J9048/C
FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)


PROCESS FOR MANUFACTURE OF DEFI USING HYPOPHOSPHORUS ACID CONTAINING CATALYSTS
HINDUSTAN UNILEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed


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PROCESS FOR MANUFACTURE OF DEFI USING HYPOPHOSPHORUS ACID CONTAINING CATALYSTS
5 FIELD OF THE INVENTION
The present invention relates to preparation of directly esterified fatty acid isethionates (DEFI). Specifically when specific process conditions are followed, use of hydrophosphorous as catalyst has been unexpectedly found to significantly 10 enhance reaction dynamics (e.g., equal to or better than commonly used ZnO catalyst). Further, due to relatively low levels of catalyst used and relatively short reaction times, enhanced reaction is accomplished while avoiding product discoloration.
15
BACKGROUND OF THE INVENTION
Directly esterified fatty acyl isethionate (DEFI) is produced by the direct
esterification of an alcohol of formula:
20 HOR'SO3M
with an organic acid (e.g. fatty acid) of formula:
RCOOH to produce a surface acting agent (i.e., DEFI) of formula:
RCOOR'SO3M 25 where R is a monovalent aliphatic hydrocarbon radical having 7 to 24, preferably 8 to 22 carbon atoms; R' comprises divalent aliphatic hydrocarbon radicals containing 2 to 4 carbons; and M is an alkali metal cation, particularly sodium, potassium or lithium; or an ammonium cation. In the reaction to make DEFI, the alcohol and organic acid noted above are reacted in the presence of a catalyst in 30 order to accelerate and produce commercially viable yields.

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Surface active agents are one of the basic raw materials in the detergent industry. Specifications for such materials generally require the absence of colored impurities in order to prepare high quality, aesthetically pleasant, 5 formulated products such as detergent bars. Absence of colored impurities also minimizes the chances of imparting off-odors to formulated products. Thus, it is obviously desirable to use catalysts which do not cause color impurities when catalyzing the DEFI reaction. It is further desirable to use DEF1 catalysts which provide good reaction rates as well as not leaving undesirable corrosivity toward 10 stainless steel used in DEFI reactors.
A number of catalysts have been used to catalyze DEFI reaction to provide good reaction kinetics with minimum, discoloration. Among some of the catalysts 15 used are included zinc oxide, zinc soap and mixtures (U.S. Patent No. 3,320,292 to Cahn et al.); and mixture of zinc oxide and organic sulfonic acid (U.S. Patent No. 4,405,526 to Lambertr). U.S. Patent No. 6,963,004 to Ahtchi-aii et al. discloses use of zirconium catalysts.
20 None of these references discloses use of hypophosphorous acid is
catalyst.
The use of hypophosphorous acid as catalyst is mentioned in GB 1,059,984, page 6, starting at line 57. However, use of such catalyst was never
25 prevalent because discoloration and/or corrosion issues were associated with use of such. The reference did not appreciate a correlation between long reaction time (6 hours in reference) and discoloration. Also process parameters such as: (1) preference for use of dry isethionate (preferably dispersed as powder, although it may be dissolved and used in aqueous liquid in less preferred
30 embodiment); (2) critical use of low amounts of catalyst (less than 2% by wt,

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preferably 1 % or less, e.g., 0.01 to 1.0%, preferably 0.02 to .50% by wt.) and (3) use of acid, not salt analogs, were not appreciated.
5 BRIEF DESCRIPTION OF THE INVENTION
Unexpectedly, applicants have now discovered that when hypophosphorous acid catalyst is used in a DEFI reaction under specific process conditions (e.g., low amounts of catalyst mixed with preferably dispersed, dry 10 powdered isethionate at four hours or less), the reaction is not only equal to or better than reactions using zirconium compound (e.g., in terms of reaction rate), but there are no corrosion and/or product discoloration issue. This is completely unpredictable.
15 More specifically, the subject invention relates to a process for producing
directly esterified fatty acid isethionate comprising:
(1) first mixing alkali metal isethionate (e.g., preferably dispersed in form
of dry powder dispersed directly in fatty acid or, less preferably,
20 dissolved in aqueous liquid) and hypophosphorous acid catalyst,
typically at room temperature, although temperatures can range from 25 to 95°C; and
(2) subsequently heating reactants to temperature of about 190°C to
25 255°C, typically about 230°C for four hours or less, preferably two
hours or less;
said catalyst being used in an amount from 0.01 to less than 2% by
wt., preferably 0.01 to 1.0%by wt., more preferably 0.2 to 0.5% by
30 wt.

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Only when relatively low amounts of catalyst were used, and the reactants were first mixed and subsequently heated for four hours or less, preferably two hours or less, as noted, were excellent reaction rates (equal to or better than zinc 5 oxide catalyst rate) seen while also having no oxidation or discoloration issues. Dry powder isethionate dispersed in fatty acid was preferred over isethionate dissolved in aqueous liquid (see Figure 4).
These and other aspects, features and advantages will become apparent to
10 those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se.
15 Other than in the experimental examples, or where otherwise indicated, all
numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about". Similarly, all percentages are weight/weight percentages of the total composition unless otherwise indicated. Numerical ranges expressed in the format "from x to y" are
20 understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated. Where the term "comprising" is used in the specification or claims, it is not intended to exclude any terms, steps or features not specifically recited. All temperatures are in degrees
25 Celsius (°C) unless specified otherwise. All measurements are in SI units unless specified otherwise. All documents cited are - in relevant part - incorporated herein by reference.

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BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows percent conversion (molar conversion of sodium 5 isethionate) from sodium isethionate (dry powder was directly dispersed in fatty acid for this example) using H3PO2 (at 0.04%, 0.08%, 0.16% and 0.33% by weight) compared to molar conversion using zinc oxide (0.33% by wt.) catalysts. As seen, conversion is better than equivalent or higher amounts of ZnO.
10 Figure 2 is exactly the same as Figure 1, but removing plots for 0.08% and
0.04% by wt. H3PO2 so comparison between 0.33% by wt. ZnO and 0.33% or 0.16% by wt. H3PO2 can be seen more starkly. Further, as indicated, there are no discoloration issues because reaction occurs in 4 hours or less, preferably 2 hours or less.
15
Figure 3 shows that a high level of H3PO2 (2% and higher) has a detrimental effect on conversion, particularly in combination with long reaction time. Severe discoloration of the reaction material was noted with this example.
20 Figure 4 shows the conversion rates for 0.16% H3PO2 using aqueous
(powder dissolved in water) and dry powdered (powder mixed in fatty acid) isethionate. This figure illustrates that the use of dry powdered isethionate greatly increases the conversion rate at shorter reaction times compared to aqueous solution, although after about 80 minutes, the reaction reaches a plateau.
25
Figure 5 shows conversion when sodium analogs of H3PO2are used. This example demonstrates alternative catalysts of the same family. As seen, typically the analogs are not as good (lower conversion rates) as the acid.

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DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a novel process for preparing DEFI. 5 Specifically, it relates to a novel process for preparing DEFI using
hypophosphorous (H3PO2) acid catalyst, but while avoiding oxidation and/or de¬coloration issues which may be associated with use of such catalysts.
When hypophosphorous catalyst is used in the DEFI reaction according to 10 the process parameters defined by the invention (e.g., using low amounts of
catalyst, preferably using dry isethionate directly dispersed in fatty acid as starting reactant and keeping reaction at 4 hours or less), directly esterified fatty acyl isethionate (DEFI) is produced in good yield (e.g., 80% molar conversion rates equal to or better than rates when using ZnO catalyst) while avoiding oxidation 15 and de-coloration issues noted.
The catalyst accelerates reaction of an isethionate having formula HOR'SO3M (where R' is a divalent aliphatic hydrocarbon radical having 2 to 4 carbons; and M is an alkali metal cation, such as sodium, potassium in lithium; or 20 an ammonium cation) with organic acid (fatty acid) of formula RCOOH (where R is monovalent aliphatic hydrocarbon radical having 7 to 24, preferably 8 to 22 carbon atoms) to produce DEFI of formula:
R COOR'SO3M (R, R' & M defined as above). 25
In the reaction, the molar ratio of fatty acid to isethionate may range from 1:1 to 2:1, preferably 1.2:1 to 1.5:1 and, as explained in greater detail below, when heated (i.e., subsequent to mixture of typically low amounts of catalyst and reactants), the reaction is heated to about 190°-255°C, preferably 220° to 240°C. 30 It is most preferred to use dry isethionate dispersed in fatty acid; less preferred to

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use isethionate dissolved as aqueous liquid. Low amounts of catalyst should be used and reaction should be 4 hours or less, preferably 2 hours or less. Further, isethionates are mixed with fatty acid and catalysts (at about 25 to 95°C) before heating to reaction temperature of 190°C and higher range. 5
The invention is described in greater detail below.
The invention involves mixing alkali metal isethionate, preferably as dry powder dispersed directly into fatty acid resulting in a slurry (although the 10 isethionate may also be dissolved in aqueous liquid) and hypophosphorous (H3PO2) acid at about 25°-95°C prior to heating to 190° to 255°C range.
The alkali metal isethionate, as noted, is most preferably in the form of a dry powder which can be dispersed in fatty acid or, slightly less preferred, which 15 can be dissolved in aqueous liquid.
When isethionate, fatty acid and catalyst are first combined (with or without agitation), this is done at temperature 25 to 95°C.
20 It is a critical part of the invention that the catalyst and isethionate (e.g.,
dispersed powder in fatty acid or dissolved in water and added separately with catalyst and fatty acid) be mixed together before higher temperature range heating. While not wishing to be bound by theory, it is believed that keeping temperature lower at first relative to reaction temperature, allow the catalyst to
25 perform optimally. Applicants have found, for example, that if catalyst and
dispersed isethionate powder are mildly heated (e.g., 30° to 95°C), before further heating to reaction temperature (Example 1), the results are good. When aqueous isethionate is used, conversion rate is slower than if powder in fatty acid slurry is used (see Figure 4).

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Thus, as noted, the invention is directed to catalyst mixed at about 25 to 95°C with preferably isethionate powder dispersed in fatty acid, and then the three are heated to reaction temperature. The reaction temperature is a temperature of 5 about 230° (190-255°C) and reaction is conducted with or without stirring or agitation. The reaction may take from about 20 minutes to about 2 hours although, typically, it will last for about 1 to 2 hours.

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5 HYAMINE TITRATION PROTOCOL
Sample is dissolved/dispersed in water in a volumetric flask, at. 1.5-2.0 grams sample (weighed to 0.0001 g) per liter. The concentration can be increased if the sample activity is very low. In adjusting the volume in the flask, a few drops 10 of alcohol can be used to break foam if it forms at the top of the flask.
10 ml. of the sample solution is pipetted into a stoppered 100 ml. graduated cylinder. 5 ml. of 3A alcohol, 15 ml. of chloroform, and 25 ml. of methylene blue indicator solution are added.
15
The graduated cylinder is stoppered and shaken thoroughly, then allowed to stand and phase-separate. If no active is present the lower organic layer will be colorless. Any active present will complex with the methylene blue indicator and dissolve in the organic layer, coloring it blue.
20
The sample is titrated with a 0.005 M solution of Hyamine 1622 from a 25 ml. buret. After each addition of titrant the graduate is stoppered and shaken thoroughly, then allowed to phase separate. The Hyamine binds with the active, gradually releasing the methylene blue indicator which migrates to the aqueous
25 phase. The end point is taken as the point at which the intensity of blue color in the aqueous and organic phases is equal by visual observation.
An initial titration can be performed with 1 ml. increments of Hyamine solution to get a rough approximation of the end point, followed by a more precise 30 titration.

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The calculation for % active is as follows: 5 % active = V x Mmb x G x 100
W
Where: 10 V = Volume in ml of Hyamine solution required to titrate sample.
Mmb = Effective molarity of Hyamine solution.
G = Milliequivalent weight of the anionic surfactant being analyzed. W = Weight, in grams of the sample being titrated in the 10 ml aliquoit.
15

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EXAMPLE 1
Hypophosphorus acid catalyst (in different amounts) and zinc oxide were 5 tested, using same test, to percent conversion and results set forth in Table below.

Time (min) % conversion
products w/0.33%
ZnO % conversion
products w/0.33%
H3PO2 % conversion
products w/
0.16%H3PO2
0
10 9.55 58.72 27.14
20 20.25 72.93 62.51
30 34.40 75.59 67.93
40 51.09 74.84 71.18
50 62.68 75.12 74.18
60 70.03 76.32 75.35

As seen from the Table and from Figure 1, the reaction dynamics are far 10 quicker using hypophosphorous acid versus ZnO on an equal weight basis. That is, at 20 minutes, H3PO2 catalyst have reached almost full conversion, while this does not happen for ZnO (zinc oxide) until about 40 minutes.
In the case of the H3PO2 conversions, dry isethionate dispersed in fatty 15 acid was used as starting reactant, the noted amounts of catalyst were used and the full reaction was completed in about 1 hour. There was no discoloration observed.

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Figure 2 is exactly the same as Figure 1 but plots for 0.08% and 0.04% by wt. H3PO2 were removed to see more clearly.
Figure 3 is plot of 2.0% by wt. H3PO2 and aqueous isethionate (isethionate 5 dissolved in water). Here it can be seen that conversion rates at 60 minutes are much lower (about 60 compared to 76 or 75 at same time point when dry powdered isethionate slurry is used). Further conversion slows even further as time passes. The Figure shows the advantage of dry powdered isethionate slurry versus aqueous. It also shows detrimental effect of high amounts versus lower of 10 H3PO2.

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EXAMPLE 2
5 Corrosion screening
An 18-8 SS washer was placed in the reaction vessel and weight change was measured. Since no appreciate weight loss occurred in the first H3PO2 reaction, the same washer was used for both experiments. No discoloration or 10 change in the appearance of the washer was noted.

Weight loss (g)
Initial wt. (g) 5.9159 -
After 4 hrs. w/ 0.33% H3PO2 5.9158 0.0001
After additional 4 hrs. w/ 0.16% H3PO2 5.9158 0.0001
After additional 4 hrs. w/ 0.08% H3PO2 5.9156 0.0003
After additional 4 hrs. w/ 0.08% H3PO2 5.9152 0.0007


The experiment shows that hypophosphorous acid catalyst used according 15 to invention (e.g., in terms of amounts used) presents no discoloration issue.
Additionally, visual examination of the washer showed no discoloration or change in appearance, further indicating that hypophosphorous acid catalyst used according to the invention presents no corrosion issue.

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EXAMPLE 3
To further show the criticality of using isethionate powder (dry dispersed 5 isethionate slurry) versus aqueous isethionate solution, applicants conducted DEFI reaction using 0.16% H3PO2 catalyst wherein the starting isethionate was powder dissolved in aqueous solution. As seen from Figure 4, the catalyst dynamics were much more powerful when using dry isethionate dispersed in slurry versus dissolved in aqueous solution. 10
EXAMPLE 4
15 To show that conversion is better using the acid rather than salt analogs,
applicants ran experiments with salt analogs. As seen in Figure 5, and the % conversion (highest 40% for all analogs tested), the analogs simply do not work as well as the acid.
20

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CLAIMS:
5 1. A process for producing directly esterified fatty acid isethionafe comprising:
(a) mixing alkali metal isethionate, fatty acid, and
hypophosphorus acid catalyst at temperature of 25° to 95°C
for 4 hours or less; and
(b) subsequently heating reactants to temperature of 190°C to
10 255°C,
wherein said hypophosphorus acid catalyst is used in an amount from 0.01 to less than 2% by wt.
15 2. A process according to claim 1, wherein alkali metal isethionate is dry
powder dispersed in fatty acid resulting in a slurry which is added directly.
3. A process according to claim 1, wherein isethionate is powder dissolved in
20 aqueous liquids.
4. A process according to claim 1, wherein catalyst is used in an amount 0.01
to 1.0% by wt.
25
5. A process according to claim 4, wherein catalyst is used in an amount 0.02
to 0.5% by wt.

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6. A process according to claim 1, wherein isethionate, fatty acid and catalyst are mixed 2 hours or less.
7. A process according to claim 1, wherein directly esterified fatty acid isethionate made shows no discoloration.
Dated this 9th dayof September 2008
HINDUSTAN UNILEVER LIMITED

(Anand Shetty) Principal Research Associate