Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-11-27
2003-12-30
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C528S275000, C528S300000, C528S302000, C528S307000, C528S308000, C528S308600, C528S403000, C528S499000, C428S357000, C430S321000
Reexamination Certificate
active
06670033
ABSTRACT:
FIELD OF THE DISCLOSURE
The present disclosure relates to a process for the purification of anhydrosugar alcohols by distillation and/or recrystallization in the presence of an aliphatic alcohol, and the products of the purification, which are desirably greater than 99.0% pure and, even upon thermal treatment, are substantially colorless.
BACKGROUND OF THE DISCLOSURE
Anhydrosugar alcohols, in particular derivatives of mannitol, iditol, and sorbitol, are known for their therapeutic uses and uses in food. Further, at least isosorbide, 1,4:3,6-dianhydrosorbitol, is being examined as a renewable natural resource for the manufacture of polymers, especially polyesters, because isosorbide is a derivative of sorbitol, which can be derived from various natural resources, including corn starch and cassava (tapioca). See related applications on processes of making and products made from polymers having isosorbide, terephthaloyl and ethylene glycol moieties, U.S. patent applications Ser. Nos. 09/064,844; 09/064,950; 09/064,846; 09/064,858; 09/064,826; 09/064,719; 09/064,862; and 09/064,720, all filed Apr. 23, 1998, each of which are incorporated in their entirety by reference.
The purity requirements for the use of anhydrosugar alcohols differ depending upon the intended application. In food and drug applications, for example, one requirement is that there be no impurities that cause harm to the individual or organism using the material containing the anhydrosugar alcohol. By this definition, an anhydosugar alcohol may contain numerous other materials or impurities that are not anhydrosugar alcohols and yet still be considered pure for a food or drug application. In polymer applications, especially those that require optical clarity, such as polymers used in packaging, one monomer purity requirement is that there not be any materials or impurities present in the monomer that could cause the resultant polymer to develop an unacceptable degree of color during synthesis and/or processing. Impurities that may be permissible in anhydrosugar alcohols used for food and drug applications may not in fact be acceptable for anhydrosugar alcohols that are to be used in polymer applications because those impurities may lead to the development of an unacceptable level of color during the synthesis or processing of the polymer.
Several methods of purifying anhydrosugar alcohols are known in the art. For example, such alcohols can be purified by vacuum distillation or recrystallization from an organic solvent such as ethyl acetate and/or ether, as disclosed in Flèche and Huchette, “Isosorbide: Preparation, Properties and Chemistry,” starch/stärke 38 (1986) Nr. 1, pp. 26-30 at 29, or methyl ethyl. ketone as disclosed in U.S. Pat. No. 3,454,603. However, these methods do not sufficiently remove impurities that may lead to the development of an unacceptable level of color during polymer synthesis and/or processing.
Purification by recrystallization from water is also known, as disclosed in Beck, “Dianhydrosorbitol—a new pharmaceutical ingredient,”
Pharmaceutical Manufacturing International
, p.97-100 at 97-98 (1996), although the product resulting from this is only about 97% pure. Generally, water is undesirable as a solvent because anhydrosugars are extremely hygroscopic.
Purification by distillation under reduced pressure in the presence of borohydride ions has also been proposed, as disclosed by Flèche and Huchette, p. 29, and as described in U.S. Pat. No. 3,160,641 for the reduction of periodate-consuming impurities in isosorbide using boric acid.
Methods are also known for the purification of anhydrosugar alcohol derivatives, and for purification of anhydrosugar alcohol precursors. Purification of specific anhydrosugar alcohol derivatives by recrystallization from methanol and ethanol is demonstrated in, for example, Hockett et al.
J. Am. Chem. Soc
., Vol. 68, p.930-935 (1946); Copeand Shen,
J. Am. Chem. Soc
. p.3177-3182 (1956); and Ojrzanowski et al.,
Acta Pol. Pharm
. 43(6) p.567-71 (1986).
Further, purification of precursors such as D-mannitol and D-glucitol by extraction or recrystallization from ethanol or a mixture of ethanol and water, respectively, are demonstrated by Block et al. in
Acta Chem. Scan
. (43) p.264-268 (1989).
The use of methanol and ethanol in the recrystallization of precursors and derivatives of anhydrosugar alcohols is also demonstrated by Defaye et al.,
Carb. Res
. 205 p.191-202 (1990). Defaye et al. also demonstrates recrystallization of A dianhydrosugar alcohols, specifically, 1,4:3,6-dianhydro-D-mannitol and 1,4:3,6-dianbydro-D-glucitol. However, these recrystallizations do not use aliphatic alcohols such as methanol, ethanol or ethylene glycol as solvents.
A method of purification of monoanhydrohexitols and dianhydrohexitols is also set forth in U.S. Pat. No. 4,564,692 to Feldmann et al. However, this process requires placing the anhydrosugar alcohol in a heavy liquid having 1-20% water by weight and adding seed crystals of the desired anhydrosugar alcohol to be recrystallized.
There is no known teaching of purifying an anhydrosugar alcohol by recrystallization from aliphatic alcohols such as methanol, ethanol or ethylene glycol. The above processes, as known in the art, are directed to purification of the anhydrosugar alcohol for use in food or pharmaceutical compositions. The inventors herein are unaware of any previous purification process achieving the required level of purity for use in polymers.
In view of the above, a simple and cost effective method of purifying anhydrosugar alcohols, resulting in an extremely pure product, is desired. Further, an extremely pure anhydrosugar alcohol is desired, particularly for use in polymer formation.
SUMMARY OF THE DISCLOSURE
The inventors of the present disclosure have discovered that recrystallization from lower aliphatic alcohols, such as methanol and ethanol, as well as melt recrystallization, improves the purity and clarity of color of anhydrosugar alcohols. Distillation also improves the purity of the end product, and may optionally be done over sodium borohydride (NaBH
4
) or other hydride ion containing compounds. A combination of distillation and solvent or melt recrystallization markedly improves the purity of the end product. Similarly, multiple distillations and/or multiple recrystallizations from lower aliphatic alcohols have been found to markedly increase the purity of the anhydrosugar alcohol.
Further, it is disclosed herein that the purity of the anhydrosugar alcohols is best measured with regard to the relative color of the anhydrosugar alcohol and its ultraviolet (LN) transmittance. A method for obtaining such measurements is herein disclosed.
Also, a method of determining the quality of polymers prepared with the purified anhydrosugar alcohol is disclosed, wherein the anhydrosugar alcohol is annealed at temperatures approaching those used in polymer formation, thereby testing the development of color in the annealed anhydrosugar alcohol at the elevated temperatures necessary for the formation of polymers. The coloring of the resultant annealed anhydrosugar alcohol is indicative of the color that may develop during synthesis and/or processing of the resultant polymer.
Further, use of the purified anhydrosugar alcohols resulting from the above methods in the formation of polymers and products formed therefrom is described.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE DISCLOSURE
The process of the invention provides for the purification of anhydrosugar alcohols, whether starting with a commercially available product, or working with a product derived directly from a batch or continuous process for formation of anhydrosugar alcohols.
In the process of the invention, the anhydrosugar alcohol is purified by distillation and/or recrystallization from lower aliphatic alcohols. By “lower aliphatic alcohols” it is meant linear aliphatic alcohols, preferably having 1-4 carbons. Most desirably, the alcohols are methanol, ethanol or ethylene glycol. The resulting purified anhydrosugar alcohol is at le
Charbonneau Larry F.
Hubbard Michael A.
Kohle Norbert
Kvakovszky George
Rieth Jochen
Acquah Samuel A.
E. I. du Pont de Nemours and Company
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