fatty acid, more preferably a C16 to C22 fatty acid, with sodium and potassium salts; one or more co-gellants such as polyethylene oxide-polypropylene oxide block copolymers; waxes and other organic or inorganic opacifying materials; a clarifying agent in amount up to 2 wt% for maintaining the clarity of the gelled composition which is preferably a basic amine selected from amino alkanols having from 2 to 6 hydroxyl groups; 10 to about 80 wt % emollient and one or more deodorant actives. Additional ingredients include preservatives, colorants, sunscreen, chelating agents, pH adjusters, viscosity modifiers, and fragrances and the total amount of such additional ingredients is from 0.01 to 5% by weight. Further description of a deodorant stick may be found in US2010158841 A1 (Unilever). An essential element of all lipsticks is a lipophilic material from 10 to about 99 wt% such as hydrocarbon oils, fatty acid esters, fatty alcohols and mixtures thereof and including waxes such as candelilla, beeswax, carnauba,

spermaceti, montan, ozokerite, ceresin, paraffin, modified beeswax, bayberry wax, castor wax, microcrystal line waxes and mixtures thereof; an antibacterial agent; small amount of water; one or more antioxidants; skin protection agents; polysaccharides such as sorbitol; emulsifiers such as phospholipids; colorants such as FD & C approved dyes and sunscreens. Further details of lipsticks may be found in WO 0062739A1 (Unilever).

In terms of the method of cutting, cosmetic articles such as bars of soap and detergent products are made on an industrial scale by using machines.

However, till date, some operations still rely on manual skill. One such example is the use of manual labour for slicing a billet of cast-melt detergent product into smaller bars which has already been described earlier. A problem with manual cutting is that the process does not produce high quality sharp cuts because the edges of the bars are often damaged by the

accelerating blade. This not only limits the use of the cutting process but it also severely limits flexibility of the cutting arrangements. For example, a limitation of blades is that billets with a curved or other nonlinear profile cannot be cut properly to get soap bars having curves or contours.

In the process disclosed herein, the cutting is done by bringing the article, such as detergent product e.g. a detergent bar, in contact with a jet of pressurised fluid which is sprayed from at least one nozzle having an orifice of cross- sectional area from 4.9X10 ^"4 mm ² to 750x10 ^"4 mm ² .

Novelty of the disclosed method resides in providing relative motion of 150 mm/minute to 1500 mm/minute between the article and the nozzle while the article is cut.

This relative movement can be achieved in at least two possible ways.

In a first way, the cosmetic article intended to be cut is kept fixed while the nozzles are made to move over the surface of the article. This method is particularly preferred when an intricate pattern or design needs to be cut starting from a bar or tablet of a detergent product. This method is also particularly useful in cases where the cosmetic article is in the form of a billet of a melt-cast soap or detergent product or a log of extruded soap or detergent product which is to be continuously cut (severed) into a number of smaller bars of ready-to-use size. In such cases, the billet or log is preferably secured or held tightly while the nozzle or nozzles are made to move over it.

In a second way, the cosmetic article is made to move while the nozzles remain stationary.

In order to get a continuous and sharp cut, it is preferred that the contact of the jet of pressurised fluid with surface of the cosmetic article is also continuous. Broadly the relative motion (also called cutting speed) is 150 mm/minute to 1500 mm/minute, preferably it is 250 mm/minute to 900 mm/minute. In a most preferred embodiment of the method, a relative motion of 250 mm/minute to 600 mm/minute is provided.

At the lower end of the disclosed range relative motion believed to be is more contact time between the fluid and the cosmetic article which is likely to affect the surface finish e.g. especially of detergent bars.

Further preference for the relative motion is linked to size of the nozzle or nozzles. It is preferred that the selected fluid is an aqueous liquid, a non-aqueous liquid or a gas. Exemplary gases include air, oxygen, nitrogen and carbon-dioxide. Exemplary aqueous liquids include water and brine. Exemplary non-aqueous liquids include ethanol and propylene glycol. It is particularly preferred that the fluid is an aqueous liquid. An optimal aqueous liquid is plain water.

It is preferred that pressure of the fluid jet is 600 bar to 7000 bar. In a more preferred method, this pressure is 1000 bar to 5000 bars. In further preferred method, the pressure is 1500 bar to 4000 bar. The pressure is created because the fluid is forced through a nozzle which has an orifice of small cross-sectional area. This creates a very thin beam of pressurized fluid travelling almost at the speed of sound.

It is believed that cutting action of high pressure jet is due to erosion of the surface of the cosmetic article, especially in the case of a detergent compound such as a bar of detergent. The jet of pressurised fluid is sprayed from at least one nozzle having an orifice of cross-sectional area from 4.9X10 ^"4 mm ² to 700x10 ^"4 mm ² . This definition by way of cross-sectional area of the nozzle makes it clear that there is no preference for any particular shape of the orifice. However, most known orifices are circular, square, triangular or rectangular. It is preferred that the orifice is circular in shape. While the apparatus can include just a single nozzle (which has an orifice), it is preferred that the jet of pressurised fluid is sprayed simultaneously from plurality of nozzles, each having its own orifice. In such a case, it is preferred that cross section of each orifice is identical, more

preferably circular. Thus preferably, when the jet of pressurised fluid is sprayed from plurality of nozzles, each nozzle has an orifice of cross-sectional area from 4.9X10 ^"4 mm ² to 750x10 ^"4 mm ² .

It is preferred that the cross-sectional area of the orifice or orifices of nozzle(s) is 1 10X10 ^"4 mm ² to 750x10 ^"4 mm ² . However, most preferred cross-sectional area is 1 10X10 ^"4 mm ² to 550x10 ^"4 mm ² . In the case of circular orifice, the disclosed ranges would approximately equate to a broad range (orifice diameter) of 0.025 mm to 0.25 mm, more preferred range of 0.12 mm to 0.25 mm and most preferred range of 0.12 mm to 0.17 mm. The orifice of the nozzles should not be too large as it will likely affect

throughput of the method but at the same time it must not be so small that a cut cannot be performed fast enough which also implies lower throughput. Orifice(s) having the most preferred cross-sectional area is found to provide improvement in throughput by more than a factor of two as compared to that provided by an orifice whose cross sectional area is 700x10 ^"4 mm ² (i.e. where the orifice is a circle with a diameter of approximately 0.25 mm). Without further wishing to be bound by theory, it is believed to be due to relationship of pressure of the fluid with its flow rate.

Surprisingly it has been found that an orifice having cross-sectional area in the most preferred range minimizes wastage of material as particularly exemplified by a detergent product in the form of a billet of melt cast detergent product. This technical benefit is particularly important when pressurized fluid is used for cutting (severing) a larger piece of detergent composition into smaller bars where even a 5 % reduction in wastage becomes immensely significant considering that factories typically produce thousands of tonnes of bars in a day. In normal course, such wasted material is usually recycled by mixing it with subsequent batches, but this also presents its own set of technical problems of re-processing. Therefore having minimal wastage is an ideal situation.

It is also observed that orifices of larger cross-sectional area tend to leave more scratches, indentations or other surface defects, incidences of which were surprisingly found to be significantly lower in cases where the jet was sprayed from an orifice whose cross-sectional area is within the most preferred range as disclosed earlier. A further technical benefit of having orifice or orifices of smaller size (lower cross-sectional area) as compared to larger ones is that it allows for splitting the cutting heads into multiple units so that more number of articles could be cut simultaneously. In other words, instead of using one nozzle having a circular orifice of diameter of 0.25 mm for cutting one article at a time; using three separate nozzles each with a circular orifice of diameter 0.12 mm allows for simultaneously cutting or slicing, e.g. three billets of a detergent composition or for e.g. shaping three detergent bars under the same applied pressure. Therefore, yet another technical benefit of using nozzles with smaller orifices is that it provides greater throughput and it makes the method economically more viable.

The distance between the nozzle and the article also plays an important role. It is preferred that a distance of 2 mm to 8 mm is maintained between tip of the nozzle or where there are multiple nozzles between tip of each nozzle and the detergent composition which is to be cut. It is preferred the distance is 2 mm to 6 mm and further more preferably 3 mm to 5 mm. This distance can be varied if required during cutting or shaping but it is preferred that the distance is kept constant during the course of the relative motion while the article is being cut. No special measures are necessary to maintain a constant distance In the case of simple two-dimensional article as exemplified by a detergent bar which does not have any contoured surface such as a concave, convex, saddled or profiled surface. However where a bar has a contoured profile or any other non-linear shape, then in order to maintain a constant distance, either the article (or the platform on which it is kept) or the nozzles need to be raised or lowered depending on whether the surface of the article has a raised profile or a depressed profile. In other words, it is preferred that the nozzle or nozzles follow the profile of the article, such as a billet or bar of detergent product while it is being cut into individual bars or while it is being shaped. Without wishing to be bound by theory it is believed that this maximizes the surface and edge quality for each particular cutting speed and nozzle size.

If the distance is less than 2 mm, the pressure is likely to be too high to get a good quality surface or edge finish. On the other hand, distances beyond 8 mm could cause a greater degree of splashing of the fluid as it then becomes difficult to keep a straight jet of the fluid. This could eventually have an adverse impact on the capacity of the jet to provide precise cuts.

For the preferred cross-sectional areas as explained earlier, the corresponding preference for relative movement is explained in table 1 .

Table 1

It is preferred that thickness of the detergent composition is from 10 mm to 60 mm, more preferably 10 mm to 50 mm and most preferably 10 mm to 40 mm. This thickness indicates the thickness of the cosmetic article which is to be cut. The thickness could be uniform or an article could have varying thickness, especially in the case of contoured bars or billets of detergent products.

Cosmetic articles such as deodorant sticks and detergent bars have a defined range of hardness. In the case of soaps and detergent products, especially of bars, it is an important measure of quality control. The lesser the penetration value, the higher is the hardness. Hardness of a cosmetic article has a direct relation with its formulation. Another point about hardness is that it tends to vary from time to time. For example, freshly made detergent bars are softer.

Therefore their hardness (as expressed in terms of penetration value) is lower. However as time progresses, the bars generally tend to lose moisture or other volatile components which makes the bars harder. Therefore the penetration value is seen to drop (reduce) over a period of time. The disclosed method is applicable for cosmetic articles having hardness (expressed as penetration value) is in the range of 0 mm to 120 mm. A preferred range is 0 mm to 80 mm. More preferred range is 0 mm to 60 mm and the most preferred range is 0 mm to 35 mm. The broad range applies to most cosmetic articles such as detergent bars, deodorant sticks and lipsticks. The preferred range of 0 mm to 60 mm and that of 0 mm to 80 mm applies particularly to detergent bars and deosticks. The most preferred range of 0 mm to 35 mm applies to detergent bars. Usually cast melt detergent bars and laundry bars are harder than milled and plodded detergent bars usually meant for personal wash. Method of determining penetration value

This method of measuring hardness of cosmetic articles such as detergent bars and deodorant sticks, which is conveniently carried out at room temperature (typically 25°C), is performed by first placing the bar on a flat sturdy surface. A penetrometer is used for this purpose of determining hardness. This meter is a long cylindrical instrument containing a gauge at the top (for reading the measurement in millimeters and hundredth of millimeters) and in the middle a release level which, when released, releases a penetrating cone from the base. For use, the penetrometer is grasped firmly in one hand and its base is placed on the flat surface. When steady, the release lever is pushed in and then to the left in a single motion. This allows the pointed penetration cone to drop into the surface of the bar. The instrument is held steady in place for two minutes. After lapse of two minutes, the gauges on the top of the instrument are read. This reading is the number of millimeters that the tip of the cone has penetrated after two minutes. For example, if the small gauge reads 4 and the large gauge reads 0.27, it means that the cone has penetrated 4.27 mm.

The penetrometer may be clamped in position before pressing the release lever in order to keep the instrument steady.

Typical penetration values for various types of detergent bars (within four hours of manufacture) are shown in Table 2. Also shown are the typical values after 3 months of storage at room temperature. Therefore, the difference in penetration values can be easily appreciated. Also included are values for a typical deodorant product (stick). Table 2

Further details and benefits of the disclosed method will now be explained with the help of non-limiting examples. EXAMPLES

Examplel : Effect of size of nozzle orifice (cross-sectional area) and variable relative movement on surface finish of a cosmetic article (detergent bar) cut from billets of the corresponding melt-cast composition

Billets of melt-cast detergent composition were made from the composition as described in Table 3 by the normal procedure.

Table 3 ingredient wt%

sodium soap 35.0

propylene glycol 7.0

Polyethylene glycol 200 5.0

glycerol 21.0

sodium chloride 1 .0

sodium lauryl sulphate 7.0

perfume 1 .0

water 22

other minor ingredients to 100 In this test, nozzles having orifices of varying cross-sectional area were tried. Relative movement was provided between the nozzles and the billets by keeping the billets stationary and moving the nozzles to observed the effect of the changes on the surface finish of the bars. In order to find out the effects precisely, certain parameters were fixed. These were as follows:

Fixed parameters:

• Pressure of water - 3600 bar

· Distance between tip of the nozzle and surface of the billet - fixed at 5 mm

• Thickness of detergent (billet) - 15 mm

• Width of individual detergent bars cut from the billet - 15 mm

• Number of nozzles used - 1

• Penetration value of the detergent product - 17 mm

The billet was kept on wooden ply with 2 mm slots at 15 mm interval for draining the water splashed from the jet. The sample was held between the two solid plies. Visual observations are presented in the Tables 4, 5 and 6. Table 4: cross-sectional area of the orifice 1 10X10 ^"4 mm ²

1 1 650 acceptable

more scratch marks - not

12 700

acceptable

more scratch marks - not

13 800

acceptable

more scratch marks - not

14 900

acceptable

Table 5: cross-sectional area of the orifice 550X10 ^"4 mm ²

Table 6: cross-sectional area of the orifice 750x10 ^"4 mm ²

Example 2: Effect of nozzle size on average weight of bars that were cut

The object of this experiment was to determine the effect of cross-sectional area of the orifice of the nozzle on the weight of bars cut from the billet. Using this data, the average variation in the weight of bars was calculated which was eventually used to calculate the standard deviation. All the other fixed parameters have already been described earlier in the context of Example 1 . Table 7

Data on standard deviation in Table 7 explains the preference for smaller orifices. As can be readily seen from the data herein, higher standard deviation in the average weight of bars in the case of nozzles of larger orifice also supports the previously described observation on wastage of material.

The disclosed examples illustrate how the disclosed method involving further optimized parameters provides detergent bars with smoother surface. The disclosed examples also illustrate how the method leads to lesser wastage of material.