AU607044B2 - A process for the production of unsaturated fatty acid lower alkyl ester sulfonates - Google Patents

Description

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7044 S F Ref: 75087 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

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C' Complete Specification Lodged: Accepted: Published: Priority: Related Art: Class Int Class Thjs clc~mcnt contains tle alflen( ri'fl Ir ade undcr SCcjg 4 ar.j is corrc print ing, Name and Address of Applicant: Address for Service: Henkel Kommanditgesellschaft auf Aktien Henkelstrasse 67 Dusseldorf FEDERAL REPUBLIC OF GERMANY Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: A Process for the Production of Unsaturated Fatty Acid Lower Alkyl Ester Sulfonates The following statement is a full description of this invention, including the best method of performing it known to me/us oslaa~':eT 5845/3 Signa tre -of Declarant Dr. Georg Zeit -I I -i; '1 r o r D 8190 -_I A process for the production of unsaturated fatty acid lower alkvl ester sulfonates Abstract ~c' 0C ICI

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V eo e K~ c V CC fo C V V C Unsaturated fatty acid lower alkyl ester sulfonates may be produced by reaction of a mixture of unsaturated and saturated fatty acid lower alkyl esters with gaseous sulfur trioxide in a molar ratio of sulfur trioxide to unsaturated fatty acid lower alkyl esters of 1.0 to 1.2 and at temperatures of 15 to 25°C, the product obtained being neutralized and hydrolyzed immediately after sulfonation with aqueous bases at a pH value maintained at at least 6.

The unsaturated fatty acid lower alkyl ester sulfonates obtained have a particularly low content of fatty acid sulfonate disodium salt.

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Henkel KGaA D 8190 p 12740/88 M/VM/MH 9.2.1988 A process for the production of unsaturated fatty acid lower alkyl ester sulfonates.

This invention relates to a process for the production cc( of unsaturated fatty acid lower alkyl ester sulfonates by

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Sc C reaction of a mixture of unsaturated and saturated fatty acid lower alkyl esters with gaseous sulfur trioxide in a cc c

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c 5 molar ratio of sulfur trioxide to unsaturated fatty acid

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Sc lower alkyl esters of 1.0 to 1.2.

SEP-A 0 130 753 describes the process of the type mentioned above, although the object in that case is to i obtain substantially complete sulfonation of the unsaturated fatty acid esters. Obtaining such high degrees of sulfonation (based on the unsaturated fatty acid esters) requires drastic reaction conditions, including for example I a large excess of sulfur trioxide (based on unsaturated components) and high sulfonation temperatures. Chemical separation aids, such as ethylene glycol, propylene glycol and the like, are used to separate the unsaturated fatty acid lower alkyl ester sulfonates from the unreacted i saturated fatty acid esters after neutralization and hydrolysis. Similar sulfonation and separation processes are also known from DE-A 35 37 190 and 36 06 868.

In the reaction of unsaturated fatty acid lower alkyl esters with sulfur trioxide, in contrast to the sulfonation of saturated fatty acid esters (a-ester sulfonation), the attack of the sulfur trioxide takes place at the reactive C=C-bond and, after alkaline hydrolysis, leads to ester

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2sulfonates containing an internal sulfonate group. Alkene and hydroxyalkane fatty acid ester sulfonates are formed as the main products. In a secondary reaction, the sulfur trioxide is introduced into the ester function with formation of a mixed anhydride which, formally, is formed from sulfonated unsaturated fatty acid and methyl sulfuric acid. During the alkaline hydrolysis, this mixed anhydride decomposes into methyl sulfate and fatty acid sulfonate disodium salt (hereinafter referred to as disalt). The salts are also formed during the hydrolysis of the ester bond of the fatty acid lower alkyl ester sulfonates, i.e. during the hydrolysis of the primary sulfonation products. The presence of relatively large quantities of disalt in unsaturated fatty acid lower alkyl ester sulfonates, of which the formation can never be completely suppressed, Is undesirable for various rsasons.

The present invention relates to a process of the type mentioned at the beginning by which the disalt cont:nt of unsaturated fatty acid lower alkyl ester sulfonates can be considerably reduced.

This object is achieved by a process of the type mentioned at the beginning in which the reaction with sulfur trioxide is carried out at temperatures of 15 to 25°C and, immediately after sulfonation, the product obtained is neutralized with aqueods bases at a pH value of at least 6 and "cc hydrolyzed, According to a broad form of this invention there is provided a process for the production of unsaturated fatty acid lower alkyl ester sulfonates by reaction of a mixture of unsaturated and saturated fatty acid lower alkyl esters with gaseous sulfur trioxide in a molar ratio of sulfur Strioxide to unsaturated fatty acid lower alkyl esters of 1.0 to 1.2, I characterized in that the reaction is carried out at temperatures of 15 to S 25°C and, immediately after sulfonation, the product obtained is neutralized and hydrolyzed with aqueous bases at a pH value maintained at at least 6.

The products obtained by this process show the low disalt contents mentioned and surprisingly little discoloration.

The sulfonation of the mixtures of unsaturated and saturated fatty acid lower alkyl esters used with gaseous sulfur trioxide may be carried out in typical sulfonation reactors, more especially of the falling-film type. The sulfur trioxide used is diluted with air or nitrogen, preferably being used in the form of a gas mixture D 8190 containing approximately 1 to 10% by volume sulfur trioxide.

Bases suitable for neutralization and hydrolysis are oxides or hydroxides of alkali metals, such as sodium, potassium or lithium, or of alkaline earth metals, such as magnesium or calcium, or organic bases, such as ammonia, ethanol amine, diethanol amine or triethanol amine. It is preferred to use aqueous sodium hydroxide.

j It should be emphasized that the sulfonation product 10 obtained by the process according to the invention is j immediately subjected to neutralization and hydrolysis, i.e. in contrast to standard sulfonation processes for esters of saturated fatty acids, there is no after-reaction of the sulfonation product before hydrolysis and neutralization.

In one preferred embodiment of the continuous sulfonation and neutralization process according to the invention, the sulfonation product is neutralized and hydrolyzed at at least 70°C while aqueous bases are introduced to maintain a pH value -of 6 to 8. The upper limit to the hydrolysis temperature is determined by the boiling point of the water. However, the hydrolysis may also be carried out in pressure reactors at temperatures of more than 100 C.

Maintenance of the pH- value. indicated is critical. If, for example, the neutralization step only is carried out with no further addition of base during hydrolysis, the pH value of the reaction system falls rapidly to below 6 due to rearrangement reactions of the sulfonation products, so that disalt formation is promoted. In addition, disalt formation is also promoted for the above reasons if the pH value of the reaction system stays above 8 for prolonged periods.

In another advantageous embodiment of the invention for discontinuous operation, the sulfonation product is D 8190 4 introduced into an aqueous solution of the base, the molar ratio of base to sulfur trioxide or sulfone groups in the sulfonation product being more than 1:1 up to 1.3:1 and sI more especially 1.1 to 1.3. Although, in this variant of the process, neutralization and hydrolysis initially take place at pH values above 8, the pH value soon falls below this unfavorable range in this embodiment.

There is normally no need for the unreacted, saturated fatty acid alkyl esters to be subsequently separated off from the reaction mixture obtained. However, in cases where it is desired to separate these non-sulfonated products, it is possible in another advantageous embodiment of the invention to separate the neutralized and hydrolyzed sulfonation product into two phases at temperatures of to 80*C and more especially at temperatures of 50 to in the absence of chemical phase separation aids, one of these two phases essentially containing the sulfonated, unsaturated fatty acid lower alkyl ester sulfates and the other phase essentially containing the unsulfonated, saturated fatty acid lower alkyl esters.

In another advantageous embodiment of the invention, mixtures of saturated and unsaturated C 16 -Czz fatty acid lower alkyl esters containing at least 40% by weight and more especially 70 to 90% by weight, based on the total 25 weight of the fatty acid esters, of monounsaturated Cr 1 -Cz fatty acid esters are used for the sulfonation. Fatty acid Sester cuts rich in oleic acid are normally used, although fatty acid ester cuts rich in petroselic acid and/or erucic acid may also be used.

In another advantageous embodiment of the invention, mixtures of fatty acid methyl esters are used.

The unsaturated fatty acid lower alkyl ester sulfonates produced in accordance with the invention may be used as surface-active products.

The invention is illustrated by the following i~ D 8190 Examples.

Example 1 The starting material used was a fatty acid methyl ester (acid value 1.0; saponification value 192 197; iodine value 84 92), in which the fatty acid component had the following composition (in percent by weight): C12 saturated 0 2

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14 saturated 2 5

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1 5 saturated 0 1 C16 saturated 4 6

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1 saturated 1 3 C18 saturated 1 3 S C20 saturated 0 2 SCz2 saturated 0 2 C16 monounsaturated 4 6 C18 monounsaturated 63 73 C18 diunsaturated 7 12 The sulfonation reaction was carried out in a glass falling-film reactor consisting essentially.of an.1100. mm.

long tube with an internal diameter of 6 mm surrounded by a heating and cooling jacket. The reactor was provided at CC, its head with a feed attachment for the ester starting material and with a gas inlet pipe. Gaseous sulfur trioxide produced by heating of oleum was used in the form i 25 of a mixture with nitrpgen by volume S03).

The fatty acid methyl ester mixture was introduced at i a constant rate of 550 g/h. The introduction of the sulfur trioxide/nitrogen mixture was regulated in such a way that the molar ratio of sulfur trioxide to unsaturated fatty acid methyl esters was 1.1. The reaction temperature was kept at 15'C by means of a water circuit in the reactor jacket.

On leaving the reaction zone, the reaction mixture was collected in a glass beaker equipped with the electrode of a pH meter and with a stirrer. The reaction product 6 D 8190 i accumulating was immediately neutralized to a pH value of i 7 +1 by addition of 25% by weight aqueous sodium hydroxide V solution.

j For hydrolysis, the neutralized reaction product was heated in portions for 6 hours to 90*C, the pH value of the solution being kept constant at 7 +1 by addition of 25% by weight sodium hydroxide solution. The aqueous phase cooled to room temperature was then extracted with petroleum ether.

A washing-active substance content (WAS content) of 37.2% by weight was determined in the clear aqueous phase by Epton titration, 5.6% by weight of the WAS consisting of the disodium salt of the sulfonated fatty acids.

The proportion of unreacted starting material (essentially methyl esters of the saturated fatty acids) in the hydrolysis product was determined by evaporation of the solvent from the petroleum ether extract and amounted to 11.3% by weight.

Example 2 The fatty acid methyl ester described in Example 1 was sulfonated as in Example 1 at 15"C and at a molar ratio of SO, to unsaturated ester of 1:1.

For hydrolysis, the neutralized reaction product was S 25 heated for 4 hours to A WAS content of 28.1% by weight was determined in the aqueous solution obtained, 14% by weight of the WAS consisting of the disodium salt of the sulfonated fatty acids. The proportion of unreacted starting material in the aqueous solution amounted to 10.0% by weight.

Example 3 The fatty acid methyl ester described in Example 1 was sulfonated as in Example I at 15*C and at a molar ratio of SO, to unsaturated ester of 1.2.

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D 8 1 9 0 7 SFor hydrolysis, the neutralized reaction product was heated for 4 hours to A WAS content of 30.5% by weight was determined in the aqueous solution obtained, 14% by weight of the WAS consisting of the disodium salt of the sulfonated fatty I acids. The proportion of unreacted starting material in the aqueous solution amounted to 9.0% by weight.

Example 4 The fatty acid methyl ester described in Example 1 was sulfonated as in Example 1 at 15°C and at a molar ratio of S03 to unsaturated ester of 1.2.

The resulting sulfonation product was collected in a glass beaker and introduced with stirring into such a quantity of 25% by weight sodium hydroxide solution that the molar ratio of NaOH to SO 3 taken up was 1.2.

A WAS content of 22% by weight was determined in the clear solution obtained. A sample of this solution was heated for 8 hours to 90°C. Thereafter the WAS content was still 22% by weight.

Example The starting material used was a fatty acid methyl ester (acid value 1.0; saponification value 193 199; iodine value 45 53),,in which the fatty acid component had the following composition (in percent by weight): C1I saturated 2 C14 saturated 2 7 C1 5 saturated 0 2 S 30 C16 saturated 25 33 C1 saturated 1 3 Ci8 saturated 15 19

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2 0 saturated 0 2 Cz2 saturated 0 2 Ci1 monounsaturated 1 3 'i II~ LIP* 8 D 8190

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18 monounsaturated 44 48

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1 diunsaturated 2 4 In the same way as described in Example 1 this fatty acid methyl ester was reacted with sulfur trioxide at in a molar ratio of SO3 to unsaturated ester of 1.2. The reaction product accumulating was immediately neutralized continuously to a pH value of 7 +1.

For hydrolysis, the neutralized reaction product was heated for 4 hours to 90"C under the conditions described in Example 1. The mixture was then cooled to 70°C, phase separation occurring. The aqueous phase was separated from the oily phase by means of a separation funnel and, after cooling to room temperature, was extracted with petroleum ether.

A WAS content of 18.5% was determined in the aqueous phase by Epton titration.

The proportion of unreacted starting material in the aqueous phase separated off from the hydrolysis product was determined by evaporation of the solvent from the petroleum ether extract and amounted to 13.5% by weight, based on

WAS.

Claims (8)

1. A process for the production of unsaturated fatty acid lower alkyl ester sulfonates by reaction of a mixture of unsaturated and saturated fatty acid lower alkyl esters with gaseous sulfur trioxide in a molar ratio of sulfur trioxide to unsaturated fatty acid lower alkyl esters of to 1.2, characterized in that the reaction is carried out at temperatures of 15 to 25°C and, immediately after sulfonation, the product obtained is neutralized and hydrolyzed with aqueous bases at a pH value maintained at at least 6.

2. A process as claimed in claim 1, characterized in that, for continuous sulfonation and neutralization, the Ssulfonation product is neutralized and hydrolyzed at at least 70"C while aqueous bases are introduced to maintain a pH value of 6 to 8.

3. A process as claimed in claim 1, characterized in that, for discontinuous operation, the sulfonation product is introduced into an aqueous solution of the base, the molar ratio of base to sulfur trioxide or sulfone groups in the sulfonation product being more than 1:1 up to 1.3:1 and more especially 1.1 to 1.3.

4. A process as claimed in at least one of claims 1 to 3, characterized in that the neutralized and hydrolyzed sulfonation product is separated at temperatures of 50 to and more especially at temperatures of 50 to 70'C into 'two phases essentially containing only unsaturated, sulfonated fatty acid lower alkyl esters and unsulfonated, saturated fatty acid lower alkyl esters, phase separation taking place in the absence of chemical phase-separation aids.

A process as claimed in at least one of claims 1 to 4, characterized in that mixtures of saturated and unsaturated C 1

6-Ca fatty acid lower alkyl esters containing at least i D 8190 by weight, more especially 70 to 90% by weight, based on the total weight of fatty acid esters, of monounsaturated 2 fatty acids are sulfonated. 6. A process as claimed in at least one of claims 1 to chara.cterized in that mixtures of saturated and unsaturated fatty acid methyl esters are used.

7. A process for the production of unsaturated fatty acid lower alkyl ester sulfonates by reaction of a mixture of unsaturated and saturated fatty acid lower alkyl esters with gaseous sulfur trioxide in a molar ratio of sulfur trio7ide to unsaturated fatty acid lower alkyl esters of to 1-2, substantially as hereinbefore described with reference to any one of the Examples.

8, The prod'ict of the process of any one of claims 1 to 7. DATED this EIGHTH day of FEBRUARY, 1989 Henkel Kommanditgesellschaft auf Aktien Patent Attorneys for the Applicant SPRUSON FERGUSON