EP3417047B1 - Method for manufacturing soap - Google Patents

Description

The subject of the present invention is a new process for manufacturing solid soap in batches, in particular a process for manufacturing Marseille soap, which is more environmentally friendly, by optimizing the water and energy consumption necessary for its implementation. implemented and limiting releases.

The basic principle of soap preparation is based on a saponification reaction in which fatty acids and/or fatty acid esters contained in fatty substances are hydrolyzed in a basic medium to form alkaline salts (carboxylates), constituting soap. , and glycerin. When the base used in the saponification reaction is soda (NaOH), the soap obtained is called “hard”, when the base is potash (KOH), the soap is called “soft” or “liquid” .

The properties and quality of the soap produced also depend on the type of process used for its manufacture, which can be discontinuous (also called "batch" or in tank) according to an "old-fashioned" method where the cooking of the soap dough was made in a cauldron, or continuous for more industrial manufacturing.

Marseille soap refers to a high quality soap obtained by a traditional batch process. The term “Marseille soap” is not a controlled designation of origin and has no official definition, but corresponds to a manufacturing process comprising essential steps. The method of manufacturing Marseille soap is generally accepted as being based on the historical stages of pasting, salting out, cooking, washing and smoothing, in order to ensure obtaining a smooth crystalline phase comprising at least 63% fatty acids in the finished product.

Mashing and cooking consist of introducing the fatty substances, most often oils or pastes of vegetable origin, rich in fatty acids and/or fatty acid esters, and the excess aqueous soda solution into a tank. or a large capacity cauldron, and mixing them by heating at high temperatures of around 120°C to reach boiling point. Saponification begins. The high temperature initiates the saponification reaction, which is then exothermic and difficult to control. It is therefore often necessary to introduce the sodium hydroxide in several installments in order to avoid a runaway reaction. Since oils and soda are not miscible, it is generally customary to introduce a base of soap from a previous manufacture in order to facilitate the formation of an emulsion between the oily and aqueous phases. The dough is cooked like this for up to 12 hours to guarantee complete saponification. Indeed, any residual non-saponified oils could become rancid and alter the color and odor of the final soap.

The terms mashing and cooking constitute the two stages of the saponification reaction: mashing designates the initiation of the saponification reaction, and cooking aims the continuation of the reaction, kinetically slower, allowing complete saponification .

The release and washing stages essentially consist of adding salt water to the soap paste obtained during the pasting and cooking stages to extract the glycerin formed, but also the various impurities present in the raw materials used or in the base of soap used, or formed during manufacturing due to the operating conditions implemented during the pasting and cooking stages. The terms release and washing both refer to the same type of operation, the term "release" being generally used to designate the first step of washing the soap paste obtained, allowing the extraction of part of the soap paste. impurities and glycerin. The release steps are carried out, washing with an aqueous solution saturated with sodium chloride (360 g of NaCl per liter), at high temperature (>104°C). As soap is very poorly soluble in salt water, unlike soda and glycerin, it precipitates and can be recovered after decantation.

In the traditional process of manufacturing Marseille soap, it is generally necessary to carry out several washing stages (4 to 6) to achieve a soap free of all its impurities. These numerous washings with large volumes of salt water result in large quantities of waste to be reprocessed, and significant energy consumption, which significantly increases the costs of producing Marseille soap and has a strong environmental impact. Soap washed in salt water is certainly free of its impurities, soda and glycerin, but it has an inhomogeneous grained appearance due to the presence of significant quantities of salt (NaCl). This grained soap is therefore not “processable”, that is to say it is not possible to shape it to obtain soap bars that can be stored and then marketed.

Thus, an additional smoothing step is necessary to obtain a homogeneous soap paste, having controlled water, salt and soda contents to allow its subsequent drying and shaping. Smoothing can in particular be carried out by liquidation, that is to say by washing the grained soap with large quantities of pure water to remove excess salt (NaCl), boiling, then decanting to remove the water. salty.

These traditional processes for manufacturing Marseille soap are poorly suited to current environmental constraints which tend to rationalize water and energy consumption and limit discharges to be more respectful of the environment, and improve the productivity and profitability of products, while ensuring a high level of quality.

The subject of the present invention is thus a new soap manufacturing process, particularly suitable for the manufacture of Marseille soap, the water and energy consumption of which is reduced compared to traditional Marseille soap manufacturing processes, thus limiting the quantities of emissions emitted. The Marseille soap thus obtained presents the particularity of containing a controlled content of glycerin, resulting from the saponification reaction, without the latter being added to the soap formed. Indeed, according to the requirements of certain traditional soapmakers, Marseille soap must not only be prepared according to very specific process steps previously described, but must also not be modified by the introduction of additives. By additive we mean here any ingredient introduced after saponification, apart from the reagents necessary for manufacturing and the constituents of the washing and smoothing solutions.

However, the traditional preparation process for Marseille soap involves as many washing and smoothing steps as necessary to obtain a soap paste which is processable, that is to say which can be dried and shaped. For the purposes of this application, it is considered that a soap is processable if it comprises, before drying, less than 33% by weight of water, less than 0.7% by weight of salt and less than 0.2%. by weight of free soda (in NaOH form).

The large number of washing steps necessary to achieve the desired levels of water, salt and soda result in complete elimination of glycerin from the soap. However, glycerin is a humectant and hydrating agent for the skin, and gives the soap a creamier lather. It may therefore be desirable to keep it, at least in part, in the soap during its manufacture, since it could be considered as an additive if it were to be added after manufacturing the soap, which could impact the designation of the product. under the term “Marseille soap” according to certain definitions.

FR 1 337 212 , FR 2 008 916 And FR 946 742 describe soap making processes. However, the objective of these processes is not to obtain a soap with a controlled glycerin content, but on the contrary is to eliminate the glycerin from the soap to recover and valorize it.

The present invention therefore proposes a new process for preparing soap, and in particular Marseille soap, comprising the essential steps in the manufacture of Marseille soap implemented in an optimized manner to obtain an efficient and more environmentally friendly process. , making it possible to prepare a processable soap, that is to say comprising before drying less than 33% by weight of water, less than 0.7% by weight of salt and less than 0.2% by weight of free soda (NaOH), said soap comprising a controlled content of glycerin, without it being added as an additive to the soap, to give it hydrating properties, and therefore better dermatological qualities, and guarantee a creamier foam.

1. a. une étape d'empâtage et de cuisson dans laquelle :
   • on mélange au moins un acide gras et/ou ester d'acide gras avec une solution aqueuse de soude,
   • on chauffe le mélange pour obtenir une pâte de savon,
2. b. au moins une étape de lavage de la pâte de savon obtenue à l'étape a. dans laquelle :
   • la pâte de savon est mélangée avec une solution aqueuse comprenant 1 à 42% en poids d'un mélange de soude et de sel,
   • le mélange est chauffé, et laissé à décanter jusqu'à formation de deux phases : le savon grainé comprenant du sel, de la soude et de la glycérine, et une solution aqueuse comprenant du sel, de la soude et de la glycérine,
   • le savon grainé et la solution aqueuse sont séparés,
3. c. une étape de lissage du savon grainé obtenu à l'étape b. par neutralisation dans laquelle :
   • le savon grainé est mélangé avec au moins un agent de neutralisation pouvant être un acide, un acide gras ou un ester d'acide gras,
   • le mélange est chauffé et le savon lisse est obtenu.

The subject of the invention is therefore, according to a first aspect, a discontinuous process for manufacturing soap comprising at least the following steps:

1. has. a mashing and cooking step in which:
   • at least one fatty acid and/or fatty acid ester is mixed with an aqueous sodium hydroxide solution,
   • the mixture is heated to obtain a soap paste,
2. b. at least one step of washing the soap paste obtained in step a. in which :
   • the soap paste is mixed with an aqueous solution comprising 1 to 42% by weight of a mixture of soda and salt,
   • the mixture is heated, and left to decant until two phases are formed: the grained soap comprising salt, soda and glycerin, and an aqueous solution comprising salt, soda and glycerin,
   • the grained soap and the aqueous solution are separated,
3. vs. a step of smoothing the grained soap obtained in step b. by neutralization in which:
   • the grained soap is mixed with at least one neutralizing agent which may be an acid, a fatty acid or a fatty acid ester,
   • the mixture is heated and smooth soap is obtained.

The subject of the invention is therefore, according to a second aspect, a smooth soap capable of being manufactured using the method previously described.

It is indeed to the merit of the inventors to have observed that by using a very specific aqueous solution of electrolytes for the washing stages, comprising in particular a mixture of soda and salt in a well-defined content, it was possible, in a limited number of washing steps, to effectively wash the soap, while retaining a desired quantity of glycerin, and to obtain a processable soap having the properties required for the subsequent drying and shaping steps.

By discontinuous process (also called “batch” or in tank), within the meaning of the present application, is meant a process in which the soap is manufactured in discrete batches from reagents placed in determined quantities in a tank of determined capacity, as opposed to continuous processes based on a system of dosing pumps which continuously supply the saponification reactor with raw materials. The batch process is preferably carried out in open tanks or reactors, that is to say non-hermetic. Preferably, in the batch process of the invention, the different stages are carried out at atmospheric pressure, in the presence of air. The process of the invention being preferably implemented in a stirred reactor, guaranteeing the homogeneity of the medium and under mild temperature conditions, the losses of material by evaporation can be considerably limited without the need to operate in reactors. airtight. The operating conditions make it possible to preserve the quality of the raw materials and not to denature the product during its manufacture and thus to guarantee the quality of the soap obtained.

Pasting, releasing, cooking

• on mélange au moins un acide gras et/ou ester d'acide gras avec une solution aqueuse de soude,
• on chauffe le mélange pour obtenir une pâte de savon,

The manufacturing process of the invention implements at least one step a. mashing and cooking in which:

• at least one fatty acid and/or fatty acid ester is mixed with an aqueous sodium hydroxide solution,
• the mixture is heated to obtain a soap paste,

The mashing and cooking step implements the saponification reaction itself.

In this step, at least one fatty acid and/or fatty acid ester is mixed with an aqueous solution of sodium hydroxide, and optionally brine (aqueous solution comprising at least 3.5% by weight of sodium chloride (NaCl) , preferably between 10 and 30% NaCl). The brine releases glycerin.

By fatty acid is meant carboxylic acids comprising a hydrocarbon radical, saturated or unsaturated, linear or branched, comprising 6 to 30 carbon atoms, and preferably 12 to 22 carbon atoms.

As an example of saturated fatty acids, mention may be made of caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, eicosanoic acid, behenic acid, tetracosanoic acid, and their mixtures.

As an example of unsaturated fatty acids, mention may be made of sorbic acid, decylenic acid, caproleic acid, undecylenic acid, lauroleic acid, myristoleic acid, pentadecenoic acid, palmitoleic acid, palmitelaidic acid, oleic acid, elaidic acid, acid vaccenic, linoleic acid, gamma-linolenic acid, alpha-linolenic acid, steradonic acid, parinaric or stearidonic acid, gadoleic acid, dihomo-linoleic acid, dihomo-gamma-linolenic acid, arachidonic acid, timnodonic or eicosapentaenoic acid, erucic acid, acid brassidic acid, ketoleic acid, adrenic acid, clupanodonic acid, docosahexaenoic acid, nervonic or selacholeic acid, eicosadienoic acid, eicosatrienoic acid, docosadienoic acid, docosatetraenoic acid, docosapentaenoic acid.

The fatty acid and/or fatty acid ester used in step a. is usually contained in a fatty substance, preferably of plant origin.

Thus, according to a preferred embodiment, the fatty acid and/or the fatty acid ester used in step a. is a fatty substance, more preferably, the fatty substance is an oil or a vegetable paste or of vegetable origin. According to the criteria of certain soap makers, the name “Marseille soap” may in fact require the exclusive use of vegetable or plant-based fatty substances.

The term “oil” means any lipophilic, non-ionic compound, insoluble in water and liquid at room temperature (25°C) and atmospheric pressure (760 mm Hg, or 101,325 Pa). For the purposes of the present invention, the term insoluble in water means a compound whose solubility at spontaneous pH in water at 25°C and at atmospheric pressure is less than 1%, and preferably less than 0.5%. in weight. The oils preferably have a viscosity less than 500 cPs at 25°C at a shear rate of 1s ^-1 .

By pasty is meant any lipophilic, non-ionic compound, insoluble in water and semisolid or solid at room temperature (25°C) and under atmospheric pressure. Pastes preferably have a viscosity greater than 500 cPs at 25°C at a shear rate of 1s ^-1 .

In particular, the fatty substance comprising the fatty acid and/or the fatty acid ester is extracted from a species belonging to the plant kingdom. As an example of a fatty substance which can be used in the compositions of the invention, mention may be made of sweet almond oil, argan oil, avocado oil, peanut oil, etc. camellia oil, safflower oil, calophyllum oil, rapeseed oil, coconut oil, coriander oil, pumpkin oil, wheat germ oil, jojoba oil or liquid jojoba wax, linseed oil, macadamia oil, corn germ oil, hazelnut oil, walnut oil, vernonia oil, apricot kernel oil, olive oil, in particular olive pomace oil, evening primrose oil, palm oil, passionflower oil, coconut seed oil grape oil, rose oil, castor oil, rye oil, sesame oil, rice bran oil, soybean oil, and sunflower oil.

Among the fatty substances mentioned above, olive oil is preferably used, in particular acidic olive pomace oil, coconut oil, palm oil, or a mixture of these. this.

For the purposes of the invention, “acidic olive pomace oil” designates an acidic oil obtained from olive pomace. Such an oil can, for example, come from the acid hydrolysis of neutralization pastes obtained during the refining of olive pomace oil intended for food. Indeed, during the refining of olive pomace oil, one step consists of neutralizing the free fatty acids by adding soda. We obtain an oil free of free fatty acids on one side (for food use) and sodium salts of fatty acids, therefore neutralization pastes, on the other. These are these neutralization pastes which are then re-acidified to obtain oil: acidic pomace oil. Any other process for manufacturing acidic oil from olive pomace known to those skilled in the art can also be considered.

According to a preferred embodiment, the fatty substances and in particular the oils and pastes used in the process of the invention are refined, in order to limit the impurities introduced into the soap during step a., which could impact the smell, color and dermatological qualities of the final soap. Refining consists of removing metals (P, Ca, Mg, Zn, Cu, Fe) naturally present in the oil. Refining also allows the elimination of pigments, impurities likely to give a bad smell, color and quality to the soap, as well as traces of pesticides. Refining may consist of the neutralization of fatty acids by adding soda or distillation, washing with water and drying, decolorization on activated carbon, steam deodorization, filtration, etc.

The aqueous sodium hydroxide solution used in step a. preferably comprises 20% to 31% by weight of soda, preferably 25% to 30% by weight. It can be introduced into the reactor in a more concentrated form and be diluted by adding water so that its concentration in the reactor is within the aforementioned ranges.

The quantity of aqueous sodium hydroxide solution is preferably adjusted in step a. so that the soda is in excess of less than 5% relative to the stoichiometry, more preferably less than 2%, even more preferably less than 1%, so as to ensure the saponification of all the fatty acids and/or fatty acid esters used in the process.

The quantity of brine optionally introduced in step a. can in particular be between 0.1 and 5% by weight of the mixture of step a.

• 60 à 70% en poids de corps gras, de préférence 63 à 68% en poids,
• 25 à 40% en poids de solution aqueuse de soude, de préférence 29 à 36% en poids,
• 0,5 à 5% en poids de saumure, de préférence 1 à 3% en poids.

Thus, the mixture of fatty substances and aqueous sodium hydroxide solution preferably consists of:

• 60 to 70% by weight of fatty substances, preferably 63 to 68% by weight,
• 25 to 40% by weight of aqueous sodium hydroxide solution, preferably 29 to 36% by weight,
• 0.5 to 5% by weight brine, preferably 1 to 3% by weight.

The mixture is heated so that its temperature is between 60 and 110°C, in particular between 75 and 99°C, more particularly between 80°C and 90°C, for a period of 1 hour to 6 hours, preferably from 2 a.m. to 5 a.m.

Heating allows the saponification reaction to begin. The saponification reaction then being exothermic, the reaction temperature required in step a. is located between 75 and 110°C. A thermal compensation system is used, for example by means of a heat reactor. double jacket (which can be heated by a hot fluid), insulated, thermostatically controlled or not, in order to optimize energy consumption.

The quantity of sodium hydroxide present in the reaction medium of step a. is controlled by dosage (titration of the base contained in the soap, therefore the soda, with an acid, here hydrochloric acid, after solubilization of the soap in hot ethanol; according to standard NFT60-306 - determination of the caustic free alkali content), allowing monitoring of the progress of the reaction. It is in fact essential to ensure that the majority of fatty substances have been saponified since any unsaponified triglycerides could oxidize and go rancid, thus affecting the color and odor of the final soap.

According to a preferred embodiment, step a., is carried out in a reactor equipped with a mechanical stirring system, preferably allowing shearing and pumping simultaneously, ensures intimate mixing of the fatty acid and/or of the fatty acid ester with the aqueous sodium hydroxide solution, which makes it possible to avoid areas of massing and the risks of the reaction racing and guarantees the homogeneity and therefore the quality of the dough. In addition, it is no longer necessary to introduce a base of soap from a previous manufacture to allow the emulsion, which is ensured mechanically, which limits the introduction of impurities into the soap. The homogeneity of the mixture being guaranteed, the soda can be introduced in a substantially stoichiometric quantity (less than 5% excess soda). At the end of step a., a soap paste comprising a mixture of sodium carboxylates, that is to say salts of fatty acids constituting the soap, soda and water and glycerin.

Washing

• la pâte de savon est mélangée avec une solution aqueuse comprenant 1 à 42% en poids d'un mélange de soude et de sel,
• le mélange est chauffé, et laissé à décanter jusqu'à formation de deux phases : le savon grainé comprenant du sel, de la soude et de la glycérine, et une solution aqueuse comprenant du sel, de la soude et de la glycérine,
• le savon grainé et la solution aqueuse sont séparés.

The method according to the invention implements at least one step b. washing (which can also be called release/washing since it allows the release of glycerin and impurities) of the soap paste obtained in step a. in which :

• the soap paste is mixed with an aqueous solution comprising 1 to 42% by weight of a mixture of soda and salt,
• the mixture is heated, and left to decant until two phases are formed: the grained soap comprising salt, soda and glycerin, and an aqueous solution comprising salt, soda and glycerin,
• the grained soap and the aqueous solution are separated.

The grained soap obtained in step b. includes salt and soda, and glycerin.

The washing step is decisive in the process of the invention. The inventors have in fact optimized this step to allow a controlled quantity of glycerin to be preserved, preferably between 1 and 8% by weight of the smooth soap obtained after a single washing step, preferably between 2 and 5% by weight.

• 1 à 7% en poids de sel, de préférence 2 à 5% en poids de sel, plus préférentiellement 2 à 4% en poids de sel, et
• 0,01% à 40% en poids de soude, de préférence 0,9% à 20% en poids de soude, plus préférentiellement de 2% à 8% en poids de soude.

Thus, the soap paste from step a. is mixed with an aqueous solution comprising:

• 1 to 7% by weight of salt, preferably 2 to 5% by weight of salt, more preferably 2 to 4% by weight of salt, and
• 0.01% to 40% by weight of soda, preferably 0.9% to 20% by weight of soda, more preferably 2% to 8% by weight of soda.

The salt and soda contents can be adjusted by those skilled in the art depending on the nature of the oils used for the manufacture of the soap and the glycerin content desired in the final soap.

Traditional soap manufacturing processes recommend using as much water as fatty substances for washing the soap paste to allow good separation of the soap and the aqueous solution comprising salt, soda and soda. glycerin. Due to the particular electrolyte composition of the washing solution used in step b. of the process of the invention, it is possible to effectively wash the soap paste resulting from step a. without the need to use too much water.

Thus, the weight ratio of the aqueous washing solution used in step b. on the fatty acids and/or fatty acid esters introduced in step a. is less than 1, in particular between 0.2 and 0.99, and more particularly between 0.3 and 0.6.

According to a preferred embodiment, the aqueous washing solution used in step b. is added to the soap paste resulting from step a., in the same reactor equipped with a mechanical stirring system as that used for step a. As for step a., the presence of a mechanical stirring system, preferably allowing simultaneous shearing and pumping, ensures intimate mixing of the soap with the washing solution, which makes it possible to reduce the duration of the washing step and the temperatures used and to limit the quantity of washing water necessary. Thus energy consumption and waste are reduced and the quality of the soap is preserved by a limited heating time and mild temperatures.

Thus, at the start of step b., the mixture can be heated to a temperature between 70 and 99°C, in particular between 80 and 99°C and be maintained in these temperature ranges. for 30 min to 2 days, or for 45 min to 24 hours, or even for 1 hour to 18 hours, depending on the nature of the fatty acids and/or fatty acid esters used during step a.

According to a preferred embodiment, the mixture is left to settle, for example between 30 minutes and 2 days.

• le mélange est laissé à décanter pendant 30 minutes à 6h, plus préférentiellement 1h à 4h, et un premier soutirage permet de récupérer la solution aqueuse ayant décanté,
• le mélange de savon est à nouveau laissé à décanter pendant 6h à 2 jours, de préférence pendant 8 à 23h, plus préférentiellement de 12 à 18h et un second soutirage permet de séparer le savon grainé de la solution aqueuse comprenant du sel, de la soude et de la glycérine.

According to a particular embodiment, the decantation is carried out in two stages:

• the mixture is left to settle for 30 minutes to 6 hours, more preferably 1 hour to 4 hours, and a first withdrawal allows the decanted aqueous solution to be recovered,
• the soap mixture is left to decant again for 6 hours to 2 days, preferably for 8 to 23 hours, more preferably from 12 to 18 hours and a second withdrawal makes it possible to separate the grained soap from the aqueous solution comprising salt, soda and glycerin.

According to another particular embodiment, the decantation is carried out in a single step: the mixture is thus left to decant for a period ranging from 30 min to two days, then the aqueous solution having decanted is withdrawn.

The yield of aqueous washing solution, expressed as mass of aqueous solution drawn off per mass of aqueous washing solution (comprising water + electrolytes) introduced in step b. washing allows the effectiveness of decantation to be characterized. The yield of aqueous washing solution in step b. is preferably greater than 60%, in particular between 75 and 100%, in particular between 75 and 99.5%, and more particularly between 85 and 95%.

Thus, by optimizing on the one hand the composition of the aqueous washing solution and its quantity and, on the other hand, the operating parameters, in particular by the use of an appropriate stirring system, it was possible to limit significantly the number of washing steps compared to traditional soap making processes which require between 4 and 6 washing steps.

Thus, according to a preferred embodiment, the method according to the invention implements at most two steps b. washing, preferably at most one step b. washing.

Water consumption and washing water discharges are reduced accordingly. The result is a process that is more environmentally friendly and consumes less energy and allows the quality of the soap to be preserved through mild temperatures and reduced heating times.

Smoothing

• le savon grainé est mélangé avec au moins un agent de neutralisation pouvant être un acide, un acide gras ou un ester d'acide gras,
• le mélange est chauffé et le savon lisse est obtenu.

Finally, the soap manufacturing process according to the invention comprises at least one step of smoothing the grained soap obtained in step b. by neutralization in which:

• the grained soap is mixed with at least one neutralizing agent which may be an acid, a fatty acid or a fatty acid ester,
• the mixture is heated and smooth soap is obtained.

In traditional processes, the introduction of salt water during the different washing stages makes it possible to separate the soap from the aqueous washing solutions containing in particular impurities, soda and glycerin but the washed soap has a salt content ( NaCl) too high to allow its shaping. It is therefore necessary to reduce the salt level in the soap. To do this, the soap is generally smoothed by liquidation, that is to say by adding pure water. This step results in the formation of an intermediate phase of soap dissolved in water called black fat. This partial solubilization of the soap affects the reaction yields, hampering the productivity of the process and creating rejects to be reprocessed.

By introducing, into the aqueous washing solution, a mixture of salt and soda in a controlled content, the inventors demonstrated that it was thus possible to effectively separate the soap from the aqueous washing solutions without forming black grease when of the smoothing stage and to solubilize a fraction of the glycerin. We can thus directly obtain a soap free of its impurities while retaining part of the glycerin resulting from saponification.

To obtain a smooth processable soap, that is to say one which can be dried and shaped, the smooth soap must preferably comprise less than 33% by weight of water, less than 0.7% by weight of salt and less than 0.2% by weight of free soda (in NaOH form). The process according to the invention therefore implements a smoothing step by neutralization in particular to reduce the soda content of the soap.

The grained soap is thus mixed with at least one neutralizing agent which may be an acid, a fatty acid or a fatty acid ester. The use of an acid or a fatty acid allows the rapid neutralization of sodium hydroxide by acid-base reaction. The use of a fatty acid ester allows slower neutralization of the soda by saponification.

Preferably the neutralizing agent is a fatty acid or a fatty acid ester.

By fatty acid is meant carboxylic acids comprising a hydrocarbon radical, saturated or unsaturated, linear or branched, comprising 6 to 30 carbon atoms, and preferably 12 to 22 carbon atoms.

As an example of saturated fatty acids, mention may be made of caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, eicosanoic acid, behenic acid, tetracosanoic acid, and their mixtures.

Preferably, the saturated fatty acids are chosen from caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and mixtures thereof.

As an example of unsaturated fatty acids, mention may be made of sorbic acid, decylenic acid, caproleic acid, undecylenic acid, lauroleic acid, myristoleic acid, pentadecenoic acid, palmitoleic acid, palmitelaidic acid, oleic acid, elaidic acid, acid vaccenic, linoleic acid, gamma-linolenic acid, alpha-linolenic acid, steradonic acid, parinaric or stearidonic acid, gadoleic acid, dihomo-linoleic acid, dihomo-gamma-linolenic acid, arachidonic acid, timnodonic or eicosapentaenoic acid, erucic acid, acid brassidic acid, ketoleic acid, adrenic acid, clupanodonic acid, docosahexaenoic acid, nervonic or selacholeic acid, eicosadienoic acid, eicosatrienoic acid, docosadienoic acid, docosatetraenoic acid, docosapentaenoic acid.

Preferably, the unsaturated fatty acids are chosen from palmitoleic acid, oleic acid, linoleic acid, and mixtures thereof.

The fatty acid esters are preferably those previously described to be used in step a. mashing/cooking, in particular fatty substances, and in particular the oils previously described.

According to a preferred embodiment, step c. smoothing is implemented with a mixture of saturated and unsaturated fatty acids, preferably from fats of plant origin such as for example olive oil, coconut oil or palm oil. Preferably, the fatty substances used during step c. smoothing come from the same plant species as those used for saponification during step a.

Thus, during step c., the mixture is heated to a temperature between 70 and 99°C, preferably between 80 and 99°C for 10min to 5h, preferably for 30min to 2h.

Optionally, brine (aqueous solution comprising at least 0.1% by weight of sodium chloride (NaCl), preferably between 10 and 30% NaCl) can be added to the grained soap before or after adding the conditioning agent. neutralization to adjust the percentage of salt in the soap.

According to a preferred embodiment, the smoothing implemented in step c. is carried out in the same reactor equipped with a mechanical stirring system as that used for steps a or b. Same as for steps a. and b., the presence of a mechanical stirring system, preferably allowing simultaneous shearing and pumping, ensures intimate mixing of the grained soap with the fatty acid, allowing effective neutralization of the soda contained in the grained soap , which makes it possible to reduce the duration of the smoothing step and the temperatures used. The ensured homogeneity, reduced times and temperatures ensure the good quality of the soap.

Mechanical stirring system

Steps a., b. and/or c. of the process according to the invention can be implemented in a reactor equipped with a mechanical stirring system. The mechanical stirring system preferably makes it possible to simultaneously shear and pump the mixtures of steps a., b. and/or c.

According to a preferred embodiment, steps a., b. and/or c. of the process according to the invention can be implemented in the same reactor.

The reactor comprises in particular a tank comprising an interior space making it possible to produce a mixture of at least one fatty substance and a base (soda) in the interior space of the tank, and to heat the mixture. The tank has a cylindrical side wall along a central axis of circular cross section

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  • D diamètre du mobile, en mètres,
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  • P2 puissance dissipée dans la cuve par le deuxième organe d'agitation, en Watts,
  • N₂ vitesse de rotation du deuxième organe d'agitation, en tours/seconde, et Q2
• - un deuxième nombre de pompage Q₀2 compris entre 0,5 et 2 où $Q_{0}2=\frac{Q2}{N_2{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  
  avec Q2, en mètres cubes/seconde, débit passant dans une surface projetée dans un plan perpendiculaire à l'axe de pivotement du deuxième organe d'agitation

The reactor further comprises a stirring system movable in the interior space of the tank so as to circulate the mixture in the interior space of the tank, and to shear the mixture at least locally. the stirring system comprises at least a first stirring member adapted to shear the mixture and to move the mixture transversely relative to the central axis towards the side wall, and at least a second stirring member, at least the second stirring member being a mobile comprising a hub and a plurality of equally distributed blades each extending from the hub to a free end, the hub of the mobile being mounted to pivot relative to the tank in a direction of rotation around 'a pivot axis coaxial with the central axis. The second stirring member is an axial pumping mobile adapted to move the mixture in a pumping direction along the central axis of the tank, the first stirring member being arranged downstream of the second stirring member relative to the direction of pumping, each of the blades of the second stirring member having a first edge near the first stirring member and a second edge opposite the first edge along the pivot axis and at a distance from the first stirring member, the first and second edges being arranged in such a way such that the second edge is in front of the first edge with respect to the direction of rotation, the second stirring member having:

• P2 - a second power number P ₀ 2 between 0.3 and 1.5 where $P_{0}2=\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}2}{{{\mathit{<figure-callout\; id="2"\; label="\rho N"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\rho N</figure-callout>}}_2}^3{D}^5}$
  
  with
  • D diameter of the mobile, in meters,
  • ρ viscosity of the mixture, in Pascals/second,
  • P2 power dissipated in the tank by the second stirring member, in Watts,
  • N ₂ rotation speed of the second stirring member, in revolutions/second, and Q2
• - a second pumping number Q ₀ 2 between 0.5 and 2 where $Q_{0}2=\frac{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Q</figure-callout>}2}{{\mathrm{NOT}}_2{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  
  with Q2, in cubic meters/second, flow rate passing through a surface projected in a plane perpendicular to the pivot axis of the second stirring member

The reactor also includes a heating system adapted to heat the mixture in the interior space of the tank.

During the mashing and cooking step, the stirring system is moved in the mixture so as to circulate the mixture in the interior space of the tank and to shear the mixture at least locally. In particular, the mixture is moved in the pumping direction along the central axis of the tank by the second stirring member towards the first stirring member, and sheared and moved transversely relative to the central axis towards the wall lateral by the first stirring member.

Thus, the invention uses a second stirring member whose blades are inclined towards the first stirring member and whose pumping number is high while the power number is low. The second stirring member has the function of pumping the liquid towards the first stirring member, while minimizing the energy consumed. In fact, the energy dissipation function is assumed by the first agitation member.

These arrangements make it possible to improve control of the circulation of the mixture to ensure its homogeneity, whatever the viscosity of the mixture during the manufacturing process and while minimizing the energy consumed by the reactor. Caking in the mixture is avoided and the risk of the reaction racing is limited. The stirring system according to the invention which uses shearing also makes it possible to reduce the size of droplets of fatty substances and base forming an emulsion and thus to increase a surface area. of exchange between the fatty substance and the base. It is then no longer necessary to use an additional reagent to facilitate the formation of the emulsion. The soap manufacturing process is simplified and its implementation time reduced. In addition, the properties of the soap can be preserved.

.A ratio of the second pumping number Q ₀ 2 to the second power number P ₀ 2 can be such that $\frac{Q_{0}2}{P_{0}2}\ge 0.3$

.

Each of the blades of the second stirring member may have a median plane between the lower and upper edges, the median plane being inclined at an angle less than 60° relative to a horizontal plane perpendicular to the pivot axis.

The heating system may comprise the side wall of the tank made with a double jacket, and a hot fluid supply source supplying hot fluid to a space between the two envelopes of the side wall of the tank.

The tank may include a bottom from which the side wall extends, the first stirring member being arranged near the bottom of the tank, the second stirring member being arranged at a distance from the bottom of the tank. In the manufacturing process, the mixture can be moved to the bottom of the tank by the second stirring member and moved to the side wall near the bottom of the tank by the first stirring member.

The first stirring member may be a mobile comprising a hub and a plurality of equally distributed blades each extending from the hub to a free end, the hub of the mobile being mounted to pivot relative to the tank along a pivot axis coaxial with the central axis, the first stirring member being a radial pumping mobile. The radial pumping mobile makes it possible to locally create speed gradients rather than pumping the mixture.

• un premier nombre de puissance P01 compris entre 1,5 et 6 où $P_{0}1=\frac{P1}{{{\mathit{\rho N}}_1}^3{D}^5}$
  
  
  avec D diamètre du mobile, en mètres,
  • ρ viscosité du mélange, en Pascals/seconde,
  • P1 puissance dissipée dans la cuve par le premier organe d'agitation, en Watts,
  • N1 vitesse de rotation du premier organe d'agitation, en tours/seconde, et
• un premier nombre de pompage compris entre 0,2 et 1 où $Q_{0}1=\frac{Q1}{N_1{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  

avec Q1, en mètres cubes/seconde, débit passant dans une surface projetée dans un plan perpendiculaire à l'axe de pivotement P du premier organe d'agitation 15.The radial pumping mobile of the first stirring member may have:

• a first power number P01 between 1.5 and 6 where $P_{0}1=\frac{P1}{{{\mathit{\rho N}}_1}^3{D}^5}$
  
  
  with D diameter of the mobile, in meters,
  • ρ viscosity of the mixture, in Pascals/second,
  • P1 power dissipated in the tank by the first stirring member, in Watts,
  • N1 rotation speed of the first stirring member, in revolutions/second, and
• a first pumping number between 0.2 and 1 where $Q_{0}1=\frac{Q1}{{\mathrm{NOT}}_1{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  

with Q1, in cubic meters/second, flow rate passing through a surface projected in a plane perpendicular to the pivot axis P of the first stirring member 15.

The lower edge of each of the blades of the first stirring member can be shaped to present a substantially constant spacing with a part of the bottom of the tank over an essential part of a length of said blade.

The mobile of one and/or the other of the first and second stirring members may have a diameter of between 40% and 80%, preferably between 50% and 70%, of the diameter of the cross section of the tank .

The stirring system may comprise at least one deflection member, such as a counter blade or, in Anglo-Saxon terms, a baffle, arranged near the side wall facing the second stirring member to deflect part of the mixture located near the side wall towards the second stirring member. In the manufacturing process, an upper part of the mixture located near the side wall can be diverted towards the second stirring member by the diverting member.

The figure represents a reactor 1 intended to be used in a soap manufacturing process. In particular, as will appear in the following description, the soap manufacturing process provides for producing a mixture of reagents during different stages to obtain soap.

The reactor 1 comprises a tank 2, preferably heat-insulated and possibly thermostatically controlled, comprising a bottom 3 from which a side wall 4 extends to delimit an interior space 5. In the embodiment shown, the bottom 3 is elliptical and the wall cylindrical side 4 of circular cross section along a central axis A. The interior space 5 has a diameter T and a filling level H. The tank 2 can be dimensioned so that an H/T ratio is between 1.5 and 5. Opposite the bottom 3, the tank 2 has an upper opening 6. The upper opening 6 can be closed by a cover 8. In particular, the cover 8 can be mounted on one edge of the upper opening 6 in a non-hermetic manner to be able to produce mixtures in a so-called “open” tank 2, that is to say whose interior space 5 is at atmospheric pressure.

Alternatively, the tank 2 could have any other suitable shape with preferably a non-flat bottom 3 and in particular a conical bottom.

Tank 2 can be equipped with a heating system not shown. In particular, the tank 2 may have a bottom 3 and a side wall 4 with a double envelope connected to a fluid supply source at an appropriate temperature supplying a space between the two envelopes of the side wall of the tank.

The reactor 1 further comprises a stirring system 10 adapted to circulate the mixture in the interior space 5 of the tank 2, and to shear the mixture at least locally.

In the embodiment shown, the stirring system 10 comprises a shaft 11 extending along the central axis A in the interior space 5 of the tank 2 and through the cover 8. The shaft 11 has a first end 11a connected to a rotation drive device, such as a gear motor 12, and a second end 11b disposed in the vicinity of the bottom 3 of the tank 2. The shaft 11 can thus be driven in proper rotation along an axis of pivoting P coaxial with the central axis A by the drive device 12. The drive device 12 can in particular be adapted to drive the shaft 11 in proper rotation at a rotation speed of up to 80 rpm or more.

The stirring system 10 also comprises a first stirring member 15 mounted on the shaft 11 in the vicinity of the second end 11b. The first stirring member 15 is then pivotally mounted along the pivot axis P relative to the tank 2.

The first stirring member 15, arranged near the bottom 3 of the tank 2, is adapted to shear the mixture, that is to say locally create speed gradients, and to move the mixture transversely relative to the central axis A towards the side wall 4. The first stirring member 15 can be a radial pumping mobile, such as a mobile with straight blades. In particular, the mobile of the first stirring member 15 comprises a hub 16 secured to the shaft 11, and several blades 17, in particular four in the embodiment shown, equally distributed and each extending from the hub 16 to a free end 18. Each of the blades 17 is straight, that is to say it extends in a plane containing the pivot axis P. The mobile of the first stirring member 15 can have a diameter D between 40% and 80%, preferably between 50% and 70%, of the diameter T of the interior space 5 of the tank 2.

The shape of the mobile of the first stirring member 15 can also be adapted to follow the shape of the bottom 3 of the tank 2. In particular, each of the blades 17 can have a lower edge 19 facing the bottom 3 of the tank 2. shaped to present a substantially constant spacing c1 with a part of the bottom 3 of the tank 2 on an essential part, that is to say 50% or more, of a length of the blade 17 measured between the hub 16 and the free end 18. The spacing c1 between the lower edge 19 of each of the blades 17 and the bottom 3 of the tank 2 can be between 5% and 20% of the diameter T of the interior space 5 of the tank 2.

• un premier nombre de puissance $P_{0}1=\frac{P1}{{{\mathit{\rho N}}_1}^3{D}^5}$
  
  
  avec ρ viscosité du mélange, en Pascals/seconde,
  • P1 puissance dissipée dans la cuve par le premier organe d'agitation 15, en Watts,
  • N1 vitesse de rotation du premier organe d'agitation 15, en tours/seconde,
• un premier nombre de pompage $Q_{0}1=\frac{Q1}{N_1{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  

avec Q1, en mètres cubes/seconde, débit passant dans une surface projetée dans un plan perpendiculaire à l'axe de pivotement P du premier organe d'agitation 15.The mobile of the first stirring member 15 has:

• a first power number $P_{0}1=\frac{P1}{{{\mathit{\rho N}}_1}^3{D}^5}$
  
  
  with ρ viscosity of the mixture, in Pascals/second,
  • P1 power dissipated in the tank by the first stirring member 15, in Watts,
  • N1 rotation speed of the first stirring member 15, in revolutions/second,
• a first pumping number $Q_{0}1=\frac{Q1}{{\mathrm{NOT}}_1{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  

with Q1, in cubic meters/second, flow rate passing through a surface projected in a plane perpendicular to the pivot axis P of the first stirring member 15.

The first power number P01 of the radial pumping mobile of the first stirring member 15 is high, for example between 1.5 and 6, so as to promote shearing. The first pumping number Q01 of the radial pumping mobile of the first stirring member 15 can be low, for example between 0.2 and 1.

The power dissipated per cubic meter of mixture is between 1000 W/m3 and 8000 W/m3, preferably between 2000 W/m3 and 6000 W/m3.

Alternatively, the mobile of the first stirring member 15 could be a Rushton turbine or any other radial flow mobile.

The stirring system 10 also comprises a second stirring member 25 mounted on the shaft 11 on the side of the first end 11a, below the filling level H. The second stirring member 25 is then arranged coaxially at the above the first stirring member 15. The second stirring member 15 is thus mounted to pivot along the pivot axis P relative to the tank 2.

The second stirring member 25, arranged at a distance from the bottom 3 of the tank 2, is adapted to move the mixture in a pumping direction S, indicated by an arrow in the figure. In the embodiment shown, so that the mixture can be moved towards the first stirring member 15, the pumping direction S is along the central axis A of the tank 2 and oriented towards the bottom 3 of the tank 2. The second stirring member 20 can be a mobile unit with downward axial pumping, such as a propeller with inclined blades. In particular, the mobile of the second stirring member 25 comprises a hub 26 secured to the shaft 11, and several blades 27, in particular four in the embodiment shown, equally distributed and each extending from the hub 26 to a free end 28. Each of the blades 27 is inclined, that is to say it deviates from a plane containing the pivot axis P. The blade 27 has a median plane with respect to the first 29 and second 30 opposite edges along the pivot axis P. The first edge 29 is located near the first stirring member 15 and the second edge 30 is located at a distance from the first stirring member 15. In the embodiment shown, taking into account the arrangement of the first 15 and second 25 stirring members, the first edge 29 is a lower edge and the second edge is an upper edge. The median plane makes an angle with a horizontal plane perpendicular to the pivot axis P. This angle is less than 60°, for example 45° in the figure, with an inclination such that the upper edge 30 is in front of the lower edge 29 with respect to a direction of rotation R of the shaft 11, shown by an arrow, and therefore of the mobile of the second stirring member 25. In the embodiment shown, the mobile of the second stirring member 25 has a diameter D identical to that movable of the first stirring member 15. Alternatively, the movable of the second stirring member 25 could have any other diameter between 40% and 80%, preferably between 50% and 70%, of the diameter T of interior space 5 of tank 2.

• un deuxième nombre de puissance $P_{0}2=\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}2}{{{\mathit{<figure-callout\; id="2"\; label="\rho N"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\rho N</figure-callout>}}_2}^3{D}^5}$
  
  
  avec P2 puissance dissipée dans la cuve par le deuxième organe d'agitation 25, en Watts,
  N2 vitesse de rotation du deuxième organe d'agitation 25, en tours/seconde,
• un deuxième nombre de pompage $Q_{0}2=\frac{Q2}{N_2{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  

avec Q2, en mètres cubes/seconde, débit passant dans une surface projetée dans un plan perpendiculaire à l'axe de pivotement P du deuxième organe d'agitation 25.The mobile of the second stirring member 25 has:

• a second power number $P_{0}2=\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}2}{{{\mathit{<figure-callout\; id="2"\; label="\rho N"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\rho N</figure-callout>}}_2}^3{D}^5}$
  
  
  with P2 power dissipated in the tank by the second stirring member 25, in Watts,
  N2 rotation speed of the second stirring member 25, in revolutions/second,
• a second pumping number $Q_{0}2=\frac{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Q</figure-callout>}2}{{\mathrm{NOT}}_2{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}}^3}$
  

with Q2, in cubic meters/second, flow rate passing through a surface projected in a plane perpendicular to the pivot axis P of the second stirring member 25.

.The second pumping number of the axial pumping mobile of the second stirring member is high, that is to say between 0.5 and 2, so as to promote the implementation traffic. The second power number of the axial pumping mobile of the second stirring member is low, that is to say between 0.3 and 1.5. A ratio of the second pumping number Q ₀ 2 to the second power number P ₀ 2 is preferably such that $\frac{Q_{0}2}{P_{0}2}\ge 0.3$

.

The power dissipated per cubic meter of mixture between 1000 W/m3 and 8000 W/m3, preferably between 2000 W/m3 and 6000 W/m3.

The invention is not limited to the stirring system 10 described above and could in particular include any other type of stirring member, in appropriate number, in particular between two and five, preferably between two and three, and according to all appropriate arrangement. For example, the stirring system 10 could comprise two second stirring members, for example identical, mounted coaxially on the shaft above the first stirring member.

The stirring system 10 may also include one or more diversion members 35, for example between two and four, preferably between two and three, arranged to divert a part of the mixture located near the side wall 4 of the tank 2 towards the second stirring member(s) 25. The deflection members 35 can be removably mounted in the interior space 5 of the tank 2. In the embodiment shown, as deflection members 35, the stirring system 10 comprises two counter-blades 36 or, in Anglo-Saxon terms, baffles, arranged near the side wall 4 of the tank 2 facing the free ends of the mobiles of the second stirring members 25. The counter-blades 36 can be removable and pivoting around a longitudinal axis L to allow its orientation to be changed. The counter-blades 36 can have a width lb of between 3% and 8% of the diameter T of the interior space 5 of the tank 2. Furthermore, the counter-blades 36 can be arranged so as to leave a free space with the side wall 4 of the tank 2 between 2% and 8% of the diameter T of the interior space 5 of the tank 2.

According to the arrangement proposed in the particular embodiment, the radial pumping mobile of the first stirring member 15 is arranged downstream of the axial pumping mobile of the second stirring member 25 with respect to the pumping direction S. The mixture can thus be moved in the pumping direction S along the central axis A towards the bottom 3 of the tank 2 by the axial pumping mobile of the second stirring member 25 towards the radial pumping mobile of the first stirring member 15 , and sheared and moved transversely with respect to the central axis A towards the side wall 4 by the radial pumping mobile of the first stirring member 15. The mixture can thus return towards the mobile with axial pumping of the second stirring member 25 while being deflected towards this mobile by the counter-blades 36.

The use of a reactor equipped with a mechanical stirring system, making it possible in particular to simultaneously shear and pump the mixture, makes it possible to ensure the homogeneity of the mixture throughout the soap manufacturing process.

• l'étape a. d'empâtage et cuisson peut être conduite à des températures comprises entre 75 et 99°C sur une durée environ deux fois moins longue que les procédés traditionnels,
• l'étape b. de lavage peut être conduite à des températures comprises entre 70 et 99°C, et le nombre de lavages et la quantité d'eau de lavage peuvent être réduits.

This reduces water consumption, contact times between reagents and reaction temperatures. It follows that :

• step a. mashing and cooking can be carried out at temperatures between 75 and 99°C for a period approximately half as long as traditional processes,
• step b. washing can be carried out at temperatures between 70 and 99°C, and the number of washes and the amount of wash water can be reduced.

These gentler operating conditions therefore make it possible to reduce energy consumption and emissions. And they also make it possible to guarantee the integrity of the high quality fatty substances or oils used and to limit the formation of impurities resulting from the degradation of these oils or fatty substances at high temperature and thus to ensure the good quality of the soap

Drying and finishing

According to a particular embodiment, step c. of the process of the invention can be followed by a step of drying the smooth soap until obtaining a soap comprising at most 22% by weight of water, in particular at most 16% by weight of water.

Drying can preferably be carried out by passing the smooth soap through a vacuum atomizer in which the soap is sprayed. Any other system using natural or forced convection, heated or not, of ambient air or a carrier gas can also be used as a drying means. So the soap can, for example, also be poured onto the ground and dried in the open air.

Once dried, the soap can be shaped, for example by passing it through serial extruders in which it is compressed. Then the soap leaves the extruders through a die which allows obtaining the desired shape for the finished product. he can alternatively be shaped by cutting, for example when the soap has been dried on the ground in particular. The soap can also be shaped by molding.

Soap

1. a. une étape d'empâtage et de cuisson dans laquelle :
   • on mélange au moins un acide gras et/ou ester d'acide gras avec une solution aqueuse de soude,
   • on chauffe le mélange pour obtenir une pâte de savon,
2. b. au moins une étape de lavage de la pâte de savon obtenue à l'étape a. dans laquelle :
   • la pâte de savon est mélangée avec une solution aqueuse comprenant 1 à 42% en poids d'un mélange de soude et de sel,
   • le mélange est chauffé, et laissé à décanter jusqu'à formation de deux phases : le savon grainé comprenant du sel, de la soude et de la glycérine, et une solution aqueuse comprenant du sel, de la soude et de la glycérine,
   • le savon grainé et la solution aqueuse sont séparés,
3. c. une étape de lissage du savon grainé obtenu à l'étape b. par neutralisation dans laquelle :
   • le savon grainé est mélangé avec au moins un agent de neutralisation pouvant être un acide, un acide gras ou un ester d'acide gras,
   • le mélange est chauffé, et le savon lisse est obtenu.

The invention also relates to a smooth soap capable of being manufactured by means of a discontinuous soap manufacturing process comprising at least the following steps:

1. has. a mashing and cooking step in which:
   • at least one fatty acid and/or fatty acid ester is mixed with an aqueous sodium hydroxide solution,
   • the mixture is heated to obtain a soap paste,
2. b. at least one step of washing the soap paste obtained in step a. in which :
   • the soap paste is mixed with an aqueous solution comprising 1 to 42% by weight of a mixture of soda and salt,
   • the mixture is heated, and left to decant until two phases are formed: the grained soap comprising salt, soda and glycerin, and an aqueous solution comprising salt, soda and glycerin,
   • the grained soap and the aqueous solution are separated,
3. vs. a step of smoothing the grained soap obtained in step b. by neutralization in which:
   • the grained soap is mixed with at least one neutralizing agent which may be an acid, a fatty acid or a fatty acid ester,
   • the mixture is heated, and smooth soap is obtained.

• au plus de 33% en poids d'eau, de préférence 25% à 33% en poids, plus préférentiellement 24% à 32% en poids d'eau,
• au plus 0,7% en poids de sel, de préférence 0,1% à 0,6%, plus préférentiellement 0,35 à 0,5 %, plus particulièrement 0,2% à 0,5% en poids de sel, et
• au plus 0,2% en poids de soude, de préférence 0,05% à 0,2%, plus préférentiellement 0,05% à 0,1% en poids de soude libre (sous forme NaOH).

The smooth soap thus obtained preferably comprises:

• at most 33% by weight of water, preferably 25% to 33% by weight, more preferably 24% to 32% by weight of water,
• at most 0.7% by weight of salt, preferably 0.1% to 0.6%, more preferably 0.35 to 0.5%, more particularly 0.2% to 0.5% by weight of salt, And
• at most 0.2% by weight of soda, preferably 0.05% to 0.2%, more preferably 0.05% to 0.1% by weight of free soda (in NaOH form).

The invention is illustrated in more detail in the following illustrative and non-limiting example.

EXAMPLE

A smooth soap was prepared according to the following process:
360g of olive pomace oil, 120g of coconut oil and 120g of palm oil were introduced into a double-jacketed reactor equipped with a mechanical stirring system making it possible to simultaneously shear and pump the mixture.

Agitation is started at a speed of 500 rpm. The reactor is heated to a temperature of 78°C.

326g of a 27% aqueous sodium hydroxide solution and 2.1% brine are added in one go to the reactor.

The mixture is kept stirring at 650 rpm at a temperature of 87°C for 4h30.

Dosing the sodium hydroxide by titration with hydrochloric acid after 4.5 hours confirmed that the saponification reaction was complete.

197 g of an aqueous solution comprising 5% salt and 6.8% sodium hydroxide were then introduced into the reactor, still stirring at 650 rpm at a temperature of 87°C, and stirring was maintained at this temperature for 35 min. .

After 35 minutes, stirring was stopped, and the mixture was allowed to settle for 1 hour until at least two phases were formed at 87°C.

The lye comprising water, soda and salt and glycerin was then drawn off. We left it to settle again for 1 hour 20 minutes at 87°C and then the lye comprising water, soda and salt and glycerin was drawn off again. We thus recovered 139g of withdrawn detergents.

The yield is therefore 70.55%.

We then proceeded to smooth the soap. To do this, 24.7 g of coconut oil were introduced into the double-jacketed reactor equipped with a stirring system containing the grained soap previously obtained.

The mixture is kept stirring at 650 rpm at a temperature of 95°C for 30 min.

The smooth soap is then poured and air dried

The soap obtained is perfectly homogeneous and can benefit from the name Marseille soap. It forms a particularly creamy foam, and the moisturizing glycerin protects the skin.

Claims (16)

1. A discontinuous method for manufacturing soap comprising at least the following steps:

   a. a step of mashing and cooking in which:

   - at least one fatty acid and/or fatty acid ester is mixed with an aqueous soda solution,

   - the mixture is heated to obtain a soap paste,

   b. at least one step of washing the soap paste obtained in step a. in which:

   - the soap paste is mixed with an aqueous solution comprising 1 to 42% by weight of a mixture of soda and salt,

   - the mixture is heated, and left to decant until two phases are formed: the grained soap comprising salt, soda and glycerine, and an aqueous solution comprising salt, soda and glycerine,

   - the grained soap and the aqueous solution are separated,

   c. a step of smoothing the grained soap obtained in step b. by neutralisation in which:

   - the grained soap is mixed with at least one neutralising agent which may be an acid, a fatty acid or a fatty acid ester,

   - the mixture is heated, and the smooth soap is obtained.
2. The method according to the preceding claim, wherein the fatty acid and/or the fatty acid ester implemented in step a. is a fatty substance of plant origin, preferably, a plant or plant origin oil or pasty, .
3. The method according to the preceding claim, wherein the fatty substance, in particular the oil, is refined.
4. The method according to any one of claims 2 or 3, wherein the plant oil is olive oil, in particular acid oil from olive pomace, coconut oil, palm oil or a mixture thereof.
5. The method according to any one of the preceding claims, wherein the aqueous soda solution implemented in step a. comprises a soda content ranging from 20% to 31% by weight of soda, preferably from 25% to 30% by weight.
6. The method according to any one of the preceding claims, wherein steps a. , b. and/or c. are implemented in a reactor provided with a mechanical stirring system, said mechanical stirring system of the reactor allows simultaneously shearing and pumping the mixtures of steps a. , b. and/or c..
7. The method according to any one of the preceding claims, wherein the reactor is a double-jacketed reactor.
8. The method according to the preceding claim, wherein, in step a., the mixture is heated so that the temperature thereof is comprised between 60 and 110°C, in particular between 75 and 99°C, more particularly between 80°C and 90°C, for a period of 1h to 6h, preferably from 2h to 5h.
9. The method according to any one of the preceding claims, wherein the aqueous washing solution comprises:

   - 1 to 7% by weight of salt, preferably 2 to 5% by weight of salt, more preferably 2 to 4% by weight of salt, and

   - 0.01% to 40% by weight of soda, preferably 0.9% to 20% by weight of soda, more preferably from 2% to 8% by weight of soda.
10. The method according to any one of claims 7 to 9, wherein, in step b., the mixture is heated to a temperature comprised between 70 and 99°C, preferably between 80 and 99°C for 30 min to 2 days, preferably for 45 min to 24h, and more preferably for 1h to 18h.
11. The method according to any one of claims 7 to 10, wherein, in step c., the mixture is heated to a temperature comprised between 70 and 99°C, preferably between 80 and 99°C for 10min to 5h, preferably for 30min to 2h.
12. The method according to any one of the preceding claims, comprising at most two washing steps, preferably at most one washing step.
13. The method according to any one of the preceding claims, wherein the step c. is followed by a step of drying the smooth soap until obtaining a soap comprising at most 22% by weight of water, in particular at most 16% by weight of water.
14. The method according to the preceding claim, wherein the drying step is followed by a finishing step comprising shaping the soap, for example by moulding.
15. A smooth soap likely to be manufactured by means of the method according to any one of claims 1 to 14, characterised in that it comprises between 1 and 8% by weight of glycerine relative to the weight of the smooth soap.
16. The smooth soap according to the preceding claim, comprising:

    - at most 33% by weight of water, preferably 25% to 33% by weight, more preferably 24% to 32% by weight of water,

    - at most 0.7% by weight of salt, preferably 0.1% to 0.6%, more preferably 0.35 to 0.5%, more particularly 0.2% to 0.5% by weight of salt, and

    - at most 0.2% by weight of soda, preferably 0.05% to 0.2%, more preferably 0.05% to 0.1% by weight of free soda.

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