Title of Invention | A METHOD FOR PREPARING A NON-CRYSTALLISABLE POLYOL SYRUP. |
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Abstract | TITLE : A METHOD OF PREPARING ANON-CRYSTALLISABLE POLYOL SYRUP. The invention concerns a method for preparing a heat-stable and alkali-resistant, non-crystallizable polyol syrup, comprising a step which consists in hydrogenating a sugar syrup and a step which consists in caramelizing the hydrogenated sugar syrup. The invention is characterised in that the hydrogenated and caramelized sugar syrup is purified on ion-exchanging resins, said purification comprising at least a process which consists in passing it at least once on strong cationic resin at a temperature less than 50 °C and selected according to the desired reducing sugar proportion in the non-crystallizable polyol syrup. The invention also concerns the use of the resulting polyol syrup for preparing toothpaste. (FIG. - nil) |
Full Text | A METHOD OF PREPARING A NON-CRYSTALLISABLE POLYOL SYRUP The invention relates to a new method of preparing a non-crystallisable polyol syrup that is resistant to heat and to alkalis. To be more specific, it relates to a new method of preparing a polyol syrup that can be used in the production of soap or detergent, in the formulation of pharmaceutical syrups or toothpaste, i.e. in any application that requires, in an alkaline and/or hot environment, resistance to the formation of colorations that are undesirable or compounds that are unsuitable from the taste point of view. By polyols are meant the products obtained by catalytic hydrogenation of simple reducing sugars, complex reducing sugars such as disaccharides, oligo- saccharides and polysaccharides, and mixtures thereof, which will be referred to hereinafter as "sugar syrup". As a general rule, the simple reducing sugars intended for catalytic hydrogenation in accordance with 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 on catalytic hydrogenation yield maltitol, isomalt, isomaltitol and lactitol. In the context of the present invention, non- crystallisable composition means mixtures of polyols that form non-crystallisable syrups at 20°C with a dry materials proportion of 70% when stored in a hermetically sealed container for one month. The non-crystallisable sorbitol in the context of the invention is defined in the European Pharmacopoeia, 1997, paragraph 0437. Sorbitol syrups are widely used in the agriculture- foodstuffs, pharmaceutical and chemical fields. In the formulation of toothpaste, and in particular in the production of sodium bicarbonate toothpaste, the use of sorbitol syrups as humectants is possible only if they are stable in the presence of sodium bicarbonate and do not cause any brown coloration during storage. This coloration is caused by reaction of the bicarbonate on the reducing sugars: glucose, maltose, oligo-saccharides and polysaccharides. The intensity of the coloration increases with the number of units of the polysaccharide, and a molecule of maltose therefore causes more coloration than a molecule of dextrose. Coloration is also strongly accelerated by the temperature to which the syrup is exposed. It has been noted that the same intensity of coloration is obtained after storage for 10 days at 45°C and after storage for 15 months at 20°C. It is preferable for these syrups to be non-crystallisable to facilitate handling and transporting them, regardless of the climatic conditions, and to assure that finished products prepared from such syrups are stable. Maltitol syrups also represent a large class and are mainly used in preparing non-cariogenic pharmaceutical and food products. Although more costly, xylitol syrups are being widely used because of their high sweetening power, their dental properties and their excellent humectant characteristics. It is known that the coloration of a polyol syrup in the presence of alkalis is related to the presence of reducing free sugars: glucose, maltose, oligo-saccharides and polysaccharides. Improving the stability of such syrups therefore entails eliminating these free sugars. Various approaches have already been investigated on a laboratory scale. Japanese patent JP 51.86406 offers the prospect of improving the purity of crystallisable sorbitol syrups by reducing crystallised glucose under alkaline conditions maintained throughout the reduction reaction, in order to obtain very pure sorbitol containing little non-reduced sugar. However, the above technique is of no practical benefit on an industrial scale because it requires a costly feed, monitoring and control system and the constant addition of buffer and alkaline solution during the reaction represents a penalty in terms of the subsequent purification step. The method is also relatively highly polluting because of the large quantities of reactants used. Furthermore, there is no reference to the stability of the sorbitol syrups obtained by said method. Japanese patent JP 41.12212 mentions a method of preparing sorbitol of maximum purity resistant to heat and to alkalis which entails reduction by adding hydrogen at high pressure and either adjusting the pH of the solution to a value from 8 to 10 just before the reduction reaction is completed or heating the reduced sorbitol solution, whose pH has previously been adjusted to a value from 8 to 10 by means of an alkali, to a temperature from 60°C to 90°C, followed, after decomposition of the residual directly reducing sugars, by separation by filtration, with or without neutralisation by means of an acid and with or without decoloration over charcoal, followed by purification over ion-exchange resin. The above method, which is applied to a crystallisable sorbitol solution, gives rise to considerable formation of impurities because the reducing sugars are subjected to a relatively long processing duration, of the order of five hours, and does not impart sufficient stability. Japanese patents JP 63.79844 and JP 71.45090 describe a method of preparing polyols resistant to heat and to alkalis which entails treating for one to two hours in a hot alkaline medium an aqueous solution of polyols purified a first time by treatment with carbon black and then over ion-exchange resin, and then purifying again the solution obtained at 50°C, by passage over ion-exchange resin. The above method is intended in particular for crystallisable sorbitol syrups obtained from very pure glucose syrups. Crystallisable syrups of this kind are not suitable for use in particular in toothpaste because of their many drawbacks. Also, the above method is particularly complex because of the multiple operations it involves, and is therefore difficult to apply on an industrial scale. Patent EP 0 711 743, of which the applicant is the patentee, describes polyol compositions which are highly chemically stable in an alkaline medium and have a very low reactivity. These compositions, which are particularly suitable for use in a basic medium necessitating absence of coloration, are obtained by catalytic hydrogenation of simple or complex reducing sugars and then stabilising the syrup and purifying the stabilised syrup. The stabilisation step entails submitting the sorbitol syrups obtained by hydrogenation to oxidation, caramelisation or fermentation, so as to obtain syrups exhibiting an optical density in an S test of less than or equal to 0.100. The applicant has shown that satisfactory stability can be obtained only at low values in the above test, which reflects the susceptibility of the compositions to coloration in an alkaline medium. Aiming to improve further the performance of a method of the above kind, and with a view to limiting mineral and organic waste, in order to protect the environment, the applicant has, after lengthy research, developed a new method which yields non-crystallisable polyol syrups that are sufficiently stable in an alkaline medium and, by limiting purification operations, offers a high yield and reduced pollution, which prior art techniques cannot provide. Thus the applicant has found that, to obtain non- crystallisable polyol syrups that are resistant to heat and to alkalis, it is necessary to submit a sugar syrup that has undergone a hydrogenation and caramelisation step to a step of purification over at least one strong cationic resin at a temperature below 50°C, said temperature being chosen as a function of the desired proportion of reducing sugars in the final composition. The invention therefore provides a new method of preparing a non-crystallisable polyol syrup, resistant to heat and alkaline media, including a step of hydrogenating a sugar syrup and a step of caramelising the hydrogenated sugar syrup, characterised in that the hydrogenated and caramelised sugar syrup undergoes purification over ion exchange resins, said purification including at least one passage over strong cationic resin at a temperature less than 50°C, said temperature being chosen as a function of the desired proportion of reducing sugars in the non-crystallisable polyol syrup. Considerable research by the applicant has shown the importance of the working temperature on maintaining the quality of the product during purification over a strong cationic resin. The quality of the composition after purification and in particular its final proportion of reducing sugars is inversely proportional to the temperature at which it is passed over the strong cationic resin. Purification over strong cationic resin in accordance with the invention is therefore carried out at a temperature below 50°C, chosen as a function of the desired proportion of reducing sugars in the final composition after purification. The applicant has found that the temperature during passage over the resin can be adjusted as a function of the proportion of reducing sugars obtained after caramelisation and of the desired final proportion of reducing sugars in the purified polyol syrup. The required proportion varies as a function of the intended applications of the syrup. For preparing toothpaste, in addition to the nature of the alkaline agent present in the paste, it is necessary in particular to take into account the nature of the colouring agents used to determine the acceptable limit for resistance to coloration by the polyol syrup. Slight yellow coloration is more readily acceptable for blue pastes. The flavours used are also a factor to be taken into account when determining the acceptable limit on the proportion of reducing sugars. Thus for some bicarbonate pastes, the acceptable limit is 3 50 parts per million of reducing sugars (expressed as dextrose equivalents and hereinafter abbreviated to ppm), and for others, such as those containing pyrophosphates, proportions of up to 500 ppm may suit. This is equally applicable to other pharmaceutical, cosmetic and food applications. Under optimum conditions for hydrogenating and then caramelising a non-crystallisable polyol syrup, minimum reducing sugar proportions of the order of 50 ppm to 100 ppm are obtained. The applicant has found that under these conditions the maximum temperature at which a syrup of this kind can be purified over strong cationic resin is 50°C if, allowing for the increased proportion of reducing sugars in the resins, a final value less than or equal to 500 ppm of reducing sugars is to be obtained, regarded as being the acceptable maximum limit. Below 50°C, the temperature during passage over the resin can therefore be adjusted as a function of the required proportion of reducing sugars in the final composition and of the proportion of reducing sugars initially present after caramelisation, as explained more fully later. Accordingly, passage over strong cationic resin can advantageously be adjusted to a temperature of less than or equal to 40°C, preferably less than or equal to 30°C and even more preferably from 20°C to 30°C if a very low proportion of reducing sugars is desired in the polyol composition according to the invention. The purification as such is effected using standard techniques, i.e. first passing over strong cationic resin, then strong anionic resin, and then passage over a mixed bed which is an equal parts mixture of the two resins. It is also possible to modify the order in which the resins are combined. The aim of the strong cationic resin is to eliminate cations, in particular sodium coining from the sodium carbonate used in caramelisation, and the soluble nickel coming from the hydrogenation catalyst. The object of the strong anionic resin is to eliminate organic anions such as gluconate in particular, which is a degradation product from the caramelisation step. The use of a mixed bed in the final step optimises purification by palliating any leaks of ions that might have occurred in preceding steps. The preferred cation exchange resin is a strong cationic resin carrying a sulphonic type functional group SO3H used in strong acid form, for example the IR 200 C resin from ROHM and HAAS. The preferred anionic resin is a strong anionic resin such as the IRA 910 resin from the same manufacturer. The mixed bed consists of a mixture of the two resins. In one advantageous embodiment of the method according to the invention, to prevent excessively long residence times in the resin, with the attendant risk of encouraging deterioration of the purified polyol syrup, the purification over resins is effected at a flowrate corresponding to 1.5 times the volume of the resin column through which the syrup passes per hour. In another advantageous embodiment of the method according to the invention, caramelisation is conducted in the hydrogenation reactor, under hydrogen and without separating the catalyst, by introducing an alkaline agent at the end of the hydrogenation reaction, at a time when the pH is likely to be stable after adding the alkaline agent, and without using a buffer. Considerable research by the applicant has shown that the hydrogenation step can advantageously be combined with caramelisation in the same reactor, without adding buffer, so as to obtain a polyol composition that is stable in a hot alkaline medium from sugar syrup in a manner which is economical and also not very polluting after purification. In the context of the present invention, caramelisation means alkaline degradation of the reducing sugars of the hydrogenate, leading to the formation of corresponding enols. Alkaline agents suitable for caramelisation include strong or weak bases. In a preferred embodiment, the alkaline agent used for caramelisation is sodium carbonate. The sugar syrups subjected to the method according to the invention can include in particular glucose syrups, fructose syrups, glucose syrups rich in maltose and xylose syrups. The sugar syrup advantageously contains 60% to 95% dextrose, 0.1% to 20% maltose, the remainder to 100% consisting of polysaccharides and oligo-saccharides, the above percentages being percentages by weight relative to the dry weight of the saccharides contained in said syrup. The catalytic hydrogenation is carried out in a manner known in the art, in a twin-jacket reactor, over Raney nickel catalysts, although any other sugar hydrogenation catalyst may be suitable. It is preferably carried out at a hydrogen pressure from 3 0 bars to 100 bars and at a temperature from 120°C to 150°C, and even more preferably at a temperature from 130°C to 150°C, in order to optimise the rate of hydrogenation whilst limiting secondary reactions. Sodium carbonate is introduced into the reactor to obtain a pH from 9 to 11, and preferably from 9.5 to 11, at a time when the pH is sufficiently stable to require no buffer solution nor addition of a massive quantity of sodium carbonate to maintain the pH at that value. This is generally achieved after 90 minutes of hydrogenation under the conditions in accordance with the invention. This criterion for introducing the sodium carbonate results from studies of hydrogenation kinetics and caramelisation conditions. If the reaction medium is still rich in free reducing sugars, introducing the alkaline agent destabilises the pH, which is significantly reduced because of the conversion of the free reducing sugars into corresponding acids. Accordingly, beyond a reducing sugars proportion of approximately 0.4%, too much acid is formed and the pH therefore falls, rendering ineffective the stabilising action of the caramelisation and entailing the addition of too much sodium carbonate. It is therefore preferable to introduce the alkaline agent when the proportion of residual reducing sugars is less than 0.2%, and more preferably less than or equal to 0.1%. When the pH in the reactor is less than 9, the caramelisation is insufficient. When it is greater than 11, the caramelisation is satisfactory but the ionic charge of the hydrogenate becomes too high, which leads to a consequential rejection of chlorides when regenerating the cation exchange resins. The applicant has found that, at a pH from 9.5 to 11, the excess sodium carbonate in the reaction medium is sufficient to achieve complete caramelisation of the sugars. The method according to the invention produces polyol syrups that are particularly suitable for use in the preparation of basic pH products such as toothpastes based on sodium bicarbonate or the family of sodium phosphates, anti-acid compositions, shaving foams or depilatory creams, or for the production of products at high temperatures, whilst achieving a previously unequalled return on investment, and a minimum level of organic and mineral wastes. In one advantageous embodiment of the method according to the invention, the syrup obtained is a non- crystallisable sorbitol syrup. The non-crystallisable sorbitol syrup obtained preferably contains at least 64 wt.% of sorbitol, at least 6 wt.% of maltitol, the remainder to 100% consisting of oligo-saccharides and polysaccharides, the above percentages being expressed relative to the dry weight of polyols present in the composition. The syrup that can be obtained by the method according to the invention can therefore be used with advantage in preparing basic pH products containing alkaline agents or treated or obtained at a high temperature. The invention also provides a toothpaste composition containing the polyol syrup that can be obtained by the method according to the invention. The invention is illustrated by the following non- limiting examples. Example 1 A sugar syrup with the composition given below was introduced with stirring into a 20-litre twin-jacket reactor containing Raney nickel in suspension: - dextrose: 75%/dry - maltose: 8%/dry - maltotriose: 3.6%/dry - higher DP: 13.4%/dry The dry material of the reaction medium was 40 wt.% and the Raney nickel proportion was 5 wt.%, in both cases relative to the dry weight. Hydrogenation was carried out for 90 minutes at a pressure of 50 bars and a temperature of 140°C. A 3 wt.% solution of sodium carbonate was introduced for 15 minutes so as to obtain a hydrogenate pH of 10.8. The pH was found to be stable and the proportion of reducing sugars was found to be less than 0.4 wt.%. Hydrogenation was continued for 20 minutes. Then the stirring of the reactor was stopped, the contents allowed to settle for 15 minutes, and the supernatant liquor drained into a settling tank to recover the catalyst. The supernatant liquor from the settling tank was then filtered to eliminate the final traces of catalyst. The syrup obtained in the above manner was cooled to 25°C and then purified over strong cationic resin, then over anionic resin and finally over the mixed bed. The syrup obtained was then subjected to a test for its resistance to alkaline agents. The test, referred to as the S test, is described in patent EP 0 711 743, of which the applicant is the patentee. The lower the value obtained in the S test (optical density less than 0.1), the more stable the polyol composition. 500 mg of ultrapure sodium hydrogen carbonate and 250 mg of a 20% aqueous solution of ammonia were added to 5 ml of syrup. The result was mixed and heated in a water bath without stirring at 100°C for two hours. The solution was cooled to 20°C and its optical density measured at a wavelength of 42 0 nm using a spectrophotometer such as the PERKIN-ELMER Lambda 5 UV/VIS spectrophotometer. A calibration range was produced in the same manner by substituting for the 5 ml of syrup, 3 ml of pure water and 2 ml of anhydrous pure glucose solutions with concentrations of 100, 200, 300, 400, 500, 600 and 1000 ppm. The respective absorbencies of the above glucose solutions were 0.04, 0.08, 0.120, 0.160, 0.205, 0.250, 0.413. The syrup obtained in accordance with the present invention had a relatively low optical density of 0.04. This was equivalent to a glucose proportion of 100 ppm/dry, which indicates very high resistance to alkalis. The method according to the invention therefore produces a non-crystallisable polyol composition that is highly resistant to alkaline and/or hot media in a more economical and less polluting way than the prior art techniques. Example 2: Influence of temperature on purification by means of ion exchange resins The syrup obtained in example 1 before purification was divided into seven fractions. The fractions were purified over strong cationic resin at respective temperatures of 20, 30, 35, 40, 45, 50, 52 and 60°C (fractions A to H), then over anionic resin and finally over the mixed bed. An S test was performed on each fraction after purification and for each point the difference was computed compared to the original test (delta S test). The results are given in ppm dextrose equivalent. The results show clearly the influence of the working temperature on purification over strong cationic resin. This shows that it is possible to adapt the temperature of the composition during purification according to the reducing sugar requirements necessitated by the intended end use, which confers unheard of flexibility on the method according to the invention. Example 3: Formulation of a sodium bicarbonate toothpaste A sodium bicarbonate toothpaste with the following formula was produced using products A and F from example 2 (purified over resins at 20°C and at 50°C): The toothpastes A and B obtained had respective pH of 8.4 and 8.7 in 10% solution. After storage for six months at room temperature, because of the satisfactory purity of product A, the colour of paste A had not changed. However, paste B was an unacceptable yellowish colour after the same storage time. Example 4: Formulation of anti-tartar toothpastes with sodium pyrophosphate An anti-tartar toothpaste with the following formula was produced using sodium pyrophosphate as the anti- tartar agent and product D from example 2 (purified on strong cationic resin at 40°C): The final pH of the toothpaste was 7.8 as such and 8.6 after dilution to 10%. The colour of the toothpaste had not changed after storage of six months at room temperature. Syrup D from example 2 is therefore entirely suitable for use in a toothpaste in the presence of anti- tartar agent. WE CLAIM: 1. Process for preparing a noncrystallizable polyol syrup stable to heat and to alkaline medium, using a stop of hydrogonation of a sugar syrup and a stop of caramelization of the hydrogenated sugar syrup, characterized in that the hydrogenated and caramelized sugar syrup is subjected to purification on ion-exchange resins, the said purification comprising at least one passage over a strong cationic rosin at a temperature of loss than 30oC, the said temperature boing chosen according to the level of reducing sugars desired in the noncrystalizable polyol syrup. 2. Process according to Claim 1, characterized in that the caramelization treatment is performed in the hydrogenation reactor, under hydrogen and without separation of the catalyst, by introducing sodium hydroxide at the and of the hydrogenation reaction. 3. Process according to either of Claims 1 and 2, characterized in that the caramelization step consists in bringing the pH of the hydrogenated syrup to a value of between 9 and 11, preferably of between 9.5 and 11, whan this pH is likely to be stable. 4. Process according to any one of Claims 1 to 3, characterized in that the purification stop is performed on a strong cationic resin at a temperature of loss than 30oC, and than on an anionic resin and finally on a mixed bed. 5. Process according to any one of Claims 1 to 4, characterized in that the temperature for passing over a strong cationic resin is between 20 and less than 30oC. 6. Process according to any one of claims 1 to 5, characterized in that the polyol syrup is a noncrystallizable sorbitol syrup. 7. Process according to Claim 6, characterized in that the noncrystallizable sorbitol syrup has a sorbitol content of at least 64% by weight, the oligo-and polysaccharide content constituting the balance for 100%, these percentages being expressed relative to the dry matter content of the polyois present in the composition. The invention relates to a method of preparing a non-crystallisable polyol syrup, resistant to heat and alkaline media, including a step of hydrogenating a sugar syrup and a step of caramelising the hydrogenated sugar syrup, characterised in that the hydrogenated and caramelised sugar syrup undergoes purification over ion exchange resins, said purification including at least one passage over strong cationic resins at a temperature less than 50°C, said temperature being chosen as a function of the desired proportion of reducing sugars in the non-crystallisable polyol syrup. It also relates to the use of the polyol syrup obtained in the preparation of toothpaste. |
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in-pct-2001-00651-kol-abstract.pdf
in-pct-2001-00651-kol-claims.pdf
in-pct-2001-00651-kol-correspondence.pdf
in-pct-2001-00651-kol-description (complete).pdf
in-pct-2001-00651-kol-form 1.pdf
in-pct-2001-00651-kol-form 18.pdf
in-pct-2001-00651-kol-form 2.pdf
in-pct-2001-00651-kol-form 3.pdf
in-pct-2001-00651-kol-form 5.pdf
in-pct-2001-00651-kol-letter patent.pdf
in-pct-2001-00651-kol-reply f.e.r.pdf
in-pct-2001-00651-kol-translated copy of priority document.pdf
IN-PCT-2001-651-KOL-CORRESPONDENCE 1.1.pdf
IN-PCT-2001-651-KOL-FORM 27.pdf
IN-PCT-2001-651-KOL-FORM-27.pdf
Patent Number | 216902 | ||||||||||||
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Indian Patent Application Number | IN/PCT/2001/651/KOL | ||||||||||||
PG Journal Number | 12/2008 | ||||||||||||
Publication Date | 21-Mar-2008 | ||||||||||||
Grant Date | 19-Mar-2008 | ||||||||||||
Date of Filing | 21-Jun-2001 | ||||||||||||
Name of Patentee | ROQUETTE FRERES | ||||||||||||
Applicant Address | 62136 LESTREM FRANCE, A FRENCH COMPANY. | ||||||||||||
Inventors:
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PCT International Classification Number | C07C 29/76,29/88, | ||||||||||||
PCT International Application Number | PCT/FR00/02963 | ||||||||||||
PCT International Filing date | 2000-10-25 | ||||||||||||
PCT Conventions:
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