GB2124624A - Lubricating oil additive - Google Patents

Abstract

An additive for a lubricating oil is constituted by an organic compound having a molecular weight of approximately 300-1200 and containing in its molecule at least one group: <IMAGE> wherein x is 1 or 2 and the free bonds are connected to alkyl, carboxylic acid or carbonic acid alkyl ester radicals. The additive is prepared by reacting sulphur monochloride or dichloride with a hydrocarbon compound having at least one double olefinic bond in its molecule, or with an alkylester compound having at least one double olefinic bond, to give a sulphochlorinated intermediate, and then reacting this intermediate with a thiocyanate of an alkaline metal or ammonium. When it forms part of a lubricating oil composition, the multifunctional additive exerts an antioxidant action, inhibits corrosion induced by sulphur and its derivatives, inhibits the formation of lead pastes, and also manifests antiwear characteristics.

Description

SPECIFICATION Lubricating oil additive This invention relates to a multifunctional ash-free additive for lubricating oils. The invention also relates to the process for preparing the additive, and to lubricating oil compositions which contain the additive.

The problem of lubricating oil deterioration is a problem which one trys to overcome, by suitable formulation of the lubricating oil, since the deterioration of lubricating oils leads to the formation of products which are corrosive towards the metal surfaces with which the lubricating oils come into contact. In recent years it has become common practice to incorporate in lubricating oils additives which are capable of inhibiting oil deterioration and the formation of damaging deposits. These additives are generally classified into groups according to their action in improving the lubricating oil.

Thus, the additives of one group inhibit corrosion and stabilise the lubricating oil towards oxidative degradation. Another group comprises corrosion inhibitors which oppose the corrosion characteristics of the lubricating oil degradation products, or passivate the metal surface against the corrosive action of these degradation products. A further group comprises antiwear agents which enable metal-metal contact between metal surfaces in movement to be avoided.

Several additives are often required in order to give the lubricating oil a number of characteristics, and this is disadvantageous both for the cost reasons and for reasons of mutual compatibility between additives. Thus, current research is directed towards the development of so-called multifunctional additives capable of providing lubricating oils with several desirable characteristics. Thus for example US-A-261 9464 described lubricating oil compositions containing alkylmonothiocyanate to provide oxidation resistance and to inhibit corrosion. US-A-27 1 9126 describes polsulphide thiodiazoles used as antioxidant and antiwear additives for lubricating oils.

It has however been found that the antioxidant and antiwear characteristics of known additives do not always attain completely satisfactory values. There is also an interest in those additives which, in addition to these characteristics, also inhibit corrosion and the formation of lead pastes or sludges.

The present invention provides an ash-free multi-functional additive which is an organic compound, preferably having a molecular weight of from about 300 and about 1200, containing in its molecule at least one group:

wherein x is 1 or 2 and wherein the bonds from the carbon atoms (other than those bonds connected to the thiocyano groups) are connected to alkyl radicals or alkylester radicals of a carboxylic or carbonic acid.

Thus, the present invention provides an ash-free multifunctional additive for lubricating oils, which provides antioxidant and antiwear action, and which inhibits corrosion induced by sulphur and its derivatives, and the formation of lead pastes or sludges.

Preferably, the additive of the present invention is liquid at ambient temperature (20-250C) and has a molecular weight in the range of 400 to 1000.

The process for preparing the additive of the present invention comprises reacting sulphur monochloride or dichloride with a hydrocarbon compound having at least one double olefinic bond in its molecule, or with an alkylester of a carboxylic or carbonic acid having at least one double olefinic bond, to give a sulphochlorinated intermediate, and then reacting this intermediate with a thiocyanate of an alkaline metal (i.e. an alkali metal or an alkaline earth metal) or of ammonium.

The unsaturated hydrocarbons which can be used include linear or branched olefins in general, and in particular the oligomers of propylene, butene and isobutene, and C4 to C24 a-olefins. In the reaction with sulphur monochloride or dichloride, terpene hydrocarbons can also be used, as can alkylesters of carboxylic acids or of carbonic acid, which have at least one unsaturated olefin bond, such as oleic acid derivatives, jojoba oil, lard oil, and unsaturated carbonic esters such as allylalkylcarbonates and oleylalkylcarbonates.

The sulphochlorination consists of treating the aforesaid unsaturated compounds with a sulphur chloride, and in particular with sulphur monochloride or dichloride. The reaction may comprise adding the sulphochlorinating agent to the unsaturated compound, the actual reaction itself, and final stripping.

According to the reactivity of the unsaturated compound, the reaction can be conducted either in mass or in an inert solvent, preferably at a temperature in the range of O to 10000, more preferably 20 to 8000, and preferably for a time of 1 to 10 hours.

The sulphochlorinated intermediate obtained in this manner can be represented as follows:

wherein x is 1 or 2 The quantity of sulphur chloride used in the reaction is usually at least equal to the stoichiometric amount necessary for forming the intermediate.

The reaction between the sulphochlorinated intermediate and the thiocyanate of the alkaline metal or ammonium may be conducted either in mass under either homogeneous or heterogeneous conditions, or in a suitable unreactive solvent, preferably at a temperature in the range of O to 2000C and preferably for a time of 1 to 10 hours. With regard to the proportion of reagents, at least one mole of thiocyanate is usually used for each gram-atom of chlorine in the sulphochlorinated intermediate.

Because of its multiplicity of action and absence of ash, the additive of the present invention obtained in this manner can be applied in the most varied fields in which the action of the lubricant is required. Thus it can be used in engine oils, in transmission and hydraulic fluids, in metal machining oils, etc., usually in a concentration range varying from 0.1 to 10% by weight, and preferably from 0.3 to 3% by weight.

In particular, the additive of the present invention can be added to a vast range of lubricants, comprising hydrocarbons of mineral or synthetic origin, carboxylic acid esters, polyglycols, polyolefins, alkylesters of carbonic and/or phosphoric acids and their mixtures in any proportion. The additive can be dissolved in the oil in the presence of other agents such as one or more dispersants, detergents, antioxidants, pour point depressants, viscosity index improvers, antiwear agents, extreme pressure additives, anti-foaming emulsifiers, etc. The use of the additive is particularly convenient in the formulation of engine oils in which, more than in others, its multiplicity of action is fully utilised.

Examples of these formulations as shown in the following Table 1.

TABLE 1

15W/50 15W/40 15W/So SAE 30 Mineral oil (% by weight) 76 79.1 60.5 91.9 Ester base (% by weight) ~ , 15 Detergent-dispersant-inhibitor pack (% by weight) 10 1 1.9 9.5 8.1 Viscosity index improvement polymer (% by weight) 14 9 15 The components can be different for the different formulations.The additive of the present invention provides antioxidant action, inhibits corrosion caused by sulphur and its derivatives, inhibits the formation of lead paste or sludge, and manifests antiwear properties.

The invention will now be illustrated by the following examples. The additives of the invention described in the following Examples have molecular weights in the range of 300 to 1200.

EXAMPLE 1 67.5 g (0.5 moles) of sulphur monochloride were added slowly, under stirring, to 224 g (1 mole) of 1 -hexadecene. Reaction was carried out in a nitrogen atmosphere at ambient temperature for a time of 3.5 hours, until the acidity number of the mixture fell to about 3 mg KOH/g. A stream of nitrogen was then passed through the reaction mixture until the acidity fell to a value of the order of 0.3 mg KOH/g.

60.6 g (0.75 moles) of sodium thiocyanate were added to 200 g of the intermediate product thus obtained, containing 24 g of chlorine (0.68 gram-atoms). The reagent mixture, under stirring and an inert atmosphere, was heated to 160~170 C and kept under these conditions for 7 hours. After cooling, the sodium chloride by-product of the reaction was filtered using a filter aid. An additive of the present invention was thus obtained in the form of a brown oil-soluble viscous liquid at ambient temperature.

The additive obtained in this Example increases the stability of the lubricating oil towards oxidation. In order to evaluate this characteristic, there was used an oxidation test in which air was bubbled through in accordance with the modified IP 48 procedure. The test parameters were: temperature 1 750C; air flow rate 50 ml/min; time 48 hours; presence of copper and iron strips.

The following Table 2 shows the viscosity values in cst at 400C of the samples before and after the oxidation test, and the percentage variation in the viscosity of the samples thus treated. For comparison purposes, the test was also carried out with a commercial thiodiazole polysulphide additive.

The results are shown in the following Table 2.

TABLE 2 ~~~~~~~~~~~~~~~~~~~~~~~~~

Initial Final Difference V400C (cst) ~ V#ODC(C6t) V(%) SN 450 oil as such 85 170 100 Additive of this Example (0.3%) 85 Additive of this Example (1%) 85 94.2 10.8 Commercial additive (0.3%) 85 99.6 17.2 Commercial additive (1%) 85 103.0 21.2 l The additive of this Example controls and inhibits the corrosion of copper by sulphur and its derivatives.

Besides having a high merit point in an ASTM D 130 test, the additive of this Example raises that of a sulphochlorinated compound containing active sulphur, such as that obtained as the intermediate in this Example. The test results are as given in the following Table 3.

TABLE 3

Merit Additive of this Example (1% by weight) 1 b Intermediate of this Example (5% by weight) 4c Additive + intermediate (5 + 0.3% by weight) 2a Additive + intermediate (5 + 1% by weight) 1 b The additive of this Example inhibits the formation of lead pastes or sludges. This characteristic was evaluated by using a lead point screener on an Alfetta engine.A SAE 30 unigrade formulation containing 8.1% by weight of a detergent-dispersant-inhibitor pack (zinc sulphonatepolyisobutenylsuccinimide-dithiophosphate), which gives rise to the formation of lead paste or sludges, was used as the reference. The test results on the engine, which were obtained over 30 hours, are as given in the following Table 4.

TABLE 4

Merit SAE 30 formulation 84 SAE 30 formulation + 0.3% additive of this Example 98 The additive of this Example has good antiwear characteristics, on tribological examination. In this respect, its performance on an LFW-1 machine using the method of ASTM D 271 'i- 68, and on a 4- ball wear machine using steel balls, operating under the following conditions, were measured: angular velocity 126 rad/s load 40 da N oil temperature 750C test duration 1 hour.

The results obtained, as given in the following Table 5, relate to the wear in mm using SN 450 oil as such and containing 1% by weight of the additive of this Example. For comparison purposes, the results are given for an SN 450 oil composition containing 1% by weight of the commercial additive thiodiazole polysulphide.

TABLE 5

LRN-1 4-ball wear machine wear (mm) diameter worn (mm) SN 450 2.96 1.26 SN 450 + 1% additive of this Example 1.03 0.50 SN 450 + 1% commercial additive 1.40 0.65 EXAMPLE 2 37.9 g (0.46 moles) of sodium thiocyanate were added to 200 g of jojoba oil sulphochlorinated by the same method used in the preparation of the intermediate of Example 1, and containing 1 5 g of chlorine (0.42 gram-atoms). A reaction was conducted as in Example 1, until an additive was obtained in the form of a very viscous oil-soluble liquid. The performance of the additive was similar to that of the additive obtained in Example 1.

EXAMPLE 3 Analogously to the preceding examples, 38.8 g (0.47 moles) of sodium thiocyanate were added to 300 g of sulphochlorinated allyloleyl carbonate containing 1 5.3 g of chlorine (0.43 gram-atoms).

Operating as in Example 1, an additive was obtained in the form of a dark brown viscous oil-soluble liquid. The performance of the additive was similar to that of the additive obtained in Example 1.

Claims (16)

1. Lubricant composition comprising a lubricating oil and an additive, the additive being present in an amount which is less than the amount of the lubricating oil, and the additive being an organic compound having a molecular weight of from approximately 300 to approximately 1 200 and containing in its molecule at least one group:

wherein x is 1 or 2 and wherein the bonds from the carbon atoms (other than those bonds connected to the thiocyano groups) are connected to alkyl radicals or to carboxylic acid or carbonic acid alkylester radicals.

2. A composition as claimed in claim 1, wherein the additive has a molecular weight of from 400 to 1000.

3. A composition as claimed in claim 1 or 2, containing from 0.1 to 10% by weight of the additive.

4. A composition as claimed in claim 3, containing from 0.3 to 10% by weight of the additive.

5. A lubricant composition as claimed in claim 1, substantially as described in any of the foregoing Examples.

6. A process for preparing an additive for a iubricanting oil, which comprises reacting sulphur monochloride or dichloride with a hydrocarbon compound having in its molecule at least one double olefinic bond, or with an alkylester of a carboxylic acid or carbonic acid which comprises at least one double olefinic bond, to give a sulphochlorinated intermediate; and reacting the intermediate with a thiocyanate of an alkaline metal or of ammonium.

7. A process according to claim 6, wherein the unsaturated hydrocarbon is a linear or branched olefin, an oligomer of propylene, butene or isobutene, a C4 to C24 cg-olefin, or a terpene hydrocarbon.

8. A process according to claim 6, wherein the ester of carboxylic acid or carbonic acid is an oleic acid derivative, jojoba oil, lard oil, an allylalkylcarbonate or an oleylalkylcarbonate.

9. A process according to any of claims 6 to 8, wherein the reaction for preparing the intermediate is carried out at a temperature of from 0 to 1000C.

10. A process according to claim 9, wherein the reaction for preparing the intermediate is carried out at a temperature of from 20 to 800 C.

11. A process according to any of claims 6 to 10, wherein the reaction for preparing the intermediate is carried out for a time of from 1 to 10 hours.

12. A process according to any of claims 6 to 11, wherein the reaction of the intermediate with the thiocyanate is carried out at a temperature of from 0 to 2000C.

13. A process according to any of claims 6 to 12 wherein the reaction of the intermediate with the thiocyanate is carried out for a time of from 1 to 1 0 hours.

14. A process according to claim 6, substantially as described in any of the foregoing Examples.

1 5. An additive for a lubricating oil, when prepared by a process according to any of claims 6 to 14.

16. An additive for a lubricating oil, the additive being an organic compound having a molecular weight of from approximately 300 to approximately 1200 and containing in its molecule at least one group:

wherein x is 1 or 2 and wherein the bonds from the carbon atoms (other than those bonds connected to the thiocyano groups) are connected to alkyl radicals or to carboxylic acid or carbonic acid alkylester radicals.

1 7. An additive as claimed in claim 1 6, having a molecular weight of from 400 to 1000.