EP0383359A2 - Process for preparing an overbased additive containing a boron derivative, additive produced by said process and lubricating compositions containing said additive - Google Patents

Abstract

Process for preparing a superalkalfied additive containing inorganic boron by carbonation of a reaction mixture consisting of a detergent, an alkali metal or alkaline-earth metal and nitrogen- containing and oxygen-containing promoters in a diluent oil and a hydrocarbon solvent. The inorganic boron derivative is introduced into the reaction mixture before the carbonation reaction. The boron additive is employed as an additive with an antiwear effect in lubricants.

Description

This invention relates to a process for preparing an over-alkalized 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 dispersing 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 the cold parts by its dispersing effect. The fixing of these particles in the form of varnish or lacquers is thus avoided.

The role of basic reserve additives consists in combating the acidity caused in 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 patents 3,907,691 and 4,10081) while organic compounds provide antiwear and antifriction properties rather (American patents 4,549,775 and 4,599,183).

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 the American patents 3 853774 and 4 601837. However for reasons related to the difference in reactivity between carbon dioxide and boric acid or anhydride, reported in American patent 3 785976, this substitution occurs. proves difficult.

The prior art is oriented towards 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 Patents 3,480,548, 4,089,790, 3,829,381 and 4,560,489 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 Patent 3,929,650 claims the possibility of using a dispersant of the alkenyl succinimide type.

US Patent 3,907,691 provides for the formation of a complex by heating the intermediate product formed by the reaction of boric acid with the overbased sulfonate. US Patent 4,539,126 claims the preparation of complexes by reacting boric acid with an overbased alkylsalicylate.

US Patent 3,928,216 reports the use of catalytic amounts of boron salts of an amine during the overbasing reaction.

US Patent 3,679,584 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 the alkaline earth carbonates which form colloidal dispersions, the 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 the form of a dispersion in oil is added to the reaction mixture before the introduction of carbon dioxide.

Among the inorganic boron derivatives, there may be mentioned the oxides and anhydrides of boron as well as boric steel and its salts. Boric acid and its ammonium salt, diammonium tetraborate ((NH₄) ₂ B₄O₇.4H₂O) its sodium salt, sodium tetraborate (Na₂B₄O₇.nH₂O) its potassium salt, potassium tetraborate (K₂B₄O₇. nH₂O) and its lithium salt, lithium tetraborate (Li₂B₄O₇.5H₂O) 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, salicyclic acids or phenols

ou R₄ est un radical 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 advantageously be used in admixture with alkyl succinamides of general formula:

or R₄ is a hydrocarbon radical 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 alphaolefins, 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 comprising 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.

The 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 naphtenic 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.

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.

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.

It may be advantageous to bring the reaction mixture containing the boron derivative to reflux for a period of 30 minutes to 2 hours before carbonation.

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 commonly used mechanical tests, 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-alkylbenzenesulfonic acid containing 70% active ingredient, 35g of 97% calcium hydroxide are introduced into a 250ml reactor equipped with an agitator, a carbon dioxide inlet and a condenser. 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. The 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:

500 ml of an aqueous solution at 80 ° C containing 50 g / l of tetraborate are introduced into a one liter reactor thermostatically controlled at 60 ° C containing 114 g of 200 Neutral oil with 12.8% dispersant dispersed therein sodium. The aqueous solution is added dropwise over 3 hours.
The homogeneous emulsion thus obtained is dehydrated as quickly as possible. A fluid dispersion of sodium tetraborate at 17% by weight in oil is thus obtained.

EXAMPLE 3: (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 2. A product of VA 350 is obtained, containing 0.36% by weight of boron, with cloudy appearance.
Examination of the product under an electron microscope shows the presence of 6nm diameter calcium carbonate globules and 0.6µm diameter sodium borate particles.

EXAMPLE 4

The experiment described in Example 1 is repeated, with the difference that only 4g of 200N diluent oil is introduced instead of 22.5g. 20.5 g of the sodium tetraborate dispersion of Example 2 are added before the start of carbonation. A product with a clear appearance is then collected, with VA 369 mg KOH / g at 0.46% by weight of boron.

Examination under the electron microscope reveals the presence of globules of only 6nm in diameter. The analysis of the globules in energy losses gives a spectrum where we notice a peak characteristic of the presence of boron. The procedure of Example 4 according to the invention makes it possible to effectively incorporate boron into the globules of the colloidal dispersion.

Claims (12)

1 - Process for the preparation of an overbased additive with antiwear effect by carbonation of a reaction mixture composed of at least one detergent, of an derivative of an alkali or alkaline earth metal, of at least one nitrogenous promoter and / or oxygenated in a diluent oil and a hydrocarbon solvent characterized in that an inorganic boron derivative used in the form of a dispersion in oil is added to the reaction mixture before the introduction of carbon dioxide. 2 - Process according to claim 1 characterized in that the reaction mixture contains at least one detergent chosen from sulfonic acids of petroleum or synthetic origin, salicylic acids, phenols and their alkali or alkaline-earth salts. 3 - Process according to claims 1 or 2 characterized in that the detergent is used in mixture with an alkylsuccinamide of general formula

or R₄ is a C₁₂ to C₁₀₀ hydrocarbon radical, n is between 1 and 6 and m is between 1 to 5. 4 - Method according to one of the preceding claims characterized in that the reaction mixture contains a derivative of an alkali or alkaline earth metal chosen from the oxides, hydroxides or alcoholate of such a metal. 5 - Process according to one of the preceding claims, characterized in that the reaction mixture contains at least one oxygenated promoter chosen from Cip to C₅ aliphatic alcohols, glycols or ethers. 6 - Method according to one of the preceding claims characterized in that the reaction mixture contains water. 7 - Method according to one of the preceding claims characterized in that the reaction mixture contains a paraffinic or naphthenic diluent oil. 8 - Method according to one of the preceding claims characterized in that the reaction mixture contains an aliphatic or aromatic hydrocarbon solvent. 9 - Method according to one of the preceding claims characterized in that in the reaction mixture containing 100 to 500 parts by weight of at least one detergent, 100 to 300 parts by weight of an derivative of an alkali or alkaline earth metal, 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 and 15 to 400 parts by weight of an inorganic derivative of boron or introduced at a temperature of 20 to 80 ° C and preferably from 35 to 70 ° C for 20 minutes to 4 hours, 50 to 350 parts by weight of carbon dioxide. 10 - Method according to one of the preceding claims characterized in that the reaction mixture is heated to reflux for 30 minutes to 2 hours before carbonation. 11 - Overbased additive with antiwear effect characterized in that it is prepared according to the process described in claims 1 to 10 and in that it contains 0.1 to 10% by weight and preferably 0.25 to 5% by weight d 'an inorganic boron derivative. 12 - Lubricating composition characterized in that it contains a natural or synthetic diluent oil and 0.5 to 40% by weight, preferably 1 to 30% by weight of an additive according to claim 11.