WO1995014751A1

WO1995014751A1 - Alkaline earth metal sulphurised hydrocarbyl phenates, their preparation, and concentrates and finished lubricating oils containing them

Info

Publication number: WO1995014751A1
Application number: PCT/GB1994/002552
Authority: WO
Inventors: Stephen James Cook; Paul Kristian Robinson
Original assignee: Bp Chemicals (Additives) Limited
Priority date: 1993-11-25
Filing date: 1994-11-21
Publication date: 1995-06-01
Also published as: GB9324208D0; EP0680508A1; JPH08506141A

Abstract

A composition suitable for use as an additive to lubricating oils comprises a mixture of alkaline earth metal sulphurised hydrocarbyl phenates having hydrocarbyl substituents derived from (i) either propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms. As compared with a composition comprising hydrocarbyl phenate derived from propylene tetramer or butylene trimer alone the compositions of the invention are more compatible with hydrocarbyl sulphonates, commonly found with phenates in lubricating oil additive packages.

Description

ALKALINE EARTH METAL SULPHURISED HYDROCARBYL PHENATES, THEIR PREPARATION, AND CONCENTRATES AND FINISHED LUBRICATING OILS

CONTAINING THEM The present invention relates in general to alkaline earth metal sulphurised hydrocarbyl phenates, their preparation and their use in concentrate and lubricating oil compositions.

In the internal combustion engine, by-products from the combustion chamber often blow by the piston and admix with the lubricating oil. Many of these by-products form acidic materials within the lubricating oil. This is particularly marked in diesel engines operating on low-grade fuels of high sulphur content wherein corrosive acids are produced by combustion. The acids thereby incorporated in the lubricating oil can include sulphur acids produced by oxidation of sulphur, hydrohalic acids derived from halogen lead scavengers in the fuel and nitrogen acids produced by the oxidation of atmospheric nitrogen within the combustion chamber. Such acids cause deposition of sludge and corrosion of the bearings and engine parts leading to rapid wear and early breakdown of the engine.

Compounds generally employed to neutralise the acidic materials and disperse sludge within the lubricating oil include the sulphurised metal alkyl phenates, wherein the metal is an alkaline earth metal such as calcium, magnesium or barium. Both "normal" and "overbased" sulphurised alkaline earth metal alkyl phenates have been employed. The term "overbased" is used to describe those sulphurised alkaline earth metal alkyl phenates in which the ratio of the number of equivalents of the alkaline earth metal moiety to the number of equivalents of the phenol moiety is greater than one, and is usually greater than 1.2 and may be as high as 4.5 or greater. In contrast, the equivalent ratio of alkaline earth metal moiety to phenol or salicylic acid moiety in "normal" alkaline earth metal alkyl phenates is one. Thus, the "overbased" material contains greater than 20% in excess of the alkaline earth metal present in the corresponding

"normal" material. For this reason "overbased" sulphurised alkaline earth metal alkyl phenates have a greater capability for neutralising acidic matter than do the corresponding "normal" alkaline earth metal alkyl phenates. It is customary to use alkaline earth metal sulphurised hydrocarbyl phenates in lubricating oil additive formulations together with alkaline earth metal hydrocarbyl sulphonates, thereby achieving a blend of properties in terms of acid neutralisation capability, corrosion inhibition, antioxidancy, etc. It is well- known that such combinations can give rise to problems. Thus it is recognised that solubility problems can arise when a calcium sulphurised hydrocarbyl phenate wherein the hydrocarbyl substituent is derived from propylene tetramer, a much used commercial product, is formulated with some highly overbased calcium hydrocarbyl sulphonates. Propylene tetramer is a highly branched Ci2~-_.lkene. in addition to the C^-a-l-ke e fragments there is also present low levels of

The manufacture of calcium sulphurised hydrocarbyl phenates wherein the hydrocarbyl substituent is derived from propylene tetramer involves the step of alkylating phenol with propylene tetramer in the presence of an acid catalyst, for example an acidic clay. Typically it consists of up to 70% of paradodecyl- phenol with the other 30% being made up of the ortho isomer, 2,4- didodecyl phenol, dodecylphenylether, and low molecular weight isomers. It is believed, though we do not wish to be bound by any theory, that low molecular weight isomers, parahexylphenol (Cg) , paraoctylphenol (Cg), and tertiary butyl phenol present in the alkylphenol give rise to calcium phenates which are insoluble in the presence of some highly overbased sulphonates.

Whatever the reason for the observed insolubility, we have found that a solution to the problem is to incorporate into the hydrocarbyl phenol composition from which the alkaline earth metal sulphurised hydrocarbyl phenate is derived by reaction with an alkaline earth metal base, a hydrocarbyl phenol wherein the hydrocarbyl substituent is derived from an alkene having greater than 12 carbon atoms.

Accordingly in one aspect the present invention provides a composition suitable for use as an additive to lubricating oils comprising a mixture of alkaline earth metal sulphurised hydrocarbyl phenates having hydrocarbyl substituents derived from (i) either propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms.

The alkaline earth metal of the alkaline earth metal sulphurised hydrocarbyl phenates mixture may suitably be either calcium, barium or magnesium, preferably calcium or barium, more preferably calcium.

As regards (i), of the alternatives propylene tetramer or butylene trimer, propylene tetramer is preferred. With reference to the alkene having greater than 12 carbon atoms (ii), preferably the alkene is a straight-chain alkene. Preferably the alkene contains at least 16 carbon atoms. Suitably the alkene may contain up to 50 carbon atoms, typically up to 30 carbon atoms. An example of a suitable alkene is octadecene, a straight-chain C^_β- alkene.

Of the hydrocarbyl substituents, the proportion of hydrocarbyl substituent derived from the alkene having greater than 12 carbon atoms may suitably be up to 50, or more, mole %, typically about 20 mole %. It may be as low as 1 mole %, though amounts greater than 5 mole %, typically about 10 mole %, are preferred.

In another aspect the present invention provides a process for the production of the composition suitable for use as an additive to lubricating oils as hereinbefore described which process comprises reacting at elevated temperature an alkaline earth metal base in the presence of a hydroxylic solvent with a mixture of sulphurised hydrocarbyl phenols wherein the hydrocarbyl substituents are derived from (i) either propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms. The mixture of sulphurised hydrocarbyl phenols may be obtained by either (A) simply mixing a pre-formed hydrocarbyl phenol wherein the hydrocarbyl substituent is derived from either propylene tetramer or butylene trimer with a pre-formed hydrocarbyl phenol wherein the hydrocarbyl substituent is derived from at least one alkene having greater than 12 carbon atoms, either, or both, the pre-formed hydrocarbyl phenols being sulphurised or being sulphurised during the reaction with the alkaline earth metal base, or (B) reacting in a preliminary step phenol with a mixture of (i) propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms and thereafter reacting the product of the preliminary step with a source of sulphur in the presence or absence of the alkaline earth metal base.

As regards the alternatives (A) and (B), alternative (B) wherein the product of the preliminary step is reacted with a source of sulphur in the presence of the alkaline earth metal base is preferred because it leads to the advantage that less of the more expensive alkene having greater than 12 carbon atoms need be utilised to achieve solubility improvements comparable with those found using alternative (A) .

The source of sulphur may be either elemental sulphur or a sulphur compound, for example a sulphur halide. Preferably elemental sulphur is used as the source of sulphur. The amount of sulphur employed may suitably be sufficient to provide an alkaline earth metal sulphurised hydrocarbyl phenate mixture containing from 0.1 to 15, for example from 0.5 to 10, percent by weight of sulphur.

The preparation of hydrocarbyl phenols is well-known in the art. Typically phenol is alkylated at elevated temperature in the presence of an acidic catalyst. The elevated temperature may suitably be in the range from 30 to 200°C, preferably from 110 to 150°C. Acidic materials useful as catalysts include both protonic and Lewis acids. Such materials include for example sulphuric acid or phosphoric acid which may be unsupported or supported. Suitable supports include clays and zeolites. Alternatively, the acid- exchanged forms of clays or zeolites may be employed. The alkaline earth metal of the alkaline earth metal base is preferably calcium, barium or magnesium, more preferably calcium or barium, most preferably calcium. The base moiety may suitably be an oxide or a hydroxide, preferably the hydroxide. A calcium base may be added, for example, in the form of quicklime (CaO) or in the form of slaked lime (Ca(OH)2), preferably in the form of slaked lime. The alkaline earth metal base is preferably added in an amount relative to the alkyl phenol sufficient to produce an overbased alkaline earth metal sulphurised hydrocarbyl phenate. The hydroxylic solvent may suitably be (1) either:- (i) a polyhydric alcohol having 2 to 4 carbon atoms, (ii) a di- (C₃ or C₄) glycol, (iii) a tri- (C2 to C₄) glycol, or (iv) a mono- or poly- alkylene glycol alkyl ether of the formula:- RfO ^_χOR² (I) wherein in the formula (I) R is a C-^ to Cg alkyl group, R¹ is an alkylene group, R² is hydrogen or a C^ to Cg alkyl group and x is an integer of from 1 to 6.

The aforesaid solvents (i) to (iv) may be used either alone or in combination with either (2) a hydrocarbon solvent or (3) either (a) water, (b) a C^ to C20 monohydric alcohol, (c) a ketone containing up to 20 carbon atoms, (d) a carboxylic acid ester containing up to 10 carbon atoms, (e) an aliphatic, alicyclic or aromatic ether containing up to 20 carbon atoms or (4) a C^ to C monohydric alcohol in combination with a hydrocarbon solvent (2).

Suitable compounds having the formula (I) include the monomethyl or dimethyl ethers of (a) ethylene glycol, (b) diethylene glycol, (c) triethylene glycol or (d) tetraethylene glycol. A suitable compound is methyl diglycol (CH₃OCH2CH2OCH2CH2OH) . Mixtures of glycol ethers of the formula (I) and glycols may also be employed. The polyhydric alcohol may suitably be either a dihydric alcohol, for example ethylene glycol or propylene glycol, or a trihydric alcohol, for example glycerol. The di-(C3 or C₄) glycol may suitably be dipropylene glycol, the tri-(C2 to C₄) glycol may suitably be triethylene glycol. Preferably the component (1) is either ethylene glycol or methyl diglycol. (2) is a hydrocarbon solvent which may be aliphatic or aromatic. Examples of suitable hydrocarbons include toluene, xylene, naphtha and aliphatic paraffins, for example hexane, and cycloaliphatic paraffins. (3) may be either (i) water (ii) a C^ to C_2Q monohydric alcohol, (iii) a ketone having up to 20 carbon atoms, (iv) a carboxylic acid ester having up to 10 carbon atoms or (v) an aliphatic, alicyclic or aromatic ether having up to 20 carbon atoms. Examples are methanol, 2-ethyl hexanol, cyclohexanol, cyclohexanone, benzyl alcohol, ethyl acetate and acetophenone. (4) may be a C-^ to C₄ monohydric alcohol, preferably methanol, in combination with a hydrocarbon solvent (2). Preferred solvents comprise ethylene glycol, a mixture of ethylene glycol and 2-ethyl hexanol and a mixture of methanol and toluene.

As a supplementary solvent or diluent it is preferred to employ a lubricating oil. Suitable lubricating oils will be described hereinafter in relation to the concentrate.

For the production of overbased phenates, as opposed to neutral phenates, it is preferred to add, subsequent to addition of the alkaline earth metal base, carbon dioxide, suitably in the form of a gas or a solid, preferably in the form of a gas. In gaseous form it may suitably be blown through the reaction mixture.

An overbasing catalyst may be employed if desired, but in general the reaction can be accomplished satisfactorily in the absence of a catalyst. Suitable catalysts are well-known in the art. Suitably the elevated temperature at which the process is operated may be a temperature in the range from 15 to 200°C, preferably from 50 to 175°C. The selection of the optimum temperature within the aforesaid range will depend to a large extent on the nature of the solvent employed. Typically using ethylene glycol for example as solvent the optimum temperature will be in the range from 100 to 175°C, whereas using methanol/toluene as solvent the optimum temperature will be below 100°C.

It is preferred to remove the solvent, suitably by distillation at subatmospheric pressure. Finally it is preferred to separate off any insoluble matter, suitably by filtration or centrifugation, preferably by filtration. Additive manufacturers generally market additives in the form of concentrates, ie concentrated solutions of the additive in a suitable solvent, which for use as a lubricating oil additive is generally most conveniently a lubricating oil.

In another aspect the present invention therefore provides a concentrate suitable for incorporation into a finished lubricating oil comprising a lubricating oil and the composition comprising a mixture of alkaline earth metal sulphurised hydrocarbyl phenates as hereinbefore described.

The amount of the lubricating oil in the concentrate composition may suitably be from 10 to 90%, for example from 20 to 80%, by weight of the composition. The lubricating oil may suitably be an animal, a vegetable or a mineral oil. Suitably the lubricating oil is a petroleum-derived lubricating oil, such as a naphthenic base, paraffin base or mixed base oil. Solvent neutral oils are particularly suitable. Alternatively, the lubricating oil may be a synthetic lubricating oil. Suitable synthetic lubricating oils include synthetic ester lubricating oils, which oils include diesters such as di-octyl adipate, di-octyl sebacate and tri-decyladipate, or polymeric hydrocarbon lubricating oils, for example liquid polyisobutenes and poly-alphaolefins.

The composition is preferably overbased. Suitably the TBN (Total Base Number) of the composition may be in the range from 50 to 350 mg KOH/g, for example 100 to 300 mg KOH/g.

The concentrate preferably further incorporates an overbased alkaline earth metal hydrocarbyl sulphonate, which may be any such sulphonate commonly employed as an additive to lubricating oils. Typically the sulphonate will be a highly overbased sulphonate, for example one having a TBN greater than 300 mg KOH/g. It is an advantage of using the alkaline earth metal sulphurised hydrocarbyl phenate mixture of the present invention that sulphonates which are recognised in the art as having incompatibility problems with phenates derived from propylene tetramer or butylene trimer alone can be rendered more compatible therewith. The concentrate composition may also contain one or more other types of conventional lubricating oil additives, for example viscosity index improvers, anti-wear agents, antioxidants, dispersants, rust inhibitors, pour-point depressants, or the like. In a final aspect the present invention provides a finished lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion of a concentrate as hereinbefore described.

Suitable lubricating oils may be any of those as hereinbefore described in relation to the concentrate.

Conventional lubricating oil additives as hereinbefore described in relation to the concentrate may, if desired, be incorporated into the finished lubricating oil composition as an alternative to adding them to the concentrate or as a supplement thereto.

The amount of the concentrate present in the finished lubricating oil composition will depend on the nature of the final use. Thus, for marine lubricating oils the amount of concentrate present may suitably be sufficient to provide a TBN of from 9 to 100 and for automobile engine lubricants the amount may suitably be sufficient to provide a TBN of from 4 to 20.

The invention will now be further illustrated by reference to the following Examples.

The term "AV" is used to denote the Alkalinity Value in mg KOH/g as measured by the method of ASTM D2896. The viscosity was measured by the method of ASTM D445. Comparison Test

(A) Alkylation of phenol with propylene tetramer (a) Reaction stage Phenol (300g; 3.2 moles) and propylene tetramer (300g; 1.8 moles) were charged to a 1 litre 5-necked, round bottom flask equipped with an air condenser, thermo-pocket containing a thermometer and thermocouple, and an agitator. Agitation was achieved by use of a vibro-mix motor with a stainless steel perforated disc. The temperature of the mixture was raised to 45°C, at which point FULCAT 22B catalyst (45g) was added. The temperature was then raised to 135°C over about 20 minutes. After 2 hours at 135°C the reaction mixture was allowed to cool to 80°C. At 80° the crude alkylphenol was filtered through CLARCEL DIC filter aid. The weight of the filtrate was noted. (b) Distillation stage

The reaction intermediate from step (a) (approx. 400g) was charged to a 1 litre 5-necked, round bottom reaction flask equipped with a take-off condenser (with thermometer to determine the vapour temperature), agitator (paddle type) and thermo-pocket (with thermometer and thermocouple) . The temperature of the crude alkylphenol was raised to 100°C, at which point vacuum (29 inches Hg) was applied and the temperature was raised to a point at which either:- (i) the temperature of the reactor reached 235°C, or

(ii) the temperature of the vapour off-take leading to the condenser attained 140°c. tB . Preparation of calcium sulphurised alkyl phenate

Alkyl phenol obtained in step (A) (147g), lime (66g; 0.89 mole), sulphur (21g; 0.66 mole), 150SN diluent oil (129g) and a

"heel" of 250 AV calcium sulphurised alkyl phenate (31g) were charged into a 1 litre round bottom flask fitted with a take-off condenser, carbon dioxide sparge, and agitator (paddle-type). The mixture was heated to 145°C (under slight vacuum) whilst stirring (approx. 500 rpm) . Ethylene glycol (42g; 0.68 moles) was added whilst raising the temperature to 165°C over approximately 20 minutes. After 1 hour at 165°C carbon dioxide (23g; 0.52 mole) was added under atmospheric pressure. A vacuum (29 inches Hg) was applied and the temperature raised to 200°C. The reactor was held under these conditions for 1 hour. The amounts of crude product and volatile material were noted. After cooling to approximately 140°C the crude product was filtered through CLARCEL DIC filter aid.

This is not an example according to the present invention because the hydrocarbyl substituent of the calcium sulphurised hydrocarbyl phenate was not derived from a mixture of propylene tetramer and an alkene having greater than 12 carbon atoms. It is included only for the purpose of comparison. Example 1

The procedure of the Comparison Test was repeated except that:- (i) in step (A) (a) instead of propylene tetramer (1.8 moles) there was used a mixture of octadecene (0.9 mole) and propylene tetramer (0.9 mole) , and

(ii) in step (A) (b) because the boiling point of octadecene (179° C/29 inches of Hg) differs from that of propylene tetramer the distillation stage required modification. It was necessary to ensure that the temperature of the reactor reached 190°C (29 inches Hg) to expel any unreacted octadecene from the reaction mixture. At this point the distillation stage was complete. Example 2 The procedure of Example 1 was repeated except that instead of using in step (A) (a) a mixture of propylene tetramer (0.9 mole) and octadecene (0.9 mole) there was used a mixture of octadecene (0.36 mole) and propylene tetramer (1.44 moles). Example 3 The procedure of Example 1 was repeated except that instead of using in step (A) (a) a mixture of octadecene (0.9 mole) and propylene tetramer (0.9 mole) there was used a mixture of octadecene (0.18 mole) and propylene tetramer (1.62 moles).

The product of the Comparison Test and of Examples 1 to 3 were analysed in terms of their calcium, sulphur and carbon dioxide contents, their residual ethylene glycol content, alkalinity value and viscosity at 100°C. Additionally, they were subjected to a 35/35 AV compatability test with a highly overbased calcium hydrocarbyl sulphonate. The test is an 'in house' test devised to determine the ability of a package of additives to form homogeneous solutions with base oil by assessing the appearance of the finished lubricant when subjected to a beam of transmitted white light. The appearance and sediment are rated after a fixed period using the tables shown below. Rating

Appearance Sediment

Rating Description Rating Description

1 Clear and bright A Just detectable

2 Slight cloud B Trace (wispy)

3 Moderate cloud C Up to 1.5mm

4 Detectable floe D " " 3.0mm

5 Heavy floe E " " 6.5mm

6 Heavy cloud F " " 13.0mm

7 Light suspension G " " 24.5mm

8 Cotton wool suspension H Over 25.5mm

The results of the analyses are given in the accompanying Table.

It is clear from an examination of the results presented in the Table that the compatability of the products with highly overbased sulphonates is markedly improved by the use of a C₁₂/^C _l8 alkylphenol mixture in the preparation of the phenate.

TABLE

PRODUCT

COMPARISON TEST EXAMPLE 1 EXAMPLE 2 EXAMPLE 3

Calcium (%) 9.60 9.59 9.56 9.03

Sulphur (%) 3.84 3.81 3.79 2.94

Carbon dioxide 5.00 5.10 5.10 5.60

AV (mgKOH/g) 273 262 257 252

Viscosity @ 100C (cSt) 290 220 127 57

Glycol (%) 2.73 2.84 2.53 2.94

35/35 AV ADX 509 (24hrs) 6/5/C 2/-/- 21-1- 21-1-

Claims

Claims:

1. A composition suitable for use as an additive to lubricating oils comprising a mixture of alkaline earth metal sulphurised hydrocarbyl phenates having hydrocarbyl substituents derived from (i) either propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms.

2. A composition according to claim 1 wherein the alkaline earth metal is calcium.

3. A composition according to either claim 1 or claim 2 wherein the hydrocarbyl substituent is derived from propylene tetramer.

4. A composition according to any one of the preceding claims wherein the alkene having greater than 12 carbon atoms is octadecene.

5. A process for the production of the compositions as claimed in claims 1 to 5 which process comprises reacting at elevated temperature an alkaline earth metal base in the presence of a hydroxylic solvent with a mixture of sulphurised hydrocarbyl phenols wherein the hydrocarbyl substituents are derived from (i) either propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms.

6. A process according to claim 5 wherein the mixture of sulphurised hydrocarbyl phenols is obtained by reacting in a preliminary step phenol with a mixture of (i) propylene tetramer or butylene trimer and (ii) at least one alkene having greater than 12 carbon atoms and thereafter reacting the product of the preliminary step with a source of sulphur in the presence of the alkaline earth metal base reactant.

7. A concentrate suitable for incorporation into a finished lubricating oil comprising a lubricating oil and the composition comprising a mixture of alkaline earth metal sulphurised hydrocarbyl phenates as claimed in claims 1 to 4.

8. A concentrate according to claim 7 further incorporating an overbased alkaline earth metal hydrocarbyl sulphonate.

9. A concentrate according to either claim 7 or claim 8 having a TBN in the range from 100 to 300 mg KOH/g.

10. A finished lubricating oil composition comprising a major proportion of a lubricating oil and a minor proportion of a concentrate as claimed in claims 7 to 9.