Secondary alcohol esters of hydroxyacids and uses thereof

Details Secondary alcohol esters of hydroxyacids and uses thereof Secondary alcohol esters of hydroxyacids and uses thereof

2000-01-10

2002-06-18

Howard, Jacqueline V. (Department: 1764)

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

Organic compounds

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

C508S501000, C508S463000, C554S219000, C554S163000

Reexamination Certificate

active

06407272

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The invention relates to esters, particularly to esters of secondary alcohols and hydroxyacids, processes for preparing such esters by transesterification, and use of the esters in compositions such as lubricating compositions.
BACKGROUND OF THE INVENTION
Many esters of hydroxyacids, including esters of ricinoleic acid, are described in the literature and/or are commercially available. Castor oil, ergot oil, methyl stearate and methyl ricinoleate are exemplary. Nevertheless, an impediment to preparing additional esters of hydroxyacids, and particularly unsaturated hydroxyacids, is that such esters are susceptible to isomerization and/or alcoholysis in the presence of many reaction conditions that are typically employed to prepare esters. Accordingly, the product ester is in admixture with undesired products. Such undesired products include estolide, which is the ester that forms when the hydroxy group of one fatty acid reacts with the carboxyl group of a different fatty acid molecule. Other undesired products are esters wherein the portion derived from unsaturated fatty acid has a trans rather than cis double bond, and/or the double bond has migrated. Still other undesired products arise upon loss of the hydroxy group to form an additional double bond or where the internal ester is formed.
The following patents, which are exemplary only, describe the preparation of esters containing a hydroxyacid, and specifically ricinoleate esters: U.S. Pat. Nos. 2,486,444; and 1,701,703. The following publications, which are exemplary only, describe the preparation of esters containing the ricinoleate residue: J. American Oil Chemists Society (JAOCS), 67:1375 (1986); JAOCS 73:543 (1996); and JAOCS 73:1385 (1996).
In order to obtain a composition with a high concentration of secondary alcohol ester of a hydroxyacid, it has typically been necessary to perform extensive, and necessarily expensive distillative processes on the product mixture obtained by the ester-forming reaction.
There is a need in the art for a process to prepare esters of hydroxyacids, wherein the alcohol portion of the ester is derived from a secondary alcohol. In particular, there is a need for a process that can be conducted to prepare commercial quantities of secondary alcohol esters of hydroxyacids at a commercially attractive price. The present invention addresses these needs and provides further related advantages as set forth herein.
SUMMARY OF THE INVENTION
The present invention provides a transesterification process wherein a secondary alcohol is reacted with an ester of a hydroxyacid, to provide an ester of the secondary alcohol and the hydroxyacid. Thus, in one embodiment, the present invention provides a process that includes reacting an ester of a hydroxyacid with a secondary alcohol in the presence of a transition metal compound, to form a secondary alcohol ester of a hydroxyacid.
In another embodiment, the present invention provides a process for preparing a secondary alcohol ester of a secondary hydroxyacid according to the formula (R
4
)(R
5
)CH—O—C(═O)—R
2
—CH(OH)—R
3
. Each of R
2
, R
3
, R
4
and R
5
is independently selected from C
1
—C
22
hydrocarbon groups optionally substituted with one or more of halogen, oxygen and nitrogen. The process includes reacting an ester of a secondary hydroxyacid with a secondary alcohol under transesterification conditions. The transesterification conditions include adding an organometallic compound, preferably an organometallic transesterification catalyst, to one or both of the ester of the secondary hydroxyacid or the secondary alcohol.
The invention provides secondary alcohol esters of hydroxyacids, preferably secondary hydroxyacids, and compositions that include the same. The esters and/or compositions may be included in, and form part of, a lubricating composition, i.e., a composition intended for use in an environment wherein it provides lubrication properties. In one specific embodiment, the invention provides capryl alcohol ricinoleate, and compositions that include this ester, where these compositions may have utility as lubricating compositions.
In another embodiment, the present invention provides a composition that includes at least 50 wt % of a secondary alcohol ester of a secondary hydroxyacid, where the weight percent value is based on the total weight of the composition. The secondary alcohol ester of a secondary hydroxyacid is preferably a secondary alcohol ester of a fatty unsaturated secondary hydroxyacid. The secondary alcohol ester of a secondary fatty unsaturated hydroxyacid is preferably capryl alcohol ricinoleate.
In addition, the invention provides a process of improving the lubricity of a composition, where the process includes incorporating the ester as described above into the composition. In addition, the invention provides a process of modifying the friction properties of a composition, that includes incorporating the ester prepared as described above into the composition. These and related aspects of the invention are described further below.
DETAILED DESCRIPTION OF THE INVENTION
Generally, the present invention provides a process for preparing a secondary alcohol ester of a hydroxyacid. The process comprises, that is includes, reacting an ester of a hydroxyacid with a secondary alcohol under transesterification conditions. The transesterification conditions include the addition of an organometallic compound to one or both of the reactants, and/or the presence of an organometallic compound in combination with one or both of the reactants, where the organometallic compound is preferably an organometallic catalyst. The product of the transesterification reaction is an ester having the same hydroxyacid component as the starting ester, but the alcohol component is derived from the secondary alcohol.
As used herein, a “carboxylic acid” refers to an organic molecule that includes a carboxylic acid group (—COOH). A carboxylic acid may be generally represented by the formula Ra—COOH where Ra refers to an organic moiety.
As used herein, a “hydroxyacid” refers to an organic molecule that includes a single hydroxy group (—OH) and a single carboxylic acid group (—COOH). Unless otherwise specified, the hydroxy group of the hydroxyacid may be either primary or secondary, where a primary hydroxy group is bonded to a carbon that is, in turn, bonded to one and only one carbon, and a secondary hydroxy group is bonded to a carbon that is, in turn, bonded to two and only two carbons. The hydroxyacid having a primary hydroxy group will be referred to herein as a primary hydroxyacid, while a hydroxyacid having a secondary hydroxy group will be referred to as a secondary hydroxyacid. Hydroxyacids may be generally represented by the formula HOOC—Ra—OH where Ra is an organic moiety that links together the IOOC— and —OH groups. A fatty hydroxyacid has at least 10 carbons, and is a preferred hydroxyacid of the present invention. An unsaturated hydroxyacid includes at least one double bond in addition to hydroxy and carboxylic acid groups. Unsaturated hydroxyacids are a preferred hydroxyacids of the present invention. Unsaturated fatty hydroxyacids have at least 10 carbons and at least one double bond, in addition to hydroxy and carboxylic acid groups, and are another preferred hydroxyacids of the present invention.
As used herein, an “ester of carboxylic acid” or a “carboxylic ester” refers to an organic molecule wherein the carboxylic acid group (—COOH) of a carboxylic acid (Ra—COOH) has been converted to a carboxylic ester moiety (COO—Rb where Rb is an organic moiety). Conceptually, a carboxylic ester can be described as having an acid component and an alcohol component, where in a carboxylic ester of the formula Ra—COO—Rb, Ra—COOH is the acid component and HO—Rb is the alcohol component. The alcohol component may have either a primary or secondary hydroxy group, so as to be a primary alcohol or a secondary alcohol, respectively. Tertiary alcohols do not work under typical reaction conditions. A primary alcohol ester of a

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