Cleaning tablet

Abstract

The invention relates to a cleaning tablet having a compacted powder core of which at least part of the surface is covered by a stabilizing composition water soluble and having a melting temperature of between 40 and 100 °C. The cleaning tablet according to the invention, whose surface is covered with a stabilizing composition, prevents the powder from crumbling with a minimum amount of stabilizing composition. The stabilizing composition has penetrated the cleaning tablet, which is composed of compact powder, and has formed cohesive bonds with the powder particles, reinforcing the structure of the tablet and preventing crumbling that reinforce the structure of the tablet and prevent crumbling. The invention also relates to its manufacturing method using fine droplet spraying of the stabilizing composition onto at least one surface of the cleaning tablet.

Description

[0001] The present invention relates to a cleaning tablet, in particular solid cleaning tablets, and to the method of manufacturing them.

[0002] A cleaning tablet comprises a powder mix of cleaning agents with possibly carrier agents, which is compacted to form a block or a core. The specific composition of the powder mix depends on the application. It is designed to provide a pre-measured amount of compacted cleaning powder in an easy-to-use format. A cleaning tablet can have different shapes such as a parallelepiped, a cylinder, a diamond, a cone, a prism, a pyramid, a sphere, or any specific shape depending on the industry and / or the product and / or the release of the ingredients over time.

[0003] Examples of cleaning tablets include detergent tablets, dishwasher tablets, tablets to reconstitute detergent or cleaning solutions, toilet tablets, washing machine tablets, multi-purpose tablets, etc.

[0004] Generally, a process for manufacturing a cleaning tablet includes a step of formulation the powder composition, a step of granulation and / or compressing the powder to transform it into a solid product. After this step the surface of the tablet can be crumbly. A coating step can be implemented, where a coating composition is applied to the surface of the tablet, and an optionally drying step to remove excess liquid from the coating step, in order to form a solid protective shell around the tablet. Other intermediate or additional steps may be added, such as a tablet packaging step.

[0005] The coating composition must enable both good wetting and good fixing of the powder on the surface, while allowing the formation of a solid shell to protect the tablet from impact and moisture. The coating composition comprises one or more coating agents. Coating agents are compounds used to create a protective outer layer around the tablet. Coating agents can be polymers, waxes, gums, or other substances specifically formulated as required.

[0006] On one hand the coating compositions with the best wetting and powder fixation properties are polymers such as polyacrylate, or biopolymers such as starch. The coating composition is applied in an aqueous liquid phase to the surface of the tablet. The water is then evaporated during a drying step. However, this coating process has intrinsic defects. As the detergent tablet is formulated based on a water-soluble compound, the water present in the coating composition can interact with the tablet, either by solubilizing part of the tablet, or by triggering reactivity and instability between the tablet's most reactive chemical constituents. Also, after drying, the coatings obtained are generally very hygroscopic and therefore sensitive to humidity, making the tablet not very stable over time.

[0007] In addition, the use of these polymers or biopolymers requires a drying step. However, these compounds are very adhesive and stick to the tablet coating and conveying equipment, making cleaning under internal conditions very difficult and time consuming.

[0008] On another hand, the coating compositions that form the best protective shells are polymers or biopolymers or non-aqueous solid fats with a high melting temperature. The coating composition is heated and melted, then used by depositing it on the surface of the tablet by dipping, coating or spraying. The composition solidifies as it cools, forming a shell on the tablet. The coatings are generally thick but more protective against humidity and storage conditions. The drying step is not necessary, and the compounds are not very adhesive, facilitating the handling of the tablet. However, the quantity of coating composition used is high, the coating is less adhesive to the tablet, and parts of the coating can peel off the tablet (deformation of the tablet). Also, as the quantity of coating composition required is very high, it leaves residues in the manufacturing equipment. Usually, a cleaning step of the industrial equipment (chemical or mechanical) is added, impacting on the production schedule and costs.

[0009] Moreover, the above coating steps are time-consuming and slow down the overall production rate. Achieving a uniform coating layer on all tablets can also be a challenge. Non-uniform coating distribution can affect the stability and appearance of the tablet.

[0010] The applicant has therefore judged necessary to conceive a cleaning tablet which appearance and structure remain stable during manufacture and storage overcoming at least in part the problems deriving from the coatings described above and the associated methods.Solution of the invention

[0011] To this purpose, the invention relates to a cleaning tablet having a compacted powder core of which at least part of the surface is covered by a stabilizing composition, said stabilizing composition being water soluble and having a melting temperature of between 40 and 100 °C, and said stabilizing composition is sprayed onto the surface of the core in quantities ranging from 0.01 to 0.12 g / cm 3< of the tablet.

[0012] In the cleaning tablet according to the invention, whose surface is covered with a stabilizing composition, the powder forming the core is prevented from crumbling thanks to a stabilizing composition. This stabilizing composition forms cohesive bonds with the powder particles at the surface of the core, thereby reinforcing the structure of the tablet. Contrary to the known coatings which form thick layers over the tablet, the stabilized layer forms part of the tablet.

[0013] The compacted powder core comprises cleaning substances in the form of powder, as is well known to a person skilled in the art.

[0014] A stabilizing composition is a chemical substance or mix of substances whose purpose is to strengthen powder cohesion, prevent crumbling, and protect the surface against external influences, such as humidity. The stabilizing composition according to the invention is designed to penetrate the pores of a solid substance, such as the core of the cleaning tablet, thereby creating mechanical bonds with the particles on the surface of the tablet and / or in the compacted powder core. By penetrating the pores of the tablet, this composition promotes a stronger, more stable structure, contributing to mechanical strength and integrity of the tablet. The stabilizing composition, which unlike a coating, is not a simple layer on the surface of the tablet, but penetrates the compact powder core of the tablet and contributes to the stability of the tablet.

[0015] Unlike a coating, it penetrates the gaps and pores of the compressed core, allowing a partial filling of the porosity. This mechanism promotes cohesion between the powder particles, thus strengthening the mechanical stability of the tablet. The stabilizing composition can be considered as an internal consolidating agent. Preferably, the stabilizing composition is not a coating.

[0016] Thus, it contributes to its long-term physical stability. The stabilizing composition plays a crucial role in preserving the powder's original characteristics, limiting its interaction with adverse environmental conditions such as humidity, while promoting easy handling, safe storage, and efficient use of the cleaning tablet.

[0017] The stabilizing composition is water-soluble, meaning that upon use, when placed in an aqueous media, it will entirely solubilize.

[0018] The stabilizing composition can comprise a single substance or a mixture of substances. For example, the composition can comprise one stabilizing substance or a combination of stabilizing substances, such as polyethers. Examples of stabilizing substances suitable for the stabilizing composition of the invention are water soluble polyethers such as polyalkylether, for example poloxamer such as polyethylene glycols, polyethylene-propylene glycols; or alkyl polyether for example alkyl-polyethylene glycols, alkyl-polyethylene-polypropylene glycols; or alcohols alkoxylates for example alcohols ethoxylated, alcohols ethoxylated-propylated; or a mixture of at least two polyethers.

[0019] Preferably, the stabilizing composition comprises at least one polyether.

[0020] Preferably, the stabilizing composition comprises at least two polyethers.

[0021] Preferably, the stabilizing composition comprises at least one alcohol alkoxylate.

[0022] Preferably, the stabilizing composition comprises at least one polyethylene glycol.

[0023] Preferably, the stabilizing composition is composed of water-soluble polyethylene glycols based on natural plants. Example of such natural polyethylene glycols are PEG 1500, PEG 4000, PEG 6000 or a mixture of at least two polyethylene glycols. PEG 4000 is the most preferred polyethylene glycol.

[0024] Preferably, the stabilizing composition comprises a mixture of at least two polyethers.

[0025] Preferably, the stabilizing composition comprises a mixture of at least one polyether and at least one alcohol alkoxylate.

[0026] Preferably, the stabilizing composition is devoid of water and solvent. It may further comprise additives, processing aids, coloring agents or any other substance. Preferably however, the stabilizing substance(s) amount for at least 90% weight of the composition, preferably at least 95% of the composition. The stabilizing composition is also preferably devoid of water and / or devoid of solvent.

[0027] Preferably, the melting temperature of the stabilizing composition is from 40 to 100 °C, preferably from 40 to 90 °C, more preferably from 41 to 80°C, more preferably from 42 to 70°C, more preferably from 45 to 65°C.

[0028] The cleaning tablet can have different shapes such as a parallelepiped, a cylinder, a diamond, a cone, a prism, a pyramid, a sphere, an octahedron, an ellipsoid, or a specific shape depending on the industry and / or the product and / or the release of the ingredients over time. For instance, a parallelepiped cleaning tablet may have a length varying from 2 to 4 cm, a width varying from 1.5 to 3 cm and a height varying from 1 to 2 cm. The manufacturing method of the tablet of the invention is particularly flexible and can adapt to any shape. One aspect of the present invention is to minimize the quantity of stabilizing composition required, not only for economic reasons but also to facilitate the overall manufacturing process, equipment cleaning and improved tablet appearance. The quantity of stabilizing composition is minimized by the method of manufacture in the present invention using mist spraying technology.

[0029] The stabilizing composition can represent from 0.01 to 0.05 g / cm 3< of the tablet, or more preferably 0.02 to 0.04 g / cm 3< of the tablet even more preferably 0.02 g / cm 3< or less.

[0030] The invention also relates to the method of manufacturing a cleaning tablet according to the invention. The method comprises the steps of: ∘ the stabilizing composition according to the invention, is melted; ∘ the melted stabilizing composition is applied by mist spraying on at least part of the surface of the compacted powder core.

[0031] The stabilizing composition helps to protect the stability of the tablet and requires only a small quantity to fix the tablet's surface powder. Preferably, the stabilizing composition is sprayed on the surface of the core in amounts ranging from 0.01 to 0.12 g / cm 3< of the tablet, more preferably from 0.01 g to 0.05 g / cm 3< , the most preferred 0.02 g / cm 3< .

[0032] Mist spraying is a process consisting in dispersing a liquid in the form of fine droplets in the air. This process is used in various applications including chemical spraying, cooling, humidification, disinfection, agricultural spraying, etc. Mist spraying can be carried out using different known techniques such as pneumatic spraying, electrostatic spraying, thermal spraying, aerosol spraying. Mist spraying can produce a warm mist of finely atomized particles of stabilizing composition. Preferably, the mist spraying is obtained by a technology of atomized spray.

[0033] Generally, the melted stabilizing composition to be atomized is introduced into the spray nozzle through a feed channel. Through another channel, air is introduced into the spray nozzle. Air and liquid flows converge through the nozzle to a common outlet. When the liquid is exposed to the air pressure, it is broken into fine droplets. The air flow plays a crucial role in breaking up the liquid into small particles. Adequate air pressure is essential to effectively break up liquid into fine droplets. Preferably, the mist spraying uses an air pressure from 0.5 to 8 bars, more preferably from 0.5 to 4.0 bars.

[0034] The temperature of the compressed air can also influence the process. In order to obtain an adequate low viscosity and avoid precipitation of the melted stabilizing composition in the mist spraying equipment and air flow should be above the melting temperature of the stabilizing composition. Preferably, the mist spraying uses an air temperature from 50 to 110°C, more preferably from 60 to 100°C, more preferably from 65 to 95°C.

[0035] The flow rate of the melted stabilizing composition determines the amount of composition sprayed per unit of time. Preferably, the melted stabilizing composition pressure is set from 1.0 to 8.0 bars, more preferably from 1.0 to 4.0 bars.

[0036] Different types of air spray nozzles can be used, as long as they are compatible with the air pressure, liquid pressure and operating temperature of the present invention, such as those supplied by Spraying system co.

[0037] Preferably, the stabilizing composition is sprayed in the form of particles with a diameter of up to 300 µm, more preferably with a diameter of up to 200 µm, more preferably with a diameter of up to 100 µm, more preferably with a diameter less than 100 µm (i.e. 90% of the particles have a diameter having this value or below). The diameter of the particles can be measured using various methods well known to those skilled in the art, for example, by using a laser diffraction granulometer such as the Mastersizer from Malvern Panalytical.

[0038] Preferably, the mist spraying is carried out on at least one surface of the table, more preferably on at least 50% of the surface, at least on 60% of the surface, at least on 75% of the surface and more preferably on the total surface of the tablet.

[0039] As the stabilizing composition is devoid of water or solvent, the method of manufacturing the tablet according to the invention does not include a drying step requiring heat. Preferably, after the mist spraying step, a cooling step can be carried out to solidify the stabilizing composition, which can be active cooling (ventilation cooling, forced air cooling, etc) or passive cooling (ambient air cooling)

[0040] The cleaning tablet can be further packed in an individual packaging such as a plastic bag, paper fiber based bag, carton skillet, blister packaging, aluminum packaging or any material with is design to provide moisture protection properties.Detailed description of the invention

[0041] The invention will be better understood on reading the following description of embodiments of the invention, with reference to the figures where: Figure 1 shows a parallelepiped-shaped cleansing tablet according to the invention. Figure 2 illustrates the manufacturing process of the cleaning tablet of Figure 1, the top surface of which is covered with a stabilizing composition. Figure 3 is a cross-sectional view of a cleaning tablet according to the invention, where the top and bottom surfaces are covered with a stabilizing composition.

[0042] With reference to figure 1, a cleaning tablet 1 is a 6-sided rectangular parallelepiped comprising a core 2 of compacted powder, for example dishwashing powder. The top surface of the compacted powder core 2 is covered with a stabilizing composition 3.

[0043] The stabilizing composition 3 consists here of a pure bio-sourced polyethylene glycol. It has a molar mass of 4000 and a melting temperature from 54 to 58°C.

[0044] With reference to figure 2, to manufacture the tablet 1, the polyethylene glycol 3 is heated in a step A above its melting temperature, i.e. above 80°C to obtain a liquid form. The liquid obtained passes through an air atomization nozzle 4 (or high-pressure pneumatic spray nozzle) and a valve, as for example supplied by the company "Spraying system Co" in order to form a mist spray 5 of droplets of polyethylene glycol 3 which is oriented toward a compressed powder core 2. The air in the nozzle has here a temperature of 75°C and a pressure of 0.8 bar. The core 2 is passed under the nozzle at a speed of for example 6 m / min and the distance between the nozzle and the core surface is here for example 47 mm.

[0045] The composition is thus sprayed in step B onto the surface of the powder core in the form of a warm mist. The tablet is then cooled to 20°C, allowing the solidification of the composition on its surface.

[0046] Figure 3 is a cross-sectional view of a cleaning tablet 10 covered with stabilizer on both the upper 30 and lower 31 surfaces. The stabilizer has penetrated inside the cleaning tablet.

[0047] The method described above can be used to spray the stabilizing composition on one, two, three, four, five or the six faces of the powder core.ExamplesPreparation of test tablets:

[0048] 6 identical compacted powder cores were treated with Polyethylene glycol 4000 under different settings.

[0049] Polyethylene glycol 4000 was applied either to two (top, bottom), four (top, bottom and two sides) or all six surfaces of a cleaning tablet having a size of 36 mm x 26 mm x 14 mm (volume of the tablet 13,10 cm 3< ) as described in reference to figure 2. For each condition, either 0.4g or 1.1g of Polyethylene glycol 4000 was applied by mist spraying per tablet. The resulting cleaning tablets were then packaged in a cardboard box containing polyethylene providing protection against humidity (recycled cardboard comprising recyclable polyethylene). The tablets were stored for 4 weeks at 35°C under a relative humidity of 75%.

[0050] The tablets are usually packaged in cardboard boxes. It is recognized by industry professionals that tablet dimensions can vary slightly in post-production. These variations are well known to the skilled person and are considered normal. Without limiting this - a tablet can have dimensions of L. 3,35 cm x 1. 2,35 cm x H. 1,6 cm, with a tolerance of a few millimeters. Such dimensions are given as guidelines.Example 1: Dimensional stability

[0051] Two comparison groups, each including the set of test tablets described above, were formed: a first group where the packaging remained closed during storage, and a second group where the packaging remained open, so that the aging of the tablets can be measured.

[0052] The dimensional stability of a cleaning tablet represents its ability to maintain its initial physical characteristics under varying conditions. It makes it possible to evaluate in particular the deformation of a cleaning tablet, resulting from external factors such as humidity. Dimensional stability is measured by comparing the initial volume of the tablet of the cleaning tablet, observed before storage, to the final volume after 4 weeks of storage according to the protocol. The percentage of increase of the tablet volume i.e. the volume expansion, is calculated. The higher the volume expansion is, the less the tablet is stabilized. These cleaning tablets were compared to a cleaning tablet with a well-known individual water-soluble packaging comprising polyvinyl alcohol, used as a reference. The data collected has been included in Table 1 below. Table 1: Dimensional stability of the cleaning tabletAmount of stabilized composition sprayed per tablet (g)Quantity of stabilized composition sprayed per tablet (gr / cm 3< )Number of Stabilized surfaces of the tabletVolume expansion of Primary packaging with moisture protection, but left open (%)Volume expansion of Primary packaging with moisture protection, but left closed (%)Water-soluble package of polyvinyl alcohol / / 5.50.00.40,031227.76.31.10,084221.98.60.40,031429.17.81.10,084425.88.00.40,031627.47.61.10,084612.76.5

[0053] A tablet whose packaging has remained open and stabilized on two sides with little stabilizing composition will undergo more variation than a tablet stabilized on 6 sides with a greater quantity of stabilizing composition. The loss of protection against temperature and humidity for partial stabilization (2 surfaces of the tablet) and little stabilizing composition is compensated by using a packaging with moisture protection that is fully closed. As a result, the tablet does not swell and remains stable over time.

[0054] Table 1 shows the impact over time of a tablet with closed or open packaging according to the amount of stabilizing composition on its surface. The stabilizing composition permits stabilize the expansion of the tablet during storage. Also, the combination of stabilizing composition and packaging with moisture protection helps to improve the stability of the tablet over time.

[0055] The hygroscopicity of the tablet is the ability to absorb moisture from the air of the components present in the tablet. The compressed powder that forms the core of the tablet often contains salt or alkaline agents (soda ash, percarbonate, silicates, etc.), which are hygroscopic. In the absence of waterproof protection (coating, packaging, stabilizing composition), these powders absorb vapor from the air. The ambient air enters the core (pores) of the tablet. The moisture in this absorbed air causes the tablet to increase in volume, which triggers the tablet to expand. It is not the air itself that increases the volume of the tablet, but the water contained in the air that penetrates the pores of the tablet.

[0056] When a packaging with efficient moisture protection is properly closed, a greater amount of stabilizing composition does not lead to a superior dimensional stability and thus does not lead to a more stable tablet.

[0057] Regardless, it is possible to significantly reduce the amount of coating, making it easier to apply industrially and at the same time improving the stability of the tablet.Example 2: Crumbliness of the tablet

[0058] The same set of test tablets underwent a crumbliness test.

[0059] The crumbliness test consists in measuring the difference in their weight before storage and after the 4 weeks of storage. The storage was performed with the packaging closed, but tablets were extracted from the packaging before weighing. A comparative control was carried out by measuring the friability of a tablet having been packaged in the same way but devoid of stabilizing composition. The data collected are summarized in Table 2 below. The lower the weight loss is, the less the tablet is friable at tits surface ensuring a good visual and aesthetic aspect of the tablet. Table 2: Crumbliness of the tabletAmount of stabilizing composition sprayed per tablet (g)Number of Stabilized surfaces of the tabletQuantity of stabilized composition sprayed per tablet (gr / cm 3< )Primary packaging with moisture protection, but left closed - weight variation (g)0.00 / -0.850.420,031-0.121.120,084-0.810.440,031-0.401.140,084-0.840.460,031-0.281.160,084-1.110, 360,024-0,28

[0060] The use of a stabilizing composition reduces the crumbliness of a tablet and thus preserves its structure.

[0061] Here we see that at 0.031 and 0.024 g / cm 3< of surface the tablet is less friable than the tablet without the stabilizing composition, even if all the 6 sides are not sprayed. With a stabilizing composition of 0.084g / cm 3< , the tablet is at least, if not more friable than the reference without the stabilizing composition.

[0062] Applying a small quantity of stabilizing composition to the whole tablet greatly reduces its friability compared to a tablet without stabilizing composition. However, increasing the quantity of stabilizing composition over the entire surface of the tablet leads to over spraying, resulting in, for example, in an increase of the maintenance costs of the spraying process, as well as and the formation of a thick layer over the tablet. As a result, this layer can easily detach from the tablet under mechanical stress, as the stabilizing composition is no longer part of the tablet. The more stabilizing composition applied, the more crumbled the tablet becomes. A small amount of stabilizing composition is enough to reduce crumbliness, while moisture protection is effectively provided by the packaging.

[0063] Skilled persons in the art will appreciate that many different embodiments can be implemented without departing from the principles of the invention. It is understood that the examples provided herein are non-limiting, and that a person skilled in the art will be able to adjust dimensions or parameters as needed to achieve reproducible results within the scope of the invention.

Examples

example 1

Dimensional stability

[0051]Two comparison groups, each including the set of test tablets described above, were formed: a first group where the packaging remained closed during storage, and a second group where the packaging remained open, so that the aging of the tablets can be measured.

[0052]The dimensional stability of a cleaning tablet represents its ability to maintain its initial physical characteristics under varying conditions. It makes it possible to evaluate in particular the deformation of a cleaning tablet, resulting from external factors such as humidity. Dimensional stability is measured by comparing the initial volume of the tablet of the cleaning tablet, observed before storage, to the final volume after 4 weeks of storage according to the protocol. The percentage of increase of the tablet volume i.e. the volume expansion, is calculated. The higher the volume expansion is, the less the tablet is stabilized. These cleaning tablets were compared to a cleaning tablet wit...

example 2

Crumbliness of the tablet

[0058]The same set of test tablets underwent a crumbliness test.

[0059]The crumbliness test consists in measuring the difference in their weight before storage and after the 4 weeks of storage. The storage was performed with the packaging closed, but tablets were extracted from the packaging before weighing. A comparative control was carried out by measuring the friability of a tablet having been packaged in the same way but devoid of stabilizing composition. The data collected are summarized in Table 2 below. The lower the weight loss is, the less the tablet is friable at tits surface ensuring a good visual and aesthetic aspect of the tablet.

Table 2: Crumbliness of the tablet

Amount of stabilizing composition sprayed per tablet (g)Number of Stabilized surfaces of the tabletQuantity of stabilized composition sprayed per tablet (gr / cm 3Primary packaging with moisture protection, but left closed - weight variation (g)

0.00 / -0.85

0.420,031-0.12

1.120,084-0.81

0.440...

[0001] The present invention relates to a cleaning tablet, in particular solid cleaning tablets, and to the method of manufacturing them.

[0002] A cleaning tablet comprises a powder mix of cleaning agents with possibly carrier agents, which is compacted to form a block or a core. The specific composition of the powder mix depends on the application. It is designed to provide a pre-measured amount of compacted cleaning powder in an easy-to-use format. A cleaning tablet can have different shapes such as a parallelepiped, a cylinder, a diamond, a cone, a prism, a pyramid, a sphere, or any specific shape depending on the industry and / or the product and / or the release of the ingredients over time.

[0003] Examples of cleaning tablets include detergent tablets, dishwasher tablets, tablets to reconstitute detergent or cleaning solutions, toilet tablets, washing machine tablets, multi-purpose tablets, etc.

[0004] Generally, a process for manufacturing a cleaning tablet includes a step of formulation the powder composition, a step of granulation and / or compressing the powder to transform it into a solid product. After this step the surface of the tablet can be crumbly. A coating step can be implemented, where a coating composition is applied to the surface of the tablet, and an optionally drying step to remove excess liquid from the coating step, in order to form a solid protective shell around the tablet. Other intermediate or additional steps may be added, such as a tablet packaging step.

[0005] The coating composition must enable both good wetting and good fixing of the powder on the surface, while allowing the formation of a solid shell to protect the tablet from impact and moisture. The coating composition comprises one or more coating agents. Coating agents are compounds used to create a protective outer layer around the tablet. Coating agents can be polymers, waxes, gums, or other substances specifically formulated as required.

[0006] On one hand the coating compositions with the best wetting and powder fixation properties are polymers such as polyacrylate, or biopolymers such as starch. The coating composition is applied in an aqueous liquid phase to the surface of the tablet. The water is then evaporated during a drying step. However, this coating process has intrinsic defects. As the detergent tablet is formulated based on a water-soluble compound, the water present in the coating composition can interact with the tablet, either by solubilizing part of the tablet, or by triggering reactivity and instability between the tablet's most reactive chemical constituents. Also, after drying, the coatings obtained are generally very hygroscopic and therefore sensitive to humidity, making the tablet not very stable over time.

[0007] In addition, the use of these polymers or biopolymers requires a drying step. However, these compounds are very adhesive and stick to the tablet coating and conveying equipment, making cleaning under internal conditions very difficult and time consuming.

[0008] On another hand, the coating compositions that form the best protective shells are polymers or biopolymers or non-aqueous solid fats with a high melting temperature. The coating composition is heated and melted, then used by depositing it on the surface of the tablet by dipping, coating or spraying. The composition solidifies as it cools, forming a shell on the tablet. The coatings are generally thick but more protective against humidity and storage conditions. The drying step is not necessary, and the compounds are not very adhesive, facilitating the handling of the tablet. However, the quantity of coating composition used is high, the coating is less adhesive to the tablet, and parts of the coating can peel off the tablet (deformation of the tablet). Also, as the quantity of coating composition required is very high, it leaves residues in the manufacturing equipment. Usually, a cleaning step of the industrial equipment (chemical or mechanical) is added, impacting on the production schedule and costs.

[0009] Moreover, the above coating steps are time-consuming and slow down the overall production rate. Achieving a uniform coating layer on all tablets can also be a challenge. Non-uniform coating distribution can affect the stability and appearance of the tablet.

[0010] The applicant has therefore judged necessary to conceive a cleaning tablet which appearance and structure remain stable during manufacture and storage overcoming at least in part the problems deriving from the coatings described above and the associated methods.Solution of the invention

[0011] To this purpose, the invention relates to a cleaning tablet having a compacted powder core of which at least part of the surface is covered by a stabilizing composition, said stabilizing composition being water soluble and having a melting temperature of between 40 and 100 °C, and said stabilizing composition is sprayed onto the surface of the core in quantities ranging from 0.01 to 0.12 g / cm 3< of the tablet.

[0012] In the cleaning tablet according to the invention, whose surface is covered with a stabilizing composition, the powder forming the core is prevented from crumbling thanks to a stabilizing composition. This stabilizing composition forms cohesive bonds with the powder particles at the surface of the core, thereby reinforcing the structure of the tablet. Contrary to the known coatings which form thick layers over the tablet, the stabilized layer forms part of the tablet.

[0013] The compacted powder core comprises cleaning substances in the form of powder, as is well known to a person skilled in the art.

[0014] A stabilizing composition is a chemical substance or mix of substances whose purpose is to strengthen powder cohesion, prevent crumbling, and protect the surface against external influences, such as humidity. The stabilizing composition according to the invention is designed to penetrate the pores of a solid substance, such as the core of the cleaning tablet, thereby creating mechanical bonds with the particles on the surface of the tablet and / or in the compacted powder core. By penetrating the pores of the tablet, this composition promotes a stronger, more stable structure, contributing to mechanical strength and integrity of the tablet. The stabilizing composition, which unlike a coating, is not a simple layer on the surface of the tablet, but penetrates the compact powder core of the tablet and contributes to the stability of the tablet.

[0015] Unlike a coating, it penetrates the gaps and pores of the compressed core, allowing a partial filling of the porosity. This mechanism promotes cohesion between the powder particles, thus strengthening the mechanical stability of the tablet. The stabilizing composition can be considered as an internal consolidating agent. Preferably, the stabilizing composition is not a coating.

[0016] Thus, it contributes to its long-term physical stability. The stabilizing composition plays a crucial role in preserving the powder's original characteristics, limiting its interaction with adverse environmental conditions such as humidity, while promoting easy handling, safe storage, and efficient use of the cleaning tablet.

[0017] The stabilizing composition is water-soluble, meaning that upon use, when placed in an aqueous media, it will entirely solubilize.

[0018] The stabilizing composition can comprise a single substance or a mixture of substances. For example, the composition can comprise one stabilizing substance or a combination of stabilizing substances, such as polyethers. Examples of stabilizing substances suitable for the stabilizing composition of the invention are water soluble polyethers such as polyalkylether, for example poloxamer such as polyethylene glycols, polyethylene-propylene glycols; or alkyl polyether for example alkyl-polyethylene glycols, alkyl-polyethylene-polypropylene glycols; or alcohols alkoxylates for example alcohols ethoxylated, alcohols ethoxylated-propylated; or a mixture of at least two polyethers.

[0019] Preferably, the stabilizing composition comprises at least one polyether.

[0020] Preferably, the stabilizing composition comprises at least two polyethers.

[0021] Preferably, the stabilizing composition comprises at least one alcohol alkoxylate.

[0022] Preferably, the stabilizing composition comprises at least one polyethylene glycol.

[0023] Preferably, the stabilizing composition is composed of water-soluble polyethylene glycols based on natural plants. Example of such natural polyethylene glycols are PEG 1500, PEG 4000, PEG 6000 or a mixture of at least two polyethylene glycols. PEG 4000 is the most preferred polyethylene glycol.

[0024] Preferably, the stabilizing composition comprises a mixture of at least two polyethers.

[0025] Preferably, the stabilizing composition comprises a mixture of at least one polyether and at least one alcohol alkoxylate.

[0026] Preferably, the stabilizing composition is devoid of water and solvent. It may further comprise additives, processing aids, coloring agents or any other substance. Preferably however, the stabilizing substance(s) amount for at least 90% weight of the composition, preferably at least 95% of the composition. The stabilizing composition is also preferably devoid of water and / or devoid of solvent.

[0027] Preferably, the melting temperature of the stabilizing composition is from 40 to 100 °C, preferably from 40 to 90 °C, more preferably from 41 to 80°C, more preferably from 42 to 70°C, more preferably from 45 to 65°C.

[0028] The cleaning tablet can have different shapes such as a parallelepiped, a cylinder, a diamond, a cone, a prism, a pyramid, a sphere, an octahedron, an ellipsoid, or a specific shape depending on the industry and / or the product and / or the release of the ingredients over time. For instance, a parallelepiped cleaning tablet may have a length varying from 2 to 4 cm, a width varying from 1.5 to 3 cm and a height varying from 1 to 2 cm. The manufacturing method of the tablet of the invention is particularly flexible and can adapt to any shape. One aspect of the present invention is to minimize the quantity of stabilizing composition required, not only for economic reasons but also to facilitate the overall manufacturing process, equipment cleaning and improved tablet appearance. The quantity of stabilizing composition is minimized by the method of manufacture in the present invention using mist spraying technology.

[0029] The stabilizing composition can represent from 0.01 to 0.05 g / cm 3< of the tablet, or more preferably 0.02 to 0.04 g / cm 3< of the tablet even more preferably 0.02 g / cm 3< or less.

[0030] The invention also relates to the method of manufacturing a cleaning tablet according to the invention. The method comprises the steps of: ∘ the stabilizing composition according to the invention, is melted; ∘ the melted stabilizing composition is applied by mist spraying on at least part of the surface of the compacted powder core.

[0031] The stabilizing composition helps to protect the stability of the tablet and requires only a small quantity to fix the tablet's surface powder. Preferably, the stabilizing composition is sprayed on the surface of the core in amounts ranging from 0.01 to 0.12 g / cm 3< of the tablet, more preferably from 0.01 g to 0.05 g / cm 3< , the most preferred 0.02 g / cm 3< .

[0032] Mist spraying is a process consisting in dispersing a liquid in the form of fine droplets in the air. This process is used in various applications including chemical spraying, cooling, humidification, disinfection, agricultural spraying, etc. Mist spraying can be carried out using different known techniques such as pneumatic spraying, electrostatic spraying, thermal spraying, aerosol spraying. Mist spraying can produce a warm mist of finely atomized particles of stabilizing composition. Preferably, the mist spraying is obtained by a technology of atomized spray.

[0033] Generally, the melted stabilizing composition to be atomized is introduced into the spray nozzle through a feed channel. Through another channel, air is introduced into the spray nozzle. Air and liquid flows converge through the nozzle to a common outlet. When the liquid is exposed to the air pressure, it is broken into fine droplets. The air flow plays a crucial role in breaking up the liquid into small particles. Adequate air pressure is essential to effectively break up liquid into fine droplets. Preferably, the mist spraying uses an air pressure from 0.5 to 8 bars, more preferably from 0.5 to 4.0 bars.

[0034] The temperature of the compressed air can also influence the process. In order to obtain an adequate low viscosity and avoid precipitation of the melted stabilizing composition in the mist spraying equipment and air flow should be above the melting temperature of the stabilizing composition. Preferably, the mist spraying uses an air temperature from 50 to 110°C, more preferably from 60 to 100°C, more preferably from 65 to 95°C.

[0035] The flow rate of the melted stabilizing composition determines the amount of composition sprayed per unit of time. Preferably, the melted stabilizing composition pressure is set from 1.0 to 8.0 bars, more preferably from 1.0 to 4.0 bars.

[0036] Different types of air spray nozzles can be used, as long as they are compatible with the air pressure, liquid pressure and operating temperature of the present invention, such as those supplied by Spraying system co.

[0037] Preferably, the stabilizing composition is sprayed in the form of particles with a diameter of up to 300 µm, more preferably with a diameter of up to 200 µm, more preferably with a diameter of up to 100 µm, more preferably with a diameter less than 100 µm (i.e. 90% of the particles have a diameter having this value or below). The diameter of the particles can be measured using various methods well known to those skilled in the art, for example, by using a laser diffraction granulometer such as the Mastersizer from Malvern Panalytical.

[0038] Preferably, the mist spraying is carried out on at least one surface of the table, more preferably on at least 50% of the surface, at least on 60% of the surface, at least on 75% of the surface and more preferably on the total surface of the tablet.

[0039] As the stabilizing composition is devoid of water or solvent, the method of manufacturing the tablet according to the invention does not include a drying step requiring heat. Preferably, after the mist spraying step, a cooling step can be carried out to solidify the stabilizing composition, which can be active cooling (ventilation cooling, forced air cooling, etc) or passive cooling (ambient air cooling)

[0040] The cleaning tablet can be further packed in an individual packaging such as a plastic bag, paper fiber based bag, carton skillet, blister packaging, aluminum packaging or any material with is design to provide moisture protection properties.Detailed description of the invention

[0041] The invention will be better understood on reading the following description of embodiments of the invention, with reference to the figures where: Figure 1 shows a parallelepiped-shaped cleansing tablet according to the invention. Figure 2 illustrates the manufacturing process of the cleaning tablet of Figure 1, the top surface of which is covered with a stabilizing composition. Figure 3 is a cross-sectional view of a cleaning tablet according to the invention, where the top and bottom surfaces are covered with a stabilizing composition.

[0042] With reference to figure 1, a cleaning tablet 1 is a 6-sided rectangular parallelepiped comprising a core 2 of compacted powder, for example dishwashing powder. The top surface of the compacted powder core 2 is covered with a stabilizing composition 3.

[0043] The stabilizing composition 3 consists here of a pure bio-sourced polyethylene glycol. It has a molar mass of 4000 and a melting temperature from 54 to 58°C.

[0044] With reference to figure 2, to manufacture the tablet 1, the polyethylene glycol 3 is heated in a step A above its melting temperature, i.e. above 80°C to obtain a liquid form. The liquid obtained passes through an air atomization nozzle 4 (or high-pressure pneumatic spray nozzle) and a valve, as for example supplied by the company "Spraying system Co" in order to form a mist spray 5 of droplets of polyethylene glycol 3 which is oriented toward a compressed powder core 2. The air in the nozzle has here a temperature of 75°C and a pressure of 0.8 bar. The core 2 is passed under the nozzle at a speed of for example 6 m / min and the distance between the nozzle and the core surface is here for example 47 mm.

[0045] The composition is thus sprayed in step B onto the surface of the powder core in the form of a warm mist. The tablet is then cooled to 20°C, allowing the solidification of the composition on its surface.

[0046] Figure 3 is a cross-sectional view of a cleaning tablet 10 covered with stabilizer on both the upper 30 and lower 31 surfaces. The stabilizer has penetrated inside the cleaning tablet.

[0047] The method described above can be used to spray the stabilizing composition on one, two, three, four, five or the six faces of the powder core.ExamplesPreparation of test tablets:

[0048] 6 identical compacted powder cores were treated with Polyethylene glycol 4000 under different settings.

[0049] Polyethylene glycol 4000 was applied either to two (top, bottom), four (top, bottom and two sides) or all six surfaces of a cleaning tablet having a size of 36 mm x 26 mm x 14 mm (volume of the tablet 13,10 cm 3< ) as described in reference to figure 2. For each condition, either 0.4g or 1.1g of Polyethylene glycol 4000 was applied by mist spraying per tablet. The resulting cleaning tablets were then packaged in a cardboard box containing polyethylene providing protection against humidity (recycled cardboard comprising recyclable polyethylene). The tablets were stored for 4 weeks at 35°C under a relative humidity of 75%.

[0050] The tablets are usually packaged in cardboard boxes. It is recognized by industry professionals that tablet dimensions can vary slightly in post-production. These variations are well known to the skilled person and are considered normal. Without limiting this - a tablet can have dimensions of L. 3,35 cm x 1. 2,35 cm x H. 1,6 cm, with a tolerance of a few millimeters. Such dimensions are given as guidelines.Example 1: Dimensional stability

[0051] Two comparison groups, each including the set of test tablets described above, were formed: a first group where the packaging remained closed during storage, and a second group where the packaging remained open, so that the aging of the tablets can be measured.

[0052] The dimensional stability of a cleaning tablet represents its ability to maintain its initial physical characteristics under varying conditions. It makes it possible to evaluate in particular the deformation of a cleaning tablet, resulting from external factors such as humidity. Dimensional stability is measured by comparing the initial volume of the tablet of the cleaning tablet, observed before storage, to the final volume after 4 weeks of storage according to the protocol. The percentage of increase of the tablet volume i.e. the volume expansion, is calculated. The higher the volume expansion is, the less the tablet is stabilized. These cleaning tablets were compared to a cleaning tablet with a well-known individual water-soluble packaging comprising polyvinyl alcohol, used as a reference. The data collected has been included in Table 1 below. Table 1: Dimensional stability of the cleaning tabletAmount of stabilized composition sprayed per tablet (g)Quantity of stabilized composition sprayed per tablet (gr / cm 3< )Number of Stabilized surfaces of the tabletVolume expansion of Primary packaging with moisture protection, but left open (%)Volume expansion of Primary packaging with moisture protection, but left closed (%)Water-soluble package of polyvinyl alcohol / / 5.50.00.40,031227.76.31.10,084221.98.60.40,031429.17.81.10,084425.88.00.40,031627.47.61.10,084612.76.5

[0053] A tablet whose packaging has remained open and stabilized on two sides with little stabilizing composition will undergo more variation than a tablet stabilized on 6 sides with a greater quantity of stabilizing composition. The loss of protection against temperature and humidity for partial stabilization (2 surfaces of the tablet) and little stabilizing composition is compensated by using a packaging with moisture protection that is fully closed. As a result, the tablet does not swell and remains stable over time.

[0054] Table 1 shows the impact over time of a tablet with closed or open packaging according to the amount of stabilizing composition on its surface. The stabilizing composition permits stabilize the expansion of the tablet during storage. Also, the combination of stabilizing composition and packaging with moisture protection helps to improve the stability of the tablet over time.

[0055] The hygroscopicity of the tablet is the ability to absorb moisture from the air of the components present in the tablet. The compressed powder that forms the core of the tablet often contains salt or alkaline agents (soda ash, percarbonate, silicates, etc.), which are hygroscopic. In the absence of waterproof protection (coating, packaging, stabilizing composition), these powders absorb vapor from the air. The ambient air enters the core (pores) of the tablet. The moisture in this absorbed air causes the tablet to increase in volume, which triggers the tablet to expand. It is not the air itself that increases the volume of the tablet, but the water contained in the air that penetrates the pores of the tablet.

[0056] When a packaging with efficient moisture protection is properly closed, a greater amount of stabilizing composition does not lead to a superior dimensional stability and thus does not lead to a more stable tablet.

[0057] Regardless, it is possible to significantly reduce the amount of coating, making it easier to apply industrially and at the same time improving the stability of the tablet.Example 2: Crumbliness of the tablet

[0058] The same set of test tablets underwent a crumbliness test.

[0059] The crumbliness test consists in measuring the difference in their weight before storage and after the 4 weeks of storage. The storage was performed with the packaging closed, but tablets were extracted from the packaging before weighing. A comparative control was carried out by measuring the friability of a tablet having been packaged in the same way but devoid of stabilizing composition. The data collected are summarized in Table 2 below. The lower the weight loss is, the less the tablet is friable at tits surface ensuring a good visual and aesthetic aspect of the tablet. Table 2: Crumbliness of the tabletAmount of stabilizing composition sprayed per tablet (g)Number of Stabilized surfaces of the tabletQuantity of stabilized composition sprayed per tablet (gr / cm 3< )Primary packaging with moisture protection, but left closed - weight variation (g)0.00 / -0.850.420,031-0.121.120,084-0.810.440,031-0.401.140,084-0.840.460,031-0.281.160,084-1.110, 360,024-0,28

[0060] The use of a stabilizing composition reduces the crumbliness of a tablet and thus preserves its structure.

[0061] Here we see that at 0.031 and 0.024 g / cm 3< of surface the tablet is less friable than the tablet without the stabilizing composition, even if all the 6 sides are not sprayed. With a stabilizing composition of 0.084g / cm 3< , the tablet is at least, if not more friable than the reference without the stabilizing composition.

[0062] Applying a small quantity of stabilizing composition to the whole tablet greatly reduces its friability compared to a tablet without stabilizing composition. However, increasing the quantity of stabilizing composition over the entire surface of the tablet leads to over spraying, resulting in, for example, in an increase of the maintenance costs of the spraying process, as well as and the formation of a thick layer over the tablet. As a result, this layer can easily detach from the tablet under mechanical stress, as the stabilizing composition is no longer part of the tablet. The more stabilizing composition applied, the more crumbled the tablet becomes. A small amount of stabilizing composition is enough to reduce crumbliness, while moisture protection is effectively provided by the packaging.

[0063] Skilled persons in the art will appreciate that many different embodiments can be implemented without departing from the principles of the invention. It is understood that the examples provided herein are non-limiting, and that a person skilled in the art will be able to adjust dimensions or parameters as needed to achieve reproducible results within the scope of the invention.

Examples

example 1

Dimensional stability

[0051]Two comparison groups, each including the set of test tablets described above, were formed: a first group where the packaging remained closed during storage, and a second group where the packaging remained open, so that the aging of the tablets can be measured.

[0052]The dimensional stability of a cleaning tablet represents its ability to maintain its initial physical characteristics under varying conditions. It makes it possible to evaluate in particular the deformation of a cleaning tablet, resulting from external factors such as humidity. Dimensional stability is measured by comparing the initial volume of the tablet of the cleaning tablet, observed before storage, to the final volume after 4 weeks of storage according to the protocol. The percentage of increase of the tablet volume i.e. the volume expansion, is calculated. The higher the volume expansion is, the less the tablet is stabilized. These cleaning tablets were compared to a cleaning tablet wit...

example 2

Crumbliness of the tablet

[0058]The same set of test tablets underwent a crumbliness test.

[0059]The crumbliness test consists in measuring the difference in their weight before storage and after the 4 weeks of storage. The storage was performed with the packaging closed, but tablets were extracted from the packaging before weighing. A comparative control was carried out by measuring the friability of a tablet having been packaged in the same way but devoid of stabilizing composition. The data collected are summarized in Table 2 below. The lower the weight loss is, the less the tablet is friable at tits surface ensuring a good visual and aesthetic aspect of the tablet.

Table 2: Crumbliness of the tablet

Amount of stabilizing composition sprayed per tablet (g)Number of Stabilized surfaces of the tabletQuantity of stabilized composition sprayed per tablet (gr / cm 3Primary packaging with moisture protection, but left closed - weight variation (g)

0.00 / -0.85

0.420,031-0.12

1.120,084-0.81

0.440...

Claims

1. Cleaning tablet (1) having a compacted powder core (2) of which at least part of the surface is covered by a stabilizing composition (3), said stabilizing composition being water soluble and having a melting temperature of between 40 and 100 °C, and said stabilizing composition is sprayed onto the surface of the core in quantities ranging from 0.01 to 0.12 g / cm3 of the tablet.

2. Cleaning tablet according to claim 1, wherein the stabilizing composition comprises at least one polyether.

3. Cleaning tablet according to claim 1 or 2, wherein the stabilizing composition comprises at least one alcohol alkoxylate.

4. Cleaning tablet according to claim 2 wherein the polyether comprises a polyethylene glycol.

5. Cleaning tablet according to one of claims 1 to 4, wherein stabilizing composition comprise a mixture of at least two polyether and at least one alcohol alkoxylate.

6. Cleaning tablet according to one of claims 1 to 5, wherein the stabilizing composition is devoid of water and solvent.

7. Cleaning tablet according to one of claims 1 to 6, wherein the stabilizing composition comprises at least 90% in weight of a stabilizing substance.

8. Cleaning tablet according to one of claims 1 to 7, wherein the stabilizing composition has a melting point between 40 and 100°C.

9. Method for manufacturing a cleaning tablet according to any one of claims 1 to 8, comprising: ∘ the stabilizing composition is melted (A); ∘ the melted stabilizing composition is applied by mist spraying (B) on at least part of the surface of the compacted powder core.

10. Method according to claim 9, wherein the mist spraying is obtained by a technology atomized spray.

11. Method according to one of the claims 9 to 10, wherein the mist spraying uses an air pressure comprised from 0.5 to 8 bars.

12. Method according to one of the claims 9 to 11, wherein the mist spraying uses an air temperature comprised from 50°C to 110°C.

13. Method according to one of the claims 9 to 12, wherein the melted stabilizing composition pressure is set from 1.0 to 8.0 bars.

14. Method according to one of the claims 9 to 13, wherein the stabilizing composition is sprayed in the form of particles having a diameter of up to 300 µm.

15. Method according to one of the claims 9 to 14, further comprising a cooling step to solidify the stabilizing composition.

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