GB2058118A - Overbased calcium sulphonate production - Google Patents

Description

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GB 2 058 118 A 1

SPECIFICATION

Overbased Calcium Sulphonate Production

The present invention relates to the production of overbased calcium sulphonates and to the overbased calcium sulphonates thereby prduced.

5 Overbased calcium sulphonates which consist of colloidal calcium carbonate dispersed in calcium sulphonate have been known as lubricant additives for some time. They act as dispersants and their basicity neutralises acids formed in the lubricant thus reducing corrosion. One problem with the use of overbased calcium sulphonates in lubricating oils has been that the colloidal calcium carbonate has tended to form haze and sediment in the oil. In addition the materials can be difficult to filter after 10 manufacture.

Various proposals have been made to overcome this problem, for example United States patent 3714042 suggests that the overbased sulphonate be reacted with an aikenyl succinic acid or a derivative thereof. This of course adds to the cost of the overbased sulphonate, requiring an extra reactant and an additional processing step.

15 Overbased calcium sulphonates are generally produced by carbonating mixtures of an oil soluble sulphonic acid or an alkaline earth metal sulphonate, an alcohol, often methanol, calcium oxide and oil. In some processes second solvents, promoters and alkaline earth metal halides are used. Processes for the production of overbased calcium sulphonates are described in British Patent specifications 1299253 and 1309172.

20 We have found that the development of haze and sediment in lubricating oils is due to the morphology of the calcium carbonate. The calcium carbonate present contains both crystalline and amorphous material and it appears that the greater the amount of crystalline material present in the final product the more difficult it is to filter and the greater the tendency for haze and sediment formation.

25 The present invention therefore provides a process for the production of highly basic calcium sulphonates comprising the following steps.

* (i) Forming a mixture of

(a) an oil-soluble sulphonic acid or an alkaline earth metal sulphonate

(b) an aromatic or aliphatic hydrocarbon 30 (c) a C, to C5 alcohol

(d) oil

(e) an excess of calcium oxide over that required to react with the sulphonic acid

(ii) adjusting the water content to between 0.50% and 4% of the weight of excess calcium oxide.

(iii) carbonating the anhydrous mixture of (i) until the pH of the mixture is in the range 6.0 to 7.5 35 or until the Infra-Red Spectrum first indicates the formation of vaterite as shown by a peak at 872

cm-'.

(iv) removing the voiatiles.

Component (a) of the reaction mixture includes oil-soluble sulphonic acids and these may be a natural or synthetic sulphonic acid, e.g. a mahogany or petroleum alkyl sulphonic acid; an alkyl 40 sulphonic acid; or an alkaryl sulphonic acid. The alkyl sulphonic acid should preferably have at least 18 carbon atoms in the alkyl chain. Most suitable are sulphonic acids having a molecular weight of between 300 and 700, e.g. between 400 and 500.

Instead of a sulphonic acid, an alkaline earth metal sulphonate can be used, for example a -calcium sulphonate.

45 Component (a) can be conveniently used as a mineral oil solution e.g. one consisting of 70% by weight by sulphonic acid or sulphonate and 30% by weight of oil.

Component (b) of the reaction mixture is an aromatic or aliphatic hydrocarbon. Aromatic hydrocarbons are preferred, and examples of these are toluene, xylene, and ethyl benzene. Suitable aliphatic hydrocarbons include paraffinic hydrocarbons such as n-hexane, n-heptane, n-decane, n-50 dodecane, white spirit, naphtha, or iso-paraffins.

Component (c) is preferably methanol although other alcohols such as ethanol can be used.

Additional reaction promoters may be used and these may be the ammonium carboxylates such as those described in U.K. Patent 1307172 where the preferred ammonium carboxylates are those derived from C, to C3 saturated monocarboxylic acids, e.g. formic acid, acetic acid, or propionic acid. 55 the preferred ammonium carboxylate is ammonium formate.

Alternatively alkali metal salts of a C, to C3 carboxylic acid may be used the preferred being those of C, to C3 saturated monocarboxylic acids. The preferred alkali metals are sodium and potassium.

As an alternative promoter a metal halide or sulphide may be used. The preferred metals are alkali metals or alkaline earth metals, e.g. sodium, potassium, lithium, calcium, barium, strontium. Other 60 metal nitrates or sulphides which may be used are those of aluminium, copper, iron, cobalt, nickel.

The water content of the initial reaction mixture is critical to obtaining the desired product and must not be more than 4 wt. % and not less than 0.50 wt. % based on the weight of the excess calcium oxide, we prefer to use from 1 wt. % to 3 wt. % based on the weight of the excess calcium oxide. The reactants which are used are therefore preferably anhydrous, and this includes carbon dioxide and any

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GB 2 058 118 A 2

calcium oxide which is added later to the reaction mixture or if not the water level must be adjusted after formation of the reaction mixture to allow for water in the components and also water formed by neutralisation of the sulphonic acid.

The reaction mixture is an oil solution of components (a), (b), (c), and (e), and suitable oils include 5 hydrocarbon oils, particularly those of mineral origin. Oils which have viscosities of 15 to 30 cS at 5

100°F are very suitable. Alternatively other oils which may be used are the lubricating oils which are described later in the specification.

Regarding the quantities of components (a), (b), (c) (d) and (e) it is essential that the volume ratio of components (b) and (c) be between 30:70 and 80:20, otherwise if there is too much of component 10 (b) the resulting product will be greasy, whereas with too much of component (c) there will be 1 o excessive viscosity of the reaction mixture whilst carbon dioxide and any calcium oxide are added.

Preferred volume ratios are between 50:50 and 70:30.

If a promoter is used we prefer to use less than 10%, e.g. between 3.0% and 7.0% by weight based on the total weight of calcium oxide in the reaction mixture, (i.e. including any calcium oxide 15 which is added at a later stage in the reaction). 15

The relative quantities of the other components of the reaction mixture are not so critical, but it is preferred that the weight of component (a) is 40% to 220% of the total weight of oil in the reaction mixture; and that the amounts by weight of components (b) and (c) are each between 30% and 160%

of the total weight of oil, in the reaction mixture. The calcium oxide may be added in several batches 20 but we prefer that the weight of each charge is preferably between 20 and 30% by weight based on 20 the total weight of oil plus component (a).

The carbon dioxide is introduced until the pH of the reaction mixture is in the range 6.0 to 7.5,

preferably 6.5 to 7.0, as is indicated by monitoring with narrow-range pH paper. Alternatively carbonation may be stopped at 872 cm-1 peak in the Infra-Red Spectrum corresponding to the 25 crystalline calcium carbonate and if carbonation is continued without removal of methanol at this point 25 the peak at 872-1 grows rapidly whilst the peak at 865 cm-1 declines to result in a predominantly crystalline product giving haze and sediment problems. The peak at 872 cm-1 tends to appear when the pH of the reaction mixture is in the range 6.5 to 7.0 and we find that if excess methanol is removed at this point and carbonation continued the peak at 865 cm-1 is retained and the final product has 30 peaks at both 865 cm-1 and 872 cm-1 and does not give haze and sediment problems. 30

When the carbon dioxide has been added, if desired further calcium oxide up to the specified maximum quantity may be added and carbon dioxide introduced into the reaction mixture in the same manner as previously. If a sulphonic acid was used initially as the component (a) it will not be necessary to use so much calcium oxide as was originally present in the reaction mixture before the 35 first addition of carbon dioxide. However, in practice, it is convenient to use the same amount of 35

calcium oxide for each charge.

If desired a still further addition or additions of calcium oxide followed by carbon dioxide may be carried out using similar reaction conditions as with the previous addition. Before adding calcium oxide in a further addition step, the carbon dioxide treatment at the previous step should be complete, i.e. the 40 reaction mixture should not be capable of absorbing any more carbon dioxide. 40

After the last treatment with carbon dioxide, the reaction mixture should be heated to an elevated temperature, e.g. above 130°C., to remove volatile materials (components (b), water, and any remaining alcohol) and thereafter filtered, preferably using a filter aid. The desired overbased detergent additive usually having a TBN of 300 or more, is the filtrate.

45 As a further preferred embodiment of the process water is added to the reaction mixture after 45

introduction of carbon dioxide is complete and before removal of the volatile materials. The water is then removed when the other volatiles are removed but we find that this addition of water reduces the tendency of the product to form a skin on storage. ?

As a modification the above described process can be varied by including in the reaction mixture 50 a sixth component (f), and that is a long-chain monocarboxylic acid, or anhydride, or a long-chain di- 50 carboxylic acid or anhydride. By long chain we mean that the molecular weight of the acid is at least 500. Preferred carboxylic acids are those having a molecular weight of between 600 and 3000, e.g.

between 800 and 1800. These carboxylic acids are conveniently derived from a polymer of a mono-olefin, e.g. a C2 to Cs mono-olefin, such as polyethylene, polypropylene or polyisobutene. 55 The quantity of component (f) which is used is preferably 20 to 55 wt. % of the weight of 55

component (a). The combined weight of components (a) and (f) are then preferably 40% to 220% of the total weight of oil in the reaction mixture.

Also as a further modification, to minimise the production of greasy products, the reaction mixture can also include small amounts (e.g. between 4% and 15% by weight of oil) of an alkyl phenol 60 containing at least 7 carbon atoms in the alkyl chain. Suitable examples are n-decyl phenol, cetyl 60

phenol, and nonyi phenol. Alkyl phenols act as copromoters and also enhance the speed of reaction.

The overbased detergent of this invention is suitable for use in lubricating oils, both mineral and synthetic.

The lubricating oil may be an animal, vegetable or mineral oil, for example petroleum oil fractions

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GB 2 058 118 A 3

ranging from naphthas to spindle oil to SAE 30, 40 or 50 lubricating oil grades, castor oil, fish oils or oxidised mineral oil.

Suitable synthetic ester lubricating oils include diesters such as di-octyl adipate, dioctyl sebacate, didecyl azelate, tridecyl adipate, didecyl succinate, didecyl glutarate and mixtures thereof. Alternatively 5 the synthetic ester can be a polyester such as that prepared by reacting polyhydric alcohols such as 5 trimethylolpropane and pentaerythritol with monocarboxylic acids such as butyric acid, caproic acid,

caprylic acid and pelargonic acid to give the corresponding tri- and tetra-esters.

Also complex esters may be used as base oils such as those formed by esterification reactions between a dicarboxylic acid, a glycol and an alcohol and/or a monocarboxylic acid.

10 Blends of diesters with minor proportions, of one or more thickening agents may also be used as 1 q lubricants. Thus one may use blends containing up to 50% by volume of one or more water insoluble polyoxyalkylene glycols, for example polyethylene or polypropylene glycol, or mixed oxyethylene/oxypropylene glycol.

The amount of overbased detergent added to the lubricating oil should be a minor proportion, e.g.

15 between 0.01% and 10% by weight, preferably between 0.1% and 5% by weight. 15

The final lubricating oil may contain other additives according to the particular use for the oil. For example, viscosity index improvers such as ethylene propylene copolymers may be present as may succinic acid based dispersants, other metal containing dispersant additives and the well known zinc dialkyldithiophosphate antiwear additives.

20 The present invention is illustrated but in no way limited by reference to the following Example in 20

which the following charge was placed in the reaction vessel

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Sulphonic Acid

Calcium Oxide

Anhydrous Calcium Chloride

Methanol

Toluene

Oil (solvent 150 Neutral)

grams 89.9 5.2 1.9 41.0 115.9 80.6

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The water of neutralisation and any other water present was removed azeotropically. The reaction mixture was then cooled to below 60°C and 50.6 grams calcium oxide and varying amounts of water added. The mixture was then carbonated at 60°C until the end point as described in the following table was reached.

The reaction mixture was stripped at 150°C liquid temperature to remove the volatiles, 40.1 grams of oil being added during stripping.

The results of reactions as described above but using varying quantities of water are set out below.

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Added Water

% wt. on Excess CaO 0

0.50

1.02 3.06

5.11 7.15

Carbonation End Point pH 6.8 pH 6.8

pH 6.5 C02 breakthroughs 30 minutes pH 7.1 (I.R. showed some vaterite) pH 7.1 (I.R. showed some vaterite)

Filtration USG/hr/ft2

0.2 0.5

1.3 1.0

Very slow

So slow no product obtained

TBN mgKOH/g

271 266

303 297

Kinematic Viscosity (100°C) (Centistokes)

1218

204

Solubility at 5 wt. % in solvent 600 oil clear after 6 days Clear— no sediment after 8 days

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•Almost solid at Room Temperature.

Claims (2)

Claims

1. A process for the production of highly basic calcium sulphonates comprising the following steps.

60 (i) forming a mixture of

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GB 2 058 118 A

(a) an oil-soluble sulphonic acid or an alkaline earth metal sulphonate

(b) an aromatic or aliphatic hydrocarbon

(c) a C, to Cs alcohol

(d) oil

5 (e) an excess of calcium oxide over that required to react with the sulphonic acid. 5

(ii) adjusting the water content to between 0.50% and 4% of the weight of excess calcium oxide.

(iii) carbonating the mixture of (1) until the pH of the mixture is in the range 6.0 to 7.5 or until the Infra-Red Spectrum first indicates the formation of vaterite as shown by a peak at 872 cm-1.

(iv) removing the volatiles.

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2. A highly basic calcium sulphonate whenever prepared by a process according to claim 1. 10

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY,from which copies may be obtained.