GB2193957A

GB2193957A - Extreme pressure (EP) aromatic oniphide lubricating oil additive and process for preparing same

Info

Publication number: GB2193957A
Application number: GB08617993A
Authority: GB
Inventors: Rezso Csikos; Sandor Borzsonyi; Peter L Farkas
Original assignee: Magyar Asvanyolaj es Foldgaz Kiserleti Intezet
Current assignee: Magyar Asvanyolaj es Foldgaz Kiserleti Intezet
Priority date: 1986-07-28
Filing date: 1986-07-23
Publication date: 1988-02-24
Also published as: NL8601966A; FR2602786A1; GB8617993D0; JPS6343997A; CH672487A5; FR2602786B1; BE905179A

Abstract

Extreme pressure (EP) additives of the general formula (R<I-V>-Arb)c(Sx)d, wherein R<I>, R<II>, R<III>, R<IV> and R<V> are the same or different and each represents a hydrogen atom, a C1-40 straight or branched chain or cyclic, saturated or unsaturated hydrocarbyl group or a derivative thereof; Ar stands for a monocyclic or polycyclic aromatic hydrocarbyl group or a derivative thereof; b means a number from 1 to 5; c means a number from 2 to 10; d means a number from 1 to 9; and x means a number from 1 to 6, are useful for the preparation of auxiliary materials for lubricating and hydraulic oils, lubricating greases as well as for metal-working coolant and lubricating fluids.

Description

SPECIFICATION Extreme pressure (EP) lubricating oil additive and process for preparing same This invention relates to an extreme pressure (EP) lubricating oil additive with a high sulfur content, useful for the production of auxiliary materials for lubricating and hydraulic oils, lubricating greases as well as for metal-working coolant and lubricating fluids.

According to an other aspect of the invention, there is provided a process for the preparation of these additives.

For preserving vehicles, engines, industrial equipment, hydraulic systems as well as tools and equipment in metal-working processes, for diminishing the wear (attrition) and for a more economical operating, lubricating materials are at present prepared with an EP additive of 0. 1 to 20% by mass. These compounds containing in general sulfur, chlorine, phosphorus or nitrogen go into chemical reactions with the metals resulting in a superficial protective layer which inhibits the formation of local welded microbonds caused by heat flashes of high temperature appearing as a consequence of high loads between metal surfaces moving on each other. The splitting of these microbonds gives rise to the development of superficial pitting or striation.In addition to the wear-resistant properties, other important characteristics such as lubricating capacity, heat stability as well as protective action against oxidation and corrosion of the lubricating materials should also be considered. These are taken into account by adding compounds with a combined effect, on the one hand, and additive compositions, on the other hand.

A high number of processes for preparing EP additives have been reported in the literature, especially in patent specifications involving EP additives. These processes can be divided to three well-distinguishable groups.

(1) The reaction of alkanols, esters, alkylphenol derivatives, olefines and/or of hydrocarbons containing sulfur, chlorine or nitrogen as heteroatoms with the sulfur compounds of phosphorus, e.g. with P4Sao: Processes of such type are described e.g. in the East-German patent specifications Nos.

117,248, 101,695 and 79,093, in the United States patent specification No. 4,058,468 as well as in the Hungarian patent specification No. 180,272. Though the EP effect of the thus-prepared additives containing mainly sulfur and phosphorus is weak, their additional action is yet advantageous with a preferable antioxidant and corrosion-inhibiting effect.

(2) The reaction of alkenes containing one or more unsaturated bonds, aromatic and/or alkylaromatic hydrocarbons, hydrocarbons containing sulfur, chlorine, nitrogen or phosphorus as heteroatoms and esters with the chlorine compounds of sulfur (e.g. with SCI2, S2Cl2, SOCI2 or R-S-CI): In some cases, the reaction product is subjected to a post-treatment with an alkaline metal hydroxide, sodium mercaptide or sodium sulfide in order to eliminate the residual chlorine content.

Processes of such type have been described in the United States patent specifications Nos.

4,198,305, 4,097,387, 3,925,414, 3,844,964 and 3,873,454 as well as in the French patent specification No. 2,404,042. These processes are used for the preparation of EP additives with medium or high sulfur content and containing in general also other heteroatoms.

(3) The reaction of olefines containing one or more unsaturated bonds, esters, hydrocarbons containing heteroatoms with elementary sulfur or with the mixture of elementary sulfur and hydrogen sulfide in the presence of or without a catalyst: The direct sulfuration of isobutylene or C3 8 olefines is most frequently used. Processes of such type have been reported in the French patent specification No. 2,434,864, in the United States patent specifications Nos, 3,926,822, 3,899,475, 4,119,550 and 4,119,545 as well as in the German patent specification No. 2,838,981. These processes are useful for the preparation of additives with a high EP effect containing 5 to 50% of sulfur,.The drawbacks of this method of preparation consist in the relatively high pressure (100 bar), in the relatively high temperatures (150 to 200"C) as well as in a high amount of harmful side-products causing environmental pollution.

In the course of our investigations concerning the preparation of EP additives, it has been found that organic polysulfide EP additives of the general formula (R ~Arb)c(sx)dx wherein Rl, R", R"', RIV and RV are the same or different and each represents a hydrogen atom, a C, 40 straight or branched chain or cyclic, saturated or unsaturated hydrocarbyl group or a derivative thereof; Ar stands for a monocyclic or polycyclic aromatic hydrocarbyl group or a derivative thereof; b means a number from 1 to 5; c means a number from 2 to 10; d means a number from 1 to 9; and x means a number from 1 to 6, with a high sulfur content and higher effectivity can be prepared in a much simpler way and with lower expenditures by chloromethylating an alkylaromatic compound of the general formula R'-V-Arb, wherein Rl, R", R"', RlVt RV, Ar and b are the same as defined above, with a formaldehyde solution and/or with paraformaldehyde together with an aqueous solution of hydrochloric acid and/or gaseous hydrogen chloride in the presence or without a catalyst and then reacting the thus-obtained arylalkyl chloride with sodium polysulfide.

Based on the results of the extended technological and effectivity studies, it can be stated that the characteristics of the above organic polysulfides such as the solubility in lubricating oils and organic solvents, the compatibility with other additives and the tribological properties are decisively influenced by the composition of the intermediate prepared in the chloromethylating step.

Namely, no uniform product is here formed, but di- and eventually polysubstituted compounds are also obtained, in addition to the monosubstituted product, in the course of reactions following each other. This process is illustrated by the reaction schemes A and B.

As a consequence of the reaction rules of alkylaromatic hydrocarbons as well as of the reaction-hindering effect of the -CH2Cl group bound to the aromatic ring, the reaction rate of the introduction of a second chloromethyl group is lower whereas the probability of entering of a third chloromethyl group is negligible in most cases.

In Fig. 1, the change in the composition of a product prepared by chloromethylating a xylene isomeric mixture at 350C and at 50 C is shown as the function of the change in the total chlorine content of the product. On the horizontal axis of the diagram, the chlorine content (as % by mass), on the left vertical axis the composition (as % by mass), whereas on the right vertical axis the monochloro/dichloro ratio are plotted.

It is clearly seen from the diagram that, by the increase in the chlorine content, the amount of the dichloror compounds containing two chloromethyl groups (curves II) is significantly enhanced in addition to the monochloro products (curves I).The monochloro/dichloro ratio is diminished by the increase in the chlorine content (curves Ill) and the value of this ratio is lower when the reaction is carried out at a higher temperature.

In the first step of preparing the additive, there exists a possibility to adjust the appropriate monochloro/dichloro ratio by suitable selection of the temperature of the chloromethylation, the xylene/hydrochloric acid/formaldehyde molar ratio and the chlorine content.

In the polysulfide forming reaction, a product consisting of the mixture of dimers and trimers, eventually tetramers is obtained as a result of binding through the Sx groups. These reactions are shown in the reaction schemes C, D and E.

The reaction shown in the reaction scheme E is only significant when the content of dichloro compounds is high. However, the quantity of the monochloro compounds is a manyfold of the dichloro compounds in the course of the additive production; thus, the amount of the tetramers and the oligomers obtained in the polysulfide forming reaction is negligible. Similarly, the amount of the substances arising from the trichloro and polychloro products and having a very complicated composition can also be neglected.

In Fig. 2 the change in the composition of the organic polysulfide is illustrated as a function of the monochloro/dichloro ratio of the chloromethylated alkylarene hydrocarbons. On the horizontal axis of the diagram the monochloro/dichloro ratios, whereas on the vertical axis the composition (as % by mass) are plotted. The data given for the xylene starting substance were determined by calculation.

It is obvious from the diagram that the amount of the dimers (I) rapidly diminishes by a decrease in the monochloro/dichloro ratio, whereas the quantity of the trimers (II) is intensely increased. The product contains trimers in a quantity of about 12% even in the case when the amount of the monchloro substances is a twentyfold of the dichloro substances, whereas the proportion of the trimers in the product amounts to 50% when the monochloro/dichloro ratio is 4:1.

From the view-point of preparing the sulfur-containing EP additive, the ratio of the dimers to the trimers in the composition of the organic polysulfide is of decisive importance. As a consequence of their higher hydrocarbon content, the solubility of the dimers in apolar solvents and lubricating oils is higher; thus, the solubility and compatibility of the product with other additives is improved by the increase in the dimer content of the polysulfides. Consequently, the polysulfides having a high trimer (eventually tetramer) content are unsuitable for preparing EP additive compositions. This problem appears particularly in the course of mixture formation with thiophosphonates and succinimides prepared from a high molecular mass polyisobutylene and being essential components of the EP additive mixture compositions.

According to our recognition, an indispensable requirement of preparing an organic polysulfide also useful for the production of an EP additive composition is that the monochloro content of the chloromethylated intermediate should be at least seven times as high as the dichloro content thereof. When an isomeric xylene mixture is used as starting material, this demand can safely achieved by using a chloromethylating reaction performed at a temperature of 350C until a chlorine content of 14% is reached. A lower chlorine content is uneconomical because of a high amount of the unreacted xylene. The reaction period is significantly increased by extremely low temperatures.

A similarly preferably composition can be achieved by using a chloromethylating reaction at a higher temperature but with a lower molar ratio of paraformaldehyde. On carrying out the chloromethylation of xylene e.g. at 800C until reaching a chlorine content of 12 to 14% and on using a 4:0.6:1 molar ratio of hydrochloric acid/paraformaldehyde/xylene, the threshold value represented by the at least 7:1 monochloro/dichloro ratio is similarly accomplished. In addition, the time of the reaction is also significantly decreased as a consequence of the higher temperature.

An organic polysulfide which can be used as an EP additive for lubricating and hydraulic oils, lubricating greases as well as for metal-working auxiliary materials and can be mixed with several more polar additives, can be prepared in an appropriate quality when the monochloro content of the chloromethylated intermediate is at least three times as high as the dichloro content thereof.

When an isomeric xylene mixture is used as starting material, this demand can safely be accomplished by using a chloromethylating reaction carried out at a temperature of at most 500C until achieving a chlorine content of 17.5%.

When the monochloro/dichloro ratio in the chloromethylated intermediate is lower than 3:1, then the solubility of the organic polysulfide prepared therefrom is not suitable, the product is not uniform and possibly it separates to several phases. In the case of such a low monochloro/dichloro ratio, oligomers and polymers of higher molecular mass are also formed.

The chloromethylation can significantly be accelerated and the amount of the dilute hydrochloric acid remaining after the reaction can preferably be diminished by adding gaseous hydrogen chloride, but the proportion of the dichloro derivatives in a product prepared in such a way of substantially higher in the case of an identical chlorine content. A similar result is obtained by using Lewis acids as catalysts.

The process of the invention also relates to the repeated utilization of the more dilute hydrochloric acid recovered after the chloromethylation. Namely, the amount of this acid is very important because of the fourfold molar excess. The repeated utilization of the waste hydrochloric acid is possible owing to its relatively high hydrochloric acid content which is in general 24 to 28%. It is worthwhile to recirculate the hydrochloric acid in such a way that the HCI content of the waste acid obtained in the last reaction be lower than 15%. When the time of the reaction is highly increased, it is possible to work at a higher temperature or possibly to use a Lewis acid as catalyst provided that the characteristic monochloro/dichloro ratio of the product is maintained at the desired level.

The physical and chemical properties of the sulfur-containing EP additive prepared by using the process described above are influenced to a high extent by the composition and structure of the starting hydrocarbon. First of all, the number of the carbon atoms and the structure of the alkyl groups bound to the aromatic ring are important which decide the reactivity of the alkylaromatic hydrocarbon and influence the properties and EP effect of the organic product obtained.

The most important characteristics of the obtained sulfur-containing EP additive are the adequate solubility and other physical and chemical indices connected with the utility (viscosity, flash point, heat stability, foaming liability) as well as the assuring of an appropriate EP effect which can be determined by tests carried out according to defined standard prescriptions. These prescriptions are described in DIN 51,350; ASTM D2266-67; and ASTM D 2783-69T.

It has been proved on the basis of qualifying examinations carried out on organic polysulfides that an advantageous EP effect is provided not only by the quantity of the sulfur introduced to the lubricating substance, but the organic group bound to the sulfur also plays an important role in this effect. It can be stated that the EP effect of polysulfides containing aromatic hydrocarbons is in general better, but the solubility in oil of these polysulfides is lower and can be improved in the course of the chloromethylation by increasing the monochloro/dichloro ratio and the number and molecular mass of the alkyl substituents bound to the aromatic ring.

It has also been proved by examination of the EP effect that the effectivity of the product is substantially influenced by the technology of the preparation of the organic polysulfide. On the basis of tests carried out by using the four-ball and FZG apparatuses, the more uniform product with a higher grade of purity prepared according to the process of the invention is more effective than e.g. the product obtained by the direct sulfurating of isobutylene.

The process of the invention is illustrated in detail with the aid of the following non-limiting Examples.

Example 1 483.5 g of a 35% hydrochloric acid solution and 41.7 g of powdered paraformaldehyde are introduced into a heatable and coolable round-bottom ground-glass flask fitted with a stirrer and thermometer. The mixture is heated to 50 C and stirred for about one hour until the paraformaldehyde is completely dissolved. Then the mixture is cooled to 350C and 123 g of a xylene isomeric mixture (corresponding to a 4:1 molar ratio of hydrogen chloride to xylene) are dropwise added to the system. The mixture is vigorously stirred and the reaction is continued until reaching a chlorine content of 14% (about 20 to 25 hours).Then the stirring is stopped, the mixture is cooled to room temperature, the chloromethylated xylene representing the upper phase is separated in a funnel and made free from hydrogen chloride by bubbling nitrogen through the solution. The composition of the chloromethylated xylene is determined by gas chromatography. The following results are obtained: Unreacted xylene 38.9% Monochloro derivatives 57.6% Dichloro derivatives 3.1% Monochloro/dichloro ratio 18.6 The chloromethylated xylene is made free from hydrogen chloride, then it is reacted with a sodium polysulfide of the composition Na2S3 to give a product with a sulfur content of 28.2% (after removing the unreacted xylene by distillation). The thus-obtained product is completely soluble in xylene, gas oil, ligroine and lubricating oils.

(a) The organic polysulfide prepared by usingAthe process described in Example 1 is mixed in a half proportion to a mixture consisting of antioxidant, detergent, and dispersing and corrosioninhibiting additives to give an EP additive composition with an opalescence point of -3"C, which is clear and transparent at room temperature. The EP additive composition is mixed in an amount of 6.5% by mass to a base oil with a viscosity classified as SAE-80 W-90. The welding load of the doped oil is 6000 N (determined according to the standard DIN 51,350).On carrying out the FZG test (type number A/16, 6/90/10) according to the standard DIN 51,354 on a drive oil with a viscosity classified as SAE-80 W-90 containing 6.5% of an EP additive composition, a deterioration grade number higher than 12 and a specific mass change of 0.032 mg/MJ are obtained.

(b) For comparison, the following experiment is carried out. The process described in the first part of Example 1 is followed with the difference that the xylene isomeric mixture is chloromethylated at 500C until reaching a chlorine content of 17.5%. The composition of the chloromethylated xylene is determined by gas chromatography to give the following results: Unreacted xylene 29.0% Monochloro derivatives 60.0% Dichloro derivatives 12.0% Monochloro/dichloro ratio 5.0 An organic polysulfide is prepared as described above, except that the chloromethylated xylene is reacted with a sodium sulfide of the composition Na2S4 to give a product with a sulfur content of 38.3% which is used for preparing an EP additive composition according to paragraph (a) of Example 1.The thus-obtained product is turbid, has an opalescence point of 38 C, and separates to two phases after one day's standing. It is completely soluble in xylene and gas oil, and it is only restrictedly soluble in ligroine and in oils with a low aromatic content.

(c) The organic polysulfide prepared as described in paragraph (b) of Example 1 is added in an amount of 3% by mass to a lubricating grease to result in a welding load value increased from 2000 N to 5000 N.

(d) The organic polysulfide prepared as described in paragraph (b) of Example 1 is added in an amount of 3% by mass to a metal-working coolant-lubricating fluid to result in a welding load value increased from 1600 N to 5000 N.

Example 2 The process described in Example 1 is followed with the difference that a single compound, i.e. m-xylene, is used as starting substance. After reaching a chlorine content of 14% (15 hours), the composition of the thus-chloromethylated m-xylene gives the following results on gas-chromatographic determination: Unreacted m-xylene 36.2% Monochloro derivative 61.0% Dichloro derivative 2.7% Monochloro/dichloro ratio 22.6 After being made free from hydrogen chloride by bubbling air through the solution, the chloromethylated product is reacted with a sodium polysulfide of the composition Na2S4 to give a product with a sulfur content of 36.3% which is unrestrictedly soluble in xylene, gas oil, ligroine and lubricating oils.

This sulfur-containing product is added in an amount of 6.5% by mass to a base oil with a viscosity classified as SAE-80 W-90 to increase the four-ball welding load value thereof to 6500 N (according to the standard DIN 51,350).

Example 3 The process described in the first part of Example 1 is followed with the difference that the xylene isomeric mixture is chloromethylated at 800C until achieving a chlorine content of 20% to give a chloromethylated xylene with the following composition as determined by gas chromatography Unreacted xylene 22.3% Monochloro derivatives 45.9% Dichloro derivatives 27.0% Other substances 4.8% Monochloro/dichloro ratio 1.7 After being made free from hydrogen chloride by bubbling air through the solution, the chloromethylated xylene is reacted with sodium polysulfide of a composition Na2S4. The thusobtained product separates to two phases after a short period of standing.

The upper phase shows the following characteristics: Quantity: 59% of the product Sulfur content: 42.1 % Solubility: unrestricted in xylene and gas oil, whereas restricted in ligroine and lubricating oils.

The lower phase shows the following characteristics: Quantity: 41% of the product Sulfur content: 57% Solubility: 10 9/100 g of benzene and xylene as solvent; practically insoluble in ligroine and lubricating oils.

This method is unsuitable for the economical preparation of an EP additive.

Example 4 The process described in Example 1 is followed with the difference that, instead of the xylene isomeric mixture, 220 g of octylbenzene are used which are chloromethylated until reaching a chlorine content of 9.1% within a reaction period lasting about 40 hours to give a product with the following composition as determined by gas chromatography: Unreacted octylbenzene 42.8% Monochloro derivatives 54.5% Dichloro derivatives 2.7% Monochloro/dicloro ratio 20.2 After being made free from hydrogen chloride by bubbling nitrogen through the solution, the chloromethylated octylbenzene is reacted with sodium polysulfide of a composition Na2S4 to give a product with a sulfur content of 24.8% which is soluble in xylene, gas oil, ligroine and lubricating oils.

This sulfur-containing product is added in an amount of 6.5% by mass to a base oil with a viscosity classified as SAE-80 W-90 to increase the four-ball welding load value thereof to 6000 N (according to the standard DIN 51,350).

Example 5 The process described in the first part of Example 1 is followed with the difference that, instead of the xylene isomeric mixture, 285.3 g of dodecylbenzene are used which are chloromethylated until reaching a chlorine content of 7.5% within a reaction period lasting about 70 hours to give a product with the following composition as determined by gas chromatography: Unreacted dodecylbenzene 44.0% Monochloro derivatives 53.5% Dichloro derivatives 2.5% Monochloro/dicloro ratio 21.4 After being made free from hydrogen chloride by bubbling nitrogen through the solution, the chloromethylated dodecylbenzene is reacted with sodium polysulfide of a composition Na2S4 to give a product with a sulfur content of 20.6%.

This sulfur-containing product is added in an amount of 6.5% by mass to a base oil with a viscosity classified as SAE-80 W-90 to increase the four-ball welding load value thereof to 5500 N (according to the standard DIN 51,350).

Example 6 The process described in the first part of Example 1 is followed, with the difference that the residual hydrochloric acid, containing 24% of HCI, from the chloromethylation experiment described in Example 1 is used. The chloromethylation is carried out at 500C until reaching a chlorine content of 14.2% within a reaction period lasting about 40 hours to give a product with the following composition as determined by gas chromatography: Unreacted xylene 39.6% Monochloro derivatives 55.1 % Dichloro derivatives 4.5% Monochloro/dichloro ratio 12.2 After being made free from hydrogen chloride by bubbling nitrogen through the solution, the chloromethylated xylene is reacted with sodium sulfide of a composition Na2S3 to give a product with a sulfur content of 29.6%.

This sulfur-containing product is added in an amount of 6.5% by mass to a base oil with a viscosity classified as SAE-80 W-90 to increase the four-ball welding load value thereof to 600 N (according to the standard DIN 51,350).

Example 7 The process described in the first part of Example 1 is followed with the difference that the hydrochloric acid is used in an amount of 241.8 g which corresponds to a 2:1 molar ratio of hydrochloric acid to xylene, instead of the 4:1 ratio used in the above experiments. The chloromethylation is carried out at 400C until reaching a chlorine content of 14% within a reaction period lasting about 40 hours to give a product with the following composition as determined by gas chromatography: Unreacted xylene 40. 1% Monochloro derivatives 56.6% Dichloro derivatives 4.0% Monochloro/dichloro ratio 14.2 After being made free from hydrogen chloride by bubbling nitrogen through the solution, the chloromethylated xylene is reacted with sodium sulfide of the composition Na2S3 to give a product with a sulfur content of 28.4%.

Example 8 1800 g of 28% hydrochloric acid and 339 g of paraformaldehyde are placed in a heatable and coolable round-bottom ground-glass flask fitted with a stirrer, thermometer, fritt-glass gas inlet tube and gas outlet tube. The mixture is heated to 500C and stirred for about one hour until the complete dissolution of the paraformaldehyde. Then the mixture is cooled to 25 C, 1000 g of a xylene isomeric mixture are dropwise added to the system, whereupon the bubbling-in of hydrogen chloride is started and the chloromethylation is continued until reaching a chlorine content of 14.1% (about 18 hours). The thus-obtained product shows the following composition as determined by gas chromatography: Unreacted xylene 45% Monochloro derivatives 45% Dichloro derivatives 10% Monochloro/dichloro ratio 4.5 After being made free from hydrogen chloride by bubbling nitrogen through the solution, the chloromethylated xylene is reacted with sodium polysulfide of the composition Na2S5 to give a product with a sulfur content of 41.5% which is completely soluble in benzene, xylene and gas oil, whereas its solubility is lower than 10 9/100 g of solvent an ligroine and lubricating oils.

(a) The sulfur-containing product is added in an amount of 3% by mass to a lubricating grease to increase the four-ball welding load value thereof from 2000 N to 5000 N.

(b) The product is added in an amount of 3% to a metal-working coolant-lubricating fluid to increase the welding load value thereof from 1600 N to 5000 N.

Example 9 For comparison, according to the German patent specification No. 2,838,981, 526 g of powdered sulfur, 920 g of cooled liquid isobutylene and 269 g of cooled liquid hydrogen sulfide are introduced into a high-pressure reactor fitted with a stirrer, heating jacket and condenser coil.

After closing the reactor, the mixture is heated to 170 C while stirring. The pressure rises to 92 bar. The reaction mixture is stirred for about 10 hours whilst the pressure gradually decreases below 20 bar. Then the reactor is cooled to room temperature and the thus-obtained dark reddish-brown liquid is poured into a distilling flask. After removing the unreacted substances by distillation, clarification and other purifying operations, the product is obtained in a yield of 760 g with a sulfur content of 42.5%.

The thus-obtained sulfur-containing product is added in an amount of 6.5% of a lubricating oil with a viscosity classified at SAE-80 W-90 to increase the welding load value thereof to 3800 N.

The drive oil containing the additive in an amount of 6.5% was qualified by using the FZG test (type number A/16, 6/9/10) according to the standard DIN 51,354. The deterioration grade number was found to be 12, whereas the specific mass change proved to be 0.122 mg/MJ.

Example 10 The process described in Example 1 is followed with the difference that 21 g of powdered paraformaldehyde are only used. The mixture is heated to 80 C, and after adding 123 g of a xylene isomeric mixture, the reaction mixture is stirred for 12 hours. The characteristics of the thus-prepared chloromethylated xylene are as follows: Chlorine content 13% Unreacted xylene 42.7% Monochloro derivatives 52.8% Dichloro derivatives 3.5% Monochloro/dichloro ratio 1 5. 1 After being made free from hydrogen chloride by bubbling air through the solution, the chloromethylated xylene is reacted with sodium polysulfide of a composition Na2S4 to give a product with a sulfur content of 37.2% which is completely soluble in xylene, gas oil, ligroine and lubricating oils.

Claims

1. Extreme pressure (ED) additive of the general formula, (R ~Arb)c(Sx)d wherein R', R1', Rail, RIV and RV are the same or different and each represents a hydrogen atom, a C 40 straight or branched chain or cyclic, saturated or unsaturated hydrocarbyl group or a derivative thereof; Ar stands for a monocyclic or polycyclic aromatic hydrocarbyl group or a derivative thereof; b means a number from 1 to 5; c means a number from 2 to 10; d means a number from 1 to 9; and x means a number from 1 to 6, useful for the preparation of auxiliary materials for lubricating and hydraulic oils, lubricating greases as well as for metal-working coolant and lubricating fluids.

2. A process for the preparation of extreme pressure (EP) additives as claimed in claim 1 of the general formula (Rl V~Arb)c(sx)d wherein R', Roll, Rill, RIV and RV are the same or different and each represents a hydrogen atom, a C1 40 straight or branched chain or cyclic, saturated or unsaturated hydrocarbyl group or a derivative thereof; Ar stands for a monocyclic or polycyclic aromatic hydrocarbyl group or a derivative thereof; b means a number from 1 to 5; c means a number from 2 to 10; d means a number from 1 to 9; and x means a number from 1 to 6, by the reaction of an organic chlorine compound of the general formula (Rl-v-Arb)-claS wherein R', R', Rail, R'V, RV, Ar and b are as defined in claim 1 and "a" means a number from 1 to 5, with a metal sulfide of the general formula MnSXS wherein M represents an alkali metal and/or an alkali-earth metal, n means a number from 1 to 2 and x means a number from 1 to 6, which comprises chloromethylating a hydrocarbon of the general formula RI-V~Arb, wherein R', R'', R'#, R'V, RV, Ar and b are as defined in claim 1, with a formaldehyde solution and/or with paraformaldehyde together with an aqueous solution of hydrochloric acid and/or gaseous hydrogen chloride in the presence or without a catalyst, by adjusting to at least 7:1 the percentage ratio of the monochloro to di- and polychloro compounds in the case of organic polysulfides suitable for the preparation of extreme pressure (EP) additive mixtures, whereas by adjusting to at least 3:1 the percentage ratio of the monochloro to di- and polychloro compounds in the preparation of extreme pressure (EP) additives for lubricating and hydraulic oils, lubricating greases and metal-working auxiliary materials, then reacting the thus-obtained chloromethylated compound with a metal polysulfide of the general formula MnSx wherein M, n and x are the same as defined above, and optionally purifying the thus-obtained final product.

3. A process as claimed in claim 2 for the preparation of a sulfur compound useful to obtain an extreme pressure (EP) additive mixture for lubricating oils, which comprises chloromethylating an isomeric xylene mixture at most at 400C by using a hydrochloric acid/paraformaldehyde/xylene molar ratio of at least 4:1.2:1 until reaching a chlorine content of 12 to 14%, then reacting the chloromethylated xylene with sodium polysulfide and optionally purifying the thus-obtained product.

4. A process as claimed in claim 2 for the preparation of an extreme pressure (EP) additive for lubricating and hydraulic oils, lubricating greases as well as metal-working auxiliary materials, which comprises chloromethylating an isomeric xylene mixture at 40 to 500C by using a hydrochloric acid/paraformaldehyde/xylene molar ratio of 4:1.2:1 until reaching a chlorine content of 14 to 17.5%, then reacting the chloromethylated xylene with sodium polysulfide and optionally purifying the thus-obtained product.

5. A process as claimed in any of claims 2 to 4, which comprises repeatedly using the more dilute hydrochloric acid recovered after the chloromethylation.

6. A process as claimed in claim 2 for the preparation of a sulfur compound suitable to obtain an extreme pressure (EP) additive mixture for lubricating oils, which comprises chloromethylating an isomeric xylene mixture at most at 1000C by using a hydrochloric acid/paraformaldehyde/xylene molar ratio of at most 4:0.8:1 until reaching a chlorine content of 10 to 14%, then reacting the chloromethylated xylene with sodium polysulfide and optionally purifying the thus-obtained product.

7. A process as claimed in claim 2 for the preparation of an extreme pressure (EP) additive for lubricating and hydraulic oils, lubricating greases as well as metal-working auxiliary materials, which comprises chloromethylating an isomeric xylene mixture at a temperature from 80 to 100 C by using a hydrochloric acid/paraformaldehyde/xylene molar ratio of at most 4:1:1 until reaching a chlorine content of 12 to 17.5%, then reacting the chloromethylated xylene with sodium polysulfide and optionally purifying the thus-obtained product.

8. An extreme pressure additive as claimed in claim 1, substantially as hereinbefore described in any one of Examples 1 to 10.

9. A process as claimed in claim 2, substantially as hereinbefore described in any one of Examples 1 to 10.

10. An extreme pressure additive made by a process as claimed in any one of claims 2 to 7.

11. Lubricating oil, hydraulic oil, lubricating greases, metal working coolant or lubricating fluid or an additive therefor containing an extreme pressure additive as claimed in claim 1, 8 or 10.