EP0308445B1 - Process for the preparation of a superalkalinized additive containing an inorganic boron derivative, additive produced by said process and lubricating compositions containing said additive - Google Patents

Abstract

Process for the preparation of a superalkanized additive with an anti-wear effect for lubricating oils, said process consisting of the carbonation of a reactive mixture composed of at least one detergent, of a derivate of an alkaline or alkaline-earth metal, at least one azotized and/or oxygenized promoter and a boron derivate, in a diluent oil and a hydrocarbon solvent.

Description

This invention relates to a process for preparing an overbased additive for lubricating oils containing an inorganic boron derivative, the additive thus obtained and a lubricating composition containing said additive.

Fuels, in particular those used in fuel or heavy fuel engines, contain increasing amounts of sulfur. At the same time, the operating conditions become more severe.

It has become necessary to add to the lubricating oils various additives improving their properties. Among these additives are detergents, dispersants, antiwear and extreme pressure additives and additives providing a basic reserve.

The detergent and dispersant properties of a lubricant correspond to its ability to keep impurities and unburned particles in suspension in the hot parts of the engine by its detergency effect but also in cold parts by its dispersing effect. The fixing of these particles in the form of varnish or lacquers is thus avoided.

The role of additives with a basicity reserve consists in combating the acidity caused in the engines by the combustion of organic sulfur derivatives contained in fuels and by the oxidation of the components of lubricating oils.

The antiwear additives act by forming a thin solid or plastic film which separates the friction surfaces and prevents wear of the different parts of the engine.

The detergent and dispersant properties as well as the basicity reserve are generally provided by overbased additives. These are alkali or alkaline earth carbonates in a detergent solution of the alkyl sulfonate, phenate or salicylate type.

Antiwear additives are generally sulfur and / or phosphorus compounds, the most commonly used being Zn dialkyldithiophosphates.

Boron derivatives form another class of antiwear additives. The boron mineral compounds provide an antiwear and extreme pressure function (US-A-3907691 and 4100081) while the organic compounds provide antiwear and anti-friction properties (US-A-4549975 and 4599183).

The incorporation of a boron compound in an overbased additive would make it possible to have a multifunctional additive having a basicity reserve, detergent, dispersant and anti-wear properties. Different methods of incorporating boron into an overbased additive have been considered.

The most obvious method would be to replace carbon dioxide with boric acid outright. This process is envisaged in US-A-3853774 and 4601837. However for reasons related to the difference in reactivity between carbon dioxide and boric acid or anhydride, reported in US-A-3785976, this substitution appears difficult.

The prior art has focused on boron compounds such as boric acid and its organic esters or else boron oxide which are then added to conventional over-alkalinized additives containing calcium carbonate. Such mixtures described in US-A-3480548, 4089790, 3829381 and 4560489 have drawbacks from the point of view of their stability and their compatibility with the other additives of the lubricant formulation.

In order to improve their stability, US-A-3929650 claims the possibility of using a dispersant of the alkenyl succinimide type.

US-A-3907691 provides for the formation of a complex by heating the intermediate product formed by reaction of boric acid with the overbased surfonate. US-A-4539126 claims the preparation of complexes by reaction of boric acid with an overbased alkylsalicylate.

US-A-3928216 reports the use of catalytic amounts of boron salts of an amine during the overbasing reaction.

US-A-3679584 suggests a two-step procedure. To a conventional overbased additive prepared in a first step, boric acid and carbon dioxide are added in a second step. However, the alkaline value of the over-alkalized mixture drops very sharply during this second stage, passing for example from 295 to 177.

The alkaline value (VA) is fictitiously equivalent to the number of milligrams of KOH per gram of overbased additive titrated by a strong acid. It is determined by direct potentiometric assay according to standard ASTM D-2896.

All the processes based on the mixture of a boron derivative with an additive already overbased give unstable products whose boron content and alkaline value are also low.

These mixtures are generally in the form of a cloudy liquid. Unlike alkaline earth carbonates which form colloidal dispersions, boron derivatives remain in the form of coarse solid particles responsible for the cloudy appearance of the liquid. These solid particles in suspension could go against the desired effect with antiwear additives by causing for example the abrasion of the motors. By precipitating they lead to annoying sediments and to a heterogeneity in the metal concentration.

The present invention overcomes these drawbacks and prepares overbased additives with significant boron content and high alkaline value. As the boron derivatives are incorporated into the globules of the colloidal dispersion, these additives are homogeneous and stable and have very good antiwear properties.

The process for the preparation of overbased additives with antiwear effect according to the invention consists in carbonating a reaction mixture composed of at least one detergent, of an alkali or alkaline earth metal derivative, of at least one nitrogenous and / or oxygenated promoter in a diluent oil and a hydrocarbon solvent characterized in that an inorganic boron derivative used in powder form or in aqueous solution is introduced into the reaction mixture during the carbonation reaction before the fifteenth minute of said carbonation.

Among the inorganic boron derivatives there may be mentioned the oxides and anhydrides of boron as well as boric acid and its salts. Boric acid and its ammonium salt, diammonium tetraborate ((NH₄) ₂B₄O₇ · 4H₂O) its sodium salt, sodium tetraborate (Na₂B₄O₇ · nH₂O) its potassium salt, potassium tetraborate (K₂B₄O₇ · nH₂O ) and its lithium salt, lithium tetraborate (Li₂ B₄ O₇ · 5H₂O) are particularly suitable.

We can also mention barium metaborate (BaO · B₂O₃ · nH₂O), manganese borate (MnB₄O₇) and lead borate (Pb (BO₂) ₂).

The detergents commonly used in overbased additives are salts of sulfonic acids, salicylic acids or phenols.

hydrocarboné de 12 à 100 atomes de carbone, n est compris entre 1 et 6 et m est compris entre 1 à 5.These detergents can be advantageously used in admixture with alkyl succinimides of general formula:

hydrocarbon of 12 to 100 carbon atoms, n is between 1 and 6 and m is between 1 to 5.

The sulfonic acids are of petroleum or synthetic origin. The average molecular weight of petroleum sulfonates is generally greater than 320. They are obtained by sulfonation of petroleum distillates. Synthetic sulfonic acids are particularly useful in the context of the invention. They may be products obtained by sulfonation of olefins with a carbon number greater than or equal to 12 or alternatively alkylarylsulfonic acids.

Alkylarylsulfonic acids have one or more alkyl chains on an aromatic ring, generally a benzenic ring. The alkyl chains must contain a minimum of 8 carbon atoms. Their structure is linear or branched. Benzene, toluene, xylene or napthalene alkylated with C₁₃ to C₁₆ alpha-olefins, with C₂₀₋₂₂ paraffins or with propylene tetramers (C₂₄-benzenesulfonic acid) are commonly used.

The oil-soluble salicylic acids are substituted on the aromatic ring by a chain containing at least 10 and in general 16 to 18 carbon atoms.

The phenols which are soluble in organic medium and which are particularly advantageous in the context of the invention are phenols substituted by one or more linear or branched alkyl chains containing at least 8 carbon atoms. The most common commercial products are, for example, nonylphenol, dinonylphenol, dodecylphenol and mixtures thereof.

Phenols are used in the form of alkali or alkaline earth metal salts. They are particularly appreciated after having undergone a sulfurization by reaction with the flower of sulfur or with sulfur chloride.

Overbased additives contain one or more of these detergents. The sulfonic or salicylic acids or the phenols can be used in admixture with dispersants derived from alkenylsuccinic acids with a chain greater than or equal to 12 carbon atoms or with carboxylic acids having at least 8 carbon atoms.

The alkali or alkaline earth metal derivative is generally an oxide, hydroxide or alcoholate of such a metal.

The oxygenated promoters are mainly aliphatic alcohols, generally C₁ to C₅, most often methanol, ethanol, butanol or glycols. Ethers such as dioxolane or dialkoxymethanes are also used. The alcohols can be used alone or in admixture with water.

The nitrogenous promoters are inter alia ammonia, ethylenediamine, ethanolamines, ammonium chloride or ammonium carbonate.

The role of the diluent oil is to allow easy handling at room temperature. Among these oils, mention may be made of paraffinic oils such as 75, 100 or 150 Neutral or naphthenic oils, type 100 Pale solvent.

Hydrocarbon solvents have an aliphatic structure, such as heptane, isooctane, nonane or an aromatic structure, such as toluene or xylene. These solvents can be used as a mixture. It is particularly advantageous to use solvents which give azeotropes with water, such as alcohols, glycols or alkoxyalkanols.

For the implementation of the invention, a double jacket reactor is generally used, provided with a vigorous stirring system, a temperature regulator, a condenser, a system allowing a vacuum to be produced. or a slight overpressure, a gas diffuser and a solvent recovery system.

• ― 100 à 500 parties en poids de détergents
• ― 100 à 300 parties en poids d'un dérivé de métal alcalin ou alcalinoterreux
• ― 0 à 100 parties poids d'un promoteur azoté
• ― 30 à 300 parties poids d'un promoteur oxygéné
• ― 0 à 100 parties poids d'eau
• ― 100 à 500 parties poids d'une huile diluante
• ― 200 à 800 parties poids d'un solvant hydrocarboné
• ― 15 à 400 parties en poids d'un dérivé inorganique du bore.

According to a preferred implementation of the invention, the following are introduced into the reactor:

• - 100 to 500 parts by weight of detergents
• - 100 to 300 parts by weight of an alkali or alkaline earth metal derivative
• - 0 to 100 parts by weight of a nitrogenous promoter
• - 30 to 300 parts by weight of an oxygenated promoter
• - 0 to 100 parts by weight of water
• - 100 to 500 parts by weight of a diluent oil
• - 200 to 800 parts by weight of a hydrocarbon solvent
• - 15 to 400 parts by weight of an inorganic boron derivative.

If the boron derivatives are used in the form of a dispersion in oil, this dispersion is added to the reaction mixture before the introduction of carbon dioxide. The boron derivatives used in dispersion are boric acid and its salts. The boron derivatives used in powder form or in the form of an aqueous solution, if their solubility is sufficient, are boron oxide, boric acid and its salts.

The pulverulent compounds or the aqueous solutions are introduced during carbonation a few minutes after the start of the reaction.

Using detergents of the sulfonate type, the reaction mixture is subjected to strong stirring while the introduction of 50 to 350 parts by weight of carbon dioxide begins by bubbling into the reaction medium. The duration of carbonation generally varies from 20 minutes to 4 hours at constant flow. The reaction is exothermic. The mixture is maintained at a temperature varying from 20 to 80 ° C and preferably from 35 to 70 ° C.

Solvents can be removed in one step, but generally there are two steps. The solvents, except the hydrocarbon diluent, are removed by heating, then the solid residues by centrifugation or filtration before the removal of the hydrocarbon solvent.

The overbased additives obtained by the process according to the invention have alkaline values (VA), measured according to standard ASTM D-2896, generally greater than 200 mg KOH / g. VAs greater than 300 and even 500 can be obtained.

In the case of the use of detergents of the phenolic type, the reaction mixture free of boron derivative is brought to reflux for at least half an hour. After cooling, the boron derivative is added. The introduction of carbon dioxide and the subsequent treatment proceed as before.

The overbased phenates obtained have alkaline values (VA) generally greater than 150 mg KOH / g. VAs greater than 250 even 320 can be obtained.

The amount of boron incorporated can vary between 0.1 and 10% by weight and preferably 0.25 to 5%. This amount is sufficient to provide antiwear properties to lubricating oils. The antiwear properties are measured with mechanical tests commonly used, such as the 4 wear balls method (NF-E 48-617) and 4 extreme pressure balls (ASTM D 2783-69T or NF E 48-617) and the FALEX tests ( ASTM D 32-33).

The additives according to the invention have a clear appearance and keep a homogeneous consistency over time. They have viscosities low enough to allow easy handling and are compatible with the other additives commonly used in lubricating oils.

The overbased additives are added to lubricating oils of natural or synthetic origin at a concentration of between 0.5 and 40% by weight and preferably between 1 and 30% by weight.

The following examples illustrate the invention without, however, limiting it.

EXAMPLE 1 : (Comparative)

27g of C₂₄-alylbenzenesulfonic acid containing 70% active material, 35g of calcium hydroxide are introduced into a 250 ml reactor, equipped with an agitator, a carbon dioxide inlet and a condenser. 97% purity, 13.3 ml of methanol, 22.5 g of 100 N oil, 1.1 ml of 20% ammonia, 150 ml of xylene.

The mixture is stirred at 700 revolutions / minute and its temperature is regulated at 49 ° C. Carbon dioxide is introduced at a flow rate of 230 ml / minute for 30 minutes. At the end of the reaction, the mixture is heated to 100 ° C to remove the methanol and the water produced by carbonation. Solid residues are removed by centrifugation then filtration. The elimination of xylene makes it possible to recover a fluid product of basicity (VA) equal to 420 mg KOH / g containing 18% of calcium and which proves to be stable in dilution in mineral oils (absence of cloudiness after 1 month).

EXAMPLE 2 :

The procedure of Example 1 is repeated except that 5 g of sodium metaborate tetrahydrate are added to the reaction medium before the 10th minute of carbonation. A much more fluid product than VA 425 is collected, stable in oil and whose boron content is of the order of 0.37% by weight.

EXAMPLE 3 :

The experiment described in Example 1 is repeated with the difference that 2 g of powdered sodium tetraborate are added to the reaction medium before the 10th minute of carbonation. A product of VA 403 mg KOH / g is collected, the boron content of which is 0.45% by weight.

EXAMPLE 4 : (Comparative)

A simple mixture of 13 g of overbased sulfonate from Example 1 is prepared with 3 g of the dispersion of sodium tetraborate from Example 3. A product of VA 350 is obtained, containing 0.36% by weight of boron, at cloudy appearance.

Examination of the product under an electron microscope shows the presence of calcium carbonate globules of 0.006 µm in diameter and sodium borate particles of 0.6 µm in diameter.

EXAMPLE 5 :

The procedure of Example 3 is repeated with the difference that 30 grams of calcium oxide, 10.2 ml of water are introduced and the product is carbonated for 75 minutes at a flow rate of 103 ml / minute . Before the 15th minute of carbonation, 9.52 g of potassium tetraborate powder are added. A clear product of VA 310 mg KOH / g and containing 0.86% by weight of boron is collected.

EXAMPLE 6

The procedure of Example 5 is repeated, but the boron compound is boric acid. 8.98 g of powdered boric acid are added at the 10th minute of carbonation. A product of VA 411 mg KOH / g and of very viscous consistency is then obtained. It contains 1.23% by weight of boron.

EXAMPLE 7 :

The procedure of Example 5 is repeated after adding only 4.5 ml of methanol to the reaction medium. A clear, very fluid product of VA 298 mg KOH / g is obtained, containing 1.3% by weight of boron.

EXAMPLE 8 :

The procedure of Example 6 is repeated, but 11.2 g of powdered boron trioxide are added.

A clear product of VA 229 mg KOH / g and containing 2.4% by weight of boron is collected.

EXAMPLE 9 :

The procedure of Example 5 is repeated, but 12.3 g of trimethylborate are added at the 10th minute of carbonation. A viscous product of VA 437 mg KOH / g and at 1.2% by weight of boron is then obtained.

EXAMPLE 10 :

The procedure of Example 1 is repeated except that 9.53 g of powdered diammonium tetraborate are added after 10 minutes of carbonation. A clear, relatively fluid product of VA 438 mg KOH / g and containing 1.15% by weight of boron is obtained.

EXAMPLE 11 :

The procedure of Example 1 is repeated except that, instead of C d'un-benzene sulfonic acid, 23 g of an 80/20 molar mixture of C₂₄-benzene sulfonic acid of molar weight are used. 520 to 70% of active material and C₉ carboxylic acid obtained by hydroformylation of olefins (CK9 acid distributed by the company NORSOLOR). 30.7 g of slaked lime at 97% purity are added.

Carbonation is carried out for 25 minutes at a flow rate of 210 ml / minute.

9.53 g of diammonium tetraborate tetrahydrate are added after ten minutes of carbonation.

The product collected is clear and stable in dilution. Its VA is 307 mg KOH / g and its boron content is 1.55% by weight.

EXAMPLE 12 :

4 billes usures:

NF-E 48-617

usure FALEX:

D 32-33

4 billes EP:

D 2783-69T E 48-617

The overbased additives were subjected to the following mechanical tests:

4 wear balls:

NF-E 48-617

FALEX wear:

D 32-33

4 EP balls:

D 2783-69T E 48-617

The products are tested after dilution in the following oil mixture: 600N / BSS (Bright Stock Solvent) = 80/20 up to a VA of 70 mg KOH / g or even 10 mg KOH / g.

By way of example, the following table presents some results obtained, it can thus be seen that the products obtained according to the invention have improved antiwear and extreme pressure power compared to the reference overbased product described in Example 1.

Claims (11)

1. Process for the preparation of an overbased antiwear additive by carbonation of a reaction mixture comprising at least one detergent, an alkali or alkaline earth metal derivative, at least one nitrogen and/or oxygen-containing promoter in a diluting oil and a hydrocarbon solvent characterised in that an inorganic boron derivative, used in powdered form or in an aqueous solution, is introduced into the reaction mixture during the carbonation reaction before the fifteenth minute of the said carbonation reaction.

2. Process according to claim 1, characterised in that the reaction mixture comprises at least one detergent selected from sulphonic acids of a petroleum or synthetic origin, salicylic acids, phenols and their alkali or alkaline earth salts.

3. Process according to claims 1 or 2, characterised in that the detergent is used in a mixture with an alkylsuccinimide of the general formula

where R₄ is a C₁₂ to C₁₀₀ hydrocarbon radical, n is between 1 and 6 and m is between 1 and 5.

4. Process according to any one of the preceding claims, characterised in that the reaction mixture comprises an alkali or alkaline earth metal derivative selected from oxides, hydroxides or an alcoholate of such a metal.

5. Process according to any one of the preceding claims, characterised in that the reaction mixture contains at least one oxygen-containing promoter selected from among C₁ to C₅ aliphatic alcohols, glycols or ethers.

6. Process according to any one of the preceding claims, characterised in that the reaction mixture comprises water.

7. Process according to any one of the preceding claims characterised in that the reaction mixture comprises a paraffinic or naphthenic diluting oil.

8. Process according to any one of the preceding claims, characterised in that the reaction mixture comprises an aromatic or aliphatic hydrocarbon sulphate.

9. Process according to any one of the preceding claims characterised in that 50 to 350 parts by weight of carbon dioxide are added to the reaction mixture comprising 100 to 500 parts by weight of at least one detergent, 100 to 300 parts by weight of an alkali or alkaline earth metal derivative, 0 to 100 parts by weight of a nitrogen-containing promoter, 30 to 300 parts by weight of an oxygen-containing promoter, 0 to 100 parts by weight of water, 100 to 500 parts by weight of a diluting oil, 200 to 800 parts by weight of a hydrocarbon solvent and 15 to 400 parts by weight of an inorganic boron derivative at a temperature of 20 to 80°C and preferably 35 to 70°C during a period of 20 minutes to 4 hours.

10. Overbased antiwear additive characterised in that it is prepared according to the process described in claims 1 to 9 and in that it contains 0.1 to 10% by weight, and preferably 0.25% to 5% by weight, of an inorganic boron derivative.

11. Lubricating composition characterised in that it contains a natural or synthetic diluting oil and 0.5 to 40% by weight, and preferably 1 to 30% by weight, of an additive according to Claim 10.