GB2232665A - Sulphonic acid derivatives and their use as emulsifiers - Google Patents

Abstract

Sulphonic acids are produced by sulphonating an alkyl aromatic compound in which the alkyl group is linear and contains an average of from 18 to 20 carbon atoms; neutral salts of these acids are useful as emulsifiers in oil in water and water in oil emulsions. Basic metal containing salts, particularly basic alkali and alkaline earth metal salts are used as additives in lubricating oils. These sulphonic acids and metal salts thereof are also claimed per se.

Description

SULPHONIC ACIDS AND THEIR SALTS The present invention relates to improved oil soluble alkyl aromatic sulphonic acids and sulphonates produced therefrom. In particular the invention is concerned with sulphonic acids from which neutral sulphonate emulsifiers and overbased sulphonates especially overbased alkaline earth metal sulphonates which may be used as lubricant additives may be obtained.

Sulphonic acids and sulphonates are generally obtained from mono-alkylates of aromatics the alkyl chain being either branched or straight chain. Oil soluble sulphonic acids are obtained from alkylates containing an alkyl group of more than 16 generally more than 20, carbon atoms, which group is usually branched chain since branched chain olefines are more readily available and cheaper than the corresponding straight chain olefines.

We have now found that sulphonates produced from a particular alkylate are especially useful as emulsifiers in emulsifiable cutting oil formulations and may also be used in the production of overbased alkaline earth metal additives.

The present invention therefore provides a process for the production of sulphonic acids comprising sulphonating an alkyl aromatic compound in which the alkyl group is linear and contains an average of from 18 to 20 carbon atoms.

The invention further provides an alkyl aryl sulphonic acid in which the alkyl group is linear and contains an average of from 18 to 20 carbon atoms.

In a further embodiment the invention provides neutral salts of such sulphonic acids and their use as emulsifiers in oil in water and water in oil emulsions.

In yet another embodiment the invention provides the use of such sulphonic acids as raw materials for the production of basic metal containing additives, particularly basic alkali and alkaline earth metal additives for use in lubricating oils; the invention also provides such basic metal containing additives.

The alkylate itself may be produced by any of the well known alkylation techniques. Our preferred technique being the use of Friedel Crafts catalyst such as aluminium trichloride preferably together with hydrochloric acid. No special conditions are needed for alkylation, our invention being the composition of the olefine feed and the ratios of the material used. In the aspect of the invention concerned with sulphonic acids for producing overbased sulphonates our techniques are particularly useful when the aromatic compound is benzene and toluene.

The ratio of aromatic compound to olefine mixture in the reaction of our invention should be from 10:1 to 1:1 by volume so that an excess of the olefine is not used. This ensures that the products formed are essentially mono-alkyl aromatics which we find to be important since dialkyl aromatics containing a branched chain alkyl group are difficult to sulphonate.

Any of the well known sulphonation techniques can be used to produce the sulphonic acids. For example the alkylate may be sulphonated with concentrated sulphuric acid, with oleum or with sulphur trioxide dissolved in sulphur dioxide, this latter technique being preferred. After sulphonation the sulphonic acid is purified by standard techniques or purifying aids such as the addition of olefines and optionally water as described in our corresponding application U.K. Ser. No. 6775/76 and its U.S. counterpart Pat. No. 4151627 and the ether containing compounds as described in our application U.K. Ser.

No. 5100/75 now U.K. Pat. No. 1469203 corresponding to U.S. Ser.

No. 557396 may be included.

The sulphonic acids may be neutralised to form sulphonates which may be used as detergents dispersants and emulsifiers. The choice of cation will depend upon the use to which the sulphonate is to be put. For use as an emulsifier or in oil recovery the cation will generally be an alkali metal or a quaternary nitrogenic cation, whilst for use as lubricant additives the cation will usually be calcium, barium or magnesium and the sulphonate is often overbased.

Emulsified oils are now used in a large number of machining operations due to an industry demand for higher production rates, lower costs, improved environmental conditions and better operator acceptance. Emulsions are generally used where cooling is more important than lubrication. In operations such as broaching, deep drilling, or where surface finish is particularly critical, neat oils may still be used, but the development of extreme pressure additives in emulsions has increased their applicability and use.

The emulsions are generally prepared from emulsifiable oils supplied to the final user for incorporation into the water. The emulsifiable oils frequently contain additives which can be supplied as an additive package, formulation or concentrate to the producer of the emulsifiable cutting oil.

Amongst the various types of fluids, there is a marked trend towards those having an optimised combination of lubricating, cooling and long-life properties. Such fluids are obtained by micro-emulsification of a base oil formulated with anti-corrosion and biostability agents. The micro-emulsion type of cutting fluid has good stability due to the very small size of their hydrocarbon droplets which do not tend to coalesce during storage. This feature is a key advantage over conventional fluids forming white emulsion whose hydrocarbon droplet size is much larger, where formulation with water-soluble biostability agents is difficult.

Aqueous metal working fluids have been known for many years and different additives have been developed to provide oils useful for different types of metal working and for use with different types of water.

Various emulsifiers have been proposed for the production of water in oil and oil in water emulsions. Typical emulsifiers are the sulphonates, such as the natural and synthetic petroleum sulphonates and the synthetic alkylaryl sulphonates, such as the C12-C24 alkyl benzene and toluene sulphonates and mixtures therefore as described in United Kingdom patent specification 1476891.

Where the fluids are aqueous metal working fluids they may be water in oil emulsions or oil in water emulsions, largely depending upon whether lubrication or cooling is the more important. We are, however, particularly concerned with the currently more popular high water content micro emulsion cutting fluids.

The additives may be supplied to a producer of emulsifiable oils or to the producer of the aqueous fluids. In either instance they may be supplied as a solution or an emulsion of the sulphonates together with other additives for incorporation into oil or the bulk of the water. The solution may be in oil or water and if in oil it will generally contain some water.

The emulsifiable oil supplied to the final user may contain other emulsifiers to enable the production of oil in water or water in oil emulsions and, the choice depending upon the nature of the oil and the type of emulsion required.

Alternatively the final user may introduce the emulsifier into the fluid separately. Salts of the synthetic alkyl benzene sulphonic acids, particularly the mixtures which form the subject of United Kingdom Patent No. 1476891 are our preferred co-emulsifier, other suitable emulsifiers are the sulphonamide carboxylates such as those described in French Patent 2403396 and the sulphonates described in European Patent Application 0015491.

It is preferred that the alkyl groups of the alkylaryl sulfonates are used as co-emulsifiers, branched chain alkyl groups since improved emulsion stability is often found in such cases. Accordingly, it is preferred that at least a proportion of an emulsifier composition is made up of branched-chain alkyl type compounds. Preferably a major proportion, and most preferably all, the composition is of such compounds. Highly preferred are alkylaryl sulfonates derived from benzene and orthoxylene, especially when the alkyl groups are branched-chain, for example, when propylene, butene or isobutylene oligomers are used for alkylation.

We prefer that the emulsifiable cutting oil for incorporation into bulk water contains from 3 to 35 wtt, preferably 3 to 25 wt%, more preferably 7 to 20 wt% of the emulsifier.

Where fluids are to be used for metal working they may be boron free although small amounts of boron may be required for the necessary anti-bacterial properties. Boron may be provided by incorporating boric acid or any other boron compound that forms boric acid upon being dissolved in water, such as metabori acid or boric oxide. It is believed that the boric acid forms an addition product or salt with the amine which is a syrupy liquid and does not precipitate out of the cutting fluid. The emulsifiable oil may contain up to 30 wt% boric acid although we prefer that it contains from 2 to 6 wt% of boric acid to give no more than 1.0, preferably no more than 0.4 wt% boron in the final aqueous metal working fluid.

Other additives which may be present include hydroxy di- or tri-carboxylic' acids which may be used are tartaric and citric acids. It is important that the acid used be soluble in water.

Alkanolamines used in the present invention may also be present in cutting oil formulations using the sulphonates of the present invention, typically those which contain from one to three aliphatic radicals, each containing from one to four carbon atoms, and have at least one hydroxy group attached to a carbon atom, and include primary, secondary and tertiary alkylol amines such as mono-di- or triethanolamine. We prefer that both the emulsifiable oil and the aqueous fluid contain an excess of alkanolamine relative to total acid content.

A coupling agent such as a non-ionic wetting agent is generally used in aqueous metal working fluids embodying the invention. To improve the compatibility of the components, any desired non-ionic wetting agent may be used, such as a condensation product of ethylene oxide; a condensation product of a fatty acid or derivative, such as a derivative of à fatty acid, fatty alcohol, fatty amide or fatty amine, with ethylene oxide; and a reaction product obtained by the condensation of an oxyalkylaryl compound, such as a derivative of an alkylphenol or alkylnaphthol, with ethylene oxide. It is preferable that the non-ionic wetting agent employed be water-soluble.Typical non-ionic wetting agents include the polyethoxyesters of fatty acids, the monooleate of a polyethylene glycol, the monolaurate of a polyethylene glycol, the polyethoxyethers of fatty alcohols, the condensation product of an alkylphenol such as dodecyl phenol with 12 moles of ethylene oxide, and the sulfonated product of the condensation of an alkylphenol or an alkylnapthol with ethylene oxide.

A particularly useful non-ionic wetting agent is an alkyl phenoxy polyethyoxy ethanol such as octyl or nonyl phenoxy polyethoxy ethanol.

We also find, particularly when emulsifiers other than sulphonic acids and sulphonates are used that carboxylic acids such as neo acids and fatty acids may be included to enhance emulsion production. The amount required depends on the other components present but typically 2 to 10% based on the hydroxy di- or tri- carboxylic acid or 10% to 30% if boric acid is also present.

Other ingredients which may be incorporated in the aqueous fluids include silicone anti-foaming agents and biocides.

Metal containing additives for lubricants may also be obtained from the sulphonic acids of this invention and may be present in the neutral or slightly basic or highly basic forms.

The metals are usually alkali or alkaline earth metals, for example, Na, Li, Ca, Mg, Ba. The most commonly used are Ca or Mg, or mixtures of Ca and Mg or mixtures of Ca and/or Mg with Na.

The metal compounds which may be used in neutralising the alkaryl sulphonic acids to provide the sulphonates include the oxides, hydroxides and alkoxides, for example, calcium hydroxide or magnesium oxide. hydrocarbon solvents and/or diluent oil might also be included as well as neutralisation promoters and viscosity control agents, such as formates and halides. These additional materials are particularly useful when an excess of metal base is used to give a slightly basic salt. These slightly basic sulphonates may have a total base number (TBN) of 0 to about 50 mg KOH/g and may contain diluent oil.

The highly basic metal sulphonates are usually produced by neutralising an alkaryl sulphonic acid with a large excess of metal base over that required for complete neutralisation and thereafter forming a dispersed carbonate complex by reacting the excess metal base with carbon dioxide to provide the desired overbasing. Neutral or slightly basic metal sulphonate may be used in place of the alkaryl sulphonic acid.

The reaction mixture may include organic solvents for example, toluene, xylene, hexane, chlorobenzene, and other materials, for example, alcohols, water, amines, salts of organic or inorganic acids, which serve to promote the overbasing process, and diluent oil. Volatile materials and undispersed solids are removed in the final stages of the process. Processes which use a metal alkoxide as the starting metal compound can proceed by a somewhat different route in which carbonation of the alkoxide to give an alkoxide carbonate complex is followed by hydrolysis of the complex to give the metal carbonate. These reactions may be carried out in the presence of alkaryl sulphonate, solvents and diluents.

Highly basic metal sulphonates may have a TBN from about 50 to about 500, preferably 250 to 450 and contain about 10 to about 35 wt% alkaryl sulphonate. The following patents provide illustrative examples: EP 0,000,264, EP 0,000,318, EP 0,025,328, EP 0,047,126, EP 0,121,024, EP 0,015,341, EP 0,013,807, EP 0,013,808, EP 0,212,922.

The production of the sulphonic acid of the present invention is illustrated by the following Example: 100g of an alkylate composition believed to be obtained by condensing a chlorinated linear C18-C20 paraffin onto benzene to give a mixed product having the following composition and properties Phenyl C17 8.3 wt% = C18 38.5 wt% = C19 21.9 wt% = C20 5.0 wt% = C21 0.6 wt% Total phenyl isomers 74.3 N-paraffins C18-21 1.1 Polyakylbenzene-diphenyl 20.0 Tetralines isomers 4.6 Total 100.0 Average molecular weight 334 Pour point deg C -15 Viscosity cSt at 40 deg 14.5 density at 15 deg C Kg/m3 863 Flash point PMCC deg C 174 bromine number g/100g 0.2 were blended with 30 g of liquid S02 under reflux conditions at - 10 C.

24 g of 503 were then poured into 54 g of S02 at -15 C; this mixture is added over a period of 15 minutes into the alkylate diluted with as described above S02. During sulphonation temperature is maintained at - 10 C 15 minutes after end of S03 addition temperature is progressively increased to 1300C to remove SO2; when the temperature is about 100 C 2.5 g of olefin (mw 335) are added in order to reduce most of unreacted 503 The composition of the sulfonic acid obtained is (mass pct) active ingredient 90 with a molecular weight of 445 sulfuric acid 0.2 water 0.3 non sulfonated 9.5 Neutral sodium sulphonates obtained from these sulphonic acids were used as emulsifiers for cutting oils.The cutting oils are obtained by blending the sodium sulphonate with or without a co-emulsifier, with a coupling agent and by blending the mixture with a base oil. Other co-additives can be introduced to the cutting oil include : corrosion inhibitors, white/yellow metal passivators, defoamers, extreme-pressure, antiwear or lubricity agents, biocides or biostatic agents, additives yielding alkalinity reserve.

Typical formulations are given hereunder. Two sulphonates of the invention have been used: sulphonate A (hereinafter "(A)") and sulphonate B (hereinafter "(B)").

(A) is the sodium salt of an average linear C18 monoalkylbenzenesulphonic acid mixed with 6-10 mass% of monoalkyl diphenylsulphonate and 10-12 mass% of dialkylbenzenesulphonate.

(B) is also the sodium salt of an average C18 alkylbenzenesulphonic acid but mixed with 40 mass% of Cl0-C15 monoalkylbenzenesulphonate, 60 mass% of dialkylbenzenesulphonate, with alkyl chain lengths from C10 to C18.

Formulations (1) to (6) are milky emulsion concentrates containing a sulphonate, another sulphonate used as a co-emulsifier to match the hydrophilic balance of the baseoil and the co-additives, ECA 6427, an additive package giving anticorrosion performance, and butyl carbitol, a coupling agent.

(1) (2) (3) (4) (5) (6) --- --- --- --- --- -- Synacto 406 13.4 - - - - Synacto 416 - - - 10.4 - (A) - 13.4 - - 10.4 - (B) - - 13.4 - - 10.4 Synacto 476 2.4 2.4 2.4 - - Synacto 246 - - - 5.4 5.4 5.4 ECA 6427 2.0 2.0 2.0 2.0 2.0 2.0 water 0.8 0.8 0.8 1.0 1.0 1.0 Bu carbitol 2.6 2.6 2.6 2.6 2.6 2.6 Nynaes T 22 78.8 78.6 78.6 78.6 78.6 78.6 Nynaes T 22 is a naphthenic base oil.

Synacto products are commercially available from Exxon Chemical.

These additive packages were mixed with oil in the proportions specified below and tested.

Performance (1) (2) (3) (4) (5) (6) Appearance ............... milky white (4 vol. pct) oil O 0 0 0 0 0 cream Appearance after 24hrs ............... milky white ...............

oil trace 0 0 trace 0 0 cream 0 0 0 0 0 trace Corrosion IP 287, (4 vol. pct) surface stained, pct 75 75 75 75 75 75 Corrosion IP 125 0/1-2 0/5-3 0/5-3 0/1-2 0/5-3 0/5-3 (1.5 vol. pct) The emulsions were prepared in local tap water (250 ppm hardness expressed as CaC03 equivalent) The advantage of using the products of this invention is the flexibility of formulation. The formulations given above show that two sulphonates of very different molecular weights can be directly substituted by the sulphonates of the invention. This is evidenced by comparing formulations (2) and (5). The two formulations yield perfectly stable emulsions. (2) contains 13.4 pct (A) and 2.4 pct of Synacto 476 an hydrophilic low molecular weight (380) sulphonate, and (5) contains 5.2 pct (A) and 5.4 pct of Synacto 246, a high molecular weight (520) sulphonate.

The formulations made with sulphonates (A) and (B) are less sensitive to changes in hydrophilic/lipophilic variations the oil and of the co-additives.

Claims (5)

1. A process for the production of sulphonic acids comprising sulphonating an alkyl aromatic compound in which the alkyl group is linear and contains an average of from 18 to 20 carbon atoms.

2. An alkyl aryl sulphonic acid in which the alkyl group is linear and contains an average of from 18 to 20 carbon atoms.

3. Neutral salts of a sulphonic acid according to claim 2.

4. The use of a neutral salt according to claim 3 as an emulsifier in oil in water and water in oil emulsions.

5. Basic metal containing additives, particularly basic alkali and alkaline earth metal additives for use in lubricating oils obtained from a sulphonic acid according to claim 3.