WO2014072840A1

WO2014072840A1 - Flowable, high active, aqueous fatty alkyl sulfates

Info

Publication number: WO2014072840A1
Application number: PCT/IB2013/052211
Authority: WO
Inventors: Ramakrishnan GOPALAKRISHNAN; Shekhar UNNATHAN
Original assignee: Galaxy Surfactants Ltd.
Priority date: 2012-11-12
Filing date: 2013-03-20
Publication date: 2014-05-15

Abstract

The present invention relates to a process for preparing high-concentration, flowable aqueous fatty alkyl sulfate solution, said process comprises (i) ethoxylation of fatty alcohol with very low of about 0.3 to about 0.8 moles of ethylene oxide, and (ii) sulfating the ethoxylated fatty alcohol with specific reaction conditions, and (iii) neutralizing the sulfation product with an aqueous base. The obtained fatty alkyl sulfate solution contains at least 65% by weight of mixture of fatty alkyl sulfates and fatty alkyl ether sulfates in a weight ratio in the range from about 80:20 to about 50:50 wherein the average number of moles of ethylene oxide (EO) of the mixture is between 0.3 to 0.8; less than 3 ppm of dioxane; and water, and wherein the solution does not contain any antimicrobial or preservatives and is homogeneous, flowable and pumpable at 25°C.

Description

FLOWABLE, HIGH ACTIVE, AQUEOUS FATTY ALKYL SULFATES

FIELD OF THE INVENTION

The present invention relates to highly concentrated, aqueous solutions of fatty alkyl sulfates which are homogeneous, flowable, and pumpable at room temperature. It particularly relates to a process for preparing homogeneous, flowable, and pumpable aqueous solutions of fatty alkyl sulfates with an active ingredient content of atleast 65% by weight.

BACKGROUND AND PRIOR ART OF THE INVENTION

Fatty Alkyl Sulphates (FAS) are widely used class of anionic surfactants. They are suitable for numerous commercial applications by virtue of their excellent foaming properties and their cleaning effect. They are used in household cleaning products, personal care products, institutional cleaners and industrial cleaning processes, as industrial process aids in emulsion polymerisation and as additives during plastics and paint production. Uses in household cleaning products include laundry detergents, hand dishwashing liquids, and various hard surface cleaners. Their neutral flavor, their acceptable compatibility with mucous membrane, and their growth-inhibition effect on the bacteria responsible for plaque also make them particularly suitable for use as a surfactant component in the production of oral hygiene and dental care preparations.

The fatty alkyl sulfates (FAS) are produced industrially, generally by sulfation of suitable fatty alcohols with gaseous SO_3. The fatty alkyl sulfuric acid which forms as crude product in the process is then neutralized in the presence of suitable alkalis, preferably aqueous sodium hydroxide, to give the fatty alkyl sulfates. At the end of such processes, surfactant-containing aqueous preparations with a maximum of 30% by weight of fatty alkyl sulfates are obtained. However, the demerit associated with such low-concentration FAS solution is its transportation; in so doing only small amounts of active substance (maximum 30% by weight) but large amounts of water are transported. Also, end-use formulators have to face the problem of storing and handling it in bulk quantity. Furthermore, 30% aqueous FAS require antimicrobial agents or preservatives to be added to protect it from microbial contamination. One of the ways to overcome the high transportation cost and other problems associated in using low-concentration FAS, is to prepare aqueous solutions of FAS with high concentration having minimum amount of water in it. However, the smooth production and processing of aqueous FAS with high active ingredient content is often hindered by the fact that these solutions are very viscous and not flowable. Aqueous compositions of FAS are generally easily flowable at room temperature up to an active ingredient content of about 30% by weight and display viscosities of up to 500 mPa.s (by Brookfield Viscometer). It tends to be non-fluid, that is, they either gel or paste and become non-flowable and too viscous to pump at ambient room temperature, when the total solids or active content exceeds about 35% by weight. The viscosity of more highly concentrated aqueous compositions of FAS with an active ingredient content of more than 30% by weight is temperature dependent, so that these compositions can be made to flow by heating, for example sodium lauryl sulfate with 70% active content is flowable at about 45°C. However, the heating of such compositions is associated with many problems such as heating containers are not universally available, lots of energy is being utilized for heating, providing heating system to the material during transportation is a cumbersome task, and moreover, heating results in decomposition of the product.

There has been no shortage of attempts in the past to solve the problem posed by the high viscosity of high-concentration FAS solutions or pastes. Attempts have been made to overcome this problem by adding fluidizers to the reaction mixture, for example, either during or after formation of the surfactant in an aqueous medium, or by introducing special additives or solvents. Use of secondary alkane sulfonates and hydroxycarboxylic acid salts as viscosity-reducing agents for anionic surfactant concentrates is known from German patent applications DE 3447859 (Henkel) and DE 2251405 (Albright & Wilson). Other known viscosity reducers are sulfonated aromatic compounds as disclosed in DE 2305554 (Albright & Wilson), cumene sulfonate or acidic phosphoric acid esters as taught in DE 1617160, polyhydric alcohols, carboxylic acids or esters thereof as claimed in EP 08060 or mono and/or disulfates of polyalkylene glycol ethers as claimed in EP 024711 (Henkel). Pending US Pat. Pub. No. 2010/0303739 (Cognis) discloses that adding certain polyol and/or betaine and/or fatty acid alkylamide in FAS solution reduces its viscosity and allows making highly concentrated FAS solution or paste which is pumpable. US Pat. No. 5,304,669 (Henkel) teaches about a process for the production of alkyl sulfate pastes having improved flow properties by co-sulfation of aliphatic alcohols and unsaturated fatty acid glyceride esters and subsequent neutralization thereof in such a way that pastes with solids content of 30-80% by weight are obtained. While some measure of success has been achieved, but such large amounts of additives or fluidizers are difficult or costly to remove from the medium and are always remain in the product. Some fluidizers may also introduce reaction byproducts and components that can interact with other ingredients in the formulation or interfere with the purpose for which the surfactant is subsequently used. Additionally, some fluidizers may introduce toxicologically, physiologically, or environmentally unacceptable materials in the product.

There are prior arts which provide high solids or high active content anionic surfactants without using any viscosity regulators or additives, for example, US Pat No. 5,446,188 (Henkel) teaches co-sulfating mixture of unsaturated fatty alcohol and saturated fatty alcohol, and neutralizing to produce FAS pastes which are flowable and pumpable at low temperature. However, none of the patents discloses the art of making saturated and high active i.e more than 65% active FAS aqueous solution which is flowable at room temperature. Alternative way of making high concentration FAS is to remove the water in order to obtain dry products, which are easier to transport. The dried products in powder form are typically obtained by spray-drying. However, the spray-drying process requires capital investment, and is always an energy and time-consuming process which consequently makes the resultant product more expensive. Moreover, such dried powdered products give rise to the disadvantage of considerable dust emission in use and the unwanted entry of air into the product. To overcome the difficulties of powdered FAS, some FAS are made available in granular form. Granular form may, in particular, be suitable to improve the handling properties of the material while lowering or not increasing too much the cost of manufacturing or shipping. European patent application EP 403148 (P&G) describes a process for the production of FAS granules which are dispersible in cold water. It is known from European patent EP 0603207 (Henkel), that water-containing pastes of alkyl sulfates can be converted into granules of high bulk density by drying and simultaneous granulation in a continuous fluidized bed. To improve the solubility of the granules, mixtures of surfactants are used, for example, US Pat No. 6,780,829 (Cognis) relates to the use of olefin sulfonates in quantities of 3 to 25% by weight for improving the solubility of FAS granules in cold water.

While there are improvements happening in spray-drying and granulation, but these technologies still suffer from many demerits including the low temperature solubility. Moreover, these products can be sticky and there anti-caking agent has to be necessarily used which also contributes in increasing the cost of the sulfate product. Therefore, industry prefers aqueous FAS and is still finding ways to produce aqueous FAS solution which is highly concentrated and yet flowable and pumpable at room temperature. A major difficulty, though, is finding an inexpensive and efficient way to produce the said high active FAS aqueous solution or paste which is homogeneous, flowable and pumpable. Surprisingly, inventors of the present invention have found that the aqueous fatty alkyl sulphate solutions which are highly concentrated having atleast 65% by weight of active ingredient and yet homogeneous, flowable and pumpable at room temperature can be prepared by slightly modifying the fatty alkyl sulfates to convert some minor portion of it into ethoxylated fatty alkyl sulfates. This modification is done by direct and simple ethoxylation of fatty alcohols with very low moles of ethylene oxide followed by sulfation with certain reaction conditions and then neutralizing it with a base.

US Pat No. 6,313,085 (Cognis) teaches to prepare high-concentration flowable aqueous anionic surfactant mixture having solids content in the range from 50 to 80% by weight, comprising 60-90% by weight of alkyl ether sulphates and 10-40% by weight of alkyl sulphates. These are prepared by sulphating the mixture of fatty alcohol and ethoxylated fatty alcohol. Similarly, US Pat. No. 5,847,183 (Henkel) relates to high-concentration fatty alcohol (ether) sulfates which are obtained by co-sulfating mixtures of fatty alcohol and fatty alcohol ethoxylate. The claimed product is flowable at room temperature. According to this patent, fatty alkyl (ether) sulfates of comparable carbon chain length and degree of ethoxylation prepared by simple and direct ethoxylation of fatty alcohols followed by sulfation are present as cutting-resistant crystallized pastes which are non-flowable and pumpable. However, unexpectedly, the inventors of the present invention found that fatty alkyl sulfates having concentration of atleast 65% by weight of active ingredient can be made which are homogeneous, flowable and pumpable even at room temperature by simple and direct ethoxylation of fatty alcohols with very low of about 0.3 to 0.8 moles of ethylene oxide, followed by sulfation of the ethoxylated fatty alcohols with certain unique reaction conditions and then neutralizing the sulfated product with a base. SUMMARY OF THE INVENTION

The present invention relates to a process for preparing fatty alkyl sulfate aqueous solutions having active ingredient content of atleast 65% by weight and which is homogeneous, flowable and pumpable at room temperature i.e. 25°C.

These high-concentration and flowable fatty alkyl sulfate aqueous solutions are prepared by (i) ethoxylation of fatty alcohol with very low of about 0.3 to about 0.8 moles of ethylene oxide (EO), and

(ii) sulfating the ethoxylated fatty alcohol with specific reaction conditions, and

(iii) neutralizing the sulfated product with an aqueous base.

According to another embodiment of the present invention, it relates to said high- concentration aqueous solution of fatty alkyl sulfates which is a mixture of fatty alkyl sulfates and fatty alkyl ether sulfates present in a weight ratio in the range from about 80:20 to 50:50.

According to yet another embodiment, the process of the present invention provides fatty alkyl sulfate solution containing very low level of dioxane impurity which has never been achieved before in the prior art. It contains less than 3 ppm of dioxane, more preferably less than 2 ppm of dioxane.

OBJECTS OF THE INVENTION

It is an object of the present invention to overcome the drawbacks of the present invention. It is an object of the present invention to provide a process for preparing highly concentrated fatty alkyl sulfate aqueous solution, which is isotropic, flowable and pumpable at room temperature i.e. at 25°C without any externally added cosolvents, cosurfactants or viscosity modifiers.

It is an object of the present invention to provide a process for preparing fatty alkyl sulfate aqueous solution with active ingredient concentration of atleast 65% by weight. It is an object of the present invention to provide a process for preparing fatty alkyl sulfate aqueous solution which is a mixture of fatty alkyl sulfates and fatty alkyl ether sulfates present in a weight ratio in the range from about 80:20 to 50:50.

It is an object of the present invention to provide a process for preparing high- concentration, flowable aqueous fatty alkyl sulfates having saturated and linear fatty alkyl chain.

It is an object of the present invention to provide a process for preparing high- concentration, flowable aqueous fatty alkyl sulfate aqueous solution without having any antimicrobial or preservative.

It is an object of the present invention to provide a process for preparing high- concentration, flowable aqueous fatty alkyl sulfate aqueous solution containing less than 3 ppm of dioxane.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned before, the fatty alkyl sulfates (FAS) are produced industrially, generally by sulfation of suitable fatty alcohols with gaseous SO_3. Inventors of the present invention have found that by slightly ethoxylating the fatty alcohol followed by sulfating the ethoxylated fatty alcohols with SO₃ in a certain reaction conditions, allows to produce fatty alkyl sulfates which are highly concentrated and flowable at room temperature i.e. at about 25°C.

Thus, the present invention relates to a process for preparing highly concentrated fatty alkyl sulfate aqueous solutions which are homogeneous, flowable and pumpable at 25°C. These fatty alkyl sulfate aqueous solutions are prepared by (i) ethoxylation of fatty alcohol with very low of about 0.3 to 0.8 moles of ethylene oxide to produce ethoxylated fatty alcohol of formula (I) as per (eq.l)

A

R - OH + n H₂C - CH₂ ► R-(OCH₂CH₂)„-OH (eq.l) formula (I)

in which R is a linear saturated hydrocarbon radical containing 8 to 18 carbon atoms, and n is an average number of EO moles between 0.3 to 0.8, and

(ii) sulfating the ethoxylated fatty alcohol with S0₃/air mixture at a temperature from about 40°C to 50°C to produce sulfation product of formula (II) as per (eq.2),

R-(OCH₂CH₂)„-OH + S0₃ ► R-(OCH₂CH₂)„-OS0₃H (eq.2)

Formula (II)

wherein

mole concentration of S0₃ in S0₃/air mixture is from about 3.5 to 4.5%, and mole ratio of S0₃ to ethoxylated fatty alcohol is from about 1 :1 to 1: 1.1, and

(iii) neutralizing the sulfation product with an aqueous base as per (eq.3)

R-(OCH₂CH₂)„-OS0₃H + MOH ► R-(OCH₂CH₂)„-OS0₃M (eq.3) wherein M is an alkali metal, alkaline earth metal, ammonium or substituted ammonium;

Like other available ethoxylated fatty alkyl sulfates, the aqueous fatty alkyl sulfates of the present invention is also a mixture of fatty alkyl sulfates and fatty alkyl ether sulfates. Fatty alkyl ether sulfates are the fatty alkyl sulfates ethoxylated with certain number of moles of ethylene oxides. However, the fatty alkyl sulfates and fatty alkyl ether sulfates are present in a weight ratio in the range from 80:20 to 50:50. Such high amount of fatty alkyl sulfates in such type of mixtures was never achieved before. The active ingredient concentration of the flowable fatty alkyl sulfate solution obtained by the present inventive process is atleast 65% by weight, preferably atleast 68% by weight, and more preferably atleast 70% by weight. Since the aqueous fatty alkyl sulfates of the present invention is a mixture of fatty alkyl sulfates and fatty alkyl ether sulfates, the said active ingredient concentration is the sum of the concentration of both the said sulfates together. The range of the active ingredient concentration is between 65% to 80% by weight, preferably between 68% to 75% by weight.

The fatty alkyl sulfates of the present invention have a fatty alkyl chain containing 8 to 18 carbon atoms. Particularly, the fatty alkyl chain contains 12 to 18 carbon atoms, more particularly 12 to 16 carbon atoms, and still more particularly 12 to 14 carbon atoms. Typical examples of fatty alkyl chain include, caprylyl, capryl, lauryl, myristyl, cetyl, palmityl, stearyl, and the technical mixtures thereof obtained. Preferred examples are lauryl and coco fatty alkyl chain. Few prior art teaches to get the flowable fatty alkyl (ether) sulfates only if we produce a mixture of saturated and unsaturated or branched fatty alkyl chain sulfates using corresponding fatty alcohols. However, the process of the present invention allows to get the flowable fatty alkyl (ether) sulfates even if the fatty alkyl chain is full saturated.

As the formation of impurities is almost unavoidable in any reaction, the aqueous fatty alkyl sulfates obtained by the process of the present invention also contains certain impurities. The impurities mainly found in fatty alcohol (ether) sulfate products are unsulfated fatty (ether) alcohols and 1,4-dioxane. According to yet another aspect, the process of the present invention provides fatty alkyl sulfate solution containing very low level of dioxane impurity which has never been achieved before in the prior art. It contains less than 3 ppm of dioxane, more preferably less than 2 ppm of dioxane.

1,4-dioxane is the most undesirable by-product or impurity formed during the sulfation of ethoxylated alcohols is 1,4-dioxane. 1,4-Dioxane (CAS No. 123-91-1) was declared a Priority Existing Chemical on 3rd May 1994 due to concerns over possible human carcinogenicity, its potential for widespread occupational and public exposure and high degree of partitioning to, and persistence in the aquatic environment. The health risk from 1 ,4-dioxane in laundry detergents has become a matter of considerable debate among public health experts and advocates. The same study group has also tested many other cosmetic and personal care products, as well as other types of household cleaning products for the presence of this chemical. High enough amounts were found throughout the testing that many companies have come under legal attack for poisoning consumers. Clearly, the risk from its presence in children's bubble baths, shampoos and adult products such as body wash seems obvious to the public since the products are applied directly to the skin. In this case, under pressure by the California attorney general and public interest groups' legal arms, many manufacturers began eliminating or markedly reducing the amount of dioxane in their products. Fatty alkyl ether sulfates available in the market contain about 7-10 ppm of dioxane. Final shampoos made using 14-16% of these fatty alkyl ether sulfates contain more than 1 ppm of dioxane which is still a high level to accept. Hence, many attempts have been already made and still going on to remove the dioxane from fatty alkyl ether sulfates upto its trace level. US Pat. No. 4,954,646 (Hoechst), EP Pat. No. 0052801 (Henkel), Japanese Pat. No.2007131573 (Lion Corp) all teach about the various ways of reducing the dioxane content in alkyl ether sulfate products but all the attempted ways did not able to lower the dioxane content to its trace level.

Thus, all the ethoxylated products contain dioxane as an unavoidable impurity. Although the process of the present invention involves ethoxylation and sulfation reactions, it is ensured to limit the dioxane content to a very low level by carrying out the following process steps:

1. ethoxylation of fatty alcohols using very low amount i.e. from about 0.3 to 0.8 moles of ethylene oxide and preferably 0.4 to 0.6 moles of ethylene oxide.

2. sulfation of ethoxylated fatty alcohols under specific reaction conditions in terms of SO₃ mole concentration in air, sulfation temperature, and the mole ratio of SO₃ to ethoxylated fatty alcohol.

3. removal of remaining dioxane by applying pressure of about 30-100 mmHg (i.e. applying vacuum) during the neutralization step. The three specific reaction conditions involved in the process of the present invention which are responsible to produce highly concentrated, homogenous, flowable and yet very low dioxane containing fatty alkyl sulfate aqueous solutions are as follows:

1. mole concentration of SO_j in air: sulfating the ethoxylated fatty alcohol with 3.5 to 4.5% mole concentration of SO₃ in air provides a good quality sulfated product. Mole concentration lower than 3.5%, results in decrease in the rate of reaction and the reaction does not complete. If the mole concentration of SO₃ in air is higher than 4.5% then the rate of reaction will be too high, resulting into over-sulfation and leading to high colouration of the product and also the level of impurities including dioxane will increase.

2. sulfating reaction temperature: sulfating the ethoxylated fatty alcohol at a temperature from about 40°C to 50°C is required to get a proper sulfated product. Temperature lower than 40°C increases the condensation of SO₃ into droplets which leads to incompletion of reaction, whereas reaction temperature higher than 50°C results to over-sulfation and leading to high colouration of the product and also the level of impurities including dioxane increases.

3. mole ratio of SO^ethoxylated fatty alcohol: mole ratio of SO₃ to ethoxylated fatty alcohol of from about 1: 1 to 1: 1.1 is required to maintain the colour and impurity level within the acceptable limit. Below 1: 1 ratio, the sulfation reaction does not complete and results in lower yields, whereas ratio above 1:1.1 results into high colouration of the product and also the level of impurities including dioxane increases.

Following above steps, results in producing fatty alkyl sulfate solutions containing very low amount of dioxane. It contains less than 3 ppm of dioxane, preferably less than 2 ppm which ultimately provides a ultra low or trace amount of dioxane in the final shampoo, body wash or other personal and home care cleansing formulations. Ultra low or trace amount means less than 0.5 ppm of dioxane, preferably less than 0.3 ppm of dioxane and more preferably less than 0.2 ppm of dioxane. Such low quantity of dioxane in personal care and home care cleansing formulations is unexpectedly obtained due to the use of aqueous fatty alkyl sulfates which is produced by the process of the present invention.

Another benefit of present invention is that the high-concentration, flowable aqueous fatty alkyl sulfate solution obtained does not require any antimicrobial system and is self- preserving due to its high active and high solids content.

Accordingly, the present invention relates to a process for preparing an aqueous solution of fatty alkyl sulfates, the solution comprising

(i) atleast 65% by weight of mixture of fatty alkyl sulfate and fatty alkyl ether sulfate in a weight ratio in the range from about 80:20 to about 50:50, wherein the average number of moles of ethylene oxide (EO) of the mixture is between 0.3 to 0.8; and

(ii) less than 3 ppm of dioxane; and

(iii) water

wherein the solution does not contain any antimicrobial and is homogeneous, flowable and pumpable at 25°C.

The pH of the fatty alkyl sulfate solution obtained by the present invention is between 6 to 9.

The novel process to obtain the novel fatty alkyl sulfates of the present invention can be better understood by the following examples.

EXAMPLES

Examples 1, 2, 3, 4 and 5 describe the process of manufacture of novel highly concentrated, flowable fatty alkyl sulfates ethoxylated with 0.3 to 0.8 moles of EO.

Examples 6 to 11 illustrates the comparative examples.

Examples 12 and 13 describes the preparation of personal care formulations (e.g. shampoo) incorporating the novel compounds of the present invention. Example 1 : 0.5 mole ethoxylated sodium lauryl (C₁₂-14) sulfate

It involves two steps: a. Preparation of 0.5 mole ethoxylated lauryl alcohol, and

b. Sulfation and neutralization of 0.5 mole ethoxylated lauryl alcohol a. Preparation of 0.5 mole ethoxylated lauryl (CI¾.H) alcohol:

5975 kg (30.8 kmole) of C12-14 lauryl alcohol was heated to 160°C in a pre-treatment vessel. After the temperature was achieved, vacuum was applied to pre-treatment vessel for removing the moisture from lauryl alcohol. 10 kg of suitable catalyst was then added and the mass was mixed well at the same temperature. The mass was then transferred to reaction vessel with nitrogen blanket. After ensuring an oxygen free atmosphere and temperature of 160°C, 676 kg (15.36 kmole) of ethylene oxide was added to the reaction vessel. After complete addition of ethylene oxide, batch was kept for reaction for 30 minutes. Batch was then transferred to post-treatment vessel, cooled to 40°C and neutralised with 10.5 kg of acetic acid to obtain 6650 kg of 0.5 mole ethoxylated C12-14 lauryl alcohol.

b. Sulfation and Neutralization of 0.5 mole ethoxylated lauryl (C 17.1 ) alcohol:

6650 kg (30.8 kmole) of 0.5 mole ethoxylated C12-14 lauryl alcohol was continuously feed in the falling film reactor equipped with jacket cooling system. It was reacted with a mixture of 2463 kg of SO₃ gas (30.8 kmole) and 20765 kg of air (720 kmole) at the temperature of 45- 47°C to obtain the sulfated mass. The mole concentration of SO₃ in air was 4.1%.

The sulfated mass was then continuously fed to the vacuumed wiped film neutraliser where it was neutralised with 22% sodium hydroxide aqueous solution. Vacuum of the neutralizer was maintained in the range of 0.925 - 0.945 kg/cm". The pH of the solution was adjusted in the range of 6-7 by adding acid.

The resultant 0.5 mole ethoxylated sodium lauryl sulfate solution contained sodium lauryl sulfate and sodium lauryl ether sulfate in a weight ratio of about 73:27 and the combined or total active ingredient content was 70-72% by weight. The product obtained was homogeneous, flowable and pumpable at 25°C, having dioxane content of 1.9 ppm.

Example 2: 0.3 mole ethoxylated sodium lauryl (C₁₂-14) sulfate

a. Preparation of 0.3 mole ethoxylated lauryl (CI¾.H) alcohol:

8600 kg (44.33 kmole) of C12-14 lauryl alcohol was heated to 160°C in a pre-treatment vessel. After the temperature was achieved, vacuum was applied to pre-treatment vessel for removing the moisture from lauryl alcohol. 10 kg of suitable catalyst was then added and the mass was mixed well at the same temperature. The mass was then transferred to reaction vessel with nitrogen blanket. After ensuring an oxygen free atmosphere and temperature of 160°C, 585 kg (13.3 kmole) of ethylene oxide was added to the reaction vessel. After complete addition of ethylene oxide, batch was kept for reaction for 30 minutes. Batch was then transferred to post-treatment vessel, cooled to 40°C and neutralised with 10.5 kg of acetic acid to obtain 9185 kg of 0.3 mole ethoxylated C12-14 lauryl alcohol.

b. Sulfation and Neutralization of 0.3 mole ethoxylated lauryl (C 17.1 ) alcohol:

9185 kg (44.33 kmole) of 0.3 mole ethoxylated C12-14 lauryl alcohol was continuously feed in the falling film reactor equipped with jacket cooling system. It was reacted with a mixture of 3546 kg of SO₃ gas (44.33 kmole) and 29907 kg of air (1037 kmole) at the temperature of 48-50°C to obtain the sulfated mass. The mole concentration of SO₃ in air used was 4.1%. The sulfated mass was continuously fed to the vacuumed wiped film neutraliser where it was neutralised with 22% sodium hydroxide aqueous solution. Vacuum of the neutralizer was maintained in the range of 0.925 - 0.945 kg/cm". The pH of the solution was adjusted in the range of 6-7 by adding acid.

The resultant 0.3 ethoxylated sodium lauryl sulfate solution contained a mixture sodium lauryl sulfate and sodium lauryl ether sulfate and the combined or total active ingredient content was 70-72% by weight. The product obtained was homogeneous, flowable and pumpable at 25°C, having dioxane content of 0.86 ppm.

Example 3: 0.8 mole ethoxylated sodium lauryl (C12-14) sulfate

a. Preparation of 0.8 mole ethoxylated lauryl (CI¾.H) alcohol:

7700 kg (39.7 kmole) of C_12-14 lauryl alcohol was heated to 160°C in a pre-treatment vessel. After the temperature was achieved, vacuum was applied to pre-treatment vessel for removing the moisture from lauryl alcohol. 10 kg of suitable catalyst was then added and the mass was mixed well at the same temperature. The mass was then transferred to reaction vessel with nitrogen blanket. After ensuring an oxygen free atmosphere and temperature of 160°C, 1397 kg (31.75 kmole) of ethylene oxide was added to the reaction vessel. After complete addition of ethylene oxide, batch was kept for reaction for 30 minutes. Batch was then transferred to post-treatment vessel, cooled to 40°C and neutralised with 10.5 kg of acetic acid to obtain 9097 kg of 0.8 mole ethoxylated C_12-14 lauryl alcohol. b. Sulfation and Neutralization of 0.8 mole ethoxylated lauryl (C 17,14) alcohol:

9097 kg (39.7 kmole) 0.8 mole ethoxylated C_12-14 lauryl alcohol was continuously feed in the falling film reactor equipped with jacket cooling system. It was reacted with a mixture of 3176 kg of SO₃ gas (39.7 kmole) and 26792 kg of air (929 kmole) at the temperature of 48- 50°C to obtain the sulfated mass. The mole concentration of SO₃ in air used was 4.1%.

The sulfated mass was continuously fed to the vacuumed wiped film neutraliser where it was neutralised with 22% sodium hydroxide aqueous solution. Vacuum of the neutralizer was maintained in the range of 0.925 - 0.945 kg/cm". The pH of the solution was adjusted in the range of 6-7 by adding acid.

The resultant 0.8 ethoxylated sodium lauryl sulfate solution contained a mixture sodium lauryl sulfate and sodium lauryl ether sulfate in a weight ratio of about 50:50 and the combined or total active ingredient content was 70-72% by weight. The product obtained was homogeneous, flowable and pumpable at 25°C, having dioxane content of 2.1 ppm. Example 4: 0.5 mole ethoxylated sodium lauryl (Cs-is) sulfate

Same process as explained above was followed. The total active ingredient content was 69- 71% by weight. The product obtained was homogeneous, flowable and pumpable at 25°C, having dioxane content of 2.0 ppm.

Example 5: 0.5 mole ethoxylated sodium lauryl

sulfate

Same process as explained above was followed. The total active ingredient content was 68- 70% by weight. The product obtained was homogeneous, flowable and pumpable at 25°C, having dioxane content of about 1.9 ppm.

Comparative Examples:

Following are the examples, where 0.5 mole, 0.3 mole and 0.8 mole ethoxylated fatty alkyl sulfates were prepared under reaction conditions other than the present invention.

Example 6: Preparation of 0.5 mole ethoxylated sodium lauryl (C_12-14) sulfate using mole concentration of 5% of SO₃ in air.

Example 7: Preparation of 0.5 mole ethoxylated sodium lauryl (C_12-14) sulfate using mole concentration of 3% of SO₃ in air.

Example 8: Preparation of 0.3 mole ethoxylated sodium lauryl (C_12-14) sulfate using sulfation temperature of 55°C

Example 9: Preparation of 0.3 mole ethoxylated sodium lauryl (C_12-14) sulfate using sulfation temperature of 35°C

Example 10: Preparation of 0.8 mole ethoxylated sodium lauryl (C_12-14) sulfate using mole ratio of SO₃ to ethoxylated fatty alcohol of 1 : 1.5

Example 11: Preparation of 0.8 mole ethoxylated sodium lauryl (C_12-14) sulfate using mole ratio of SO₃ to ethoxylated fatty alcohol of 1:0.5 It was seen that the flowability of all the products were hampered and some of them become non-flowable also. The dioxane content of all the products was too high, of about more than 10 ppm. Also, some products were found to be discoloured.

Formulation Examples

Example 12: Shampoo formulation containing 0.5 mole ethoxylated sodium lauryl (C12- 14) sulfate of example 1

After incorporating 14% of the product of example 1 in preparing the shampoo formulation, the dioxane content was detected to be 0.26 ppm based on the total formulation.

Example 13: Shampoo formulation containing 0.3 mole ethoxylated sodium lauryl (C12- 14) sulfate of example 2

After incorporating 14% of the product of example 2 in preparing the shampoo formulation, the dioxane content was detected to be 0.12 ppm based on the total formulation.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The given embodiments are therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

Claims

1. A process for preparing an aqueous solution of fatty alkyl sulfates, wherein said process comprises the steps of

(i) ethoxylating fatty alcohol with about 0.3 to 0.8 moles of ethylene oxide to produce ethoxylated fatty alcohol of formula (I) as per eq.1.

A

R - OH + n H₂C - CH₂ ► R-(OCH₂CH₂)„-OH (eq.l) formula (I)

in which R is a linear saturated hydrocarbon radical containing 8 to 18 carbon atoms, and n is an average number of EO moles between 0.3 to 0.8,

(ii) sulfating the said ethoxylated fatty alcohol with S0₃/air mixture at a temperature from about 40°C to 50°C to produce sulfation product of formula (II) as per eq.2. R-(OCH₂CH₂)„-OH + S0₃ ► R-(OCH₂CH₂)„-OS0₃H (eq.2)

Formula (II)

wherein

mole concentration of S0₃ in S0₃/air mixture is from about 3.5 to 4.5%, and mole ratio of S0₃ to ethoxylated fatty alcohol is from about 1: 1 to 1:1.1,

(iii) neutralizing the sulfation product with an aqueous base as per eq.3.

R-(OCH₂CH₂)„-OS0₃H + MOH ► R-(OCH₂CH₂)„-OS0₃M (eq.3) wherein M is a alkali metal, alkaline earth metal, ammonium or substituted ammonium;

2. The process as claimed in claim 1, further comprising neutralizing the sulfation product under a pressure of 30-100 mmHg.

3. An aqueous solution of fatty alkyl sulfates prepared by the process as claimed in claim 1, the solution comprising

(i) atleast 65% by weight of mixture of fatty alkyl sulfates and fatty alkyl ether sulfates in a weight ratio in the range from about 80:20 to about 50:50 wherein the average number of moles of ethylene oxide (EO) of the mixture is between 0.3 to 0.8, and

(ii) less than 3 ppm of dioxane; and

(iii) water.

4. The fatty alkyl sulfates as prepared by the process as claimed in claim 1, is homogeneous, flowable, and pumpable at and below 25°C.

5. The fatty alkyl sulfate solution of claim 3 does not contain antimicrobial or preservative.