CA2000278A1 - Process for the production of light-colored -sulfofatty acid alkyl ester salts - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Light-colored .alpha.-sulfofatty acid alkyl ester salts are produced by sulfonation of fatty acid alkyl esters with gaseous sulfur trioxide in the fatty acid alkyl esters are sulfonated in the presence of 0.25 to 1.5 mol-%, based on fatty acid alkyl ester, of at least one fatty acid amide corresponding to formula I

(I)

Description

ZOO~Z78 PATENT
Docket D 8405 CA

A PROCESS FOR THE PRODUCTION OF LIGHT-COLORED
a-SULFOFATTY ACID AL~YL ESTER SALTS

BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to a process for the production of light-colored ~-sulfofatty acid alkyl ester salts by sulfonation of fatty acid alkyl esters with sulfur trioxide and subsequent working up.

2. Description of the Related Art The sulfonation of fatty acid alkyl esters for the ~-production of ~-sulfofatty acid alkyl ester salts (herein-after referred to as "ester sulfonates") has long been known. On an industrial scale, the starting materials used are fats and/or oils of vegetable or animal origin from which the fatty acid alkyl esters are obtained either by hydrolysis and subsequent esterification with lower alkan-ols, particularly methanol, or by transesterification of the natural triglycerides with lower alkanols. Depending on the origin of the natural starting material, the fatty acid ester mixtures obtained contain esters of fatty acids i~
covering a comparatively broad chain length range of normally from 6 to 22 carbon atoms. In known processes, these fatty acid ester mixtures are preferably sulfonated with gaseous sulfur trioxide. This leads to more or less heavily discolored, acidic crude sulfonates which are ; bleached and converted into ester sulfonate pastes by neutralization to a pH in the range from about 6 to 7. In -~
this form, they are of considerable importance as surfac~
tants for washing and cleaning purposes. ~-~
Despite optimal industrial sulfonation conditions, batches which can only be blleached with difficulty, if at ---~
, -,: , Z()O()Z78 ~:~.3., .~r~ lc~ M~:~ t~ For~l r~p ~ d il~fJ~ tr~ u~s ~e t`~ eni: t y o~.~t:.2i ~ 1 in the ~r~s~ t loJt of ~sto~ at~ .
qh~ arl~ t lon 01~ d~k c~olo~d pxc)~ ts is larg~y ~:t.cl~t~tl t.o oxl~J~:.Lorl ~ruduc:t~ th~.t l~A~:~.y ~c:!d ~ter u~d ~),yf~raxyt ~i~.y~iroxy, c.)~ 4~ ) whlr,h, or~ o on~s ~rtfl, ~r~A.lt ~ tlv~ r~CI~ J ~' tha i~Atty ~lCS kl ~ p~ ur~.ng pro~auctLon ~nd ~t:or~g~ o~ ~hc ~f~ flr~ur ll~g p~ U~ e Alkyl ~4rf~ arid whi~h, C3n th~! C~ hP~nd, n~4 or~l~sd clurlny ~UL~Or~t~On af ~h~ al~y~. efi~t;*r~ .h g2~eou~ ~ulfur tr~ 1d~ by ~he etrong i t~t~ s~h~ a~ tr~.ox~
l'he f~ rm~n ~ OXC3 ~ecorld~ry ~:odu~ .UriJn~ working ~Ip Q~ tri~.~.y~3rld~.s tD th~ ~y/irf~J~n~ttQd ~ y a~1cl h~. .ti.s i by tec33n s~:1 m~.7l~3 by pun~ ul~--~icrl in th~ ~b~S~ f ~.~ r or t,y l~i~ti~ ,On Vid bo3~1C
we.,~ t~ ni~ r*~ h~ ,r~ littl~
f ~c~ h~ s~ ~t~)s~at~ th~ lky~ t~r~ ~. h;rJow l~lr~ U~ e}~ O,~r l(~l~sing e~Cfre~.t Or tl~ f3ul~ur t~;.L;~xi~e c~n c~ y 1~ c~uc~~d ~y ~n~rl3u~:eo.n~L~ pl~3~.~n~J n~ ~h~
2C1~lul fi3r ~r~.ox:Ld~ hc,we~r~r, un~l~r~ut.:~n~lon l~d8 ~.o r~ y~ or~pl~x~ Ag~n~ wh~c~h h~v~ ?~ p~po~ed U/,t;~! t Por f~x~mE~ , d 1~x~n~ ( M . 6ut~ar ~ ~ ~, J ~ At~ .
~:nR~n. sc~ ~ Q ~ B), 53~3 540,, 3.1.kyl pho~ph~t~ ~A.~.
T~r~k ~ ~, 0, Inàl. ~ng. Ch~m. Protl. R~ V~relop. 2 2~ 317 ~t~ t~yl ~ .tt~ S. ~ ya~
~hem. ~ , Jap~n D~7 ~lg74], ~47~-~?4751. ~o~r~v~r, the pr~ m~n~ n~ ar~ nd~d ~-~r th~ dL~2,dtt2~ t~a~, or~ t;h~3 ~n~ h~nd, they lead t~ .~.ndu~r~lly ln~dequate c4~l~fre~ t~ r~d/s~r ~n t~ h~r l~ar~ ~r~ t~nd~
3Q ~onsider~ble ~r~p~rAt~ve ~ lcul~:iea, ~o th~ hey are url~uit~le rvr indu~tr~Al ~pplicat~on.
~rh~. pro~len~ addr~oR;~ ~y the pr~h~ ~nv~n~lorl Wfllj~, on the ~)ne h~d, tc) pro~ride ~ mprov~d pro~e~ ~or t~e produ~ioP~ of ll.qht-colored a~ lfo~tty acid al}~l R~tsr ~alt~ by ~ullf~r~at~on og ~atty as~id ~lkyl e~st~r~ s~lth ~
~uli~os~ti~cJ ag~!r!~ ~nd 9Ub~3~3qlJ21~t Wosklr~ p. PIOYO par-t~ y~ ~ha p~ol~len~ add~ ed by the is~n~ W~B t~

~;, , , ~;'"'1'~ ' ~ .
~'`' ' ~ ,, ' ~ ' , 2(~0Q278 reduce the oxidizing effect of sulfur trioxide where it is used as the sulfonating agent without the conversion levels of the sulfonation reaction being reduced and without other preparative difficulties arising.
S DES~RIPTION OF ~HE INVEN~IQ~
It has now been found that the addition of small quantities of certain fatty acid amldes to the fatty acid alkyl esters has a positive effect on their oxidation stability, so that only small quantities of color-active oxo compounds are formed and ester sulfonates of uniformly high color quality are obtained in the sulfonation with sulfur trioxide.
The present invention relates to a an improvement in a process for the production of light-colored ~-sulfofatty acid alkyl ester salts wherein a fatty acid alkyl ester is sulfonated with gaseous sulfur trioxide to produce a sulfonated reaction product and wherein the sulfonated reaction product is subsequently aged, bleached, and neutralized to form an ~-sulfofatty acid alkyl ester salt, wherein the improvement comprises sulfonating said fatty acid alkyl ester in the presence of from 0.25 to 1.5 mol-%, based on fatty acid alkyl ester, of at least one fatty acid amide corresponding to the following formula ~ . . . . .
.,:.-.:
-, ...

,, - ,~, ,, " ;- .,: . . . :, :

200~278 R1 _ 1l - N / (I) R~
in which R1 is a linear C521 alkyl radical, R2 and R3 independently of one another represent a hydrogen atom, a linear or branched C1h alkyl radical or R2 and R3 together form a tetra- or pentamethylene chain of a heterocyclic ring system, in which a methylene group may optionally be replaced by an oxygen atom, a sulfur atom or an NH group.
In one preferred embodiment of the invention, the fatty acid alkyl esters are sulfonated in the presence of 0.75 to 1.0 mol-% fatty acid amide.
The fatty acid amides corresponding to formula I are known substances which may be prepared by standard methods of organic synthesis. Examples of suitable compounds are caproic acid N,N-dimethylamide, caprylic acid n-butylamide, capric acid N,N-diethylamide, lauric acid N,N-dimethyl-amide, lauric acid morpholide, myristic acid i-propylamide, myristic acid N,N--dimethylamide, myristic acid pyrrolidide, palmitic acid amide, palmitic acid i-butylamide, palmitic acid N,N-dimethylamide, stearic acid amide, stearic acid methylamide, stearic acid N,N-dimethylamide, stearic acid n-propylamide, stearic acid N,N-di-n-propylamide, stearic acid i-propylamide, stearic acid n-butylamide, stearic acid N,N-di-n-butylamide, stearic acid n-pentylamide, stearic acid N,N-di-n-hexylamide, stearic acid i-butylamide, stearic acid N,N-di-i-butylamide, stearic acid pyrrolidide, stearic acid piperidide, stearic acid morpholide, behenic acid amide and behenic acid N,N-dimethylamide.
The fatty acid amides corresponding to formula I may be used individually or in the form of mixtures of several individual compounds. In one preferred embodiment of the invention, the fatty acid amides of formula I added to the fatty acid alkyl esters are those in which the substituents R1 contain 15 to 17 carbon atoms, the substituents R2 and R3 of these fatty acid amides again preferably cons~sting of linear alkyl radicals.
Sulfonation by the process accordinq to the invention may be applied to esters of saturated fatty acidsi with lower aliphat~c alcohols, particularly Cl~ alkyl esters of saturated fatty acids containing rrom 6 to 22 and prefsr-ably from 8 to 18 carbon atoms. The fatty acid residues of these esters emanate from natural fats and oils and are therefore exclusively or at least predominantly linear.
The alkyl radicals of the fatty acid esters emanate from linear or branched, aliphatic Cl~ alcohols. Methyl esters are preferably used as starting material for the sulfona-tion reaction.
The fatty acid alkyl esters are obtained in known manner from fats and oils of natural origin either by hydrolysis and subsequent esterification of the free fatty acids with lower alkanols or by transesterification of the natural triglyceride mixtures with lower alkanols. Apart from the methylene group in the ~-position, they should contain no other sulfonatable or sulfatable groups and, in particular, no double bonds or alcoholic hydroxyl groups.
For this reason, the starting materials - either the fats and oils or the alkyl esters obtained therefrom -are hydrogenated before sulfonation to iodine values below 1 and preferably below 0.5 under known conditions for the hydrogenation of fats. According to the invention, it is possible in principle to use individual fatty acid alkyl esters, for example methyl stearate, as the starting material for the -sulfonation with sulfur trioxide. On an industrial scale, however, alkyl esters of fatty acid mixtures are generally used.
The sulfonation reaction is carried out under the same conditions as the relevant known processes for the ~
sulfonation of fatty acid derivatives as described, for example, in DE-A-12 46 718 and DE-A-12 48 645. The sulfon-ation reaction is carried out with a mixture of gaseous sulfur trioxide and an inert gas which normally contains 21)00~8 from 2 to 8% by volume sulfur trioxide. The molar ratio of fatty acid alkyl ester to sulfur trioxide may be in the range from 1:1.1 to 1:1.8, but is preferably in the range from 1:1.2 to 1:1.5. Air i5 preferably used as the inert gas in industrial processes. The reaction temperature may be in the range from 10 to 130'C. The sulfonation i5 preferably carried out at 60 to 90'C. The process temper-ature may either remain constant or may be increased in stages. Falling film and cascade reactors have proved suitable for continuously carrying out the sulfonation process.
Immediately after the sulfonation reaction, the reaction mixture obtained is subjected to an after-reaction (ageing) for 10 to 30 minutes at 70 to 90C. The reaction product is then bleached and neutralized in the usual way.
Bleaching may be carried out in known manner with hydrogen peroxide and/or sodium hypochlorite in aqueous medium. The neutralization of the acidic reaction product may be carried out both before and after bleaching.
Bleaching with hydrogen peroxide before neutralization is described, for example, in DE-B-ll 79 931. DE-A-12 34 709 describes a combined bleaching treatment in which the treatment of the acidic reaction product with aqueous hydrogen peroxide is followed by neutralization of the partly bleached sulfonation product which is then subjected to a concluding bleaching process either again with hydro-gen peroxide or, better still, with sodium hypochlorite.
According to DE-A-33 19 591, the crude sulfonation product is first subjected to preliminary bleaching with sodium hypochlorite in a neutral to mildly alkaline aqueous medium, after which the salt paste is mildly acidified and rebleached with hydrogen peroxide or compounds yielding hydrogen peroxide.
The neutralization of the acidic sulfonation products is carried out with aqueous potassium hydroxide solutions and preferably with aqueous sodium hydroxide solutions.
The bleaching and neutralization conditions should be ~,,, ,.,.,~ , . .. .........................

. . - ., .
s,. .~

2000Z~8 5~ y~ .h~t~r, ~rl~ h ~ ps~ lo l h ~ p ~ . 6 ~ g la l y X~U 1 Q~ u 1 ~
r~ff~ ~J~r~ J ~ lnlr~n~lon, ~ ddi-t:lon. ~ t' ~m~ll qu~n~ikler~ o~ r,~ y .~ ald2~ ac~rr~spond~ng ~o Pax~nu;l~ urp~ln~l.y t.. nc.~rea~ t:h~ ~tabil.Lt~ the :~utky .af.~ lkyl ~wter~ 0 oxlL~i~lnq ~r~c~: Or th-3 ru~ tr:ioxi~. In t:h~ Gul ~OI~r?ltiO7l ol~ the ~tt:y ~ld al~yl e~ in 1;he ~re~ence ol' ~atty ~c:id amide~ co~rts-~;p~ndin~ to ~or~,ula I, ~tion o~ cul~.r-ac:t~l/e 1~ ~ly~ Xy ~n~ ~xr~ ,t~iv~_ive~ np~ t~ b~
ly ~uppr~e~qad ~o th~t~ ul~rn~1:y ~c:icl o~t~r 81~11t8 of ~cis~ ry ~ or ~ual It~ an ~ ~h~is~
Ir~ the ollowln~ ~x~mpl~ ul~Jrl~t~n ~ ~h~ ~atty ~oi.~ al)~:yl ~qte.r An~ wor}ci~g up ~ th~ cruda ~u1rona~lon procluct ~r~ ~axried o~ by t~ f~ w1ng~ ~t~nd~r~ thod:
~n A 1 l~t*r ~ndar~l rehctor ~quipp~d wl~h 9 hsat1ng and ~oo.l itlg ~ck3t ~ncl ~ g~ 1 t~ p.;p~, :L mol ~a~y ~
~1~;y1 ~3t:er i~ ~nt~s~iv~1}r mlxed wit~ the p~rti~ r ~tty ~1cl ;~m1~ erm.ll1a I Qlrvi~e~gQc3 ln th~ qu~a t:lty ~nv 1 3age~
.~o and th~ x~suît1n~ s~ s~re nQ~td t~ C. Th~ ~t~y z~c1d r.~ wa~ h~n ~ c'c~d wl~s ~ ul~r trl~xi~ c~ OA~ O~ 1rIY t~ ~ mO1~A- r;~
.~he ~u1~ur- trioxitl~ wa~ ~xpell~d ~r~m el c~re~pond~ng ~u~.r~t.i.~ c~l~u~! by heat~ ng, ~.~ ltA~t~ ~t~l nlt:rog~n t~ a ~c~nc~ln~ra~ion o~ 5~ hy i~lun~ an~ in~r~d~ed ~r~o th~ f~tty d ~ 3rt ~tt~!r r>~ r ~ perl~a ~ m.~ tes, 'I~h~ ~mp~r~
atur~ ~E th~ r~c~.on mlxtur~ u~ ~ept below gO~C.
A~ su~oF~a~n, the ~ e ~u1f~n~t~on pr~ ua~ WAC
t; ~ c~e~ rl ~ti~r~r~ tl~ Qr l~ n~r.~t~ at ~o~

3~ in a b~t~r ~A~z.~h ~d ~ th~n nnutrk11z~cl by s~irr1ng tnto a ~in:l uti~.)n ot 4,1 ~ mc~1) fsodlum hy~roxlde ~n 500 ~1 uater .
~for2~ th* c~lu~ s1u~e; w~re d~rmIn~, tl~ ulfo-at~.y acid ~' kyl ~t~r ~;~d~u~ lt w~* ~ ch~d ~or 120 minut6~a ~f~ t.h~ adæiti~s~ o~ ~ by ~rsight, b~s~d on u~h~ng~a~t1ve ~h~tnnce, o~ ~o~1urQ h~poc~ rit{~.
.h~ color valu~ me~u~en~n~.~ w~r~ c~rri~d O~lt ~i:` `

. .....
. .~ . ..
photometrically ~y the Klett method at an anlonic surfac-tant concentration of 5% by weight and at pH 7 using a 1 cm round cell and a blue filter (400 to 465 nm).
In the comparison tests, the fatty acid alkyl ester was sulfonated without the addition of fatty acid amides corresponding to formula I.

EXAMPLES
EXAMPLES 1 and ~
The starting material used was a tallow fatty acid methyl ester (chain length distribution in the fatty acid residue: 50% by weight C16, 50% by weight C18: saponification value 198; iodine value 0.2). This starting material had been obtained from high-quality beef tallow (fancy tallow);
its fatty acid component had only been slightly damaged by production and working up.
The tallow fatty acid methyl ester was reacted with sulfur trioxide by the standard method described above in the presence of 0.25 to 1.50 mol-% stearic acid amide or stearic acid N,N-dimethylamide. The Klett color values observed for the-resulting ~-sulfofatty acid methyl ester sodium salts are shown in Table I in relation to the color value of an end product obtained without the addition of a fatty acid amide.

200(~8 Table I
Sulfonation in the presence of stearic acid amide or stearic acid N.N-dimethylamide _ . . . _ .
Example Mol-% Klett color value 1 Cl7H3sCNH2 0.25 24 0.50 20 0.75 24 l.00 21 1.50 30 ~:
~, 2 C~7H3scoN(cH3)2 0.25 21 0.50 18 0.75 ll ~-1.00 13 -: :
1.50 18 --~:

Comparison 1 no addition - 42 ~ ~.

- :-~ :
EXAMPLES 2 to 22 The starting material used was a tallow fatty acid methyl ester (chain length distribution in the fatty acid residue: 50% by weight C16, 50% by weight C1B; saponification :
value 198; iodine value 0.9). This starting material had been obtained from low-quality beef tallow (A tallow); the -fatty acid component had been damaged by production and -::
working up.
The tallow fatty acid methyl ester was reacted with sulfur trioxide by the standard method described above in the presence of quantities of O.S and 1.0 mol-% of the fatty acid amides of formula I shown in Table II and worked up to the corresponding ~-sulfofatty acid methyl ester sodium salts. The Klett color values of the respective end ~ :

~ .. .. .

f~O()()Z78 products are shown in Table II by comparison with the color value of an end product which had been obtained without the addition of a fatty acid amide.

~.~ ,""" "~ ... , ,..,: ,~ : , ~. , , ., - .

q: ~. --., ~ . . .. .

: ZO 0 V ~ 7 Table II
Sulfonation in the presence of fatty acid amides corre-spondina to formula I

R1 _ C - N /
\ R3 , Example Rl R2 R3 Klett color value 0.5 mol-% 1.0 mol-~
, 3 C17H3s H H 93 76 4 Cl7H3s CH3 H 90 74 C17H3s nC3H7 H 90 81 6 C17H3s i-C3H7 H lO0 85 7 C17H3s nC4Hs H 105 87 8 c17H3s iC4Hs H 108 91 9 CSH1l CH3 CH3 108 82 C1lH~ CH3 CH3 110 82 11 C13H27 CH3 CH3 lO9 79 12 ClsH3~ CH3 CH3 110 75 13 Cl7H3s CH3 CH3 88 68 14 C2lH43 CH3 CH3 108 85 C17H3s nC3H7 n-C3H7 95 79 16 C17H35 i-C3H7 i-C3H7 98 78 17 C18H3s nC4Hs n C4Hs 105 87 18 C17H35 iC4Hs i-C4H9 99 79 19 C17H35 - (CH2)4 - 97 C17H35 - (CH2)5 - 103 75 21 C17H35 ~ (CH2)2 - ~ (CH2)2 86 71 no addition 163 .. . . ~
.. ..

11 :

Claims (6)

1. In a process for the production of light-colored .alpha.-sulfofatty acid alkyl ester salts wherein a fatty acid alkyl ester is sulfonated with gaseous sulfur trioxide to produce a sulfonated reaction product and wherein the sulfonated reaction product is subsequently aged, bleached, and neutralized to form an .alpha.-sulfofatty acid alkyl ester salt, the improvement comprising sulfonating said fatty acid alkyl ester in the presence of 0.25 to 1.5 mol-%, based on fatty acid alkyl ester, of at least one fatty acid amide of the formula I

(I) wherein R1 is a linear C5-21 alkyl radical, R2 and R3 are independently a hydrogen atom, a linear or branched C1-6 alkyl radical, or R2 and R3 together form a tetra- or pentamethylene chain of a heterocyclic ring system.

2. The process of claim 1 wherein said heterocyclic ring system contains an oxygen atom, a sulfur atom or an NH
group.

3. The process of claims 1 or 2 wherein R1 is a C15-17 alkyl radical.

4. The process of claims 1 or 2 wherein R2 and R3 are together or separately linear alkyl radicals.

5. The process of claims 1 or 2 wherein said fatty acid alkyl ester is a C1-4 alkyl ester of saturated C6-22 fatty acid.

6. The process of claims 1 or 2 wherein said fatty acid alkyl ester is a methyl ester.