Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-06-08
2001-03-20
Lee, Howard C. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C510S470000, C536S004100
Reexamination Certificate
active
06204369
ABSTRACT:
BACKGROUND OF THE INVENTION
Alkyl polyglycosides have been known for at least sixty years. They are nonionic surfactants with low toxicity and gentleness to the skin. They can be made from renewable resources and are rapidly degraded in the environment.
Early processes for the preparation of alkyl polyglycosides were two-step processes. The first step comprised the reaction of a lower alcohol having 1 to 6 carbon atoms with a source of saccharide in the presence of an acid catalyst to form the alkyl polyglycoside. These alkyl polyglycosides do not have useful surfactant properties. Since water is miscible with, or highly soluble in, the alcohols, the reaction mixture can contain substantial quantities of water (see U.S. Pat. No. 4,721,780). The higher alkyl polyglycosides in which the aliphatic group contains from 7 to 22 carbon atoms, were prepared by transacetalization of the lower glycosides with higher fatty alcohols under substantially anhydrous conditions.
More recently, alkyl polyglycosides having alkyl groups with from 7 to about 22 carbon atoms have been prepared by a “direct process”. In the “direct process” a long chain fatty alcohol is reacted with a source of saccharide in the presence of an acid catalyst under conditions in which the water formed in the reaction is removed as quickly as it is formed to maintain the water content of the reaction mixture at as low a level as is reasonably possible. The water formed in the reaction is only slightly soluble in the fatty alcohol and any undissolved water results in the rapid formation of unwanted byproducts. The parameters of the “direct process” were set out in U.S. Pat. No. 3,839,318, which is incorporated herein by reference. Other patents such as U.S. Pat. Nos. 4,939,245, 4,950,743 and 5,003,057 also describe the “direct process” and are incorporated herin by reference.
In the direct process an anhydrous source of saccharide or a hydrous saccharide source mixed with an alcohol, present in stoichiometric excess, is heated under reduced pressure to remove the water. An acid catalyst is added to the mixture of saccharide source and fatty alcohol and after the water has been substantially eliminated, the mixture is heated under reduced pressure to form the alkyl polyglycoside. As an alternative, a slurry of anhydrous saccharide and alcohol can be formed. The slurry is then added to a heated second portion of alcohol. It is preferred to use a hydrous saccharide source since hydrous saccharide sources are much less expensive than the anhydrous material.
Sources such as 70% high dextrose syrup being liquids, are easier to handle, easier to pump and significantly less expensive then the anhydrous sources presently being used, but have not been used because of the inherent problems caused by the water present. Water in the reaction is only slightly soluble in the fatty alcohol and any undissolved water results in the rapid formation of unwanted byproducts. Also high dextrose syrup is less pure then other forms of dextrose presently being used. It is therefore desirable to find a method of producing alkyl polyglycoside which can use a hydrated saccharide, such as high dextrose syrup, as a source of dextrose as a raw material in the process.
SUMMARY OF THE INVENTION
One aspect of the invention pertains to a process for preparing a substantially dry mixture of a saccharide in a solvent such as an alcohol. The first step of the process comprises mixing a dextrose syrup with an amount of a C
7-22
fatty alcohol sufficient to thoroughly wet the saccharide. In the next step a second portion of a second C
7-22
fatty alcohol is added to the mixture to form a dispersion. The third step involves allowing the dispersion to stand for a period of time sufficient to form solid particles. The dispersion forms as a semi solid mass which is broken into smaller particles. The next step comprises reducing the water content of the dispersion subsequent to the solid particles being formed by reducing the pressure to from about 100 to about 1 mm Hg and a temperature wherein the lower temperature limit is selected such that the solvent is maintained in a liquid phase.
Another aspect of the invention pertains to a process for producing alkyl polyglycosides which utilizes the substantially dry saccharide-solvent mixture described above. This process is comprised of all of the above steps plus reacting the C
7-22
fatty alcohol with the saccharide in the presence of an effective amount of an acid catalyst at a temperature of from about 80° C. to about 140° C. under a reduced pressure to form a reaction mixture containing the alkyl polyglycoside.
The present invention permits the manufacture of an alkyl polyglycoside using a relatively inexpensive liquid, high dextrose carbohydrate syrup as a raw material and the simultaneous process advantages of using an anhydrous dextrose. The anhydrous dextrose is formed with minimal energy requirements compared to known dehydration methods.
DETAILED DESCRIPTION OF THE INVENTION
The term “fatty alcohol” as used herein refers to aliphatic alcohols having from about 7 to about 22 carbon atoms. The alcohol may also be an alkoxylated alcohol represented by the formula:
RO(CR
1
H—CH
2
O)
y
H
wherein R is the residue of a fatty alcohol containing form about 7 to 22 carbon atoms, R1 is H, CH3, or —CH2-CH3 and Y is a number form 0 to 5. The alcohols can be saturated or unsaturated, natural or synthetic, straight chain or branched chain. The fatty alcohol used in the process of the invention can be a single alcohol or a mixture of alcohols. Preferably, the fatty alcohols are aliphatic alcohols having from 8 to about 18 carbon atoms. Alcohols having aromatic or other cyclic moieties in their structure can also be reacted but the glycosides formed are generally not as biodegradable as the glycosides formed from aliphatic alcohols.
All pressures expressed in mm Hg are absolute pressures unless otherwise noted.
The term extinction coefficient as used herein refers to the calculated absorbance of a theoretical solution containing one gram of solid material per cubic centimeter of solution measured and calculated according to the formula:
E470=A/(C*L)
Wherein:
A=measured absorbence at 470 nm
C=concentration in grams per cm3
L=path length in centimeters and
E(479)=extinction coefficient at 470 nm
As used herein, a “hydrous saccharide source” refers to a reducing sugar or an oligomer or polymer comprising moieties of a reducing sugar which under the acid conditions of the process forms a reducing saccharide required to react with the alcohol. Examples of some saccharides that can be used are any 6 carbon or 5 carbon sugars such as dextrose, mannose, xylose or arabinose. The term “hydrous” refers to a solid or liquid saccharide source which contains water. Materials such as dextrose monohydrate, solidified high dextrose corn syrup, liquid high dextrose corn syrup and the like have been found useful to prepare the alkyl polyglycosides by the improved process of the invention.
The term “alkyl polyglycoside” is used to denote a composition of the formula:
RO(CR
1
H—CH
2
O)
y
G
x
wherein R is the residue of a fatty alcohol having from about 7 to about 22 carbon atoms; R
1
is H, CH
3
or CH
2
CH
3
, G is the residue of a reducing saccharide; y is an average number of from 0 to about 5; and x is an average number of from 1 to about 5. Preferably x is a number of from 1 to about 2.5.
G is the residue of a reducing saccharide. The residue of a reducing saccharide can be the residue of a monosaccharide such as glucose, fructose, lactose, mannose, xylose and the like or the residue or fragments of a polysaccharide or oligosaccharide such as isomaltose, maltose, cellobiose, mellobiose, maltotriose and the like. The oligosaccharides can undergo transglycosidation under the acid conditions and elevated temperature of the process to produce the reducing saccharide moieties which react with the alcohol and/or a hydroxyl of a mono or polyglycoside.
The source of saccharides useful in the practice of the prese
Edwards Frank L.
McCurry, Jr. Patrick
Roth C. Deane
Drach John E.
Ettelman Aaron R.
Fobare Rossi Joanne Mary
Henkel Corporation
Lee Howard C.
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