US3476598A - Sucrose based surfactants as aids in sugar refining and sugar crystallization processes - Google Patents

Description

United States Patent 3,476,598 SUCROSE BASED SURFACTANTS AS AIDS IN SUGAR REFINING AND SUGAR CRYSTAL- LIZATION PROCESSES Herbert L. Sanders, Skokie, Ill., assignor to Varney Chemical Corporation, Janesville, Wis., a corporation of Wisconsin N0 Drawing. Filed May 10, 1966, Ser. No. 549,776

Int. Cl. C13 1/02 US. Cl. 127-58 8 Claims ABSTRACT OF THE DISCLOSURE The method of improving sugar recovery and sugar crystal quality consisting of incorporating in sugar crystallization systems uniquely compatible sucrose-derived surface active agents including sucrose esters, sucrose ethers, sucrose ether-esters, and mixtures thereof.

The present invention relates to novel sucrose derived surfactants, to the processes for producing these surfactants, and to their use as processing and crystallization aids in sugar refining operations. More particularly, the present invention is directed to sucrose esters, sucrose ethers, and sucrose ether-esters having surfactant properties uniquely efiicacious in improving the conditions and rates of crystalliaztion of sugars, the overall production yields, and the quality of the ultimate commercial products. Specifically, the present invention is directed to the use of these compounds in sugar refining processes.

The use of surface active agents in sugar processing is known in the prior art and various types of surfactants have been proposed for the general purpose of improving the overall processes involved. For example U.S. Patent No. 2,591,704 discloses for such use the following: (1) partial long chain fatty acid esters of polyhydroxylic compounds which have 3 to 6 carbon atoms per molecule, (2) polyoxyalkylene ethers of (1) wherein the oxyalkylene groups have from 2 to 3 carbon atoms each, (3) polyoxyalkylene esters of long chain fatty acids wherein the polyoxyalkylene groups have from 2 to 3 carbon atoms each, and (4) long chain fatty esters of polyoxyalkylene ethers of polyhydroxylic compounds which have 3 to 6 carbon atoms per molecule wherein the oxyalkylene groups have from 2 to 3 carbon atoms each. Some prior art patents describe surface active agents derived from sugars themselves and US. Patent No. 3,018,281 describes such a water soluble surface active agent produced by reacting sucrose with an aliphatic epoxide having in excess of eight carbon atoms, the epoxide preferably consisting of a mixture of lower aliphatic epoxides such as propylene oxide and butylene' oxide and higher molecular weight epoxides such as dodecane epoxide. US. Patent No. 3,018,282 describes a process for reacting propoxylated (or butoxylated) sucrose with fatty acid halides using an acid catalyst. US. Patent No. 2,908,681 describes fatty acid esters of octakis (2- hydroxypropyl) sucrose, a product having exactly 8 propylene oxide groups per sucrose molecule, and, a 1960 article in The Journal ofthe American Oil Chemists Society (37468) describes the addition of ethylene oxide to previously formed sucrose fatty esters to impart water solubility. In US. Patent No. 2,871,148 fatty acid esters or diesters of glycosides (such as methyl glycoside) are recommended for use in the processing of sugars and in their crystallization. The glycoside esters themselves, together with the methods of their preparation, are described in US. Patent Nos. 2,759,922 and 2,759,923. Still another patent, US. Patent No. 2,893,990, describes a process for producing sugar esters comprising monoand di-fatty acid esters of sucrose or raflinose. These ester products are recommended as having utility for various detergent purposes.

In spite of very extensive research inthe field of synthetic surface-active agents and notwithstanding that specific researches and products have been directed specially to agents for use in sugar crystallization processes, none of the prior art products has proven completely satisfactory for the intended purpose and in each case any particular agent has one or more objectionable features which impair its usefulness. Even surfactants such as fatty acid esters of polyhydroxy compounds having from 3 to 6 carbon atoms per molecule, and polyoxyalkylene ethers of such products in which the oxyalkylene groups have from 2 to 3 carbons each have not been found completely satisfactory. The epoxylated derivatives of sucrose described in the prior art, and having certain surfactant properties, also fail to meet the unique physical and chemical requirements of surface active agents for sugar refining processes. Sucrose ester surfactants, now commercially available (Schwartz and Rader, The Journal of the American Oil Chemists Society, September 1965, vol. 42, No. 9), while apparently generally useful as components of multi-purpose washing compositions, particularly in solid preparations, have been found to be significantly deficient as agents for improving sugar refining processes. It is, therefore, the aim of the present invention to provide improved sucrose-derived surface active agents which avoid the deficiencies and remedy the shortcomings of prior art products of the type finding utility in commercial sugar processing procedures.

It is a principal feature of the sucrose-derived surfactants of the present invention that they are highly effective as processing aids in sugar refining and crystallization.

It is an important object of the present invention to provide sucrose esters, ethers and ether-esters having unique solubility and surfactant properties and possessing improved compatibility characteristics in sugar processing systems and solutions.

A related object is to improve the quality, the rate of crystallization, and the yield of crystalline sugar in sugar processing operations.

Yet another object of the invention is to provide improved sugar processing aids derived from sucrose and having important viscosity-modifying ability whereby interfacial tensions and surface tensions: in sugar crystallization systems are lowered to effect an increase in the number of crystallization centers and the nucleation rate while reducing the tendency of crystals to agglomerate.

Still another object of the invention is to provide sucrose-based surfactants for increasing the fluidity of massecuites to provide better circulation, improved heat exchange characteristics, and more efficient operation in sugar processing systems.

Another feature of the sucrose derived surfactants of the present invention is that sugar solutions: so treated exhibit reduced entrainment and foaming tendencies, more efiicient evaporation, and improved crystal structure and associated filtrability.

In order to disclose more clearly the nature of the present invention, specific examples are set forth here below. It isgto be understood, however, that the examples are intended neither to delineate the scope of the invention nor limit the ambit of the appended claims.

EXAMPLE 1.SUCROSE POLYETHER A sucrose ether-ester embodying the features of the present invention was prepared by reacting the following components in the proportions indicated below 342 grams sucrose (1 mole) 815 grams propylene oxide (14 moles) 2 moles methyl coconate (fatty acid methyl ester in which lauric acid is the predominant fatty acid) The sucrose was reacted with the propylene oxide and the resulting product esterified with methyl coconate to form the lauroyl ester of sucrose polypropoxy propanol. This product added to massecuites in a sugar evaporator decreased the processing time and increased the over-all yield.

Any commercial propylene oxide may be used, one suitable product having the following properties:

B.P.34.2 C.

Sp. gr.0.83 at 25 C.

Refractive index-l.363 at 25 C. Viscosity0.28 centipoise Flash point F.

EXAMPLE 2.SUCROSE ESTER A fatty acid ester of sucrose exhibiting the special surfactant properties and the unique solubility and compatibility in sugar solutions typical of the preparations of the invention was prepared by reacting sucrose with methyl oleate in dimethyl formamide as a solvent. Details of the unit syntheses are well-known in the art, as exemplified in US. Patent No. 2,893,990.

EXAMPLE 3.SUCROSE ETHER-ESTER An alkyl ether of sucrose was prepared by reacting alkoxylated sucrose with an alkyl chloride to form a final product such as lauryl sucryl ether.

Aqueous dilutions of the products produced in each of the examples given above exhibited good sheeting and spreading characteristics in rinse tests carried out at concentrations of 200 ppm. Other detergent properties such as effective soil removal from cotton and from wool cloth were exhibited by dilute solutions (0.5-1.0%) of the products. The sucrose-based surfactants of the present invention provide detergent performance at least equal to conventional ionic surfactants. However, they are markedly superior to these conventional surfactants in their unique efficacy as processing aids in the crystallization of sugar.

In view of the present disclosure, those skilled in the art will be able to apply the teachings of the invention in particular preferred manners. Useful and highly effective typical techniques are set forth in the paragraphs below. The examples are illustrative only and are not intended to limit the invention in any way.

Procedure A In employing the invention in cane sugar processing, the lauryl sucryl ether of Example 3, in a concentration of about 0.1% based on the weight of sugar solids in the massecuite, was added to the crystallizer tank containing the concentrated mother liquor from a second strike. Upon removal of the sugar crystals, the massecuite was spun and purged in the conventional manner.

Procedure B The invention was employed in the processing of beet sugar by addition of about 0.1% of the sucrose polyether of Example 1 to the green syrup in a vacuum pan, whereupon the syrup was boiled and agitated. Upon recovery of the crystalline sugar, in the usual manner, the mother liquor was subjected to a second concentrating step for another strike of sugar, the surfactant being present in each concentrate, to effect the advantages of the invention.

Procedure C The invention was applied in the refining of corn sugar by adding between about 0.01 and 0.05% by weight of the sucrose ester of Example 2 (sucrose dioleate) to the boiling corn syrup, in a vacuum pan. After concentration, the syrup was drawn off, seeded, crystallized and spun.

Procedure D The sucrose-derived surfactants of the invention may be used effectively in purging operations, and in atypical procedure cake brown sugar in a centrifuge was purged with water containing about 0.2 to about 0.5% by weight of the sucrose esters, sucrose ethers, or sucrose etheresters of the invention. The sugar was recovered in the usual manner.

Through the practice of the present invention it has been possible to achieve substantial improvements in commercial sugar producing operations. The products of the invention, when added to massecuites in sugar evaporators improve the physical properties of and thus decrease processing time and provide larger yields of crystals. The surfactants of the invention may be introduced at any of several stages of the overall process up to and including the crystal purging step. That is, the invention can be practiced by adding the sucrose derivatives during the boiling of the sugar liquor, during crystallization, during'the dumping or spinning of the massecuite, or during the crystal purging.

The concentration of sucrose surfactant required to achieve the advantages of the invention varies somewhat with the particular agent used and with the particular stage of the process during which the agent is introduced. In general, the preferred concentration is in the range of between about 0.01% and 1.0% of surfactant based on the concentration of sugar solids, and preferably in the range of from about 0.03% to about 0.5%. When added to the purge water, the preferred concentration is between about 0.1% to about 1%, in the water.

The sucrose derivatives may be advantageously incorporated at any one or several stages of the process, either in the raw vacuum pans, in the crystallizer, or in any of the other stages. As those familiar with the relevant art will recognize, the surfactants must be thoroughly and intimately mixed with *the syrup. Throughout the processing steps, from initial through intermediate pans, the surfactants go forward with the sugars, pass on to the raws, and then to the molasses.

A very important advantage of the unique surfactants of the present invention is their remarkable solubility in and special compatibility with the concentrated solutions in sugar processing systems. It is this property of the noval compositions of the invention that is believed to be principally responsible for their marked and unexpected superiority over the prior art surface active agents. In addition, the agents of the invention favorably affect the wetting properties of the solutions, reduce foam, lower the viscosity, improve the heat transfer, and reduce scale formation in processing equipment.

In the presence of sucrose surfactants of the invention sugar crystallization from solution is effected at an increased rate, and a drier and whiter product is formed. Over-all processing time is reduced and the time for growing a given quantity of crystals is significantly shortened. The final crystalline sugar product is of an improved quality, particularly in the soft or brown grades.

It will be understood by those skilled in the art that while this invention has been described in connection with specific details and specific embodiments, these details and embodiments are illustrative only and are not to be considered limitations since apparently widely different embodiments of this invention can be made without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a process for manufacturing crystalline sugar and including the step of preparing a syrup having a high concentration of sugar dissolved therein and the step of separating precipitated sugar crystals from said syrup, the improvement which comprises the step of introducing into said syrup prior to removal of said crystals therefrom a sucrose-derived viscosity modifier and crystallization aid consisting essentially of a surface active agent selected from the group consisting of sucrose esters, sucrose ethers, sucrose ether-esters, and mixtures thereof.

2. The process of claim 1 wherein the sucrose ethers are lauryl sucryl ethers.

3. The process of claim 1 where the sucrose etheresters are lauroyl esters of sucrose polypropoxy propanol.

4. The process of claim 1 wherein said Surface active agent is present at a concentration in the range of from about 0.01% to about 1% by weight based upon the weight of solids in said syrup.

5. The process of claim 1 wherein said surface active agent is present at a concentration in the range of from about 0.03 to about 0.5% by weight based upon the weight of solids in said syrup.

6. The process of claim 1 wherein the sucrose esters are fatty acid esters of sucrose.

7. The process of claim 6 wherein the fatty acid esters of sucrose are sucrose dioleates.

8. 'In a sugar refining and crystallization process the method of increasing the rate of crystallization of sugars and the overall yield of crystalline products, and concurrently improving the quality of the ultimate sugar crystals separated and recovered from concentrated sugar solution, said method comprising carrying out the sugar crystal separation in the presence of a sucrose-derived solution viscosity modifier and crystallization aid comprising a surface active agent selected from the group consisting of sucrose esters, sucrose ethers, sucrose etheresters, and mixtures thereof.

References Cited UNITED STATES PATENTS 2,591,704 4/1952 King 12758 2,759,922 8/1956 Gibbons 260--210 2,759,923 8/1956 Gibbons 260-210 2,871,148 1/1959 Kent 127-58 2,893,990 7/1959 Hass et al. 260209 X 2,908,681 10/1959 Anderson et a1.

2,927,919 3/1960 Anderson 260-209 2,974,134 3/1961 Pollitzer 260--209 3,018,281 1/1962 Crecelius 260-209 3,048,577 8/1962 Gaertner 260-209 3,061,478 10/1962 Kent 12716 X MORRIS O. WOLK, Primary Examiner D. G. CONLIN, Assistant Examiner U.S. Cl. X.R.