MXPA01006678A - Process for the preparation of a non-crystallizing polyol syrup - Google Patents

Abstract

Preparation of anon-crystallizable polymer syrup comprises hydrogenating a sugar syrup, caramelizing and purifying using a cationic ion exchange resin strong at below 50 degrees C, giving stability to heat and alkali. Preparation of A non-crystallizable polymer syrup comprises hydrogenating a sugar syrup, caramelizing and purifying involving at least one pass over a cationic ion exchange resin strong at below 50 degrees C. An Independent claim is included for a dental paste containing the polyol syrup.

Description

METHOD FOR PREPARING A NON CRYSTALLIZABLE POLYOL SYRUP The subject of the invention is a new method for preparing a non-crystallizable polyol, stable to heat and alkali. A new method for preparing a polyol syrup capable of being used in the manufacture of liquors, detergents, in the formulation of pharmaceutical syrups, of toothpaste, ie, in all the application requiring a resistance, is also more precisely referred to. in an alkaline medium and / or in heat against the formation of undesirable colorations or of compounds that are unsuitable from the point of view of their taste. Polyols are understood as the products obtained by the catalytic hydrogenation of simple reducing sugars, of complex reducing sugars such as disaccharides, oligosaccharides and polysaccharides, as well as their mixtures, which will be designated later by the term "sugar syrup". In general, the simple reducing sugars which are intended for the catalytic hydrogenation according to the invention are glucose, xylose, fructose and mannose. The polyols obtained are then sorbitol, xylitol and mannitol. The disaccharides are most often maltose, isomaltulose, maltulose, isomaltose and lactose, which lead by catalytic hydrogenation, to maltilol, isomalt, isomaltitol and lactitol. By non-crystallizable composition, it is understood in the present invention the mixtures of polyols that form the non-crystallizable syrups at 20 ° C and a dry matter of 70% when stored in an airtight container for one month. By way of indication, the definition of a non-crystallisable sorbitol syrup within the meaning of the invention is in accordance with the European Pharmacopoeia, 1997, paragraph 0437. Sorbitol syrups are widely used in the agri-food, pharmaceutical and chemical domains. In the formulation of toothpastes and in particular in the manufacture of toothpastes with sodium bicarbonate, the use of sorbitol syrups as a humectant is not possible since the latter is stable in the presence of sodium bicarbonate, and does not generate brown coloring in storage. Indeed, this coloration appeared by the reaction of bicarbonate on the reducing sugars: glucose, maltose, oligo and polysaccharides. The intensity of coloration increases with the number of polysaccharide units, so a maltose molecule will generate more coloration than a dextrose molecule. The coloring is also strongly accelerated by the temperature at which the syrup is exposed. Indeed, we have remarked that the same intensity of coloration is then obtained from a storage of 10 days at 45 ° C and a storage of 15 months at 20 ° C. It is preferred that the syrups are non-crystallizable, in order to facilitate their handling and transport whatever the climatic conditions and ensure the stability in the times of finished products prepared from such syrups. Maltitol syrups also represent an important class, and are mainly used to prepare food and pharmaceutical products with cariogens. Xylitol syrups, although very expensive, have an important development due to their high sugar content, their dental properties and their excellent moisturizing characteristics. It is known that the coloration of a syrup of polyols in the presence of alkalis joins the presence of free, reducing sugars: glucose, maltose, oligo and polysaccharides. The improvement of the stability of such syrups thus passes through the elimination of these free sugars. Several means have already been contemplated in the laboratory scale. Japanese patent JP 51.86406 offers the prospects for improving the purity of crystallizable sorbitol syrups by bringing into play a reduction of crystallized glucose under alkalinity maintained throughout the reduction reaction, in order to obtain sorbitol of high purity poor in sugars not reduced. Nevertheless, this technique remains devoid of practical interest in the industrial scale because it needs to put a feeding, control and regulation device onerous, and the constant addition of buffer and alkaline solution during the reaction penalizes the subsequent purification stage. This method is on the other hand relatively contaminated taking into account important quantities of reagents used. Furthermore, nothing is said about the stability of the sorbitol syrups that result from said method. Japanese patent JP 41.12212 mentions a method of preparing sorbitol of maximum purity resistant to heat and alkalis, consisting of a reduction by addition of hydrogen at high pressure, that is, preventing the regulation of the solution at pH 8 to 10 just before that the reduction reaction is not achieved, that is to say having a temperature of 60 to 90 ° C, the sorbitol solution reduced and previously regulated to pH 8 to 10 in an alkali medium, after the decomposition of residual direct reducing sugars, in a separation by filtration with or without neutralization by an acid and with or without discoloration on carbon, then in a purification on ion exchange resin. This procedure, which is applied to a crystallisable sorbitol solution, instead provides a significant impurity formation because the reducing sugars undergo a relatively long treatment time of the order of five hours, and thus does not lead to a stability judged sufficient . Japanese patents JP 63.79844 and JP 7.145090 disclose a method of preparing heat and alkali-stable polyols, consisting of treating an aqueous polyol solution purified a first time by treatment in the first two hours in heat and alkaline medium. Then, on ion exchange resin, then purify again the solution obtained at 50 ° C, to pass on ion exchange resin. This method is particularly directed to crystallisable sorbitol syrups, obtained from high purity glucose syrups. Or of such crystallizable syrups do not adapt to a use notably in toothpastes because of numerous disadvantages they present. On the other hand, this method is particularly complex due to the multiple operations of which it is constituted, and thus hardly applicable to the industrial scale. The patent EP 0 71 1743, of which the plaintiff is the owner, describes the compositions of polyols which have a high chemical stability in an alkaline medium and a very weak reactivity. These compositions, particularly adapted for use in basic medium that require an absence of coloration, are obtained by catalytic hydrogenation of simple or complex reducing sugars, then by stabilization and purification of stabilized syrup. The stabilization step consists of subjecting the sorbitol syrups obtained by hydrogenation to oxidation, caramelization or fermentation, in order to arrange the syrups at an optical density less than or equal to 0.100 in an S-test. The plaintiff had a demonstrated effect that a satisfactory stability can not be reached with weak values in this test, reflecting the aptitude of the compositions to the coloration in alkaline medium. Seeking how to improve the performance of such a procedure, and in the desire to limit mineral and organic rejections to preserve the environment, the plaintiff has then put in place, after a long search, a new method that allows both to obtain non-crystallizable polyol syrups sufficiently stable in an alkaline medium and offering comfort by limiting purification operations with a high yield and minor contamination, which does not make it possible to obtain the conventional techniques known from the prior art. Thus, the plaintiff has found that it suits him, in order to obtain the non-crystallizable polyols stable to heat and alkalis, subjecting a syrup of sugars that has undergone a stage of hydrogenation and caramelization, to a purification step on at least one strong cationic resin at a temperature lower than 50 ° C said temperature being selected as a function of the rate of reducing sugars desired in the final composition. The object of the invention is therefore a new method for preparing a non-crystallizable polyol stable to heat and in an alkaline medium, comprising a step of hydrogenation of a sugar syrup and a stage of caramelization of hydrogenated sugar syrup, characterized in that the hydrogenated sugar syrup underwent a purification on heat exchange resins, said purification comprising at least one step on strong cationic resin at a temperature lower than 50 ° C said temperature being selected as a function of the rate of reducing sugars desired in the non-polyol syrup crystallizable. The plaintiff has indeed demonstrated after numerous works, the importance of working temperature over the maintenance of product quality when purifying on strong cationic resin. Indeed, the quality of the composition after the purification and in particular its final reducing sugar ratio is inversely proportional to the passage temperature over the strong cationic resin.

The purification on the strong cationic resin according to the invention is then conducted at a temperature below 50 ° C, chosen as a function of the rate of reducing sugars desired in the final composition after purification. In fact, the plaintiff found that it is possible to regulate the flow temperature on the resin as a function of part of the rate of reducing sugars reached after the caramelization and of another part of the final reducing sugar content desired for the polyol syrup. purified. This searched content varies depending on the applications aspirated for ef syrup. For the preparation of toothpastes, in addition to the nature of the alkaline agent present in the paste, the nature of the colorants used to determine the acceptable limit of coloring resistance for the polyol syrup is notably taken into account. In effect, a light yellow coloration will be more easily admitted for the legs colored in blue. The aromas used are also a factor to be taken into account to determine the limit of the acceptable sugar reduction rate. Thus, for certain pastes with bicarbonates, the acceptable limit is 350 parts of a million reducing sugars (squeezed in dextrose equivalent and designated later by ppm), and for others as cells containing pyrophosphates, the rates have up to 500 ppm They can agree. This is equally applicable for other pharmaceutical, cosmetic or food applications. Under the optimum conditions for conducting a hydrogenation after a caramelization of a non-crystallizable polyol syrup, the minimum values of reducing sugars of the order of 50 to 100 pp are obtained. Under these conditions, the plaintiff has found that the maximum temperature at which such syrup can be purified on strong cationic resin is 50 ° C, in order to finally obtain, taking into account the increase in the rate of reductive sugars in the resins , a value less than or equal to 500 ppm of reducing sugars considered as the maximum acceptable limit. From this side of 50 ° C, it is thus possible to regulate the temperature of passage over the resin as a function of the rate of reducing sugars desired in the final composition and of the rate of reducing sugars initially present after the caramelization. It is thus that the passage over strong cationic resin can be advantageously regulated at a temperature less than or equal to 40 ° C, preferably less than or equal to 30 ° C and more preferably still comprises between 20 and 30 ° C if a very weak rate is sought of reducing sugars in the polyol compositions according to the invention. The purification in itself is carried out according to current practices, that is to say that firstly a step is carried out on strong cationic resin on strong anionic resin, then on a mixed bed which is a split mixture of these two resins. It is also possible to modify the order of combination of these resins. The strong cationic resin has the purpose of eliminating the cations such as notably the sodium contributed by the sodium hydroxide used when the caramelization, and the soluble nickel provided by the hydrogenation catalyst. The strong anionic resin is intended to eliminate organic anions such as notably gluconate, which is a degradation product from the caramelization stage. The use in the last stage of mixed bed allows to optimize the purification the possible exits of ions that could take place when the preceding stages. It is preferred to use as the cation exchanger a strong cationic resin carrying a sulfonic functional group SO 3 H used in the form of a strong acid, such as, for example, the IR resin 200 C marketed by ROHM and HAAS. As for the anionic resin, it is preferred to use a strong anionic resin such as IRA 910 resin, marketed by the same manufacturer. The mixed bed will consist of a mixture of two resins. According to an advantageous embodiment of the method according to the invention, purification is carried out on resins at a capacity corresponding to 1.5 times the volume of the resin column crossed by the syrup per hour, in order to avoid too long residence times in the resin that risk promoting quality degradation of the purified polyol syrup. According to another advantageous embodiment of the method according to the invention, the caramelization is conducted in the hydrogenation reactor, under hydrogen and without catalyst separation, by introduction of an alkaline agent at the end of the hydrogenation reaction, at a time or the pH is likely to be stable after adding this alkaline agent without resorting to a buffer. The plaintiff has indeed found after numerous works that the hydrogenation step can advantageously be combined in a caramelization in the same reactor, without adding a buffer, in order to obtain a polyol composition in an economical and low-polluting manner after purification. stable in an alkaline medium and heat from a syrup of sugars. Caramelization in the sense of the present invention means an alkaline degradation of reducing sugars of the hydrogenate, which leads to the formation of corresponding enols. Among the alkaline alkalis that agree well with caramelization, strong or weak bases can be cited. According to a preferred embodiment, the alkaline agent used for caramelization is sodium hydroxide. The sugar syrup subjected to a process according to the invention can consist notably of glucose syrups, fructose, in glucose syrups rich in maltose, or still in xylose syrups. Advantageously, the sugar syrup is constituted by 60 to 95% of dextrose, 0.1 to 20% of maltose, the complement to 100 constituting poly and oligosaccharides, these percentages expressed by weight in comparison with the dry weights of the saccharides contained in said syrup. The catalytic hydrogenation is carried out in a manner known per se, in a reactor with double envelope, on the nickel catalysts of Raney, any other catalyst for hydrogenation of sugars may agree. Preferably, it is carried out at a hydrogen pressure between and 100 bars, at a temperature between 120 and 150 ° C, and still more preferably at a temperature between 130 and 150 ° C, this in order to optimize the hydrogenation rate by limiting the side reactions. The sodium hydroxide is introduced into the reactor so as to obtain a pH between 9 and 11, preferably between 9.5 and 11, at a time when it is sufficiently stable so as not to resort to a buffer solution or to avoid having to add a massive amount of sodium hydroxide in order to maintain the pH at that value. This state is generally reached at the end of 1 hour 30 of hydrogenation, under the conditions according to the invention. This criterion for the introduction of sodium hydroxide results in the study of hydrogenation kinetics and caramelization conditions. When the reaction medium is still rich in free reducing sugars, the introduction of the alkaline agent prepares a pH stability which drops appreciably due to the conversion of these free reducing sugars into corresponding acids. Thus, beyond an ambient reducing sugar content of 0.4%, too much acid formation is observed and thus a drop in pH renders the stabilization action of the caramelization inefficient and involves too much addition of sodium hydroxide. It is thus preferred to introduce the alkaline agent when the content of residual reducing sugars is less than 0.2%, and more preferably still less than or equal to 0.1%. When the pH in the reactor is less than 9, the caramelization is insufficient. When that is greater than 11, the caramelization is satisfactory but the ionic charge of the hydrogenate becomes too important which prepares a consequent rejection of chlorides when the regeneration of cation exchange resins. At a pH between 9.5 and 11, the plaintiff has ascertained that the excess of sodium hydroxide in the reaction medium is sufficient to ensure a complete caramelization of sugars. The process according to the invention makes it possible to obtain the polyol syrups particularly adapted to the invention in the preparation of basic pH products such as, notably, toothpastes based on sodium bicarbonate or the family of sodium phosphates, antacid compositions, shaving foams, epilating creams, or for the manufacture of products at high temperature, all attending to an unequaled profitability until now, and a minimum level of organic and mineral rejection. According to a method of the advantageous embodiment of the method according to the invention, the syrup obtained is a non-crystallizing sorbitol syrup. Preferably, the non-crystallizable sorbitol syrup obtained has a sorbitol content of at least 64% by weight, a maltitol content of at least 6% by weight, the content of oligo and polysaccharides constitutes the complement to 100%, these percentages being expressed in comparison with the dry matter of polyols present in the composition. The syrup that can be obtained according to the method according to the invention can thus be used advantageously in the preparation of products with basic pH, which contains the alkaline agents, or treated or obtained at high temperature.

The subject of the invention is also a toothpaste composition containing the polyol syrup which can be obtained according to the method according to the invention. The invention will be illustrated with the help of the following examples and which is provided by way of non-limiting. Example 1 In a double-walled reactor with a capacity of 20 liters, which contains Raney nickel in suspension, a syrup of sugars is introduced under agitation whose composition is as follows: - dextrose: 75% / sec - maltose: 8% / sec - maltotriose: 3.6% / sec - higher DP: 13.4% / sec The dry matter of the reaction medium is 40% by weight, and the Raney nickel content is 5% by weight, expressed in comparison with the dry weight. The hydrogenation is conducted for 1 h 30 at a pressure of 50 bars and at a temperature of 140 ° C. A solution of sodium hydroxide in 3% by weight is then introduced for 15 minutes in order to fix the pH of the hydrogenate to a value of 10.8. It is found that the pH is stable, the content of reducing sugars being less than 0.4% by weight. Hydrogenation is continued for 20 minutes. After the stirring of the reactor is stopped, it is allowed to decant for 15 minutes and the supernatant is emptied into a decanter in order to recover the catalyst. The supernatant of the decanter is filtered immediately in order to remove the last traces of catalyst. The syrup thus obtained is subjected, after cooling to 25 ° C, to a purification on strong cationic resin then on anionic resin, then on a mixed bed. The syrup obtained is then subjected to a stability test on the alkaline agents. This test, entitled test S, is described in patent EP 71 1743 whose claimant is the owner. The stability of the polyol compositions is so much more important than the value obtained in this test S is base (optical density less than 0.1). In 5 ml of syrup, 500 mg of ultra pure quality sodium hydrogencarbonate, and 250 mg of an aqueous solution in 20% ammonia are added. The mixture is mixed and heated for 2 hours in a water bath at 100 ° C without stirring. The solution is cooled to 20 ° C and the optical density thereof is measured at a wavelength of 420 nm, with the aid of a spectrometer such as that marketed by PERKIN-ELMER under the Lambda 5 UV / VIS Spectrometer brand. In the same way, a range of contrast is made by replacing the 5 ml of syrup with 3 ml of pure water and 2 ml of solutions of pure glucose anhydrous, concentration 100, 200, 300, 400, 500, 600 and 1000 parts per million. These solutions of glucose have by absorbency respectively: 0.04, 0.08, 0.120, 0.160, 0.205, 0.413.

An optimum base density of 0.04 is obtained for the syrup obtained according to the present invention. This is equivalent to a glucose dosage of 100 parts per million on dry, which is a value indicative of a very large stability to alkalines. The method according to the invention thus makes it possible to obtain a non-crystallizable polyol composition in a more economical and less polluting manner than the prior art techniques, very stable in an alkaline and / or heat medium. Example 2: Influence of temperature on the purification in motion of the ion exchange resins. The syrup obtained according to Example 1 is recovered before purification, which is divided into seven fractions. These fractions are purified on strong cationic resin, respectively at 20, 30, 35, 40, 45, 50, 52 and 60 ° C (fractions identified from A to H), then on anionic resin and finally on a mixed bed. An S test is carried out on each fraction after purification and the difference with the initial test is calculated for each point (S delta test). The results are provided in parts per million equivalent dextrose.

These results clearly demonstrate the influence of working temperature when purification on strong cationic resin. It is thus shown that it is possible to adapt the temperature of the composition when its purification, according to the requirements in terms of reducing sugars that the final application requires, which provides the method according to the invention with a flexibility that has hitherto not existed. Example 3: formulation of a toothpaste with sodium bicarbonate A toothpaste with sodium bicarbonate is made with the products A and F of example 2 (purified on resin at 20 ° C and at 50 ° C) according to the following formula: PART A PART B (% by weight) Syrup A 45.00 Syrup F 45.00 Sodium bicarbonate 10.00 10.00 Abrasive silica Tixosil 9.00 9.00 73 Abrasive silica Tixosil 10.00 10.00 43 Sodium lauryl sulfate 5.66 5.66 (aqueous solution at 30%) Monofluorophosphate 0.80 0.80 sodium Carboxymethylcellulose 0.70 0.70 sodium Titanium dioxide 0.70 0.70 Peppermint aroma 1.00 1 .00 Purified water qs 100.00 Id Sodium saccharinate 0.2 0.2 The toothpastes A and B, as obtained, respectively have a pH of 8.4 and 8.7, in a 10% solution. After storage for six months at room temperature, the color of the toothpaste A did not evolve due to the satisfactory purity of the product A. The paste B presents on the contrary an unacceptable yellowish color after the same storage times. Example 4: Formulation of anti-tartar toothpastes with sodium pyrophosphate. An anti-tartar toothpaste is made with sodium pyrophosphate as anti-tartar agent, and product D of example 2 (purified on strong cationic resin at 40 ° C), according to the following formula: Syrup D 45.00 Sodium pyrophosphate 4.00 Abrasive silica TIXOSIL 73 9.00 Silica thickener TiXOSIL 43 1 1 .00 Sodium saccharinate 0.20 Methyl parahydroxybenzoate 0.18 Propyl parahydroxybenzoate 0.02 Titanium dioxide 0.70 Sodium carboxymethylcellulose 0.70 Sodium monofluorophosphate 0.76 Sodium lauryl sulfate 5.66 (aqueous sol at 30%) Mint aroma 1 .00 Purified water qsp 100.00 The final pH of the toothpaste is 7.8 such as and 8.6 after dilution in 10%. After storage of the toothpaste for six months at room temperature, modifications of its color do not appear. The syrup B of Example 2 is thus completely adapted to a use in a toothpaste in the presence of the anti-tartar agent.

Claims (7)

1. CLAIMS 1. A method for preparing a non-crystallizable polyol, stable to heat and in an alkaline medium, comprising a step of hydrogenation of a sugar syrup and a stage of caramelization of hydrogenated sugar syrup, characterized in that the hydrogenated sugar syrup and caramelized is purified on ion exchange resins, said purification comprising at least one step on strong cationic resin at a temperature lower than 50 ° C, said temperature being selected as a function of the rate of reducing sugars desired in the non-crystallizable polyol syrup. The method according to claim 1, characterized in that the caramelization treatment is conducted in the hydrogenation reactor, under hydrogen and without separation of the catalyst, by introduction of sodium hydroxide at the end of the hydrogenation reaction. 3. The method according to any of claims 1 and 2, characterized in that the caramelization step consists of adjusting the pH of hydrogenated syrup to a value between 9 and 11, preferably between 9.5 and 11, when this pH is capable of being stable. 4. The method according to any of claims 1 to 3, characterized in that the purification step is conducted on strong cationic resin at a temperature below 50 ° C, then on anionic resin and finally on a mixed bed. The method according to any of claims 1 to 4, characterized in that the passage temperature over strong cationic resin is less than or equal to 40 ° C, preferably less than or equal to 30 ° C, and more preferably still between 20 and 30 ° C. ° C. The method according to any of claims 1 to 5, characterized in that the polyol syrup is a non-crystallisable sorbitol syrup. The method according to claim 6, characterized in that the non-crystallizable sorbitol syrup has a sorbitol content of at least 64% by weight, a maltitol content of at least 6% by weight, the content of oligo and polysaccharides constituting the 100% complement, these percentages expressed in comparison with the dry matter of the polyols present in the composition. 8. The use of a syrup of polyols capable of being obtained according to a process according to any of claims 1 to 7 for the preparation of products with basic pH, containing the alkaline agents or treated or obtained at high temperature 9. The composition of the toothpaste containing the polyol syrup obtainable according to a method according to any of claims 1 to 7.