The invention is a continuous process for preparing a cosmetic or dermatological preparation, comprising emulsifying at least two pre-products in at least one mixing apparatus, cooling the emulsion to less than 40.degree. C. by adding an aqueous phase with a lower temperature than the mixture, adding at least one ingredient selected from the group consisting of perfume oil and temperature-sensitive active ingredients, and homogenizing the emulsion in at least one homogenizing apparatus at a temperature of from 20 to 50.degree. C. The invention also includes a product made by such process.

Description of the Invention

FIELD OF THE INVENTION

The present invention relates to a process for the preparation of cosmetic or dermatological preparations, in particular of preparations comprising emulsions, PIT emulsions and washing-active substances.

BACKGROUND OF THE INVENTION

Cosmetic or dermatological preparations in the form of emulsions, PIT emulsions and preparations comprising washing-active substances are widespread. Emulsions may be W/O or O/W emulsions or else multiple emulsions, i.e. emulsions containing more than two phases. They are sold in the form of creams, lotions, but also as perspiration-inhibiting, body-odour-reducing cleansing and sunscreen preparations. PIT emulsions are particular forms of emulsions. They are characterized by the method of their preparation and the droplet sizes resulting therefrom. For the preparation, emulsifiers or emulsifier systems are used which change their polarity depending on the temperature, meaning that phase inversion arises during the preparation. As a result of this phase inversion, particular product properties are achieved, such as, for example, a particular optical appearance or an extraordinarily low viscosity. Such preparations are suitable, for example, as sprayable skincare or sunscreen emulsions. Finally, preparations comprising washing-active substances are used as body- or hair-cleansing compositions, and also as dishwashing detergents.

Usually, such preparations are prepared in a batchwise process, mostly in a mixer into which the starting substances are introduced and the intermediate or end product are removed after a certain operating time. In this process, all of the process steps which are required for the preparation of the product take place in this one apparatus one after the other: metering, mixing, heating/cooling, emulsifying, cooling. Often, upon removing the product, the product is subjected to subsequent homogenization. Although in food technology continuous plants for the preparation of emulsions such as yoghurt or mayonnaise are widespread, cosmetic or dermatological preparations are only prepared continuously in exceptional cases. This is because the requirements on the stability of cosmetic products are much higher and, due to their more complex composition comprising numerous different components, said products are much more difficult to prepare in stable form. Thus, for example, for a yoghurt, a stability in the region of a few weeks is expected, whereas cosmetic emulsions should be stable over at least 30 months.

Plants which are operated in batchwise processes have a series of disadvantages besides the advantageous flexibility with regard to the products which can be prepared. The long batch times required lead to increased production costs. There is a risk of contamination since the plants have to be emptied and charged frequently. The risk of contamination can be limited by keeping the product temperatures low. This is achieved by using cold aqueous phases. Alternatively, a heat exchanger can also be connected downstream. In most cases, relatively large amounts of air are introduced into the system, which is undesirable.

Known continuous processes are characterized in that the individual phases are metered into a high-performance emulsifying device at the same time. The emulsification and homogenization operation takes place therein with a high input of energy, giving rise to high shear forces. However, the occurrence of high shear forces is able to damage polymers present in the preparations. As a result of simultaneously metering all of the components, they are subjected to relatively high temperatures over prolonged periods. As a result, the use of temperature-sensitive substances is only possible to a limited degree. Such substances are, for example, cosmetic active and functional ingredients, such as fragrances, vitamins, coenzymes, peptides, enzymes, nucleic acids, plant extracts, preservatives, such as, for example, those from 1,2-dibromo-2,4-dicyanobutane and 2-phenoxyethanol.

Although continuous plants with which it is possible to prepare a large number of different cosmetic and/or dermatological preparations are desired, they are not known to date. In particular, a plant with which it would be possible to prepare both low-viscosity emulsions, lotions, creams and body- and hair-cleansing preparations and also dishwashing detergents would represent a significant improvement in the prior art.

It has hitherto not been possible to prepare PIT emulsions in continuous processes since the droplets remain too large despite a high input of energy. Continuously prepared creams and liquid emulsions were in most cases insufficiently stable. During the preparation of preparations comprising washing-active substances, the use of continuous processes in most cases leads to inhomogeneities arising as a result of inadequate mixing. Transparent preparations are therefore only obtainable with difficulty since such inhomogeneities often lead to clouding. For the preparation of O/W emulsions, continuous processes have hitherto not been able to penetrate the market since it has not been possible to achieve products of high quality: in most cases the emulsions were not stable or tended towards oil losses. The cause of this behaviour is assumed to be the fact that homogeneous droplet size distributions cannot be achieved through the use of static mixers on their own.

The article "Eine Anlage zum kontinuierlichen Emulgieren" [A continuous emulsification plant] in the Journal Verfahrenstechnik, volume 1-2 from 1986 describes, for example, a continuous preparation process for the preparation of W/O and O/W creams. The discontinuously prepared preproducts pass through a metering system, a dynamic mixer and a static mixer. Here, a hot/cold process is realized in which the preproducts enter the process in cold or hot form. The emulsion is produced in the dynamic mixer, homogenization takes place in the static mixer, as a result of which the particle size distribution is adjusted. This plant is suitable for the preparation of skin creams, body lotions, mayonnaise and sauces.

In this process, the homogenization operation takes place at 40 to 75.degree. C., although it would be desirable to carry out this step at low temperatures since temperature-sensitive constituents of the formulations, such as odour or aroma substances or active ingredients such as vitamins, should as far as possible not be subjected to thermal stress.

SUMMARY OF THE INVENTION

Starting from this, it was an object of the present invention to find a process which overcomes the disadvantages of the prior art.

It has been found, in a manner unforseen by the person skilled in the art, that a continuous preparation process, as shown in FIG. 1 (see Original Patent), for cosmetic or dermatological preparations which comprise temperature-sensitive ingredients characterized by a sequence of the following process steps (a) emulsification in mixing apparatuses (11), (b) establishing a mixture temperature of less than 40.degree. C. by adding (B) aqueous phase with a lower temperature compared with the mixture, (c) addition (C) of perfume oil and/or temperature-sensitive active ingredients, (d) homogenization in apparatuses (13) in the temperature range from 20 to 50.degree. C., particularly preferably 28 to 40.degree. C., overcomes the disadvantages of the prior art. Likewise, a preparation process for cosmetic or dermatological preparations which comprise temperature-sensitive ingredients, as shown in FIG. 2 (see Original Patent) and characterized in that (1) it is carried out continuously and (2) by a sequence of the following process steps (a) emulsification in mixing apparatuses (30), in combination with static mixers (28, 11) and/or homogenizers (29, 33), (b) establishing a mixture temperature of 55-35.degree. C. by adding (P,Q) aqueous phase of 15-50.degree. C. with a lower temperature compared with the mixture, (c) addition (R,S) of perfume oil and/or temperature-sensitive active ingredients at different temperatures, (d) homogenization in apparatuses (29, 33) in the temperature range from either 50 to 80.degree. C., particularly preferably 60 to 70.degree. C. or 20 to 50.degree. C., particularly preferably 28 to 45.degree. C., very particularly preferably 30 to 40.degree. C., (e) stepwise (stagewise) cooling during the process (32, 34), also remedies the disadvantages of the prior art. It is particularly preferred here when the entering preproducts have been heated beforehand to temperatures of from 40 to 100.degree. C., particularly preferably 50 to 90.degree. C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this connection, it is preferred when, as a further downstream step (14), as shown in FIG. 1 (see Original Patent) or (32, 34), as shown in FIG. 2 (see Original Patent), the process product is cooled to at most 28 to 30.degree. C. It is also preferred when the preproducts are mixed at temperatures of from 40 to 100.degree. C., particularly preferably 50 to 90.degree. C. before they enter the first mixing or homogenization apparatus. In addition, it is preferred when, upon passing through the homogenization apparatus (13), as shown in FIG. 1, the temperature of the exiting mixture increases 2 to 60.degree. C., or upon passing through the homogenization apparatus (29, 33), as shown in FIG. 2, the temperature of the exiting mixture increases 2 to 10.degree. C., based on the temperature of the entering mixture.

It is particularly preferred when the emulsification operation is carried out in two different mixing apparatuses (10) and (11), as shown in FIG. 1. It is very particularly preferred when the emulsification operation is carried out in a static mixer (10) and a loop mixer (11) (FIG. 1) or (29) and (33) (FIG. 2).

It is particularly preferred when the homogenization operation is carried out in a loop mixer (30) and a homogenizer (33), as shown in FIG. 2.

It is particularly preferred when the homogenization operation is carried out in two different apparatuses (12) and (13), as shown in FIG. 1. It is very particularly preferred when the homogenization operation is carried out in a static mixer (12) and a homogenizer (13).

It is very particularly preferred when the emulsification operation is carried out in a loop mixer (30) in combination with one or more homogenizers (29, 33), and static mixers (28, 31), as shown in FIG. 2.

The invention also covers emulsions, PIT emulsions and products comprising washing-active substances, obtainable by a process according to at least one of the variants described. Preferably, such emulsions, PIT emulsions and products comprising washing-active substances comprise, or are used in such processes as, temperature-sensitive ingredients, such as fragrances, vitamins, coenzymes, peptides, enzymes, nucleic acids, plant extracts, preservatives.

Through the process according to the invention it is possible to achieve particularly high throughput capacities of the plants used: to date, the capacity limits of customary plants were 3 t/h, whereas with the plant according to the invention up to 10 t/h can be achieved. In this regard, the process is very universally suitable for completely different types of product groups: besides W/O and O/W emulsions, PIT emulsions and products comprising washing-active substances can also be prepared in a particularly cost-effective manner on one and the same plant, the products being particularly stable and also storable over long periods. In view of the universal applicability of the plant, production may be at particularly low cost. In the case of PIT emulsions, particularly small droplet sizes can be achieved which can otherwise only be prepared in long-term storage-stable form in laboratory experiments.

This is of great advantage particularly when sunscreen formulations based on PIT emulsions are to be prepared: in this way, it is possible to incorporate a particularly large amount of photoprotective agent and thus achieve particularly high sun protection factors of up to 40 and above.

It is advantageous in the process according to the invention to use as loop mixer an apparatus which is characterized by a product feed arranged at a distance from the product discharge, a conveying device such as a multi-threaded conveying screw, which is located in an internal guide tube, the mixing of the product being effected as a result of the volume conveyed through the internal conveying device being a multiple of the volume introduced through the feed, giving rise to forced circulation outside the guide tube against the conveyance direction within the guide tube. It is particularly preferred to use a mixer of the Burdosa DMT 320 model. Such mixers have hitherto been used to prepare orange juice concentrate, yoghurt, salad sauces or other foods and allow the process parameters to be matched in a very variable manner to the requirements. For example, besides a pure mixer operation, emulsification or foaming are also possible.

It is advantageous in the process according to the invention to use as further mixer an apparatus which acts at the same time as a homogenizer. A homogenizer of the Becomix DH 500 model, Berents, Stuhr, Germany is preferably used. It is particularly advantageous to use a high-pressure homogenizer consisting of a high-pressure pump, a structured packing and a valve, as is described, for example, in European patent application 810025.

It is further advantageous, instead of the mixer (10), to use a combination of two mixing apparatuses, in particular a static mixer and a dynamic mixer. In this case, the temperature of the exiting mixture increases on passing through the combination of mixing apparatuses by 2 to 60.degree. C., based on the temperature of the entering mixture.

As a result of high-pressure homogenization, heating in a separate process step is particularly advantageously superfluous since, as a result of the input of energy for the homogenization, the homogenized material is very effectively heated simultaneously.

A further advantage of the process according to the invention is the property that it is very easy to clean the plant when changing the product. A cleaning solution is fed in and circulated in a suitable manner, thus dispensing with dismantling or laborious cleaning in some other way. Such apparatuses are also referred to as cip-capable (clean in process).
 

Claim 1 of 25 Claims

1. A process for preparing a cosmetic or dermatological preparation, wherein the process is continuous and comprises: (a) emulsifying at least two pre-products in at least one mixing device to form an emulsion, (b) adding to the emulsion of (a) water or an aqueous solution having a temperature which is lower than the temperature of the emulsion to form a cooled emulsion having a temperature of less than 40.degree. C., (c) adding to the cooled emulsion at least one substance selected from perfume oils and temperature-sensitive active ingredients, and (d) homogenizing the cooled emulsion and the at least one substance in at least one homogenizing device at a temperature of from 20.degree. C. to 50.degree. C. to form a homogenized emulsion.
 

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