CA2116666A1 - Process to improve the color of sulf(on)ated surfactants without bleach - Google Patents

Abstract

A process for improving dark-colored sulf(on)ated surfactant compositions, and particularly alpha-sulfo fatty acid alkyl ester compositions, without the need for bleaching. The process comprises the steps of (1) forming a solution of a sulf(on)ated surfactant containing dark-colored impurities, in a suitable solvent and (2) separating the dark-colored impurities from the solution. Methyl ester sulfonates and methanol solvent are most preferred.
Treatment of the solution with an adsorbent, preferably activated carbon, enhances separation of the dark impurities. The surfactant is thereafter recovered from the solution by known processes, for example, precipitation of the surfactant and/or evaporation of the solvent. After processing in accordance with the invention, the sulf(on)ated surfactant has improved color, odor, and physical properties.

Description

2~1~6~
WO 93/0~013 P~/US9~/07332 PR~CESS TO IMPROVE THE COLOR ûF
SULF(~N)ATED SWRFAC~ANTS WITHOUT BLEACH ..
~

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Fiel~ of Invention . ~ -The invention is directed to improving the color of suifonated or :~
sulfated surfactant compositions'~ particularly alpha-sulfo f~atty acld alkyl ester compositions,: without the:~::need for bleachiny.

The ~ manufacture ~f alkali metal ~ salt;s ~f alpha:-sulfo fatty; acid al~kyl ~es~ers:: (hereinafter~ es~ter~sulfonates:"):by ne~utral~lIation~of f~atty acld ester~sul~onl~c~ aci~ds ~with~: aqueous caustic:~ lS
known.~ Such ~ester~:~:sulfonates;~ are~ predomln~an:~ly ~used ~ as :~
surfactants ln~washlng~and~c~leans~lng~agent~s~:and~products.

The ~known processes~far~ maklng;~these~ ester~sulfona:tes~ n~ good~
yiel~ds~suffer~:~from the~formatl:on ~of~dark-~colorad ~mRur~ltles.~ The:~
ester:sul~on~ acids, from which ~the~es:ter~sul:~onates:~:r~deriv~ed,:~
are~obtained:~by sul:fonation of :~fatty acid~ esters~ or, `les~s~
preferably, ~by~sul~fonati~on~and~e:s~erlflcat~lon:uf ~fatty~ac~ds.~ ln~
order~to~Qbtain~high~sulfonation~y:iel~ds,~ex~çess~sulfon~at;ing ::agent::~
~n~:combin~tion ~with~:greater proces~sing ~;:times and/o:r temperat`ures~
i~s~ requlred.~: These co~ndltions:~can~ result in~ unde~slrable s~ide`~
re;actlons includi~ng the formatlon of :~he~:dark-colored~imP~urlties.
Examples of; such sulfonation processPs ;are described in U.S.

. .

W ~ g3~05013 PCT/U~/0733~ :
2 11~66g;

3~485.856 and "The Journal of the American Oil Chemists Society"~
52 (1~75), pp. ~23-3~9.

For aesthetic and other reasvns, the dark-colored ester sulfonate - compositions are not suitable for use directly in washing br cleansing agents and products. Therefore, the dark ester sulfonate products have heretofore been bleached in order to lighten ~heir color. Typically the dark produc~s are treated with an aqueous bleaching agent, sueh as hydrogen peroxide or hypochlorite, before and/or after neutralization. Such bleaching processes are described in U.S. 3,159,657; 3,452~064; 4,547.318 and 4,617,900.

The art has recognized certain problems inherent to the bleaching process, particularly han~ling di~ficulties and hydrolysis of ~he ester group. ~eretofore these problems have been dealt with, inter alia~ by the optimizing bleaching process itself, or by modi~ying the ester sulfona~ion process itself to deliver an ester sulfonate with less color, thus allowing the use :of milder 2~ bleachlng conditions. Such processes are described in U.S.
3,997,57~; 4,080,372; 4,547,318; and 4,617,900. However; none of these references disclose a process for making ester sulfonate surfactant which is comple~ely satis~aetory. : ~

A method nf lmproving the color of dark-colored~ ester sulfonate compositions without the need for~:bleaehing has now been~
discovered.~ More speci~ically, ~ it has~been discovered that the darl(-colored impurities can be separa~ed by -known separation : methods from ~a solution comprising the ester sulfonate substantially dissolved in a suitable solvent. Separation o~ the : ! dark-col~red impurities from the solution can~be enhanced with an adsorbent:material, A~ter removal of the dark-colored 1mpurities, the ester sulfonate can be recovered from the: solvent: to yield :a product with: improved, i.e. lighter, color. The ~process :also 3; provides a particulate ester sulfon~te surfactant having improved physica7 properties; relative to that obtained by drying of the surfactant from a~ueous pastes and improved surfactant odor.
, 211~
WO 93/05013 Pcr/us92/o7332 The inventive process can also be applied to other sulf(on)ated surfactants whose preparation may result in the formation of dark-colored impurities during and/or after the sulfation or sulfonation reaction. Such surfactants include, but are not limited to, alkylbenzene sulfonates, linear alkane sulfQnates~
alpha-olefin sulfonates, fatty alcohol sulfates (i.e. alkyl sul fates ), and al kyl ether sul fates .

Summary of the Inv~ention The present invention involves a novel process for improving the color of a sulfonated or sulfated (hereinafter lS sulf(on3ated) surfactant composition, said surfactant composition comprising: `

(i3 a sulf~on)ated surfactant, preferably selected from the grollp consisting of: alkylberizene sulfonates, linear alkane sulfonates, alpha-olefin sulfonàtes, es~er sulfonates, fatty alcohol sulfates, alkyl ether sulfates and mixtures thereofi and ~.
(ii) dark-colored~lmpurlties ~ormed during the preparatlon Ot said sul~(on)ated sur~actant;
;: ~ ..
said process comprising the steps of ~
~ ; j : (1) ~formlng a solution~ cDmprlsing~

(a) said surfactant composition comprising said ~;
sulf(on)ate~ surfactant and said dark-colored `:
1mpuritles; and :
. . .
.
(b)~ a suitable solvent, ~preferably a Cl-C~
alcohol, in an amount sufficient to substantially ~ :
dissolve sa~d sulf(on)ated surfactant; ;.

,~
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W~ 93/05q)13 PC~/U~;92/0733, 2116~6 (2) separating said dark-colored impurities from said sol ut i on; fol 1 owed by (3) recovering said sulf~on)ated surfac~ant from said solution~ -wherein the amount of water present in said solution in step (1) is sufficiently low to avoid interference with effective separation of the dark-colored impurities from said solution. `-0 '~
The invention is particularly significant for Tmprovin~ the oolor of ester sulfon~te comp~sitions, since methods haYe been d i scovered for maki ng the other sul f ( on ) a~ed surf actant s wi th l ow levels of dark impuritles. The following disciosure is therefore directed to improving the color o~ es~er s~lfonate compositions.

..~

:
The ester sulfona~te compositlons which are imprvYed in ~color by the i nven~i on compri se an ester~ sul fonate havi ng the prsferred :
~ ~ general formul a ( l )~

R~ CH -- COOR~

SO3X :~
3 û
wherein Rl is~a:C4-C22 1lnear or branched chailn a~lkyl,~

R2 lS a~ Cl-Cg alkyl ,~ and : X lS~ a water-soluble sa~lt-forming catlon.
, . . .
:

~1 51~
Wo 93/05013 1~Cr/US9~07332 Particularly useful ester sulfonates are those wherein R2 is -CH3, ~:
i.e. methyl ester sulfona~es, and more particularly methyl ester sulfonates wherein Rl is C10-C16-The cation X is obtained from the agent used to neutralize the ester sulfonic acid to form the ester sulfonate. Suitable X ~-cations are monovalent ca~ions, includin9 alkali metals such as sodium, potassium, and 1 ithium; substituted or unsubstituted ammonium; and cations derived from lower alkanolamines, f~r :~
example monoe~hanolamine~ diethanolamine, and triethanolamine; and mixtures thereof. Par~icularly suitable cations are sodium, potassium, lithium, and those derived from lower alkanolamînes~
It is contemplated that ~he neutralization agent can also provide a cation ~laving a valence number grea~er than one, for example.
alkaline earth metals such as magnesium and calcium. In this `~
case, the general formula (I) would be modified to reflect the greater number of moles of es~er sulfonic acid associated with the cation in the salt (es~er sulfonate) form, said number being equal to the cation valenre number.

The ester sulfonic acids, ~rom which the ester ~sulfonates are~
prepared, can be obtained by s~ulfonating and then esteri~ylng natural or synthetic fatty acids~ or by sulfonating synthet~lc fatty acid esters.~For commercial reasons~the~ester sulfonic acids are prefe~rably~prepared by~sulfonatin~ ~atty ac~ld esters;.

;Examples~ of~sui~table~ fatty acld esters include,~ but are ~no~
~l;imi~ted to, methyl~ l~urate, ethyl ~aur~te~ propyl laur~ate, methyl~
palmi;tate, et~hyl~ palmitate~ me~thyl~ stearate, ~ethyl~;~`stearate,~
3~ ~ methyl hydrogenated tallo~ f~tty acid ester7~ethyl~hydrogenated tallow fatty ~acid~ ester, methyl~ hydrogen~ted coco fatty 'acld ester, ethyl hydrogenated ~ coco ~fatty acld ester~ methyl hydrogenated ; pal~m ~ ~atty; acid ester,~ and ~mixtur~s thereor.
Pref~rred are~ hydrogenated tallow ~fatty acid methyl ~esters.
hydrogenated~palm~ oil ~fatty acld~ me~thyl este~rs, hydrogenatea~
coconut oil~fat~ty~ aeid methyl esters, and mixtures thereof.

;~
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w o ~3/05013 PcT/uss2/07332 211~666 C
The fatty acid esters can be sulfonated to ~he sul~ofatty ac~d esters by known processes, for example, by thin layer or batch sulfonation. Suitable sulfonating agents include anhydrous S03, S03 dilùted with nitrogen or dry air, and the like. As an examp1e, linear esters of Cg-C20 carboxylic acids can be sulfonated with gaseous S03 according to "The Journal of the American Oil Chemists Society", 52 (1975), pp. 323-329.
~ ':
The sulfonation of the fatty acids or fatty acid esters can result in the formation of dark-colored impuri~ies in the ester sulfonic acid product. Neutralization of the ester sulfonic acid with an agent providing thc water-soluble ca~ion X re~ults in ester sulfonate comprising dark-colored impurities. In accordance with the present invention, these dar~-colored impurities can be separated from the ester sulfona~e t~ provide a product having significantly lighter color.

The process comprises the step of forming a solution of the dark ester sul~onate product in a suitable solvent. Suitable s:olvents :
inelude any which are capable o~ substantially di:ssolving the ester sul~onate under appropriate temperatures and pressures.
Mixtures of solvents~can be used provided that the mixture is capable of substantlally dissolving the ester sul~onate under appropria~e proc~ss condition:s. Particularly~suitable solvenls for processing ~ster sulfonates are C1-Cg alcohols and:lower : : esters thereof.:: Preferably:C1-Cg ~alcohols: are used;~:there~ore~
the process is further :described in ~erm~ ~of: lower alcohol: ~ :
solvents. However, it is contem~lated thàt any solvent as broad~ly :~def:ined:above is usable in the pr~cess. More pre~erably~metha~nol,~
ethanol and mixtures thereof are used, an~ most preferably methanol is used~

Sufficient lower alcnhol, in an amount relative to the~ester sutfonate7 must be present to solubilize the ~ester sulfonate at practical processing: temperatures and p~essures.~ For best results, concentrations and~process condition~s are selected to substantially dissolve, and most preferably to wholly dissolve.
:

~.

W ~(~3/~5~3 ~ 1 1 6 ~ ~ ~ PCT~US9ZtO7332 the ester sulfonate prior tO separation of the dark-colorea impurities. The selection of suitable solubilization conditions is considered to be within the ability of one of ordinary skill in the art, However, the weight ratio of lower alcohol tO ester sulfonate will yenerally be from 10:1 to 0.75:1 a~ temperatures of between about 10C to about 110~C, more preferably from 5:1 to 0.75:1, even more preferably from 3:1 to 0.75:1" and most preferably from 2:1 to 1:1. Higher ratiss of lower alcohol to ester sul fonate (greater than 10:1 ) can be used, but are probably not any more effective. The amount of lower akohSol required to solubilize the ester sulfonate can be added at any or all of the points beForet during and after neu~ralization of ~he ester sulfonic acid to form the ester sulfonate, further discussed herein. Advantageously some or all of the lower alcohol is added during neu~ralization. Preferably substantially all of the lower alcohol is added during the neutralization step.

The amount of water in the solution must be sufficiently low to avoid interference with e~fective separation o~ the dark-c~lored 2~ impurities from the solution. Without intending to limit the invention, it is theori2ed~that too much water, in relation to the amount of lower alcohol and ester sulfonate present, can result in the ~ormation o~a~separate es~er sulfonate/water p~ase which can make it difficult to separate the dark-colored impurities from the lower alcohol solvent-containing phase.~ It is further theorized that in the presen~e of sufficient water, the ester sulfonate can act as a surfactant to effectively solub~lize at least a portion of the dark-col;ored impurities.

It is also theorized that some portion o~ the d~rk-colored~
impuri,ties are soluble or suspendable in ~he l:ower alcDhol~;an'd/or the solution. It is believed~ that such soluble o~ suspendable : impurities can be sep~rated;by adsorbents, such~ as actlvated carb~n. The other portion of the~dark lmpuritles, which are not soluble or suspendable in the lower alcohol and/~r solution, can be separated from ~the solution by other se~aration methods as described herein.
~:: ` ' ~: :' W(~ ~/()5~ CI /US92/0733~
2116~;66 The selection of suitable ratios of lower alcohol to water relative to a given amount of ester sulfonate is considered to be within the experimental a~ility of one havlng ordinary skill ln the art. Preferably the weight ratio of alcohol to water is at ; least 3:1, more preferably 10:1, and even more prefera~ly ~0:1.
Most preferably the solution is essentially free of water in order to achieve more effective separation of th~ dark-colored impuirities.

It is highly pre~erred thak the neutralization process used to pr~pare the ester sulfonate minimize the amouint of water in the ester sulfonate product. In this way, the alcohol: water ratios required for effective separation o~ the dark-colored impurities can be obtained without the nee~ ~or exc~ssiively large amounts of alcohol or the need for a separate dehydration step for the ester sulfonate, prior to dissolving with lower alcohol. Accor~ing to a preferred embodiment, neutrali~ation is performed with substantially anhydrous solutions of the neutralization agent in a lower alcohol solvent. The selection of the particular alcoho?
solvent depends upon the deslred ester, since transes~erl~ication may oocur during neutralization.~ For example, where methyl ester sul~onates are desired, methanol is the~preferred alcohol solvent.
~, According to a particularly pre~erred embodiment, neutrali;zation is performed~by~addition of the ester sul~onic ~acid to a soluti~on of alkoxide in alcohol,~ said alkoxi~e having the~formula R30X, wher~in R3 is Cl-Cg~alkyl and X is~a water-saluble~salt-forming~
cation as here~nbefore~de~ined. (See~Japanese~Laid-Op~n Patent Publieation No. 29084;2/1~gO~ Alterna~ively~ the alkoxide i~
alcohol solution can~be added~to the estér sulfonic acid, or the ;~
`two solutions~ can be mixed together simultaneously, as ~which~
occurs in an in-live mixer~. The ~ilkoxide~solution can be pri~pared by known methods, for example, by ~di~ssol~vlng an~ alkàll- or alkaline earth- metal C1-Cg alkoxide~ln t~he respeotive alcohal ~o }
directly provide ~an ~essentially ~anhydrous neutralizat~ion ~system.
The alkuxide solu~îon can also be ~ormed by dissolving a solid alkal~- `or alkaline earth- metal hydroxide in the alcohol, ~

,, ' .;

W O ~3/U~01~ 2 1 1 ~ ~ 6 ~ PCT/U59~/07332 a~though this method of forming the alkoxide solution is less preferred since one mole of water is forme~ for each mole of alkoxide generated. If this latter method is used, the water from alkoxide generation can optionally be removed by known methods to provide an essentially anhydrous neutralization system.

An amount o~ lower alcohol sufficient to dissolve the resultant neutralized es~er sulfona~e can be used in the preferred substantially anhydrous neutralization. Additional solYent can ~e added after neutralization as required to dissolve the ester sulfonate prior to separating the dark-colored impurities. Such additional solvent can be any as defined above in ~orminy the solution comprising the ester sulfona~e surfactant and the lower alcohol solvent.

Of course, the ester sulfonate can also be prepared by neutralizing the es~er sulfonic acid by well-known processes.
including conventional neutralization processes involving aqueous 5-50% oaustic solutions. Any residual wa~er in the ester sulfonate product can then be removed ~s necessary by known methods, such as drying~ b~fore proceeding ~o separate the dark-colored impurities.

Where water is present during neutralization, preferably at least a portion of the alcohol required to substantially diss~lve the ester sul~onate is mixed with the ester sulfonic acid prior to neutralization. By~ premixing the ester sulfonic acîd with alcohol, it :has been shown in the art ~See7 for example, ~.5.

4,404,143, Sekiguchi et al, September 13, 1983~ incor~orated herein by reference) that reduced levels of fatty acid disalts are formed during neutrali2ation, relatlve to ~systems where no premixing with alcohol is per~ormed. Additionally, premixing suppresses the formati~n of an ester sulfonate/wa~er phase:.
thereby providing better mixing and^lmproved neutralization.

The prQcess of the presen~ invention further comprises the step of separating dark-colored impurities from the solution of the ester WO 93/0~;0~3 PCI~/US92/07332 æ~ iO , .~
sulfonate product in alcohol. Separation can be achieved by conventional methods such as settlin9/clarification~
centrifu~ation, filtr~tion, adsorption. or a combination thereof.
The particular separation method or methods employe~ will depend upon a number of factors, such as the amount and proportion of dark-colored impurities which are insoluble in the solventl versus~;
those that are sol uble or suspendable in the solvent. and the amount and proportion of water relative to the amount of solvent and ester sulfonate surfactant. . ;~:~
'~"'' Clarification can be accom~lished by simple gravitation; on an industrial sc~le the use of conventional equipment. such as ~-revolving plows or rakes, can be used~ to aid separation.
Centrifugation can be by ~i~her a batch method or a continuous method, involving decantation of the supernat2nt from the sedimented dark-colored impurities.
. .
Filtration can be performed thr~ough conventi~onal filters. For ~i~example, on a laboratory scale,~ filtration~ through pap~er, `~
diatomaceous earth, or adsorbent are suitable. ~On an lndustrial ~-scale9 suitable filtration equipment includes pressure filters of the plate-~nd-frame or shell~and-lea~ cons:truction, or: of~ the rctating drum~or:disk~type; vacuum :or suctlon~ filters of the rotating drum or dlsk :type; edge~ filters; clarif1c:atlon~;~fllters~

;n a preferred mbodimen. tbe ~solu~ion ~s treated~ wlth a adsorbent materl~al~ such:~as act~lv~ated;~carbon~ ;activated:~alumlna~
: : or silica~ gel.~ Such: adsorbent: mat:erial is~believéd : to be;~
particularly ~ective:~ at separati~g~ that:~ portion ~of ~:the :I dark-c:olored impurlties whlch are theorized to be~ soluble or ~ ~ ~
suspendable in ~the a~1cohol:~and/or solution,: as ~:discus~s~ed~ herei~n:~ n : ~ above. P~referably ac~tlvated~carbon;is~used as the~adsorben~t.

: ~5 Wher~ an adsorbent filter is used fo~r separat~ion, ad~sorbent : treatment occurs: during :filtration. Adsorbent treatment can alternatively oc~ur elther before or, preferably, after~separation WO 93/0501~ 2 1 1 S 6 6 ~ P~r/uss2/o7332 of dark impurities by a non-adsorDent method. For example. the solution can be mixed with a suitable amount of adsorbent particulate? such that aark-colore~ impurities adsorb onto the particulate, followed by separating the adsorbent partioulate by, for example, cen~rifugation and/or non-adsorbent filtration.
Treatment can also, and most preferably, occur by passing the li~uor ob~ained after an initial separation of dark-colored impurities by, for example, centrifugation and/or non-adsorbent filtration, through an adsorbent bed. Alternatively, the liquor can be mixed with fresh adsorbent particulate s~ch that dark impurities adsorb onto the particulate, followed by separating the spent or used adsorbent particulate by any suitable method, such as those previously described.

Preferably, the temperature required to solubilize the ester sulfonate (in the step of formin~ the solvent sol:ution of the ester sulfonate eomposition) is maintained throughout the separation and through to the ~ final product recovery step.
Additional lower alcohol can be added as needed to solubilize any ester sulfonate which may precipitate during the~separation.
~..;.
In commercial applications, the ester: sulfonate dissolving and impurity separation ste~s would pr~ferably :be conducted in suitable pressurized, enclosed equipment and equlpment systems to avoid evaporating the solvent at the ;s~lected solvent temperature.
: Such evaporation can resu7t in undesirable:evaporation cooling, and loss of solvent vapors to the environment.

After separation of the dark-colored impurities;from the solution, the ester sulfonate product having improved color c~an be recove,red from the solvent solution by known methods~ Such recovery ~ethods include, for example, precipitation of the ester sulfonate from the solution, evaporation of the lower alcohol solvent from the solution or a combination thereof. Preeipitation of the ester sul~onate can be achieved by :reducing the temperature of the solution, and thereby the solubility of the ester sulfonate in the lower a7cohol. The precipitated ester sulfonate can then. be :;

''`,;

W ~ 93/05013 P ~ /US~/07332 211666b 12 -- ~
recovered by known metho~s, tor ~xample. ~iltration followed by evaporation of essentially all of any residual solvent.
Evaporation may occur under normal or reduced pressure and with or without heating to yield a solid or ~olten ester sulfonat2 that can be processed by known methods to any desired form, such as powder, flake, chunk or granulate.
'~.' On an industrial scale, the lower alcohol, and any water which may be present, can be removed by he~ting the solution and flashing or evapora~ing the alcohol (and water, if present). This can b~ done by any suitable metho~, including conven~ional processe~, such as spray drying, atmospheric fl~sh drying, vacuum flash drying,~ drum drying, wiped film evaporation~ or a combination thereof. Spray drying can be used to directly yield an ester sul~onate p~roduct in powdered or granular form. The~ other methods yield ester sulfonate products in a chunk, noodle~ or large particulate form.
which can b~ further processed b~ known methods to any desired form, for example, milli ng to a granular form, or flaking and then chopping or milling to a :granul~ar ~orm. The ~alcohoi ~which tS
: ~ 20 removQd to reciDver the es~er sulfonate is advan~ageously condensed, r~covered and recycled for re-us~e in any o~ the alcohol :addition steps des:cribed herein. Where the ester sulfonate is , ~
recove~ed by fil:tration :o~ precipitated ~:re-crystall:ized):~ ester : .-.
~ sulf~nate,~ the ~resultant ~liquor :o~tain~ed:from~:filtratl~on, ~whlch~
:~ 25 ~ contains lower~alcohol : and : some:~amount:~ o~ dissolYed~:ester ; sul~onate, cao ~be recycied to~any~precedl~ng step ln~the~ process,~
~pre~erably back to :the step where fresh, dark-colored~:ester~
: ~sul~fonate is d:issolved~ n lower al:~ohol to ~orm a~solution.~

~ As a result~of this process,:ester~ sul~fon~ates o~f~ lmproved, i.~e.:
hter, color are ob~ained. Where the process has ~also involved effective adsorbent~ tr~atment ~of the sol:uti;o~, the: resultant : :product i:s~ ne~:r-whi~te in coior and can:~ be used directly in~
~ ~leansing and~washing:ag~nts and: pr~ducts. The::resul~ant:~product :~
: 3~ ~may also ~be~ converted lnto a light-colored~paste~by add~ltion~of ~ ~ :
wat~r: afte;r ~sèparati~on o~ ~the d~rk impur1ti~es. ~ffective : ~ ~
adsorbent treatment further results in improved:surfac~ant odor. ~i : :~

W O ~3/050l3 2 ~ ~ S fi G ~ r/us92/~7332 -- 13 -- l Improved particle physical properties are also achieved by the present process, relative to those obtained by drying of a conventional aqueous system. The amount of water rel ative to alcohol in the separated solution is belieYed to have an important effect on the physical properties of the resultant light-colored ester sulfonate product. As the ratio of water: alcohol increases, it ~ecomes increasingly difficult to remove the solvent comprising alcohol an~ water. Therefore, where water is present in the solution, removal of the solvent with heating is preferred for improYed physical properties.

The process further al l ows for greater fl exi bi l i ty i n the raw materials and process conditions of sulf~nation. For example, starting materials having a greater degree of irnpurities 1~ themselves whîch can result in the formation of the dark-co10red impurities, or processing conditions for obtaining grea~er rates of conversion to the ester sulfonate, may be used without the concerns heretofore associated with the need for bleaching.
Impurities which can result in the fcrmatiQn of dar~k-colored impurities are known in the art, and tnclude glycerl~e, glyeeride (mono-. di- or tri:-) and unsaturated fatty aeid ester. By avoiding the need for bleaching, the proce s may also avoid the formation of sensiti:zers, such as those described in D. Oonnor et al.; Identifica~isn of Certa~n_Sultones as the~Sen~sitizers in an /11~ Y~2 1~L~,~ "Fette Seifen Ans:trichmittel" 77, 25-2 : The ester sulfsnates obtained by the method :sf the present : invention are useful as an active ingredlent: for cl@anslng an~
washing agents and pr~ducts, and which ~an be employed either independently or in admixture with other surfactants. For example, in: detergent c~mpositions~ sultable~;co-surfactants in~lude anionic surfactants, nonionio ::sur.fact:ants, catisnic surfactants, zwitterionic surfactan~s or amphoteric surfacta~ts Othér ingredients conventionally used in de~ergent fsrmulations ~may als~ be used. Such lngredients include those generally used as builders, enzymes, bleaching agents and activators, soil ,.,:'.
.~

WO 9~/ûS013 PCr/USg2/0733~
211~6f~ 14--release agents, chelatin~ agents, soil-remova1 ina anti-redeposition agents, dispersing agen~s, brighteners, suds suppressors, etc.
~.~
The invention is illustrated by the following non-limiting examples. All par~s and percentages herein are by weight unless otherwise stated, All color measurements were carried out using a ~`
Hunter Colorimeter providing L~ a, b readings.

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21~i6S

wo ~/n5(~ - 15 - - PCT/U892/07332 ,.'~

EXAMPLES ~

x~m~ .
:.
.,,~.
Ester sulfonic acid was produced by conventional sulfonation of p~lm stearin ~atty acid methyl ester. The acid component of the `~`
methyl ester consisted essentially of saturated fatty acids wi~h an Iodine Value of 0.28 and the following chainlength distribution (by weight percent):
~ ,.. .
C12 - 0.~3 :
~14 - 1.5~ i , C15 - 0.08 i C16 - 66.;rj ~ `
C17 - 0. 15 :`
2~ ~ Cl~ - 31 . 28 ::: c20 - ~o.ig , The;sulfonatlon reaction;was ~carried out at 80 C to 95DC ~ln an annular fatling~fi~lm re~ac;tor;using a:: mlxture of~ su~lfu:r trloxlde 25 : and~: air (503 cantent:::3-4% :by ~volume;~ S03 exces:s~ 5-30 mole :perc~ent~ he~;s:u;l~onat~ed:~me~hyl::ester~acid mlx~:was:~then~digested~
; in~ 2~ closed~:vess:e~l ~for~:35~:to~40: ~mi nutes~at:;a t:empera:~ure~of~ 80~C~
o~95:-t. The degree of sul:fDnat~or~a~ter~dlge~sb on was 95Y..~

~ ~A::portion of the sul~onat:ed methyl~:~este~ acid mix~wa:s~cool:ed ~o ~ about ~20 C and~:ground lnto a powder.: This powder gave~ a:~cblor A ~ ~ r~adiflg of L=14.9, a-0, b~0.8.~ Percent~Yolatiles:~o~: the~ sample~
was~-3%~ (by ~Cenco drylng; consisting essentially~ of~ ncidental~
m~is~ur~

: : ::Undér ~high~shear~mixing,~500 9 of:~:the ~aeid mlx was mlxed with ~ :methanol (lOOg):at:45C to 55~C. and neutr li~ed by adding 25%~w/w:

:: : ~ : : : ; ~
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WO ~3/0~013 P~/US92/07332 211~ i 5 , ~
solution of CH30Na in methanol. (More pre~erably, the acid mix can be added into the 25% w/w solution of CH30Na in methanol.)The volatiles content of the neutralized product was determined (by Cenco drying an al iquat) to be 32%, consisting of methanol and incidental moisture. A portion of the neutralized product was air dried to a 7% volatiles content (Cenco) and ground to a powder.
The colur of this dried sample was L=28.8. a=2.5, b=7.1. A second portion of the neutralized produet (73.59; Cenco volatiles 32%3 was dissolved into 176.59 o~ methanol . 29 of a~tivated carbon ~decolori~ing activated carbon, Aldrich Chemical Co., catalog ~16,155-1) was added to the solution, which was then stirred for 6V minutes at a tempera~ure of 40~C ~o 509C. :Thls solution was vacuum filtered through 15cm-diameter Whatman #41 paper on~o which was added an additional ~g activated carbon. The filtered~ liquor was passed a second time ~hrough the same filtration assembly.
The liqu~r was then air dried to a 10.4% volatiles content ~Cenco) and ground to a powder. The color of this powder was L-81.S, a--0 . 7, b=13.6 .

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W O 93/050~3 P~T/US92/07332 ExamDl e 2 ( comDarat i ve L

Sulfonated methyl ester acid mix was prepared from the same palm stearin fatty acid rnethyl ester stock used in Example 1, using ~;
substantially the same sulfonation conditions. The color of a ~-ground, powdered sample of the sulfonated methyl ester acid was L
= 19.8, a = 0.7, and b = 1.4.
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Fo110wing digestion of the acid mix, 20% (~/w sulfonated ester acid~ methanol and 8% (wtw sul~onated ester acid) hydrogen peroxide solution (S0% ~22 in water) were added ~o and mixed with the acid mix. This mix~ure was then further digested with ~
n~gligible additional mix~ng or back mixing for about 5Q minutes ~-at 70'C. The bleached aci~ mix was then neutralize~ with 12.5% --NaOH ~aq.) so~ution at 63-C to an aqueous (5~-;57% moisture) pas~e.
Water was eYaporated from the paste (plate ~and frame heat -~
exchanger, exit paste temperature 295-305DF, fl:ash to a~mosphere~
followed by chilling to yield bleached, ester ~ul~onate flakes having 3-5% moist~re (Cenco an~lysis). The flakes were ground into a powder having a color of L = 90.7, a - -3.1, and b - 10.8.

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Claims (32)

-- 18 --

1. A process for improving the color of a sulf(on)ated surfactant composition, said surfactant composition comprising:
(i) a sulf(on)ated surfactant, and (ii) dark-colored impurities formed during the preparation of said surfactant;
said process comprising the steps of:
(1) forming a solution comprising:
(a) said surfactant composition comprising said sulf(on)ated surfactant and said dark-colored impurities; and (b) a solvent in an amount sufficient to substantially dissolve said sulf(on)ated surfactant;
(2) separating said dark-colored impurities from said solution; followed by (3) recovering said sulf(on)ated surfactant from said solution, wherein an amount of water is present in said solution formed in step (1) which is sufficiently low to avoid interference with effective separation of the dark-colored impurities in step (2).

2. A process according to Claim 1 wherein said sulf(on)ated surfactant is selected from the group consisting of ester sulfonate, alkylbenzene sulfonate, linear alkane sulfonate, alpha-olefin sulfonate, fatty alcohol sulfate, alkyl ether -sulfate and mixtures thereof.

3. A process according to Claim 1 wherein said solvent in step (1) is a C1-C8 alcohol.

4. A process according to Claim 3 wherein the surfactant is an ester sulfonate having the general formula (I) (I) wherein R1 is a C4-C22 linear or branched chain alkyl, R2 is a C1-C8 alkyl, and X is a water-soluble salt-forming cation.

5. A process according to Claim 4 wherein R2 is -CH3.

6. A process according to Claim 4 wherein a weight ratio of C1-C8 alcohol to water in said solution in step (1) is at least 3:1.

7. A process according to Claim 6 wherein said weight ratio of C1-C8 alcohol to water in said solution in step (1) is at least 10:1.

8. A process according to Claim 7 wherein said weight ratio of C1-C8 alcohol to water in said solution in step (1) is at least 30:1.

9. A process according to Claim 8 wherein said solution in step (1) is essentially water-free.

10. A process according to Claim 6, 7, 8 or 9 wherein the weight ratio of C1-C8 alcohol to surfactant in said solution in step (1) is from 10:1 to 0.75:1.

11. A process according to Claim 10 wherein the weight ratio of C1-C8 alcohol to surfactant is from 3:1 to 0.75:1.

12. A process according to Claim 10 wherein the weight ratio of C1-C8 alcohol to surfactant is from 2:1 to 1:1.

13. A process according to Claim 4 wherein step (2) comprises centrifuging said solution.

14. A process according to Claim 4 wherein step (2) comprises filtering said solution.

15. A process according to Claim 4 wherein step (2) comprises mixing adsorbent particulate with said solution, such that said dark-colored impurities adsorb onto said adsorbent particulate, followed by separating said adsorbent particulate from said solution.

16. A process according to Claim 15 wherein separation of said adsorbent particulate comprises centrifuging said solution.

17. A process according to Claim 15 or 16 wherein separation of said adsorbent particulate comprises filtering said solution.

18. A process according to Claim 13 or 14 wherein Step (2) further comprises passing said solution through an adsorbent bed.

19. A process according to Claim 18 wherein said adsorbent bed is an activated carbon bed.

20. A process according to Claim 4 wherein in step (2), said dark-colored impurities are separated by passing said solution through an adsorbent bed.

21. A process according to Claim 15 or 20 wherein said adsorbent is activated carbon.

22. A process according to Claim 4 wherein step (3) comprises evaporating said C1-C8 alcohol from said solution.

23. A process according to Claim 4 wherein step (3) comprises precipitating said ester sulfonate from said solution.

24. A process according to Claim 4 wherein said ester sulfonate is obtained by neutralizing an ester sulfonic acid with an agent supplying said cation X in a substantially anhydrous medium of a C1-C8 alcohol.

25. A process according to Claim 24 wherein said agent is an alkoxide of the formula R3OX, wherein R3 is C1-C8 alkyl.

26. A process for improving the color of a methyl ester sulfonate composition, said composition comprising:

(i) a methyl ester sulfonate of the general formula (II) (I) wherein R1 is a C4-C22 linear or branched chain alkyl, R2 is a C1-C8 alkyl, and X is a water-soluble salt-forming cation, and (ii) dark-colored impurities formed during the preparation of said methyl ester sulfonate;
said process comprising the steps of:
(1) forming a solution comprising:
(a) said methyl ester sulfonate composition comprising said methyl ester sulfonate and said dark-colored impurities, and (b) a lower, alcohol solvent selected from methanol, ethanol, and mixtures thereof, wherein a weight ratio of said lower alcohol solvent to said methyl ester sulfonate is at least 1:1, and wherein a weight ratio of said lower alcohol solvent to said water in step (1) is at least 3:1, and (2) separating said dark-colored impurities from said solution by a step comprising centrifuging said solution, filtering said solution, treatment of said solution with activated carbon, filtering said solution through activated carbon, and combinations thereof;
followed by (3) recovering said methyl ester sulfonate from said solution.

27. A process according to Claim 26 wherein said lower alcohol solvent is methanol, and said weight ratio of methanol to methyl ester sulfonate is from 3:1 to 0.75:1.

28. A process according to Claim 27 wherein said weight ratio of methanol to water is at least 10:1.

29. A process according to Claim 28 wherein step 2 comprises filtering said solution, followed by filtering said solution through activated carbon.

30. A process according to Claim 29 wherein step 3 comprises reducing the temperature of said solution in order to precipitate said methyl ester sulfonate, followed by filtration of said precipitated methyl ester sulfonated from said solution.

31. A process according to Claim 28, 29 or 30 wherein step 3 further comprising a step of evaporating said methanol solvent from said solution to recover said methyl ester sulfonate.

32. A process according to Claim 30 wherein step 3 further comprising a step of evaporating essentially all of an amount of residual methanol solvent from said filtered, precipitated methyl ester sulfonate.