MXPA96006648A - Improved procedure of oxidation of losazuca - Google Patents

Abstract

The present invention relates to an improved process of alkaline oxidation and an aqueous medium of sugars possessing one or more primary alcohols functions by means of hypohalites and in the presence of a catalyst constituted by a binary or tertiary alkyl nitroxyl. The procedure is very interesting because the oxidation takes place in the presence of high concentrations of sugars. The products ined by this procedure, some new, can be used as "builders" in the compositions of lej

Description

IMPROVED PROCEDURE OF OXIDATION OF SUGARS The invention concerns a process of oxidation of sugars. More precisely, this invention concerns a process for oxidation of sugars by a hypohalite by means of a catalyst constituted by a binary or tertiary alkyl nitroxyl. It is known that sugars and, in general, their derivatives can be oxidized in an alkaline medium by means of hypohalites in the presence of a catalyst constituted by a binary or tertiary alkyl nitroxyl. This oxidation is translated by the appearance of carboxylic acid functions instead of primary alcohol functions and also the terminal hemiacetal function of small glucose polymers for example. Such a procedure has been described in the international patent application WO 95/07303. This procedure, which has been exemplified on methyl glucosides, on a disaccharide such as trehalose and on polysaccharides such as starch, inulin and pullulan, can also be applied to β-glucans such as cellulose, curdlan or scleroglucan and is also applicable to hydrolysates or derivatives of these sugars. By this process, the starch or the inulin or its hydrolysates can be oxidized to poly-a-glucuronic acids or poly-β-fructuronic acids. Therefore, an aqueous alkaline solution containing approximately 7 to 15 grams of dry matter per liter of water, to which is added an oxidation catalyst constituted by approximately 0.1 to 2.5% l-oxyl-2, 2 , 6, 6-tetramethylopiperidine (hereafter called TEMPO) and from 20% to 75% sodium bromide as a co-oxidant, these percentages being expressed in relation to sugar, is subjected to the action of the water of javel acting as an oxidant. This international patent application WO 95/07303 also demonstrates that, in order to be effective, such an oxidation reaction must be carried out at a temperature below 30 ° C and that it is particularly preferable to proceed with this oxidation at a temperature between 0 and 5 ° C. . Under these conditions, it is indicated that, for example, oxidized starches can be obtained with rates approaching the theoretical maximum, namely that the quasitotality of the anhydroglucosyl units of these polymers are converted into anhydroglucuronyl units. The hemiacetal terminal reducing ends of glucose or glucose oligomers are also oxidized into carboxylic acid functions thereby constituting a glucaric acid or glucuronyl-glucarate unless these ends are protected, for example, by methylation. According to the teaching of the patent application in question, this last oxidation relative to the unprotected reducing ends only concerns the starch or inulin hydrolysates of low molecular weight.

It was discovered and, what finally constitutes the basis of the present invention, that also high oxidation rates could be obtained, whatever the sugar to be oxidized, when aqueous solutions of sugars or their polymers containing more than 15 grams of sugar were used. sugar per liter of water. In the first instance, the present invention thus concerns an alkaline oxidation process and, in an aqueous medium, sugars possessing one or more primary alcohols functions by hypohalites and in the presence of a catalyst constituted by a binary or tertiary alkyl nitroxyl, characterized due to the fact that the sugar concentration of the aqueous medium is higher than 50 g / 1, preferably higher than 100 g / 1 and, optimally, higher than 200 g / 1 A solution of polyglucuronic acids is obtained in the case of the oxidation of polymers of glucose. In the case of the oxidation of aldoses monomers, thus the alderic acids corresponding to the monomer subjected to oxidation are obtained. The Applicant Society discovered that, unexpectedly, the complete oxidation of the sugars obtained by the oxidation catalyzed by a nitroxyl binary or tertiary alkyl, in an alkaline medium, by means of hypohalites, it could be guaranteed although the sugar concentration in the reaction medium was much higher than 15 g / 1. You can proceed to the oxidation of sugars with concentrations up to 500 g / 1, even more. The Applicant Society discovered that they are above all solubility or viscosity problems that limit the concentrations at which oxidations can proceed according to the process of the invention. For example, it is possible to proceed with the oxidation of substances of low molecular weight such as xylose, arabinose, glucose, fructose, mannitol, sorbitol, lactose, lactitol, maltitol, starch hydrolysates, ... at concentrations well above 100 g / 1. In addition, the Applicant Society observed that such oxidation could also be carried out at temperatures well above 30 ° C up to 60 ° C. These high temperatures allow the solubility limit of the sugars to be increased and the viscosity of their solutions to decrease, thus increasing their concentration. Thus it is possible to proceed, for example, at 40 ° C to the oxidation of solutions containing more than 200 g / 1 of mannitol, even though at a temperature of 0 ° C, the solubility limit thereof is considerably exceeded.

When it is desired to oxidize sugars of polymeric nature such as starch, inulin, cellulose, pectins, gums or their hydrolysates or products derived by esterification, etherification, cross-linking ... the concentration limit of the solutions to be oxidized will be limit of the pressures imposed by the viscosity of these solutions. However, this limit will be higher if the temperature of the reaction medium is higher. In the second instance, the process according to the invention is characterized in that the oxidation is carried out at a temperature above 30 ° C, preferably above 40 ° C. Since the oxidation rates as well as the selectivity of the oxidation with respect to the primary alcohols or hemiacetal functions remain essentially the same during the process of the invention as during the prior art process essentially represented by the patent application WO 95 / 07303, it is evident that the increase in the concentrations of the sugars to be oxidized according to the process of the present invention constitutes a considerable saving as far as the volume of the reactors necessary for carrying out the process of the invention is concerned. In addition, the fact of working at high temperatures makes it possible to avoid the use of very expensive refrigeration units. The heat that comes from these very exothermic oxidation reactions and whose degree depends on the concentration of the media, can be evacuated simply by water at room temperature. Finally, the Applicant Society observed that another advantage of high temperatures, in all cases equal to or greater than 30 ° C, was that the oxidation rates of sugars increased and that it was thus possible to decrease the catalyst rates, in particular the TEMPO rate. This considerable increase in the efficiency of the catalyst at high temperature means that, at least as regards the oxidation of the sugars of low molecular mass, it is possible to reduce very significantly even the expensive cocatalyst, namely the sodium bromide used in the procedure of the superior technique. The selectivity of the oxidation is only slightly affected and only signs of oxidation are observed concerning secondary alcohols. Conversely, this considerable increase in the efficiency of the catalyst allows, unlike what was taught in patent WO 95/07303, to also oxidise the hemiacetal ends of the polymers of glucose with polymerization degree higher than 15 and to suppress almost totally the reducing power of starch hydrolysates subjected to oxidation.

According to the Applicant Society, such products consisting of glucuronyl-glucarate containing less than 0.5 reducing sugars, do not exist. It will be understood that the term sugar (s) used in the present invention pertains to the -ostas, the -uloses, the alditols as well as all the derivative compounds such as the acids or poly-acids aldónicos, ketoaldónicos, urónicos, its derivatives acetylated, aminados , alkylated, carboxymethylated, cationized, ... and the homogeneous or heterogeneous polymers of these sugars, even though these sugars have at least one primary alcohol function. The process of the invention is, for example, very effective on starch hydrolysates and starch hydrolysates hydrogenated or oxidized by other processes, and the products that can be obtained have very interesting yields in the bleach compositions because of their complexing properties conferred by the numerous carboxylic functions that they present. Other oxidizable materials, usable in the process of this invention, can also be constituted by primary alcohols with hydrocarbon chain such as methanol, ethanol, propanol, ... since these are soluble in water at preferred temperatures of the process of the invention .

To carry out the process of the invention, the sugar is dissolved in the water to obtain a concentration of at least 50 g / 1.

It is essential in the process of the invention that the oxidation takes place in an alkaline medium. To carry out the oxidation reaction of the process of the invention, the preferred pH is between about 9 to about 13. The appearance of acid functions according to the evolution of the oxidation reaction obliges, of course, to introduce an alkali continuously in the reaction medium in order to maintain this pH. The patent US-A-5334756 concerns a process for the preparation of carboxylates, in particular of alkyl polyglucosides, consisting of subjecting an alkyl polyglycoside containing primary hydroxy groups to moderate oxidation but in slightly alkaline medium because the pH is between 8.0 and 9.0 and , preferably, between 8.5 and 9.0. According to the process of the invention, the oxidation is carried out in the presence of a catalyst constituted by a binary or tertiary alkyl nitroxyl capable of releasing a nitrosonium cation which is reduced in hydroxylamine when a primary alcohol function is oxidized in carboxylic acid. This nitrosonium cation is regenerated in situ by an oxidant easily constituted by a hypochlorite. According to a preferred embodiment of the invention, the catalyst is constituted by l-oxyl-2, 2, 6,6-tetramethylopiperidine or TEMPO and the hypochlorite is the water of javelin.

The catalyst is added to the water before or after adding the sugar. The concentration of the catalyst must be at least 0.01% in relation to the weight of the sugar. It may be lower when working at high temperature. However, it is preferred to use TEMPO concentrations between 0.05% and 1.5%. The catalyst concentration increases the more the reaction time decreases. Of course, the inverse is valid. The reaction temperature according to the process of the invention is at least 30 ° C. Oxidation products of excellent quality that only contain a few percentages of oxidations concerning the secondary alcohols, are obtained at temperatures of up to approximately 60 ° C, even slightly higher. These non-selective oxidations grow according to the increase in temperature. The duration required for the oxidation depends both on the temperature, on the pH and on the percentage of the catalyst. Unexpectedly, the sugar concentration of the reaction medium is not very important. In general, the desired oxidation rates that can be between 10% and 100% and, more generally, between 60 and 99% of the primary alcohol functions to be oxidized are obtained between 1 minute and 2 hours approximately, although Depending on the circumstances and the equipment of the oxidation reactors (agitation, dimension of the heat exchangers), it is possible to proceed with the oxidations for a longer time. Thus, the duration required for oxidation is considerably shorter than that indicated in US-A-5334756. When, for example, low catalyst rates or lower temperatures are used, a longer oxidation duration can be carried out. More or less heavy polymers that present primary alcohols functions can be used in the process of the invention. However, the Applicant Society observed that in order to proceed with the oxidation of sugars of relatively low molecular mass, such as, for example, monomers, dimers and polymers of simple sugars with a degree of polymerization of less than about 20, it was not necessary to use a co-oxidant. . This goes against the prior art teaching. An alkaline oxidation process of monomers, dimers and polymers of simple sugars with a degree of polymerization of less than about 20 according to the invention consists in only using the water of javel without adding expensive co-oxidant such as sodium bromide. The oxidation of maltitol which is a dimer, composed of glucose and sorbitol bound in a, 1-4 is, for example, possible by the single action of the water of javel without adding bromide.

Thus, glucuronyl (a, 1-4) glucaric acid, which is a new product and has very interesting sequestering properties, is obtained with a total yield. The oxidation of maltitol may be carried out, for example, according to the process of the invention at a temperature of 40 ° C with a TEMPO rate of 1.3% and a maltitol concentration of the syrup subjected to oxidation of 25% without bromide. Generally, to obtain the oxidation of all the primary alcohol functions of a sugar, it is preferred to use a slight excess of oxidant be approximately 2.2 moles of NaOCl per mole of primary alcohol to be oxidized, eg, 6.6 moles of NaOCl per mole of maltitol to be oxidized because maltitol has three primary alcohol functions. However, the Applicant observed that glucose syrups or maltodextrins with a GP greater than 2 could be almost completely oxidized without adding cocatalysts for a short time that they were oxidized at a temperature higher than 30 ° C. The process of the present invention has at least four advantages in relation to the process proposed in the patent application WO 95/07303, in which the oxidation of the sugars is carried out in very dilute and very cold medium. First the catalyst rates can be reduced as stated above.

Second is not necessary at least when proceeding to the oxidation of products with low molecular mass, use cocatalysts. Third, it is not necessary to use refrigeration units. Fourth, it is not necessary to evaporate huge amounts of water to recover the products obtained by the process of the present invention. In the process of the present invention, it is preferred to proceed to the progressive addition of alkali in reaction medium in order to keep the pH of this medium constant. It would be possible to introduce in a single time, at the beginning of the reaction, the total quantity of alkali that is considered necessary for the realization of it. The sugar and the oxidant or the oxidant-cooxidant mixture can be introduced continuously into the reactor, however it is preferred to completely dissolve them in the water from the beginning of the reaction. When the oxidation reaction is complete or when it reaches the determined threshold which depends on the relative amount of oxidant carried out, the stoppage of the alkali consumption or the stabilization of the pH is observed if all the alkali was introduced in a single time at the beginning of the reaction. The catalyst can be extracted from the reaction medium by, for example, extraction using a solvent; It is also possible in a more practical way to adsorb onto a column of granular activated carbon.

After filtration, the reaction medium without its catalyst and without carbon residues can be treated by ion exclusion chromatography or by means of membranes in order to remove the mineral salts. If the case arises, these reactionary means thus purified can be concentrated and dried. It can also be subjected to a crystallization to isolate pure products when pure sugars have been subjected to oxidation. Other details of the invention will appear on reading the examples given below. In these examples, the concentrations in sugars are given in percentage by weight of sugars in relation to the weight of sugar solutions made, the percentages of catalysts are given by weight in relation to the weight of dry sugars made. Example 1; In a stirred and thermally regulated reactor, equipped with a pH measurement probe, an aqueous solution is prepared at 50% by weight of sorbitol by the addition of 100 grams of sorbitol to 100 ml of demineralized water. This solution is brought to 45 ° C and, subsequently, 0.8 g of TEMPO and 1.15 1 of javeline water are added to 48 ° C chlorometric in the form of a solution previously diluted to 10% and adjusted to a pH of 10.4 by the acid hydrochloric.

The reaction is allowed to develop at a temperature of 45 ° by circulating water at 20 ° C in the double jacket of the reactor and continuously adding a 10% soda solution in order to maintain the pH at 10.4. After 20 minutes, it is observed that the consumption of soda is almost negative. The content of the reactor is percolated on a column of granular activated carbon and then this column is isolated with water in order to extract the catalyst. The analysis of the obtained product shows that the mixture contains in relation to the dry matter: - 33% of glucaric acid in the form of its sodium salt, - 67% of sodium chloride. No products of superoxidation of glucaric acid are detected. Example 2; In the same reactor, an aqueous solution is prepared at 25% by weight of mannitol by the addition of 100 grams of mannitol to 300 ml of demineralized water. This solution is brought to 55 ° C and, subsequently, 1 g of TEMPO and 1.15 1 of javeline water are added at 48 ° C chlorometric in the form of a solution previously diluted to 25% and adjusted to a pH of 10.6 by the acid hydrochloric.

The reaction is allowed to develop at 55 ° C by circulating water at 20 ° C in the double jacket of the reactor and continuously adding a 10% soda solution in order to maintain the pH at 10.6. After 30 minutes, it is observed that the consumption of soda is almost negative. The content of the reactor is percolated on a column of granular activated carbon in order to extract the catalyst and then this column is isolated with water. 7 liters of solution are recovered containing: - 1.9% manic acid in the form of its sodium salt, - 4.1% sodium chloride. Indications of superoxidation products of manic acid are detected. Example 3; In the same reactor, an aqueous solution at 50% by weight of maltitol is prepared by the addition of 100 grams of maltitol to 100 ml of demineralized water. This solution is brought to 35 ° C and, subsequently, 0.3 g of TEMPO and 0.9 1 of javeline water are added at 48 ° C chlorometric in the form of a solution previously diluted to 10% and adjusted to a pH of 10.4 by the acid hydrochloric.

The reaction is allowed to develop at a temperature of 45 ° by circulating water at 20 ° C in the double jacket of the reactor and continuously adding a soda solution to 25% in order to maintain the pH at 10.4. After 40 minutes, it is observed that the consumption of soda is almost negative. The content of the reactor is percolated on a column of granular activated carbon in order to extract the catalyst and then this column is isolated with water. The analysis of the product obtained shows that the mixture contains: - 37% glucuronyl-glucaric acid in the form of its sodium salt, - 63% sodium chloride. No super-oxidation products of glucuronyl-glucaric acid are detected. The salt present in the crude reaction product was removed by an ion exclusion chromatographic technique on a strong cationic resin. Thus, a product consisting of 4% sodium chloride was obtained. The complexing power of glucuronyl-glucuric acid thus purified was measured thanks to a potentiometer provided with a calcium electrode and a value of 16 mg of complex calcium was measured by one gram of glucuronyl-glucaric acid in the form of its sodium salt; This product presents excellent performance as builder intervening in the formulation of bleach compositions. Example 4: In the same reactor, an aqueous solution is prepared at 20% GLUCIDEXR 19 corresponding to 100 grams of dry matter. This product is a maltodextrin marketed by the Applicant, which is obtained by hydrolysis to the α-amylase of the starch. This solution is brought to 35 ° C and, subsequently, 1 g of TEMPO and 0.75 1 of javeline water are added at 48 ° C chlorometric in the form of a solution previously diluted to 50% and adjusted to pH 10.3 by the acid hydrochloric. The reaction is allowed to develop at a temperature of 35 ° by continuously adding a 10% soda solution in order to maintain the pH at 10.3. After 120 minutes, it is observed that the consumption of soda is almost negative. The content of the reactor is percolated on a column of granular activated carbon, and then this column is isolated with water. The analysis of the product obtained shows that the mixture contains: - 45% of glucaric acid, glucuronyl-glucaric acid and polyglucuronyl-glucaric acid in the form of its sodium salts, - 55% of sodium chloride. It has an average degree of polymerization of about 5 and its content of free reducing sugars, measured by the BERTRAND method is 0.3%, indicating that, under the particular conditions of the process of the invention, even the hemiacetal functions of the glucose polymers with a degree of polymerization greater than 20, they are oxidized in spite of the absence of cooxidant. Example 5; In a fermentation apparatus equipped with BIOLAFITTE brand glass tub, with a useful capacity of 20 liters, 2995 grams of water and 1591 grams of soda are introduced to form 4586 grams of a soda lye at 34.7%. In this lye 55 grams of anthraquinone-2-monosulfonate of sodium and 18.2 ml of hydrogen peroxide are added to 110 volumes. The fermentation apparatus is ventilated with an air flow rate of 20 liters per minute by stirring at a rate of 1000 revolutions per minute. After having stirred this mixture at 25 ° C for 30 minutes, the temperature is raised to 45 ° C. A total of 18,344 grams of a glucose syrup obtained by acid hydrolysis of corn starch are added progressively and regularly in 3 hours and 30 30 minutes, presenting a dry matter of 50% and a GE of 37 (a mean degree of polymerization equal to 2.7). ). The temperature is then set at 55 ° C and agitation and ventilation are continued for 2 hours and 30 minutes. The content of reducing sugars in the reaction medium is reduced to 0.3 / 100g of dry matter of glucose syrup.

(Initially it was 37 g / lOOg). After having rectified the pH of this reaction medium to 7, it is percolated on a column of granular activated carbon in order to extract the sodium salt of the antaquinone-2-monosulfonic acid. This oxidative alkaline degradation reaction transforms the glucose syrup composed of polyglucosyl-glucose into polyglucosyl-arabinonate. In a stirred and thermally regulated reactor, all of this polyglycosyl arabinonate syrup is introduced without diluting it. Due to the slight dilution following the elimination of the sodium salt of the acid-2-anthraquinone monosulfonic acid, the sugary dry matter of this syrup rises to approximately 38%. This syrup is brought to the temperature of 45 ° C and, subsequently, 50 g of TEMPO and 58 1 of javeline water are added to 48 ° C chlorometric in the form of a solution previously diluted to 25% and adjusted to a pH of 10.4 . The reaction is allowed to develop at a temperature of 45 ° by circulating water at 20 ° C in the double jacket of the reactor and continuously adding a 10% solution of SBS in order to maintain the pH at 10.4. After 90 minutes, it is observed that the consumption of soda is almost negative. The content of the reactor is percolated on a column of granular activated carbon in order to extract the catalyst and subsequently this column is isolated with water. The quasitotality of the mineral salts present in this solution is extracted by means of an ion exclusion technique using strong cationic resins. The product obtained has been concentrated under vacuum and then dehydrated by atomization. It provides a white powder of glucuronil-arabinaratos. This powder was used in replacement of the polyacrylates in a bleach formula at the rate of 1 part of glucuronil-arabinarates thus enriched by a part of polyacrylates. Not only do the powders obtained not color during storage but also present very interesting bleach qualities because after having made 25 consecutive washings of samples of cotton and cotton / polyester fabrics, the bleaching rates are higher than the polyacrylate control. In addition, the rate of organic inlays is significantly lower.

Claims (7)

1. CLAIMS 1. Process of alkaline oxidation at a pH between 9 to 13 approximately, of sugars possessing one or more primary alcohols functions by means of hypohalites and in the presence of a catalyst constituted by a binary or tertiary alkyl nitroxyl, characterized by the fact that the sugar concentration of the aqueous medium is greater than 50 g / 1, preferably higher than 100 g / 1 and, optimally, higher than 200 g / 1
2. 2. Alkaline oxidation process for sugars according to claim 1, characterized in that the oxidation be brought to a temperature above 30 ° C, preferably above 40 ° C.
3. 3. Procedure for alkaline oxidation of sugars according to claims 1 and 2, characterized in that the catalyst is l-oxy-2, 2,6,6-tetramethylpiperidine.
4. 4. Method of alkaline oxidation of monomers, dimers, trimers and tetramers of simple sugars according to any of claims 1 to 3, characterized in that the hypohalite is sodium hypochlorite and because it is used without cooxidant, in particular without sodium bromide.
5. 5. Glucuronyl (a, 1-4) glucaric acid.
6. 6. Glucuronil-glucarate containing less than 0.5% reducing sugars.
7. 7. Use of the products obtained by the process according to claims 1 to 4 in the bleach compositions.