EP0604474B1

EP0604474B1 - Overbased metal-containing detergents

Info

Publication number: EP0604474B1
Application number: EP92918587A
Authority: EP
Inventors: John Frederick Marsh; Neal Allan Hawkins; John Arthur Cleverley; William David Read
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1991-09-19
Filing date: 1992-09-05
Publication date: 1996-07-17
Anticipated expiration: 2012-09-05
Also published as: CA2119245A1; DE69212322D1; DE69212322T2; JPH06511022A; WO1993006195A1; GB9120038D0; EP0604474A1

Abstract

Ultrasound is used in the preparation of overbased metal-containing detergents, for example, overbased sulphonates or phenates of calcium or magnesium, suitable for use as additives for oil-based compositions, for example, lubricating oils and fuels. The use of ultrasound may, for example, reduce sediment levels, reduce the amount of waste material to be disposed of, reduce the amount of product lost during filtration, and/or increase filtration rates.

Description

Overbased metal-containing detergents

The invention relates to a process for preparing overbased metal-containing detergents, to overbased detergents produced by the process, and to oil-based compositions containing the detergents.
Overbased metal-containing detergents are well known, as is their use as additives in oil-based compositions, for example, lubricants, greases and fuels. The overbased detergents function both as detergents and acid neutralizers, thereby reducing wear and corrosion and, when used in engines, extending engine life. Commonly used overbased metal-containing detergents include overbased oil-soluble sulphonates, phenates, sulphurized phenates, thiophosphonates, salicylates, naphthenates and other carboxylates of the alkali and alkaline earth metals and magnesium, particularly preferred metals being calcium and magnesium.
Many processes have been proposed for producing overbased metal-containing detergents suitable for use as additives in oil-based compositions, the preferred processes generally involving the treatment with an acidic gas of a mixture, in an organic solvent or diluent, of an oil-soluble metal salt and/or an oil-soluble acid and an excess of a compound, normally a basic compound, of the desired metal above that required to react with any acid present. Thus, when starting from an oil-soluble acid rather than from a salt, the preferred processes involve a neutralization step followed by an overbasing step. The last-mentioned step is often referred to as a carbonation step, since in practice carbon dioxide is almost invariably used as the acidic gas.
It is normally desirable that overbased metal-containing detergents to be used as additives for oil-based compositions have a relatively high basicity since this results in the most economic use of the metal. The basicity is usually expressed in terms of the Total Base Number (TBN) of the product, the TBN being the number of milligrams of potassium hydroxide equivalent to 1 gram of the product when titrating with a strong acid. The invention is particularly concerned with detergents having a TBN of 50 mg KOH/g or more and, for some applications, it is preferred that the TBN be at least 300, preferably at least 400, mg KOH/g, as measured by ASTM D2896.
Despite the numerous prior proposals for preparing overbased metal-containing detergents suitable for use as additives in oil-based compositions, for example, lubricants, greases and fuels, there remains a need for improved processes for preparing such additives, particularly additives having a TBN of 50 mg KOH/g or more.
The applicants have surprisingly found that the use of ultrasound to treat a starting material, a reaction mixture or a reaction product in a process for the preparation of an overbased metal-containing detergent makes it possible to obtain improvements in the preparation of overbased metal-containing detergents, especially those of high TBN. The term "reaction mixture" as used herein includes both a mixture of starting materials and the mixture when in reaction.
The invention accordingly provides a process for the preparation of an overbased metal-containing detergent, in which process a starting material, a reaction mixture, or a reaction product is treated with ultrasound. The invention also provides overbased metal-containing detergents produced by the process, and oil-based compositions containing such detergents.
The invention further provides a process for the preparation of an overbased metal-containing detergent which process comprises treating with CO₂ a mixture comprising a metal-containing detergent selected from the group consisting of phenate sulphonate, sulphurized phenate and salicylate and a metal-containing basic compound selected from the group consisting of a metal oxide, metal hydroxide and metal alkoxide, in which process a starting material, a reaction mixture or a reaction product is treated with ultrasound;and a process for the preparation of an overbased metal-containing detergent which comprises reacting an oil-soluble acid with a metal-containing basic compound to give a metal-containing detergent, and treating with CO₂ a mixture of the metal-containing detergent and a metal-containing basic compound, in which process a starting material, reaction mixture or reaction product is treated with ultrasound. The metal-containing detergent may if desired contain more than one metal, so in principle a mixture of basic compounds could be used in the neutralizing step and/or the overbasing step, and/or different basic compounds could be used in these two steps.
The invention has particular relevance to processes for the preparation of overbased metal-containing detergents in which purification of the product involves a filtration step, although in some cases an improvement is obtained when purification is effected by an alternative method, for example, centrifuging.
Examples of improvements which may be obtained by the use of ultrasound in accordance with the invention are a reduction in the amount of sediment to be removed at the end of the process, a reduction in the amount of waste material resulting from the process, a reduction in the amount of product lost during filtration, and an increase in the filtration rate. Not all of these improvements will necessarily be obtained in any particular case, although in some cases an improvement in one respect may lead to an improvement in one or more other respects. Thus, for example, a reduction in sediment levels will normally lead to lower amounts of waste and may also lead to a reduced tendency for the blocking of filters, and increased filtration rates.
Where there is a reduced tendency for filters to be blocked, filters can be cleaned less frequently, while faster filtration rates can lead to increased plant capacity. The waste to be disposed of at the end of a process in which purification is effected by filtration includes not only the sediment itself, but also filter-aid added before filtration. The amount of filter-aid used is normally in direct proportion to the amount of sediment, so that a reduction in the amount of sediment will normally also make possible a reduction in the amount of filter-aid used. A reduction in the amount of waste to be disposed of at the end of a process is an important advantage from the ecological viewpoint when working on a large scale.
While the use of ultrasound in processes for the preparation of metal-containing detergents will give an improvement in most cases, for example, one or more improvements as indicated above, there may be some cases where, for instance, a process gives low sediment levels and good filtration rates without the use of ultrasound. In such cases, the use of ultrasound during the process may not give any appreciable improvement.
The invention also provides the use of ultrasound in the preparation of an overbased metal-containing detergent.
The invention further provides the use of ultrasound to reduce sediment levels in the preparation of an overbased metal-containing detergent.
The invention also provides the use of ultrasound to reduce the proportion of waste material obtained in the preparation of an overbased metal-containing detergent.
The invention further provides the use of ultrasound to increase filtration rates in the preparation of an overbased metal-containing detergent.
The term "ultrasound" is usually used to denote sound having a frequency above that normally audible to the human ear. In accordance with the invention, the term "ultrasound" advantageously denotes sound having a frequency of about 16 to 100 kHz, preferably 16 to 80 kHz. The intensity of sound becomes attenuated with distance from the source, sound of higher frequencies becoming attenuated more rapidly than sound of lower frequencies, and in many cases, therefore, it may be desirable to use low frequency ultrasound, for example, ultrasound having a frequency in the range of 20 to 50 kHz. Commercially available power ultrasound equipment is in many cases tuned to operate at 20 kHz.
The sound intensity to be used in accordance with the invention will depend on the system to be treated and the optimum value for any particular system can be determined by routine experiment. In general ultrasonic sources to be used in accordance with the invention will produce sound with intensities in the region of from 0.5 to 500 watts/cm², especially 1 to 300 watts/cm². As indicated above, intensities become attenuated with distance from the source, and the intensity of the sound produced by the source must be chosen with this in mind.
The treatment with ultrasound can be carried out by any suitable means. A general discussion of some of the principles behind the generation of power ultrasound, and examples of a number of different sonicators, are given, for example, in T. J. Mason, Ed., "Sonochemistry: The Uses of Ultrasound in Chemistry", Royal Society of Chemistry, 1990, 47-68.
One means for carrying out the treatment with ultrasound comprises an ultrasonic bath, which typically has the form of a liquid-filled tank with a plurality of transducers positioned around the base and walls. An ultrasonic bath is a low intensity system, the intensity of the ultrasound at the transducer face typically being of the order of 1 to 2 watts/cm². If desired, an ultrasonic bath could be used in a continuous process in which, for example, a fluid to be treated is caused to flow in a controlled manner through an ultrasonic tank and out over a weir. A number of tanks could, if desired, be connected in series.
Another means for carrying out the treatment with ultrasound comprises an ultrasonic probe. Such probes are typically capable of supplying much higher sound intensities. Thus, for example, the intensity at the face of the probe may be of the order of 100 to 500 watts/cm². For continuous operation, one or more probes could, for example, be positioned in a flow pipe.
A further means for carrying out the treatment with ultrasound comprises apparatus in which the fluid to be treated is pumped at high velocity past a blade, causing the blade to vibrate ultrasonically.
In accordance with the invention, ultrasound may be used in the preparation of any overbased metal-containing detergent suitable for use as an additive in an oil-based composition, for example, the overbased oil-soluble sulphonates, phenates, sulphurized phenates, thiophosphonates, salicylates, and naphthenates and other carboxylates of a metal, particularly the alkali or alkaline earth metals or magnesium, for example, sodium, lithium, calcium, barium and magnesium. The most commonly used metals are calcium and magnesium, mixtures of calcium and magnesium, and mixtures of calcium and/or magnesium with sodium. The process of the invention finds particular use in the preparation of overbased calcium and magnesium alkaryl sulphonates and alkyl phenates, but is not limited thereto. The invention is particularly concerned with the preparation of metal-containing detergents having a TBN of at least 50 mg KOH/g. The preferred detergents comprise dispersed carbonate complexes, that is, the acidic gas used in their preparation is carbon dioxide.
Sulphonic acids suitable for use in preparing oil-soluble sulphonates are typically obtained by sulphonation of alkyl-substituted aromatic hydrocarbons, for example, those obtained from the fractionation of petroleum by distillation and/or extraction, or by the alkylation of aromatic hydrocarbons, for example, benzene, toluene, xylene, naphthalene, or biphenyl. Alkylation of aromatic hydrocarbons may be carried out, in the presence of a catalyst, with alkylating agents having from about 3 to more than 50 carbon atoms, such as, for example, haloparaffins, olefins that may be obtained by dehydrogenation of paraffins, and polyolefins, for example, polymers of ethylene, propylene, and/or butene. The alkaryl sulphonates usually contain from about 9 to about 70 or more carbon atoms, preferably from about 16 to about 50 carbon atoms, per alkyl-substituted aromatic moiety.
The metal compounds which may be used in neutralizing these alkaryl sulphonic acids to provide the sulphonates include the oxides, hydroxides and alkoxides, for example, calcium hydroxide or magnesium oxide. Hydrocarbon solvents and/or diluent oils may also be included, as well as promoters and viscosity control agents, for example, formates and halides.
The highly basic metal sulphonates are usually produced by neutralizing an alkaryl sulphonic acid with a large excess of metal base over that required for complete neutralization and thereafter forming a dispersed carbonate complex by reacting the excess metal base with carbon dioxide to provide the desired overbasing. Neutral or slightly basic metal sulphonates may be used in place of the alkaryl sulphonic acid.
The reaction mixture may include organic solvents, for example, toluene, xylene, hexane, chlorobenzene; other materials, for example, alcohols, water, amines, and/or salts of organic or inorganic acids, which serve to promote the overbasing process; and diluent oil. Volatile materials and undispersed solids are removed in the final stages of the process. Processes which use a metal alkoxide as the starting metal compound can proceed by a somewhat different route in which carbonation of the alkoxide to give an alkoxide-carbonate complex is followed by hydrolysis of the complex to give the metal carbonate. These reactions may be carried out in the presence of alkaryl sulphonate, solvents and diluents.
Highly basic metal sulphonates may have a TBN from about 50 to about 500, preferably 250 to 450, and contain about 10 to about 35 wt. % alkaryl sulphonate. The following patents provide illustrative examples of overbased sulphonates and/or processes for preparing them:

EP 0 000 264, EP 0 000 318, EP 0 025 328,
EP 0 047 126, EP 0 121 024, EP 0 015 341,
EP 0 013 807, EP 0 013 808, EP 0 212 922

Examples of sulphurized alkyl phenols which may be used for preparing sulphurized phenate detergents are phenols of the general structure:
where R is an alkyl radical, n is an integer from 0 to 4 and x is an integer from 1 to 4. All the R groups will normally be the same, but this is not essential. The average number of carbon atoms in all of the R groups is preferably at least about 9 in order to ensure adequate solubility in oil. The individual R groups may contain from 5 to 40, preferably 8 to 20 carbon atoms. Alkylation of phenol may be carried out with, for example, alkylating agents of the types used to alkylate aromatic hydrocarbons in the manufacture of alkaryl sulphonates. Dihydroxybenzenes may be used in place of phenol. Sulphurization may be effected, for example, by reaction of the alkyl phenol with sulphur chloride or by reaction with sulphur. In the latter case, the alkyl phenol is usually present as the metal salt, although other sulphurization promoters may be used, for example, amines.
Highly basic metal phenates may be made by methods similar to those used to prepare highly basic metal sulphonates. Highly basic metal phenates may have a TBN from, for example, 100 to 400, preferably about 200 to 350. The following patents provide illustrative examples of overbased phenates and/or processes for preparing them:

EP 0 094 814, GB 1 470 338, GB 1 551 819,
GB 2 055 855, GB 2 055 886, GB 1 597 482.

Highly basic metal thiophosphonates, salicylates, naphthenates and other mono- and dicarboxylates may also be used in oil-based compositions and may be prepared by methods similar to those used to prepare highly basic sulphonates and phenates.
In a first aspect of the invention, a starting material or reaction mixture used in a process for the preparation of an overbased metal-containing detergent is subjected to treatment with ultrasound. In this case, ultrasound is advantageously used to treat a metal-containing basic compound, preferably an oxide or hydroxide, to be used in a neutralization step, and/or to treat the reaction mixture in the neutralization step (if used) and/or the overbasing step. Thus, ultrasound may be used to treat a reaction mixture comprising a metal-containing basic compound and an oil-soluble acid capable of reacting with the basic compound to form a metal-containing detergent, and/or to treat a reaction mixture comprising an oil-soluble metal-containing detergent and a metal-containing basic compound, the last-mentioned reaction mixture preferably being treated with ultrasound while an acidic gas, preferably carbon dioxide, is passed into it to give an overbased product.
As indicated above, treatment with ultrasound may be effected using an ultrasonic bath. In some cases, an ultrasonic bath may act as a heat sink, resulting in cooling of, for example, a reaction mixture and incomplete, or no, reaction. In such cases, the bath preferably comprises heating means so that the temperature of the liquid (normally water) in the bath can be maintained at a level at which the reaction is not inhibited, or at any other desired temperature.
The optimum sound frequencies, sound intensities and treatment times to be used in accordance with this aspect of the invention will depend on the nature of the starting material or reaction mixture to be treated, and can be determined by routine experiment. Examples of treatment times and methods are given in the Examples herein. Where ultrasound is used to treat a reaction mixture, the ultrasound treatment is preferably continued throughout the entire reaction period.
The applicants have found that the treatment of a starting material or reaction mixture in accordance with the first aspect of the invention can result, for example, in lower sediment levels in the product obtained at the end of the overbasing step and, in consequence, lower sediment levels in overbased products from which volatile materials have been stripped prior to filtration. As indicated earlier, lower sediment levels can lead to increased filtration rates and a reduced tendency for the blocking of filters, so that plant capacity can be increased and filters can be cleaned less frequently, and can also lead to lower amounts of product being lost on the filter, and lower amounts of waste.
In a second aspect of the invention, a reaction product is treated with ultrasound. The applicants have surprisingly found that it is particularly advantageous to treat with ultrasound the product of the overbasing reaction employed in the preparation of overbased metal-containing detergents. In particular, the applicants have found that filtration rates may be increased by treating an overbased product with ultrasound before filtration. In addition, less product may be lost on the filter cake during filtration and, in some cases, sediment levels may be reduced, leading, for example, to a reduction in the amount of waste material to be disposed of at the end of the process. In some cases, treatment of the reaction product with ultrasound may eliminate, or reduce, the amount of gelatinous material in the product.
Before filtration of the product of an overbasing reaction, the product is normally stripped to remove volatile materials required in the production of the overbased product but not required in the final product, and a solvent may be added, normally to the stripped product, before filtration. In accordance with the present invention, the ultrasound treatment may be carried out at any stage, for example, on the unstripped, partially stripped or fully stripped product, and before or after the addition of a solvent.
The optimum sound frequencies, sound intensities and treatment times to be used in accordance with this aspect of the invention will depend on the nature of the reaction product to be treated, and can be determined by routine experiment. Examples of treatment times and methods are given in the Examples herein.
Overbased detergents obtained by the process of the invention are useful as additives for oil-based compositions, for example, lubricants, greases and fuels, and the invention thus also provides such compositions containing the overbased detergents. When used in engine lubricants, the overbased detergents neutralize acids formed by the operation of the engine and help to disperse solids in the oil to reduce the formation of harmful deposits. They also enhance the antirust properties of the lubricants. The amount of overbased detergents that should be included in the oil-based composition depends on the type of composition and its proposed application. Automotive crankcase lubricating oils typically contain 0.01% to 3 mass % of the overbased detergent, on an active ingredient basis, based on the mass of the oil, while marine lubricating oils typically contain up to 13 mass % of the detergent, on the same basis.
The overbased detergents prepared in accordance with the invention are oil-soluble or (in common with certain of the other additives referred to below) are dissolvable in oil with the aid of a suitable solvent, or are stably dispersible materials. Oil-soluble, dissolvable, or stably dispersible as that terminology is used herein does not necessarily indicate that the materials are soluble, dissolvable, miscible, or capable of being suspended in oil in all proportions. It does mean, however, that the materials are, for instance, soluble or stably dispersible in oil to an extent sufficient to exert their intended effect in the environment in which the oil is employed. Moreover, the additional incorporation of other additives may also permit incorporation of higher levels of a particular additive, if desired.
Additives, including the overbased detergents prepared in accordance with the present invention, can be incorporated into a base oil in any convenient way. Thus, they can be added directly to the oil by dispersing or by dissolving them in the oil at the desired level of concentration. Such blending can occur at room temperature or an elevated temperature.
Additives produced in accordance with the present invention may be useful in fuel oils or lubricating oils. The normally liquid fuel oils are generally derived from petroleum sources, for example, normally liquid petroleum distillate fuels, although they may include those produced synthetically by the Fischer-Tropsch and related processes, the processing of organic waste material or the processing of coal, lignite or shale rock. Such fuel compositions have varying boiling ranges, viscosities, cloud and pour points, according to their end use, as is well known to those skilled in the art. Among such fuels are those commonly known as diesel fuels, distillate fuels, for example, gasoline, heating oils, residual fuels and bunker fuels, which are collectively referred to herein as fuel oils. The properties of such fuels are well known to those skilled in the art as illustrated, for example, by ASTM Specification D 396-73, available from the American Society for Testing Materials, 1916 Race Street, Philadelphia, Pennsylvania 19103.
Middle distillate fuel oils include distillates boiling from about 120 to 725°F (about 49 to 385°C) (e.g., 375 to 725°F (191 to 385°C)), including kerosene, diesel fuels, home heating fuel oil, jet fuels, etc., and most preferably whose 20 % and 90 % distillation points differ by less than 212°F (100°C), and/or whose 90 % to final boiling point range is between about 20 to 50°F (about -7 and 10°C) and/or whose final boiling point is in the range of 600 to 700°F (about 316 to 371°C).
Overbased detergents prepared in accordance with the invention are particularly useful in lubricating oil compositions which employ a base oil in which the detergents are dissolved or dispersed. Base oils with which the overbased detergents may be used include those suitable for use as crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, for example, automobile and truck engines, marine and railroad diesel engines. They may also be used, for example, in base oils suitable for use as aviation lubricants or as lubricants for two cycle engines.
Synthetic base oils include alkyl esters of dicarboxylic acids, polyglycols and alcohols; poly-α-olefins, including polybutenes; alkyl benzenes; organic esters of phosphoric acids; and polysilicone oils.
Natural base oils include mineral lubricating oils which may vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, mixed, or paraffinic-naphthenic, as well as to features used in their production, for example, as to the distillation range chosen, and as to whether they are, for example, straight run or cracked, hydrofined or solvent extracted.
More specifically, natural lubricating oil base stocks which can be used may be straight mineral lubricating oil or distillates derived from paraffinic, naphthenic, asphaltic, or mixed base crude oils. Alternatively, if desired, various blended oils may be employed as well as residual oils, particularly those from which asphaltic constituents have been removed. The oils may be refined by any suitable method, for example, using acid, alkali, and/or clay or other agents such, for example, as aluminium chloride, or they may be extracted oils produced, for example, by solvent extraction with solvents, for example, phenol, sulphur dioxide, furfural, dichlorodiethyl ether, nitrobenzene, or crotonaldehyde.
The lubricating oil base stock conveniently has a viscosity of about 2.5 to about 12 cSt (about 2.5 x 10^-6 to about 12 x 10^-6 m²/s) and preferably about 2.5 to about 9 cSt. (about 2.5 x 10^-6 to about 9 x 10^-6 m²/s) at 100°C. Mixtures of synthetic and natural base oils may be used if desired.
An overbased detergent prepared in accordance with the present invention may be employed in a lubricating oil composition which comprises lubricating oil, typically in a major proportion, and the detergent, typically in a minor proportion, for example, in a proportion as indicated above. Additional additives may be incorporated in the composition to enable it to meet particular requirements. Examples of additives which may be included in lubricating oil compositions are other detergents and metal rust inhibitors, viscosity index improvers, corrosion inhibitors, oxidation inhibitors, friction modifiers, dispersants, anti-foaming agents, anti-wear agents, pour point depressants, and rust inhibitors.
Additional detergents and metal rust inhibitors include other metal salts, preferably overbased metal salts, particularly calcium, magnesium and sodium salts, for example, oil-soluble overbased sulphonates, phenates, sulphurised phenates, thiophosphonates, salicylates, naphthenates, and other carboxylates, particularly carboxylates derived from mono- and di-carboxylic acids.
Viscosity index improvers (or viscosity modifiers) impart high and low temperature operability to a lubricating oil and permit it to remain shear stable at elevated temperatures and also exhibit acceptable viscosity or fluidity at low temperatures. Suitable compounds for use as viscosity modifiers are generally high molecular weight hydrocarbon polymers, including polyesters, and viscosity index improver dispersants, which function as dispersants as well as viscosity index improvers. Oil soluble viscpsity modifying polymers generally have weight average molecular weights of from about 10,000 to 1,000,000, preferably 20,000 to 500,000, as determined by gel permeation chromatography or light scattering methods.
Representative examples of suitable viscosity modifiers are polyisobutylene, copolymers of ethylene and propylene, polymethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, interpolymers of styrene and acrylic esters, and partially hydrogenated copolymers of styrene/ isoprene, styrene/butadiene, and isoprene/butadiene, as well as the partially hydrogenated homopolymers of butadiene and isoprene.
Corrosion inhibitors, also known as anti-corrosive agents, reduce the degradation of metallic parts contacted by the lubricating oil composition.
Oxidation inhibitors, or antioxidants, reduce the tendency of mineral oils to deteriorate in service, evidence of such deterioration being, for example, the production of varnish-like deposits on the metal surfaces and of sludge, and viscosity growth. Suitable oxidation inhibitors include ZDDPs, aromatic amines, for example alkylated phenylamines and phenyl alphanapthylamine, hindered phenols, alkaline earth metal salts of sulphurized alkyl-phenols having preferably C₅ to C₁₂ alkyl side chains, e.g., calcium nonylphenyl sulphide; barium octylphenyl.sulphide; and phosphosulphurized or sulphurized hydrocarbons.
ZDDPs, which also act as antiwear agents, are zinc dihydrocarbyl dithiophosphates. Especially preferred ZDDPs for use in oil-based compositions are those of the formula zn[SP(S)(OR)(OR¹)]₂ wherein R and R¹ may be the same or different hydrocarbyl radicals containing from 1 to 18, and preferably 2 to 12, carbon atoms, for example, alkyl, alkenyl, aryl, aralkyl, alkaryl and cycloaliphatic radicals. Particularly preferred as R and R¹ radicals are alkyl radicals having 2 to 8 carbon atoms. Examples of radicals which R and R¹ may represent are ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-heptyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl and butenyl radicals. In order to obtain oil solubility, the total number of carbon atoms in R and R¹ will generally be about 5 or greater.
Other oxidation inhibitors or antioxidants which may be used in lubricating oil compositions comprise oil-soluble copper compounds. The copper way be blended into the oil as any suitable oil-soluble copper compound. By oil-soluble it is meant that the compound is oil-soluble under normal blending conditions in the oil or additive package. The copper compound may be in the cuprous or cupric form. The copper may, for example, be in the form of a copper dihydrocarbyl thio- or dithio-phosphate. Alternatively, the copper may be added as the copper salt of a synthetic or natural carboxylic acid. Examples of suitable acids include C₈ to C₁₈ fatty acids, such, for example, as stearic or palmitic acid, but unsaturated acids such, for example, as oleic acid or branched carboxylic acids such, for example, as naphthenic acids of molecular weights of from about 200 to 500, or synthetic carboxylic acids, are preferred, because of the improved handling and solubility properties of the resulting copper carboxylates. Also useful are oil-soluble copper dithiocarbamates of the general formula R_cR_d(NCSS)_zCu, where z is 1 or 2, and R_c and R_d are the same or different hydrocarbyl radicals containing from 1 to 18, and preferably 2 to 12, carbon atoms, and including radicals such, for example, as alkyl, alkenyl, aryl, aralkyl, alkaryl and cycloaliphatic radicals. Particularly preferred as R_c and R_d groups are alkyl groups of from 2 to 8 carbon atoms. Thus, the radicals may, for example, be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-heptyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, or butenyl radicals. In order to obtain oil solubility, the total number of carbon atoms (i.e. the carbon atoms in R_c and R_d) will generally be about five or greater. Copper sulphonates, phenates, and acetylacetonates may also be used.
Examples of useful copper compounds are copper CU^I and/or Cu^II salts derived from an alkenyl succinic acid or anhydride. The salts themselves may be basic, neutral or acidic. They may be formed by reacting (a) polyalkylene succinimides (typically having polymer groups of number average molecular weight ( $\bar{M}$
_n) of 700 to 5,000) derived from polyalkylene-polyamines, which have at least one free carboxylic acid group, with (b) a reactive metal compound. Suitable reactive metal compounds include those such, for example, as cupric or cuprous hydroxides, oxides, acetates, borates, and carbonates or basic copper carbonate.
Examples of these metal salts are Cu salts derived from polyisobutenyl succinic anhydride, and Cu salts derived from polyisobutenyl succinic acid. Preferably, the copper is in its divalent form, Cu^II. The preferred substrates are polyalkenyl succinic acids in which the alkenyl group has a molecular weight greater than about 700. The alkenyl group desirably has a $\bar{M}$
_n from about 900 to 1,400, and up to 2,500, with a $\bar{M}$
_n of about 950 being most preferred. Especially preferred is polyisobutylene succinic anhydride or acid. These materials may desirably be dissolved in a solvent, for example, a mineral oil, and heated in the presence of a water solution (or slurry) of the metal-bearing material to a temperature of about 70°C to about 200°C. Temperatures of 100°C to 140°C are normally adequate. It may be necessary, depending upon the salt produced, not to allow the reaction mixture to remain at a temperature above about 140°C for an extended period of time, e.g., longer than 5 hours, or decomposition of the salt may occur.
The copper antioxidants (e.g., Cu-polyisobutenyl succinate, Cu-oleate, or mixtures thereof) will generally be employed in an amount of from about 5 to 500 ppm by weight of the copper, in the final lubricating composition.
Friction modifiers and fuel economy agents which are compatible with the other ingredients of the final oil may also be included. Examples of such materials are glyceryl monoesters of higher fatty acids, for example, glyceryl mono-oleate, esters of long chain polycarboxylic acids with diols, for example, the butane diol ester of a dimerized unsaturated fatty acid, and oxazoline compounds.
Dispersants maintain oil-insoluble substances, resulting from oxidation during use, in suspension in the fluid, thus preventing sludge formation and precipitation or deposition on metal parts. So-called ashless dispersants are organic materials which form substantially no ash on combustion, in contrast to the metal-containing (and thus ash-forming) detergents described above. Suitable dispersants include, for example, derivatives of long chain hydrocarbon substituted carboxylic acids in which the hydrocarbon - groups contain 50 to 400 carbon atoms, examples of such derivatives being derivatives of high molecular weight hydrocarbyl-substituted succinic acid. Such hydrocarbon-substituted carboxylic acids may be reacted with, for example, a nitrogen-containing compound, advantageously a polyalkylene polyamine, or with an ester. Such nitrogen-containing and ester dispersants are well known in the art. Particularly preferred dispersants are the reaction products of polyalkylene amines with alkenyl succinic anhydrides.
In general, suitable dispersants include oil soluble salts, amides, imides, oxazolines and esters, or mixtures thereof, of long chain hydrocarbon-substituted mono and dicarboxylic acids or their anhydrides; long chain aliphatic hydrocarbons having a polyamine attached directly thereto; and Mannich condensation products formed by condensing about 1 molar proportion of a long chain substituted phenol with about 1 to 2.5 moles of formaldehyde and about 0.5 to 2 moles of a polyalkylene polyamine. In these dispersants long chain hydrocarbon groups are suitably derived from polymers of a C₂ to C₅ monoolefin, the polymers typically having a number average molecular weight of from 700 to 5000. As indicated above, a viscosity index improver dispersant functions both as a viscosity index improver and as a dispersant. Examples of viscosity index improver dispersants suitable for use in accordance with the invention include reaction products of amines, for example polyamines, with a hydrocarbyl-substituted mono - or dicarboxylic acid in which the hydrocarbyl substituent comprises a chain of sufficient length to impart viscosity index improving properties to the compounds. In general, the viscosity index improver dispersant may be, for example, a polymer of a C₄ to C₂₄ unsaturated ester of vinyl alcohol or a C₃ to C₁₀ unsaturated mono-carboxylic acid or a C₄ to C₁₀ di-carboxylic acid with an unsaturated nitrogen-containing monomer having 4 to 20 carbon atoms; a polymer of a C₂ to C₂₀ olefin with an unsaturated C₃ to C₁₀ mono- or di-carboxylic acid neutralized with an amine, hydroxyamine or an alcohol; or a polymer of ethylene with a C₃ to C₂₀ olefin further reacted either by grafting a C₄ to C₂₀ unsaturated nitrogen - containing monomer thereon or by grafting an unsaturated acid onto the polymer backbone and then reacting carboxylic acid groups of the grafted acid with an amine, hydroxy amine or alcohol.
Examples of dispersants and viscosity index improver dispersants which may be used in accordance with the invention may be found in European Patent Specification No. 24146 B, the disclosure of which is incorporated herein by reference.
Antiwear agents include zinc dihydrocarbyl dithiophosphates (ZDDPs), for example, those indicated above as oxidation inhibitors.
Pour point depressants otherwise known as lube oil flow improvers, lower the temperature at which the fluid will flow or can be poured. Such additives are well known. Typical of those additives which improve the low temperature fluidity of the fluid are C₈ to C₁₈ dialkyl fumarate/vinyl acetate copolymers, polymethacrylates, and wax naphthalene. Foam control can be provided by an antifoamant of the polysiloxane type, for example, silicone oil or polydimethyl siloxane.
Some of the above-mentioned additives can provide a multiplicity of effects; thus for example, a single additive may act as a dispersant-oxidation inhibitor. This approach is well known and need not be further elaborated herein.

When lubricating compositions contain one or more of the above-mentioned additives, each additive is typically blended into the base oil in an amount which enables the additive to provide its desired function. Representative effective amounts of such additives, when used in crankcase lubricants, are as follows:

Additive	Mass % a.i.*	Mass % a.i.*
	(Broad)	(Preferred)
Detergents/Rust inhibitors	0.01-6	0.01-3
Viscosity Modifier	0.01-6	0.01-4
Corrosion Inhibitor	0.01-5	0.01-1.5
Oxidation Inhibitor	0.01-5	0.01-1.5
Dispersant	0.1-20	0.1-8
Pour Point Depressant	0.01-5	0.01-1.5
Anti-Foaming Agent	0.001-3	0.001-0.15
Anti-wear Agents	0.01-6	0.01-4
Friction Modifier	0.01-5	0.01-1.5
Mineral or Synthetic Base Oil	Balance	Balance

* Mass % active ingredient based on the final oil.

When used in marine applications, relatively larger amounts of overbased metal-containing detergents may be used. For example, marine diesel cylinder lubricants may contain 10 mass % or more, preferably 12.5 to 30 mass %, of detergent so that the lubricant has an overall TBN of at least 20, preferably at least 70.
When a plurality of additives are employed it may be desirable, although not essential, to prepare one or more additive concentrates comprising the additives (a concentrate being referred to herein as an additive package) whereby several additives can be added simultaneously to the base oil to form the lubricating oil composition. Dissolution of the additive concentrate(s) into the lubricating oil may be facilitated, for example, by mixing accompanied with heating, but this is not essential. The concentrate(s) or additive package(s) will typically be formulated to contain the additive(s) in proper amounts to provide the desired concentration in the final formulation when the additive package(s) is/are combined with a predetermined amount of base lubricant. Thus, one or more overbased detergents prepared in accordance with the present invention can be added to small amounts of base oil or other compatible solvents along with other desirable additives to form additive packages containing active ingredients in an amount, based on the additive package, of, for example, from about 2.5 to about 90 mass %, and preferably from about 5 to about 75 mass %, and most preferably from about 8 to about 50 mass % by weight, additives in the appropriate proportions with the remainder being base oil.
The final formulations may employ typically about 10 mass % of an additive package as described above with the remainder being base oil.
The following Examples illustrate the invention. Where the sediment level of the product obtained at the end of carbonation is quoted in the Examples and Comparative Examples, this is the volume % of dense sediment determined by centrifuging a given volume of the actual reaction mixture, including reaction solvents, and observing, using a calibrated vessel, the volume of sediment obtained. Sediment levels at the end of stripping to remove solvents and volatile materials were determined by diluting a sample of the stripping product with an equal volume of toluene, centrifuging the diluted sample, and observing the volume % of dense sediment. The observed volume % of sediment was multiplied by two in order to obtain the sediment level in the stripped product. Where gel is present, gel levels are measured in the same manner, and at the same time, as sediment levels.
TBN, where quoted, was measured by the technique described in ASTM D2896.

Example 1

A two litre reaction vessel provided with a stirrer was positioned in an ultrasonic bath capable of supplying ultrasound having a frequency of 38 kHz and an intensity of 1 to 2 watts/cm² (at the transducer face). A mixture of 720g toluene, 365g of a 70 mass % solution of an alkyl benzene sulphonic acid (molecular weight 480) in diluent oil and 13g of methanol was slowly stirred in the reaction vessel (at a stirring rate lower than that normally required for conventional mixing). The bath was then energized, and 154g of magnesium oxide were added. There was an exotherm to about 35°C. 57g of an ethylene diamine carbamate solution were then added, followed by 82.5g of methanol and 101.5g of water. The ethylene diamine carbamate solution comprised 16.5 mass % ethylene diamine, 12.2 mass % carbon dioxide, 35.65 mass % water and 35.65 mass % methanol.
After the addition of the water and methanol, the temperature of the reaction mixture was stabilized at 40°C, and carbon dioxide was then introduced into the mixture at a rate of 39g/hour. During carbonation, the temperature of the ultrasonic bath was controlled by means of a heater situated in the bath so that the reaction temperature rose to about 68°C over a period of about 180 minutes and then fell back to 65°C, at which it was maintained. The ultrasound treatment was continued until carbonation was terminated.
Carbonation was terminated when 175g of carbon dioxide had been passed into the reaction mixture. The product contained 0.8 vol. % sediment. Solvents were then removed by distillation to 165°C at atmospheric pressure, 260g of diluent oil being added when the temperature reached 80°C. The product obtained after distillation was vacuum stripped to remove the final traces of water and solvent, and then filtered at a rate of 159 litres/m²/hr in a pressure filter through a bed of diatomaceous earth. The overbased magnesium sulphonate produced had a TBN of 419mg KOH/g.

Comparative Example 1

Example 1 was repeated except that ultrasound was not applied and the stirrer speed was increased to give conventional mixing. Neutralization and carbonation were carried out with the reaction vessel positioned in the (unactivated) ultrasonic bath, and the same temperatures as in Example 1 were used, the temperature being controlled by means of the heater in the bath. The mixture obtained at the end of carbonation contained 1.4 vol. % sediment. The filtration rate was 115 l/m²/hr, and the product had a TBN of 422mg KOH/g.

Example 2

Example 1 was repeated except that during carbonation the temperature of the ultrasonic bath was maintained at a level of about 2°C below the reaction temperature: the reaction temperature rose to about 75°C over a period of about 88 minutes, and then gradually declined to 65°C, at which it was maintained by heating. The mixture obtained at the end of carbonation contained 0.4 vol. % sediment. The filtration rate was 299 l/m²/hr, and the product had a TBN of 430 mg KOH/g.

Comparative Example 2

Example 2 was repeated except that ultrasound was not applied and the stirrer speed was increased to give conventional mixing. Neutralization and carbonation were carried out with the reaction vessel positioned in the (unactivated) ultrasonic bath, and the same temperatures as in Example 2 were used, the temperature being controlled by means of the heater in the bath. The mixture obtained at the end of carbonation contained 0.7 vol. % sediment. The filtration rate was 131 l/m²/hr, and the product had a TBN of 426 mg KOH/g.

Example 3

A mixture of 154g magnesium oxide and 500g of toluene was subjected for 6 minutes to treatment with an ultrasonic probe supplying ultrasound having a frequency of 20 kHz and an intensity of 140 watts/cm² (at the face of the probe) to form a magnesium oxide dispersion.
365g of a 70 mass % solution of an alkyl benzene sulphonic acid (molecular weight 480) in diluent oil, 220g of toluene and 13g of methanol were introduced into a two litre reaction vessel fitted with a stirrer, temperature controller, gas distribution tube and reflux condenser. To the mixture so obtained there was added the magnesium oxide dispersion prepared as described above, followed by 110g of water, 82.5g of methanol, and 57g of the ethylene diamine carbamate solution used in Example 1.
The temperature of the reaction mixture was stabilized at 40°C, and carbon dioxide was then injected into the mixture at a rate of 39g/hour. The temperature increased to 63°C and then slowly declined. When the temperature had dropped to 60°C, heat was applied to maintain the temperature at that level. After 138g of carbon dioxide had been injected into the mixture, the condenser was changed to the distillation position. Injection of carbon dioxide was terminated after 175g of carbon dioxide had been passed into the reactor. The product obtained at the end of carbonation contained 0.25 vol. % sediment.
After termination of carbonation, solvents were removed by distillation at 165°C at atmospheric pressure, 260g of diluent oil being added when the temperature reached 80°C. When the temperature reached 165°C, a vacuum of 23in mercury (78 kPa) was applied to the reactor to ensure that the last traces of water and solvents were removed. The product obtained, which contained 0.4 vol. % sediment, was then filtered in a pressure filter through a bed of filter aid to give a magnesium sulphonate with a TBN in excess of 400mg KOH/g.

Comparative Example 3

Example 3 was repeated, except that the magnesium oxide was not treated with ultrasound before use. The sediment level at the end of carbonation was 0.5 vol. %, and that after stripping to remove water and solvents was 1.0 vol. %.

Example 4A

408.1g of toluene, 82.6g of diluent oil, 149.3g of calcium hydroxide and 10.2g of methanol were introduced into a stirred reaction vessel and 584.9g of a mixture of an alkyl benzene sulphonic acid (70 mass % active ingredient in diluent oil) and toluene in a mass ratio of 1:1 were added, followed by 401.0g of methanol and 28.3g of water. The mixture was then transferred into a beaker and stirred while being subjected for 10 minutes to treatment with an ultrasonic probe (Lucas Dawe Sonifier 250 obtainable from Lucas Dawe Ultrasonics Limited, Bradford, England) supplying ultrasound having a frequency of 20 kHz at an output power meter reading of 70 %.
The treated mixture was returned to the reaction vessel and maintained at 33°C while 66.5g of carbon dioxide were introduced over a period of 1 hour 30 minutes. The reaction mixture was then heated over a period of an hour to 60°C and then cooled to 33°C. 135g of calcium hydroxide were then added, following which 66.5g of carbon dioxide were introduced over a period of 1 hour 30 minutes.
At the end of the second treatment with carbon dioxide, the product contained 2.7 vol. % of sediment. The reaction mixture was then heated over a period of an hour to 60°C, in a "heat soaking" step. After this heating step, the product contained 1.6 vol. % of sediment.

Example 4B

Example 4A was repeated, with the minor variations indicated below in the amounts of components, except that the treatment with ultrasound was carried out on an initial slurry of calcium hydroxide.
408.1g of toluene, 83.2g of diluent oil and 148.9g of calcium hydroxide were stirred in a beaker and subjected to the sonication treatment described in Example 4A. The treated mixture was then introduced into a stirred reaction vessel and 584.2g of the mixture of alkyl benzene sulphonic acid and toluene used in Example 4A were added. 400.1g of methanol and 27.9g of water were then added, following which carbon dioxide was introduced as in Example 4A. Subsequent stages of the process were as described in Example 4A.
At the end of the second treatment with carbon dioxide, the product contained 3.0 vol. % sediment, while after a final heating step (to 65°C) the sediment level was 1.4 vol. %.

Comparative Example 4

Example 4A was repeated except that the treatment with ultrasound was omitted. At the end of the second treatment with carbon dioxide, the product contained 3.2 vol. % of sediment, and after the final heating step the sediment level was 2.0 vol. %.

Example 5

An overbased calcium sulphonate having a TBN of about 400 mg KOH/g was prepared as follows:
612.4g of toluene, 124.3g of diluent oil, 223.7g of calcium hydroxide and 16.0g of methanol were introduced into a stirred reaction vessel, and 876g of a mixture of an alkyl benzene sulphonic acid (70 mass % active ingredient in diluent oil) and toluene in a mass ratio of 1:1 were added. The contents of the vessel were cooled and maintained at a maximum of 27°C. 601.2g of methanol and 42g of water were then added. The temperature was maintained at 33°C while 99.8g of carbon dioxide were introduced over 1 hour 40 minutes. The reaction mixture was then heated, over a period of 1 hour, to 60°C, and then cooled to 33°C. 202g of calcium hydroxide were then added, following which 99.8g of carbon dioxide were introduced, over a period of 1 hour 41 minutes, while maintaining the temperature at 33°C. The reaction mixture was then heated to 65°C over 1 hour and 352g of diluent oil were added.
After stripping, by distillation, to remove solvents and volatile materials, a 400g sample of the stripped product contained 5 vol. % dense sediment and 9 vol. % black gel. This product would be expected to cause immediate blocking of a filter, so that the filtration rate would be zero.
The 400g sample was subjected for 10 minutes to treatment with an ultrasonic probe supplying ultrasound having a frequency of 20 kHz and an intensity (at the face of the probe) of 47 watts/cm². After the ultrasound treatment, the sulphonate contained only 4.4 vol. % dense sediment, and there was no visible gel. On repeating the sonication for a further period of 10 minutes, the level of dense sediment was reduced to 3.8 vol. % and, again, there was no visible gel. On filtering the sonicated product in a pressure filter through a layer of diatomaceous earth, the filtration rate was 288kg/m²/hr. The filtered product had a TBN in excess of 388mg KOH/g.

Comparative Example 5

The preparative method used in Example 5 was repeated on a somewhat smaller scale:
408g of toluene, 83g of diluent oil, 149g of calcium hydroxide and 10g of methanol were introduced into the stirred reaction vessel used in Example 4, and 584g of the sulphonic acid/toluene mixture used in Example 5 were added. The temperature was maintained at a maximum of 28°C by cooling. 400g of methanol and 28g of water were then added, and the temperature was maintained at 33°C while 66.5g of carbon dioxide were introduced over a period of 1 hour 28 minutes. The reaction mixture was then heated to 65°C over a period of 1 hour, and then cooled to 33°C over a period of 10 minutes. 135g of calcium hydroxide were then added, following which 66.5g of carbon dioxide were introduced, over a period of 1 hour 30 minutes, while maintaining the temperature at 33°C. The reaction mixture was then heated to 65°C over a period of 1 hour. 235g of diluent oil were added when the temperature reached 63°C.
After stripping, by distillation, to remove solvents and volatile materials, the stripped product contained 2.4 vol. % dense sediment and 1.6 vol. % black gel. On filtering the product in a pressure filter through a layer of diatomaceous earth under the same conditions as in Example 5, the filtration rate was only 37kg/m²/hr, in contrast to the much higher rate of 288kg/m²/hr obtained in Example 5 when a product which initially contained a higher sediment level was subjected to treatment with ultrasound. The filtered product obtained in Comparative Example 5 had a TBN in excess of 390mg KOH/g.

Examples 6 and 7 and Comparative Examples 6 and 7

An overbased calcium sulphonate having a TBN of about 400mg KOH/g was prepared following the procedure described in Example 5 with the following differences: 33 g of water was used; the temperature was maintained at 28°C during the introduction of carbon dioxide; at the end of the first introduction of carbon dioxide, the reaction mixture was heated to 60°C over a period of 1 hour, and then held at 60°C for 15 minutes before cooling; at the end of the second introduction of carbon dioxide, the reaction mixture was heated to 62°C over a period of 1 hour and maintained at 62°C for 15 minutes.
The preparation was repeated three more times and the four stripped products were mixed together to form a masterbatch. Samples of approximately 600g were taken from this masterbatch. Each sample was found to contain 2.2 vol. % dense sediment. Each sample was filtered rapidly through a 150 µm mesh to remove any large particles which might have partially blocked the jet in the ultrasound apparatus (such treatment would not be necessary when using a larger scale apparatus). After filtration through the mesh, each sample contained 2.0 vol. % sediment.
One of the samples was treated with ultrasound using a Lucas Dawe Minisonic type 4005 apparatus obtainable from Lucas Dawe Ultrasonics Limited, Bradford, England. ("Minisonic" is a trade mark.) The apparatus comprises two glass vessels and a fluid to be treated can be pumped from one vessel to the other through the ultrasonic head. In the head, the fluid passes at high velocity through a special orifice and emerges as a thin flat stream which is bisected by a blade which is caused by the fluid to vibrate at 20 kHz. The power to the pump can be set on a scale of from "low" to "high". The fluid can be passed once from the first vessel to the second through the head (single pass) or can then be pumped back to the first vessel (via the head), with, optionally, further passes in the same manner (multiple passes).
The apparatus can also be used in a "recycle" mode, wherein, after passing through the head, the feed is pumped directly back into the first vessel without passing through the head or into the second vessel. In Examples 6 and 7, sonication was continuous, using the recycle mode, and was carried out for 10 minutes with the pump control on the high setting.
The treated sample was filtered, through a filter cake, in admixture with a quantity of filter-aid, and the filtration rate, mass of separated sediment, and mass of product lost on the filter cake were noted (Example 6). A further treated sample was filtered using approximately half the quantity of the admixed filter-aid (Example 7).
Examples 6 and 7 were repeated without subjecting the samples to ultrasound before filtration (Comparative Examples 6 and 7 respectively).

The results are summarized in Table I.

TABLE I

	Example 6	Example 7	Comparative Ex. 6	Comparative Ex. 7
Sediment before sonication (vol. %)	2.0	2.0	2.0	2.0
Sediment after sonication (vol. %)	1.4	1.2	N/A	N/A
Mass filtered (g)	611.8	614.1	612.3	613.5
Admixed filter-aid (g)	18.4	9.2	18.0	9.2
Filtration rate (kg/m²/hr)	482	310	306	147
Mass of separated sediment (g)	6.66	6.31	6.86	6.65
Mass of product lost on filter cake (g)	18.14	14.7	20.66	21.77
N/A = not applicable

Comparison of Example 6 and Comparative Example 6, and Example 7 and Comparative Example 7 shows that the ultrasound treatment increased the filtration rate. Comparative Examples 6 and 7 show that, in the absence of ultrasound treatment, halving the amount of filter-aid mixed with the sample to be filtered also halved the filtration rate. As shown in Example 7, however, there was a lower reduction in filtration rate, and less product was lost on the filter cake (while the filtration rate remained at an acceptable level), when the sample was treated with ultrasound before filtration. It will be noted that the mass of separated sediment was substantially constant.

Example 8 and Comparative Example 8

Five samples of an overbased calcium sulphonate were prepared, the procedure described in Examples 6 and 7 being used in each case. For Example 8, the samples were not mixed to form a masterbatch. Before filtration as described below, each sample was filtered rapidly through a 150 pm mesh as described in Examples 6 and 7. One sample (Sample 1) was filtered without treatment with ultrasound (Comparative Example 8), while each of the other samples was treated in the Minisonic apparatus described in Examples 6 and 7, with the power control half way between the low and high settings, and then filtered. All variables except the number of sonication passes were held constant. The results are summarized in Table II.

Table II

Sample	1	2	3	4	5
Number of sonic passes	0	5	10	15	20
Sediment level before ultrasound treatment (vol %)	3.8	3.0	3.6	2.2	2.6
Sediment level after ultrasound treatment (vol %)	-	2.0	1.8	1.8	1.9
Filtration rate (kg/m²/hr)	Filter blocked	19	21	97	110
TBN (mg KOH/g)	346	345	359	392	392

The sediment levels before ultrasound treatment show the variation to be expected at the levels of sediment in question. The TBN was measured after filtration. A relatively low TBN will usually be obtained if a product filters very slowly (in this case at a rate of the order of 20 kg/m²/hr).
Table II shows that, in the system tested, increasing the number of sonic passes from 5 to 15 gave a significant increase in the filtration rate and the TBN, and, in all cases, sonication gave a decrease in sediment level and increase in filtration rate over the case where the sample was not subjected to treatment with ultrasound.

Example 9 and Comparative Example 9

Seven samples of an overbased calcium sulphonate were prepared, the procedure used in Examples 6 and 7 being used in each case. Before filtration as described below, each sample was filtered rapidly through a 150µm mesh as described in Examples 6 and 7.
One sample (Sample 1) was filtered without treatment with ultrasound (Comparative Example 9), while each of the other samples was treated in the Minisonic apparatus described in Examples 6 and 7, with the power control halfway between the low and high settings, and then filtered. All variables except the type and time of the treatment with ultrasound were kept constant. The results are summarized in Table III.
The sediment levels before ultrasound treatment show the variation to be expected at the level of sediment in question. The TBN was measured after filtration.
Table III shows that, in all cases, sonication reduced the sediment level and increased the filtration rate. Once a high filtration rate was achieved, further sonication had no further effect.

Example 10 and Comparative Example 10

An overbased calcium sulphonate was prepared as follows:
2698g of toluene, 107.9g of diluent oil, 1547.8g of calcium hydroxide and 13g of methanol were introduced into a stirred reaction vessel, and 3241.8g of an alkyl benzene sulphonic acid (60 mass % active ingredient in diluent oil) were added, followed by 682g of toluene, 2527g of methanol and 136.5g of water. The temperature was then maintained in the range of from 27.1°C to 29.7°C while 724.4g of carbon dioxide were introduced over a period of 3 hours. The temperature was then raised to 45.8°C, and 1325.9g of diluent oil were added, following which the temperature was raised to 75°C over a period of 42 minutes. Solvents and volatile materials were then removed by distillation.
Samples of approximately 700g were taken from the product prepared as described above. One sample (Sample 1: Comparative Example 10) was filtered in a pressure filter through a bed of diatomaceous earth without further treatment. Each of three other samples (Samples 2 to 4) was subjected to treatment with ultrasound for 10 minutes using an ultrasonic probe having a frequency of 20 kHz and a power output as indicated in Table IV below. The treated samples were then filtered in the same manner as the untreated sample. The results obtained are summarized in Table IV. TABLE IV

Sample No. 1 2 3 4

Ultrasonic power output (watts) N/A 25 42 to 46 58 to 64

Filtration rate (kg/m²/hr) 140 451 549 576

TBN of product (mgKOH/g) 312 314 313 313

N/A = not applicable
In each case, treatment with ultrasound led to a significant increase in the filtration rate, the increase being greatest when the ultrasonic power output was highest.

Example 11

The material used was a commercial overbased calcium phenate, having a TBN of 250mg KOH/g, from which the solids had been removed by centrifugation rather than filtration.
1236.2g of the calcium phenate described above were treated in the Minisonic apparatus described in Examples 6 and 7. The treatment was carried out for 10 minutes with the apparatus in the recycle mode and the power control on the high setting. 842g of the treated product were filtered at a gauge pressure of 40 psi (276 kPa) through a bed of diatomaceous earth. The filtration rate was 1238 kg/m²/hr.

Comparative Example 11

820.6g of the commercial calcium phenate described in Example 11 were filtered as described in Example 11, but without treatment with ultrasound. The filtration rate was 977 kg/m²/hr, significantly lower than that obtained in Example 11.

Claims

A process for the preparation of an overbased metal-containing detergent which process comprises treating with CO₂ a mixture comprising a metal-containing detergent selected from the group consisting of phenate sulphonate, sulphurized phenate and salicylate and a metal-containing basic compound selected from the group consisting of a metal oxide, metal hydroxide and metal alkoxide, in which process a starting material, a reaction mixture or a reaction product is treated with ultrasound.
A process as claimed in claim 1, wherein the metal-containing detergent comprises at least one metal selected from alkali and alkaline earth metals and magnesium.
A process as claimed in claim 1, wherein the metal-containing detergent is a sulphonate or phenate of calcium and/or magnesium.
A process as claimed in any one of claims 1 to 3, wherein the overbased metal-containing detergent has a TBN of at least 50mg KOH/g.
A process as claimed in claim 4, wherein the overbased metal-containing detergent has a TBN of at least 300mg KOH/g.
A process as claimed in any of claims 1 to 5 wherein the metal-containing detergent is prepared by reacting an oil-soluble acid with a metal-containing basic compound.
A process as claimed in any of one of claims 1 to 6, wherein ultrasound is used to treat a starting material which comprises a metal-containing basic compound.
A process as claimed in any one of claims 1 to 7, wherein ultrasound is used to treat a reaction mixture comprising a metal-containing basic compound and an oil-soluble acid capable of reacting with the basic compound to form a metal-containing detergent.
A process as claimed in any one of claims 1 to 7, wherein ultrasound is used to treat a reaction mixture comprising an oil-soluble metal-containing detergent and a metal-containing basic compound, while CO₂ is passed into the reaction mixture.
A process as claimed in any of claims 1 to 9, wherein ultrasound is used to treat a reaction product which comprises the overbased metal-containing detergent and impurities.
The use of ultrasound in the preparation of an overbased metal-containing detergent to reduce sediment levels and/or the proportion of waste material obtained and/or to increase the filtration rate of the overbased metal-containing detergent.