WO2007038025A2

WO2007038025A2 - High purity polyol monoester compositions and methods for producing the same

Info

Publication number: WO2007038025A2
Application number: PCT/US2006/036079
Authority: WO
Inventors: Anatoliy Dameshek; Christopher A. Gariepy; Joseph C. Rongione; Richard R. Tenore
Original assignee: Stepan Company
Priority date: 2005-09-23
Filing date: 2006-09-23
Publication date: 2007-04-05
Also published as: WO2007038025A3

Abstract

The present technology generally relates to high purity polyol monoesters, and improved processes for producing high purity monoesters of a polyol and a fatty acid or fatty acid derivative by adding the fatty acid or fatty acid derivative to a preheated polyol at a desired rate and at an appropriate reaction temperature. The present technology also generally relates to liquid cleansing compositions comprising a high purity propylene glycol monoester, where such compositions preferably comprise a propylene glycol ester having at least about 80% by weight monoester content based on the total weight of the propylene glycol ester.

Description

HIGH PURITY POLYOL MONOESTER COMPOSITIONS AND METHODS FOR

PRODUCING THE SAME

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 60/720,305, filed on September 23, 2005.

FIELD OF INVENTION

[0002] The present technology generally relates to high purity polyol monoesters, and improved processes for producing high purity monoesters of a polyol and a fatty acid or fatty acid derivative by adding the fatty acid or fatty acid derivative to a preheated polyol at a desired rate and at an appropriate reaction temperature. The present technology also generally relates to liquid cleansing compositions comprising a high purity propylene glycol monoester.

BACKGROUND OF THE INVENTION

[0003] It is known in the art that some fatty acid esters of polyols are excellent oil-in-water emulsifϊers for food products, drug delivery vehicles, cosmetic ointments and the like, and are also useful as detergent surfactants and can be combined with co-surfactants, builders and detergent adjunct materials. Fatty acid monoesters of polyols can also be used as coalescence aids in latex paints, and as pigment dispersants for cosmetics, paints and ore slurries. See, e.g., U.S. Published Patent App. No. 2003/0187103 Al (Bloom et al.).

[0004] In general, the preparation of fatty acid esters of polyols may be accomplished from a number of routes. For example, propylene glycol and triglycerides can be reacted together to provide a reaction product comprising monoesters of propylene glycol, propylene glycol diesters, monoglycerides, diglycerides, and triglycerides, after removal of the excess propylene glycol and glycerol. A second preparation route involves the reaction of propylene glycol with fatty acids or fatty acid derivatives, such as methyl or ethyl esters of fatty acids. The product from this reaction will generally be a mixture comprising primarily mono- and diesters of propylene glycol after the removal of water or the low-boiling alcohol (ethanol, methanol, etc.), by-products and any excess starting reactants. A third route is to react propylene oxide with fatty acid, leading to a mixture of mono- and diesters or a mixture of monoester and free fatty acid, depending on reaction conditions. A fourth route would be to react propylene glycol with an acid chloride of a fatty acid, the outcome of which is similar to those previously described.

[0005] All of the techniques of the prior art, when a fatty alkyl substrate is reacted with a polyol or polyhydroxy compound, suffer from the disadvantage of producing mixtures of mono- and diesters with limited ability to enhance the desired monoester content without subsequent processing, i.e. distillation or extraction processes. Alternative processes to avoid formation of the undesirable diester found in the prior art rely on manipulation of the reaction conditions which result in undesirable equilibrium products that contain large quantities of unreacted starting materials and need subsequent processing, i.e., distillation or extraction. This is especially true of the commonly used polyols, propylene glycol and glycerin, the monoesters of which are desirable for emulsifiers used in foods, drugs, cosmetics and industrial cleansers and lubricants.

[0006] The difficulty of obtaining high monoester content in esters of polyols has been known in the art for many years. As an example, U.S. Patent No. 2,383,531 (Arrowsmith & Ross, the '"531 patent") describes in detail the specifics of the difficulties and a typical distillation process to obtain the desired end product. As is typical in the prior art, the process of the '531 patent suffers from the disadvantage of using high levels of free glycerin to drive the equilibrium end product to the desired high monoester content, quenching the catalyst system and running a subsequent purification process.

[0007] Commercially, a polyol monoester such as a propylene glycol monoester can be prepared by either directly esterifying a polyol (e.g., propylene glycol) with a fatty acid or by interesterifying triglyceride with the polyol. For example, direct esterification under practical conditions can be accomplished by reacting propylene glycol with a fatty acid to yield approximately 55 to 60 percent purity of a propylene glycol monoester product; the balance is a reaction by-product comprising diester and unreacted starting material.

[0008] Another commonly utilized process of making propylene glycol monoesters is through interesterificaton of triglycerides with propylene glycol. This interesterifϊcation reaction proceeds at temperatures ranging from about 175° C to about 230° C with the use of a catalyst such as sodium hydroxide. The resulting crude product contains propylene glycol mono- and diesters, monoglycerides and diglycerides, as well as numerous by-products. The final product composition of these processes can be described in terms of the ratio of mono- to diesters comprising the crude product. The composition of the end product can be controlled by varying the amounts of polyol with respect to triglyceride, and through manipulation of the reaction conditions. A higher concentration of monoesters is usually obtained through a molecular distillation process.

[0009] In many instances, it is preferable to utilize a monoester mixture, which possesses a high ratio of monoester to diester. For example, U.S. Pat. No. 6,436,430 (Mulye) describes, in general, the use of a propylene glycol monoester of C₆-C₁₈ fatty acid having at least 60% by weight monoester content based on the total weight of the propylene glycol ester and a non-ionic surfactant to provide a self-emulsifying composition for drugs poorly soluble in water. A typical commercial operation utilizes a high ratio of propylene glycol to triglyceride to yield a product possessing a high monoester content, usually 65% to 75% mono-ester.

[0010] Monoglycerides are mono-fatty acid ester derivatives of glycerol. In general, crude monoglyceride mixtures are made from reacting naturally occurring triglycerides, often obtained from oil seed processing, with glycerol. The process is known as glycerolysis. Such reactions generate a mixture of monoglycerides, diglycerides and triglycerides. Limitation on monoglyceride production, via this approach, is generally controlled by: (1) solubility of the glycerol in the reaction mixture; (2) the overall equilibria statistics; and, (3) time. Typical commercially available crude monoglyceride mixtures made using this approach include ratios of monoglyceride:diglyceride:triglyceride (by weight) of about 45:45:10; or about 60:35:5, depending on processing conditions utilized.

[0011] Commercial production of monoglycerides and monoesters of polyols have been extensively reviewed in Bailey's Industrial Oil & Fat Products, vol. 4, published by John Wiley & Sons (5th edition, 1996) (hereinafter "Bailey's"). In general, Bailey's teaches one skilled in the art, who wants to optimize the production of monoesters of polyols to employ a mass molar excess of the polyol component, to achieve the desired outcome at equilibrium. Typically, the reaction conditions employ from about 40% to about 60% by weight of the polyol component, a level which is disadvantageous to process economics. Bailey's provides a table of reaction ratios and equilibrium outcomes to use as a guide for predicting process equilibrium of the reactions described therein.

[0012] In addition, because the equilibrium stage of the reaction produces a mixture of components, multiple secondary steps normally are employed to obtain the desired end product composition, including vacuum stripping, washing, deodorization, and/or distillation. Therefore, the crude monoester mixtures are typically purified for at least partial isolation of the monoesters from the diesters. Distillation or extraction of the crude monoester mixture produces purified monoester compositions (see, ejj., U.S. Patent Nos. 3,669,848 (Selden) and 6,153,773 (Kolstad et al.)). In general, a distillation process is the most widely used technique for such purification. Typically, the crude monoester mixture is distilled under vacuum, in a short path distillation process. The distillate generally comprises greater than 90% (by weight) monoesters. The remaining material generally comprises mainly diesters. However, each of these subsequent steps incurs additional yield loss, process time, capital equipment; all of which impact negatively on process economics.

[0013] For example, in many instances, it is preferred to utilize more purified monoglycerides. That is, crude monoglyceride compositions or mixtures are purified for at least partial isolation of the monoglycerides from the diglycerides and triglycerides. In general, monoglyceride distillation has been the most widely utilized technique for such purifications. Typically the crude monoglyceride mixture is distilled under vacuum, in a short path distillation process. The distillate generally comprises greater than 90% (by weight) monoglycerides. The remainder generally comprises diglycerides and triglycerides. During the process, the monoglycerides are generally heated to at least 200° C. However, in some instances, such processes which involve distillation of monoesters, for example, monoglycerides or propylene glycol monoesters, are associated with the generation of "off tastes" and/or "off aromas" in the final product. The specific source of these off flavors or off aromas is not presently known. However, it is generally believed to be associated with the utilization of the distillation processes, i.e., processes that concern heating mixtures containing the monoglyceride (or propylene glycol monoester) of interest until they vaporize under the distillation conditions, typically at about 240° C.

[0014] U.S. Patent No. 2,251,693 (Richardson, et al.) (hereinafter the '"693 patent") describes an improvement in yield from the typical monoglyceride content (just above 50% by weight) to levels of just above 80% by weight. The '693 patent identifies commercially available monoglycerides containing about 50% monoglyceride, the desired product, and the remainder of the end product made up of diglycerides and triglycerides. To increase the level of desired monoglyceride, the '693 patent requires the interesterification of a fat (triglyceride oil) and glycerol in a solvated system employing dioxane as the preferred solvent. The ratio of glycerin to oil is on the order of 4:3; i.e. the level of glycerol in the reactor at the start of the reaction exceeds the level of triglyceride oil. The interesterification is run with a typical base catalyst followed by neutralization and stripping of the dioxane solvent. The utility of the reactor in this method is significantly reduced due to the employment of a very large excess of glycerol and the employment of the solvent, both of which must be removed from the end product mixture. The '693 patent further provides that the desired monoglyceride may be isolated by solvent extraction using acidulated water and ethyl ether. The process is not economic, requires extraction of the solvent of reaction, and a second extraction of the product from the fractionation solvent.

[0015] U.S. Patent No. 2,789,119 (Sully) (hereinafter the '"119 patent") identifies the process utilized in the '693 patent as giving erratic results due to the employment of dioxane as a solvent. The '119 patent additionally identified dioxane as toxic and undesirable and suggests the use of tert-butyl alcohol as an ideal solvent for interesterifϊcation reactions. However, the described process of the '119 patent similarly suffers from the reduced utility of the reactor due to incorporation of a reaction solvent, which in turn must be removed by steam distillation. Although the ' 119 patent claims to use more favorable ratios of glycerol to fat — 6 parts glycerol to 10 parts fat — the levels of monoglyceride are in agreement with the equilibrium distributions identified in Bailey's. To achieve levels of monoglyceride in excess of 70% in the end product, the described process requires a second purification step, either molecular distillation or crystallization. Although the '119 patent does offer to recycle the di- and triglyceride byproducts, the described process suffers from the necessity of removing residual catalyst and the associated yield losses from multiple step processing.

[0016] U.S. Patent No. 2,875,221 (Birnbaum) (hereinafter the '"221 patent") describes a continuous process to produce monoglycerides. Although the patent does not suffer the reactor utility loss of processes that use solvents, it does comply with the reactant ratios identified in Bailey's. It therefore loses reactor utility due to the excess glycerol required to shift the equilibrium to the desired end product. Ten percent of the reaction mass is made up of previously formed monoglyceride. This material is necessary to facilitate the solvation of the glycerol and glyceride of a fatty acid. The reaction rate is not sufficient to achieve equilibrium in the reactor phase of the process. This process suffers from an inability to achieve equilibrium as exemplified by the holding tank required in the process following the reactor zone. Further, catalytic activity is not well controlled and if compromised, the method of the '221 patent can result in production of an end product low in monoglyceride content.

[0017] Moreover, the process of the '221 patent further provides for the removal of residual catalyst by filtration. Such a process is impractical without the added requirement of water washing to fully remove catalyst salts and residual glycerol. Complete removal of glycerol is not demonstrated in the examples provided and will require a subsequent processing step. Thus, the process described in the '221 patent lacks the necessary throughput to achieve economic success and true high monoglycerol ester content, 80% and higher. Rather, the described process requires the added step of molecular distillation, a further processing economic inefficiency.

[0018] U.S. Patent No. 3,079,412 (Chang et al.) (hereinafter the '"412 patent") describes a counter current, continuous process to produce monoesters of polyol compounds. Although the '412 patent claims that process economics are not affected by the large excess of glycerin being delivered to the reaction zone, the described process does not account for the glycerin content of the equilibrium mixture obtained from the product side of the reactor. According to the process of the '412 patent, a small portion of glycerin is being added with catalyst as a mixture to the reactor, and the mixture flows in a counter current direction to a homogenized mixture of fat (triglyceride) and excess glycerol. At the same time, a quantity of glycerol equivalent to that being added with the catalyst is being discharged at a position opposite to the product removal side of the reactor zone. However, the excess glycerol homogenized with the starting fat and having reached an equilibrium reaction mixture is still discharged as part of the product. The process of the '412 patent requires glycerin levels in line with the ratios set out in Bailey's, the equilibrium product mixture is also in line with the anticipated outcome in Bailey's resulting in a product with a maximum 70% by weight monoglyceride and 5-8% by weight free glycerol. Although not described by the '412 patent, the final product requires a subsequent purification step to remove excess glycerol and enhance monoester content. Additionally the '412 patent describes neutralization of the final equilibrium product by continually pumping the finished equilibrium mass through an ion exchange resin. Such a process is impractical because there is no indication of a system for regeneration of the resin after catalyst is deposited on the resin. The process as described suffers from the inherent loss of economic efficiency due to the requirement of excess glycerol and additional equipment and processing steps to obtain the final product.

[0019] U.S. Patent No. 3,313,834 (Allen et al.) (hereinafter the '"834 patent") discloses a process for making monoesters by removing a fraction of the equilibrium mixture continually, with make up of the reactants, and by passing the portion removed through a molecular still, to remove the unreacted polyol component. The '834 patent provides for the rapid removal of the polyol component, with rapid cooling followed by neutralization of the catalyst. The described process inherently suffers from the flaw that the rate of interesterification under catalytic conditions is very rapid and competitive with the rate of removal of the polyol component even under conditions of shot path distillation; i.e., as the polyol component is removed it is regenerated at the expense of monoester to diester formation. The process description in the '834 patent does not affect the equilibrium product distribution as described in Bailey's and as a consequence targets the typical 50% by weight monoester mixture with di- and tri-esters. The described process also suffers from the necessity to filter undesired catalyst residues from the end product.

[0020] U.S. Patent No. 4,363,763 (Peterson) (hereinafter the '763 patent) provides for the manufacture of polyol monoesters of alpha-hydroxy carboxylic acids and utilization of those monoesters in emulsions and detergent compositions. The '763 patent describes polyol esters of hydroxy fatty acids that are targeted to deliver α-hydroxy acids to the skin. The '763 patent describes a complex method of making the ester to obtain high mono content, followed by an elaborate extraction to obtain the desired end product. The process of the '763 patent is laborious, requires several steps including processing and clean up, is generally a cost prohibitive process, and generates significant amounts of by-product waste. Indeed, the costly process of the '763 patent is not suitable for producing low priced emulsiflers intended to provide emulsification.

[0021] U.S. Patent No. 6,723,863 (Lee et al.) (hereinafter the "'863 patent") discloses a process of producing a high monoester mixture from a polyol and a triglyceride oil which eliminates the use of organic solvents, multiple water washings and/or molecular distillation. The '863 patent provides that in the presence of a catalyst at a temperature range from about 180° C to about 280° C under an inert atmosphere or under the vapor pressure of the polyol with a pressure up to about 500 psig at reaction temperature, a polyol can interesterify with an oil to yield a monoester mixture possessing a desirable monoester composition containing a high amount (approximately 90% by weight) of monoester and color. However, the process of the '863 patent requires a relatively high temperature (typically at 240° C) for the esterfication of polyol, which can adversely affect the flavors and aromas of the monoester product.

[0022] It would be useful to develop a process for producing monoesters from polyols and fatty acids or fatty acid derivatives at a lower temperature in which the product of the process contains a high amount of monoester and desirable characteristics without the need for purification through a distillation or extraction process. It has been surprisingly found that the improved process of the presently described technology yields a monoester mixture comprised of about 80% by weight or more monoester content, and possesses an acceptable color, flavor, and odor achieved through an esterfication reaction carried out under an appropriate reaction temperature. The process of the present technology can decrease the cost to produce monoesters of polyols by decreasing process waste streams and by delivering higher purity monoesters by maintaining a single reaction phase over the course of the reaction at an appropriate temperature, minimizing the formation of undesired diester and higher (e.g., triester) components in the end product(s).

[0023] Anionic surfactants such as ammonium lauryl sulfate (ALS) or ammonium laureth sulfate (ALES) are known in the art to be used in personal care liquid cleansing systems. In order to obtain thickening with these types of systems, it is necessary to add a thickener. Suitable thickeners include polymers such as cellulose polymers (e.g., hydroxy ethyl cellulose) and polyethylene glycol polymers (e.g., PEG 150 Distearate, PEG 120 Methyl Glucose Dioleate) and salts such as sodium chloride and ammonium chloride. A need also exists for liquid cleansing compositions based upon non-polymeric salt free surfactant systems that have desirable levels of thickening, foam quality and integrity, fragrance solubilization, and clarity. It has also been surprisingly found that a propylene glycol monoester having at least about 80% by weight monoester content based on the total weight of the propylene glycol ester displays unique properties when used in liquid cleansing applications including thickening, foam quality and integrity, clarity, fragrance solubilizing, and conditioning.

BRIEF SUMMARY OF THE INVENTION

[0024] It is one objective of the presently described technology to improve process economics for manufacturing monoesters of polyols and fatty acids by judiciously combining reactants in such a way that promotes solution chemistry while avoiding or minimizing the possibility of forming a two-phase system.

[0025] It is a further objective of the presently described technology to keep polyol concentration low or to an absolute minimum, and to avoid or reduce the use of solvents to promote solubility, and therefore, to maximize the utility of a process reactor for the production of monoesters described herein.

[0026] It is yet another objective of the presently described technology to find a suitable additive that can be used both as thickening and conditioning agents for personal care liquid cleansing products and that can be utilized as a substitute for other additives, for example, sodium chloride and silicone.

[0027] In one aspect of the presently disclosed technology, it has been surprisingly found that by carrying out the reaction in a solution phase, monoester content is favored to diester content of a polyol reacted with fatty acid derivatives.

[0028] In some embodiments, the presently disclosed technology provides processes to improve the production of a high purity monoester of a polyol and a fatty acid or a fatty acid derivative. For example, methods are provided to manufacture a high purity monoester of a polyol and a fatty acid or fatty acid derivative by adding a fatty acid or fatty acid derivative to a preheated polyol, preferably at such a rate as to prevent or substantially reduce the formation of a second liquid phase, at an appropriate reaction temperature. Methods method of these embodiments can include the following steps: a) providing a polyol; b) heating the polyol to within an appropriate reaction temperature range; c) adding a fatty acid or a fatty acid derivative to the heated polyol within the appropriate reaction temperature range to form a reaction solution; and d) holding the reaction solution within the reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed.

[0029] In accordance with methods of the present technology, a reaction catalyst can be added to the preheated polyol at the appropriate reaction temperature before the addition of the fatty acid or fatty acid derivative. For example, the method can include the following steps: a) adding the polyol to a reaction vessel; b) heating the polyol to a reaction temperature; c) adding a catalyst to the heated polyol to form a mixture; d) adding a fatty acid or fatty acid derivative to the mixture to form a reaction solution at a rate sufficiently slow to avoid formation of a two-phase mixture; and e) holding the reaction solution at the reaction temperature until all or substantially all of the fatty acid or fatty acid derivative is consumed.

Sometimes, the catalyst needs to be activated after being added to the heated polyol. For example, when potassium methylate is used as the catalyst, it can be activated by stripping methanol.

[0030] In another embodiment, the presently disclosed technology provides a method to manufacture a high purity monoester of a polyol and a fatty acid or fatty acid derivative, and the method includes the steps of: a) adding a first charge of the polyol; b) heating the polyol to within a first reaction temperature range; c) adding a reaction catalyst to the polyol heated within the first reaction temperature range to form a polyol/catalyst mixture; d) adding the fatty acid or fatty acid derivative to the polyol/catalyst mixture heated within the first reaction temperature range to form a reaction solution; e) mixing and holding the reaction solution within the first reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed; and f) adding a second charge of the polyol to the reaction solution.

[0031] In another embodiment, the presently disclosed technology provides a process to improve the production of a high purity monoester of a polyol and a fatty acid or fatty acid derivative comprising: a) heating a first charge of a polyol to within a first reaction temperature range; b) adding a reaction catalyst to the polyol heated to the first reaction temperature range to form a polyol/catalyst mixture; c) adding a fatty acid or a fatty acid derivative to the polyol/catalyst mixture within the first reaction temperature range to form a reaction solution; d) holding the reaction solution within the first reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed ; and e) adding a second charge of the polyol to the reaction solution.

[0032] One inherent advantage of the presently described technology is the avoidance of a diluting solvent to promote the existence of a single-phase solution. This is achieved through careful addition of the ingredients at a rate sufficient to keep up with the reactivity of the components, but below such a rate as to exceed the miscibility limits of the ingredients. In so doing, it has been surprisingly found that an enhanced ratio of monoester production at the expense of diester and higher components can be achieved.

[0033] The prior art has relied upon significant excess use of polyols to "statistically favor" monoester production followed by subsequent steps to clean up the product and isolate the desired monoester component. The presently described technology significantly increases the monoester content without the need of significant excess use of polyols, and subsequently reduces the effort required to purify the product by isolating the desired monoester product, and in some cases can produce sufficiently clean enough product to substantially eliminate all post reaction processing.

[0034] In another aspect of the presently described technology, it has been surprisingly found that a propylene glycol ester having at least about 80% by weight monoester content based on -lithe total weight of the propylene glycol ester, which can be obtained by either the method of the present technology or by another method currently known or discovered in the future, displays unique properties when used in liquid cleansing applications including thickening, foam quality and integrity, clarity, fragrance solubilizing, and conditioning.

[0035] This aspect of the presently described technology provides one or more embodiments of a liquid cleansing composition comprising a propylene glycol ester having at least about 80% by weight monoester content based on the total weight of the propylene glycol ester; and a surfactant, preferably an anionic or zwitterionic surfactant. More preferably, the surfactant is suitable for use in a personal care product.

[0036] One advantage related to this aspect of the presently described technology is that the propylene glycol esters of the present technology are liquid at room temperature, allowing for processing at room temperature.

[0037] Another advantage related to this aspect of the presently described technology is that the propylene glycol esters of the present technology are biodegradable, since they are derived from, for example, vegetable oils, which are natural, renewable resources.

[0038] A further advantage related to this aspect of the presently described technology is that the present propylene glycol esters provide conditioning at levels comparable to that of silicones that are known in the art. Production costs of the present propylene glycol esters are lower than those of known silicones.

[0039] Yet another advantage related to this aspect of the presently described technology is that when utilizing the propylene glycol esters of the present technology in conjunction with a surfactant in a liquid cleansing system, it is not necessary to include a secondary surfactant.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS [0040] [Not Applicable]

DETAILED DESCRIPTION OF THE INVENTION

[0041] While the presently described 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.

[0042] In general, the first aspect of the presently described technology provides a process to improve the production of a high purity monoester of a polyol and a fatty acid or a fatty acid derivative by preheating the polyol to an appropriate reaction temperature and adding the fatty acid or fatty acid derivative to the polyol (preferably after the addition of a reaction catalyst) at an appropriate reaction temperature and at a rate sufficiently slow that can prevent or substantially reduce the formation of a second liquid phase. For example, one method of the present technology comprises: a) providing a polyol; b) heating the polyol to within an appropriate reaction temperature range; c) adding a fatty acid or a fatty acid derivative to the heated polyol within the appropriate reaction temperature range to form a reaction solution; and d) holding the reaction solution within the reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed.

[0043] The appropriate reaction temperature is generally within the range of from about 60° C to about 200° C, preferably from about 110° C to about 170° C, and most preferably from about 120⁰C to about 155° C.

[0044] The presently described technology takes advantage of the solubility of oils, diglycerides and alkyl esters in polyols to effect faster reaction rates and to minimize the formation of analogous monoester side products that can cause purification difficulties. It also takes advantage of mechanical mechanisms to remove desired product and avoid establishing chemical conditions so as to optimize the desired product.

[0045] hi accordance with at least one embodiment of the presently described technology, the full charge of a polyol is preheated to the desired reaction temperature. A catalyst suitable for esterification of polyols and fatty acids or fatty acid derivatives can be added to the heated polyol before the addition of the fatty acid or fatty acid derivative. Such a catalyst can be activated after being added to the heated polyol. For example, when potassium methylate is used as the catalyst, it can be activated by stripping methanol. Next, the full charge of a fatty acid or a fatty acid derivative is added over a specified period (e.g., from about 1 to about 7 hours). The ratio of total polyol to fatty acid or fatty acid derivative is on the order of about 1:1 on a weight basis and can be varied from about 0.9:1 to about 2:1 depending on the desired outcome. (The higher the weight ratio of polyol, the higher the final equilibrium concentration of monoester in the final product.) The addition rate of the fatty acid or fatty acid derivative is should be such that it is sufficient to keep up with the reactivity of the components. Preferably, the fatty acid or fatty acid derivative is added at a sufficiently slow rate to prevent or substantially reduce the formation of a second liquid phase, i.e., the formation of a second liquid phase is substantially minimized or does not form. In at east one such embodiment, the fatty acid or derivative reaction rate is similar to the addition rate of the fatty acid or derivative. The reaction is judged complete when all or substantially all of the fatty acid or the fatty acid derivative has been consumed as determined by an appropriate analytical method such as gas liquid chromatography ("GLC") or acid base titration. Usually the reaction is judged complete when about 5% or less, preferably about 1% or less of the fatty acid or fatty acid derivative is left in the reaction solution. Hence, it is preferred that the reaction solution be held within the reaction temperature range until 5% or less, preferably 1% or less, of the fatty acid or fatty acid derivative is left within the reaction solution. However, one of ordinary skill in the art will appreciate that the reaction completeness may be varied based upon the desired quantity of fatty acid or fatty acid derivative desired in the reaction solution based upon reaction parameters of the presently described technology utilized.

[0046] In accordance with other embodiments of the presently described technology, the polyol can be divided into two charges. In at least one such embodiment, a process is provided to improve the production of a high purity monoester of a polyol and a fatty acid or fatty acid derivative, where the process comprises: a) heating a first charge of a polyol to within a first reaction temperature range; b) adding a reaction catalyst to the polyol heated to the first reaction temperature range to form a polyol/catalyst mixture; c) adding a fatty acid or a fatty acid derivative to the polyol/catalyst mixture within the first reaction temperature range to form a reaction solution; d) holding the reaction solution within the first reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed ; and e) adding a second charge of the polyol to the reaction solution.

[0047] hi embodiments where the polyol is divided into two charges, an initial charge, preferably in the range of from about 50% to about 100% of the full polyol charge, is heated to a reaction temperature within the desired temperature range, the catalyst is added, and then the full charge of the fatty acid or fatty acid derivative is added in the manner described above, i.e. at a rate sufficient to promote reaction but insufficient to cause formation of two liquid phases in the reaction mass. The initial charge of the polyol is more preferably in the amount of from about 50% to about 75%, most preferably in the amount of about 75% of the full polyol charge. In preferred embodiments, the reaction solution is held within the first reaction temperature range until 5% or less, preferably 1% or less, of the fatty acid or fatty acid derivative is left within the reaction solution before the addition of the second charge of the polyol. The remaining charge of the polyol can thus be added after the first phase of the reaction is judged complete by a determination that all or substantially all of the fatty acid or the fatty acid derivative is consumed (usually about 5% or less, preferably about 1% or less of the fatty acid or fatty acid derivative is left in the reaction solution), as determined by, for example, GLC or acid base titration.

[0048] Dividing the full polyol charge into two stages is not a necessity to achieve a high monoester outcome in the presently described technology but a convenient way of accelerating the rate of reaction. It has been surprisingly found that by adding the polyol in two stages the first half of the reaction proceeds more quickly. The subsequent addition of the remaining polyol charge promotes the enhancement of monoester formation at the expense of diester formed in the first step of the process through an interesteriflcation mechanism. The final equilibrium distribution of products (mono- and diesters) will be an equivalent outcome if 100% of the polyol is charged initially or, for example, if 75% of the polyol is charged initially; the difference is the time needed to achieve the equilibrium. It is preferred that the fatty acid or fatty acid derivative be added at a sufficiently slow rate to prevent or substantially reduce the formation of a second liquid phase. It has been surprisingly discovered that as long as the reactants are added at a rate sufficient to promote reaction but sufficiently slow as to prevent clouding or hazy mixtures, i.e. inhomogeneous two-phase mixtures, the equilibrium distribution of monoester is enhanced when compared to equilibrium mixtures prepared from any process resulting in a two-phase reaction mixture (as in Bailey's).

[0049] The reaction temperature in accordance with the at least one embodiment of the presently described technology can be within the range of from about 100° C to about 200° C, preferably from about 110° C to about 170° C, most preferably from about 135° C to about 155° C. In the instance when the full polyol charge is added initially, the reaction temperature is maintained constant throughout the full addition of the remainder of the reactants. In the instance when a partial polyol charge is initially placed in the reactor and the remaining charge of the polyol is added after the charge of the fatty acid or fatty acid derivative and the completion of the first phase of the reaction, it is only necessary to maintain reaction temperature throughout the charge of the fatty acid or fatty acid derivative. Maintaining the reaction temperature with the appropriate range when charging the fatty acid or fatty acid derivative is critical in order to maximize reaction efficiency, because the addition rate of the fatty acid or fatty acid derivative at this stage is limited by reaction rate - higher temperature, higher the addition rate. The subsequent addition of the second polyol charge can be accomplished at a lower temperature; as long as the reaction mass remains homogeneous. The second reaction temperature range in accordance with this embodiment of the presently technology can be from about 20° C to about 170° C, preferably from about 70° C to about 140° C, most preferably from about 100° C to about 135° C.

[0050] The process of the presently described technology substantially minimizes or avoids the use of significant excesses of polyol in the manufacture of monoester compositions of polyols. Not to be bound by any particular theory, it is believed that as the reaction proceeds in a two-phase system the most likely outcome is the formation of diester or higher (e.g., triester) components. This is supported by the applicants' belief that the reaction mixture is discontinuous, two phase, and the reaction takes place at the interface between the polar and non-polar phases. In the composition of reactants as identified in Bailey's, a two phase mixture is inherent: the polyol being the polar phase and the fatty acid derivative being the non-polar phase. As a consequence of mixing, droplets of one exist in the other and any monoester produced throughout the course of the reaction resides in the boundary between the polar and non-polar phases. The probability of another fatty acid derivative reacting with monoester rather than polyol is enhanced due to physical separation of the polyol phase from the fatty acid derivative phase by the already produced monoester, driving formation of diester and higher components.

[0051] The compositions identified in Bailey's require extraordinary excesses in polyol to greatly increase the size of the interface and promote formation of monoester. Because the presently described technology purposely minimizes or eliminates this interface, the probability of the fatty acid derivative reacting with a free polyol is more random. The statistical outcome is therefore higher in monoester content than the processes identified by the prior art.

[0052] Any catalyst suitable for esterification reaction can be used in the presently described technology. Normally such a catalyst is a strong base, such as alkali or alkaline earth hydroxides. For example, one commonly used catalyst is NaOH. The catalyst can also be an alkali or alkaline earth alkoxide salt of an alkyl group alcohol, i.e., alkyl alcoholates, or alkali or alkaline earth metal amides. Examples of such alkyl alcoholates catalysts include, for example, alcoholates of monohydric alcohols with from about 1 to about 18 carbon atoms of the alkali or alkaline earth metals. Such alkali or alkaline earth metal alcoholates include, but are not limited to, alcoholates of methyl, ethyl, propyl, butyl, tertiary butyl, lauryl, stearyl, oleyl, or benzyl alcohols. Cesium, rubidium, potassium, sodium, calcium, lithium, magnesium or zinc alcoholates are typically utilized, along with mixtures of such alcoholates. Sodium (Na), potassium (K) or calcium (Ca) alkoxide salts of lower alkyl group alcohols (1-4 carbons) are preferred.

[0053] Suitable polyols for the presently described technology include polyol compounds with a molecular weight below about 2300 atomic mass unit (amu) and having two or more hydroxyl groups. Examples of such suitable polyols include, but are not limited to, ethylene glycol, propylene glycol, glycerol, diethylene glycol, dipropylene glycol, diglycerol, triethylene glycol, tripropylene glycol, triglycerol, trimethylene glycol, sorbitol, mannitol, sucrose, dextrose, erythritol, cellulose, poly(ethylene glycol) oligomers, poly(glycerol) oligomers, poly(propylene glycol) oligomers, derivatives thereof, and mixtures thereof.

[0054] Suitable fatty acids or fatty acid derivatives can be derived from any vegetable oils, fish oils, animal oils, transgenically-modified plant oils, and single cell organism sources. Example sources include, but are not limited to, sunflower oil, corn oil, canola oil, castor oil, palm oil, palm kernel oil, coconut oil, safflower oil, linseed oil, soybean oil, rapeseed oil, tallow, lard, poultry, sardine, bunker, menhaden, cottonseed oil, oil from a single cell organism or combinations thereof. The oils for the presently described technology may be saturated (i.e., hydrogenated) or partially saturated. Preferred fatty acid derivatives are lower alkyl esters of fatty acids or oils derived from vegetable, fish, animal, transgenically-modified plant or single cell organism sources. Preferably, the alkyl group of the lower alkyl fatty acid ester is from alkyl alcohols with from about 1 to about 6 carbons, which can be in a linear or branched geometry.

[0055] In a preferred embodiment, the fatty acid or fatty acid derivative is derived from a vegetable oil, and the polyol is, for example, propylene glycol (in any of its optical forms and/or mixtures). More preferably, the oil is selected from the group comprising soybean oil, linseed oil, corn oil, sunflower oil, canola oil, rapeseed oil, safflower oil, hydrogenated (full or partial) derivatives thereof, and combinations thereof.

[0056] Preferred high purity fatty acid polyol monoester products of the presently described technology typically comprising at least about 80%, alternatively at least about 89%, by weight monoester content based on the total weight of polyol ester in the composition. Such high purity polyol monoester product can be used, for example, as emulsifϊers in foods, drugs, and cosmetics. Monoesters of the presently described technology can also be used as coalescence aids in latex paints, as pigment dispersants for cosmetics, paints and ore slurries. They can also be used as thickening and conditioning agents in liquid cleansing products, such as detergents and shampoo or other personal care cleansing product, as described below.

[0057] One category of especially useful fatty acid polyol monoester product is propylene glycol ester containing at least about 80% by weight monoester content based on the total weight of the propylene glycol ester.

[0058] In at least a second aspect, the presently described technology provides a liquid cleansing composition comprising a propylene glycol ester, preferably a vegetable oil derived propylene glycol ester, having at least about 80% by weight monoester content based on the total weight of the propylene glycol ester, and a surfactant.

[0059] Although the fatty acid may be branched, it is preferred that a straight chain fatty acid is utilized. Examples of suitable fatty acids of the presently described technology include, but are not limited to, palmitic acid (C16), stearic acid (C18), oleic acid (C18-1), linoleic acid (Cl 8-2), and linolenic acid (Cl 8-3).

[0060] Any oils described above are appropriate fatty acid sources for preparing monoesters suitable for the liquid cleansing compositions of the present technology. Preferably, the oils are chosen from the group including, but not limited to, sunflower oil, corn oil, safflower oil, soy oil, and mixtures thereof. Most preferably, corn oil, sunflower oil, or a mixture thereof can be used to provide fatty acids or fatty acid derivatives for the preparation of monoesters suitable for the liquid cleansing compositions of the presently described technology.

[0061] In one embodiment of the present technology, the fatty acid compositions of the vegetable oils for use in preparing a propylene glycol monoester comprise from about 0% to about 20% palmitic acid, from about 0% to about 20% stearic acid, from about 10% to about 40% oleic acid, from about 40% to about 80% linoleic acid, and less than about 10% linolenic acid. Preferably, the vegetable oil acid compositions of the vegetable oils for use in preparing the propylene glycol monoester of the present technology comprise from about 5% to about 15% palmitic acid, from about 1% to about 5% stearic acid, from about 10% to about 30% oleic acid, from about 50% to about 80% linoleic acid, and less than about 8% linolenic acid.

[0062] The propylene glycol ester component for the liquid cleansing composition of the presently described technology, as indicated herein and above, is a lipid fatty acid esterified product of propylene glycol containing at least about 80% by weight monoester content based on the total weight of propylene glycol ester, i.e., only one of the hydroxy groups is esterified. In one embodiment, the propylene glycol ester comprises less than about 16% diester, less than about 0.1% propylene glycol, and less than about 1.5% methyl ester.

[0063] The term "ester of propylene glycol containing at least about 80% monoester content by weight" signifies that at least about 80% by weight up to a maximum of about 100% of the esters in the propylene glycol ester mixture is the monoester. Although the propylene glycol ester may contain any amount of monoester above the about 80% level based on the total weight of the propylene glycol ester, including from about 80% to about 100% inclusive, e.g., including at least about 85%, 90%, 95%, 98% or 99% by weight, it is preferred that the propylene glycol ester contains at least about 90% by weight monoester.

[0064] The esters of propylene glycols used in the liquid cleansing composition of the present technology can be produced by the method for preparing high purity fatty acid polyol monoester of the present technology as described above. The propylene glycol esters useful in the cleansing composition of the present technology are also commercially available or can be prepared by other art-recognized techniques, e.g., by reacting a fatty acid source with methanol to produce methyl ester and glycerin, and then reacting the methyl ester of fatty acid with excess propylene glycol to produce the propylene glycol monoester or by direct esterification of propylene glycol with fatty acids. Other methods include the methods for the preparation of propylene glycol fatty acid esters described in U.S. Patent No. 6,723,863 (Lee et al.) issued on April 20, 2004, which is incorporated herein by reference in its entirety.

[0065] Whatever the mode of usage, the liquid cleansing composition of the presently described technology should contain a sufficient amount of propylene glycol ester of the present technology to provide a concentration of from about 0.005% to about 50%, alternatively from about 1% to about 25%, alternatively from about 2% to about 10%, by weight based on the total weight of the liquid cleansing composition. In preferred embodiments, the propylene glycol ester is present in an amount of from about 2% to about 4%, more preferably from about 3% to about 4%, by weight based on the total weight of the cleansing composition.

[0066] The liquid cleansing composition of the present technology preferably contains one or more organic or inorganic surfactants selected from the group consisting of anionic, cationic, nonionic, amphoteric and zwitterionic surfactants, derivatives thereof, or mixtures thereof. These surfactants are described in U.S. Patent No. 3,929,678 (Laughlin et al.) issued Dec. 30, 1975, which is incorporated herein by reference. Useful cationic surfactants also include those described in U.S. Patent No. 4,295,217 (Murphy) issued Mar. 31, 1981, and in U.S. PatentNo. 4,222,905 (Cockrell) issued Sept. 16, 1980, both of which are incorporated herein by reference. The surfactant represents from about 1% to about 50%, preferably from about 2% to about 40%, more preferably from about 3% to about 20%, by weight of the liquid cleansing composition.

[0067] Anionic and zwitterionic surfactants are preferred surfactants for the liquid cleansing composition of the present technology because of their ability to provide foam and remove the particulate soil from skin and hair without inducing dryness or irritation. Liquid cleansing compositions, such as shampoo or body wash, containing the presently described propylene glycol esters, while maintaining excellent greasy/oily soil removal, enhance the organoleptic characteristics of the formulation, i.e. the formulation is more pleasing to use because it spreads evenly on the skin or hair, is not runny or too thin nor pasty or too thick. Anionic surfactants are especially preferred for the liquid cleansing composition of the present technology because it has been surprisingly found that propylene glycol monoesters are excellent non-polymeric thickeners for anionic surfactant systems. Useful anionic surfactants specifically include those described in U.S. Patent No. 3,929,678 (Laughllin et al.) and those described in U.S. Pat. No. 4,199,483 (Jones), which are incorporated herein by reference.

[0068] Examples of preferred detergent systems for personal care cleansers are readily known to those skilled in the art and typically include combinations of anionic surfactants and zwitterionic co-surfactants. U.S. Patent No. 5,705,147 (Shapiro & Tseitlina) incorporated herein by reference provides a detailed description of surfactants used to prepare personal care cleansers. The presently described technology, when incorporated in formulations containing mixtures of the surfactants described in U.S. Patent No. 5,705,147 (Shapiro & Tseitlina), will provide enhancement in organoleptic characteristics of viscosity, flow-ability and foam stability. Briefly, a list of typical surfactants for personal care detergents would include: alkyl and aryl-sulfates and sulfonates, alkly and aryl ether sulfates, derivatives of aliphatic quaternary ammonium compounds known in the art as betaines.

[0069] 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 specific examples, the inventors do not limit the scope and spirit of the present technology. It will be understood by those skilled in the art that the full scope of the presently described technology encompasses the subject matter defined by the claims appending this specification, and any alterations, modifications, or equivalents of those claims. Examples

Example 1. Sequential Addition of Methyl Esters and Propylene Glycol

[0070] Propylene glycol (PG) (35.51 g, 0.467 moles) was heated to 135° C. Sodium methoxide solution (2.82 g, 25% by weight (w/w) solution in methanol, 0.013 moles) was added and the solution was stirred for 20 minutes. Next, methyl esters derived from corn oil (100.04 g, 0.343 moles) were added over 5 hours. The solution was agitated for 1.5 hours at which time a second PG charge (57.90 g, 0.761 moles) was added over 1.5 hours. The temperature is maintained at 135° C, and after 1 additional hour a sample was analyzed by gas chromatography (GC). The monoester/diester ratio was found to be 89: 11 by weight.

Example 2. All Raw Materials Combined Prior to Heating to Reaction Temperature

[0071] Propylene glycol (90.12 g, 1.18 moles) and methyl esters derived from corn oil (100.1Og, 0.343 moles) were combined and dried. Sodium methoxide solution (2.98 g, 30% w/w solution in methanol, 0.16 moles) was added at 34° C. The mix was heated to 135° C over 3 hours and then held at 135° C for 3 hours. Upon cooling a sample was analyzed by GC. The monoester/diester ratio was found to be 85: 15 by weight.

[0072] As is clearly obvious to anyone skilled in the art, Example 2 follows the classical reaction sequence as identified in Bailey's and produces a high monoester content as a consequence of the utility of a mass excess of propylene glycol charge to the reactor. Example 1 on the other hand clearly produces an equilibrium product, which yields a 26% decrease in diester side product with nearly identical charges of reactants through the judicious choice of order of addition.

Example 3. Addition of Methyl Ester to Polyol at Elevated Temperature

[0073] Propylene glycol (PG) (75.19 g, 0.988 moles) was heated to 135° C. Sodium methoxide solution (0.73 g, 25% by weight (w/w) solution in methanol, 0.0034 moles) was added and the solution was stirred for 20 minutes. Next, methyl esters derived from sunflower oil (100.15 g, 0.348 moles) were added over 5 hours. The solution was agitated for 15 hours. Analysis by GC showed the monoester/diester ratio to be 85: 15.

[0074] By running the process following the procedure as outlined in Example 3, an outcome equivalent to Comparative Example 2 is achieved with about a 16% reduction in total charge of polyol. One skilled in the art will realize that following Example 3 will allow for a greater utility of the fixed volume of a reactor kettle, i.e. more finished product will come from the same volume due to the improvement in charge ratio of ingredients and that the amount of free or un-reacted propylene glycol at the end of the process needing removal is significantly less for Example 3 as for Example 2. Improved yield and reduced side products improve process economics.

[0075] The following examples illustrate various properties achieved when liquid cleansing compositions were prepared using ALS/ALES systems with vegetable oil derived propylene glycol monoester (PGME) compounds.

Example 4. A Thickened ALES Cleanser Composition

[0076] A liquid cleansing composition was prepared of the following composition:

[0077] In this example, surfactants were mixed at room temperature (20-25⁰C) with deionized water followed by the addition of PGME and preservative. No additional heating or pH adjustment is required to obtain a clear product with desired viscosity.

[0078] The PGME used in this example was found to have a monoester content of 89%, as determined by GLC with the remainder composed of 9.4% diester and residual starting materials. The resulting cleansing composition was clear, pleasingly viscous and had a pH of 6.8. The viscosity as measured by Brookfield type LV viscometer (Spindle 3 at 30 rotations per minute) was found to be 1380 cps at 25 ⁰C. Evaluations of the foaming potential were determined by the procedure described below:

1. Make up a 0.2% active solution of the material to be evaluated in the 25°C tap water.

2. Introduce 100 grams of the 0.2% solution into a 500 ml graduated cylinder, keeping the foam to a minimum. 3. Add 2 grams of castor oil to the graduated cylinder, and then stopper the cylinder.

4. Place the cylinders of solutions to be tested in the shake foam machine, securing them with the clamps at the rubber stoppers

5. Program the machine to invert the cylinders 10 times.

6. Let the foam settle for 15 seconds, then take a reading of total height, including the base of the 100 ml of solution.

7. After 5 minutes, take a foam reading again as in Step 6.

[0079] Initial foam height was measured at 252 milliliters in a 500 ml graduated cylinder, and remained constant over a five minute period.

Example 5. ALES Cleanser Formulation

A liquid cleansing composition was prepared of the following composition in the manner described in Example 4:

[0080] The PGME used in this example was determined to have a monoester content of 85%, as determined by GLC with the remainder composed of 13.3% diester and residual starting materials. The resulting composition was pleasingly viscous, clear and had a pH of 6.9. The Brookfield viscosity (LV 3@30) of the composition was 860 cps at 25 ⁰C.

[0081] Foam height and stability testing was performed in accordance with the procedure described in Example 4. The initial foam height was 245 milliliters and remained constant over a five minute period. Example 6.

[0082] A liquid cleansing composition was prepared of the following composition in the manner described in Example 4:

[0083] The PGME used in this example was determined to have a monoester content of 88%, as determined by GLC with the remainder composed of 9.0% diester and residual starting materials. The resulting composition was pleasingly viscous, clear and had a pH of 6.6. The Brookfield viscosity (LV 3@30) of the composition was 3980 cps at 25 ⁰C.

[0084] Foam height and stability testing was performed in accordance with the procedure described in Example 4. The initial foam height was 252 and remained constant over a five minute period.

[0085] Formulations prepared in accordance with Examples 4, 5, and 6 needed no additional heating or pH adjustment to obtain clear pleasantly viscous liquid cleansing composition. The use of salt or high molecular weight polymers are not required to increase viscosity of the detergent solutions and the formulations were made without the necessity of heat or high shear mixing to disperse and stabilize the ingredients.

[0086] As is apparent to anyone skilled in the art, the compositions herein described result in cleansing compositions acceptable for personal care cleansing, which exhibit good and unusually stable foaming characteristics and which are surprisingly viscous without the utility of additional thickening agents such as hydroxy ethyl cellulose or the addition of salt. Had high molecular weight polymers, such as hydroxy ethyl cellulose been used to thicken the composition the resulting viscosity would not be pleasing because such polymers tend to produce very elastic rheological characteristics; a tendency to be stringy when poured and difficult to dispense from a bottle or sticky when rubbed in the palm of you hand. Had the presently described examples been thickened by adding salt, the resulting viscosity would not be pleasing because salt hardens ALES solutions forming ridged gels; a tendency to fracture and not spread when poured from a bottle or rubbed through the palms of the hands. Compositions of the presently described technology exhibit neither of these negative rheological characteristics and although they exhibit increased viscosity they pour easily form a bottle and spread easily and evenly through the palm of the hand, they are pleasingly viscous.

[0087] The present technology is now described in such full, clear, concise and exact terms as to enable any 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.

Claims

CLAIMSWhat is claimed is:

1. A process to improve the production of a high purity monoester of a polyol and a fatty acid or a fatty acid derivative comprising:

(a) providing a polyol;

(b) heating the polyol to within an appropriate reaction temperature range;

(c) adding a fatty acid or a fatty acid derivative to the heated polyol within the appropriate reaction temperature range to form a reaction solution; and

(d) holding the reaction solution within the reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed.

2. A process of claim 1, wherein the fatty acid or fatty acid derivative is added at a sufficiently slow rate to prevent or substantially reduce the formation of a second liquid phase.

3. A process of claim 1, wherein a catalyst is added to the heated polyol before the addition of the fatty acid or fatty acid derivative.

4. A process of claim 3, wherein the catalyst is activated after being added to the heated polyol.

5. A process of claim 1, wherein the reaction solution is held within the reaction temperature range until 5% or less of the fatty acid or fatty acid derivative is left within the reaction solution.

6. A process of claim 1, wherein the reaction solution is held within the reaction temperature range until 1% or less of the fatty acid or fatty acid derivative is left within the reaction solution.

7. A process of claim 1, wherein the polyol is a compound with a molecular weight below 2300 amu and having two or more hydroxyl groups.

8. A process of claim 7, wherein the polyol is selected from the group consisting of ethylene glycol, propylene glycol, glycerol, diethylene glycol, dipropylene glycol, diglycerol, triethylene glycol, tripropylene glycol, triglycerol, trimethylene glycol, sorbitol, mannitol, sucrose, dextrose, erythritol, cellulose, poly(ethylene glycol) oligomers, poly(glycerol) oligomers, poly(propylene glycol) oligomers, derivatives thereof, and mixtures thereof.

9. A process of claim 1, wherein the fatty acid or fatty acid derivative is derived from the group consisting of sunflower oil, corn oil, canola oil, castor oil, palm oil, palm kernel oil, coconut oil, safflower oil, linseed oil, soybean oil, rapeseed oil, tallow, lard, poultry, sardine, bunker, menhaden, cottonseed oil, oil from a single cell organism, and combinations thereof.

10. A process of claim 1 , wherein the fatty acid derivative is a lower alkyl ester of a fatty acid or an oil derived from vegetable, animal or single cell organism sources.

11. A process of claim 10, wherein the alkyl group of the lower alkyl ester has about 1 to about 6 carbons.

12. A process of claim 1, wherein the appropriate reaction temperature range is from about 60° C to about 200° C.

13. A process of claim 1, wherein the appropriate reaction temperature range is from about 110° C to about 170° C.

14. A process of claim 1, wherein the appropriate reaction temperature range is from about 12O⁰C to about 155° C.

15. A high purity polyol monoester composition produced by the process of claim 1.

16. A process to improve the production of a high purity monoester of a polyol and a fatty acid or fatty acid derivative comprising:

(a) heating a first charge of a polyol to within a first reaction temperature range;

(b) adding a reaction catalyst to the polyol heated to the first reaction temperature range to form a polyol/catalyst mixture; (c) adding a fatty acid or a fatty acid derivative to the polyol/catalyst mixture within the first reaction temperature range to form a reaction solution;

(d) holding the reaction solution within the first reaction temperature range until all or substantially all of the fatty acid or fatty acid derivative is consumed ; and

(e) adding a second charge of the polyol to the reaction solution.

17. A process of claim 16, wherein the fatty acid or fatty acid derivative is added at a sufficiently slow rate to prevent or substantially reduce the formation of a second liquid phase.

18. A process of claim 16, wherein the reaction solution is held within the first reaction temperature range until 5% or less of the fatty acid or fatty acid derivative is left within the reaction solution before the addition of the second charge of the polyol.

19. A process of claim 16, wherein the reaction solution is held within the first reaction temperature range until 1% or less of the fatty acid or fatty acid derivative is left within the reaction solution before the addition of the second charge of the polyol.

20. A process of claim 16, wherein the polyol is a compound with a molecular weight below 2300 amu and having two or more hydroxyl groups.

21. A process of claim 20, wherein the polyol is selected from the group consisting of ethylene glycol, propylene glycol, glycerol, diethylene glycol, dipropylene glycol, diglycerol, trimethylene glycol, Methylene glycol, tripropylene glycol, triglycerol, sorbitol, mannitol, sucrose, dextrose, erythritol, cellulose, poly(ethylene glycol) oligomers, poly(glycerol) oligomers, poly(propylene glycol) oligomers, derivatives thereof, and mixtures thereof.

22. A process of claim 16, wherein the preferred fatty acid or fatty acid derivative is derived from the group consisting of sunflower oil, corn oil, canola oil, castor oil, palm oil, palm kernel oil, coconut oil, safflower oil, linseed oil, soybean oil, rapeseed oil, tallow, lard, poultry, sardine, bunker, menhaden, cottonseed oil, oil from a single cell organism, and combinations thereof.

23. A process of claim 16, wherein the fatty acid derivative is a lower alkyl ester of a fatty acid or an oil derived from vegetable, animal or single cell organism sources.

24. A process of claim 16, wherein the first reaction temperature range is from about 100° C to about 200° C.

25. A process of claim 16, wherein the first temperature range is from about 110° C to about 170⁰ C.

26. A process of claim 16, wherein the first reaction temperature range is from 135° C to about 155° C.

27. A process of claim 16, wherein the second charge of the polyol is added at a temperature within a lower second reaction temperature range, wherein the second reaction temperature range is from about 20° C to about 170° C.

28. A process of claim 27, wherein the second reaction temperature range is from about 70° C to about 140° C.

29. A process of claim 27, wherein second reaction temperature range is from about 100° C to about 135° C.

30. A high purity polyol monoester composition produced by the process of claim 16.

31. A high purity polyol monoester composition of claim 30, comprising at least about 80% by weight monoester content based on the total weight of polyol ester in the composition.

32. A liquid cleansing composition comprising: a propylene glycol ester having at least about 80% by weight monoester content based on the total weight of the propylene glycol ester; and an anionic or zwitterionic surfactant.

33. A liquid cleansing composition of claim 32, wherein the propylene glycol ester is derived from an oil selected from the group consisting of sunflower oil, corn oil, canola oil, castor oil, palm oil, palm kernel oil, coconut oil, safflower oil, linseed oil, soybean oil, rapeseed oil, tallow, lard, poultry, sardine, bunker, menhaden, cottonseed oil, oil from a single cell organism, and combinations thereof.

34. A liquid cleansing composition of claim 32, wherein the propylene glycol ester is present in an amount of from about 2% to about 4% by weight based on the total weight of the cleansing composition.

35. A liquid cleansing composition of claim 32, wherein the propylene glycol monoester compound is present in an amount of from about 3% to about 4% by weight based on the total weight of the cleansing composition.

36. A liquid cleansing composition of claim 32, wherein the propylene glycol ester comprises less than about 16% diester, less than about 0.1% propylene glycol, and less than about 1.5% methyl ester.