EP0750659A1 - Detergent/dispersant additives for alkylsalicylate-alkylphenate, alkaline-earth, sulfurized and overalkalinized-type lubricating oils - Google Patents

Abstract

Dispersant detergent additives for lubricating oils prepared by neutralization, carboxylation, sulfurization-overalkalinization, carbonatation, distillation, filtering and degassing from alkyl phenols containing 35-85 % by weight of liner alkyl substituents. The process does not require during the neutralizing phase the presence of a third solvent, which, by forming an azeotropic mixture with water, promotes the elimination of water arising from the neutralizing reaction. The additives of the invention have improved stability to hydrolysis and improved dispersion properties, improved compatability and improved foaming properties.

Description

Detergent-dispersant additives for lubricating oils of the alkylsalicylates-alkylphenates, alkaline-earth, sulphurized and over-alkalized type.

 The subject of the present invention is new detergent-dispersant additives for lubricating oils of the alkylsalicylates-alkylphenates, alkaline-earth, sulfurized and super-alkalized type having improved foaming properties, compatibility and dispersion in oils and stability to hydrolysis. as well as a process for their preparation.

 It is already known, from US-A-3,036,971, published on May 29, 1962, to prepare detergent-dispersant additives based on sulfurized alkylphenates of alkaline earth metals of high basicity, by sulfurization of an alkylphenol, neutralization of the sulfurized alkylphenol using an alkaline earth base, then over-alkalinization by carbonation of the alkaline earth base dispersed in the sulfurized alkylphenate; this type of product has the drawback of being not very stable on hydrolysis, with the formation of a precipitate of crystallized calcium carbonate, in particular when this type of product is highly over-alkalized, which entails risks of clogging of filters of marine engines. .

It is also known, from French patent 1,563,557, published on April 11, 1969, to prepare detergent additives based on sulfurized calcium alkylsalicylates by carboxylation of a potassium alkylphenate, exchange with calcium chloride, then sulfurization of calcium alkylsalicylate obtained with sulfur in the presence of lime, a carboxylic acid and an alkylene glycol or alkylene glycol alkyl ether; such a method has the drawback of requiring an exchange reaction.

 Under these conditions, the applicant has described in French patent application 2,625,220, published on June 30, 1989, a process for the preparation of overbased detergent-dispersant additives based on alkylphenates and alkylsalicylates, which comprises the following steps :

a) neutralization of a C ₈ -C ₃₀ alkyl substituted alkylphenol with an alkaline earth base, in the presence of a C ₁₈ -C ₁₈ acid and a solvent forming an azeotrope with the water of the reaction at a temperature corresponding to the reflux temperature of the azeotrope;

 b) distillation of the solvent;

 c) carboxylation using carbon dioxide under pressure to convert the alkylphenate to alkylsalicylate;

 d) sulfurization and over-alkalization with sulfur and an alkaline earth base in the presence of a glycol and a third solvent, followed by carbonation;

 e) and finally filtration.

 However, this process developed by the applicant, and the products obtained by this process have several drawbacks.

 First of all, in the neutralization step, the use of a solvent giving an azeotrope with water is necessary in order to obtain a sufficient conversion rate of the alkylphenol into the alkylphenate.

The carboxylation step is carried out at high pressures generally between 5 and 15 × 10 ⁵ Pa to convert the alkylphenate to alkylsalicylate.

 And the sulfurization and over-alkalization stage is dangerous from an industrial point of view because it gives rise to a brutal release of hydrogen sulphide that could not be controlled.

Finally, the products obtained by this prior process have dispersion and compatibility with lubricating oils lower than those of alkylsalicylates, having the same content of alkaline earth metals and above all, exhibited poor stability to hydrolysis, requiring frequent changes of the filters used in the lubrication circuits of marine engines.

 The applicant has now found that it could substantially improve the performance of these additives, in particular in the foaming, compatibility and dispersion tests in a new oil and in the hydrolysis stability tests, by preparing them by a method comprising the following steps:

 A) Neutralization of alkylphenols containing at least 35% and at most 85% by weight of linear alkylphenol in which the linear alkyl radical contains 12 to 40, and preferably 18 to 30 carbon atoms, mixed with at most 65 and at least 15% by weight of branched alkylphenol in which the branched alkyl radical contains 9 to 24 and preferably 12 carbon atoms, using an alkaline earth base, in the presence of at least one acid carboxylic containing from 1 to 4 carbon atoms, said neutralization operation being carried out at a temperature of at least 215ºC, with gradual vacuuming of the reactor in which the neutralization reaction is carried out, in order to remove the water from the reaction, in the absence of any solvent capable of forming an azeotrope with the latter. The amounts of reagents used correspond to the following molar ratios:

 alkaline earth base / total alkylphenol of between 0.2 and 0.7 and preferably between 0.3 and 0.5,

 - total carboxylic acid / total alkylphenol of between 0.01 and 0.5 and preferably between 0.03 and 0.15;

B) Carboxylation of the alkylphenate obtained in step A) to convert at least 22% and, preferably, at least 25% in moles of the starting alkylphenols to alkyl salicylate (measured as salicylic acid), by the action of carbon dioxide, at a temperature between 180 and 240ºC, preferably between 190 and 220 ° C, under a pressure which can range from atmospheric pressure to 15 × 10 ⁵ Pa (15 bars), for a period of one to eight hours, optionally in the presence of a dilution oil (100 N for example) added at the start or at the end of step A or of step B;

 C) Sulfurization and over-alkalization of the mixture of alkylphenate and alkylsalicylate obtained with elemental sulfur, in the presence of an alkaline earth base, of a mono-alcohol having a boiling point higher than 150ºC, and preferably higher at 175ºC, and optionally at this stage of an alkylene glycol or an alkylene glycol alkyl ether at a temperature between 145 and 180ºC, preferably between 150 and 160 ° C. The amounts of reagents used correspond to the following molar ratios:

 - sulfur / total alkylphenol of between 0.3 and 1.5 and preferably between 0.8 and 1.0;

 - total alkaline earth base / total alkylphenol of between 1.0 and 3.5 and preferably between 1.4 and 3.0;

- total alkaline earth base / mono alcohol with a boiling point above 150ºC between 0.3 and 0.5 then, after addition of the alkylene glycol or its alkyl ether if it has not already been added to a total alkaline earth / alkylene glycol base molar ratio of between 1.0 and 3.0 and preferably between 1.4 and 1.8, carbonation of the medium obtained by carbon dioxide at a temperature of 145 to 180ºC and under pressure close to atmospheric pressure, the quantity of CO ₂ used being between that which can be completely absorbed by the reaction medium and an excess of 30% of this quantity;

D) Elimination of the alkylene glycol and of the mono alcohol by distillation;

 E) Filtration to remove sediment;

 F) and finally degassing in air at a temperature between 80 and 160 ° C, preferably between 100 and 140ºC, until the rating of the copper strip is 1A tested according to ASTM D -130, performed for at least 15 minutes at 150ºC and preferably 1 hour at 150ºC.

 According to another aspect, the subject of the present invention is also a detergent-dispersant additive for lubricating oil of the alkaline-earth, sulphurized and over-alkalized alkylsalicylate-alkylphenate type, characterized in that

 a) the alkyl substituents of said alkylsalicylate-alkylphenate are in a proportion of at least 35% and at most 85% by weight of linear alkyl in which the number of carbon atoms is between 12 and 40, preferably between 18 and 30 carbon atoms, with a maximum of 65% by weight of branched alkyl in which the number of carbon atoms is between 9 and 24 and preferably 12 carbon atoms,

 b) in that the proportion of the alkylsalicylate in the alkylsalicylate-alkylphenate mixture is at least 22% and preferably at least 25% by moles and

 c) in that the molar proportion of alkaline earth base relative to the alkyl salicylate-alkylphenate group is between 1.0 and 3.5.

 The additives obtained according to the present invention can have a high basicity, reflected by the BN of these additives and measured according to standard ASTM-D2896 and which can easily reach values of 250 to 350 and even more.

 It will be noted that the additives according to the invention are based on alkaline earth metals, to the exclusion of any alkali metal, such as in particular sodium and potassium.

The Applicant has found that the improvement in foaming, compatibility and dispersion properties and hydrolysis stability of the additives thus obtained required the use of starting alkylphenols containing at least 35% and at most 85% by weight of alkylphenols in which the alkyl radical which contains from 12 to 40 carbon atoms is linear and unbranched.

 Indeed, it was conventional until now to use for the preparation of such additives alkylphenols in which the alkyl radical was generally a propylene tetramer, that is to say a branched dodecyl radical.

 However, the use of such a branched alkylphenol, insofar as it is present at more than 65% by weight in the starting alkylphenol, does not make it possible to obtain additives having the improved properties according to the invention;

 Branched alkylphenols, obtained by reacting phenol with a branched olefin containing 9 to 24 carbon atoms and generally coming from propylene, consist of a mixture of monosubstituted isomers in the vast majority in the para position, very little in the ortho position and practically no in the meta position, which makes them relatively reactive towards an alkaline earth base, since the phenol function is practically devoid of steric hindrance.

 On the other hand, linear alkylphenols, obtained by reaction of phenol with a linear olefin containing 12 to 40 and preferably 18 to 30 carbon atoms and generally coming from ethylene, consist of a mixture of monosubstituted isomers in which the proportion of linear alkyl substituents in ortho and para positions and even meta is much better distributed, which makes them much less reactive towards an alkaline earth base, since the phenol function is much less accessible due to congestion important steric due to the presence of closer and generally heavier alkyl substituents.

It is all the more surprising, in these conditions tions, to be able to obtain alkaline-earth alkaline additives from mixtures of alkylphenol which may contain up to 85% by weight of linear alkyl radical by eliminating, in the neutralization step, the third solvent forming an azeotropic mixture with l water and which was considered essential until now to react the branched alkylphenols, more reactive, with the alkaline earth base.

 The Applicant has achieved this by maintaining in this first neutralization step the presence of a carboxylic acid which serves as an agent for transferring calcium from an inorganic reagent to an organic reagent and by providing for more advanced reaction conditions, namely a temperature of at least 215 ºC with a progressive placing of the reactor under vacuum, so as to reach a very low absolute pressure of at most 7000 Pa (70 mbar), at this temperature in order to facilitate the elimination of the water.

 Among the alkaline earth bases which can be used to carry out the various stages of preparation of the additives according to the present invention, there may be mentioned the oxides or hydroxides of calcium, magnesium, barium or strontium and very particularly those of calcium.

In the context of the present invention, slaked lime corresponding to the chemical formula Ca (OH) ₂ is preferred and will be used by way of illustration in the various examples under the name of lime.

Among the C ₁ to C ₄ carboxylic acids used in the neutralization step, mention may be made of formic, acetic, propionic and butyric acids, which can be used alone or as a mixture.

It is preferred to use mixtures of these acids, for example the formic acid-acetic acid mixture, according to a molar ratio of acetic acid / formic acid of between 0.01 and 5, preferably between 0.25 and 2 and very particularly of the order of 1, as described in particular in French patent 2625220, requested on December 23, 1987 by OROGIL Company.

 As examples of alkylene glycols suitable for the sulfurization-over-alkalization stage, mention may be made of ethylene glycol, propylene glycol, butylene glycol.

 Finally, among the monoalcohols having a boiling point greater than 150 ° C. to be used in this same sulfurization-overalkalinization stage, mention may be made of C6-C14 alkanols or cycloalkanols such as ethyl-2-hexanol, oxo alcohols, diethyl alcohol, tridecyl alcohol, trimethylcyclohexanol; alkylene glycol ethers such as butoxy-2 ethanol, butoxy-2 propanol, hexyloxy-2-ethanol and methyl ethers of dipropylene glycol.

 The first neutralization step A) of the alkylphenol is characterized by the use of a particular alkylphenol and reaction conditions, in particular of well determined temperature and pressure.

 Indeed, the use of an alkylphenol having a content of at least 35% by weight and which can range up to 85% in linear alkylphenol, in particular in which the linear alkyl radical contains a large number of carbon atoms ( of 18 to 30 carbon atoms) is particularly interesting since a long linear alkyl chain promotes the compatibility and the solubility of the additives in lubricating oils.

 However, the presence of relatively heavy linear alkyl radicals in the alkylphenols makes the latter less reactive than branched alkylphenols, hence the need to use more vigorous reaction conditions to neutralize them with an alkaline earth base.

The neutralization reaction is carried out at a temperature of at least 215ºC, with progressive vacuuming, so as to reach a very low pressure of at most 7000 Pa (70 mbar) at 215ºC. Step A) of neutralization can be carried out at a temperature of at least 220ºC with progressive vacuuming, so as to reach a very low pressure of at most 7000 Pa (70 mbar) at 220ºC.

 Particularly advantageous conditions of implementation consist in carrying out the neutralization step A) at a temperature of at least 225ºC, with progressive evacuation, so as to reach a very low pressure of at most 7000 Pa (70 mbar) at 225ºC.

 According to another embodiment, the neutralization step A) is carried out at a temperature of at least 240ºC with progressive evacuation, so as to reach a very low pressure of at most 7,000 Pa (70 mbar) at 240ºC

At the end of this neutralization step, the alkylphenate obtained is preferably maintained for a period not exceeding 15 hours, generally between 2 and 6 hours, at a temperature of at least 215ºC and an absolute pressure included between 5,000 and 10 ⁵ Pa (0.05 and 1.0 bar), in particular between 10,000 and 20,000 Pa (0.1 and 0.2 bar).

Indeed, under these conditions, it is possible to obtain, in the presence of the indicated proportion of C ₁ to C ₄ carboxylic acid, a transformation, at a sufficient rate, of the alkylphenol into the alkylphenate, which conditions the final content of the additive in alkaline earth metal and therefore its properties of detergent-dispersing agent in oils.

 Provided that the temperature is sufficiently high and that the reactor is placed under vacuum, the neutralization reaction is carried out without it being necessary to add a third solvent forming an azeotrope with water in this step. formed during this reaction.

The second carboxylation step B) aims to transform part of the alkylphenate into alkylsalicylate by simple bubbling of carbon dioxide in the reaction medium from the previous neutralization step. It must take place under pressure to avoid any decarboxylation of the salicylate which forms.

This carboxylation reaction of an alkylphenate containing at least 35% of relatively inert and heavy linear alkylphenate, requires heating to a temperature which must be higher the less the pressure in the reactor. Thus if we want to limit the pressure in the reactor to 3.5.10 ⁵ Pa (3.5 bar) maximum, it is necessary to operate at a temperature equal to or higher than 190ºC.

According to a variant, step B) of carboxylation is carried out using carbon dioxide at a temperature equal to or greater than 200ºC, under a pressure of 4 × 10 ⁵ Pa (4 bars)

 During this carboxylation step, the transformation of the alkylphenate into alkylsalicylate may involve the formation of alkylphenol, which should be converted to the alkylphenate in the next step.

The third step (C) of the process for preparing the additives according to the present invention is divided into a reaction C ₁ of sulfurization and over-alkalization followed by a reaction C ₂ of carbonation.

The reaction C ₁ of sulfurization and over-alkalization is dangerous on an industrial scale because the addition of elemental sulfur to the reaction mixture at a temperature between 145 and 180 ° C results in a release of hydrogen sulfide which can only be controlled under certain conditions.

The Applicant has found that this reaction could be controlled after the product obtained at the end of the carboxylation step has cooled to approximately 155 ° C., by loading elemental sulfur at this temperature and then gradually over a period of 1 to two hours, a mixture of the alkaline earth base, of a mono-alcohol with a boiling point higher than 150ºC, at a temperature of 150 to 160ºC and possibly alkylene glycol.

 Stopping the loading of this mixture causes the release of hydrogen sulfide to stop

 Such an implementation of the sulfurization and over-alkalization reaction makes it possible to incorporate approximately 50 mol% of sulfur reacted in the alkylsalicylate-alkylphenate obtained, the remaining 50% being eliminated in the form of hydrogen sulfide.

 Insofar as the sulfur is used in a molar proportion of 0.5 to 1.5 or even 0.8 to 1.0 relative to the starting total alkylphenol, this means that one finds in the alkylsalicylate- alkaline earth alkylphenate, sulfurized and superalkalized a molar proportion between 0.25 and 0.75, even between 0.4 and 0.5.

 Although the Applicant is not bound by any scientific explanation, it can be assumed that during the stages of the process for the preparation of the additives according to the present invention, the main chemical reactions are the following:

 during neutralization:

 where AA / AF denotes a mixture of acetic acid and formic acid and where (II) is in the majority proportion and (I) in the minority proportion.

- during the carboxylation:

- and during sulfurization / over-alkalization:

in majority proportion

in a minority proportion The carbonation reaction C ₂ by bubbling carbon dioxide in the reaction medium containing an excess of alkaline earth base relative to the alkylphenol which reacted with sulfur at a temperature of 145 to 180 ° C. requires the presence of alkylene glycol which must be added in this step C ₂ if it has not been added in C ₁ ; the purpose of this step C ₂ is to transform the additional alkaline earth base into alkylphenate and finely divided calcium carbonate, the latter being trapped between the sulfurized alkylphenate and alkylsalicylate molecules and thus causing the alkalinization of the additive .

 The purpose of the fourth distillation step D is to eliminate the alkylene glycol and the mono-alcohol introduced into the reaction medium during the previous step to facilitate the sulfurization, the over-alkalization and the carbonation of the additive according to the present invention.

 The purpose of the fifth filtration step E is to get rid of the sediments and in particular of the crystallized calcium carbonate which could have formed during the previous steps and which clogs the filters installed on the lubrication oil circuits.

 Finally, the sixth and final step of air degassing F is important because it allows the additive to pass the hydrolysis stability test, which is not the case for an additive that would be manufactured exclusively from a branched alkylphenol such as dodecylphenol obtained by addition of the propylene tetramer on phenol.

The present invention also relates to the corresponding process for the preparation of these additives and of lubricating oil compositions, in particular for marine engines, but also for automobiles and railways containing a major proportion of lubricating oil and from 2 to 20% by weight. of a dispersing detergent additive according to the invention. These additives can also be used in applications industrial products such as hydraulic oils in proportions that vary from 0.1 to 3% by weight.

 The following examples illustrate particular implementations of the invention and are intended to assist those skilled in the art to obtain additives which are the subject of the present invention.

EXAMPLE N'1

A) Neutralization:

 875 g of dodéσylphenol (DDP) of molecular weight 270, or (3.24 moles) and 875 g of linear alkylphenol of molecular weight 390 are charged into a 4-liter tetracol glass reactor, topped with a vigorous heat-insulating material. (i.e. 2.24 moles).

 The agitator is started and heated to 65ºC; at this temperature, 158 g of lime Ca (OH) 2 (i.e. 2.135 moles) and 19 g of a mixture (50/50 by weight) of formic acid and acetic acid are added.

 Heating of the reaction medium is continued at 120 ° C., the temperature at which the reactor is placed under a nitrogen atmosphere, then up to 165 ° C., where the nitrogen atmosphere is stopped; at this temperature, the distillation of water begins.

 The temperature is raised to 220ºC and a vacuum is gradually produced until an absolute pressure of 5,000 Pa (50 mbar) is obtained.

 The reaction mixture is kept for 5 hours under the preceding conditions.

 It is allowed to cool to 180ºC then the vacuum is broken under a nitrogen atmosphere and a sample is taken for analysis.

The total amount of distillate obtained is approximately 114 cm ³ ; demixing occurs in the lower phase (62 cm ³ being water).

B) Carboxylation:

The product obtained in step A) is transferred to a 3.6 1 autoclave and heated to 180ºC.

 At this temperature, one begins to sweep the reactor with carbon dioxide (CO2) for 10 minutes. The amount of CO2 used in this step is of the order of 20 g.

After having brought the temperature to 200ºC, the autoclave is closed, leaving a minimal leak and the introduction of the CO2 is continued so as to maintain a pressure of 3.5 × 10 ⁵ Pa (3.5 bar) for 5 hours at 200ºC.

 The amount of CO2 introduced is of the order of 50 g. After cooling the autoclave to 165ºC, it is decompressed to atmospheric pressure and then purged with nitrogen.

 A total amount of product of 1916 g is recovered. C1) Sulfurization and Suralcalinization:

 1114 g of the product obtained in step B) are transferred to a 4 l tetracol glass reactor, equipped with a heating system and an agitator.

 After starting the heating, 487 g of 100 N oil and 0.2 g of antifoam are introduced with stirring.

At 155 ° C., 90 g of sulfur (2.81 moles) are charged and a slight vacuum of 0.96 × 10 ⁵ Pa (960 mbar) is put under. In a beaker, a mixture of 193.6 g of glycol, 273 g of lime and 589 g (including 200 of rinsing) of 2-ethylhexanol is prepared separately.

 Said mixture is added over 1 hour 30 minutes to the reactor while maintaining the temperature at 155 ° C. under the same slight depression. A release of hydrogen sulfide is observed.

 After introduction of the mixture, the temperature is increased to 170 ° C. in 1 hour and, during this step, 170 g of distillate are collected which separates into two phases, the lower phase of which contains water and glycol. One remains one hour under the above conditions, then it returns to atmospheric pressure.

C2 Carbonation: 101 g of carbon dioxide are introduced at a flow rate of 0.9 g / min (approximately).

 The total amount of distillate collected is 190 g, which separates into an aqueous phase of 100 g of a mixture of water and glycol and an organic phase of 90 g of 2-ethylhexanol.

 D) Elimination of σlvcol and 2-ethylhexanol

 The mixture is heated to 195ºC while gradually vacuuming until an absolute pressure of 5,000 Pa (50 mbar) is obtained.

 The above final conditions are maintained for one hour and a sample is taken to determine the percentage of raw sediment which is 1.2%.

E) Pressure filtration (4.10 ⁵ Pa at 150ºC)

F) Air degassing:

 The above product is degassed in air at 110ºC for 6 hours until a copper blade of 1A is obtained in the standardized test ASTM D 130 carried out under the following conditions: 15 minutes at 150ºC.

 The final additive obtained had the following characteristics:

 ANALYZES OF THE PRODUCT OBTAINED IN EXAMPLE 1:

EXAMPLE # 2:

A) Neutralization

A 5.15 reactor is charged with 875 g of dodecylphenol (the alkyl chain of which is propylene tetramer), 875 g of linear alkylphenol (the starting olefin being a cut of linear alpha-olefin C ₂₀ - C ₂₈ from the company CHEVRON CHEMICAL), 158 g of lime and 22 g of a formic acid / acetic acid mixture (each of the 2 acids being equal in weight); this last component must be added at a temperature less than or equal to 80ºC. The heating and the agitator are started and a light nitrogen sweep is carried out to expel the air from the reactor.

 At 170ºC, the first drops of distillate appear. At 220ºC, the nitrogen delivery is stopped and the vacuum is started.

 The maximum vacuum is reached after about one hour and the product is left for 4 hours under the above conditions.

The distillate collected consists of 2 layers, namely an upper layer of 60 cm ³ consisting mainly of alkylphenol and a lower layer of 80 cm ³ consisting mainly of water.

 After breaking the vacuum with nitrogen, the product is cooled to 200ºC and a sample is taken to determine the percentage of sediment which is 2.8%.

 B. Carboxylation

The reactor is purged with CO2 for 15 minutes then it is placed under a pressure of 3.5 × 10 ⁵ Pa (3.5 bars) of CO 2 which is maintained for 5 hours under these conditions, before decompressing.

 C. Sulfurization - Suralcalinization

 800 g of the above carboxylated product are drawn off in another reactor and 350 g of oil are added.

 In a beaker, a mixture of 334 g of 2-ethylhexanol, 139 g of glycol and 196 g of lime is prepared separately with stirring.

 The heating of the reactor is started.

 At 155ºC, 64 g of sulfur (2 moles) are loaded, then after a waiting period of 10 minutes, the above mixture is introduced by modulating the flow rate for 1 hour and a half so that the temperature variation is between 152 and 158º C.

Let the reactor temperature rise to reach 170ºC After the loading of the lime-containing mixture has finished, there are two hours of sulfurization.

 The introduction of CO2 is carried out in 1.5 hours at 170ºC. The percentage of sediment is 1%.

D) Ethylene glycol and 2-ethylhexanol are removed by distillation. The final conditions are lh at 195ºC under 8000 Pa (80 mbar). The percentage of sediment is 1%.

E) The product thus obtained is filtered under pressure.

F) The above product is degassed in air at 120ºC for 6 hours. A sample is taken there to verify the ASTM D 130 copper blade test, carried out under the following conditions: 15 minutes at 150ºC.

 The additive obtained has the following characteristics:

EXAMPLES # 3. 4. 5. 6 and 7:

 STEP A): NEUTRALIZATION

 In a 500 l reactor, the following are charged with stirring and in order:

 - 87.5 kg of dodecylphenol,

 - 87.5 kg of linear alkylphenol (the same as that used in Example 2)

 - 15.8 Kg of lime,

 - 1, 1 Kg of formic acid

 - 1, 1 Kg of acetic acid

Formic and acetic acids are charged to a temperature below 80 ° C.

 The reactor heating is started and maintained at 220ºC. As soon as this temperature is reached, a vacuum is started until a pressure of 6000 Pa (60 mbar) is obtained, which requires approximately 1 hour. The reactor is maintained for 4 hours under the above conditions and then the vacuum is broken with carbon dioxide.

 STEP B: CARBOXYLATION

The conditions are 5 hours at 200ºC under a pressure of 3.5 × 10 ⁵ Pa (3.5 bar) of CO2.

 The reactor is decompressed and cooled. The product is then transferred to a storage tank. Part of this product will be taken back for step C.

 STEP C: SULFURIZATION - OVERCALINATION

 Charges:

 The carboxylated product and the oil are loaded into the reactor; it is stirred and heated.

 Furthermore, a premixture of 2-ethylhexanol 1, glycol to which lime is added with stirring, in the proportions indicated above, is prepared in a separate container.

 When the temperature reaches 135ºC, the reactor is placed under slight vacuum (96,000 Pa, or 960 mbar)

 - At 155 ° C., the premix is introduced into the reactor, in approximately 1 hour, then the piping is rinsed with 2-ethylhexanol 2.

The reactor is then heated to 170ºC and maintained for 2 hours under these conditions. The introduction of CO2 is finally carried out in 1 hour 30 minutes.

 STEP D:

 Ethylene glycol and 2-ethylhexanol are removed by distillation. The final conditions are 1 hour at 195ºC under 6000 Pa (60 mbar).

 STEP E:

 The product is filtered at 150ºC under a pressure of 4 bars. The percentage of sediment is 2.4%.

 STEP F:

 The above product is degassed in air at 120ºC until a copper blade of rating 1A is obtained in the ASTM D130 test, carried out under the following conditions: 1 hour at 150ºC.

 The main variant of tests 3, 4, 5, 6 and 7 is located in the neutralization phase.

 nº3 - heating to 220ºC then vacuum.

 # 4 - vacuuming starts at 180ºC. nº5 - reduction of the lime load. nº6 - reduction of the lime load, the vacuum starts at 165ºC.

 # 7 - Same as # 6, but reflux is introduced at the top of the column leading from the reactor to the condenser to decrease the loss of alkylphenol.

 The results of these tests are shown in Table I.

Example 8

 STEP A: NEUTRALIZATION

 In a 500 L reactor, we load:

 - 87.4 Kg of dodecylphenol

- 87.4 Kg of linear C ₂₀ -C ₂₈ alkylphenol

 It is heated to 80ºC and then 18 kg of lime are introduced (calcium hydroxide: Ca (OH2); it is stirred and charged

0.53 Kg of acetic acid and 0.37 Kg of formic acid as well as 66 Kg of 100 N oil. After heating to 220ºC, vacuum is gradually applied until a pressure of 5,000 Pa (50 mbar) is obtained and the above conditions are maintained for five hours.

 STEP B: CARBOXYLATION

 This phase is carried out under the following conditions: 200ºC under a pressure of 3.5 × 10 Pa (3.5 bars) - duration: 7 h 00

 STEP C: SULFURIZATION / OVERALCALINIZATION The process used is that described in Example 1, with the exception of the fillers.

 These are from:

 - 100 Kg of product from step B,

 - 6 Kg of 100N oil,

 - 12 Kg of calcium sulfonate of TBN about 20

- 18 kg of hydrated lime,

 - 12.8 Kg of glycol,

 - 5.6 Kg of sulfur,

 - 6.5 Kg of carbon dioxide,

 - 23 Kg 2-ethylhexanol-1

 - 15 Kg 2-ethylhexanol-2

 The other steps, D: Elimination of glycol and 2-ethylhexanol, E: Filtration and F: Degassing, are identical to that described in Example 1.

 The analyzes obtained on the filtered and degassed product are as follows:

 EXAMPLES 9. 10 and 11:

 INFLUENCE OF SULFURIZATION TEMPERATURE

We operate under the same conditions as those described in steps A and B of Example 4 and we divide then, in three equal fractions, part of the product obtained at the end of step B of carboxylation.

 Then all of the following steps are continued as described in this same example 4, with the difference that, in the first fraction (example 9) the sulfurization is carried out at a temperature of 165ºC, in the second fraction (example 10) at a temperature of 155ºC and in the third fraction (example 11) at a temperature of 145ºC.

 From an analytical point of view, as the results of the analyzes shown in the table show, no really significant difference is observed on the final product.

 EXAMPLE 12:

The procedure is identical to Example 1, with the difference that in step C of sulfurization / carbonation, the lime is added first, then the glycol and ethylhexanol gradually. From an analytical and performance point of view, no really significant difference is observed on the final product.

COMPARATIVE EXAMPLE 13

 We repeat the experiment which is the subject of the example

7 of French patent 2,625,220 of the applicant, already cited above.

 The main characteristics of the process followed in this example are a mixture of alkylphenols containing 30% linear alkylphenol, a neutralization temperature between 145 and 195ºC and the use of 2-ethylhexanol as azeotropic solvent.

 The results obtained show that the neutralization temperature is too low to significantly react the linear alkylphenols.

 Likewise, the experiment which is the subject of Example 1 of US-A-4,902,436 from the company COSMO OIL is repeated.

 Again the neutralization temperature, which was 160ºC for 3 hours, did not allow the starting alkylphenols to participate significantly in the reaction with calcium oxide.

EXAMPLES 14 to 18

 A series of examples 14 to 18 was carried out to determine the influence of the neutralization temperature, this being respectively 180 ° C. for example 14, of

200ºC for Example 15, 220 ° C for Example 16, 230ºC for Example 17 and finally 240 ° C for Example 18.

 The operating conditions and the results obtained in each of these examples 14 to 18, among which only examples 16 to 18 represent implementations according to the present invention, appear in Table III below.

The operating conditions, with regard to Example 16, are specified in the description which follows. EXAMPLE 16

 A) Neutralization:

875 g of dodecylphenol (DDP) of molecular weight 270 ((3.24 moles) and 875 g of linear alkylphenol of molecular weight 390 approximately are charged into a 4-liter glass tetracol reactor surmounted by a vigorous thermal insulation. (i.e. 2.24 moles) corresponding to a cut of C ₂₀ -C ₂₈ alpha olefins. The agitator is put at 350 revolutions per minute and heated to 65ºC; at this temperature, 139 g of lime Ca (OH) 2 (i.e. 1.878 moles) and 18.9 g of a mixture (50/50 by weight) of formic acid and acetic acid (i.e. 0.36 mole) are added. of this mixture).

 Heating of the reaction medium is continued at 120 ° C., the temperature at which the reactor is placed under a nitrogen atmosphere, then up to 165 ° C., where the nitrogen atmosphere is stopped; at this temperature, the distillation of water begins.

 The temperature is raised to 220ºC in 1 hour, gradually vacuuming until an absolute pressure of 5,000 Pa (50 mbar) is obtained.

 The reaction mixture is maintained for 3 hours under the preceding conditions.

 It is allowed to cool to 180ºC then the vacuum is broken under a nitrogen atmosphere and a sample is taken for analysis.

The total amount of distillate obtained is approximately 94 cm ³ ; demixing occurs in the lower phase (51 cm ³ being water). 640 g of 100 N oil are then added.

 B) Carboxylation:

 The product obtained in step A) is transferred to a 3.6 L autoclave and heated to 180 ºC.

 At this temperature, one begins to sweep the reactor with carbon dioxide (CO2) for 10 minutes. The amount of CO2 used in this step is of the order of 20 g.

After bringing the temperature to 200 ° C, we close the autoclave leaving a minimal leak and the introduction of the CO2 is continued so as to maintain a pressure of 3.5 × 10 ⁵ Pa (3.5 bar) for 6 hours at 200ºC.

 The amount of CO2 introduced is of the order of 50 g. After cooling the autoclave to 165ºC, it is decompressed to atmospheric pressure and then purged with nitrogen.

 A total quantity of product of 2513 g is recovered.

 C) Sulfurization and Suralcalinization:

 1516 g of the product obtained in step B) are transferred to a 4 l glass tetracol reactor, equipped with a heating system and an agitator (600 revolutions per minute).

 After starting the heating, 91 g of 100 N oil and 0.2 g of anti-foaming agent are introduced with stirring.

At 110ºC, 90.5 g of sulfur are charged and a slight vacuum of 0.96 × 10 ⁵ Pa (960 mbar) is placed. In a beaker, a mixture of 193.6 g of glycol, 304 g of lime and 589 g (including 200 of rinsing) of 2-ethylhexanol is prepared separately. Said mixture is added over 1 hour to the reactor while maintaining the temperature at 155ºC under the same slight vacuum. A release of hydrogen sulfide is observed.

 After introduction of the mixture, the temperature is increased to 170ºC in 1 hour and, during this step, 170 g of distillate are collected which separates into two phases, the lower phase of which contains water and glycol.

 One remains one hour under the above conditions, then it returns to atmospheric pressure.

 Carbonation:

 103 g of carbon dioxide are introduced at a flow rate of 0.9 g / min (approximately).

The total amount of distillate collected is 220 cm ³ which separate into an aqueous phase of 90 cm ³ of a mixture of water and glycol and an organic phase of 130 cm ³ of 2-ethylhexanol. D) Elimination of glycol and 2-ethylhexanol

 The mixture is heated to 195ºC while gradually vacuuming until an absolute pressure of 5,000 Pa (50 mbar) is obtained.

 The above final conditions are maintained for one hour and a sample is taken to determine the percentage of raw sediment which is 1.6%.

E) Pressure filtration (4.10 ⁵ Pa at 150ºC).

A wire mesh filter and a filter aid are used.

 F) Air degassing:

 The above product is degassed in air at 110ºC for 16 hours until a copper blade of 1A is obtained in the standardized test ASTM D130 carried out under the following conditions: 60 minutes at 150ºC.

 The final additive obtained had the following characteristics:

 ANALYZES OF THE PRODUCT OBTAINED IN EXAMPLE 16

 EXAMPLES 19 to 22

 Another series of experiments was also carried out according to Examples 19 to 22, which aimed to determine the influence of the relative proportion of linear alkylphenols in the mixture of starting alkylphenols.

 Thus, this proportion was 0% in Example 19, 20% in Example 20, 80% in Example 21 and 100% in Example 22. Only Examples 16 and 21 are part of the invention.

The operating conditions were the same as those used in Example 16, described above, in which the relative proportion of alkylphenols in the mixture of starting alkylphenols was, let us recall, 50% in weight.

 These conditions and the results obtained are shown in Table III below.

 DESCRIPTION OF THE PERFORMANCE TESTS

1. HYDROLYSIS STABILITY: MAO 29

 This method is inspired by the ASTM D method

2619 modified. Its purpose is to study the sensitivity to water of an oil and is applicable to marine oils.

 The method consists in introducing a sample of oil with demineralized water into a bottle and stirring it in a thermostatically controlled oven. At the end of the test, the sample is dried, filtered and analyzed. The hydrolysis stability is expressed by: the presence or absence of crystallized carbonate, characterized by IR spectrometry. The results are qualified as "GOOD" in the absence of crystallized carbonate and "BAD" in the presence of the latter.

 2. MAO 60A DISPERSION:

 The purpose of this method is to assess the dispersive properties of an oil or an additive and to predict its level of performance (deposits, sludge) compared to a reference oil.

 It is generally applicable to terrestrial and marine engine oils.

 According to this method, the dispersive power of the oil is obtained by performing a paper chromatography of a mixture of oil to be tested and artificial mud under the following conditions:

The spots are observed after 48 hours of rest, manually or using the CCD photometer. On each spot, the diameter (d) of diffusion of the mixture is measured and the diameter (D) of diffusion of the oil alone and the ratio d / D × 100 is calculated.

 The dispersive power of the oil is obtained by comparing the sum of the 6 spots with the value found on one of the reference oils which will have to be tested in the same measurement series.

 The addition of the d / D × 100 ratios under the six conditions listed above corresponds to a maximum dispersive power of 600, corresponding to an ideal dispersion of 100% under all conditions. In the results of this test, the higher the number, the better the dispersibility of the oil.

 3. MAO COMPATIBILITY 25

 The purpose of this method is to assess the appearance and storage stability of the additives and the corresponding oils containing them.

 This method is applicable to additives for lubricants.

 In this method the additive and the corresponding oil containing it are stored simultaneously at room temperature and hot for a determined period.

 The appearance of the products is evaluated before and after storage and the results are qualified as "GOOD" or "BAD" depending on whether or not a single phase is maintained without sedimentation.

 4. FOAMING

The method used to determine whether a given compound gives rise to foaming is the standardized method ASTM-D 892, in which the lower the number, the better the product.

On reading the results obtained in Examples 14 to 18 intended to measure the influence of the neutralization temperature, the following comments can be made.

 It appears that the salicylate content expressed in the form of a salicylic acid index at the end of carboxylation step B increases with the neutralization temperature to give the following respective results 12, 23, 26, 29 and 31 ( mg KOH / g product).

 On the other hand, it clearly appears that the neutralization temperature range (145ºC - 195ºC) used in the aforementioned French patent 2,625,220 is clearly insufficient for the neutralization of the linear alkylphenol by lime. This is highlighted by the percentage of raw sediment (figure which accounts for the incorporation of lime) and the success or failure of the hydrolysis stability test, as shown in the table below:

 A reduction in the foaming of the finished product will also be noted when the neutralization temperature increases, this is explained by a greater reactivity of the linear alkylphenols at high temperature and it is generally known that the linear products are less foaming than the branched products. In addition, infrared spectroscopy shows a decrease in the content of orthoalkylphenols (mainly from the linear product) when the neutralization temperature increases.

On the other hand, on reading the results obtained in examples 19, 20, 16, 21 and 22, the following comments can be made.

 In the examples in question, only the proportion of linear alkylphenols in the starting mixture which included linear alkylphenols and / or branched alkylphenols varied, as shown in the table below:

 The other parameters that have been kept constant in these examples are:

a) in the neutralization step (A):

 the amount by total weight of branched alkylphenol and linear alkylphenol

. the amount of dilution oil

b) at the carboxylation stage (B): the CO2 pressure and the other operating conditions

 c) at the sulfurization and over-alkalization stage (C): the charges of the various reagents and the operating conditions.

 The aim pursued in the choice of these different parameters for Examples 19, 20, 16, 21 and 22 was to obtain a product satisfying the following four performance tests:

 . hydrolysis stability MAO 29

 . dispersion in new oils MAO 60A; the higher the number, the better the product.

. MAO 25 compatibility (pass = good, or failure = bad). . ASTM D 892 foaming - the lower the number, the better the product.

 The results obtained in said examples can be summarized in the table below:

We first observe that the neutralization reaction is much more complete with branched alkylphenols than with linear alkylphenols, which is confirmed by the following 4 analyzes.

 - BN ASTM D 2896 which, after removal of unreacted lime by filtration, reports on the basicity of the medium. - The percentage of sediment by volume, that is to say the unreacted lime.

- The amount of water collected which comes from the base acid reaction: (Alkylphenol + lime). - The salicylate content expressed as salicylic acid mg KOH / g produced in the final product.

The above results were partly predictable because the branched alkylphenol with a shorter, therefore more reactive chain, consists mainly of 86% of the para isomer and 8% of the ortho isomer, whereas the linear alkylphenol consists of Only 45% of the para isomer and 55% of the ortho isomer. Neutralization of the ortho isomer is much more difficult due to steric hindrance.

 On the other hand, there is an unexpected improvement in the stability to MAO 29 hydrolysis and in MAO 25 compatibility following an increase in linear alkylphenol as well as an improvement in foaming and dispersion MAO 60A when the relative starting proportion passes. from 0 to 80% of linear alkylphenols.

 Example 20 in which the proportion of linear alkylphenol in the starting alkylphenol mixture was only 20% by weight does not make it possible to obtain satisfactory results in the tests of stability to MAO 29 hydrolysis and of compatibility MAO 25.

 Additional tests have made it possible to determine that the minimum proportion of linear alkylphenol in the starting alkylphenol mixture must be at least 35% by weight to obtain satisfactory results in all of the tests appearing in the preceding table and in particular those of MAO 29 hydrolysis stability and MAO 25 compatibility.

On the other hand, we also observe, quite surprisingly, that the chemical mixture of linear and branched alkylphenols 50/50 by weight (example 16) has, with respect to the physical mixture: unexpected analytical behavior, the results being significantly better, as shown by the results summarized in the table below:

These performances of the 50/50 chemical mixture are all the more unexpected since the physical mixture does not pass the compatibility and hydrolysis stability tests, while the chemical mixture (example 16) passes them. In addition, in the foaming and dispersion tests an unexpected phenomenon is observed: the results improve when the level of linear alkylphenol increases to deteriorate markedly for the 100% linear alkylphenol products. It is therefore necessary to admit a synergy between the simultaneous presence of linear alkylphenols and branched alkylphenols in the neutralization phase and on the performance of the finished products.

 Although the Applicant does not wish to be bound by any explanation, it offers the following explanation of the synergy between linear alkylphenol and branched alkylphenol.

During the neutralization step, the neutralization of the linear alkylphenol is weak for the following reasons: low reactivity due to the length of the chain and to the preponderant presence of ortho isomer; furthermore, due to its high molecular weight, the entrainment effect of the reaction water is weak. On the other hand, the introduction of a branched alkylphenol into the medium improves the rate of conversion of the linear alkylphenol to alkylphenate for the following reasons:

 The lime first reacts with a branched alkylphenol R-∅-OH to yield the following product (I):

which being more basic than lime in an organic medium allows the neutralization of a 2nd mole alkylphenol R'-∅-OH which can be linear.

In addition, the relative volatility of the branched alkylphenol at this temperature facilitates the removal of water.

 Another proof of the synergistic effect due to the presence of a mixture of branched alkylphenol and linear alkylphenol and observed at the lime neutralization stage is BN ASTM D 2896 which accounts for the incorporation lime, because this analysis is carried out after filtration, that is to say removal of unreacted lime.

The table below gives the BN (ASTM D2896) obtained on the one hand for pure branched alkylphenol then for pure linear alkylphenol on the other hand for mixtures 20/80 50/50 and 80/20 by weight.

 We observe that the more the linear fraction increases, the more the difference between the real BN and the theoretical BN (20/80, 50/50 and 80/20) increases.

Claims

1. Detergent-dispersant additives for lubricating oils of the alkylsalicylates-alkylphenates, alkaline-earth, sulphurized and super-alkalized type, characterized in that they can be obtained by a process comprising the following stages:

 A) neutralization of alkylphenols containing at least 35% and at most 85% by weight of linear alkylphenol in which the linear alkyl radical contains 12 to 40 and preferably 18 to 30 carbon atoms, mixed with at most 65 and at minimum 15% by weight of branched alkylphenol in which the branched alkyl radical contains 9 to 24 and preferably 12 carbon atoms, using an alkaline earth base in the presence of at least one acid chosen from acids carboxylic containing from 1 to 4 carbon atoms, said neutralization operation being carried out at a temperature of at least 215ºC, with progressive placing in vacuum of the reactor in which the neutralization reaction is carried out in order to remove water from the reaction, in the absence of any solvent capable of forming an azeotrope with the latter. The amounts of reagents used correspond to the following molar ratios:

 - total alkaline earth / alkylphenol base between 0.2 to 0.7 and preferably between 0.3 and 0.5;

 - total carboxylic acid / total alkylphenol between 0.01 to 0.5 and preferably between 0.03 and 0.15.

B) carboxylation of the alkylphenate obtained in step A) to transform at least 22% and preferably at least 25% into moles of the starting alkylphenols into alkylsalicylate (measured as salicylic acid) using gases carbon dioxide at a temperature of 180 to 240ºC, preferably between 190 and 220 ° C, under a pressure which can range from atmospheric pressure to 15 × 10 ⁵ Pa (15 bars) for a period of one to eight hours, in the presence eventually a 100N dilution oil added at the start or end of step A) or step B;

 C) sulfurization and over-alkalization of the mixture of alkylphenate and alkylsalicylate obtained by elemental sulfur in the presence of an alkaline earth base, of a mono-alcohol having a boiling point higher than 150ºC and preferably higher than 175ºC and optionally, at this stage, an alkylene glycol or an alkylene glycol alkyl ether, at a temperature between 145 and 180ºC, preferably between 150 and 160ºC. The amounts of reagents used correspond to the following molar ratios:

 - sulfur / total alkylphenol between 0.3 to 1.5 and preferably between 0.8 and 1.0;

 - total alkaline earth base / total alkylphenol between 1.0 to 3.5 and preferably between 1.4 and

3.0;

- total alkaline earth base / mono-alcohol with a boiling point higher than 150ºC between 0.3 and 0.5 then after addition of the alkylene glycol or its alkyl ether if it has not already been added in a total alkaline earth / alkylene glycol base molar ratio of between 1.0 and 3.0 and preferably of between 1.4 and 1.8, carbonation of the medium obtained by carbon dioxide at a temperature of 145 to 180ºC and under pressure close to atmospheric pressure, the amount of CO ₂ used being between that which can be completely absorbed by the reaction medium and an excess of 30% of this amount;

 D) elimination of the alkylene glycol and of the monoalcohol by distillation;

 E) filtration to remove sediment;

 F) and finally degassing in air at a temperature between 80 and 160 ° C, preferably between 110 and 140ºC, until the rating of the copper strip is 1A tested according to ASTM D 130 carried out for at least 15 minutes at 150 ° C and preferably 1 hour at 150ºC.

2. Additive according to claim 1, characterized in that the neutralization stage A) is carried out at a temperature of at least 220ºC with progressive vacuuming, so as to reach a very low pressure of at most 7,000 Pa (70 mbar) at 220 ° C.

 3. Additive according to claim 2, characterized in that step A) of neutralization is carried out at a temperature of at least 240ºC with progressive evacuation, so as to reach a very low pressure of at most 7000 Pa (70 mbar) at 240ºC.

4. Additive according to claim 1, characterized in that at the end of step A) of neutralization, the alkylphenate obtained is maintained for a period not exceeding 15 hours and preferably between 2 and 6 hours, at a temperature of at least 220ºC and under a pressure between 5,000 and 10 ⁵ Pa (0.05 and 1.0 bar), preferably between 10,000 and 20,000 Pa (0.1 and 0.2 bar) .

5. Additive according to any one of claims 1 to 4, characterized in that step B) of carboxylation is carried out using carbon dioxide at a temperature equal to or greater than 200ºC, under a pressure of 4 × 10 ⁵ Pa (4 bar).

 6. Additive according to any one of the preceding claims, characterized in that the alkaline earth base is calcium oxide or magnesium oxide.

 7. Additive according to any one of the preceding claims, characterized in that step C) of sulfurization and over-alkalization is carried out by cooling the mixture of alkylphenate and alkylsalicylate obtained in step B) of carboxylation to a temperature of 155ºC, adding elemental sulfur at this temperature then gradually for a period of one to two hours a mixture of alkaline earth base, alkylene glycol and a monoalcohol with a boiling point above 150ºC, and maintaining the temperature between 150 and 160ºC.

8. Additive according to any one of the preceding claims, characterized in that the carboxylic acid containing 1 to 4 carbon atoms used in step A) of neutralization is a mixture of formic acid and acetic acid, preferably a 50/50 mixture by weight of these two acids.

 9. Lubricating composition containing a major part of lubricating oil and from 2 to 20% by weight of a detergent-dispersant additive which is the subject of any one of the preceding claims.

 10. Process for the preparation of detergent-dispersant additives for lubricating oil of the alkylsalicylates-alkylphenates, alkaline-earth, sulphurized and super-alkalized type, characterized in that it comprises the following stages:

 A) neutralization of alkylphenols containing at least 35% and at most 85% by weight of linear alkylphenol in which the linear alkyl radical contains 12 to 40 and preferably 18 to 30 carbon atoms, mixed with at most 65 and at minimum 15% by weight of branched alkylphenol in which the branched alkyl radical contains 9 to 24 and preferably 12 carbon atoms, using an alkaline earth base in the presence of at least one acid chosen from acids carboxylic containing from 1 to 4 carbon atoms, said neutralization operation being carried out at a temperature of at least 215ºC, with progressive placing in vacuum of the reactor in which the neutralization reaction is carried out in order to remove water from the reaction, in the absence of any solvent capable of forming an azeotrope with the latter. The amounts of reagents used correspond to the following molar ratios:

 - total alkaline earth / alkylphenol base between 0.2 to 0.7 and preferably between 0.3 and 0.5;

 total carboxylic acid / total alkylphenol between 0.01 and 0.5 and preferably between 0.03 and 0.15.

B) carboxylation of the alkylphenate obtained in step A) to convert at least 22% and preferably at least 25% into moles of the starting alkylphenols into alkylsali cylate (measured as salicylic acid) using carbon dioxide at a temperature of 180 to 240 ° C, preferably between 190 and 220 ° C, under a pressure which can range from atmospheric pressure to 15 × 10 ⁵ Pa (15 bars) for a period of one to eight hours, optionally in the presence of a 100N dilution oil added at the start or at the end of step A) or of step B;

 C) sulfurization and over-alkalinization of the mixture of alkylphenate and alkylsalicylate obtained by elemental sulfur in the presence of an alkaline earth base, of a mono-alcohol having a boiling point higher than 150ºC and preferably higher than 175 ° C and optionally at this stage an alkylene glycol or an alkylene glycol alkyl ether, at a temperature between 145 and 180 ° C, preferably between 150 and 160 ° C. The amounts of reagents used correspond to the following molar ratios:

 - sulfur / total alkylphenol between 0.3 to 1.5 and preferably between 0.8 and 1.0;

 - total alkaline earth base / total alkylphenol between 1.0 to 3.5 and preferably between 1.4 and

3.0;

- total alkaline earth base / mono-alcohol with a boiling point higher than 150ºC between 0.3 and 0.5 then after addition of the alkylene glycol or its alkyl ether if it has not already been added in a total alkaline earth / alkylene glycol base molar ratio of between 1.0 and 3.0 and preferably between 1.4 and 1.8, carbonation of the medium obtained by carbon dioxide at a temperature of 145 to 180 ° C and under pressure close to atmospheric pressure, the amount of C0 ₂ used being between that which can be completely absorbed by the reaction medium and an excess of 30% of this amount;

 D) elimination of the alkylene glycol and of the monoalcohol by distillation;

 E) filtration to remove sediment;

F) and finally degassing with air at a temperature between 80 and 160 ° C, preferably between 110 and 140 ° C, until the rating of the copper strip is 1A under test according to standard ASTM D 130 carried out for at least 15 minutes at 150ºC and preferably 1 hour at 150ºC.

 11. A hydraulic oil composition containing a hydraulic oil and from 0.1 to 3% by weight of a detergent-dispersant additive which is the subject of any one of claims 1 to 8.

 12. Detergent-dispersant additive for lubricating oil of the alkaline-earth, sulfurized and over-alkalized alkylsalycilate-alkylphenate type, characterized in that a) the alkyl substituents of said alkylsalicylate-alkylphenate are in a proportion of at least 35% and at most 85% by weight d linear alkyl in which the number of carbon atoms is between 12 and 40, preferably between 18 and 30 carbon atoms, with at most 65% by weight of branched alkyl in which the number of carbon atoms is between 9 and 24 and preferably 12 carbon atoms,

 b) in that the proportion of the alkylsalicylate in the alkylsalicylate-alkylphenate mixture is at least 22% and preferably at least 25% by moles and

 c) in that the molar proportion of alkaline earth base relative to the alkyl salicylate-alkylphenate group is between 1.0 and 3.5.

 13. Additive according to claim 12 characterized in that the molar proportion of sulfur present in one alkaline earth alkylsalicylate-alkylphenate, sulfurized and superalkalized is between 0.25 and 0.75 and preferably between 0.4 and 0.5.