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Soaps are inexpensive anionic surfactants. Hard soaps are based on sodium salts. Soft soaps are based on potassium salt.

Soaps are inexpensive anionic surfactants. Hard soaps are based on sodium salts. Soft soaps are based on potassium salt.

amixon® mixers and reactors in oleochemistry for the production of detergents and metal soaps

Oleochemistry influences the quality of products as diverse as cosmetics, plastics, rubber, food, surface protection, paper, pharmaceuticals, lubricants, ....

In the production of detergents and metal soaps, many specific requirements are placed on the mixers/synthesis reactors. amixon equipment fulfills these special tasks in an exemplary manner.


Soaps are potassium salts and sodium salts of fatty acids. Soap is one of the oldest chemical products. Even primitive peoples knew about the lubricating and separating effect of soap. They used the ash from burnt wood and mixed it in water to make a diluted lye. They strained the ash residue from the liquid phase and vaporized it. Thus, they concentrated the weak lye and mixed it with oil and fat - preferably in a heated state. The onset of turbidity is an indication of the formation of soap suds, which has fat- and water-solving properties.   Ideally, the more solid components of the soapsuds were separated from the more liquid ones. This made them easier to store and transport.   This method was used by the Sumerians as early as 3000 BC, using the soap substance for healing purposes.

amixon® mixers, vacuum dryers and synthesis reactors for the production of magnesium stearate, calcium stearate and sodium stearate

Soaps are not only used for cleaning, but also as a lubricant in the moulding of metallic materials, e.g. in the thermoforming of bathtubs or car chassis. They are also used in "cold deep drawing" and in the downstream processing of tubes.  So-called metal soaps such as magnesium stearate, calcium stearate and sodium stearate, simplified also called stearates, are formed during the esterification of stearic acid in the presence of metal oxides/hydroxides with cleavage of glycerol.

The term "metallic soaps" refers to all soaps that neither contain sodium nor potassium salts. As a waxy white powder, they are not soluble in water. They also find application as additives in the production of medicines and cosmetics, as well as in animal feed.    They are effective anti-caking agents in food production.

European patent specification 0330 097 specifies processes for producing powdered basic metal soaps based on stearic acid. It is shown that with correct temperature control and the use of a suitable mixing system, metal soaps result as finely dispersed, free-flowing, light-colored powders. After a spontaneous change of phase from liquid to solid, the product is vacuumed for drying. Other patent specifications, such as the German patent application DE4019167A1, explain the production of powdered basic-neutral metal soap in the form of a two-step process with the aim of obtaining a low-dust, flaky, free-flowing powder.

amixon® conical processing units are also designed and manufactured according to the customer's specific requirements.

The production chain for metal soaps is highly complex and very individually shaped by company-specific process philosophies. The process step "powder mixing" is important at several points: first for the collection and preparation of the raw materials and then for carrying out the syntheses. The hydroxides of the metals mentioned are introduced in powder form, along with suitable oils and fats. The mass is heated and homogenized to a low-viscosity suspension, which becomes a viscous paste after adding small amounts of a catalyst or heating the mass. The reaction then continues with the reactor vessel closed, with strong heat generation, and the system pressure increases to values that are many times higher than the ambient pressure. After the reaction is complete, the synthesis reactor is evacuated to dry and cool the mass. The end result is a white, finely dispersed powder.

Cleansing effect of soap

It was not until Roman times that the cleansing effect of soap was cultivated. Roman writings mention the Germanic soap, which consisted of tallow, ash and plant juices. It was used to dye the skin and hair red before the fight. The art of soap boiling is said to have been passed on from the Arabs to the Spaniards, and Charlemagne encouraged the settlement of soap boilers in the Franconian Empire during his reign from 768 to 814. Old German terms such as Seifa, Seipha or Säpa for soft soap have been handed down. The production of hard white soap was considered special and was favored by the use of marine plants and olive oil as raw materials. Infused with medicinal herbs, antioxidants, deodorants and fragrance oils, soap was a coveted luxury item.

Around 900, Marseille was a stronghold of soap production. Five centuries later, it was the Italian cities of Savona, Venice and Genoa. King Louis XVI (reigned 1775 to January 21, 1793) issued a quality guideline for soap in France:   The oil content had to be at least 72 percent by weight.

amixon® Continuous mixer for powder detergents

In this plant, heavy-duty detergents, color detergents and mild detergents are filled. High-performance filling lines must operate as uninterruptedly as possible. The material supply must be continuous. A continuous mixer from amixon® reliably fulfills this task. In this case, the mixing principle of continuous boiler flow applies. This continuous mixer can mix up to five solid streams. The various components are metered from the top according to the recipe, mixed in the mixer and discharged to the bottom. This continuous mixer can feed 1, 2 or 3 filling machines simultaneously.

The use of an amixon® mixer ensures particularly gentle homogenization. The particles of the mixture retain their structure and size. At the end of a production campaign, the mixer can discharge completely automatically if the mixing tool is equipped with ComDisc® tools.

The amixon® vertical mixer functions as a continuous mixer with three discharge nozzles.

The amixon® vertical mixer functions as a continuous mixer with three discharge nozzles. One amixon® mixer simultaneously supplies up to three high-speed packaging machines.

Historical print from the 19th century: development and production of soaps.

Historical print from the 19th century: development and production of soaps.

Early industrial production

Around 1900, industrial processes replaced potash with artificial soda ash as well as the strong alkalis sodium hydroxide and potassium hydroxide. The basic chemicals perborate and silicate gave rise to Henkel's Persil brand product in 1907. In 1929, Benckiser developed a dishwashing detergent for the hotel and restaurant industry in Ludwigshafen. Curd soap became a mass product. To this day, great efforts have been made to make detergents more environmentally friendly. For example, the enzymes and surfactants used in modern detergents are biodegradable, microplastics, phosphates and bleaching agents are not used.

In addition to the foaming and washing capacity, the phenomenon of "soap skin" should be mentioned. In this process, the property of soap forming a surface film is utilized. If a spatially irregularly curved wire loop is dipped into a soap solution and lifted, a soap skin is formed. The area stretched in this way represents the minimum surface area. The irregularly shaped roofs of the Olympic tents in Munich were optimized using this method.

amixon® twin-shaft mixer HM 5000 for mixing coated "exploder powders" into washing-active substances.

amixon® twin-shaft mixer HM 5000 for mixing coated "exploder powders" into washing-active substances. Exploders swell spontaneously in the presence of water. This causes the dishwasher tabs to burst at a predefined time.

This amixon® twin-shaft mixer mixes batchwise

Another specialty concerns the final mixing of dishwasher detergent tabs / compacts. These consist of different formulations, which are often colored differently. They indicate advanced functions and stand for "grease remover", "rinse aid", "extra-dry effect", "cleaning booster", "water softener" or even "drugstore tab". High-performance tablet presses are capable of forming tabs from different colored tablet parts.

This requires that the various washing powders are mixed in such a way that their particle shape is maintained. The specific flow and cohesion properties must also be maintained. In order to maintain the function of so-called exploders, mixing must be extremely gentle. Such batch mixers must work largely self-cleaning and self-discharging.

Special application: Continuous agglomeration with increased energy input

Powder detergents are sometimes post-treated to densify them. This saves transport costs and packaging material. Continuously operating mixing granulators produce round agglomerates from a powdery washing-active substance by build-up granulation. In most cases, small amounts of a liquid binder are added. The amount of liquid should be as small as possible to avoid subsequent thermal drying. The previously powdery-dusty bulk material is then granular and low in dust. Agglomerated bulk materials are generally easy to dose and fill.

Ideal mixing quality with minimum energy input

The commercial importance of soap extends to its washing-active property as a detergent for personal care, clothing, dishes and household cleaning in liquid and solid form as powder, granules, ball or tablet. A completely different field of application extends to the industrial applications of stearates.

A look at the product range of major stearate manufacturers shows how broad the application spectrum of metal soaps is: Calcium stearates and zinc stearates are effective stabilizers in plastic production and allow the use of PVC for drinking water pipes. The PVC plastic is stabilized against washout. Calcium stearate is also used as a lubricant additive in rolling bearings.

The stearates of the metals zinc, sodium, barium, lithium and aluminum have very different efficacies in different compositions: For example, as a chemical acid scavenger, as an impregnating agent, as a vulcanization aid for rubber, as a lubricant in metal processing, as a hydrophobizing agent in the manufacture of building materials, as a release agent or adhesion promoter, as an abrasive when lapping surfaces or as a matting agent for paint lacquers, as a thickener/emulsifier in creams, shampoos and foods, for hydrophobizing absorbent materials.

With a particle size of 3 to 15 µm, magnesium stearate has a very large surface area and, in the smallest concentrations, serves as an effective flow aid for bulk materials of all kinds. However, it is important that the mixing process is gentle and precise. High shear mixing reduces the flowability. Without magnesium stearate, the production output of today's tablet presses would be unthinkable.

amixon® KoneSlid® mixer size KS 2600 for extremely gentle powder mixing with minimum mixing time.

amixon® KoneSlid® mixer size KS 2600 for extremely gentle powder mixing with minimum mixing time. This mixer empties free-flowing bulk materials completely within a few seconds.


amixon® mixers

  • amixon® machines are able to achieve a technically ideal mixing quality in a short time with minimum energy input, which cannot be further improved in practice.
  • Since the metallic soaps consist of very fine powder, the risk of dust explosion is increased. amixon® mixers are certified according to Atex type testing.
  • In the amixon® mixer, ideal mixing quality is achieved even at peripheral speeds of the mixing tool of less than 1 m/s.
  • The powder derivatives of oleo chemistry usually have poor flow properties. amixon® mixers are capable of mixing even poorly flowing powders homogeneously and discharging them completely.
  • amixon® mixers can be used flexibly. They mix equally well even at low filling levels.
  • amixon® mixers have large inspection doors. They are easily accessible when manual cleaning is required.
  • amixon® mixers are permanently gas-tight. This is especially important when the mixing chamber is inerted with nitrogen.

amixon® vacuum dryers/ synthesis reactors

  • Thermal processes work more effectively the more heat exchange surface is available. amixon® processing equipment can be heated and cooled over its entire surface: Mixing shaft, static mixing tools, mixing arm and mixing helix, and the entire mixing chamber.
  • The consistency of the mixing goods can vary depending on the reaction process: liquid, semi-solid, highly viscous or powdery. amixon® devices mix ideally and effectively in every phase.
  • Frequent load changes lead to material fatigue. This is especially true when process temperatures change frequently and rapidly. amixon® has decades of experience and is able to design and manufacture apparatus in such a way that they still have a long service life.
amixon® mixing dryer synthesis reactor universally applicable.

amixon® mixing dryer synthesis reactor universally applicable.

Use the amixon® test machines for your process optimization!

amixon has gained extensive experience in various fields of synthesis reaction control since 1983 and offers users a comprehensive range of process machines with vertically mounted helical mixing tools.

In the amixon test center, 20 different vertical mixing systems and 4 different synthesis reactors are available for trials. Tests in the pilot plant usually deliver first-class results.

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