PROCEDURE FOR THE PRODUCTION OF BUTYLOLIGOGLYCOSIDEN.

-1- 23443-343 The invention relates to a method of preparing toutyloligoglycosides by acid-catalyzed reaction of saccharides with butanol at elevated temperatures. Butyloligoglycosides or mixtures of butylglycosides and butyloligoglycosides are interesting polyols that are available from carbohydrates. They are increasingly gaining importance as intermediates in the preparation of polyurethanes and surfactants based on long-chained alkylglycosides. Alkylglycosides with short-chained alkyl groups are generally prepared by the Fischer process. Thus, according to U.S. Patent 3,974,138, butylglucosides are obtained from glucose and butanol by heating at reflux with acid catalyst. Glucose must be used in crystalline form in this process. Less expensive aqueous glucose or dextrose syrups cannot be used since glucose separates from the reaction mixture in the form of viscous, tacky masses as soon as the water from the reaction is distilled off. A process for the preparation of alkyloligoglycosides from saccharides and monofunctional alcohols with 8 to 25 carbon atoms with acid catalysts is described in German OS 20 36 472. Glycols with 3 to 5 carbon atoms are used in this process in order to be able to use sugar syrups. The glycols function as solvents for both the alcohols and the sugars. Pure butylglycosides cannot be prepared by this procedure. The glycols have a higher boiling point than butanol and therefore cannot be distilled off during the reaction in the presence of the butanol. Glycolglycosides remain in the reaction product. O.Z. 4168 *£& -2- 23443-343 AlXylglycosides are prepared with acid catalyst from polysaccharides containing water and alcohols having 3 to carbon atoms according to European Patent 0 099 183. The reaction is carried out in the presence of cosolvents such as methanol, ethanol, ethylene glycol, or acetone, and under pressure, purification of the reaction product requires increased effort in the distillation and the product has a high content of unreacted glucose. Alkylglucoside mixtures are prepared from glucose and long-chained alcohols having 8 to 22 carbon atoms with acid catalyst according to European Patent 0 092 355. Compatibility of the starting materials is achieved with nonionic surfactants. Alkylglycosides having alkyl groups containing at least 8 carbon atoms, preferably with 10 to 14 carbon atoms, are used is the surfactants. Since mixtures of fatty alcohols are generally used in the preparation of surfactants of the alkyloligoglucoside type, the product quality is hardly affected at all by the use of a surfactant differing in the alkyl group. In the preparation of alkyloligoglycosides with a specific alkyl group having fewer than 8 carbon atoms, on the other hand, such a surfactant will contaminate the end product since fatty alcohols liberated by transacetalization in the presence of short-chained alcohols cannot be separated by distillation. Accordingly, it is attempted in the present invention to provide a simplified procedure for preparing butyloligoglycosides 1Î298719 _3- 23443-343 in which inexpensive aqueous saccharide syrups can be used as starting materials, without impairing the ease of handling of the reaction mixture due to inhomogeneities or by precipitation of quantities of tacky sugars. The present invention provides a process for the prepar¬ ation of butyloligoglycosides, comprising: reacting an aqueous saccharide syrup, a butyloligogly- coside and butanol at an elevated temperature in the presence of an acid, and removing water from the reaction mixture. Surprisingly, it has been found that butyloligoglyco¬ sides are prepared without the above-mentioned difficulties by reacting aqueous saccharide syrups with butanol at an elevated temperature in the presence of butyloligoglycosides, which are not considered to be surfactants, and removing the water from the reaction mixture, preferably by azeotropically distilling off during the reaction. Saccharide syrups based on hexoses such as glucose, mannose, galactose, sorbose, or fructose, or pentoses such as xylose, arabinose, ribose, or lyxose, and disaccharides such as lactose, maltose, or sucrose, and mixtures based on them, can be used for the reaction. Preferably, commercial starch hydrolyzates such as dextrose and glucose syrups or maltodextrine syrups are used. The products can also contain oligosaccharides. The DE value (dextrose value) should be above 20, however. The water content of the products is generally 20 to 40%. Products with a water content of 25 to 30% are preferably used. -4- 23443-343 In the reaction mixture, from 1 to 20 moles of butanol are used per mole saccharide unit of the saccheride syrups. At the same time, preferably 1 to 10 moles of butanol are present per mole saccharide unit of the butyloligoglycosides used. Among the butyloligoglycosides, which are previously prepared and are to be added to the reaction mixture, butyloligoglycosides having the same saccharide portion as the sacchardie in the syrup are preferred of course. When the saccharide in the syrup is glucose, butyloligoglycoside having an average degree of oligomerization up to about 6, particularly up to about 2 is preferred. Mineral acids, strong organic acids, or acidic ion exchangers are used as catalysts. Catalysis by sulfuric acid or p-toluenesulfonic acid is preferred. The catalysts are preferably used at concentrations of 0.01 to 1.0% based on the reaction mixture. The reaction is carried out at from about 80 to 130oC and the temperature is preferably 100 to 1200C. The rate of reaction is low at temperatures below 800C. The formation of byproducts is favored above 130"C, and the color of the products is impaired. The reaction can be carried out in a homogeneous solution by the addition of butyloligoglycosides. The necessary amounts of butyloligoglycosides depend essentially on the reaction temperature and the water content of the syrups. Thus, for -5- 23443-343 example, the following mixture becomes a -homogeneous solution at 100oC: wt.% butanol wt.% butylglucoside wt.% glucose syrup with 30% water 1296713 23443-343 Stirred flasks with a device for removing water can be used as reactors for batch operation. Stirred kettle cascades with which water can be removed by the use of water separators, and other types of equipment, are suitable for continuous operation. A batchwise procedure would be as follows. Butanol and butyloligoglycoside are first placed in a stirred flask. After adding acid as a catalyst, the mixture is heated to boiling, optionally under pressure or low vacuum, to adjust to a temperature of 80 to 130oC. Butanol, aqueous saccharide syrup, and more acid are then metered in. Water is separated at the same time with a water separator. The rate of addition of the reactants is such that butyloligoglycoside is present in the reaction mixture at a concentration that prevents inhomogeneities. At the end of the reaction, the mixture can be neutralized with an alkali and excess butanol can be distilled off. In a continuous method, butyloligoglycoside is first added to the reaction mixture, after which a concentration of at least 15% by weight is maintained in the mixture during the reaction and water is separated off. The butyloligoglycoside concentration is preferably at least 20%. The process has the following advantages: (1) Inexpensive aqueous saccharide syrups can be processed. (2) All of the components that are metered in during the process are liquid and easy to pump. (3) The reaction mixture remains homogeneous during the entire process. (4) The process can be carried out continuously in a stirred kettle cascade with water separators in a simple manner. (5) Addition of auxiliary substances which must to be removed later is unnecessary. Other features of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof. EXAMPLES Example 1 , A solution of 7.5 kg of butyloligoglucoside (average degree of oligomerization approximately 1.8), 7.5 kg of n-butanol, and 63 ml of 2 N sulfuric acid are distributed uniformly among the three flasks of a stirred kettle cascade consisting of three 8-liter stirred flasks equipped with distillation columns and water separators. The flasks are then heated so that the solution boils under reflux. 1728 g/hour of 70% aqueous dextrose syrup, 2240 g/hour of n-butanol, and 33.6 ml/hour of 2 N sulfuric acid are then metered into the first flask. The reaction temperature is maintained at from 115 to 120oC. Approximately 830 g/hour of water phase is removed through the water separators. 3190 g/hour of product solution is separated from the last flask. The filling levels of the flasks remain constant. The product solution consists of approximately 45% butyloligoglucoside and contains less than 1% unreacted glucose. After neutralization with 2 N sodium hydroxide solution, n-butanol is distilled off. A butyloligoglucoside with an average degree of oligomerization of approximately 1.8 is. isolated as a syrup. Example 2 100 g of butylglucoside, 108 g of 70% glucose syrup, and 62 g of n-butanol are heated to 110oC in a stirring apparatus with a distillation column and water separator. 2.4 ml of 2 N sulfuric acid is added. The mixture is then heated at the boiling point for 4 hours and water is removed. After neutralization with 2 N sodium hydroxide solution, the n»-butanol is removed by evaporation whereby butylglucoside is obtained as a syrup. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. -10- 23443-343