CA1067092A - Unsymmetrical sulfosuccinate diesters - Google Patents

Abstract

UNSYMMETRICAL SULFOSUCCINATE DIESTERS

Abstract of the Disclosure Unsymmetrical sulfosuccinate diesters in which one carboxyl group of the sulfosuccinate is esterified with an alcohol, for instance, a C8-C12 aliphatic monohydric such as octyl or dodecyl alcohol, or with an ethoxylated or propoxyl-ated alkyl phenol, and in which the other carboxyl group is esterified by reaction with an .alpha.-monoepoxide such as propylene oxide, or higher .alpha.-epoxides, and method of preparation of such diesters. The said diesters have utility as surfactants, such as detergents and emulsifiers.

Description

Our invention relates to the preparation of certain types of novel unsymmetrical sulfosuccinate dlesters at least most of which can be represented by the followinc, formula:

R--O--C--CH CH2--C-O--( R10) H ( I ) where R-O~ is the radical of a Cl-C20 aliphatic monohydric alcohol, or of an ethoxylated or propoxylated alkyl phenol in which there are not more than 2 nuclearly attached alkyl groups each containing from 5 to 12 carbon atoms and in which the number of ethoxy (-C2H40) or propoxy (-C3H60) groups is from 1 to 6; and R O- is the radical of an a-monoepoxide (hereafter called ~-epoxide) radical containing from 3 ta 20 carbon atoms;

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:~ ; , . ~ -2 106~092 with the proviso that the sum of the number of carbon atoms in R and Rl is from 7 to 35 and that there is a difference in the number of carbon atoms in R and Rl which difference is at leàst

2; and M is a cation selected from the group of alkali metals (including ammonium), alkaline earth metals, and organic sub-:i stituted ammonium or amines. Most desirably, the difference in the number of carbon atoms between R and Rl is from 4 to 14.
Again, most desirably, in the novel compounds of our present invention, R is alkyl containing from 8 to 15 carbon atoms and Rl contains 3 carbon atoms.
; ~ ' : It is particularly desirable that the novel sulfo-:succinate compounds of our present invention be marketed and used in the form of the aforementioned types of salts, that is, where M in formula (l) is an alkali metal (which term is here `; used to mean sodium, potassium, lithium and ammonium), or alkaline earth metals, namely, calcium, magnesium, strontium ~ and barium; or, as noted above, organic substituted ammonium ;1 or amines. These latter, which most advantageously are water-1:
soluble lowerlmolecular weight amines, may be selected from a wide:group~ typical examples of which are dimethylamine;
diethylamine; triethylamine; propylamine; monoisopropylamine, diisopropylamine, triisopropylamine, and commercial mixtures of said isopropylamines; butyl amine, amyl amine; monoisopro-panolamine, diisopropanolamine, trLisopropanolamine and ` commercial mixtures of said isopropanolamines; ethanolamines such as monoethanolamine, diethanolamine, triethanolamine, and commercial mixtures thereof; polyamines such . . . . .

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~ 3 ~06709Z

as aminoethyl ethanolamine, ethylenediamine, diethylenetriamine, hydroxyethyl ethylenediamine, and hexamethylenediamine; hexyl-amine; cyclohexylamine; dimethylbenzylamine, benzylamine;
morpholine; etc. Such salts can be prepared from sodium or potassium salts of the novel sulfosuccinate compounds of our present invention by known metathesis techniques.

The aforesaid unsymmetrical sulfosuccinate diesters are characterized by the fact that there is present in the molecules thereof, connected through one ester linkage to one of the carboxyl groups of maleic anhydride, a free hydroxyl group in the ~-position resulting from the utilization of an ~-epoxide containing at least 3 carbon atoms in the production of the compounds of our invention, all as is hereafter described in detail and illustrated by the various disclosed embodiments of our invention. The special combination of radicals in the , compounds of our inventions results in pàrticular properties which effectively adapt various of the compounds to particularly effective utilities in various environments.

In the usual case, the radical R-O- in formula (I) will be derived from a long chain aliphatic monohydric alcohol, or an ethoxylated or propoxylated alkyl phenol containing a nuclearly attached alkyl group or groups each having a chain of from 5 to 12 carbon atoms, and the radical R10- in said formula (I) will be derived from an~-epoxide such as propylene oxide or butylene oxide, particular propylene oxide. However, as has been indicate

- 3 -~ -4 ~067092 , compounds according to our invention are also obtained where the R-O- radical of said formula (I) is derived from a Cl-C3 aliphatic monohydric alcohol such as methanol, ethanol or propanols, and the R10- radical is derived from a C8-C12 or C8-C20 a-epoxide such as octylene oxide or dodecylene oxide or styrene oxide.
.~

Particularly preferred embodiments of the novel com-pounds of our invention comprise unsymmetrical sulfosuccinate diesters one carboxyl group of the sulfosuccinate of which is esterified with a C8-C20 aliphatic monohydric alcohol, and the other carboxyl group of the sulfosuccinate of which is reacted with propy]ene oxide to form a propylene glycol ester group.

The aforesaid compounds are useful in various fields ~ where surfactant or wetting-out properties are a desideratum I such as, for instance, detergents, emulsifiers, penetrating agents, stabilizing agents, dispersants, emollients, and the like Sulfosuccinate surfactants and, more specifically, sulfosuccinate diesters, are known to the art, being disclosed, for instance, in U. S. Patents Nos. 2,028,091; 2,507,030;
2,887,504; 3,002,994 and 3,481,973. However, so far as we are , aware, there has been no prior suggestion or disclosure of any of the compounds of our invention.

In the preparation of the novel compounds of our in-vention, maleic anhydride is initially reacted with an aliphatic (which term includes cycloaliphatic) monohydric alcohol, or 1067Q9Z -s with an ethoxylated or propoxylated alkyl phenol, in proportions such as to produce predominately the maleic'acid monoester.
Generally speaking, a mole ratio of 1 to about 1 2 moles of maleic anhydride to 1 mole of the aliphatic monohydric alcohol or of the alkyl phenol or of the ethoxylated or propoxylated alkyl phenol results in the production of a'reaction product which contains upwards of 90 or 95% of the monoester. It is generally unnecessary to purify the reaction product to separate the monoester but this can be done, if desired, by conventional purification techniques.

. , .
¦ In a particularly preferred procedure for the production ~' of the monoester, particularly where the alcoholic reactant with the maleic anhydride is an aliphatic monohydric alcohol, such as, for instance, long chain aliphatic monohydric or fatty alco-hols, said alcohols are initially admixed with a small proportion ~I commonly from about 0.05 to 0.5%, by weight of said alcohol, of , an inorganic hydroxide or a basic catalyst, such as sodium hydrox-,~
ide or potassium hydroxide in strong aqueous solution, and heated to a somewhat elevated temperature, for'instance about 109-115C
under vacuum while purging with an inert gas, such as nitrogen, , .
`
argon or helium, whe'reby to remove all or essentially all water from the system, after which the vacuum is released and the alcoholic reactant, at the selected temperature, is admixed with the maleic anhydride and reacted, for instance, at about 70 to about' 100C, until the acid number reaches or approximates that of the desired monoester or half ester. To said monoester is then added the selected ~-epoxide to drive the reaction to com-' _ 5 _ , ~6 ~06709Z

pletion which, in the usual cases, involves the employment ofabout 0.2 to 0.3 moles excess to effect completion of the reaction in a reasonable length of time. To the resulting unsymmetrical diester there is then added slightly more than i mole of the bisulfite per mole of maleic anhydride used and the resulting mixture is heated until the reaction is complete. It should be noted that, in the preparation of the novel compounds of our present invention, whether by the preferred procedure described in this paragraph or otherwise in accordance with our invention, it i8 essential that maleic anhydride be utilized.

~ .
In the pr~paration of those of the compounds of our invention which are in the form of amine salts, it is sometimes desirable to produce such in substantially anhydrous form, soluble I ~ in organic solvents, particularly polar organic solvents such ` as ethyl alcohol, propyl alcoholi isopropyl alcohol, methyl and ethyl formamides, etc. To this end, for instance, the afore-.;, , .
,I descrlbed diesters can be reacted with a soIution containing an organic amine, sufficient water to provide a reaction medium and containing dissolved sulfur dioxide to form a sulfite of said organic amine, and a water-miscible alcohol, for instance, methyl alcohol, ethyl alcohol, n-propanol or isopropyl al~ohol, whereby to produce a substantially anhydrous organic amine salt of the said sulfosuccinic acid diesters. For best results, in carrying out such reaction, for each mol of said diester, the solution reacted therewith should contain about 1 mole or slightl~
more of organic amine or amines, and about 1 mol of water con-taining about 1 mol of sulfur dioxide.

_ 6 ~ 7 ~Q67092 .
: . In the preparation of the novel compounds o our in-vention by the foregoing method, is important, in order to obtain :~ said compounds, that the sequence of steps noted above be followed :~ that is, .that the maleic acid monoester of the Cl-C20 aliphatic monohydric alcohol, or of the ethoxylated or propoxylated alkyl 1: :
~ phenol, first be provided or prepared after which the reaction ,~ ~
with the~ -epoxide is carried out, followed by the reaction with ~; the~aqueous bisulfite to introduce the sulfonic group i~to the molecule. Thus, for instance, if the ~-epoxide is first reacted ;with the maleic anhydride and then with (a) the Cl-C20 aliphatic monohydric alcohol or ethoxylated or propoxylated alkyl phenol, followed~by the reaction with the aqueous bisulfite, or (b) the aqueous bisulfite followed by the reaction with the Cl-C
. ~ aliphatic monohydric alcohoil or the ethoxylated or propoxylated " ~
; alkyl phenol, the.products of or contemplated by the present ; invention are not obtained.

In:the reaction of the monoesters with the ~-epoxides containlng:at least 3 carbon atoms-to produce the intermediate ~ :diesters~ ich are then converted into the unsymmetrical sulfosuc-!: : ~ .
~ : :cinate esters of our invention, said reaction is especially '' 1 ' ~ ~ ' ~ ' ' désirably carried out in the presence of a catalyst, particularly a basic inorganic or organic material such as, by way of example, sodium hydroxide, potassium hydroxide, sodium carbonate, potas-~ sium carbonate; tertiary amines such as triethylamine and tri-;,il~ isopropylamine, and quaternary ammonium salts such as tetramethyl :~i: ~ .~ ammonium hydroxide, tetraethyl ammonium hydroxide, benzyl tri-:: .

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~0 6 7 0 9 2 -8 methyl ammoniurn hydroxide and benzyl triethyl ammonium hydroxide.
Such catalysts can be used in variable proportions, generally in the range of 0.1 to 2 or 3%, based on the weight of the monoester, depending generally on the basicity of the catalyst.

No novelty is claimed ln the monoesters of maleic an-hydride with certain of the alcohols as such, namely with Cl-C10 aliphatic monohydric alcohols, since such compounds and various procedures for their preparation are known to the prior art, and the same is true with respect, per se, to certain of the reaction products of such half esters or monoesters with ~-epoxides such aæ ethylene oxide and propylene oxide.

,, .
The radicals represented by R-O-in formula (I) can be derived from straight chain or branch chain aliphatic monohydric alcohols ha~ing the formula RlOH where R10-is the radical of a Cl-C20 aliphatic monohydric alcohol, or of an ethoxylated or , propoxylated phenol in which there are not more than 2 nuclearly attached alkyl groups each contai~ing fro~ 5 to 12 carbon atoms and in which the number of ethoxy (-C2H40) or propoxy (-C3H60) groups is from 1 to 6.

The radicals represented by RO- in formula (I) or by R 0- in the formula RlOH can be straight chain or branch chain and include, by way of illustration, radicals derived from such alcohols as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, cyclohex-anol, n-amyl alcohol, isoamyl alcohol, n-hexyl alcohol, isohexyl _ _ . . _ . .... _ . _ .

- ~067Q92 alcohol, 2-ethyl hexyl alcohol, 2-ethyl octyl alcohol, n-nonyL
alcohol, isononyl alcohol, n-decyl alcohol, isodecyl alcohol, undecyl alcohol, n-dodecyl alcohol, isododecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl al-cohol, heptadecyl alcohol and octadecyl alcohol,-and mixtures thereof as in commercial mixtures of fatty and other alcohols;
oxo alcohols such as the primary monohydric saturated aliphatic C1o-C20 alcohols as, for instance, oxo tridecyl alaoho~ and oxo hexadecyl alcohol (see U. S. Patent No. 2,965,678), and they can be derived from grain sources, fatty triglycerides, and petroleum sources including kerosene fractions and polymerized olefins such as polypropylenes, for instance, propylene trimers and tetramers, from oxo alcohol proaedures, and by Ziegler catalytic and other chemical procedures. Also included in such aliphatic monohydric alcohols are those derived by adducting 1 mole of such alcohols as octyl, decyl and dodecyl alcohols, or analogous branched chain alcohols, with 1 to 4 moles of ethylene oxide, or by adducting 1 mole of such alcohols as hexyl, octyl, decyl or dodecyl alcohols, or analogous.branched chain alcohols, with from 1 to 4 moles of propylene oxide.

Where R-O- ln formula (I)~ or R10- in the formula RlOH
is the radical of an ethoxylated or propoxylated alkyl phenol in which there are not more than 2 alkyl groups each containing from 5 to 12 carbon atoms, said alkyl phenol radicals can con-veniently be represented by the formula .

g _ - (OR )yO~ (~II) (R )n where R2 and R3 are the same or dissimilar C5-C12 alkyl radicals, R4 is a Cl-C3 alkyl radical, R5 is C2H4 or C3H6; each of w,m and n is zero to 1, subject to the proviso that, when w is zero, m is 1 or 2; and y is 1 to 6.

Illustrative examples of such ethoxylated and propoxy-, lated alkyl phenols from which compounds of our invention can be prepared are the adduct of 1 mole of octyl phenol with 2 moles of ethylene oxide; the adduct of 1 mole of nonyl phenol with 3 moles of ethylene oxide; the adduct of 1 mole of nonyl phenol with 1 mole of propylene oxide; th`e adduct of 1 mole of diamyl phenol with 3 moles of ethylene oxide; the adduct of 1 mole of dodecyl phenol with 2 moles of ethylene oxide; the adduct of 1 mole of dioctyl phenol with 2 moles of propylene oxide; the adduct of 1 mole of dinonyl phenol with 3 moles of ethylene oxide;
the adduct of 1 mole of nonyl toluene with 2 moles of ethylene oxide; the adduct of 1 mole of isopropyl nonyl phenol with 2 moles ofethylene oxide; and the adduct of 1 mole of dinonyl isopropyl phenol with 3 moles of ethylene oxide.

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The DC-epoxides which are utilized in the preparation of the novel compounds of the present invention and from which the radical R10- of formula (1) is derived include, by way of illus-trative examples, propylene oxide; butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, dodecylene, tetradecylene ~)67092 pentadecylene, hexadecylene and octadecylene oxides, as well as styrene oxide and similaro~-epoxides derived from analogous alkenyl benzenes.

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Illustrative examples of chemical compounds falling within the scope of our invention are the following:

(I) C12H25--C-CH- CH2-C-O-cH2 !CH 3 O SO Na 0 OH

~ ' : ' ' ' ' ' '' ' 15 31 1! I CH -C-O-CH -CH-CH
O S03K O OH.

;~ (3) CgH17--C-CH CH -C-O-CH2-CH-CH2-CH3 l ~ 3 OH
.'1, ' .
12 25 ll l 2 11 2 1 3, O S03H-N(C2~40H)3 o OH
, ~, , ' ', .

(5) Cl4H29--l-fH~ _ CH -C-O-CH2-'CH-cH3 - .
O SO NH O OH

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.

``` -12 ~067092 (6) Cl H -O-C~CH CH2-C-O-CH2-CH-(CH2)2-CH
0 S03Na O OH

, (7) C12H25-0-C2H4-o-cj-fH - CH -C-O-CH -CH-CH
O S3Na OH-- 12 25 1I f CH-C-CH2- IcH-cH3 3H.,H2N_HC=(CH3) o OH

14 29 (0c2H4)2-c2H4-o-c-cH CH2-C-O-CH -fH-CM3 . O SO Na O OH .

(10) C15H31 (OC2H4) -C2H4-0-C-fH CH2-C-O-CH2-CH-CH3 O S03Na 0 ON

(11) C8H17 (0C3H6) 3--cH2--fH--cH2--o--lcl--cH--cH2--c--o--cH2--cH--cH3 OH O so3Na O 0 (12) CH3-0-C-fH --CH2-C-O-CH --O SO Na O OH-(13) C H -O-C-fH ¦I f . O S03Na O 011 (14) C H -O-C-fH - CH -C-O-CII -CH-(CH ~ -CH
O S03Na O OH

~ -13 ` ~ 1067~92 15) C12H2 ~ -O-C3H6-O-C-fH CH2-C-O-CH2-CH-CH3 O SO3Na O OH

16) CgHl ~ -O-C H -O-C-CH CH2-~-O-CH2-1CH-CH3 O SO3Na O OH
, 17) C12H2 ~ 2 4( 2 4)32 4 11 1 -; CH2-1CI-O-CH2-CH-CH3 ;~ O OH
;~ ~
18) CgHl ~ -O-C H -O-f-fH CH2-~C-O-CH2-fH-CH3 -T-- O SO K O OH
~l 3 .~
The following examples are illustrative of the pre-paration of typical compounds of the present invention. A11 temperatures recited are in degrees Centigrade.

EXAMPLE I:
(a) To 1242g (6.06 moles) of "NEODOL 25" (a commercial product consisting mainly of a mixture C12-C15aliphatic mono-hydric alcohols having an average molecular weight of about 205) are added 1.4g of KOH in 3 ml of water, and the mixture is heated o to about 105 under a vacuum 25mm. of Hg while purging with gaseous nitrogen, and then held at such temperature for about 1/2 hour. It is then cooled to about 75, the vacuum is released and to it is added 600g (6.12 moles) of maleic anhydride, and the reaction mixture is maintained at about 75 for approximately * trade mark :1~67Q92 2 hours at the end of which time the acid value is 3.47 meq/g, `~ indicating formation of the maleic acid monoester of said mix-. . .
ture of alcohols.
(b) The monoester produced in part (a) hereof is placed in an autoclave heated to 100 and to it is added 456 g (7.85 moles) of propylene oxide over a period of 5 hours, at the end~of which time the acid value is 0.001 meq/g. The resulting di-ster contains, in the molecule, approximately 2-L.: 3~oxypropylene or~propoxy groups.
(c)~To~the dlester produced in part ~b) hereof there 18;addod~600 ml of~water and~1530 g of 42% aqueou,3 sodium bifiulfate~solution ~`(6;.18~moles)~and heated to 90. An almost immediate~exother~mLc reaction occurs~and the pressure in the autoclave rise8 to of the~order of 5~to~10 pounds per square inch. The reaction~is~complete in about 1/2 hour. A somewhat vi8co~u,s;, light yellow~solution is obtained containing approx-imately 0.5% free sodium~su}fite and 67%~solids. On the basis of~the~ 801ids content~, the~sulfosuccinate surfactant produced sh ~s tAe~following;~propeeties~

'Wëight '~In Water~Solution Draves Wetting Test Slnk Time-Séc~,nds 0.168 0 335~ 12 e surface tension of a 0.05% water solution is 32.1 d nes/cm.~

~ 14 -`'l :
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1()6709?
EXAMPLE II:
A To SOOg (3.7 moles) of "ALFOL 610" (C6-C10 synthetic alcohol, mean mol.wt. 136) is added lg of NaOH dissolved in 2ml of water, and this mixture is heated to 85 in vacuo for 1/2 hour. To it is then added 361g (3.7 moles) of maleic anhydride at 70 and the resulting reaction mixture is maintained at this temperature for 1 hour. At the end of this period, the acid ; value is 4.25 meq/g. The resulting monoester is placed in a stirred autoclave heated to 100 and to it is added 285g (4.9 : , moles~ of propylene oxide over a period of 2 hours at 3bpsi - pressure, then stirred an additional 3 hours at this temperature.
At this point the pressure in the autoclave is about 10 pounds 1::: .
l ~ per square inch. The acid value of the diester, which contains, i .
~ .
in tbe molecuie, approximately 1.3 propoxy groups, is 0.01 ~ ~; meq/g. The said diester is stripped in vacuo at 9S-100 and 1 `: `, to it~at this temperature is added 970 g.of a 40% aqueous sodium bisulfite solution (3.7-moles) over a period of 1 hour, and to thls solutLon is then added 345ml of 95 water. The final sulfosuccina~te product is a mobile liquid at room temperature which iS completely soluble in water.

EXAMPLE III:
To 316g ~2.02 moles) of the isopropyl alcohol monoester o~ maleic anhydr:ide is added 0.5g of sodium methylate and 300g (2.17 moles) of a technical yrade 1,2-octene oxide (M W. 136) having an epoxide content of 7.25 meq/g. The reaction mixture is heated to 100 for 10 hours, at the end of which period the .i .
6rrk .

~~ . 1~7092 -16 acid value is 0.05 me~/g. The resulting diester lS stripped at Looo and 0.1 mm pressure, and to it is added 550g. of a 42%
-aqueous sodium bisulfite solution (-2.22 moles) at 100. After 1 hour, the reaction is complete and an additional 500 parts of 95 water is added. The final sulfosuccinate productfiis a clear, slightly amber, solution, which is completely miscib~e with water.

. . . .

;1 EXAMPLE IV:

~I To 400ml of water are added 34g of the sulfosuccinate surfactant prepared in Example II, 1.25g of potassium persulfate, 7g of hydroxyethyl cellulose ~"Cellosize~WP-09", Union Carbide Corporation), and 1.3g of sodium bicarbonate. This solution is heated to 70 and to it is added at 70-75, in separate streams, ~ over a period of 4 hours, 550g of vinyl acetate and a solution !
of 1.25g of sodium persulfate in 50ml of water. When the addition is complete, the temperature is raised to 90 for 1/2 , .
hour. The resulting vinyl acetate latex contains 55% solids I andlshows no separation after standing for 6 months.

EXAMPLE V:
The sulfosuccinate surfactant product of Example III
is used in an emulsion polymerization process as described in Example IV with similar results.

.J
EXAMPLE VI:
The procedure described in Example I is carried out except that, in part (a), in place of the 1242g of "~EODOL 25,"

~r~ ?arks .

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` 1067092 there is used 1664 g (6.06 moles) of an adduct of 1 mole of nonyl phenol with 1.2 moles of ethylene oxide. The balance of Example I is carried out using the same amounts of the specified in-gredients. The sulfosuccinate product obtained corresponds essentially to the formula ~;

A 9 19~--o--c H ~O--C-CH--CH2--C--O--CH2-CH--CH3 O S03Na O OH

EXAMPLE VII:
The procedure described in Example II is carried out except that, in place of the 500 g of "ALFOL 610", there is used ,.
,~ 1133 g (3.7 moles) of an adduct of 1 mole of nonyl phenol with 2 moles of ethylene oxide. The sulfosuccinate product obtained corresponds to the formula CgHl~ 2 4 2H4 O oC Cl H CH2--CI--O--CH2-CH--CH,3 O SO3NaO OH

i EXAMPLE VIII:
j , .
The procedure described in Example II is carried out except that, in place of the 500 g of "ALFOL 610", there is used , 482 g (3.7 moles) of 2-ethyl hexanol. The sulfosuccinate product ' obtained, containing 69.6% solids, has a critical micelle con-centration of 1. 2% which renders it especially desirable for use in emulsion polymeriza~ion procedures such as are shown in Example IV above.

~r~e~arks .

.. , , . . .... , . , . , . _ ., ...... . _ _ .. , .. _ .. , . . , . . _, ... . .

Claims (14)

We claim:

1. An unsymmetrical sulfosuccinate surfactant accord-in to the formula where R-O- is the radical of a C1-C20 aliphatic monohydric alcohol, or of an ethoxylated or propoxylated alkyl phenol in which there are not more than 2 nuclearly attached alky groups each containing from 5 to 12 carbon atoms and in which the number of ethoxy or propoxy groups is from 1 to 6; and R1O- is the radical of an.alpha.-epoxide containing from 3 to 20 carbon atoms;
with the proviso that the sum of the number of carbon atoms in R and R1 is from 7 to 35 and that there is a difference in the number of carbon atoms in R and R1 which difference is at least 2; and M is a cation selected from the group of alkali metals, alkaline earth metals and organic substituted ammonium.

2. A surfactant according to claim 1, in which the difference in the number of carbon atoms between R and R1 is from 4 to 14.

3. A surfactant according to claim 1, in which R is alkyl containing from 8 to 15 carbon atoms and R1 contains 3 carbon atoms.

4. A surfactant according to claim 3, in which R is a straight chain.

5. A surfactant according to claim 3, in which, when R contains from 3 to 18 carbon atoms, it is branch chain.

6. A surfactant according to claim 1, in which R-O- is where R2 and R3 are the same or dissimilar C5-C12 alkyl radicals, R4 is a C1-C3 alkyl radical, R5 is C2H4 or C3H6, each of w,m and n is zero to 1, subject to the proviso that, when w is zero, m is 1 or 2; and y is 1 to 6.

7. A surfactant according to claim 1, in which R-O- is where R5 is C2H4, and y is 1 to 6.

8. A surfactant according to claim 1, in which R is a C1-C3 alkyl radical, and R1O- is an .alpha.-epoxide radical containing from 8 to 12 carbon atoms.

9. A method of preparing certain unsymmetrical sulfosuccinate surfactants which comprises (a) reacting maleic anhydride with (b) a monohydric alcohol having the formula ROH
and in which RO- is the radical of a C1-20 aliphatic monohydric alcohol, or of an ethoxylated or propoxylated alkyl phenol in which there are not more than 2 nuclearly attached alkyl groups each containing from 5 to 12 carbon atoms and in which the number of ethoxy or propoxy groups is from 1 to 6, in proportion to produce predominately the monoester of said alcohol, (c) reacting said monoester, in the presence of a basic catalyst, with an a-epoxide having the formula R1OH and in which R1O- is the radical of an .alpha.-epoxide containing from 3 to 20 carbon atoms to produce the corresponding diester, and (d) then reacting said diester with an aqueous solution of a bisulfite to convert said diester to an unsymmetrical sulfosuccinate surfactant.

10. The method of claim 9, in which the difference in the number of carbon atoms between R and R1 is from 4 to 14.

11. The method of claim 9, in which R is alkyl containing from 8 to 15 carbon atoms and R1 contains 3 carbon atoms.

12. The method of claim 11, in which R is a straight chain.

13. The method of claim 11, in which R is a branch chain.

14. The method of claim 9, in which R-O- is where R2 and R3 are the same or dissimilar C5-C12 alkyl radicals, R4 is a C1-C3 alkyl radical, R5 is C2H4 or C3H6, each of w,m and n is zero to 1, subject to the proviso that, when w is zero, m is 1 or 2; and y is 1 to 6.