MXPA00003250A - Process for removing polysorbitols from sorbitan esters - Google Patents

Abstract

A process for removing polyol impurities from a sorbitan ester solution involving:(a) providing a sorbitan ester solution containing polyol impurities;(b) adding to the sorbitan ester solution a clarifying-effective amount of a silica component;(c) adsorbing the polyol impurities from the sorbitan ester solution onto the silica to form a mixture of sorbitan ester and polyol-containing silica;and (d) removing the polyol-containing silica from the sorbitan ester solution.

Description

PROCESS TO SEPARATE POLISORBÍ OLES FROM SORBITAN ESTERS FIELD OF THE INVENTION: The present invention, in general, relates to an improved process for separating polysbritols from sorbitan esters. More particularly, the invention relates to the use of silica to separate polysorbitols from solutions of sorbitan esters.

BACKGROUND OF THE INVENTION Sorbitan fatty acid esters have wide utility in many areas as an emulsifying agent in the formation of water-in-oil and oil-in-water emulsions. In general, the 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 a basic acid catalyst, to produce fatty acid esters of sorbitan. From this process a combination of mono-, di-, tri- and tetra-esters of sorbitan is produced, as well as impurities such as polyols formed by self-condensation of sorbitan molecules, unreacted sorbitans and isosorbides. These impurities are also present in the commercial sorbitan ester products. It has been found that these polysorbitol impurities they tend to form an undesirable mud during an emulsification process. Therefore, it is desirable to separate these impurities from the fatty esters of sorbitan fatty acids, after their production through their esterification, to avoid the undesirable production of sludge. The above methods for extracting these impurities from sorbitan ester mixtures have included the dissolution of sorbitan esters in a solvent, the treatment with an aqueous metal salt to form separate phases, ie the organic and aqueous phase, followed by the separation of the organic phase from the aqueous phase. Another method includes allowing these impurities polyols to settle out of the mixture of sorbitan esters, for a prolonged period of time, followed by their separation from the bottom of the esterification reactor.

SUMMARY OF THE INVENTION: The present invention is directed to a process for separating polyol impurities from solutions of sorbitan esters including: (a) providing a solution of sorbitan ester containing polyol impurities; (b) add to the solution from about 0.01 to about 10% of assets, based on the total weight of the final crude ester product, of a silica component; (c) adsorbing the impurities of polyols in the silica component to form a mixture of silica containing the polyol and sorbitan ester; and (d) filtering the solution of esters from sorbitan the silica containing the polyol.

Description of the invention: In addition to the operant examples, or where otherwise indicated, all numbers expressing amounts of ingredients or reaction conditions should be understood as modified in all cases by the term "approximately". Surprisingly it has been discovered that solutions of sorbitan esters can be released from impurities of polyols contained therein, such as isosorbides and polysorbitols, thus producing the resulting sorbitan ester solution of clear appearance, by adding an effective amount as a clarifier of a silica component. During the esterification of sorbitols with fatty acids to form sorbitan esters, sorbitols which do not react have a tendency to self-condense, thereby forming a type of sugar / impurity polymer. The presence of these impurities in the solution of sorbitan esters causes that sorbitan esters have a cloudy appearance. Suitable sorbitan esters that can be clarified by the process of the present invention are those corresponding to formula I: where R /, R ", R" ', and R "" can be, individually, H, CH3 (CH) XC- where x is an integer of 0-22 or an unsaturated fatty acid such as oleate, linoleate, palmitoleate, myristoleate. Examples of suitable sorbitan esters that can 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 tristearate monostearate. sorbitan. Suitable silicas that can be employed in the process of the invention include, but are not limited to, crystalline, amorphous, hydrated and anhydrous.

The term amorphous, when used to describe silica, denotes an absence of crystal structure, defined by X-ray diffraction. Some short-range organization may be present and indicated by electronic diffraction, but this arrangement does not give a diffraction pattern. accurate X-ray The silica can be hydrated, that is, up to about 14%, or anhydrous. The chemical bond in amorphous silica is of various types, including siloxane (-Si-O-Si), silanol (-Si-OH), and on the surface, silane (Si-H) or organic silicon (Si-OR or -Yi-CR) Silica gel is a coherent, rigid and continuous three-nsional network of spherical colloidal silica particles. Silica gels are classified into three types: regular density gel, intermediate density gel and low density gel. The silica powder can be prepared by grinding or micronizing dry gels, which decreases the size of the silica fragments but leaves the final gel structure unchanged. The gels and powders are characterized by the density, size and shape of the particles, the distribution of the particles and by the resistance of the aggregate or coalescence. When silica is used as an adsorbent, the pore structure determines the adsorption capacity of the gel. The pores are characterized by the specific surface area, the specific volume of the pore (total volume of pores per gram of solid), average pore diameter, pore size distribution, and the degree to which entry into larger pores is limited by smaller pores. Although all the types of silica described above possess some ability to separate the polyol, the particularly preferred silica is an amorphous hydrated silica, preferably in the form of a powder. A commercial example of a preferred silica is BRITESORB® PM 5108 hydrated silica, available from PQ Corp. For convenience, the process of the invention will be described in terms of its preferred embont, in which amorphous silica hydrate is employed. In a common 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 are well known in the art, the details related to their formation need not be mentioned here. Once the esterification reaction is complete, a solution containing sorbitan esters and polyol impurities is formed. To this solution is then added, with stirring, and at a temperature from about 30 ° C to about 80 ° C, and preferably from about 50 ° C to about 70 ° C, from about 0.01 to about 10% active and , preferably, about 1% of active, based on the total weight of the final crude ester product formed, of an amorphous hydrated silica. The hydrated amorphous silica is allowed to adsorb the polyol impurities of the sorbitan ester solution, with stirring, for a period of from about 20 to about 60 minutes and, preferably, about 30 minutes, giving rise to the formation of a polyol-containing silica. dispersed in the sorbitan ester solution. It was found that the silica quickly adsorbs the polyol impurities from the sorbitan ester solution, rendering the purified sorbitan ester solution, after filtration, with a clear appearance. By using the amorphous hydrous silica to remove polyol impurities from the reaction mixture, the dead time associated with the above process which included waiting for the impurities to settle out of the reaction mixture was significantly shortened from about 8 hours to about 30 hours. minutes The polyol-containing silica is then separated from the reaction solution of sorbitan esters by any common filtration medium. An example of these includes passing the reaction solution of the sorbitan ester with the polyol containing silica dispersed therein through a filtration apparatus which at the same time collects the silica containing the polyol and allowing the ester solution of clarified sorbitan pass through it. It is possible to use any known filtration apparatus, capable of collecting these solid particles such as, for example, a plate and frame press. A plate and frame press apparatus filters the product in the following manner. The crude product, in this case the mixture of silica containing polyol and the sorbitan ester, enters a tank with pre-coating attached to the end of a press. In the lower part of the pre-coating tank is a tube that goes to a pump located under the press. The pump sucks the raw product from the pre-coating tank and pushes the raw product to the plate and frame section of the press. The plate is covered on both sides of filter paper. The product is introduced into the plate through a hole in the bottom of the plate. Then the material is pushed through the paper and onto the frame that has channels in it to bring the clean product out to the other side of the plate. The plate has two holes, one on the lower right side (raw), the other on the upper left side (clean). A plate and frame press apparatus can have from 1-20 plates and frames. Another common filtration apparatus that can be used to separate the polyol impurities from the sorbitan ester solution is a centrifuge. The centrifugation is a separation technique based on the application of centrifugal force to a mixture or suspension of materials. The present invention will be better understood from the following examples, all of which are illustrative only and are not to be understood as unduly limiting the scope of the invention in any way.

E «TEMPLES Sorbitan mono-oleate was prepared by charging a reactor with 40% by weight of a sorbitol, 60% by weight of oleic acid and 0.25% by weight of sodium hydroxide acting as a catalyst. Once the reaction process is complete, the resulting sorbitan monooleate solution is cooled to approximately 65 ° C. A hydrated silica, commercially available under the name BRITESORB®, was then added to the cooled solution of sorbitan monooleate in an amount of 1% by weight, based on the total weight of the solution in the reactor after it was I reached an acid number of 2. The mixture of sorbitan monooleate and hydrated silica was then mixed for 20 minutes to allow the polyol impurities to be absorbed by silica, after which the impurities were immediately filtered by press. The final product of sorbitan monooleate ester was clear in appearance. ?or COMPARATIVE EXAMPLE Sorbitan monooleate was prepared by the process described above. Once the acid number of the resulting sorbitan monooleate solution was adjusted to the desired level, the polyol impurities contained therein were separated allowing them to settle out of solution for a period of 10 hours. As can be seen from the data described, using the process of the present invention to separate the polyol impurities from the sorbitan esters, the dead time associated with their separation decreases significantly.

Claims (21)

1. A process for separating polyol impurities from a sorbitan ester solution consists of: (a) providing a solution of sorbitan esters containing polyol impurities; (b) adding to the sorbitan ester solution an effective amount as a clarifier of a silica component; (c) adsorbing the polyol impurities of the sorbitan ester solution onto the silica to form a mixture of silica containing the polyol and ester sorbitan; and (d) separating the polyol-containing silica from the sorbitan ester solution.

2. The process of claim 1, wherein from about 0.01 to about 10% of active silica component, based on the total weight of the final crude ester product, sorbitan ester solution is added to the solution.

3. The process of claim 2, wherein about 1% of active silica component, based on the total weight of the crude ester final product, is added to the sorbitan ester solution.

4. The process of claim 1, wherein the silica component is an amorphous, hydrated silica powder.

5. The process of claim 1, wherein the silica is add to the sorbitan ester solution at a temperature from about 30 ° C to about 80 ° C, with stirring.

The process of claim 1, wherein the sorbitan ester is selected from the group consisting of sorbitan sesquioleate, sorbitan trioleate, sorbitan monooleate, sorbitan monopalmitate, sorbitan monostearate and sorbitan tristearate.

The process of claim 1, wherein the polyol impurities are adsorbed onto the silica for a period of from about 20 to about 60 minutes.

The process of claim 1, wherein the polyol containing silica is separated from the sorbitan ester solution using an apparatus for filtration.

9. The process of claim 8, wherein the filtration apparatus is a plate and frame press.

The process of claim 7, wherein the polyol impurities are adsorbed onto the silica for a period of about 30 minutes.

The process of claim 6, wherein the sorbitan ester is sorbitan monooleate.

12. The product of the process of claim 2.

13. The product of the process of claim 3.

14. The product of the process of claim 4.

15. The product of the process of claim 5.

16. The product of the process of claim 6.

17. The product of the process of claim 7.

18. The product of the process of claim 8.

19. The product of the process of claim 9.

20. The product of the process of claim 10,

21. The product of the process of claim 11.