The present invention relates to specific diamines useful as surfactants, especially as emulsifier, especially for bitumen emulsions.

Bitumen emulsions are well known compositions including droplets of bitumen dispersed in an aqueous medium.

Generally, they contain emulsifiers that allow the emulsification and avoid the collapse of the emulsion for a more or less long period.

Among possible emulsifiers, amines are commonly used, especially for stabilizing the so-called "cationic emulsions".

An object of the present invention is to provide a new familiy of amine suitable as surfactant and that are suitable, inter alia, as emulsifier for bitumen emulsion.

To this end, the instant invention proposes to make use of specific diamines molecules, which are obtained via a new process route and that were not known in the prior art to the best knowledge of the inventors.

More precisely, according to a first aspect, one subject-matter of the instant invention is a surfactant of the formula (I):

NH - (E ¹ )- N ^{c d}

I I

H

(I)

wherein :

^■ each of R ^a and R ^b , which are identical or different, is a linear or branched, saturated or unsaturated, hydrocarbon chain, that may be interrupted and/or substituted by at least a monocyclic or polycyclic group, that may be, but not neceassarily, an aryl group,

each of R ^a and R ^b being typically :

a linear or branched alkyl chain having 1 to 24 carbon atoms, preferably at least 4 carbon atoms (each of R ^a and R ^b typically carrying from 7 to 17 carbon atoms ; it being independently preferred that the sum of the number of carbon in Ra and Rb is of at least 7, preferably of at least 10 and typically of at least 14);

or

a linear or branched alkenyl chain having 1 to 20 carbon atoms and having one or more unsaturation (typically 1 to 3) ;

^■ (E ¹ ) is a divalent hydrocarbon radical, linear or branched, and preferably linear, not substituted or substituted, e.g. carrying a -OH group and/or optionally carrying a another heteroatom containing group such as an amine , typically an alkanediyl radical of formula -(CH ₂ ) _n - wherein n = 1 , 2, 3 or 4, (and wherein at least one of the hydrogen may be substituted by a -OH group or by an amine)

^■ each of Rc and Rd, which are identical or different, is a a linear or branched alkyl chain having 1 to 10 carbon atoms, typically 1 to 4 carbon atoms.

Especially for cost reasons, R ^a and R ^b are preferably linear groups, typically linear hydrocarbon groups. The surfactants of formula (I) possess, as such, a branched structure of their hydrophobic part : R ^a and R ^b constitute a kind of "twin tail" of the diamine. The compositions of the invention do not need to make use of branched R ^a and R ^b groups which are more costly than linear R ^a and R ^b groups.

Typically, (E ¹ ) is a divalent alkanediyl radical of formula -(CH) _n - wherein n = 1 , 2, 3 or 4, preferably 2 or 3 (most typically 3)

According to another aspect, the invention relates to a method for preparing the surfactant having the formula (I) as defined herein-above.

This method includes the following steps : step 1 : reacting two acids Ra-COOH and Rb-COOH (the reaction being obtained by reacting a population of acids including these two acids), wherein Ra and Rb are identical or different, via a Piria decarboxylating ketonization, whereby a internal ketone is obtained having the formula (II) :

O

(II)

wherein R ^a and R ^b have the meaning given herein-above for formula (I)

In this step 1 , in practice, the reaction may be conducted on a single fatty acid (in that case Ra=Rb) or on a mixture of distinct fatty acids (whereby a mixture of internal ketone (II) is obtained with a mixture of groups Ra and Rb in the obtained internal ketones).

step 2 : reacting the internal ketone (II) obtained in step 1 with a diamine of formula H ₂ N-(E1 )-NR ^c R ^d in a reductive amination reaction

whereby the compound of formula (I) is obtained :

NH - (E ¹ )- NR ^c R ^d

I

R*- C - R

I

H

(I)

wherein R ^a , R ^b , R ^c , R ^d and (E ¹ ) have the meaning given hereinabove for formula (I)

The surfactants of the invention may be easily prepared from cheap and available (typically naturally occuring) raw materials of relatively low cost, which is a first avantage.

Their two-step preparation process further more allows a good control of their functionalization, which give an access to well defined tailor made molecular structures. By carefully choosing the chain length of the starting fatty acids, it is possible to control the chain length of the fatty ketone and therefore the structure of the final surfactant which allows fine tuning of the properties of the final product.

In addition, according to a specific embodiment, the hydrophobic part of the surfactants of the invention can be entirely saturated, which provides stability against oxidation when compared to unsaturated products.

The diamines and mixtures of diamines used in the scope of the invention are preferably liquids at a temperature of 10 to 30°C. Accordingly, the invention may make use of at least one diamine liquid between 10 and 30°C (to this end, it is advantageous to make use of amines having a number of carbon as low as possible in the groups R ^a and R ^b ), or of mixtures that are mixtures liquid between 10 and 30°C even if they contain amines that are, individually, not liquid in this range of temperature (these mixtures preferably contain a liquid diamine in addition to the non liquid diamine, the liquid diamine having preferably a number of carbon as low as possible in the groups R ^a and R ^b ).

According to yet another aspect, a subject-matter of the invention is the use of a diamine of formula (I) (or of a mixture of amines comprising at least two diamines of formula (I) or of a formulation comprising at least a diamine of formula (I) or a mixture of such diamines) as an emulsifier in a bitumen emulsion.

The invention also relates to a method for preparing a bitumen emulsion comprising a step wherein a bitumen is mixed together with an aqueous medium (typically water) under shear rate and in the presence of at least a diamine of formula (I), said at least one diamine of formula (I) being preferably premixed with the aqueous phase.

The bitumen emulsions obtained in the scope of the invention, that comprise a continuous aqueous phase, droplets of bitumen dispersed therein and at least a diamine (more preferably a mixture of at least two distinct amines of formula I) constitute an other subject-matter of the instant invention.

More details and preferred embodiments are set forth in the detailed specification hereinafter. The diamines and their preparation

The R ^a and R ^b groups present in the surfactants of formula (I) may be defined by the acids R ^a COOH and R ^b COOH from which they are prepared in step 1 as defined herein-above (and also referred herewith as " fatty acids"), or from which they could have been prepared in the case they are not prepared by making use of this step.

Preferred fatty acids from which the surfactants of formula (I) are actually derived (or theorically derivable) are caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid , naphthenic acids, isostearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid or mixtures thereof and preferred acid derivatives are the esters and anhydrides of these acids. Preferred are caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, naphthenic acids, isostearic acids or mixture thereof.

Other fatty acids from which the surfactants of formula (I) are actually derived (or theorically derivable) comprise one or more double bonds in the chain and include for example oleic acid, linoleic acid, linolenic acid and erucic acid to name only a few examples.

Yet other fatty acids from which the surfactants of formula (I) are actually derived (or theorically derivable) comprise the so called naphthenic acids. The term "naphthenic acid" herein generally denotes a complex mixture of saturated monocarboxylic acids containing cyclopentyl and/ot cyclohexyl fragments containing usually 9 to 20 carbon atoms. Naphthenic acids are obtained by oxidation of the naphtha fraction of crude oil and their composition varies with the crude oil composition and the conditions during refining and oxidation.

Preferably, the diamines of formula (I) are actually prepared from an internal ketone obtained from fatty acids according to step 1 of the process as defined herein-above. In that case, the surfactants of formula (I) may either be obtained from a single fatty acid RaCOOH or from a starting fatty acids mixture. In the case of a mixture of fatty acids, said mixture may be for example a so-called "cut" as typically obtained from vegetable or animal oils through saponification or alcoholysis. More preferably, it may be a fatty acid cut derived from coconut oil or palm kernel oil, that preferably contains a mixture of fatty acids which can comprise fatty acids having 8 carbon atoms up to 18 carbon atoms.

Internal ketones used in step 2 of the process described herein above can alternatively be obtained through cross-ketonization reactions starting from a mixture of linear fatty acids and naphthenic acids, or through cross-ketonization starting from a mixture of aliphatic fatty acids and benzoic acid.

The surfactants of the invention may advantageously been prepared in the following conditions :

Step 1 : decarboxylative ketonization of fatty acids

In this reaction step, fatty acids, preferably saturated straight chain fatty acids, are transformed into the internal ketone (II) through a decarboxylating ketonization reaction. This reaction is typically conducted with the fatty acids in a liquid phase and preferably by continuously removing water formed during the reaction from the reaction mixture.

Step 1 can be applied to a single fatty acid or to a cut of fatty acids generating therefore a cut of fatty ketones of formual (II). Typically the prepared fatty ketones of formula (II) contain the carbonyl group sensibly in the middle of the chain (exactly in the middle when a single fatty acid is used : Ra = Rb, the ketone is symetrical - when starting from a cut of fatty acids, all the possible ketones (II) are formed by combination of the different chains of the starting fatty acids, with a distribution of ketones obtained after the reaction following sensibly a statistical binomial law).

Typically, step 1 may be catalyzed by at least one metal compound, advantageously selected from the group consisting of Mg, Ca, Al, Ga, In, Ge, Sn, Pb, As, Sb, Bi, Cd and transition metals having an atomic number of from 21 to 30 or a mixture thereof or an oxide of these metals or a mixture thereof, preferably in an oxydized state (the metal in its oxidized state may be generated in situ by introducing the corresponding metal at a non oxidized state).

The reaction of step 1 is adavantageously catalyzed by compounds of oxydized iron, typically at least one iron oxide, such as magnetite Fe ₃ 0 ₄ , and/or Fe ₂ 0 ₃ , or FeO, the at least one iron oxide being preferably generated in situ in step 1 by introducing metallic iron, typically iron powder (namely : Fe ⁽⁰⁾ ) which has the advantage to be a very cheap and abundant material. When step 1 is carried out in the presence of a metal compound of the type recited above, especially metallic iron, it is advantageous that step 1 comprises two successive stages, namely :

1.1) in a first stage (wherein especially active catalyst species are formed), the metal compound and a first part of the fatty acids (the whole fatty acids being those referred as R ^a COOH and R ^b COOH in step 1 of the process) are mixed in a molar ratio of from 1 :0.8 to 1 :3.5 (molar ratio metal: carboxyl group equivalent) and reacted for a period of from 5 to 300 min at a temperature of from 180 to 270 °C, preferably from 190 to 260°C for a duration of from 5 to 240 min, fo example o from 15 to 120 min, and preferably in the substantial absence of added solvents, and

1.2) in a second stage, subsequent to stage (1 .1 ), the temperature is raised to 290 to 400°C and the rest of the fatty acids is added over a period of time of from 1 h to 24 h (typically until the molar ratio of fatty acid to metal is in the range of from 6:1 to 99:1 ), preferably part by part or continuously. Besides, step 1 .2 is preferably conducted in the substantial absence of added solvents

After stage (1 .2), it can be interesting to separate the metallic compounds from the products (that may be done using conventional techniques) and then to recycle the metallic compounds, e.g. for the conversion of another batch of fatty acids

The fatty acids used in the two stages (1 .1 ) and (1 .2) preferably comprise at least 10 mol%, based on the entire amount of fatty acids, of fatty acids having 12 carbon atoms or less. Typically, the fatty acids are selected from butanoic acid, hexanoic acid, isostearic acids, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid or mixtures thereof, and more preferably the fatty acids comprises 8 to 18 carbon atoms.

Stages 1 .1 and 1 .2 can also be operated on fatty acid derivatives preferably selected from esters and anhydrides, such as esters or anhydrides of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid or mixtures thereof (these derivatives preferably contain with 8 to 18 carbon atoms). Step 1 of the process may for example be conducted by :

(a) first reacting, at 220-270°C, typically at about 250°C, metallic iron (e.g. iron powder) with 1 .5 to 2.5 equivalents, advantageously 2 equivalents of fatty acids ("first portion" that leads to the formation of iron(ll) carboxylate species (with formation of H ₂ ), The reaction progress can advantageously be followed by in-situ IR analysis (with lauric acid, for example, which has a large and intense absorption band between 2500 cm ^"1 and 3500 cm ^"1 which is absent in the spectrum of the iron salt) ;

and then, after a sensibly complete conversion of fatty acids in step a),

(b) the temperature of the reaction mixture obtained by step (a) is risen above 290°C, preferably to about 300°C (whereby carboxylate salts of iron decompose to iron oxide, fatty ketone and C0 ₂ ) and maintained at this temprature and the remaining fatty acids are added to the liquid mixture.

In step (b), the addition of the fatty acids is advantageously made at a flow, in order to prevent accumulation of fatty acids, which can be checked easily using in-situ IR analysis: the fatty ketone (II) displays a v _(C =o ₎ absorption which is distinct from the absorption bands of the starting acid and the ferrous complex). Typically, the rest oft he fatty acids introduced in step (b) is added over a period of from 2 to 12 hours.

The ketone (II) acts also as a high boiling point solvent and the water generated during the reaction can therefore be trapped e.g. thanks to a dean- stark apparatus.

At the end of stage (b), the products fatty ketone can be separated from iron compounds, for example as follows:

- distillation under reduce pressure (50 mbar, 280-315°C)

- the final mixture can be diluted in CHCI3 and the suspension filtered (typically on a silica plug) and then eluted with CHCI3. Evaporation of the solvent affords fatty ketone free of iron. Step 2 : preparation of the sought diamine (I)

by reaction of the ketone (II) with the diamine

This step allows a reductive amination of the ketone (II) obtained in step 1 .

This amination is preferably performed by reacting the ketone (II) and the diamine of formula H ₂ N-(E1 )-NR ^c R ^d as defined herein-above in the presence of a transition metal (e.g. Ni, Co, Cu, Fe, Pd, Pt) based catalyst (typically Pd/C), under hydrogen pressure (typically between 1 atm. and 200 bar).

According to a possible embodiment, the reaction is carried out in a solvent. However, the presence of such a solvent is not compulsory and according to a specific embodiment, no solvent in used in step 2. The exact nature of the solvent, if any, may be determined by the skilled person. Typical suitable solvents include, without limitation, methanol, ethanol, isopropanol and mixtures thereof.

Besides, Step 2 is usually carried out at a temperature ranging from 15°C to 300°C.

Step 2 may be conducted batchwise, semi-continuously or continuously and generally performed either in a batch mode or in a continuous mode using a fixed-bed catalyst (gas-solid or gas-liquid-solid process).

A diamine of formula H ₂ N-(E ¹ )-NR ^c R ^d suitable for step 2 is dimethylaminopropylamine (DMAPA). This amine can be employed in stoichiometric amounts or in excess.

Other example of diamines suitable in step 2 include Aminoethylethanolamine (AEEA) and Ethylendiamine (EDA).

According to a specific embodiment, the group -(E ¹ )- of the diamine of formula H ₂ N- (E1 )-NR ^c R ^d may comprise an amine groupe (in that case, the amine may be a triamine or a polyamine : the term "diamine" as used in step 2 intend to encompass compounds including at least two amine group, and optionally more). Examples of amines with more that two amine groups include for example diethylene triamine (DETA), triethylenetetramine (TETA), tetraethylene pentamine (TEPA)

Mixtures of diamines may also be used, including for example mixture of D ETA/E D A/AE E A The diamine (I) produced in step 2 can be recovered after catalyst separation and removal of solvent and DMAPA excess. Finally the product can be purified, e.g. using standard technics such as distillation.

Use of the diamines (I) in bitumen

The diamines according to the invention are surfactants that are suitable as emulsifiers of hydrophobic droplets in an aqueous phase. They are especially of interest for bitumen emulsions.

The diamines as used individually according to the invention, or the mixture of diamines when they are use as such, are preferably liquids at a temperature of 10°C to 30°C, and preferably in a wider range of temperature, advantageously at least between 0°C to 40°C . To this end, it is advantageous to make use of

- individual amines having a number of carbon as low as possible in the groups R ^a and R ^b , for example less than 18 carbon atoms, more preferably less than 16, more preferably less than 14, for example less than 12 ;

mixtures of amines containing distinct groups R ^a and R ^b . Such mixtures may be e.g. obtained from mixtures of ketones (II) obtained from mixtures of fatty acids in step 1 as defiend above, for example from cuts of C ₈ -Ci ₈ fatty acids.

Non restrictive examples of diamine of specific interest include the compounds of formula (I) wherein :

Ra and Rb are a mixture of fatty chain (alyl chains typically) of between C ₈ and C18 (having between 8 and 18 carbon atoms)

When a diamine of formula (I) (or of a mixture of amines comprising at least two diamines of formula (I) or of a formulation comprising at least a diamines of formula (I) or a mixture of such diamines) is used as an emulsifier in an emulsion, especially in a bitumen emulsion, it is typically used at a content of 0.05% to 5%, for example from 0.1 to 2 % by weight, on the basis of the total weight of the emulsion.

The emulsions as obtained in the scope of the invention, comprising an emulsion of a bitumen (modified or not) in an aqueous medium and including the diamines (I) are typically cationic emulsions that may especially be selected from :

tack coat emulsions;

primary coating emulsions;

petration coat emulsion;

seal coat emulsions;

spraying emulsions;

surface treatment emulsions;

surface treatment or surface dressing emulsions;

coating emulsion or mixing emulsions;

microsurfacing emulsions;

cold mix or cold asphalt concrete for wearing course emulsions;

grave emulsion ; and

emulsion for storable cold mixes.

The appended examples illustrate in details preparation of diamines of the invention, which are useful in bitumen applications

Example 1 :

synthesis of surfactants of formula (I)

1.1. Step 1 : synthesis of an internal ketone

1.1.1. synthesis of Cga-tricosanone (internal ketone from a C12 acid)

The reaction was carried out under argon in a round bottom flask equipped with mechanical stirring, dean stark apparatus and an addition funnel.

In the reactor, 700 mg of iron powder were dispensed and 20 g of lauric acid was then introduced in the addition funnel as follows :

- a first portion of 5g of lauric acid was added into the reactor and the temperature is brought to 250°C. The mixture is stirred at this temperature for 2 hours during which the color of the media changed to black and H ₂ gas was released

- after the stirring of 2 hours, the temperature was risen to 300°C, and the mixture stirred during 1 h30 and then 15 grams of lauric acid were slowly added into the reactor during 4h30 at a flow which allows keeping concentration of lauric acid in the reaction media very low (no accumulation of free acids in solution).

At the end of the reaction, the addition funnel was replaced by a distillation apparatus and the products were distilled off at 290°C-340°C under 50 mbars pressure.

Then the distillation apparatus was again replaced by the addition funnel containing a new amount of 5g + 15g of fatty acids and the operations described above were repeated for another cycle.

Importantly, no additional amount of iron was introduced. This possible recycling of iron is a generic advantage of step 1 : the residue in the flask remaining after distillation is efficient to convert the next batch of acids.

Overall 4 cycles have been carried out without any loss of performances reducing therefore the concentration of iron to less than 1 wt% relative to total fatty acids amount converted. 1.1.2. synthesis of C15-C35 ketones mixture

from a cut of fatty acids (C8-C18)

A cut of saturated straight chain fatty acids with a distribution representative of natural coconut oil (C8: 7 wt%, C10: 8 wt%, C12: 48 wt%, C14: 17 wt%, C16: 10 wt% and C18: 10 wt%) was used in this case.

The reaction was carried out under argon in a round bottom flask equipped with mechanical stirring, dean stark apparatus and an addition funnel.

In the reactor, 3.3 g of iron powder were dispensed and a total 100 g of melted fatty acids were introduced in the addition funnel. The reaction was conducted as follows :

- A first portion of 25 g of acid was added into the reactor and the temperature was brought to 250°C. The mixture was stirred at this temperature for 2 hours during which the color of the media changes to black and H ₂ gas is released.

- after the stirring of 2 hours, the temperature was risen to 320°C and the mixture was stirred during additional 2h00. The remaining amount of fatty acids (75 grams) is then slowly added into the reactor during 6h00 at a flow (3 portions of 25 g are added every 2 hours in this case) which allows keeping concentration of free fatty acids in the reaction media very low (no accumulation of free acids in solution).

The mixture was then allowed to cool down at room temperature and 200 mL of CHCI ₃ was added into the reaction vessel.

The suspension was filtered on a silica plug (600g) and the remaining product was eluted with additional volume of CHCI ₃ . After evaporation of the solvent, 140g of the sought product (82% isolated yield) was recovered as a white wax.

1.2. step 2 : synthesis of the diamine

1.2.1. synthesis from Cg¾-tricosanone (internal ketone from a C12 acid)

In a 500 mL round bottom flask equipped with magnetic stirring and condenser are added 10 g (29.56 mmol) of the tricosanone as prepared in example 1 .1 .1 ., 120 mL of THF and finally 9.3 mL of DMAPA (73.8 mmol).

The mixture was stirred at room temperature during 1 hour in order to solubilize the ketone and 17.5 mL of Ti(0/Pr) ₄ (59.12 mmol) is added to the reaction mixture which is then stirred at room temperature during 12 hours.

50 mL of MeOH were then added to the mixture followed by the careful addition of 1 .7 g of NaBH ₄ (44.34 mmol). The resulting mixture was then stirred during 1 h00 and 250 mL of CH ₂ CI ₂ followed by 250 mL of H ₂ 0 are added into the reaction vessel. Upon addition of water a white precipate of Ti0 ₂ was formed which and then removed by filtration.

The organic phase of the filtrate is separated from the aqueous phase and is washed twice with 500 mL of aq. NaOH solution (0.5 M) followed by 500 mL of brine. The organic phase is dried over MgS0 ₄ , filtered and evaporated to give a pale yellow oil.

The product is finally purified by flash chromatography on silica gel using CH ₂ CI ₂ : MeOH as eluent (from 70:30 to 60:40) to obtain 6 g of the product as a transparent oil. (48% yield).

1.2.2. synthesis from C15-C35 ketones mixture

The same protocol was applied with the product as prepared in example 1 .2.1 starting from the compound as prepared in example 1 .1 .2

The diamines as obtained in examples 1 .2.1 and 1 .2.2. are suitable for emulsifying bitumen in water and allow to obtain cationic emulsion.