APPARATUS FOR THE PRODUCTION OF PHOSPHOROUS OR NITROGEN-CONTAINING COMPOUNDS

Abstract: A dihydrocarbyl dithiophosphate or dithiocarbamate suitable for use as a lubricating oil additive is prepared from reactants in different phases by reacting the reactants in a reaction region defined by adjacent surfaces between which there is relative movement or in a thin film on a surface over which they move.

Description: APPARATUS FOR THE PRODUCTION OF PHOSPHORUS OR NITROGEN-CONTAINING COMPOUNDS The invention relates to improvements in the manufacture of phosphorus- or nitrogen-containing compounds, especially compounds suitable for use as lubricating oil additives or as intermediates suitable for use in the manufacture of such additives. For the past 30 to 50 years, lubricating oils used as crankcase lubricants in internal combustion engines in automobiles and trucks have normally contained phosphorus- or nitrogen-containing compounds, which in many cases also contained sulphur, to improve their efficiency and useful life. One important class of such compounds comprises zinc dihydrocarbyl dithiophosphates (ZDDPs). ZDDPs are primarily antiwear agents, but also provide antioxidant activity. Another important class of such compounds comprises metal dithiocarbamates (DTCs), which may be included in lubricating oil to provide a source of, for example, sulphur. In view of the very considerable commercial importance of ZDDPs and DTCs, many different proposals have been made over many years for improving processes for their production, examples of such proposals being those described in British Patent Specification No. 2 194 239A and East German Patent Specification No. 278 799A. Despite the very considerable work that has been carried out in this field, however, the applicants have found that it is possible, in a relatively simple manner, to make very significant improvements in the production of these and related compounds. The invention provides a process for the manufacture of a compound of the general formula SUBSTITUTE SHEET wherein A represents an -0-P-O- or an _> -C group; each of X 1 and X 2 , which may be the same or different, represents 0 or S; each of R 1 and R 2 , which may be the same or different, represents a hydrocarbyf radical, M represents H, a metal ion, or an ammonium group; and n represents an integer equal to the valency of M, with the proviso that, when A represents an _>N-C group, both X 1 and X 2 represent S, in which process a first reactant is present in a different phase from a second reactant and the said reactants are reacted in a region defined by a surface and at least one member adjacent to the surface, there being relative movement between the surface and the member(s) such that the reactants are caused to move relative to the surface. Advantageously, the region is defined by adjacent surfaces between which there is relative movement such that the reactants are caused to move relative to one or both of the surfaces. The invention also provides a process for the manufacture of a compound of the general formula wherein A represents an -0-P-O- or an ]>N-C group; each of X 1 and X 2 , which may be the same or different, represents O or S; each of R 1 and R 2 , which may be the same or different, represents a hydrocarbyl radical, M represents H, a metal ion, or an ammonium group; and n represents an integer equal to the valency of , with the proviso that, when A represents an ;>N-C group, both X 1 and X 2 represents S, in which process a first reactant is present in a different phase from a second reactant and the reactants are reacted in a thin film on a surface over which they move, the average velocity (taken across the thickness of the film) of a mixture of SHEET the reactants in a direction parallel to the surface being at least 1 m sβα The thin film is advantageously formed between the surface and at least one member adjacent to the surface, preferably between adjacent surfaces, there being relative movement between the surface and the member(s), or between the surfaces, causing the said movement of the reactants. The invention also provides compounds of the above general formula prepared by the process of the invention, especially such compounds which are suitable for use as additives for lubricating oils. The compounds of the general formula given above contain two hydrocarbyl radicals, which may be the same or different. As used in this specification, the term "hydrocarbyl" denotes a radical having a carbon atom directly attached to the remainder of the molecule and having a hydrocarbon or predominantly hydrocarbon character. Hydrocarbyl radicals include the following: (1 ) Hydrocarbon groups; that is, aliphatic, (e.g. alkyl or alkenyl), alicyclic (e.g. cycloalkyl or cycloalkenyl), aromatic, aliphatic- and alicyclic-substitutβd aromatic, and aromatic-substituted aliphatic and alicyclic groups, and cyclic groups wherein the ring is completed through another portion of the molecule (that is, any two indicated substituents may together form an alicyclic group). Examples of hydrocarbon groups include methyl, ethyl, octyl, decyl, octadecyl, cyclohexyl, and phenyl groups. (2) Substituted hydrocarbon groups; that is, groups containing non- hydrocarbon substituents which do not alter the predominantly hydrocarbon character of the group. Examples of suitable substituents include halo, hydroxy, nitro, cyano, alkoxy, and acyl groups. (3) Hetero groups; that is, groups which, while predominantly hydrocarbon in character, contain atoms other than carbon in a chain or ring otherwise composed of carbon atoms. Suitable hetero atoms include, for example, nitrogen, oxygen and sulphur. In general, no more than about three substituents or hetero atoms, and preferably no more than one, will be present for each 10 carbon atoms in the hydrocarbyl group. SUBSTITUTE SHEET Especially preferred compounds for use in oil-based compositions are those wherein R 1 and R 2 in the above general formula contain from 1 to 18, and preferably 2 to 12, carbon atoms. Particularly preferred as R 1 and R 2 radicals are alkyl radicals having 2 to 8 carbon atoms. Examples of radicals which R 1 and R 2 may represent are ethyl, n-propyl, i-propyl, π-butyl, i-butyl, sec-butyl, amyl, π-hexyl, i-hexyf, n-heptyl, n-octyl, decyl, dodecyl, octadecyl, 2-βthylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl and butenyl radicals. The total number of carbon atoms in R 1 and R 2 is preferably sufficient to impart oil- solubility to the compounds. In order to obtain oil solubility, the total number of carbon atoms in R 1 and R 2 will generally be about 5 or greater. M in the above general formula represents hydrogen, a metal ion, or an ammonium group. When M in the above general formula represents a metal ion, M is advantageously derived from a Group la metal, a Group Ha metal, aluminium, tin, lead, molybdenum, titanium, manganese, cobalt, nickel, copper, cadmium, antimony or zinc. For some uses, M preferably represents a zinc ion, as in ZDDPs. In other cases, compounds wherein M represents copper or molybdenum may have particular uses. Thus, for example, as indicated later in this specification, copper dihydrocarbyl dithiophosphates and copper dithiocarbamates have proved very useful as, inter alia, antioxidants, and molybdenum dithiocarbamates also have important uses. An ammonium cation represented by M may be derived from ammonia or a primary, secondary or tertiary amine. The ammonium cation is preferably a cation of the formula R 3 R 4 R 5 R 6 N+ wherein R 3 , R 4 , R5 and R 6 each independently, represents hydrogen, or a hydrocarbyl, aminohydrocarbyl, hydroxyhydrocarbyi, or hydroxyhydrocarbyloxyhydrαcarbyl group, or R 3 and R 4 may be hydrocarbyl groups joined together to form a ring including the nitrogen atom, and optionally, oxygen, sulphur, or other nitrogen atoms. When the groups R 3 , R 4 , R 5 and or R 6 represent hydrocarbyl groups, these groups are generally hydrocarbyl groups containing up to about 150 carbon atoms and will more often be aliphatic hydrocarbyl groups containing from about 4 to about 30 carbon atoms. Compounds of the general formula given above which find particular use as lubricating oil additives include compounds of the formula [(R 1 0)R 2 0)P(S)(0)]ή M + , and, especially, compounds of the formula [(R 1 0)(R 2 0)P(S)S]n n+ (particularly dihydrocarbyl dithiophosphates in which M represents Zn or Cu) and compounds of the formula {R 1 R 2 NC(S)S]n M n + (particularly dithiocarbamates in which M represents Zn, Mo or Cu). Copper may be in the cuprous or cupric form. The invention is applicable to processes for manufacturing compounds of the general formula (I) involving a chemical reaction between reactants which are present in different phases, that is, reactants which are to some extent mutually insoluble. Normally, each of the first and second reactants is present in the reaction mixture as a liquid or solid. ZDDPs are normally prepared by a first step which comprises forming a dihydrocarbyl dithiophosphoric acid (a DDPA), usually by reaction of one or more alcohols or phenols with a phosphorus sulphide, usually P2S5 (although P 4 S3 and other sulphides may be used), and a second step in which the dihydrocarbyl dithiophosphoric acid, and optionally an added carboxylic acid, is neutralised with a zinc compound, for example, zinc oxide, zinc hydroxide, or zinc carbonate. Analogous methods may be used for other metal dihydrocarbyl dithiophosphates, replacing the zinc compound by a compound of the metal in question. Both the first step and the second step in the preparative method described above involve the reaction of a particulate solid (the P 2 S5 in the first step and the metal compound in the second step) with a liquid (the alcohol or phenol in the first step, and the DDPA in the second step). The solid is in each case to some extent insoluble in the liquid, that is, the liquid and the solid are present in different phases. The applicants have surprisingly found that very significant improvements in this long-established preparative method can be obtained if the first step, or the second step, or, preferably, both steps are carried out in accordance with the invention. Where the first step is carried out in accordance with the invention, this step may be carried out in a batchwise or, where appropriate, continuous manner. Ambient pressures may be used if desired. The temperature may be, for example, in the range of from 50 to 150°C. The process is particularly suitable for reacting SUBSTITUTE SHEET phosphorus sulphides ranging from, for example, P4S3 to P4S12, with C3 to C20 primary or secondary aliphatic alcohols, and alkylated phenols. A variable amount of hydrogen sulphide is produced, the amount in any particular case depending on the nature of the starting phosphorus sulphide. Where the reaction is carried out in a batchwise manner, the reactants may, if desired, be caused to circulate through a reactor used in accordance with the invention, in which the reactants are reacted in a region between adjacent surfaces, and a conventional stirred tank reactor or other "soaking" zone. Where the second step (the neutralisation step) is earned out in accordance with the invention, this step may be carried out batchwise or, where appropriate, continuously, and may if desired or required be promoted by, for example, the addition to the reaction mixture of small amounts of a carboxylic acid or a salt of such an acid. Alternatively, a mixed ZDDP/carboxylate salt may be prepared by the incorporation of relatively larger amounts of carboxylic acid in this step. Neutralisation may be carried out at ambient pressures. The temperature used may, for example, be in the range of from 50 to 150°C, the temperature used in any particular case depending on the nature of the acid being neutralized. The first step and/or the second step may if desired be carried out at reduced pressures to facilitate the removal of gaseous by-products. In carrying out reactions in accordance with the invention, particularly advantageous results may be obtained if the mass ratio of the reactants is kept substantially constant during the reaction. The optimum ratio for any given apparatus and reaction can be ascertained by routine experiment. For guidance, particularly advantageous mass ratios of reactants for the specific processes referred to above carried out in one type of laboratory-scale reactor are indicated in Table 1 , where % heterogeneous phase = mass of reactant used in the smaller proportion x 100 mass of reactant used in the larger proportion For the specific processes referred to above and in Table 1 , the reactant present in the solid phase is the reactant used in the smaller proportion. SUBSTITUTE SHEET Tablfl 1 % heterogeneous phase Reaction Broad Preferred DDPA Production 10-60 25-45 Neutralisation 0.5-20 M2 The mass of the liquid phase reactant may in some cases include the mass of a solvent or diluent Examples of improvements that may be obtained in the production of ZDDPs by a process in accordance with the invention are one or more of improved DDPA and ZDDP quality, with fewer unwanted by-products, reduction in the risk of ZDDP decomposition, improved utilization of raw materials, improved rate of production of the product and/or a reduction in amounts of sediment obtained at the end of the process, with a consequent reduction in amounts of unwanted material to be removed, for example, by filtration, and to be disposed of. Indeed, in some cases, it may be possible completely to eliminate the need for a final filtration step. Further, in some cases, for example, when using primary alcohols, the invention may make it possible to carry out the process in a continuous manner, rather than batchwise. In certain cases, the use of a semicontinuous procedure, where one or more reactants are added while a reaction is already taking place, may be advantageous. Examples of advantageous results which have been observed in laboratory preparations of ZDDPs, by a process in accordance with the invention carried out in a reactor of the type used in the Examples herein are a 10-fold reduction in final sediment or a 20 to 50-fold increase in rate of production, results obtained in accordance with the invention being compared in each case with results obtained when carrying out the same process in a conventional stirred reactor. It will be appreciated that, although the above discussion is primarily in terms of ZDDPs, the invention is also applicable to the preparation of ammonium salts and other metal salts of dihydrocarbyl dithiophosphoric acids. Further, the first step indicated above may be used in the preparation of materials which are not subsequently reacted with zinc compounds to form ZDDPs, for example, in the T reaction of P2S5 and alkyl-phenols to produce alkyl phenol dithiophosphoric acids for use, for example, as antioxidants. Dihydrocarbyl dithiophosphoric add* prepared in the first step may also be used as intermediates to prepare, for example, their sodium, potassium, magnesium, calcium, barium, nickel, copper and antimony salts, and salts of other metals as indicated above. Such salts, depending on the nature of the starting alcohol/phenol, may be used as antioxidant and/or antiwear agents for lubricants. DDPAs derived from aJkyl phenols may also, for example, be reacted with unsaturated organic compounds, for example, styrene or methyl acrylate to produce ashless additives. A process in accordance with the invention is advantageously carried out continuously, where it is appropriate to do so. Metal and ammonium salts of a dihydrocarbyl monothiophosphoric add may be prepared by reacting the acid with a metal compound or an amine. Alternatively, the metal or ammonium salts may be prepared, for example, by reacting a dihydrocarbylphosphite with a sulphur source in the presence of a metal compound or an amine. Examples of sulphur sources are elemental sulphur, sulphur halides, combinations of sulphur or sulphur oxides with hydrogen sulphide, and various sulphurized organic compounds. The preparation of dihydrocarbyl monothiophosphates is described in, for example, International Specification WO87/07638, the disclosures of which are incorporated by reference herein. Metal and ammonium salts of dihydrocarbyl phosphates may be prepared by reaction of the corresponding add with a metal compound or an amine. Dithiocarbamates may be prepared, for example, by reacting a secondary amine of the formula R 1 R 2 NH, wherein R 1 and R 2 have the meanings given above, with carbon disulphide and sodium hydroxide. The resulting sodium dithiocarbamates may then be treated, if desired, with a salt of another metal, for example, a zinc salt, to replace the sodium by the metal in question. Methods for the preparation of dithiocarbamates are well known in the art. The process of the invention may be used where any method for the preparation of any of the compounds falling within the scope of general formula (I) involves the use of reactants that are to some extent mutually insoluble, that is, reactants in different phases. SHEET The invention also provides the use of apparatus comprising a reaction region defined by a surface and at least one member adjacent to the surface, and means for causing relative movement between the surface and the member(s), for redudng sediments in a process for the manufacture of a compound of the general formula (I) given above. The invention further provides the use of apparatus comprising means for causing readants to move in a thin film over a surface, for redudng sediments in a process for the manufacture of a compound of the general formula (I) given above. In accordance with one asped of the invention, reactants in different phases are readed in a region defined by a surface and at least one member adjacent to the surface, there being relative movement between the surface and the member(s) such that the readants are caused to move relative to the surface. Advantageously, the region is defined by adjacent surfaces between which there is relative movement such that the reactants are caused to move relative to one or both of the surfaces. Because the surface and the member(s) (or, in the preferred case, the two surfaces) defining the readion region are adjacent to each other, the rea ants are readed in a thin film and are caused to move relative to the surface or, if there are two surfaces, to at least one of the surfaces. The very high mechanical forces exerted on the readants as a result of the arrangement and adion of the surface/member(s) and the surfaces result in significant improvements as described elsewhere in this specification. In a further asped of the invention, the readants are caused to move in a thin film on a surface over which they move, the average velocity (taken across the thickness of the film) of a mixture of the readants in a direction parallel to the surface being at least 1 m/sec, the thin film advantageously being formed between the surface and at least one member adjacent to the surface, preferably between adjacent surfaces, there being relative movement between the surface and the member(s), or between the surfaces, causing the said movement of the reactants. A thin film in accordance with the invention advantageously has a thickness of at most 25 mm, preferably at most 20 mm, and especially at most 15 mm. In SUBSTITUTE Si-ictT particular applications, film thicknesses in the range of from 0.1 to 10 mm, especially 0.2 to 10 mm, have been found to be espedally advantageous. Although the invention extends to arrangements where this is not the case, the film thickness is advantageously determined by the width of the gap between the surface and at least one member adjacent to the surface (and preferably, between adjacent surfaces), and the said gap advantageously has a width of at most 25 mm, preferably at most 20 mm, and especially at most 15 mm. (In accordance with the invention, therefore, the surface and the member, or two surfaces, are said to be "adjacent" if they define a readion region which advantageously has a thickness of at most 25 mm.) In particular forms of apparatus suitable for use in accordance with the invention, gaps with a width in the range of from 0.1 to 10 mm, espedally 0.2 to 10 mm, have been found to be particularly advantageous. The width of the gap need not be constant throughout the readion region. Where there is a thin film of material between a surface and at least one member adjacent to the surface (preferably between adjacent surfaces), relative movement of the surface and the member(s) or between the surfaces causes movement of the mixture of readants relative to the or a surface. In the preferred case, discussed in more detail below, where the surface, or one of the surfaces, is stationary and the member(s) or the other surface moves, the mixture will tend to move in a direction parallel to the stationary surface with an average velocity less than, but for a thin film approaching, that of the adjacent moving member/surface. Thus, for example, where the readants are readed in a thin film formed between an inner rotor and an outer stator, the mixture of readants will tend to move over the surface of the stator with an average velocity less than, but approaching, the peripheral velocity of the rotor. In accordance with the invention, the mixture advantageously moves with an average velocity (taken across the thickness of the film) of at least 1 m sec, advantageously at least 5 m/sec, and preferably at least 10 m sec, and these are preferred peripheral velodties for the rotor in arrangements where the readants are readed in a region defined by an inner body and an adjacent outer housing, one of which, preferably the inner body, . forms a rotor and the other of which forms a stator. In one particularly preferred arrangement having a central rotor and an outer stator, a peripheral speed of the rotor in the range of from 20 to 30 m/sec was found to be espedally advantageous. SUBSTITUTE SHEET In an embodiment not at present preferred, both the surface and the member(s), or both the surfaces, move. If the surface and member(s), or the two surfaces, move in opposite diredions (for example, if an inner body and an adjacent outing housing are rotated in opposite diredions) .the minimum average velocity of 1 m/sec mentioned above is the velocity relative to the surface or one of the surfaces. It will be appredated that the movement of the mixture of readants will normally have components in more than one direction. Thus, for example, in an arrangement where the readants are readed in a region defined by an inner body and an adjacent outer housing, one of which rotates, the movement of the mixture will normally have components in the axial and radial diredions as well as in the tangential diredion. In such an arrangement, the minimum average velocity of 1 m/sec referred to herein is the component of velocity in the tangential diredion. As indicated above, where the inner body and outer housing are adjacent to each other so that there is a thin film of material between them, the mixture of readants has an average velocity (taken across the thickness of the film) having a component in the tangential diredion approaching the peripheral speed of the rotor. When the readion region is defined by a surface and at least one member adjacent to the surface (and, preferably, by two adjacent surfaces), the surface and/or the member(s) (or one or both of the surfaces) may be caused to move, although it is normally preferred that the or a surface remains stationary. Any type of movement may be employed. Thus, for example, the movement may be an oscillatory movement. Advantageously, however, the member(s) or, where there are two surfaces, one of the surfaces, rotates, the, or the other, surface remaining stationary. Where the readion region is defined by a surface and at least one member adjacent to the surface, the or each member may comprise, for example, a blade extending radially outwardly from a shaft which, in use, is rotated at high speed. Such rotation will cause the readants to form a thin film on the surface and to move over the surface. There may also be at least one zone where centrifugal forces cause the readants to travel in a generally radial diredion at a considerable velocity before meeting the surface. In some cases, centrifugal forces may be sufficient to maintain on the surface a thin film whose thickness is SUBSTITUTE SHEET less than the width of the gap between the surface and the outer extremities of the blades. In the preferred case, where readion of the readants takes place in a region defined by two surfaces, the readion region may, if desired, be defined by opposing surfaces of two plates or cylinder walls, for example, discs, although this arrangement is not at present preferred. Preferably one of the plates is rotated at high speed, for example, from 500 to 10,000 rpm, depending on the diameter, while the other plate is stationary. The opposing surfaces of the plates are relatively close to each other (that is, adjacent to each other) so that only a thin film of material to be readed is present between them at any one time, the gap between the plates preferably being, for example, of the order of 0.2 to 25 mm. The plates may be, for example, discs having a diameter of up to 50 cm, although larger diameters are not excluded. Where one disc is rotated and the other is stationary, the peripheral velocity of the rotating disc is advantageously at least 1 m sec, advantageous and preferred velocities being as indicated above in connedion with a rotor/stator arrangement. In a particular preferred embodiment of the invention, the readion region is a generally annular region defined by a surface of an inner body and a surface of an outer housing, and the material in the region is caused to move by rotation of the inner body and/or the outer housing, advantageously by rotation of the inner body while the housing remains stationary. References to a "generally annular" region include not only the case where the inner body is in the form of a right circular cylinder and the inner surface of the housing is also smooth, but also the case where one or both of the opposed surfaces defining the mixing region is not smooth. Thus, for example, one or both of the surfaces may have one or more protrusions thereon or one or more depressions therein (including the cases where there is a single helical protuberance and or a single helical groove) or may be, for example, toothed or corrugated. For example, the outer housing may have a plurality of inwardly- extending protrusions thereon, the protrusions, which are preferably all of the same size and shape as one another, preferably being spaced apart at regular intervals on the inner surface of the outer housing, and the inner body (the rotor in this case) may have a plurality of outwardly extending regularly spaced projections of the same size and shape as one another. Alternatively, or in addrtion, the inner body or the housing may have one or more apertures or discontinuities (for example, slots) therein. Although in the preferred arrangements described above, the outer diameter of the inner body (or, where the inner body is not in the form of a right drαiar cylinder, the diameter of the volume swept out by the inner body if it were to rotate) and the inner diameter of the housing (or the diameter of the volume that would be enclosed in the interior of the housing if it were to rotate) are advantageously constant along the length of the rotor, one or both of the diameters may vary along the length of the gap. Thus, for example, starting from one end of the inner body and housing, the inner diameter of the housing may remain constant or decrease, while the external diameter of the inner body increases, or both said diameters may increase but at different rates, or the external diameter of the inner body may remain constant while the internal diameter of the housing decreases. In the arrangements discussed above, the inner body may be located coaxially or eccentrically with respect to the housing, but preferably the housing and inner body are radially symmetrical and coaxial. As indicated earlier, the inner body and/or the outer housing may have one or more apertures or discontinuities therein. Such apertures or discontinuities enable material to pass through the body in question in a generally radial diredion, so that, for example, readants fed to the centre of a hollow rotor can travel radially outwards to read in the gap between the rotor and stator. Further, the stator may also, or alternatively, have apertures and or discontinuities therein. Where the rotor and or stator has apertures or discontinuities, it may be possible to use more than one rotor and/or more than one stator. Thus, for example, readants may pass outwardly, in a generally radial diredion, through a first stator, a rotor, and a second stator. Apertures or discontinuities may of course be present in any body providing a surface referred to in this specification. Where such an annular body has a plurality of discontinuities in the form of slots therein, the body can, in the extreme case, be regarded as a plurality of members as discussed elsewhere in this speάfϊcation. SUBSTITUTE SHEET Where materials pass through a body providing a surface they will in general be subjeded to additional forces, for example, shearing forces, which may enhance the results obtainable in accordance with the invention. Shearing forces may be of importance in ail aspeds of the invention. An espedally advantageous reador for use in accordance with the invention comprises an outer casing having within it one or more stators, which may be interconnected with each other, and one or more rotors, which may also be interconnected with each other, such that there is at least one readion region defined by a rotor and an adjacent stator. Advantageously, the or each stator and the or each rotor in such a reador describes at (east a part of the curved wall of a right circular cylinder, the rotor(s) and stator(s) being coaxial with each other and, in the preferred case where the casing also has the general form of a right drcular cylinder, with the casing. Where there is more than one stator and/or more than one rotor, there will normally be more than one readion region according to the invention. In the last- mentioned case, it will normally be desirable for one or more of the stator(s) and rotor(s) to have apertures and/or discontinuities therein so that the readants can readily pass from one readion region to another. Thus, for example, a rotor or stator may have a plurality of circular apertures therethrough, or may comprise a circumferentially continuous portion from which a plurality of wall portions extend in a generally axial diredion to give a generally cylindrical surface with discontinuities therein. An advantageous reactor as described above may be provided with one or more inlets and outlets such that readants can be introduced in an axial diredion to the centre of the rotor/stator arrangement and, after passing radially outwards through the rotor/stator arrangement, can be withdrawn from a zone between the said arrangement and the casing, or from a zone, for example, a post-readion zone, downstream of the said zone. The rotor advantageously ads as a pump to draw readants fed axialfy into the reador to the centre of the rotor/stator arrangement, and also subjeds the readants to centrifugal forces causing them to move radially outwards through the rotor/stator arrangement. A reador of this type is very suitable for use in carrying out readions in a continuous manner. A rotor which causes or assists movement of fluids within the reador may of course be used in readors other than the especially advantageous reactor described above. For any given readion, the readion time required to give optimum results wiK depend, inter alia, on the nature of the rea ants and the reaction temperature, and can be ascertained by routine experiment. If the readion time is too tow, yields may be undesirably low, while if the readion time is too high, unwanted reactions may occur. Some readion of the reactants used in accordance with the invention may occur other than in the readion zone (the region thin film) used in accordance with the invention. Thus, for example, the reactants may be mixed before being introduced into the said region thin film, and some readion may take place at that stage, or in a post-readion zone (for example, a "soaking" zone) downstream of the readion zone used in accordance with the invention. Whether or not readion occurs elsewhere, advantageously a major part of each of the readants is treated in a reaction zone used in accordance with the invention. Preferably at least 75 mass% of each of the readants is treated in the said readion zone, especially at least 85 mass%, and particularly at least 95 mass%. In the most preferred case, substantially all of each of the readants is treated in the said readion zone. Thus the arrangements of inlet(s) and outlet(s) in any given reador, and the internal design of the reador, are preferably such that, in passing through the reador, the readants are constrained to pass through the readion zone. The invention further provides the use of apparatus comprising an outer housing and a rotor within the housing, the housing and the rotor having opposed adjacent surfaces defining a reaction region, in the preparation of compounds of general formula (I) given above, especially such compounds which are suitable for use as additives for lubricating oils, the peripheral speed of the rotor preferably being at least 1 m/sec. Lubricating oil additives 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 ail proportions. It does mean, however, that the additives 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 BSTITUTE SHEET employed. Moreover, the additional incorporation of other additives may also permit incorporation of higher levels of a particular additive, if desired. Additives prepared in accordance with the present invention can be incorporated into the oil in any convenient way. Thus, they can be added diredly to the oil by dispersing or by dissolving them in the oil at the desired level of concentration, typically with the aid of a suitable solvent such, for example, as toluene, cyclohexane, or tetrahydrofuran. Such blending can occur at room temperature or an elevated temperature. Additives prepared in accordance with the invention are particularly useful in lubricating oil compositions which employ a base oil in which the mixtures are dissolved or dispersed. Base oils with which the additives 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. Synthetic base oils include alkyl esters of dicarboxylic acids, polyglycols and alcohols; poly-α-olefins, 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 paraffmic-naphthenic, as well as to the method used in their produdion, for example, distillation range, straight run or cracked, hydrofined, solvent extraded and the like. 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 extraded oils produced, for example, by solvent extraction with solvents, for example, phenol, sulphur dioxide, furfural, dichlorodiethyl ether, nitrobenzene, or crotonaldehyde. Thθ 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 m 2 /s) and preferably about 2.5 to about 9 cSt. (about 2.5 x 10 to about 9 x 10* m 2 /s) at 100 β C. An additive 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 additive, typically in a minor proportion, for example, in a proportion as indicated below. 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 viscosity index improvers, corrosion inhibitors, oxidation inhibitors, fridion modifiers, dispersants, metal-containing detergents, anti-foaming agents, anti-wear agents, pour point depressants, and rust inhibitors. 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 viscosity 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, polymethacryfates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, inteφolymers 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 the metallic parts contaded by the lubricating oil composition. Illustrative of corrosion inhibitors are phospho-sulphurized hydrocarbons and the produds obtained by readion of a phosphosulphurized hydrocarbon with an alkaline earth metal oxide or hydroxide, preferably in the presence of an alkylated phenol or of an alkylphenol thioester, and also preferably in the presence of carbon dioxide. SUBSTITUTE SHEET Phosphosulphurized hydrocarbons may be prepared by reacting a suitable hydrocarbon, for example, a terpene, a heavy petroleum fraction of a C2 to Cβ oleftn polymer such, for example, as polyisobutylβnβ, with from 5 to 30 mass% of a sulphide of phosphorus for 1/2 to 15 hours, at a temperature in the range of about 65 to about 315°C. Neutralization of the phosphosulphurized hydrocarbon may be effected in any suitable manner, for example, in the manner taught in U.S. Patent No. 1,969,324. 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 alkaline earth metal salts or alkyl-phenolthioesters having preferably C5 to C 1 2 alkyl side chains, e.g. cateium nonylphenyl sulphide; barium octylphenyl sulphide; dioctylphenylaminβ; phenylalpha-naphthylamine; and phosphosulphurized or sulphurized hydrocarbons. Other oxidation inhibitors or antioxidants which may be used in lubricating oil compositions comprise oil-soluble copper compounds. The copper may 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 add. Examples of suitable acids include Cβ to C18 fatty acids, such, for example, as stearic or palmitic add, but unsaturated acids such, for example, as oieic add 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 1 R 2 NC(S)S] z Cu where z is 1 or 2, and R 1 and R 2 represent 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, aralkyi, alkaryl and cy oaliphatic radicals. Particularly preferred as R 1 and R 2 groups are alkyl groups having from 2 to 8 carbon atoms, for example, those listed earlier in this spedfication as T HEET preferred groups which R 1 and R 2 may represent. Copper sulphenates, phenates, and acetylacetonates may also be used. Examples of further useful copper compounds are copper Cu 1 and/or Cu" salts of alkenyl succinic acids or anhydrides. The salts themselves may be basic, neutral or addic. They may be formed by reading (a) polyalkylene sucdnimides (having polymer groups of M n of 700 to 5,000) derived from potyalkylene-poryamines, which have at least one free carboxylic add 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 of potyisobutenyl succinic anhydride, and Cu salts of polyisobutenyl succinic acid. Preferably, the copper is in its divalent form, Cu". The preferred substrates are polyalkenyl succinic adds in which the alkenyl group has a number average molecular weight greater than about 700. The alkenyl group desirably has a M n rom about 900 to 1 ,400, and up to 2,500, with a M n of about 950 being most preferred. Espedally preferred is polyisobutylene succinic anhydride or acid. These materials may desirably be dissolved in a solvent, such as 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 readion 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 succinic anhydride, Cu-oleate, or mixtures thereof) will generally be employed in an amount of from about 50 to 500 ppm by weight of the copper, in the final lubricating or fuel 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-olβate, . esters of long chain polycarboxylic acids with diols, for example, the butane diol ester of a dimerized unsaturated fatty acid, and oxazoline compounds. SUBSTITUTE SHEET Dispersants maintain oil-insoluble substances, e.g. resulting from wear or oxidation during use, in suspension in the fluid, thus preventing sludge flocculation and precipitation or deposition on metal parts. So-called ashless dispersants are organic materials which form substantially no ash on combustion, in contrast to metal-containing (and thus ash-forming) detergents. Suitable dispersants include, for example, derivatives of long chain hydrocarbon- substituted carboxylic adds 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. As indicated above, such hydrocarbon-substituted carboxylic adds may be readed 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 produds 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 diredly thereto; and Mannich condensation produds 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 having a number average molecular weight of about 700 to about 5000. As indicated above, a viscosity index improver dispersant fundions 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 readion produds of amines, for example polyamines, with a hydrocarbyl- substituted mono -or dicarboxylic add 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 C 1 0 unsaturated mono- or 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 neutralised with an UB TIT TE SHEET amine. hydroxyamine or an alcohol; or a polymer of ethylenβ with a C3 to C20 olefin further readed either by grafting a C4 to C20 unsaturated nitrogen- containing monomer thereon or by grafting an unsaturated add onto the polymer backbone and then reading carboxylic add groups of the grafted acid with an amine, hydroxy amine or alcohol. Examples of dispersants and viscosity index improver dispersants may be found in European Patent Specification No. 24146 B, the disclosure of which is incoφorated herein by reference. As indicated earlier in the specification, detergents and metal rust inhibitors include the metal salts, which may be overbased, of sulphonic acids, alkyl phenols, sulphurised alkyl phenols, alkyl salicylates, naphthenates, and other oil- soluble mono- and dicarboxylic adds. Overbased metal sulphonates wherein the metal is seleded from alkaline earth metals and magnesium are particularly suitable for use as detergents. Representative examples of detergents/rust inhibitors, and their methods of preparation, are given in European Spedfication No. 208 560 A. Antiwear agents, as their name implies, reduce wear of metal parts. The ZDDPs mentioned earlier in this specification are very widely used as antiwear agents. 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 tow temperature fluidity of the fluid are Cβ to Ciβ diaikyl 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. Additives prepared in accordance with the invention may where appropriate be used in lubricating oils other than engine oils. Some of the above-mentioned additives can provide a multiplicity of effeds; thus for example, a single additive may ad as a dispersant-oxidation inhibitor. This approach is well known and need not be further elaborated herein. SUBSTITUTE SHEET Compositions when containing the above-mentioned additives are typJcaJy blended into the base oil in amounts which are effective to provide their normal fundion. Representative effedive amounts of such additives for an automobile crankcase lubricant are: Additive Viscosity Modifier Corrosion Inhibitor Oxidation Inhibitor Dispersant Pour Point Depressant Anti-Foaming Agent Fridion Modifier Mineral or Synthetic Oil Base * Mass% adive ingredient based on the final oil. When a plurality of additives are employed it may be desirable, although not essential, to prepare additive concentrates comprising the additives (the 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 into the lubricating oil may be facilitated by solvents and by mixing accompanied with mild heating, but this is not essential. The concentrate or additive package 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 is combined with a predetermined amount of base lubricant. Thus, one or more additives can be added to small amounts of base oil or other compatible solvents along with other desirable additives to form additive packages containing adive 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. Three forms of mixing apparatus and reador suitable for use in the process of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: SUBSTITUTE SHEET Fig. 1 is a schematic longitudinal section through one form of reactor suitable for use in accordance with the invention; Fig. 2 is a cross-section through the reador shown in Fig. 1 ; Fig. 3 is a schematic vertical section through a further form of reador suitable for use in accordance with the invention; Fig. 4 is a cross-sedion through the reador shown in Fig. 3; Fig. 5 is a schematic vertical section through a modification of the reador shown in Fig. 3; and Fig. 6 is a cross-sedion through the reador shown in Fig. 5. Referring now to the drawings, the reador shown in Figs. 1 and 2 comprises a housing 1 having the general form of a right drcular cylinder, the housing being arranged with its longitudinal axis substantially horizontal. The housing, which is closed at each end, is provided at one end (the left hand end as seen in the drawings) with inlets 2,3 for readants to be treated in the reador and at the other end with an outlet 4 for produds of the readion. Within the housing, and coaxial therewith, is a shaft 5 which can be caused to rotate by drive means 6 situated outside the housing. A plurality of blades 7 extend radially outwards from the shaft, the end of each blade closer to the shaft being fixed to the shaft so that the blades rotate with the shaft. The shaft and blades thus form a rotor, which rotates relative to the housing, the housing remaining stationary during use of the reador. The outer extremities of the blades are adjacent to the inner surface of the housings, such that the said extremities and surface define a readion region or zone. The width of the readion region may be, for example, 0.2 to 10 mm. In use of the reador, the shaft is caused to rotate at high speed, for example, 10,000 rpm. Such rotation causes readants introduced through the inlets to form a thin film on the inner wall of the housing, readion between the readants taking place in this thin film. Material within the housing travels along the inner surface of SUBSTITUTE SHEET the housing until it reaches the outlet, through which it is removed for any further processing that may be necessary. Because a thin film is formed on the inner wall of the housing, the readants are treated in accordance with the process of the invention. A further advantage of readors in which the reactants are readed in a thin film on an outer housing is that the temperature of the materials forming the film can be controlled by supplying heat to, or withdrawing it from, the housing. Figs. 3 and 4 show a reador suitable for use in accordance with the invention. The reador shown is particularly suitable for use when working on a laboratory scale, but may readily be adapted for larger scale operation. The reador comprises a casing 11 in the form of a right drcular cylinder, the axis of the casing extending substantially vertically. The top and bottom of the casing are closed, the bottom being provided with inlets 12 and 13 for readants and the top being provided with an outlet 14 for material that has passed through the reador. When working on a large scale, it may be advantageous to use an arrangement in which the axis of the casing extends generally horizontally, as in Figs. 1 and 2. Within the casing, and coaxial therewith, is a shaft 15, supported by a bearing, which can be caused to rotate by drive means (not shown) situated outside the casing. Attached to the lower end of the shaft is a rotor comprising a rotor disc 16 with an upwardly extending peripheral rotor flange 17. The disc is mounted on the shaft for rotational movement therewith, the shaft, disc and rotor flange thus forming a rotor. The disc is provided with three generally triangular apertures 18 therein, and the rotor flange has a plurality of drcumferential openings 19 therein (most clearly seen in Fig. 4). Also mounted in the casing is a stator comprising a stator disc 20 of larger diameter than the rotor disc 16, and two downwardly extending, circumferentially discontinuous, stator flanges 21 and 22, each of the said flanges being coaxial with the rotor flange, which extends upwardly between the two stator flanges. Each of the stator flanges comprises a plurality of wall portions 24 extending downwardly from the stator disc such that there are openings 25 between the wall portions. As will be most clearly seen in Fig. 4, the outer surface of the rotor flange SUBSTITUTE SHEET is adjacent to the inner surface of the outer stator flange 21 , and the inner surface of the rotor flange is adjacent to the outer surface of the Inner stator flange 22, so that the rotor and stator define two annular reaction regions, indicated by the reference numerals 26 and 27, in accordance with the invention. The outer drcumferential wall of the reador shown in Figs. 3 and 4 may if desired be provided with a heating/cooling jacket (not shown). In use of the reactor shown in Figs. 3 and 4, the shaft 15 is rotated and the readants are introduced through the inlets 12 and 13. The pumping adion of the rotor causes the readants to be drawn through the apertures 18 in the rotor disc 16 and thus into the central region of the rotor/stator arrangement. The readants are then forced by the rotor to travel outwards in a generally radial diredion, such that they pass through the inner stator flange, the rotor flange, and the outer stator flange to the zone 28 between the outer stator flange and the casing. In passing, through the rotor and stator flanges, the reactants read in the annular readion regions 26 and 27. Material in the zone 28 passes upwardly through the casing (the upper part of the casing may, if desired, be used as a post-reaction zone), and removed via the outlet 14. Figs. 5 and 6 show a modification of the reactor shown in Figs. 3 and 4. In the reactor shown in Figs. 5 and 6, the reador also includes two opposed radially extending blades 30, each of which has a downwardly extending portion 31 providing a surface 32 adjacent to the inner surface of the inner stator flange 22. As shown in Figs. 5 and 6, the blades 30 and the rotor disc 16 are both mounted on the same shaft, but if desired they could be mounted on different shafts, one extending through the top of the reador, and one extending through the bottom. Although the arrangement shown in Figs. 5 and 6 has one rotor flange and two stator flanges, arrangements with additional rotor and stator flanges may be used if desired, thus increasing the number of readion regions in accordance with the invention. Thus, for example, in some circumstances an arrangement with two upwardly extending rotor flanges and three downwardly extending stator flanges has been found to be advantageous. SUBSTITUTE SHEET ln the reador shown in Figs. 5 and 6, the apertures 18 shown in Figs. 3 and 4 are replaced by a plurality of drcular apertures 33. The following Examples illustrate the invention. In the Examples, the reador used in accordance with the invention was substantially as described with reference to Figs. 5 and 6 of the accompanying drawings, and had the following characteristics: Diameter of volume swept by rotor = 40.5 mm Gap between rotor and each stator = 0.5 mm Speed of rotation of rotor = 10,000 φm Example 1 A slurry of phosphorus pentasulphide (P2S5) (phosphorus content of 27.6 mass% and 4.8 mass% of free sulphur) and a mixture of C 4 and C5 primary alcohols (35 mass% isobutanol, 25 mass% pentanol and 40 mass% 3-methyM -butanol) was fed continuously to the reactor through a coarse tube peristaltic pump at a flow rate of 10 g/min. 4.2 moles of alcohol were used for each mole of P2S5. The mixture in the reactor was maintained at a temperature of approximately 85°C and the residence time in the readion region of the reador defined as: Residence time = volume of readion region flow rate of readants was approximately 5 minutes. A DDPA of constant quality and containing 11.8 mass% phosphorus and 0.01% sediments was obtained. Hydrogen sulphide, one mole of which was produced for each mole of P2S5 used, was removed from the system and scrubbed in a caustic medium. The rate of produdion of the DDPA was 600 g h. SUBSTITUTE SHEET Example 2 The process was earned out as described in Example 1 , but with the reactants continuously circulating through a system wherein the reador used in accordance with the invention was coupled with a standard stirred tank reactor. After continuous circulation for 50 mins at 85°C a DPPA of constant quality having a phosphorus content of 11.9 mass% and containing less than 0.01% sediment was obtained. The rate of produdion of the DDPA was approximately 60 g h. Example 3 The procedure described in Example 1 was repeated replacing the alcohol mixture used in Example 1 with a mixture of C3 and Cβ secondary alcohols (35 mass% isopropanol and 65 mass 0 /© methyl isobutyl carbinol) having an average molecular weight of 86.3, and maintaining the mixture in the reador at approximately 80°C. A DDPA of constant quality and containing 11.3 mass% P and 0.01% sediment was obtained. Example 4 The process was carried out as in Example 3, but with the readants continuously drculating through a system as described in Example 2. After continuous drculation of 50 mins at 80°C, a DDPA of constant quality having a phosphorus content of 11.3 mass% and less than 0.01 mass% sediment was obtained. Comparative Example 1 50 g of the readion mixture used in Example 1 were charged into a discontinuous stirred tank reactor. After 4 hours a DDPA with 0.01 mass% sediment and a phosphorus content of 11.8 mass% was obtained. The rate of produdion of the DDPA was 12.5 g/h, as compared with a rate of 600 g/h for a 0.01% sediment produd in Example 1 and 60 g/h for a <0.01% sediment produd in Example 2. Example 5 A slurry of ZnO in base oil (35.4 mass% ZnO based on the slurry) and a DDPA derived from a mixture of C4 and C5 primary alcohols and containing 12.0 mass% SUBSTITUTE SHEET P were fed separately to the reador, where the readants were maintained at a temperature of 70°C. The DDPA was fed at a rate of 28.5 g/min and the ZnO slurry at a rate of 13 g/min. A raw ZDDP containing 0.25 mass% sediment and having a pH of 5 and a hydrolytic stability of greater than 60 mins was obtained. After filtration, a bright and dear produd with a Zn P ratio of 1.07, a basicity of 63 mg HCI/g, a Zn content of 8.59 mass% and a P content of 8.02 mass% was obtained. Example 6 A DDPA as used in Example 5 was readed with ZnO slurried in base oil (ZnO content 36.2 mass%, based on the slurry). The ZnO slurry was continuously drculated through the reador used in accordance with the invention, which was maintained at 88 °C, and a normal stirred tank reactor, which was maintained at 85°C, while the DDPA was fed separately to the reador used according to the . invention. An amount of DDPA corresponding to a Zn/P ratio of 1.08 was charged over a period of 30 minutes. After all the DDPA had been added, the mixture was drculated through the system for 50 minutes. A raw ZDDP with 0.01 mass% sediment, a pH of 5.0 and hydrolytic stability of greater than 60 minutes was obtained. The ZDDP did not require filtration and, after nitrogen stripping at 80°C, was clear (40 NTU haze) as compared with raw ZDDP. The produd had a Zn/P ratio of 1.08, a basidty of 29 mg HClg, a Zn content of 8.59 mass% and a P content of 7.98 mass%. Example 7 A slurry of ZnO in base oil (35.5 mass% of ZnO based on the slurry) and a DDPA derived from a mixture of sec-butyl alcohol and iso-odyl alcohol (85/15 by mass) and containing 11.8% P were fed separately to the reador, where the readants were maintained at a temperature of 75°C. The DDPA was fed at a rate of 26.5 g/min and the ZnO slurry at a rate of 14.5 g/min. A raw ZDDP containing 1.0 mass% sediment and having a pH of 4.8 and a hydrolytic stability of 10 minutes was obtained. The raw ZDDP was transferred to a stirred tank reador and maintained at 75°C for 60 minutes. A stable produd was obtained containing 0.2% sediment and having SUBSTITUTE SHEET a pH of 5.9. This produd was filtered to yield a final produd having a Zn/P ratio of 1.10:1 , a basicity of 55 mg HCI/g, a Zn content of 8.71% and a P content of 7.95%. Example 8 A system as described in Example 6 was used, both readers being maintained at a temperature of 85°C. 2.5 mass% of the zinc was added as Zn acetate. The DDPA was the same as that used in Example 7, and an amount of the DDPA corresponding to a Zn/P ratio of 1.11:1 was introduced in 40 mins. After all the DDPA had been added, the mixture was circulated through the system for 30 minutes. The procedure was repeated under the same conditions, but without the use of the promoter (that is, the zinc acetate). The data obtained are summarised as follows: With Promoter Without Promoter It will be seen that in this particular case higher stability and much tower sediments were obtained when a promoter was used. In addition, the use of the promoter made it possible to add the DDPA over a shorter period. When a promoter was used, a filtered produd with a Zn/P ratio which is substantially the same as that in the material charged to the reador was obtained. Example 9 The procedure described in Example 8 was repeated, using the same promoter as in Example 8. The ZnO slurry used had a ZnO content of 45 mass%, and the DDPA was based on 2-ethylhexyl alcohol, and had a P content of 8.4 mass%. SUBSTITUTE SHEET The produd had a pH of 5.8, a sediment level of 0.01 mass%, a stability of greater than 60 minutes, a Zn P ratio of 1.09:1 , and a basidty (mg HCI/g) of 63. TUTE SHEET

Claims: A process for the manufadure of a compound of the general formula wherein A represents an -0-P-O- or an >N-C group; each of X 1 and X 2 , which may be the same or different, represents O or S; each of R 1 and R 2 , which may be the same or different, represents a hydrocarbyl radical, M represents H, a metal ion, or an ammonium group; and n represents an integer equal to the valency of M, with the proviso that, when A represents an _>N-C group, both X 1 and X 2 represent S, in which process a first readant is present in a different phase from a second readant and the said readants are readed in a region defined by a surface and at least one member adjacent to the surface, there being relative movement between the surface and the member(s) such that the reactants are caused to move relative to the surface. 2. A process as claimed in claim 1 , wherein the region is defined by adjacent surfaces between which there is relative movement such that the readants are caused to move relative to one or both of the surfaces. 3. A process for the manufadure of a compound of the general formula SUBSTITUTE SHEET whβrein A represents an -0-P-O- or an =* -C Qroup.' each of X 1 and X 2 , which may be the same or different, represents 0 or S; each of R 1 and R 2 , which may be the same or different, represents a hydrocarbyl radical, M represents H, a metal ion, or an ammonium group; and n represents an integer equal to the valency of M, with the proviso that, when A represents an ^--=N-C group, both X 1 and X 2 represent S, in which process a first readant is present in a different phase from a second readant and the readants are readed in a thin film on a surface over which they move, the average velodty (taken across the thickness of the film) of a mixture of the readants in a direction parallel to the surface being at least 1 m/sec. 4. A process as claimed in claim 3, wherein the thin film is formed between the surface and at least one member adjacent to the surface, there being relative movement between the surface and the member(s). 5. A process as claimed in claim 3, wherein the thin film is formed between adjacent surfaces between which there is relative movement. 6. A process as claimed in any one of claims 1 , 2, 4 and 5, wherein the surface and the member(s), or the two surfaces, are separated by a distance of 0.1 to 10 mm. 7. A process as claimed in any one of claims 2, 5 and* 6, wherein one of the surfaces is a surface of an inner body and the other surface is a surface of an outer housing, one of the inner body and the outer housing being a rotor, and the other being a stator. 8. A process as claimed in claim 7, wherein the inner body is a rotor and, in use, has a peripheral speed of 20 to 30 m/sec. 9. A process as claimed in claim 7 or claim 8, wherein the inner body and/or the outer body has one or more apertures or discontinuities therein. 10. A process as claimed in any one of claims 7 to 9, wherein apparatus comprising a plurality of rotors and/or stators is used. SUBSTITUTE SHEET 11. A process as claimed in any one of claims 7 to 10, wherein the rotor(s) and stator(s) form part of a reador which is provided with one or more inlets and one or more outlets, and the rotor(s), stator(s), inlet(s) and outlet(s) are so arranged that the readants can be introduced in an axial direction to the centre of the rotor/stator arrangement and can pass radially through at least one rotor or stator before leaving the reador. 12. A process as claimed in any one of claims 1 to 11 , which is carried out in a continuous manner. 13. A process as claimed in claims 1 to 12, wherein at least 75% of each of the readants is treated in a readion region as specified in claim 1 or a thin film as specified in claim 3. 14. A process as claimed in any one of claims 1 to 13, in which the readants and or readion produd(s) are also subjeded to a soaking step. 15. A process as claimed in any one of claims 1 to 14, wherein the compound has the general formula [(R 1 0)(R 0)P(S)(0)]ή M"*, wherein R 1 , R 2 , M and n have the meanings given in claim 1. 16. A process as claimed in any one of claims 1 to 14, wherein the compound has the general formula [(R 1 0)(R 2 0)P(S)S]ή M n+ , wherein R 1 , R 2 , M and n have the meanings given in claim 1. 17. A process as claimed in any one of claims 1 to 14, wherein the compound has the general formula [R 1 R 2 NC(S)S]n M"+ f wherein R 1 , R2, M and n have the meanings given in claim 1. 18. A process as claimed in any one of claims 1 to 17, wherein the total number of carbon atoms in R and R 2 is sufficient to impart oil-solubility to the compound. 19. A process as claimed in any one of daims 1 to 18, wherein M represents a Group la metal, a Group Ha metal, aluminium, tin, lead, molybdenum, titanium, manganese, cobalt, nickel, copper, cadmium, antimony, or zinc. SUBSTITUTE SHEET 20. A process as claimed in claim 19, wherein M represents zinc or copper. 21. A process as claimed in any one of claims 1 to 20, wherein each of the first and second readants, independently, is present in the readion mixture as a liquid or solid. 22. A compound as defined in claim 1 , whenever prepared by a process as claimed in any one of claims 1 to 21. 23. The use of apparatus comprising an outer housing and a rotor within the housing, the housing and the rotor having opposed adjacent surfaces defining a readion region, in the preparation of a compound as defined in claim 1. 24. The use of apparatus comprising a readion region defined by a surface and at least one member adjacent to the surface, and means for causing relative movement between the surface and the member(s), for redudng sediments in a process for the manufacture of a compound of the general formula given in claim 1. 25. The use of apparatus comprising means for causing readants to move in a thin film over a surface, for redudng sediments in a process for the manufadure of a compound of the general formula given in daim 1. SUBSTITUTE SHEET

Inventors: BARINI GERALDO, CHIERICI ENRICO, D ANTONIO CARMINE, GUSI STEFANO, LOMBARDI ALESSANDRO, BARINI, GERALDO, CHIERICI, ENRICO, D'ANTONIO, CARMINE, GUSI, STEFANO, LOMBARDI, ALESSANDRO
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1992
Main classification: B01F7
IPC codes: B01F7, C07C333, C07F9, C10M135, C10M137, C10N10, C10N40, C10N70