Process for the preparation of phosphosulfide compounds useful as oil lubricants

Abstract

Useful as additive for lubricating oils are novel phosphosulphur compounds in accordance with the general formula (I):(((R.sup.1 --S.sub.x --O.sub.y --A--).sub.r B.sub.v).sub.p P(X)--Y.sub.i --).sub.q Z.sub.min which e.g. R.sup.1 represents an alkyl or alkenyl group, A represents the group --(CH.sub.2).sub.n --O--, B represents the group --P(S)--S--CH.sub.2 --(CH.sub.3)--O--, X represents an oxygen atom or a sulphur atom, Y represents an oxygen atom, a sulphur atom or an oxygen or sulphur-containing hydrocarbon chain, Z represents a hydrogen, chlorine or sulphur atom, a polysulphide chain, a metal or an alkyl or alkenyl group, x=1,2 or 3, y=0, 1 or 2, v is 0 or 1, r is 1 (if v=0) or r=2 (if v=1), p=2 or 3, t=0 or 1, m=0,1 or 2, q=the valency of Z if Z is a metal or q=1 or 2 and n is an integer from 1 to 30.

Description

BACKGROUND OF THE INVENTION

The present invention relates to novel phosphosulphur compounds (i.e. sulphur and phosphor-containing) and their use as petroleum additives, particularly as antioxidant, antiwear, extreme-pressure and anticorrosive additives for lubricating oils.

Antiwear and extreme-pressure additives have been used for decades particularly in engine oils, transmission fluids and hydraulic fluids. Numerous additive types have been developed and several of them have made it possible to very significantly reduce deterioration to mechanisms and therefore extend their life.

Among the antiwear and extreme-pressure additives the most active and therefore the most significantly industrially developed have been dialkyl and diaryl dithiophosphates and metallic dialkyl dithiocarbamates, (particularly those of zinc), alkyl thiophosphates, tricresyl phosphate, didodecyl phosphate, sulphurized terpenes, sulphur-containing spermaceti oil and various chlorine compounds. Certain of them are described in U.S. Pat. Nos. 2,364,283, 2,364,284, 2,365,938, 2,410,650, 2,438,876, 3,190,833. These are generally compounds containing heteroatoms such as sulphur and phosphorus, either alone (e.g. tricresyl phosphate, sulphur-containing terpenes and dithiocarbamates) or in combination (e.g. metallic dialkyl dithiophosphates and alkyl thiophosphates). Reference can be made to French Patents FR-A-982 719 and 1 321 821 and U.S. Pat. Nos. 2,750,342 and 3,944,495.

The phosphosulphur compounds used previously have relative sulphur and phosphorus quantities which are imposed by the stoichiometry of the reactions during their synthesis and which in particular give them antiwear and extreme-pressure properties, which cannot be modified by the Expert.

SUMMARY OF THE INVENTION

Novel phosphosulphur compounds have now been discovered, which can be used as lubricating additives, preferably prepared by the reaction of conventional phosphor-containing reagents with (poly)sulphurized alcohols, which makes it possible to modify at random the relative antiwear and extreme-pressure performances of said phosphosulphur compounds.

The phosphosulphur compounds according to the invention are in accordance with the general formula (I):

(((R.sup.1 --S.sub.x --O.sub.y --A--).sub.r B.sub.v --).sub.p P(X)--Y.sub.t --).sub.q Z.sub.m in which R.sup.1 represents an alkyl group (e.g. methyl, ethyl or tert. butyl) or alkenyl group (e.g. CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --), which may or may not be functionalized, containing 1 to 30 carbon atoms; A represents the group --(CH.sub.2).sub.n --O-- or the group ##STR1## in which n is an integer from 1 to 30 and R.sup.2 and R.sup.3, which can be the same or different, each represent a hydrogen atom or a substantially hydrocarbonated monovalent radical with 1 to 30 carbon atoms (e.g. methyl, ethyl, etc.), R.sup.2 and R.sup.3 can be interlinked to form a polymethylene chain and in general A represents the group --(CH.sub.2).sub.n --O--; B represents the group ##STR2## in which R.sup.4 and R.sup.5, which can be the same or different, in each case represent a hydrogen atom or a substantially hydrocarbonated monovalent radical with 1 to 30 carbon atoms and R.sup.4 and R.sup.5 can be interlinked to form a polymethylene chain; e.g. R.sup.4 =H and R.sup.5 =H or CH.sub.3 ; X represents an oxygen atom or a sulphur atom; Y represents an oxygen atom, a sulphur atom or a sulphur or oxygen-containing hydrocarbon chain; Z represents a hydrogen atom, a chlorine atom, a sulphur atom, a polysulphurized chain, a metal chosen e.g. from among the group formed by sodium, zinc, copper, molybdenum, lead, antimony and cadmium, an oxygen or sulphur-containing derivative of molydbenum or an alkyl, alkenyl or R.sup.6 group, which may or may not be functionalized, containing 1 to 30 carbon atoms; x is an integer equal to or greater than 1 and preferably equal to 1,2 or 3: y is equal to 0,1 or 2 and if y=0 then (R.sup.1 --S.sub.x --O.sub.y --A--).sub.r is written (R.sup.1 --S.sub.x --A--).sub.r ; v is equal to 0 or 1 (if v=0 there is then no B group in the formula of compounds according to the invention); r is equal to 1 if v=0 and r is equal to 2 if v=1; p is equal to 2 or 3; t is equal to 0 or 1 (if t=0 then there is no Y group in the formula of compounds according to the invention); m is equal to 0 or 1 (if m=0 then there is no Z group in the formula of compounds according to the invention); and q is an integer equal to the valency of Z if Z is a metal or a number equal to 1 or 2.

In the definition of R.sup.1 and R.sup.6, the term functionalized group is understood to mean a group containing at least one heteroatom such as e.g. chlorine or sulphur, or at least one chemical function e.g. chosen from among the carboxylic, aldehyde, ketone, nitrile, hydroxyl and epoxide functions, whereby several of these functions can be present in the same R.sup.1 and R.sup.6 group.

The different types of phosphosulphur compounds according to the invention are preferably as follows (the term (poly)sulphurized means that the compound is either monosulphurized (x=1) or polysulphurized (x>1)):

polysulphurized dialkyl dithiophosphoric and dialkenyl dithiophosphoric acids of general formula (II):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--SH --SH i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O, X=S, Y=S, Z=H, y=0, v=0, r=1, p=2, t=1, q=1 and m=1; morevover in formula (II) x is a number equal to or greater than 2 and as examples of compounds of formula (II) reference can be made to those for which R.sup.1 =tert. butyl, x=2, n=2,3,4,5 or 6 and preferably n=2,3 or 6 and R.sup.1 =CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=2, n=2,3,4,5 or 6 and preferably n=3;

(poly)sulphurized alcohols of general formula (III): ##STR3## in which R.sup.7 and R.sup.8, which can be the same or different, in each case represent a hydrogen atom or a substantially hydrocarbon-containing monovalent radical with 1 to 30 carbon atoms and R.sup.7 and R.sup.8 can be interlinked to form a polymethylene chain; formula (III) corresponding to general formula (I) in which A=--(CH.sub.2).sub.n --O, X=S, Y=S, ##STR4## y=0, v=0, r=1, p=2, t=1, q=1, m=1; moreover, in formula (III), x is a number equal to or greater than 1; examples of compounds of formula (III) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x--1 or 2, n=2,3,4,5 or 6, R.sup.7 =H and R.sup.8 =H or CH.sub.3 ; the polysulphurized metal salts of general formula (IV):

((R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--S--).sub.q Z in which Z is a metal and q is a number equal to the valency of Z, i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, Y=S, Z is a metal (e.g. zinc) y=0, v=0, r=1, p=2, t=1, q=valency of Z and m=1; moreover, in formula (IV), x is a number equal to or greater than 2, e.g. examples of compounds of formula (IV) are those for which R=tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=2, n=2,3,4,5 or 6, Z=Zn and q=2;

(poly)sulphurized dihydrocarbyldithiophosphyldithiophosphoric acids and corresponding poly(sulphurized) metal salts of general formula (V): ##STR5## in which Z=H or a metal (e.g. zinc), i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, Y=S, Z=H or a metal, y=0, v=1, r=2, p=2, t=1, q=1 (if Z=H) or q is the valency of Z (if Z is a metal) and m=1; moreover, in formula (V), x is a number equal to or greater than 1; examples of compounds of formula (V) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H, R.sup.5 =H or CH.sub.3, Z=Zn (and q=2) or Z=H (and q=1);

(poly)sulphurized organic compounds of general formula (VI):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--S--R.sup.6 i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, Y=S, Z=R.sup.6, y=0, v=0, r=1, p=2, t=1, q=1 and m=1; moreover, in formula (VI), x is a number equal to or greater than 1 and R.sup.6 is the monovalent radical of an alcohol R.sup.6 --OH; examples of compounds of formula (VI) are those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6 and R.sup.6 =(CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --CH.sub.2 --;

(poly)sulphurized organic compounds of general formula (VII): ##STR6## i.e. of general formula (I), in which A=--(CH.sub.2).sub.n --O--, X=S, Y=S, Z=R.sup.6, y=0, v=1, r=2, p=2, t=1, q=1 and m=1; moreover, in formula (VII), x is a number equal to or greater than 1; examples of compounds of formula (VII) being those for which R=tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H, R.sup.5 =H or CH.sub.3 and R.sup.6 =(CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --CH.sub.2 --;

polysulphurized dialkylphosphoric and dialkenylphosphoric acids and the corresponding polysulphurized metal salts of general formula (VIII):

((R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(O)--O--).sub.q Z in which Z=H or a metal (e.g. zinc), i.e. of general formula (I), in which A=--(CH.sub.2).sub.n --O--, X=O, Y=O, Z=H or a metal, y=0, v=0, r=1, p=2, t=1, q=1 (if Z=H) or q is the valency of Z (if Z is a metal) and m=1; moreover, in formula (VIII) x is a number equal to or greater than 2 and examples of compounds of formula (VII) are those for which R.sup.1 =tert. butyl or CH.sub.2 --C(CH.sub.3)--CH.sub.2 --, x=2, n=2,3,4,5 or 6, Z=Zn (and q=2) or Z=H (and q=1);

(poly)sulphurized dihydrocarbyldithiophosphylphosphoric acids and the corresponding (poly)sulphurized metal salts of general formula (IX): ##STR7## in which Z=H or a metal (e.g. zinc), i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=O, Y=O, Z=H or a metal, y=0, v=1, r=2, p=2, t=1, q=1 (if Z=H) or q is the valency of Z (if Z is a metal) and m=1; moreover, in formula (IX), x is a number equal to or greater than 1; examples of compounds of formula (IX) are those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1, n=2,3,4,5 or 6, R.sup.4 =H, R.sup.5 =H or CH.sub.3, Z=Zn (and q=2) or Z=H (and q=1);

polysulphurized dialkylchlorophosphates and dialkenylchlorophosphates of general formula (X):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(O)--Cl i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=O, Z=Cl, y=0, v=0, r=1, p=2, t=0, q=1 and m=1; moreover, in formula (X), x is a number equal to or greater than 2; examples of compounds of formula (X) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=2, n=2,3,4,5 or 6 and preferably n=3 or 6;

(poly)sulphurized dialkylchlorothiophosphates and dialkenylchlorothiophosphates of general formula (XI):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(S)--Cl i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, Z=Cl, y=0, v=0, r=1, p=2, t=0, q=1 and m=1; moreover, in formula (XI), x is a number equal to or greater than 1; examples of compounds of formula (XI) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,5 or 6 and preferably n=3 or 6;

(poly)sulphurized organic compounds of general formula (XII): ##STR8## i.e. of formula (I) in which A=--(CH.sub.2).sub.n --O--, X=O, Z=Cl, y=0, v=1, r=2, p=2, t=0, q=1 and m=1; moreover, in formula (XII), x is a number equal to or greater than 1; examples of compounds of formula (XII) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H and R.sup.5 =H or CH.sub.3 ;

(poly)sulphurized organic compounds of general formula (XIII): ##STR9## i.e. of formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, Z=Cl, y=0, v=1, r=2, p=2, t=0, q=1 and m=1; moreover, in formula (XIII), x is a number equal to or greater than 1; examples of compounds of formula (XIII) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H and R.sup.5 =H or CH.sub.3 ;

(poly)sulphurized trialkylphosphates and trialkenylphosphates of general formula (XIV):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.3 P(O) in which x is a number equal to or greater than 1, i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=O, y=0, v=0, r=1, p=3, t=0, q=1 and m=0; examples of compounds of formula (XIV) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2 and n=2,3,4,5 or 6;

(poly)sulphurized organic compounds of general formula (XV): ##STR10## in which x is a number equal to or greater than 1, i.e. of formula (I) in which A=--(CH.sub.2).sub.n --O--, x=0, y=0, v=1, r=2, p=3, t=0, q=1 and m=0; examples of compounds of formula (XV) being those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H and R.sup.5 =H or CH.sub.3 ;

(poly)sulphurized trialkyl thiophosphates or trialkenyl thiophosphates of general formula (XVI):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.3 P(S) in which x is a number equal to or greater than 1, i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, y=0, v=0, r=1, p=3, t=0, q=1 and m=0; and examples of compounds of formula (XVI) are those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2 and n=2,3,4,5 or 6;

(poly)sulphurized organic compounds of general formula (XVII): ##STR11## in which x is a number equal to or greater than 1, i.e. of formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, y=0, v=1, r=2, p=3, t=0, q=1 and m=0; examples of compounds of formula (XVII) are those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H and R.sup.5 =H or CH.sub.3 ;

(poly)sulphurized dialkyl phosphonates or dialkenylphosphonates of general formula (XVIII):

(R.sup.1 --S.sub.x --(CH.sub.2).sub.n --O--).sub.2 P(O)--H in which x is a number equal to or greater than 1, i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=O, Z=H, y=0, v=0, r=1, p=2, t=0, q=1 and m=1; and examples of compounds of formula (XVIII) are those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6;

(poly)sulphurized organic compounds of general formula (XIX): ##STR12## in which x is a number equal to or greater than 1, i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=O, Z=H, y=0, v=1, r=2, p=2, t=0, q=1 and m=1; and examples of compounds of formula (XIX) are those for which R.sup.1 =tert. butyl or CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2 --, x=1 or 2, n=2,3,4,5 or 6, R.sup.4 =H and R.sup.5 =H or CH.sub.3 ;

and (poly)sulphurized organic compounds of general formula (XX): ##STR13## in which x is a number equal to or greater than 1 and n is a number equal to or greater than 3, i.e. of general formula (I) in which A=--(CH.sub.2).sub.n --O--, X=S, ##STR14## R.sup.7 and R.sup.8 being defined as hereinbefore, Z=S.sub.w, w being a number equal to or greater than 1, y=0, v=0, r=1, p=2, t=1, q=1 and m=1; and examples of compounds of formula (XX) are those for which R.sup.1 =CH.sub.3, C.sub.2 H.sub.5 --, (CH.sub.3).sub.3 C-- and CH.sub.2 .dbd.C(CH.sub.3)--CH.sub.2, x=1,2 or 3, n=3,4,5 or 6, R.sup.7 =H, R.sup.8 =H or CH.sub.3 and w=1,2,3, or 4; and more specifically the compounds having the following formulas (with tBu=tert. butyl):

((tBu--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S ((tBu--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.2 ((tBu--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.3 ((tBu--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S ((tBu--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.2 ((tBu--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2).sub.2 S.sub.3.

Processes for the preparation of the phosphosulphur compounds according to the invention are illustrated in the examples. More particularly due to their good antioxidant, anticorrosive and in particular antiwear and extreme-pressure properties, each phosphosulphur compound according to the invention can advantageously be used as an additive for in particular mineral and/or synthetic lubricating oils at a concentration of 0.05 to 5% by weight.

Therefore the present invention relates to a lubricating composition incorporating a major proportion of lubricating oil and 0.05 to 5% by weight of at least one phosphosulphur compound according to the invention.

The following examples illustrate the invention without limiting its scope.

EXAMPLE 1

Synthesis of a Monosulphurized Dialkyldithiophosphoric Acid (Known Product)

In a first stage, 3000 cm.sup.3 of pure ethyl alcohol are introduced into a 6000 cm.sup.3 three-necked reactor, followed by 372 g (9.3 mole) of sodium hydroxide. After dissolving, the mixture is heated to 50.degree. C. and progressive addition takes place of 837.6 g (9.3 mole) of 2-methyl-propane-2-thiol. At the end of addition, the temperature is kept at 50.degree. C. for a further 30 minutes, followed by cooling to 20.degree. C. This is followed by the progressive introduction of 878.8 g (9.3 mole) of n-chloropropanol. The mixture is brought to the reflux of the alcohol for 6 hours and then cooled to ambient temperature.

The NaCl formed is eliminated by filtration and the organic solution acidified by a 2N HCl aqueous solution. The organic phase is collected and then the aqueous phase extracted by dichloromethane. The organic fractions are combined, washed with water, dried on anhydrous Na.sub.2 SO.sub.4 and the dichloromethane is eliminated by evaporation under reduced pressure.

The product is purified by distillation under reduced pressure (PE=84.degree. C./1 mnbar), which makes it possible to obtain 1370 g of a colourless product with the following elementary analysis:

______________________________________wt. % C wt % H wt. % SFound Theory Found Theory Found Theory(Fd) (Th) (Fd) (Th) (Fd) (Th)______________________________________56.81 56.73 10.79 10.81 21.84 21.66______________________________________

The expected chemical structure is confirmed by .sup.13 C NMR analysis, namely:

(CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --OH (monosulphurized alcohol).

In a second stage 189.6 g (1.28 mole) of previously prepared monosulphurized alcohol and 400 cm.sup.3 chloroform are introduced into a 2000 cm.sup.3 three-necked reactor. The mixture is heated to 60.degree. C., followed by the progressive addition of 71.12 g (0.32 mole) of P.sub.2 S.sub.5. After completely dissolving the P.sub.2 S.sub.5, the mixture is kept for an additional hour at 60.degree. C. and accompanied by stirring. After eliminating the chloroform under reduced pressure, 240 g of a pale yellow liquid are collected, which has the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd. Th. Fd. Th. Fd. Th. Fd. Th.______________________________________43.21 43.05 7.97 7.94 32.71 32.86 8.02 7.94______________________________________

.sup.13 C NMR analysis confirms the expected chemical structure, i.e.:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O).sub.2 P(S)--SH

EXAMPLE 2

Synthesis of a Monosulphurized Zinc Dialkyldithiophosphate (Known Product)

Part of the previously obtained sulphurized dialkythiophosphoric acid (30 g, i.e. 0.077 mole) is transformed into sodium salt by adding to it 100 cm.sup.3 of an aqueous sodium solution (NaOH=3.2 g, i.e. 0.08 mole). This sodium salt is purified by successive extractions with hexane and then the recovered purified aqueous solution is treated with a solution of 12.66 g (0.045 mole) of 7H.sub.2 O ZnSO.sub.4 dissolved in 30 cm.sup.3 of water. The sulphurized zinc dialkyldithiophosphate then precipitates immediately. The mixture is extracted with chloroform, the organic phase recovered is dried on anhydrous Na.sub.2 SO.sub.4 and then the solvent is eliminated by evaporating under reduced pressure. In this way 20.3 g of a viscous yellow liquid are collected, which is in accordance with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % P wt. % ZnFd. Th. Fd. Th. Fd. Th. Fd. Th. Fd. Th.______________________________________40.11 39.81 7.26 7.11 30.69 30.40 7.24 7.35 7.82 7.75______________________________________

Moreover, the infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure of the zinc salt, i.e.:

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S).sub.2 Zn

EXAMPLE 3

Synthesis of a Monosulphurized Dialkyldithiophosphoric Alcohol

Part of the sulphurized dialkyldithiophosphoric acid obtained in Example 1 (60 g, i.e. 0.154 mole) is introduced into a 250 cm.sup.3 three-necked reactor, followed by the progressive addition of 10 g (0.172 mole) of epoxypropane, whilst not exceeding a reaction temperature of 30.degree. C. After evaporating the excess epoxy propane under reduced pressure, 66 g of pale yellow liquid are recovered and the elementary analysis is as follows:

______________________________________wt. % C wt. % H wt. % S wt. % PFd. Th. Fd. Th. Fd. Th. Fd. Th.______________________________________45.75 45.51 8.57 8.26 29.12 28.61 6.92 6.92______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--OH

EXAMPLE 4

Synthesis of a Monosulphurized Zinc Dialkyldithiophosphyldithiophosphate

Into a 250 cm.sup.3 three-necked reactor equipped with a Dean-Stark separator, are introduced 1.7 g (0.016 mole) of sodium carbonate and 100 cm.sup.3 of benzene. The mixture is refluxed for 1 hour to make the medium anhydrous, followed by the addition of 3.66 g (0.0165 mole) of P.sub.2 S.sub.5. This is followed by the progressive introduction of 29.6 g (0.066 mole) of monosulphurized dialkyldithiophosphoric alcohol prepared in Example 3. The mixture is then refluxed and kept there for 3 hours.

This is followed by cooling to 50.degree. C. and the addition of 20 cm.sup.3 of ethyl alcohol containing 0.4 g (0.01 mole) of sodium hydroxide. Reaction is allowed to take place for 1 hour. Filtration takes place to eliminate the P.sub.2 S.sub.5 in excess. This is followed by the addition of 50 cm.sup.3 of an aqueous solution containing 10 g of 7H.sub.2 O ZnSO.sub.4 (0.0356 mole) and reaction is allowed to take place for 2 hours, accompanied by vigorous stirring. This is followed by drying on Na.sub.2 SO.sub.4, filtering and evaporation of the benzene under reduced pressure. A pale viscous yellow liquid is recovered, which has the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % P wt. % ZnFd Th Fd Th Fd Th Fd Th Fd Th______________________________________40.01 39.91 7.27 7.04 30.89 31.36 8.95 9.10 3.06 3.20______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(S)--S--).sub.2 Zn

EXAMPLE 5

Synthesis of a Monosulphurized Dialkyldithiophosphoric Acid Triester

In a first stage, 30 g (0.2 mole) of monosulphurized alcohol prepared in Example 1 are dissolved in 60 cm.sup.3 of chloroform, followed by the progressive addition of 11.9 g of SOCl.sub.2 (0.1 mole). The mixture is then refluxed, followed by the progressive addition of 11.94 g of SOCl.sub.2 (0.1 mole), followed by the maintenance of reflux for a further 2 hours. After cooling, the chloroform is eliminated by evaporation and the chlorine derivative corresponding to the monosulphurized alcohol is purified by distillation under reduced presdure (PE=92.degree. C./1 mmbar), which gives 31.5 g of product (0.189 mole).

In a second stage, 27.3 g (0.07 mole) of monosulphurized dialkyldithiophosphoric acid prepared in Example 1 are transformed into sodium salt in the manner indicated in Example 2. The aqueous purified sodium salt solution is then mixed with 1 g of tetrabutyl ammonium hydrogen sulphate (phase transfer catalyst), followed by the addition of 11.42 g (0.07 mole) of the halogen-containing derivative of the preceding first stage dissolved in 10 cm.sup.3 of dichloromethane. The mixture is refluxed for 10 hours, cooled, the recovered organic phase washed with water, dried on Na.sub.2 SO.sub.4, filtered and then evaporated under reduced pressure. In this way 35 g of product are recovered with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd. Th. Fd. Th. Fd. Th. Fd. Th.______________________________________48.78 48.43 8.57 8.65 31.02 30.81 6.04 5.96______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--S--C--(CH.sub.3).sub.3

EXAMPLE 6

Synthesis of Monosulphurized Dialklychlorophosphates

Example 6.1 (known product)

Into a 500 cm.sup.3 three-necked reactor are introduced 16 g (0.104 mole) of POCl.sub.3 dissolved in 50 cm.sup.3 of benzene. This is followed by the progessive addition of a solution constituted by 30.8 g (0.208 mole) of monosulphurized alcohol prepared in Example 1, 16 g of pyridine and 50 cm.sup.3 of benzene. The mixture obtained is stirred at ambient temperature for one hour. The pyridinium chloride obtained is eliminated by filtration, the organic phase washed with water, dried on Na.sub.2 SO.sub.4 and evaporated under reduced pressure. This gives 38 g of product with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % P wt. % ClFd Th Fd Th Fd Th Fd Th Fd Th______________________________________44.89 44.61 8.02 7.97 17.44 17.03 8.11 8.23 9.65 9.43______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--Cl

Example 6.2: (novel product)

The same experiment performed on the basis of the monosulphurized thiophosphorus alcohol prepared in Example 3 leads to a product corresponding to the following formula:

(((CH.sub.3).sub.3 C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(O)--Cl

EXAMPLE 7

Synthesis of Monosulphurized Zinc Dialkylphosphates

Example 7.1 (known product)

In a first stage vigorous stirring takes place of 18 g (0.048 mole) of the first monosulphurized dialkylchlorophosphate obtained in Example 6 with 50 cm.sup.3 of an aqueous 2N sodium solution for 2 hours, followed by the extraction of the mixture with toluene. The recovered aqueous phase is acidified with 2N hydrochloric acid, extracted with toluene, washed with water, dried on Na.sub.2 SO.sub.4, filtered and then evaporated under reduced pressure. This gives 15 g of a yellow liquid with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________47.21 46.91 8.87 8.66 17.45 17.91 8.44 8.66______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the chemical structure of the expected monosulphurized dialkylphosphoric acid, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--OH

In a second stage neutralization takes place of 15 g (0.042 mole) of monosulphurized dialkylphosphoric acid prepared in the preceding first stage with 2.35 g of potassium dissolved in 50 cm.sup.3 of methyl alcohol. Stirring is maintained for 30 minutes at ambient temperature, followed by the addition of 12.7 g (0.045 mole) of 7H.sub.2 O ZnSO.sub.4 dissolved in 25 cm.sup.3 of water. The mixture is stirred for 30 minutes at ambient temperature, followed by extraction with ethyl alcohol. The recovered organic phase is washed with water, dried on Na.sub.2 SO.sub.4, filtered and then evaporated under reduced pressure. This gives 15 g of a very viscous, opalescent liquid with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % P wt. % ZnFd Th Fd Th Fd Th Fd Th Fd Th______________________________________43.52 43.10 7.55 7.70 16.26 16.45 8.14 7.95 8.11 8.39______________________________________

The infrared, .sup.31 P and .sup.-- C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--)--).sub.2 Zn

Example 7.2 (novel product)

The same experiment carried out on the basis of the chlorine derivative of the monosulphurized thiophosphorus alcohol prepared in Example 3 (cf. Example 6.1) leads to a product corresponding to the following formula:

((((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(O)--O--).sub.2 Zn

EXAMPLE 8

Synthesis of Monosulphurized Trialkylphosphates

Example 8.1 (Known Product)

10 g (0.065 mole) of POCl.sub.3 are dissolved in 50 cm.sup.3 of benzene. The mixture is cooled to 5.degree. C., followed by the progressive addition of a solution of 28.9 g (0.195 mole) of the monosulphurized alcohol prepared in Example 1, 30 g of puridine and 50 cm.sup.3 of benzene, whilst maintaining the reaction temperature at 5.degree. C. Following addition, this temperature is maintained for a further 30 minutes. This is followed by heating to the reflux of the solvent and boiling is maintained for 2 hours. The solution is cooled, filtered, the organic phase washed water, dried on Na.sub.2 SO.sub.4, filtered and evaporated under reduced pressure. This gives 27 g of product with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________51.87 51.62 9.54 9.22 19.22 19.70 6.11 6.35______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.3 P(O)

Example 8.2

The same experiment performed on the basis of the monosulphurized thiophosphorus alcohol prepared in Example 3 leads to a product corresponding to the following formula:

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.3 P(O)

EXAMPLE 9

Synthesis of Monosulphurized Trialkylthiophosphates

Example 9.1

The experiment of Example 8.1 is repeated substituting the POCl.sub.3 by the same molar quantity of PSCl.sub.3. After reaction and treatments, 24 g of product are collected with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________50.12 49.97 9.01 8.92 25.12 25.43 6.11 6.15______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.3 P(S)

Example 9.2

The same experiment performed on the basis of the monosulphurized thiophosphorus alcohol prepared in Example 3 leads to a product corresponding to the following formula:

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.3 P(S)

EXAMPLE 10

Synthesis of Monosulphurized Dialkylphosphonates

Example 10.1

30 g (0.18 mole) of monosulphurized alcohol prepared in Example 1 are dissolved in 100 cm.sup.3 of carbon tetrachloride. Then, at ambient temperature, progressive addition takes place of 8.25 g (0.06 mole) of PCl.sub.3 dissolved in 50 cm.sup.3 of carbon tetrachloride. Boiling takes place and this temperature is maintained for 1 hour. The solvent is eliminated by evaporating under reduced pressure and the dialkylphosphonate is separated from the halogen-containing derivative by liquid silica column chromatography. This gives 18 g of product with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________49.32 49.08 9.21 9.06 18.62 18.74 8.95 9.06______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(O)--H

Example 10.2

The same experiment, carried out on the basis of the monosulphurized thiophosphorus alcohol prepared in Example 3, leads to a product corresponding to the following formula:

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(O)--H

These experiments (or syntheses) can be repeated using polysulphurized alcohols (x>1). In this way it is possible to regulate at random the sulphur quantity contained in the additives according to the invention and therefore obtain products having regulatable antiwear and extreme-pressure properties. The following examples illustrate these possibilities.

EXAMPLE 11

Synthesis of a Polysulphurized Alcohol

Into a 500 cm.sup.3 three-necked reactor are introduced 200 cm.sup.3 of methyl alcohol and then 44 g (1.1 mole) of sodium hydroxide. After dissolving, the mixture is heated to 50.degree. C., followed by the progressive addition of 99 g (1.1 mole) of 2-methyl-2-propane-thiol. At the end of addition, the temperature is maintained at 50.degree. C. for a further 30 minutes. This is followed by the progressive addition of 33.2 g (1.1 gramme atom) of elementary sulphur, then reaction is allowed to take place at 50.degree. C. until the sulphur is completely dissolved. This is followed by the progressive introduction of 92.5 g (1 mole) of n-chloropropanol. The mixture is heated to the reflux of the alcohol for 6 hours and then cooled to ambient temperature.

The NaCl formed is eliminated by filtration and the organic solution evaporated under reduced pressure. The organic phase is washed with water to eliminate the toluene-extracted sodium polysulphide excess, dried on Na.sub.2 SO.sub.4 and evaporated under reduced pressure. The crude polysulphurized alcohol obtained is purified by liquid chromatography on silica, whilst eluting the impurities with hexane (tert. butyl polysulphides), the desired product then being recovered by eluting with methyl alcohol. After evaporating the methyl alcohol, in this way 173 g of polysulphurized tert. butyl alcohol are recovered with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % SFd Th Fd Th Fd Th______________________________________46.87 46.63 8.92 8.88 35.24 35.60______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely a statistical mixture of sulphurized alcohols of the following summary formula:

(CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --OH

EXAMPLE 12

Synthesis of a Polysulphurized Dialkyldithiophosphoric Acid

Into a 1000 cm.sup.3 three-necked reactor are introduced 150 g (0.83 mole) of polysulphurized alcohol prepared in Example 11 and 400 cm.sup.3 of chloroform. The mixture is heated to 60.degree. C., followed by the progressive addition of 46.11 g (0.207 mole) of P.sub.2 S.sub.5. After complete dissolving of the P.sub.2 S.sub.5, the mixture is kept for an additional hour at 60.degree. C., accompanied by stirring. After eliminating the chloroform under reduced pressure, 185 g of pale yellow liquid are collected with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________37.12 36.97 6.92 6.82 42.11 42.34 6.71 6.82______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure, namely:

((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--SH

EXAMPLE 13

Synthesis of a Polysulphurized Dialkyldithiophosphoric Alcohol

100 g of polysulphurized dialkyldithiophosphoric acid obtained in Example 12 (0.22 mole) are introduced into a 500 cm.sup.3 three-necked reactor, followed by the progressive addition of 15 g (0.26 mole) of epoxy propane, whilst not exceeding a reaction temperature of 30.degree. C. After reducing the excess epoxy propane under reduced pressure, 112 g of pale yellow liquid are recovered with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________39.94 39.81 7.35 7.22 37.32 37.55 6.01 6.05______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure of the alcohol, namely:

((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2)--CH(CH.sub.3)--OH

EXAMPLE 14

Synthesis of Polysulphurized Zinc Dialkyldithiophosphate

The experiments of Examples 1 and 2 are repeated with the polysulphurized alcohol prepared in Example 11. Following the reactions and separation, a polysulphurized zinc dialkyldithiophosphate with the following elementary analysis is obtained:

______________________________________wt. % C wt. % H wt. % S wt. % P wt. % ZnFd Th Fd Th Fd Th Fd Th Fd Th______________________________________34.82 34.56 6.37 6.17 39.21 39.58 6.14 6.38 6.46 6.73______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure of the product, namely:

(((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S).sub.2 Zn

EXAMPLE 15

Synthesis of a Polysulphurized Zinc Dialkyldithiophosphyl Dithiophosphate

The experiment of Example 4 is repeated with the polysulphurized dialkyldithiophosphoric alcohol prepared in Example 13. Following reactions and separation, a polysulphurized zinc dialkyldithiophosphyl dithiophosphate is obtained with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % P wt. % ZnFd Th Fd Th Fd Th Fd Th Fd Th______________________________________35.58 35.46 6.46 6.26 38.67 39.01 7.95 8.08 2.64 2.84______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses confirm the chemical structure of the product, namely:

((((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH(CH.sub.3)--O--).sub.2 P(S)--S--).sub.2 Zn

Evaluation of the Extreme-pressure and Antiwear Properties of the Additives According to the Invention

Tests are carried out to reveal the antiwear and extreme-pressure properties of the additives according to the invention in lubricating formulations of the gear oil type.

The additives of Examples 2,3,4,5,8.1,9.1,10.1,11,14 and 15 were studied with the aid of a machine with four balls according to the procedure of ASTM D 2783 at concentrations such that the sulphur content of the mineral-based oil SAE 80W90 is equal to or close to 0.2% by weight. The results obtained are given in Table 1.

It can in particular be seen that the functional additives according to the invention have good antiwear and extreme-pressure properties, which can be modified as a function of the sulphur quantity used in the syntheses. It can also be seen that for the same sulphur concentration the polysulphide-type additives (in this case x=2) generally have better performance characteristics than the monosulphide-type additives (x=1), which gives the possibility of regulating at random the mechanical performance characteristics of these products, as a function of the value chosen for x (1,2,3 etc). This improvement can be advantageously used in the formulation of lubricating oils, especially for gears.

TABLE 1__________________________________________________________________________ Wear Additive Extreme-Pressure Impression diameter (mm)S quantity quantity S quantity Wear load Load before 1 h under load ofAdditive in additive in oil in oil value seizing Welding load 40 kgf 60 kgf 80 kgfof Example wt. % wt. % wt. % kgf Newt kgf Newt kgf Newt 392.4 Newt 588.6 784.8__________________________________________________________________________ Newt-- -- -- -- 28.0 274.7 50 490.5 150 1471.5 1.47 1.90 2.502 30.69 0.652 0.2 36.0 353.2 80 784.8 200 1962.0 0.36 0.68 0.9814 39.21 0.510 0.2 55.4 543.5 126 1236.1 250 2452.5 0.33 0.60 0.874 30.89 0.647 0.2 42.9 420.8 100 981.0 200 1962.0 0.45 0.66 0.9815 38.67 0.517 0.2 47.0 461.1 100 981.0 250 2452.5 0.37 0.65 0.903 29.12 0.755 0.22 34.9 342.4 80 784.8 200 1962.0 0.35 0.52 1.105 31.02 0.709 0.22 33.8 331.6 80 784.8 200 1962.0 0.36 0.55 1.078.1 19.22 1.116 0.22 35.9 352.2 80 784.8 200 1962.0 0.39 0.67 0.939.1 25.12 0.875 0.22 42.9 420.8 100 981.0 250 2452.5 0.37 0;61 0.9010.1 18.62 1.182 0.22 50.6 496.4 126 1236.1 200 1962.0 0.42 0.48 1.2011 35.24 0.624 0.22 37.2 364.9 80 784.8 200 1962.0 0.39 0.54 1.09__________________________________________________________________________

EXAMPLE 16

Synthesis of the Compound

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S

a. First stage, preparation of the monosulphurized alcohol:

(CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --OH

150 cm.sup.3 of pure ethyl alcohol are introduced into a 500 cm.sup.3 three-necked reactor, followed by 18.6 g (0.465 g-mole) of sodium hydroxide. After dissolving, the mixture is heated to 50.degree. C., followed by the progressive addition of 41.9 g (0.465 g-mole) of 2-methyl-2-propane thiol. At the end of addition, the temperature is kept at 50.degree. C. for a further 30 minutes, followed by cooling to 20.degree. C. This is followed by the progressive addition of 43.95 g (0.465 g-mole) of n-chloropropanol, the mixture then being heated to the reflux of alcohol for 6 hours, followed by cooling to ambient temperature.

The NaCl formed is eliminated by filtration and the organic solution acidified by a 2N HCl aqueous solution. The organic phase is collected and then the aqueous phase extracted by dichloromethane. The organic fractions are combined, washed with water, dried on anhydrous Na.sub.2 SO.sub.4 and the dichloromethane is eliminated by evaporation under reduced pressure.

The purification of the sulphur-containing alcohol takes place by distillation under reduced pressure (PE=84.degree. C./1 mbar). 68.5 g of colourless product are recovered with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % SFd Th Fd Th Fd Th______________________________________56.81 56.73 10.79 10.81 21.84 21.66______________________________________

The infrared, .sup.1 H and .sup.13 C NMR analyses confirm the chemical structure of the product.

b. Second stage, preparation of a monosulphurized dialkyldithiophosphoric acid:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--SH

Into a 250 cm.sup.3 reactor are introduced 19.0 g (0.128 g-mole) of monosulphurized alcohol prepared in the first stage and 40 cm.sup.3 of chloroform. The mixture is heated to 60.degree. C., followed by the progressive addition of 7.11 g (0.032 g-mole) of P.sub.2 S.sub.5. After complete dissolving, the mixture is kept for an additional hour at 60.degree. C. and accompanied by stirring. After eliminating the chloroform under reduced pressure, 24 g of a pale yellow liquid are obtained with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________43.21 43.05 7.97 7.94 32.71 32.86 8.02 7.94______________________________________

The infrared, .sup.1 H and .sup.13 C analyses confirm the expected chemical structure of the product.

c. Third stage, preparation of a monosulphurized dialkyldithiophosphoric alcohol:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --OH

Into a 100 cm.sup.3 reactor are introduced 22.0 g (0.0564 g-mole) of sulphur-containing dialkyldithiophosphoric acid prepared in the preceding stage, followed by the addition of 2.8 g (0.064 g-mole) of ethylene oxide, accompanied by stirring and whilst vigorously cooling in order to maintain a temperature of 25.degree. C. The ethylene oxide excess is eliminated by evaporation under reduced pressure and 24 g of a viscous liquid are collected having the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________44.09 44.22 8.12 8.06 29.32 29.53 7.03 7.14______________________________________

The infrared, .sup.1 H, .sup.31 P and .sup.13 C NMR analyses confirm the expected chemical structure of the product.

Fourth stage, preparation of the chloride corresponding to the preceding monosulphurized dialkyldithiophosphoric alcohol:

((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --Cl

Into a 100 cm.sup.3 reactor are introduced 20.0 g (0.046 g-mole) of monosulphurized dialkyldithiophosphoric alcohol prepared in the preceding stage, followed by the addition of 20 g of chloroform and then very progressively 2.74 g (0.023 g-mole) of SOCl.sub.2, whilst maintaining the reaction temperature at about 20.degree. C. The mixture is then refluxed and then very progressive addition again takes place of the same SOCl.sub.2 quantity. After cooling, the chloroform is eliminated under reduced pressure in order to collect approximately 20 g of product, whose infrared, .sup.31 P, .sup.1 H and .sup.13 C NMR analyses correspond to the expected chemical structure of the product.

Fifth and final stage, preparation of the sought compound:

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S

Into the reactor of the preceding stage are introduced 20 g of chloroform in order to dissolve the chlorine-containing derivative followed by 1 g of tetrabutyl ammonium chloride (phase transfer catalyst) and finally very progressive 20 cm.sup.3 of an aqueous solution containing 7 g of 9H.sub.2 O Na.sub.2 S (0.03 g-mole) whilst maintaining the temperature at about 20.degree. C. The mixture is then refluxed for 1 hour, cooled and the phases separated. The recovered organic fraction is washed with water, dried on anhydrous NaSO.sub.4 and then filtered to collect 19 g of product with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________44.89 44.31 7.99 7.85 32.47 33.30 7.01 7.15______________________________________

The infrared, .sup.1 H, .sup.31 P and .sup.13 C NMR analyses confirm the chemical structure of the product.

EXAMPLE 17

Synthesis of the Compound

(((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S

The first stage (a) of Example 16 is repeated, whilst adding to the reaction mixture 14.91 g (0.465 g-mole) of elementary sulphur in order to statistically form the disulphurized compound. After reaction, the crude disulphurized alcohol obtained is purified by liquid chromatography on silica gel, followed by elution with hexane in order to eliminate the impurities and with methyl alcohol which, after evaporation under reduced pressure, makes possible to recover the sought purified, disulphurized alcohol. The experiment is continued using the same molar proportions of reagents in order to obtain after the fifth stage (e) a product with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________38.97 38.60 7.05 6.84 41.02 41.90 6.01 6.23______________________________________

The infrared, .sup.31 P and .sup.13 C NMR analyses correspond to the expected chemical structure of the product.

EXAMPLE 18

Synthesis of the Compound

(((CH.sub.3).sub.3 --C--S--(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S.sub.2

The experiment of Example 16 is integrally repeated up to the fifth stage, where use is made of 25 cm.sup.3 of an aqueous solution containing 7 g of 9H.sub.2 O Na.sub.2 S (0.03 g-mole) and 1 g of elementary sulphur (0.03 g-atom) for statistically forming the disulphurized compound. This gives a product with the following elementary analysis:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________43.22 42.73 7.85 7.57 34.89 35.68 6.73 6.90______________________________________

The infrared, .sup.31 P, .sup.1 H and .sup.13 C NMR analyses correspond to the chemical structure of the statistically expected product.

EXAMPLE 19

Synthesis of the Compound

(((CH.sub.3).sub.3 --C--S.sub.2 --(CH.sub.2).sub.3 --O--).sub.2 P(S)--S--CH.sub.2 --CH.sub.2 --).sub.2 S.sub.3

The experiment of Example 17 is repeated in order to prepare the sulphur-containing disulphurized dialkyldithiophosphorus alcohol. The experiment is continued, all molar proportions between the reagents being maintained, up to the fifth stage where use is made of 25 cm.sup.3 of an aqueous solution constituted by 7 g of 9H.sub.2 O Na.sub.2 S (0.03 g-mole) and 2 g of elementary sulphur (0.06 g-atom) in order to form the statistically sought trisulphurized compound. A product with the following elementary analysis is obtained:

______________________________________wt. % C wt. % H wt. % S wt. % PFd Th Fd Th Fd Th Fd Th______________________________________36.86 36.26 6.78 6.42 44.71 45.42 5.34 5.85______________________________________

The infrared, .sup.31 P, .sup.1 H and .sup.13 C NMR analyses correspond to the chemical structure of the statistically expected product.

Evaluation of the Extreme-pressure and Antiwear Properties of the Additives of Examples 16 to 19

Tests are carried out to reveal the extreme-pressure and antiwear properties of the additives according to the invention using a machine with four balls according to the procedure of ASTM D 2783, under concentrations such that the sulphur content of the mineral oil SAE 80W90 is equal to 0.22% by weight. The results obtained are given in Table 2.

These results show that the additives according to the invention have good antiwear and extreme-pressure properties and that these can be modified as a function of the elementary sulphur quantity used in the syntheses. It is in particular shown that for an equal sulphur concentration, the compounds having polysulphide units are more effective than those having monosulphide units, which gives a possibility of regulating at random the mechanical performance characteristics of these products. This improvement can be used with advantage in the formulation of lubricating oils for gears or for the working of metals.

TABLE 1__________________________________________________________________________ Wear Additive Extreme-Pressure Impression diameter (mm)S quantity quantity S quantity Wear load Load before 1 h under load ofAdditive in additive in oil in oil value welding Welding load 40 kgf 60 kgf 80 kgfof Example wt. % wt. % wt. % kgf Newt kgf Newt kgf Newt 392.4 Newt 588.6 784.8__________________________________________________________________________ Newt-- -- 0 -- 28.0 274.7 50 490.5 150 1471.5 1.47 1.90 2.5016 32.47 0.68 0.22 33.8 331.6 80 784.8 200 1962.0 0.40 0.58 1.0717 41.02 0.54 0.22 43&0 421.8 100 981.0 200 1962.0 0.39 0.55 0.9818 34.89 0.63 0.22 36.0 353.2 80 784.8 200 1962.0 0.39 0.65 0.9519 44.71 0.49 0.22 55.1 540.5 126 1236.1 250 2452.5 0.35 0.60 0.89__________________________________________________________________________

Claims

1. A process for preparing an alcohol of the formula

R.sup.1 --Sx--(CH.sub.2).sub.n --OH

wherein

R.sup.1 is an alkyl or alkenyl group with 4 carbon atoms,

x is 2, 3 or 4, and

n is at least 3,

comprising reacting a R.sup.1 --SH thiol with a haloalkanol of the formula

Hal--(CH.sub.2).sub.n OH,

in which Hal is a halogen atom, with the addition of elemental sulfur, in the presence of alkali and in an alcoholic medium.

2. A process according to claim 1, wherein x is 2 and n is 3.

3. A process according to claim 1, comprising reacting 2-methyl-propane-2-thiol-with elemental sulfur and with 3-chloropropanol, to produce (CH.sub.3).sub.3 C--S.sub.2 --(CH.sub.2).sub.3 --OH.

4. A process according to claim 1, wherein R.sup.1 is tert-butyl or methallyl, x is 2, 3 or 4 and n is 3 or 4.

5. A process according to claim 4, wherein x=2 and n=3.