Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1997-10-07
2004-01-20
Parsa, J. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06680392
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an improved process for removing polysorbitols from sorbitan esters. More particularly, the invention relates to the use of silica to remove polysorbitols from sorbitan ester solutions.
BACKGROUND OF THE INVENTION
Sorbitan fatty acid esters have wide spread utility in many areas as an emulsifying agent in the formation of both water-in-oil and oil-in-water emulsions. Generally, sorbitol and a fatty acid, or a combination of fatty acids are reacted at a temperature greater than about 200° C., under a flow of inert gas, in the presence of an acidic or basic catalyst, to produce sorbitan fatty acid esters. A combination of mono-, di-, tri-, and tetra-esters of sorbitan as well as impurities such as polyols formed by the self-condensation of sorbitan molecules, unreacted sorbitans and isosorbides are produced from this process. These impurities are also present in the commercial sorbitan ester products.
It has been found that these polysorbitol impurities tend to form an undesirable sludge during an emulsifying process. Therefore, it is desirable to remove these impurities from the sorbitan fatty acid esters, after their production via esterification, in order to avoid the undesirable production of sludge.
Previous methods of extracting these impurities from the sorbitan ester mixtures have involved the dissolution of the sorbitan esters into a solvent, treatment with an aqueous metal salt to form separate phases, i.e., organic and aqueous, followed by separation of the organic phase from the aqueous phase.
Another method involves allowing these polyol impurities to settle out of the sorbitan ester mixture, over:a prolonged period of time, followed by their removal from the bottom of the esterification reactor.
SUMMARY OF THE INVENTION
The present invention is directed to a process for removing polyol impurities from sorbitan ester solutions involving:
(a) providing a sorbitan ester solution containing polyol impurities;
(b) adding to the solution from about 0.01 to about 10% actives, based on the total weight of the final crude ester product, of a silica component;
(c) adsorbing the polyol impurities onto the silica component to form a mixture of polyol-containing silica and sorbitan ester; and
(d) filtering the polyol-containing silica from the sorbitan ester solution.
DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions are to be understood as being modified in all instances by the term “about”.
It has surprisingly been discovered that sorbitan ester solutions can be rid of polyol impurities contained therein, such as isosorbides and polysorbitols, thereby rendering the resultant sorbitan ester solution clear in appearance, by the addition of a clarifying-effective amount of a silica component. During the esterification of sorbitols with fatty acids to form sorbitan esters, the unreacted sorbitols have a tendency to self-condense, thereby forming a type of sugar polymer/impurity. The presence of these impurities in the sorbitan ester solution causes the sorbitan esters to appear hazy/cloudy.
Suitable sorbitan esters which may be clarified by the process of the present invention are those corresponding to formula I:
wherein R′, R″,R′″ and R″″ may be, indvidually,
wherein x is an integer form 0-2 an unsaturated fatty acid such as oleate, linoleate, patmitoleate, myristoleate.
Examples of suitable sorbitan esters which may be clarified by the process of the present invention include, but are not limited to, sorbitan sesquioleate, sorbitan trioleate, sorbitan monooleate, sorbitan monopalmitate, sorbitan monostearate and sorbitan tristearate.
Suitable silicas which may be employed in the process of the invention include, but are not limited to, crystalline, a morphous, hydrous and anhydrous.
The term amorphous, when used to describe silica, denotes a lack of crystalline structure, as defined by x-ray diffraction. Some short-range organization may be present and is indicated by electron-diffraction, but this ordering gives no sharp x-ray diffraction pattern. Silica can be either hydrated, i.e., up to ca 14%, or anhydrous. The chemical bonding in amorphous silica is of several types, including siloxane (—Si—O—Si), silanol (Si—O—H), and at the surface, silane (Si—H) or organic silicon (—Si—O—R or —Si—C—R).
Silica gel is a coherent, rigid, continuous three-dimensional network of spherical particles of colloidal silica. Silica gels are classified into three types: regular density gel, intermediate-density gel, and low-density gel. Silica powder can be made by grinding or micronizing dried gels, which decreases the size of the gel fragments but leaves the ultimate gel structure unchanged. Gels and powders are characterized by the density, size, and shape of the particles, particle distribution, and by aggregate strength or coalescence.
When silica is used as an adsorbent, the pore structure determines the gel-adsorption capacity. Pores are characterized by specific surface area, specific pore volume (total volume of pores per gram of solid), average pore diameter, pore-size distribution, and the degree to which entrance to larger pores is restricted by smaller pores.
While all of the above-disclosed silica types possess some polyol-removal capabilities, a particularly preferred silica is a hydrated amorphous silica, preferably in powder form. A commercial example of a preferred silica is BRITESORB® PM 5108 Hydrous Silica, available from PQ Corp.
For convenience, the inventive process will be described in terms of its preferred embodiment, in which a hydrated amorphous silica is employed. In a typical process, sorbitol and fatty acid esters are esterified in a reactor, in the presence of a catalyst. Since the processes by which sorbitan esters are formed is well known in the art, the particulars regarding their formation need not be addressed herein. Once the esterification reaction is complete, a solution containing sorbitan esters and polyol impurities is formed. To this solution there is then added, with agitation, and at a temperature of from about 30° C. to about 80° C., and preferably at from about 50° C. to about 70° C., from about 0.01 to about 10% actives, and preferably about 1% actives, based on the total weight of the final crude ester product formed, of a hydrated amorphous silica. The hydrated amorphous silica is allowed to adsorb the polyol impurities from the sorbitan ester solution, while under agitation, for a period of from about 20 to about 60 minutes, and preferably about 30 minutes, resulting in the formation of a polyol-containing silica dispersed in the sorbitan ester solution.
The silica was found to rapidly adsorb polyol impurities from the sorbitan ester solution, rendering the purified sorbitan ester solution, after filtration, clear in appearance. By employing the hydrated amorphous silica to remove polyol impurities from the reaction mixture, the downtime associated with the previous process which involved waiting for these impurities to settle out of the reaction mixture, was significantly shortened from about 8 hours to about 30 minutes.
The polyol-containing silica is then removed from the sorbitan ester reaction solution by any conventional filtration means. One example thereof involves passing the sorbitan ester reaction solution containing the polyol-containing silica dispersed therein through a filtration apparatus which simultaneously collects the polyol-containing silica while allowing the clarified sorbitan ester solution to pass through. Any known filtration apparatus capable of collecting solid particles may be employed such as, for example, a plate and frame press.
A plate and frame press apparatus filters product in the following way. The crude product, in this case the mixture of polyol-containing silica and sorbitan ester, enters a precoat tank attached to the end of a press. At the bottom of the precoat tank is a pipe going to
Barnhorst Jeff A.
Oester Dean A.
Cognis Corporation
Drach John E.
Parsa J.
Trzaska Steven J.
LandOfFree
Process for removing polysorbitols from sorbitan esters does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for removing polysorbitols from sorbitan esters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for removing polysorbitols from sorbitan esters will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3225736