FIELD OF THE INVENTION

[0001] The present technology relates to methods of making dialkyl amino acid ester sulfonates that are the neutralized (protonated) reaction product of an amino acid having at least two carboxylic acid groups and a fatty alcohol. In particular, the present technology relates to methods of making dialkyl amino acid ester sulfonates that provide higher yields of the amino acid diester reaction product and reduced amounts of byproducts, particularly sulfonic acid esters.

BACKGROUND OF THE INVENTION

[0002] There has been a trend in the personal care industry to formulate compositions with ingredients that are based on renewable resources derived from plants or animals, rather than fossil fuels. Such ingredients are considered “green” or “natural”, since they are derived from renewable and/or sustainable sources. As a result, they are more environmentally friendly than ingredients derived from fossil fuels, particularly if they are also manufactured without the need for petroleum-derived solvents. An ingredient having a high Biorenewable Carbon Index (BCI), such as greater than 80, indicates that the ingredient contains carbons that are derived primarily from plant, animal or marine-based sources.

[0003] Published PCT application WO2022/056366, which is herein incorporated by reference, describes dialkyl amino acid ester salts that are derived from renewable sources and can be used in compositions as a cationic component either alone or in combination with a glyceride component. The dialkyl amino acid ester salts provide conditioning, softening, or cleaning performance, and are particularly useful in hair care compositions. The dialkyl amino acid esters salts are the reaction product of an amino acid and a fatty alcohol reacted in the presence of a proton-donating acid. In preferred embodiments, the proton-donating acid is a sulfonic acid derived from biorenewable sources. The PCT application provides methods for producing different dialkyl amino acid ester salts, but does not mention the product distribution of the resulting reaction product. It has now been determined that, in addition to the amino acid diester salt reaction product, the reaction conditions described in the PCT application, which include a reaction temperature of 140 °C, form appreciable amounts (greater than 10 wt%) of by-products, such as amino acid monoester, etherified fatty alcohol, and esters of the proton-donating acid. Removing these by-products involves additional post-reaction procedures, which can lead to reduced product yield due to additional processing, and can increase production costs.

[0004] It would be desirable to have an improved esterification process that can provide comparable or higher yields of total amino acid ester reaction product, and reduced amounts of by-products, compared to methods described in the prior art. It would also be desirable to have an improved esterification process that eliminates the need for additional processing to remove unwanted by-products. Providing an improved process for preparing dialkyl amino acid esters salts, particularly those having a BCI of greater than 80, would satisfy sustainability goals of ensuring sustainable consumption through the use of bio-based materials, and promoting sustainable industrialization by providing a more efficient and cost-effective manufacturing process. SUMMARY OF THE INVENTION

[0005] The present technology relates to an improved method of making dialkyl amino acid ester sulfonate salts that results in an amino acid ester salt reaction product having fewer by-products. In one aspect, the present technology is directed to a method of making a dialkyl amino acid ester sulfonate having an undetectable (less than 500 ppm as determined by ¹ H NMR) amount of sulfonic acid ester by-product. The method includes the steps of forming a reaction mixture comprising (i) an amino acid having at least two carboxylic acid groups; (ii) a fatty alcohol feedstock, wherein the fatty alcohol feedstock comprises one or more linear or branched, saturated or unsaturated fatty alcohols having from 8 to 22 carbon atoms; and (iii) sulfonic acid; and reacting the reaction mixture at a temperature of less than 120 °C for a time sufficient to form a reaction product comprising the dialkyl amino acid ester sulfonate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a graph comparing the wet and dry combing results of hair conditioning compositions prepared with dialkyl amino acid ester ethanylsulfonates prepared according to the present technology vs. compositions prepared with other cationic conditioning agents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] While the present technology will be described in connection with one or more preferred embodiments, it will be understood by those skilled in the art that the technology is not limited to only those particular embodiments. To the contrary, the presently described technology includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims. [0008] “Biorenewable Carbon Index” (BCI) refers to a calculation of the percent carbon derived from a biorenewable resource, and is calculated based on the number of biorenewable carbons divided by the total number of carbons in the entire molecule.

[0009] “Biorenewable” is defined herein as originating from animal, plant, or marine material.

[0010] The present technology provides an improved process for preparing dialkyl amino acid ester sulfonates that are reduced in unwanted by-products, particularly sulfonate ester impurities. In the process, an amino acid having at least two carboxylic acid groups is reacted with a fatty alcohol feedstock and a sulfonic acid at a temperature of less than 120 °C to form the dialkyl amino acid ester sulfonates. The sulfonic acid is used as a quaternization agent in addition to being an esterification catalyst. Sulfonic acids that can be used in the present process include sulfonic acid, methane sulfonic acid, ethane sulfonic acid, higher alkyl analogs of ethane sulfonic acid, such as, but not limited to, propane sulfonic acid and butane sulfonic acid, dodecyl benzene sulfonic acid, and para-toluene sulfonic acid. A preferred sulfonic acid for use in the present technology is ethane sulfonic acid because it can be derived entirely from biorenewable sources. Since the fatty alcohol and amino acid reactants can also be sourced from 100% biorenewable materials, the resulting dialkyl amino acid ester ethanylsulfonates have a BCI of 100. Preferably, the ethane sulfonic acid used in the process of the present technology is free or substantially free of chloride impurities to minimize the formation of alkyl chloride impurities in the dialkyl amino acid ester ethanylsulfonate reaction product. “Substantially free” means the amount of alkyl chloride impurities in the resulting reaction product is below the detection limit of ¹ H NMR (i.e. less than 500 ppm). [0011 ] Amino acids for the formation of the dialkyl amino acid ester sulfonates can be any that have at least two carboxylic acid groups. Particular amino acids include L- aspartic acid and L-glutamic acid.

[0012] Suitable fatty alcohols used in the process may be linear or branched, and may additionally be saturated and/or unsaturated, preferably saturated. The fatty alcohol can contain about 8 to about 22 carbon atoms, preferably 8 to 18 carbon atoms. Specific examples of fatty alcohols that can be used include caprylic alcohol, capric alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, brassica alcohol, or mixtures or combinations thereof. Preferably, the fatty alcohols are derived from non-petrochemical sources. In some embodiments, the fatty alcohol is a mixture of fatty alcohols wherein between 50 wt% and 70 wt% of the alkyl groups in the fatty alcohol have 12 carbon atoms, between 20 wt% and 30 wt% of the alkyl groups have 14 carbon atoms, and between 5 wt% and 15 wt% of the alkyl groups have 16 carbon atoms, based on the total weight of alkyl groups in the fatty alcohol mixture. In some embodiments, the fatty alcohol can be derived from a coconut source, comprising a mixture of fatty acids having carbon chain lengths of 8 to 18 carbon atoms.

[0013] The fatty alcohol, amino acid and sulfonic acid are combined to form a reaction mixture and reacted to form the dialkyl amino acid ester sulfonates. The molar ratio of reactants is 1 molar equivalent of amino acid to 2-4.5 molar equivalents of fatty alcohol to 0.9 to 1.1 molar equivalents of sulfonic acid. No added solvent is necessary for the esterification reaction. The reaction temperature can range from greater than 50 °C to about 110 °C, alternatively about 90 °C to about 105 °C. Surprisingly, employing a reaction temperature of less than 120 °C, with no added solvent, can result in a greater yield of amino acid diester salt and a reduced amount of by-products compared to prior art reaction temperatures of 130-140 °C (Table 1 , infra). The result is surprising because typically higher temperatures and/or solvent are necessary to drive the esterification reaction to completion and provide a higher yield of the desirable reaction product. The components are reacted for a time sufficient to form the dialkyl amino acid ester sulfonate salt. The time for reaction can range from about 4 hours to about 48 hours, alternatively about 5 hours to about 30 hours, alternatively about 6 hours to about 24 hours.

[0014] Optionally, a heterogeneous catalyst can be added to the reaction mixture to reduce the reaction time and/or temperature of the esterification reaction while minimizing by-products. Examples of heterogeneous catalysts include ion-exchange resins, such as Amberchrom®, Amberlyst®, and Nation®, available from DuPont, and heterogeneous acid catalysts, such as sulfated inorganic oxides, including SO4 ² '7ZrO2, SO4 ² 7TiO2, SO4 ² ' /SnO2, and inorganic super acids, including WOs/ZrO2 and WOs/ZrO2-Al2O3. Additional examples of catalysts include titanium-based catalysts, such as those sold by E. I. DuPont de Nemours and Company under the name TYZOR®, for example, titanium t-butoxide (TYZOR®) or ammonium salt of lactic acid chelate of titanium dihydroxide (TYZOR® LA), and tin-based catalysts, such as dioctyltin bis-(2-ethylhexanoate) or dioctyltin dilaurate, available from REAXIS Inc., McDonald, PA.

[0015] When a heterogeneous catalyst is added to the reaction mixture, the reaction time can be shorter than if a catalyst is not employed. For example, the reaction time can be reduced from about 48 hours or about 30 hours or about 24 hours to about 4 hours or about 5 hours or about 6 hours. The catalyst can also allow the reaction to proceed at a lower temperature. For example, reaction temperatures can range from about 50 °C to about 110 °C, alternatively about 50 °C to about 105 °C, alternatively about 55 °C to about 95 °C, alternatively about 55 °C to about 90 °C. The amount of catalyst that can be used is in the range of 10 wt% g/g amino acid to 100 wt% g/g amino acid, such as, for example 50 wt% g/g amino acid.

[0016] The esterification reaction product resulting from the method of the present technology comprises a mixture of compounds, in which at least 45% by weight, such as 45% to about 78% by weight, alternatively 45% to about 76% by weight, is dialkyl amino acid ester sulfonate. The remainder of the mixture is comprised of monoalkyl amino acid sulfonate, unreacted amino acid, fatty alcohol, and sulfonic acid, and dialkyl ether and sulfonic acid ester as by-products. Surprisingly, employing a reaction temperature of less than 120 °C, preferably 105 °C or less, can reduce the formation of sulfonic acid ester and dialkyl ether by-products to levels that are below the detectable limit of ¹ H NMR (i.e. less than 500 ppm). In particular embodiments, using ethane sulfonic acid as the sulfonic acid reactant, the formation of ethanesulfonic acid ester and dialkyl ether by-products are reduced to levels that are below the detectable limit of ¹ H NMR and for the ethanesulfonic acid ester by-product, below the detectable limit by HPLC (i.e. less than 55 ppm). Thus, the process of the present technology can produce a dialkyl amino acid ester ethanylsulfonate product having less than 500 ppm, alternatively less than 400 ppm, alternatively less than 250 ppm, alternatively less than 100 ppm, alternatively less than 55 ppm, and preferably no detectable amounts of ethanesulfonic acid ester and dialkyl ether by-products, as determined by ¹ H NMR and/or HPLC analytical methods described herein. The reaction product mixture can be used without purification or separation of the dialkyl amino acid ester sulfonate. [0017] The dialkyl amino acid ester sulfonates can be formulated into hair care compositions including, but not limited to, hair conditioners and hair repair compositions. The dialkyl amino acid ester sulfonates could also be formulated into other end use products such as, but not limited to, fabric softeners, fabric conditioners, hard surface cleaners, and skin care compositions. Product compositions can include the dialkyl amino acid ester sulfonate in an amount of about 0.01 % to about 50% by weight of the product composition, alternatively about 0.05% to about 25%, alternatively about 0.1 % to about 12%, alternatively about 0.01 % to about 10%, alternatively about 0.1 % to about 5%, alternatively about 0.5% to about 5%, alternatively about 1 % to about 5%, alternatively about 1 % to about 4% by weight of the composition.

[0018] The compositions may contain other optional ingredients suitable for use, such as surfactants or other additives, and a diluent, such as water, depending on the end use for the composition. Examples of surfactants include nonionic, cationic, anionic, and amphoteric surfactants, or combinations thereof. Examples of additives include rheological modifiers, emollients, skin conditioning agents, sun care additives, emulsifier/suspending agents, thickeners, fragrances, colors, pigments, opacifiers, insect repellant actives, herbal extracts, vitamins, builders, enzymes, preservatives, antibacterial agents, pH adjusters, or combinations thereof. Such surfactants and additives are familiar to one skilled in the art, and suitable amounts of these components can be determined by one skilled in the art, depending on end use.

[0019] The method of the present technology provides several benefits. Conducting the esterification reaction at a temperature of less than 120 °C provides comparable or better yields of the dialkyl amino acid ester ethanylsulfonate compared to esterification of the components at higher temperatures, and provides reduced levels of undesirable byproducts. With by-products reduced to undetectable levels, the dialkyl amino acid ester ethanylsulfonates can be used as-is, without further purification steps. The dialkyl amino acid ester ethanylsulfonates prepared by the method of the present technology also have a lighter, more desirable color than those prepared at reaction temperatures of 130-140 °C. Hair conditioning compositions formulated with the dialkyl amino acid ester ethanylsulfonates prepared according to the present technology provide wet hair combing properties comparable to compositions formulated from dialkyl amino acid ester ethanylsulfonates prepared at reaction temperatures of 130-140 °C, and better wet hair combing properties compared to formulations comprising cetrimonium chloride (CETAC), a traditional cationic conditioning agent. However, unlike CETAC, the dialkyl amino acid ester ethanylsulfonates prepared by the present technology provide an improved environmental profile and predicted lower toxicity compared to CETAC.

EXAMPLES

[0020] The presently described technology and its advantages will be better understood by reference to the following examples. These examples are provided to describe specific embodiments of the present technology. By providing these examples, the inventors do not limit the scope and spirit of the present technology.

[0021] The following test methods are used to determine properties and performance of compositions of the present technology. ¹ H NMR was performed on a JEOL 500 MHz spectrophotometer using pyridine-c/5 and trioxane as an internal standard. Chromatographic analysis was performed using an HPLC equipped with a quaternary pump, autosampler, high-efficiency silica-based column and an evaporative light scattering detector (ESLD), where an ethane sulfonic acid ester standard was used to determine limits of detection and quantification. Performance testing was done via the following Dia-Stron procedure.

Dia-Stron Procedure for Wet and Dry Combing

1 . Rinse tress for 30 seconds.

2. Apply 0.5 mL of VO5® Volumizing Shampoo (non-conditioning shampoo).

3. Spread throughout tress.

4. Rinse tress for 30s

5. Allow to air-dry.

6. Rinse tress for 30 seconds.

7. Apply 0.5 mL of Test Conditioner.

8. Spread throughout tress.

9. Rinse tress for 30 seconds.

10. Affix tress to Dia-Stron MTT175 instrument and run “Wet Combing” procedure.

11. Repeat Step 10 nine more times.

12. Repeat Step 1 -10 for 2 more tresses.

13. Allow tresses to air-dry.

14. Affix tress to Dia-Stron MTT175 instrument and run “Dry Combing” procedure.

15. Repeat Step 14 nine more times for one tress.

16. Repeat Steps 14-15 for 2 more tresses.

Example 1 : Synthesis of Dilaurylglutamate EthanylSulfonate (1 :2.1 :1 ratio)

[0022] L-glutamic acid (1 mol, 80.60g) and lauryl alcohol (2.1 mol, 234.70g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1 mol, 85.32g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 90°C and run for 24 hours. During the reaction 8-1 Og samples were taken at 2, 4, and 6 hours for NMR analysis. An additional ~110g sample was taken at 4 hours. After the 24-hour reaction time, the remaining still molten contents of the reactor were transferred to a fared, 1 qt sample jar.

Example 2: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :2.1 :0.9 ratio)

[0023] L-glutamic acid (1 mol, 82.30g) and lauryl alcohol (2.1 mol, 239.65g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (0.9 mol, 82.30g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 90°C and run for 24 hours. During the reaction 8-10g samples were taken at 2, 4, and 6 hours for NMR analysis. An additional ~110g sample was taken at 4 hours. After the 24-hour reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

Example 3: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :2.1 :1.1 ratio)

[0024] L-glutamic acid (1 mol, 78.80g) and lauryl alcohol (2.1 mol, 229.46g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1.1 mol, 91.76g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 90°C and run for 24 hours. During the reaction 8-1 Og samples were taken at 2, 4, and 6 hours for NMR analysis. An additional ~110g sample was taken at 4 hours. After the 24-hour reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

Example 4: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :3:0.9 ratio)

[0025] L-glutamic acid (1 mol, 65.50g) and lauryl alcohol (3 mol, 272.47g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (0.9 mol, 62.40g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 90°C and run for 24 hours. During the reaction 8-10g samples were taken at 2, 4, and 6 hours for NMR analysis. An additional ~110g sample was taken at 4 hours. After the 24-hour reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

Example 5: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :3: 1.1 ratio) [0026] L-glutamic acid (1 mol, 63.30g) and lauryl alcohol (3 mol, 263.32g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1.1 mol, 73.71g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 90°C and run for 24 hours. During the reaction 8-10g samples were taken at 2, 4, and 6 hours for NMR analysis. An additional ~110g sample was taken at 4 hours. After the 24-hour reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

Example 6: Synthesis of Dilaurylglutamate EthanylSulfonate With Catalyst

[0027] L-glutamic acid (1 mol, 30g), lauryl alcohol (2.5 mol, 104g), and Amberchrom® (50 wt% g/g glutamic acid, 15g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1 mol, 30.2g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 90°C and run for 6 hours. After the 6-hour reaction time, the remaining still molten contents of the reactor were vacuum filtered to remove the catalyst and transferred to a tared, 1 qt sample jar. Example 7: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :2.55:1 ratio)

[0028] L-glutamic acid (1 mol, 71.60g) and lauryl alcohol (2.55 mol, 253.17g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was swept over the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1 mol, 75.79g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was heated to 105°C and run for a total of 12 hours. During the reaction samples were taken every 2 hours for NMR to judge reaction completion. After the reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

Example 8: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :4.5:0.9 ratio)

[0029] L-glutamic acid (1 mol, 100g) and lauryl alcohol (4.5 mol, 620.1 g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was swept over the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (0.9 mol, 94.91g) was then charged over a one-minute time period. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was heated to 100°C and run for a total of 24 hours. During the reaction, samples were taken for NMR to judge reaction completion. After the reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar. Example 9: Synthesis of Dilaurylglutamate EthanylSulfonate With Catalyst

[0030] L-glutamic acid (1 mol, 30g), lauryl alcohol (3 mol, 124.8g), and Amberchrom® (50 wt% g/g glutamic acid, 15g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 55°C. Ethanesulfonic acid (0.9 mol, 28.58g) was then charged over a one-minute time period through the nitrogen inlet neck. After the 24-hour reaction time, the remaining still molten contents of the reactor were vacuum filtered to remove the catalyst and transferred to a tared, 1 qt sample jar.

Example 10: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :2.1 :1.1 ratio) (Comparative)

[0031] L-glutamic acid (1 mol, 78.80g) and lauryl alcohol (2.1 mol, 229.46g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1.1 mol, 91.76g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 120°C and run for 6 hours. During the reaction 8-10g samples were taken at 2 and 4 hours for NMR analysis. An additional —110g sample was taken at 4 hours. After the 6-hour reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar. Example 11 : Synthesis of Dilaurylglutamate EthanylSulfonate (1 :2.55:1.1 ratio)

(Comparative)

[0032] L-glutamic acid (1 mol, 70.20g) and lauryl alcohol (2.55 mol, 248.22g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a short-path distillation head attached to a mineral oil filled bubbler. Nitrogen gas was sparged through the mixture as the temperature was brought up to 60-70°C. Ethanesulfonic acid (1.1 mol, 81.74g) was then charged over a one-minute time period through the nitrogen inlet neck. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The reaction mixture was then increased to 120°C and run for 6 hours. During the reaction 8-10g samples were taken at 2, 4, and 6 hours for NMR analysis. An additional ~110g sample was taken at 4 hours. After the 6-hour reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

Example 12: Synthesis of Dilaurylglutamate EthanylSulfonate (1 :3: 1.1 ratio) (Comparative)

[0033] L-glutamic acid (1 mol, 71.78g) and lauryl alcohol (3 mol, 287g) were charged to a 500 mL, 4-necked glass reaction flask equipped with an overhead mechanical stirrer, a thermocouple and heating mantle, and a pressure-equalizing addition funnel. Nitrogen gas was swept over the mixture as the temperature was brought up to 45°C. Ethanesulfonic acid (1.1 mol, 84.9g) was then charged to the addition funnel and was added slowly over the course of one hour. No noticeable exotherm occurred, however the mixture is at first heterogeneous in nature. The addition funnel was then replaced with a short-path distillation head attached to a mineral oil filled bubbler and the reaction mixture was heated to 140°C and run for a total of 26 hours. During the reaction samples were taken hourly for NMR to judge reaction completion. After the reaction time, the remaining still molten contents of the reactor were transferred to a tared, 1 qt sample jar.

[0034] Each of the Example dialkyl amino acid ester ethanylsulfonate reaction products were analyzed by ¹ H NMR. The wt% distribution of components in each reaction product is shown in Table 1 :

Table 1

[0035] As shown in Table 1 , no detectable levels of ethanesulfonic acid ester were found in any of the Example 1 -9 reactions, which had an esterification reaction temperature of 105 °C or less, and only Examples 2, 3, 7, and 8 showed detectable levels of dilauryl ether, which were 0.16 wt% or less. Examples 5 and 12 used the same reactant

¹ not detectable by HPLC (< 55 ppm)

² not detectable by NMR (<500 ppm) ratios, but the reaction temperature of Example 5 was 90°C, whereas the reaction temperature of Example 12 was 140°C. As shown in Table 1 , Example 5 had no detectable levels of ethanesulfonic acid ester or dilauryl ether, whereas Example 12 had 1 .98 wt% and 12.95 wt% of these by-products, respectively. Comparative Examples 10 and 11 , conducted at a reaction temperature of 120 °C, also showed detectable levels of ethanesulfonic acid ester and dilauryl ether.

Example 13: Preparation of Hair Conditioning Compositions

[0036] The dialkyl amino acid ester ethanylsulfonate reaction products prepared In Examples 1 , 2, 4, 5 and 8 were formulated into hair conditioning compositions as the conditioning active. Comparative hair conditioning compositions were also prepared using different cationic conditioning agents, or the comparative dialkyl amino acid ester ethanylsulfonate prepared in Example 12, as the conditioning active. The comparative conditioning agents were behentrimonium chloride (BTAC), centrimonium chloride (CETAC) (AM MO NYX® CETAC-30 from Stepan Company, Northfield, Illinois), STEPANQUAT® Helia (Helia), an esterquat/glyceride conditioning agent prepared from sunflower oil, from Stepan Company, and STEPANQUAT® Soleil (Soleil), an esterquat/glyceride conditioning agent prepared from sunflower oil, from Stepan Company. Each composition was formulated in accordance with the general formulation in Table 2, following the General Procedure below, and contained 2% by weight total conditioning active. Table 2

General Procedure

1. Charge water, begin mixing.

2. Sprinkle in Natrosol™ 250 HHR CS and mix until homogeneous.

3. Adjust pH with 25% Sodium Hydroxide to target of pH 8-9. Mix until clear (30-40 min).

4. Heat to 70-75°C.

5. Add Conditioning component and mix until homogeneous.

6. Add Cetyl Alcohol and mix for 30 min.

7. Cool to 45°C with mixing.

8. In a small beaker dissolve Potassium Chloride in Water. Add to batch.

9. Adjust pH 3.5-4 with 50% Citric Acid.

10. Cool to Room Temp. 11. Add Kathon™ CG.

[0037] Each of the hair conditioning compositions was evaluated for wet combing ability using the Dia-Stron MTT175 instrument and the wet combing procedure. The results of the wet combing testing are shown in Figure 1 .

[0038] The results show that there is no statistical difference in performance between the dialkyl amino acid ester ethanylsulfonates prepared according to the method of the present technology and comparative Example 12. These results demonstrate that the improved process of the present technology does not have a significant effect on the wet combing performance of the resulting dialkyl amino acid ester ethanylsulfonates. The results also show that dialkyl amino acid ester ethanylsulfonates prepared according to the method of the present technology can provide better wet combing properties than CETAC, a commonly used cationic conditioning agent. Unlike CETAC, the dialkyl amino acid ester ethanylsulfonates of the present technology provide an improved environmental profile and predicted lower toxicity compared to CETAC.

[0039] The results show that the BTAC, Helia, and Soleil formulations had lower maximum peak loads and therefore better results than the formulations containing dialkyl amino acid ester ethanylsulfonates. However, the dialkyl amino acid ester ethanylsulfonate formulations still had acceptable Dia-Stron maximum peak loads and were an improvement over CETAC. Moreover, BTAC, Helia, and Soleil have a BCI of 88, whereas the dialkyl amino acid ester ethanylsulfonates have a BCI of 100. The results demonstrate that a conditioning agent sourced from 100% biorenewable materials can provide acceptable conditioning performance. [0040] The present technology is now described in such full, clear and concise terms as to enable a person skilled in the art to which it pertains, to practice the same. It is to be understood that the foregoing describes preferred embodiments of the present technology and that modifications may be made therein without departing from the spirit or scope of the present technology as set forth in the appended claims. Further, the examples are provided to not be exhaustive but illustrative of several embodiments that fall within the scope of the claims.