Woolgrease

Details Woolgrease Woolgrease

1999-07-16

2002-07-16

Carr, Deborah D. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

C554S156000, C554S201000

Reexamination Certificate

active

06420578

ABSTRACT:

This invention relates to a process for recovering 18-methyl eicosanoic acid (18-MEA) and/or alpha hydroxy acids from woolwax acids or derivatives thereof. These materials can be employed as active ingredients in personal care products.
By “alpha hydroxy acids”, we mean acids of the formula:
where R can be CH
3
or H and n is in the range 10 to 22.
The formula of 18-MEA is:
Woolwax is the preferred name for the fat or grease found in the wool of sheep,
Ovis aries.
In its virgin unrefined state it is one of the best preventatives for rust, but generally woolwax is refined by chemical processing into commercially useful materials in one of two ways. Firstly, it is purified by a refining procedure to give Lanolin. Lanolin is the refined version of woolwax and is used primarily in a hydrated version as an emollient to soothe, smooth and calm dry or damaged skin. Secondly, the woolwax can be saponified to provide separate alcohol and acid fractions. The alcohol fraction is a complex mixture of sterols and fatty alcohols. This fraction has numerous uses, primarily to give emollient and emulsification properties to products in the personal care industry. By contrast, however, the woolwax acid fraction, although utilised to some extent in the personal care industry, has not found the same number of end user markets. This may in part be due to the highly complex nature of the fatty acids within the woolwax acid fraction which would by convention be considered as an impure source of fatty acids when compared to the use of oil seed triglycerides or tallow. Woolwax acids have a complex lipid profile consisting of iso, ante-iso and normal fatty acids and iso and nonnal alpha hydroxy fatty acids having carbon backbone skeletons ranging in carbon chain length from eight to thirty carbon atoms. More specifically the iso and normal alpha hydroxy fatty acid carbon backbone skeletons range in carbon chain length from fourteen to twenty six carbon atoms. Table 1.0 (hereinafter) shows the typical fatty acid groups within the woolwax acid lipid profile and also indicates the typical total levels of these groups within the said profile. The most abundant fatty acid within the woolwax acid composition is alpha hydroxy palmitic acid which ranges from 10% w/w to 16% w/w and, more particularly, 11% w/w to 14% w/w.
As the understanding of cosmetic ingredients and their potential modes of action have advanced, a market requirement has developed for specifically purified fractions of the woolwax acids. For example, the alpha hydroxy acid (AHA) components are believed to reduce the symptoms of skin ageing that result from sun exposure and other environmental factors. The effects of the AHA's within an emollient based cream are met with reductions in the following symptoms, mottled hyperpigmentation, fine and course wrinkling, laxity, sallowness, telangiectasia and tactile roughness. The AHA product is believed to exhibit these improvement qualities only when correctly formulated. In the case of reducing skin roughness, for example, the mode of action is by limiting the degree of transepidermal water loss.
Contained within the ante-iso fatty acid homologues of the woolwax acid fraction is the important lipid 18-MEA. This is a major structural lipid found as the major fatty acid species within the hair lipid matrix of mammalian hair (D. J. Fleet, R. E. H. Wettenhall, D. E. Rivett and A. K. Allen; A comparative study of covalently-bound fatty acids in keratinized tissues,
Comp. Biochem. Physiol, Vol
102B, No.2, 363-366, (1992). This ante-iso fatty acid has been demonstrated as the active ingredient when formulated within hair care products. 18-MEA is also found as part of the wax ester matrix which makes up Woolwax. The long chain ante-iso fatty acid is typically found at levels of 1% w/w to 4% w/w of the woolwax acids, though more usually at levels of 2% w/w to 3.5 w/w.
Because of the commercial interest in 18-MEA and the AHA's, efforts have been made to obtain purified versions of these materials. For example, the isolation of AHA's from woolwax and woolwax acids has been attempted using various approaches eg. transit metal chelation (A. H. Milburn and E. V. Truter, Extraction of 2-hydroxy acids from Wool Wax Acids,
J. Appl. Chem;
12, 156-160 (1962) and solvent fractionation (Downing, Solvent Fractionation of Wool Wax Acids,
Aust. J Appl. Sci.,
14 (No. 1) 50-56, (1962), and Beiersdorf A G, EP-A-555776).
A complicating factor in the separation of AHA's from woolwax and woolwax acids is the thermal instability of the AHA moiety due to the presence of the hydroxyl functionality in the alpha position which not increase the acidity of the carboxylic acid group but also gives a centre for further side reactions. This thermal lability results in the formation of lactones/estolides and polymers. The net result of these reactions means that the woolwax acid has a significant reduction in the total amount of AHA that can be recovered. This degradation is well documented (see for example W. R. Noble, A. Eisner and J. T. Scanlan, isolation of a Hydroxy Acid Concentrate from Wool Wax Acids,
JAOCS,
37, 14-16, (1960)).
As far as 18-MEA is concerned, the concentration of this component in woolwax acid is fairly low, typically in the range of 1 to 4% w/w and more specifically 2.5 to 3.5% w/w. These variations are accounted for according to the geographical location of the raw material and the breed of sheep from which the woolwax was scoured. It would also appear that little work has been carried out for the isolation of this material from woolwax. Work has been done to isolate the integral 18-MEA from the hair lipid matrix of mammalian hair but, this is not a commercial route since it does not permit the recovery of large enough quantities of the acid for the personal care market. Attempts have been made to synthesise 18-MEA but, in general, these involve complex multistep processes which inevitably result in low yielding routes to the desired product. The synthetic material also faces the problem of being accepted within the personal care sector as it has not been derived from a natural source which automatically places it at a disadvantage.
It is therefore, highly desirable to achieve a cost effective and robust process to isolate both an AHA enriched and an 18-MEA enriched lipid blend directly from woolwax acids.
According to the present invention, there is provided a process for recovering 18-methyl eicosanoic acid (18-MEA) and/or alphahydroxy acids from woolwax acids or derivatives thereof, which comprises heating the woolwax acids or derivatives thereof to 100° to 230° C. to form estolides and polymeric species; distilling to obtain a distillate and a residue; and recovering 18-MEA from the distillate and/or recovering alpha hydroxy acids from the residue.
The process of the invention surprisingly relies for its selectivity on the ability of the AHA's to form the estolide and polymeric species. This has hitherto been seen as an undesirable feature in the isolation of AHA's from woolwax.
The preferred feedstock of the invention is the woolwax acids as obtained from saponification of woolwax, but certain derivatives of woolwax acids can also be used as the feedstock for this invention, provided that the derivatives form estolides and polymers upon heat treatment. Suitable derivatives would be esters involving the acid functionality of the woolwax and/or esters of the hydroxyl functionality of the AHA's. Examples of suitable derivatives would include methyl, ethyl and propyl esters of the woolwax fatty acids, and formates and acetates of the AHA's within the woolwax acid mixtures. Preferably, woolwax acids are used as this involves fewer processing steps and in this way gives the 18-MEA concentrate in the more desirable free acid form. The form of the AHA has no consequence as the saponification step hydrolyses directly to the free fatty acid.
In the process of the invention, the woolwax acid (or derivatives) feedstock is heated to 100° C. to 230° C., preferably 150° C

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