EP0999890B1 - Method for preparing concentrated and emulsions calibrated in a highly viscous phase, in particular bitumen emulsions - Google Patents

Description

The subject of the present invention is a method of emulsification a hydrophobic or viscous hydrophilic phase, in particular useful for preparing concentrated and calibrated bitumen emulsions and also relates to emulsions thus obtained.

Emulsions, concentrated in very hydrophobic compound (s) viscous, are used in particular in the field of coatings like for example in the road industry. Indeed, emulsions represent an attractive alternative to the problem of spreading bitumen on pavements. In the traditional technique, pure bitumen is implemented hot which is expensive and can be dangerous for site personnel. When the bitumen is emulsified in water, the material obtained is perfectly fluid at ambient temperature which allows its implementation without difficulty. Under the influence of evaporation and drainage of the water, a film is obtained after a few hours homogeneous bitumen. Emulsions concentrated in very hydrophobic compounds viscous are also used in the adhesive industry via glues in emulsion based on rosin esters. Emulsions, concentrated in compound (s) viscous hydrophilic (s), for their part, are more particularly used in the food and pharmaceutical industries.

However, the techniques, which we have today, to prepare in most cases, this type of emulsion requires high temperatures, high pressures and / or high shear rates.

So, if we consider the particular case of bitumen, the emulsions are currently being prepared by hot injection. In general, the bitumen is heated to a temperature above 120 ° C and the phase continues, generally the water is heated to around 60 ° C. The mixture of bitumen and the aqueous phase is injected into a turbine at very high speed agitation, of the order of 5,000 revolutions per minute and at a pressure which can range up to 3 atmospheres. At the end of such a treatment, one generally obtains bitumen emulsions with a concentration not exceeding 70% by weight bitumen, an average size of small droplets (typically greater than 5 micrometers) and an equally high polydispersity.

This type of process therefore has several drawbacks.

In particular, conventional methods do not allow prepare emulsions concentrated above 70% in bitumen. However, some specific applications require in terms of handling emulsions more than 90% concentrated in bitumen. This is for example the case of sealants used for waterproofing works (protection of buildings, pipelines, undersides of cars).

Finally, the bitumen emulsions currently available do not give not satisfaction in terms of monodispersity. Bitumen droplet size present in these emulsions is generally greater than 5 microns and very heterogeneous. Storage stability and rupture of this type of emulsion are found difficult to control and the coatings which result therefrom, insufficiently homogeneous. It is clear that this is detrimental in terms of the implementation of the emulsions and the final mechanical quality of the corresponding coatings.

The object of the present invention is precisely to propose a process for preparing emulsions which are concentrated in one phase very viscous like bitumen and also calibrated

In particular, it is based on the demonstration that the mixture direct from a very viscous phase, i.e. having at the time of emulsification a viscosity between 1 and 5000 Pa.s, with a phase which is immiscible, in the presence of a surfactant, conducted under low shear and in a very short time to a viscoelastic paste (advantageously turns out to be with the specifics of an emulsion.

More specifically, the emulsification mode according to the invention is original in that it allows the production of "water in oil" type emulsions or "oil in water" very concentrated by directly mixing the two phases in laminar shear regime. It therefore clearly differs from the processes conventional emulsification, like the one mentioned above, which operate in turbulent regime. It is also distinguished from emulsification techniques by classical laminar regime which proceed by progressive incorporation of a first phase to be emulsified in a second phase or vice versa.

• le cas échéant, un traitement préalable de ladite première phase à émulsionner de manière à ajuster sa viscosité à une valeur inférieure à 5 000 Pa.s.,
• l'addition en une seule fois, de ladite phase à une seconde phase non miscible avec ladite première phase, en présence d'au moins un agent tensioactif et
• leur mélange sous cisaillement en régime laminaire jusqu'à obtention d'une émulsion stable et dans laquelle ladite première phase est présente à raison de 75 à 95% en poids. L'émulsion obtenue à l'issue du procédé revendiqué a en fait l'aspect d'une pâte viscoélastique Avantageusement, elle s'avère redispersable malgré une concentration élevée en l'une de ses phases. Elle peut donc être diluée de manière à adapter la concentration de l'émulsion finale aux exigences de l'application envisagée.Outre une concentration élevée en l'une de ses phases, l'émulsion obtenue selon l'invention possède une distribution granulométrique très resserrée et le diamètre moyen de ses gouttelettes peut être aisément contrôlé par l'intermédiaire de la vitesse de cisaillement ou par l'intermédiaire des paramètres de formulation et plus particulièrement la concentration en la seconde phase dite encore phase diluante.A cet égard, la présente invention a également pour objet un procédé utile pour préparer une émulsion concentrée et calibrée en une phase hydrophobe ou hydrophile et de viscosité comprise entre 1 et 5 000 Pa. s ou supérieure comprenant
• le cas échéant, un traitement préalable, de ladite phase à émulsionner de manière à ajuster sa viscosité à une valeur inférieure à 5 000 Pa.s,
• l'addition en une seule fois de ladite phase à une seconde phase, non miscible avec ladite première phase, en présence d'au moins un agent tensioactif et
• leur mélange sous cisaillement en régime laminaire jusqu'à obtention d'une émulsion stable et dans laquelle ladite première phase est présente à raison de 75 à 95% en poids, caractérisé en ce que la taille des gouttelettes de ladite première phase est contrôlée au sein de ladite émulsion par ajustement de la concentration en la seconde phase pour un taux de cisaillement et une concentration en agent tensioactif donnés.

The present invention therefore has for first object a process useful for emulsifying a first hydrophobic or hydrophilic phase and of viscosity between 1 and 5000 Pa.s or higher with a second phase immiscible with said first phase characterized in that it provides in action:

• where appropriate, a preliminary treatment of said first phase to be emulsified so as to adjust its viscosity to a value less than 5,000 Pa.s.,
• the addition at one time, of said phase to a second phase immiscible with said first phase, in the presence of at least one surfactant and
• mixing them under shear in a laminar regime until a stable emulsion is obtained and in which said first phase is present at a rate of 75 to 95% by weight. The emulsion obtained at the end of the claimed process in fact has the appearance of a viscoelastic paste. Advantageously, it turns out to be redispersible despite a high concentration in one of its phases. It can therefore be diluted so as to adapt the concentration of the final emulsion to the requirements of the intended application. In addition to a high concentration in one of its phases, the emulsion obtained according to the invention has a very tight particle size distribution. and the average diameter of its droplets can be easily controlled via the shear rate or via the formulation parameters and more particularly the concentration of the second phase, also known as diluent phase. In this regard, the present invention also relates to a process useful for preparing a concentrated and calibrated emulsion in a hydrophobic or hydrophilic phase and of viscosity between 1 and 5000 Pa. s or higher comprising
• where appropriate, a preliminary treatment of said phase to be emulsified so as to adjust its viscosity to a value less than 5,000 Pa.s,
• the addition at one time of said phase to a second phase, immiscible with said first phase, in the presence of at least one surfactant and
• mixing them under shear in a laminar regime until a stable emulsion is obtained and in which said first phase is present at a rate of 75 to 95% by weight, characterized in that the size of the droplets of said first phase is controlled within of said emulsion by adjusting the concentration in the second phase for a given shear rate and a concentration of surfactant.

As a rule, the size of the droplets of the first phase decreases when the shear rate and / or the surfactant concentration increase. Unexpectedly, the inventors have thus demonstrated that it was possible to adjust the droplet size of the first phase by controlling the amount of the second phase introduced to prepare the emulsion. The size of droplets do not evolve monotonically with the quantity of the second phase: the size first decreases then increases when the quantity of the second phase increases.

According to this particular mode of the invention, it thus turns out to be possible to obtain an emulsion having a minimum average droplet diameter, that is to say less than 2 microns, for an optimal amount of this second phase. The appreciation of this critical volume of the second phase in fact depends on the chemical nature of said first viscous phase at emulsify. For a determined quantity of the first phase to be emulsified, we establishes the evolution (at fixed stirring speed) of the average diameter of the droplets, obtained during its emulsification, for variable quantities in the second phase. The critical volume is the volume for which the diameter of the droplets is minimal. This appreciation of the critical volume is of course carried out for a shear rate and a concentration of surfactant given.

The emulsion has an average droplet diameter less than 2 microns or a relatively smaller size than that obtained according to conventional emulsification processes. Regarding polydispersity, it is less than 40% against for example more than 100% for emulsions bitumen classics. This polydispersity is expressed according to the Laser granulometer Coulter LS 230 and corresponds to the standard deviation of the distribution divided by the diameter means obtained (Coulter LS 230 Documentation page B-5).

The shear applied to the mixture is a laminar shear and is therefore adjusted so that the stirring mobile rotates at low speed. This scheme is characterized in that it has a low Reynolds number.

ρ est la masse volumique moyenne,

ν est la vitesse d'écoulement assimilable dans le cas de la présente invention à la vitesse du mobile d'agitation,

L est une longueur caractéristique assimilable dans le procédé revendiqué, à l'entrefer entre le mobile d'agitation et la paroi du réacteur, et

η est la viscosité moyenne de l'émulsion.

In fluid mechanics, the flow regimes are generally characterized with respect to an adimensional number called Reynolds number defined by Re = ρ ν L / η where

ρ is the average density,

ν is the flow speed which can be assimilated in the case of the present invention to the speed of the stirring mobile,

L is a characteristic length which can be assimilated in the claimed process, to the air gap between the agitation mobile and the wall of the reactor, and

η is the average viscosity of the emulsion.

Within the meaning of the invention, the laminar regime is characterized in that it has a low Reynolds number, less than about 1,000. Beyond this value, the regime becomes turbulent.

By way of illustration, if we consider in the claimed process values of ρ of 1000 kg / m ³ , ν of 0.3 ms ^-1 (circumferential speed of a mobile of radius 5 cm and rotating at a speed of 500 revolutions / minute), L of 0.002 m and η of 10 Pa.s (characteristic viscosity, at the applied shear speed, of an emulsion in which one of the phases is present at a rate of 90% by weight), there is a Reynolds number, Re of 0.06 which clearly shows that the shear regime applied to the emulsions is laminar.

In the case of a conventional process carried out in an industrial reactor, using values of ρ of 1000 kg / m ³ , ν of 30 ms ^-1 (circumferential speed of a cylinder of radius 0, 5 m and rotating at a speed of 5000 revolutions / minute), L of 0.001 m and η of 10 ^-2 Pa.s (characteristic viscosity, at the applied shear speed, of an emulsion in which one of the phases is present in the right proportion 60% by weight), on the other hand, there is a Reynolds number, Re, of 3000 corresponding to a turbulent regime.

Preferably, the stirring speed varies between 100 and 1000 revolutions per minute (corresponding to a shear rate of between approximately 250 and 2500 s ^-1 ) and more preferably is of the order of 400 to 500 revolutions per minute (correspond to a shear rate of approximately 1000 s ^-1 ). It is in fact adapted so as to transform very quickly, that is to say within a period of a few seconds to a few tens of seconds, the mixture, into the expected emulsion.

To this end, the stirring system is chosen so as to ensure that the both the homogenization and the shear of the mixture. So agitators such as flexible grids, propellers, paddles are particularly suitable in the part of the present invention.

Preferably, the emulsification takes place at temperature and ambient pressure. However, certain compounds whose viscosity is greater than 5 000 Pa.s must be treated and preferably by heating in order to reduce their viscosity. To avoid the boiling of the second phase, under the effect of heat brought by the first viscous phase previously heated, it can be necessary to work at a pressure higher than atmospheric pressure. The optimal temperature and pressure conditions will be determined by humans of art through simple routine operations.

Within the meaning of the invention, said first hydrophobic phase or hydrophilic is or comprises at least one hydrophobic or hydrophilic compound. Through example, it may include a mixture of several compounds having either hydrophilic is hydrophobic and in a diluted form or not.

This hydrophobic or hydrophilic phase is in all cases characterized by a very high viscosity, of the order of 1 to 5,000 Pa.s or higher. It has the appearance of a very viscous liquid, therefore particularly difficult to emulsify.

By way of illustration of the compounds capable of being dispersed according to the invention, mention may very particularly be made of hydrophobic materials such as in particular rosin esters (adhesive industry), lanolin (cosmetics), bitumens, waxes (cosmetics, cleaning products ...), low molecular weight polybutadienes or hydrophilic compounds like in particular polyethylene glycol, sugars, gelatins (agar-agar, carrageenans, ...) (food industry, pharmacy) and their mixtures.

Some of the corresponding hydrophobic or hydrophilic phases having at room temperature a high viscosity, in particular a higher viscosity at 5000 Pa.s, it becomes necessary to lower their viscosity to a value below 5,000 Pa.s to give them beforehand a fluidity conducive to their mixing subsequent with said second phase. As explained above, we apply then in said first phase a pretreatment preferably consisting of a heating operation combined, if necessary, with mechanical agitation (faster homogenization of the temperature within the viscous phase). In done, this heating is more particularly necessary when said first phase has a viscosity at room temperature such that it opposes its flow and / or pumping. In this regard, any destabilization of the emulsion obtained, which may be caused by evaporation of the second phase. In this particular case, the viscoelastic paste obtained may be diluted within hours of preparation and preferably immediately after its preparation in order to limit instabilities (coalescence) which may result from evaporation.

As regards the second phase, it can be either aqueous or oily. In the case of an oil, this oil can be either mineral, vegetable or animal. As mineral oil, it is possible in particular offer parrafinic, naphthenic oils or their mixtures.

The surfactants used according to the invention can be chosen among all categories of surfactants (anionic, cationic, nonionic, amphoteric ...). They can be chosen from surfactants conventionally implemented in the emulsification processes, of said first phase considered. They are of course selected taking into account the type of emulsion, viscous hydrophobic phase in aqueous phase or viscous hydrophilic phase in the oily phase, which it is envisaged to prepare according to the invention. Therefore to obtain water-in-oil type emulsions, surfactants are chosen with a hydrophilic / lipophilic balance (HLB) of less than 7 and for oil-in-water type emulsions, HLB surfactants greater than 14.

The term "HLB" (Hydrophilic Lipophilic Balance) refers to the ratio hydrophilicity of polar groups of surfactant molecules to the hydrophobicity of the lipophilic part of these same molecules; it is a term commonly used in the field of surfactants (see Treaty "Engineering techniques", chapter A7610 "Surfactants".

Advantageously, care will be taken to dissolve the surfactants in the second phase in order to avoid possible problems of kinetics of solubilization. Surfactants are used in the process according to the invention in a reduced amount and preferably varying between 0.5% and 5% by weight expressed relative to the weight of said first hydrophobic phase or hydrophilic to be emulsified so as to make the most of the amount of surfactant. The surfactant yield is defined as the ratio of the amount of surfactant necessary to cover the droplets dispersed on the total amount of surfactant used.

The method according to the invention is very particularly useful for prepare aqueous bitumen emulsions.

We can thus prepare from 100 grams of bitumen and for a water concentration of 5 grams per 100 grams of bitumen, highly concentrated emulsions, namely containing 95% by weight of bitumen, which can be diluted and stable in storage.

As mentioned previously, the viscoelastic paste obtained can be diluted with hot water (60 ° C) in the hours following its preparation and preferably immediately after its preparation. Emulsions with after dilution a bitumen concentration between 75% and 85% is found particularly stable for at least several months.

The introduction of a surfactant such as in particular bromide tetradecyltrimethylammonium at a rate of 1.5 grams per 100 grams of bitumen also makes it possible to reduce the size of the droplets of the emulsion to a value close to one micron.

A particular embodiment of the invention therefore aims application of the claimed process to the preparation of a bitumen emulsion concentrated and calibrated. This process includes the steps of heating bitumen, up to a temperature of 95 ° C, is mixed in a reactor and at atmospheric pressure, with 5% by weight of water and 0.5% to 1.5% in weight of a surfactant relative to the weight of the bitumen and to be applied to said mixture thus obtained, a shear rate so as to form said emulsion which is recovers.

As regards the stirring speed, it can vary between 0 and 1000 revolutions per minute and is preferably of the order of 400 to 500 revolutions per minute, which corresponds to a shear rate of approximately 1000 s ^-1 . An emulsion concentrated in bitumen is obtained very quickly, that is to say in a few seconds, under the effect of this shearing. It actually has the appearance of a viscoelastic paste of non-emulsified appearance. An examination of this emulsion shows that it has a concentration of up to 90 or even 95% by weight of bitumen. Advantageously, this paste proves to be perfectly redispersible in water despite its high concentration of bitumen.

The present invention also relates to emulsions of bitumens characterized in that they have a bitumen concentration greater than 75% and preferably at least equal to 85% by weight of bitumen.

Bitumen emulsions claimed and obtained according to the process of the invention have a polydispersity of less than 40%. They consist of droplets having an average diameter less than 2 microns, and preferably less than 1 micron.

It is clear that the method according to the invention as well as the emulsions thus obtained are particularly advantageous in the field of the road industry. The claimed process makes it possible to prepare fine emulsions highly concentrated bitumens with very good control over the final size of their droplets, according to a quick and simple protocol and with few surfactants.

The present invention also extends to phase emulsions hydrophobic or hydrophilic, obtained according to the claimed process. It turns out particularly useful for preparing concentrated and calibrated emulsions for therapeutic, cosmetic or food interest.

The examples and figures presented below, without limitation of the present invention, highlight other advantages thereof.

FIGURE

figure 1 :

Graph representing the evolution of the mean diameter of the droplets obtained for a stirring speed of the order of 400 revolutions / minute (shear rate of approximately 1000 s ^-1 ) as a function of the quantities of water and of surfactant ( TTAB) present at the start.

figure 2:

Graph representing the evolution of the average droplet diameter prepared according to Example 3 as a function of the shearing speed applied during emulsification.

figure 3:

Graph representing the evolution of the mean diameter of the droplets obtained for a stirring speed of the order of 400 revolutions / minute (shear rate of approximately 1000 s ⁻¹ ) as a function of the quantity of TTAB.

figure 4:

Emulsification efficiency graph obtained for a stirring speed of the order of 400 revolutions / minute (shear rate of approximately 1000 s ^-1 ), mass TTAB used / mass introduced.

figure 5:

Graph representing the evolution of the average diameter of the droplets in depending on the quantities of oil, for an emulsification carried out according to Example 5.

figure 6:

Microscopic photograph of a PEG emulsion obtained according to Example 5.

figure 7:

Graph representing the evolution of the average diameter of the droplets in depending on the amount of Span 80® or an emulsion prepared according to Example 5.

figure 8:

Comparison in terms of polydispersity of an emulsion according to the invention and a control emulsion (example 7).

EXAMPLE 1 Protocol for the preparation of an aqueous bitumen emulsion according to the invention.

100 grams of bitumen with a penetration index of 90/100 * are heated to a temperature of the order of 100 ° C. An aqueous solution of tetradecyltrimethyl ammonium bromide (TTAB) of variable concentration is prepared. The heated bitumen is poured onto the aqueous solution and the whole is kneaded for a few seconds using a flexible grid, at 400 revolutions per minute (1000 s ^-1 ), in a 10 cm reactor. of diameter. The emulsion obtained almost instantaneously, is characterized in terms of droplet diameter.

To measure the diameter of the droplets, a granulometer Commercial Laser Coulter LS 230 (COULTRONICS company) is used.

EXAMPLE 2 Effect of the quantity of water and surfactant (TTAB) on the mean diameter of droplets of a constant shear bitumen emulsion

The protocol, described in example 1, is reproduced for two TTAB concentrations, 0.75 grams and 1.5 grams and present for each of these concentrations, with a quantity of water varying between 4 and 14 grams. The emulsions, obtained at the end of each of the tests, are characterized by the average diameter of their droplets. The results are represented on the graph of figure 1.

The finest emulsion is obtained for a constant amount of water around 5 grams per 100 grams of bitumen The minimum size of droplet thus obtained can also be reduced by increasing the amount of surfactant. Thus for 1.5 grams of TTAB in 5.5 grams of water, the minimum diameter is increased to 0.8 microns against 2 microns with 0.75 grams of TTAB.

EXAMPLE 3 Effect of the shear rate on the average diameter of the droplets of the emulsified viscous phase .

The protocol described in Example 1 is reproduced with 100 g of bitumen, 1.5 g of TTAB and 5.5 g of water for variable agitation rates. The emulsions obtained at the end of each of the tests are characterized by the average diameter of their droplets. The results are shown in the graph in FIG. 2. It is thus observed that a high shear speed promotes the formation of droplets with significantly smaller average diameter. However, the stirring speed must not exceed a threshold value of 1,000 revolutions / minute (approximately 2,500 s ^-1 ) beyond which the excessively violent shear destroys the concentrated emulsion.

EXAMPLE 4 Effect of the amount of cationic surfactant on the average diameter of the droplets of a bitumen emulsion at constant volume of water and shear .

The protocol described in example 1 is reproduced for different TTAB concentrations in the presence of 5.5 grams of water The results obtained are shown in the graph in Figure 3.

Note that 1 gram of TTAB per 100 grams of bitumen is sufficient to reach sizes on the order of a micron.

A characterization of the process yield according to the mass of TTAB introduced, in fact shows that the maximum efficiency is almost reached for this maximum amount of TTAB. More specifically, this result is obtained by posing the yield as the ratio of the mass of surfactants, present at the interfaces, on the total mass of surfactants introduced. The mass of surfactants, present at the interfaces, is simply deduced by a measurement of the residual amount of surfactants, present in the second phase after dilution controlled. The graph in Figure 4 shows this relationship as a function of the total mass introduced into the 5.5 grams of water necessary to emulsify 100 grams of bitumen.

EXAMPLE 5 Assessment of the optimal quantity in the second phase relative to the average diameter of the droplets of an emulsion .

In this example, the viscous hydrophilic phase to be dispersed is a aqueous mixture containing 44% polyethylene glycol PEG 35000, the surfactant is Span 80® (sorbitan monooleate, marketed by Sigma), present at a rate of 1.5 g per 100 g of the phase to be dispersed and the continuous phase is dodecane.

Several mixtures of these compounds are carried out for different amounts of dodecane under a shear of 400 revolutions / minute (1000 s ^-1 ) (the apparatus is the same as that used for the manufacture of bitumen emulsions) within a reactor. Emulsions, obtained almost instantaneously, are characterized by the average diameter of their droplets. The results are represented on the graph in FIG. 5. The photo presented in FIG. 6 is a microscopic photograph of one of these emulsions.

We note on the graph of Figure 5 that the minimum diameter, namely about 2 microns, is obtained for 3 g of dodecane.

EXAMPLE 6 Effect of the amount of surfactant on the average diameter of the droplets of a constant shear emulsion .

The protocol described in example 5 is reproduced for several concentrations of Span 80® surfactant and 3 g of dodecane. The emulsions obtained at the end of each of the tests are characterized by the mean diameter of their droplets. The results are shown in the graph in Figure 7.

The finest emulsion is obtained for 4 g of Span 80®.

EXAMPLE 7 Comparison of a bitumen emulsion according to the invention and a conventional emulsion in terms of polydispersity and average diameter of the droplets .

The industrial implementation technique consists of injecting under pressure (about 1.5 atmospheres) and at 130 ° C the bitumen, on the one hand, and the phase aqueous soap, on the other hand, between two coaxial cylinders (a rotor and a stator) spaced about 1 mm apart. The rotor rotates at a speed of about 5,000 revolutions per minute. Emulsification takes place directly in the 1 mm air gap, it takes place in turbulent conditions. The volume fraction of the phase to be dispersed cannot exceed 70% on pain of blocking the system.

This assessment is carried out from an emulsion obtained in accordance with the present invention and incorporating 0.75 grams of TTAB for 5.5 grams of water and 100 grams of bitumen and an industrial emulsion classic bitumen. This industrial emulsion contains 60 grams of bitumen, 0.5 gram of cationic surfactant and 39.5 g of water.

The particle size distributions obtained by the two techniques are shown in Figure 8.

For the emulsion according to the invention, a centered average size is noted around 2 microns with a polydispersity close to 30%. The control emulsion has a significantly larger mean droplet diameter at namely 5 microns and a polydispersity not in accordance with the invention, that is to say significantly higher than 40%.

Claims (12)

1. A process for the preparation of a concentrated calibrated emulsion in a hydrophobic or hydrophilic phase having a Viscosity between 7 and 5000 Pa.s or more, referred to as the first phase, comprising:

   preparing the said first stage for emulsification, if necessary in a preliminary stage of prior treatment, so as to adjust its viscosity to a value below 5000 Pa.s

   adding the said first phase at a viscosity of less than 5000 Pa.s, in a single, operation, to a controlled quantity of a second phase which is not miscible with the said first phase, in the presence of at least one surfactant and

   mixing these under laminar shear conditions

   characterized in that the quantity in the second phase is adjusted to obtain a stable emulsion having a polydispersity of less than 40% on termination of the shear mixing, for a given shear rate and surfactant concentration, and in which the said first phase is present in a concentration of 75 to 95% by weight, and of which the mean diameter of the droplets is controlled within the said emulsion to a size of less than 2 microns.
2. A process according to claim 1, characterized in that the prior treatment of the said first phase is effected by heating.
3. A process according to claim 1 or 2, characterized in that the second phase is present in a quantity such that the mean diameter of the droplets of the said emulsion is less than or equal to 1 micron.
4. A process according to one of claims 1 to 3, characterized in that the surfactant is present in a quantity between 0.5% and 5% by weight expressed in relation to the weight of the first phase.
5. A process according to any one of the preceding claims, characterized in that the first phase is or comprises at least one compound selected from bitumens, colophane esters, low molecular weight polybutadienes, waxes, lanolin, sugars, polyethylene glycols, gelatines and their mixtures.
6. A process according to any one of the preceding claims, characterized in that the laminar conditions applied have a Reynolds number of less than approximately 1000.
7. A process according to any one of the preceding claims, characterized in that the shear rate varies between 250 and 2500 s^-1 and is preferably of the order of 1000 s^-1.
8. A process according to any one of the preceding claims, characterized in that the first phase is a bitumen and the second phase is water.
9. Application of a process according to one of claims 1 to 8 to the preparation of concentrated gauged bitumen emulsions.
10. A process for the preparation of a gauged bitumen emulsion having a bitumen concentration of the order of 95% by weight of bitumen and a viscosity of between 1 and 5000 Pa.s or more, characterized in that the bitumen is heated to a temperature of 95°C, this is then mixed within a reactor at atmospheric pressure with 5% by weight of water and 0.5 to 1.5% by weight of a surfactant with respect to the weight of bitumen, a shear rate is applied to the mixture so obtained so as to form an emulsion having a polydispersity of less than 40% in which the mean diameter of the droplets is adjusted to a size of less than 2 microns.
11. An emulsion comprising 95 to 90% by weight of a hydrophobic or hydrophilic phase, of a viscosity between 1 and 5000 Pa.s or more, in which the mean diameter of the droplets is of a size less than 2 microns and of which the polydispersity is less than 40%, characterized in that it is obtained in accordance with the process defined in one of claims 1 to 8 and 10.
12. A concentrated aqueous emulsion of bitumen, characterized in that it comprises at least 75% and preferably more than 85% by weight of bitumen, has a polydispersity of less than 40%, and in which the mean diameter of its droplets is less than microns.

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