FR2802932A1 - Galactomannan oligomers obtained by depolymerization, subjecting the solid galactomannan, especially guar gum, a solvent system and an oxidant to elevated temperature and pressure - Google Patents

Abstract

Preparation of oligomers of galactomannans by subjecting one or more galactomannans in solid form, a solvent system comprising a solvent, and optionally a co-solvent and an oxidizing agent to a temperature of 250 deg C or less and a pressure of 0.2-30 MPa, is new. An Independent claim is also included for galactomannan oligomers of molecular weight 2000-10000 g/mole produced by the novel method.

Description

 The present invention relates to a process for the preparation of oligomers of at least one galactomanan under the effect of the temperature and of the temperature of the galactomannans. pressure.

It also relates to the oligomers obtained or obtainable by this process, and their uses.

The invention further relates to the compositions based on the aforementioned oligomers. Galactomannans are nonionic polysaccharides extracted from the albumen of leguminous seeds of which they constitute the reserve carbohydrate. They are especially known and used as a texturing agent and especially for their viscosity, thickening, stabilizing, water-retaining and film-forming properties. Among the most employed are guar gum, locust bean gum, and tara gum.

They are chemically neutral macromolecules, comprising a main chain consisting of D-mannopyranose units linked in position p (1-4) and substituted by D-galactopyranose units at position a (1-6).

The different galactomannans are distinguished by the proportion of D-mannopyranose and D-galactopyranose units which are represented by their ratio mannose / galactose (hereinafter M / G). Although variable from one species to another, the mannose / galactose ratio is of the order of 1 for fenugreek, 2 for guar, 3 for tara, and 4 for carob.

Various industries, such as the cosmetics, dyeing, food, detergency, agrochemical, industrial formulations, pharmaceutical, construction materials, drilling fluids use these polysaccharides, among others, for their texture property and in particular thickener or viscosity, stabilizer, emulsifier, gelling agent, binder.

These polysaccharides are all the more interesting by their nature, they are compatible with other compounds and therefore can be used in combination with them to produce synergistic effects, among others, in terms of texture. For example, locust bean gum in combination with xanthan gum can lead to gels of different strengths and consistencies more or less elastic.

Native galactomannans are highly hydrophilic polymers which, at low concentrations, lead to highly viscous solutions. Depending on the intended application, this aspect may limit their use.

The properties of galactomannans can be related to their molecular weight. For example, at different molecular weights, it is possible to obtain galactomannans whose texturing properties and in particular the thickening or viscosity property can be adjusted. The conventional routes for access to galactomanides of different molecular weights are - oxidative route in the presence of alkaline, - basic route in the presence of oxygen, - enzymatic route, - acid depolymerization.

These depolymerization methods are known per se. For example, reference may be made to EP0130946 for the oxidative depolymerization process in the presence of alkaline, and for the basic route in the presence of oxygen, PCT / US98 / 14677, with regard to enzymatic depolymerization, and "Hydrolysis Glykozidischer Bindungen", Jozsef Szejtli, 1975, VEB Fachbuchverlag, Leipzig, for acidic depolymerization.

Although widely used, these methods have drawbacks.

In fact, chemical depolymerization, whether basic or acidic, leads to galactomannans of lower molecular weight. However, the resulting galactomannans require extensive purification to remove the byproducts formed during the process. In addition, with this type of process, obtaining galactomannans of molecular weight less than 50 000 g / mol is long and expensive. Moreover, in certain cases, the operating conditions are such that the degradation of the galactomannan takes place before its depolymerization.

The enzymatic depolymerization which has the advantage of allowing selective cleavage of the galactomanan (relative to the chemical process) is a method which is not economically advantageous. In addition, in some cases, it is difficult to deactivate the enzyme at the end of the reaction without degrading the depolymerized product.

The object of the present invention is to overcome the disadvantages mentioned above by proposing a process for the preparation of galactomannan oligomers which is simple and inexpensive to implement and in which the resulting oligomers are devoid of secondary products.

Another object of the present invention is to provide a method which makes it possible to access a wider range of oligomers of galactomannans, that is to say to molecular weight ranges that can not be reached by conventional channels. .

These objects are achieved by the present invention which relates to a process for the preparation of oligomers of at least one galactomanan, characterized in that a mixture comprising at least one galactomannan in solid form is subjected to a system of solvent comprising at least one solvent and optionally at least one co-solvent, and - at least one oxidizing agent, at a temperature of at most 250 ° C. and a pressure of at most 30 × 10 5 Pa.

The subject of the invention is also the oligomers of galactomannans obtained or obtainable by the aforementioned process.

Other advantages and features of the present invention will become clear from reading the description and the examples which follow.

The subject of the present invention is therefore a process for the preparation of oligomers of at least one galactomanan, characterized in that a mixture comprising: <B> - </ B> at least one galactomannan in solid form, - a solvent system comprising at least one solvent and optionally at least one co-solvent, and - at least one oxidizing agent, at a temperature of at most 250 C and a pressure of at most 30.10s Pa.

In the context of the present invention, the term "oligomer" of galactomannans is understood to mean galactomannans whose molecular weight is less than about 2.5 × 10 6 g / mol. The term "oligomer" of galactomannans denotes more particularly galactomannans whose weight-average molecular weight is advantageously less than 1.5 × 10 6 g / mol, preferably less than 600 000 g / mol, more particularly between 2000 and 50 000 g / mol. According to one embodiment of the invention, the weight-average molecular weight of the oligomers is between 2000 and 10 000 g / mol.

The weight-average molecular weight can be measured by size exclusion chromatography (SEC).

 Optionally, it can also be determined directly by light scattering or from intrinsic viscosity using a calibration according to G. Robinson's "Viscosity-Molecular weight relationships, intrinsic chain flexibility and dynamic solution properties of guar galactomannan". Ross Murphy, ER Morris, Carbohydrate Research 107, p. 17-32, 1982.

Depending on the desired molecular weight, by adjusting the temperature, the pressure, and the reaction time, all of the molecular weight ranges mentioned above can be obtained.

In the context of the present invention, the galactomannans can be used alone or as a mixture. Among the galcatomannans, mention may be made, without limitation, of galactomannans having a mannose / galactose (M / G) ratio of at most equal to 5, and more particularly guar, carob, cassia and tara. According to a preferred embodiment of the invention, the galactomannan is guar.

The galactomannan is advantageously in the form of a powder.

The powder is obtained by conventional grinding means such as grinding in mills of the type - roll mills for the powder of average grain size mesh 100, that is to say a flour having at most 1% by mass of particles greater than 80 mesh and not more than 10% mass of particles less than 200 mesh; pin mills for the finer particle size 200, that is to say a powder having no particles greater than 80 mesh and having at most 60% by mass of particles smaller than 200. mesh, and mesh type 175, that is to say a powder having at most 1% by weight of particles greater than 80 mesh and at most 75% by mass of particles smaller than 200 mesh.

The powder can be used as it is or after treatment with suitable enzymes such as, for example, alkaline, acid and / or neutral proteases; lipases; phytases; alkaline, acidic and / or neutral phosphatases; amylases. Enzyme treatment is by conventional and known methods.

The particle size of said powder may vary between 10 and 150 microns. In the case of treated powders, this particle size is more particularly 20 to 60 microns, preferably 30 to 50 microns.

Granulometry measurements can be carried out using the laser granulometry technique, using a MALVERN granulometer, sold by the company Malvem Instruments S.A.

In addition to the galactomannan (s), the mixture comprises a solvent system comprising at least one solvent and optionally at least one co-solvent.

The solvent may be selected from carbon dioxide, water, ammonia, C 1 -C 5 alkanes, C 1 and C 2 fluoroalkyls, alone or in mixtures.

As C 1 -C 5 alkane alkanes, mention may be made of ethane, propane, butane and pentane, and their isomers.

When the solvent system comprises a co-solvent, the latter is advantageously chosen from protic solvents, and more particularly from C1-C4 alcohols, C1-C4 ketones. There may be mentioned, for example, ethanol as alcohol and acetone as ketone. The depolymerization of galactomannans to galactomanan oligomers requires the presence of at least one oxidizing agent. This agent can be selected from air, 02, hydrogen peroxide, nitric acid, and mixtures thereof.

The aforementioned mixture is then subjected to temperature and pressure conditions such that galactomannan undergoes no degradation and only depolymerization.

The temperature is advantageously between 20 and 250 ° C., preferably between 40 and 150 ° C.

The pressure is more particularly between 2 and 20 MPa, preferably between 3 and 9 MPa.

It should be noted that during the process of the invention, the starting galactomanan and the galactomannan (s) oligomer (s) obtained have substantially the same M / G ratio.

In the process of the invention the choice of the solvent system as well as the oxidizing agent is made in such a way that before the reaction they are either in liquid form or in gas form, and that during the reaction, under the effect of temperature and pressure, they preferably go to the state of monophasic fluid.

The process can thus be considered as a process for the depolymerization of galactomannans in the solid state by an oxidizing agent and a solvent system in the fluid state.

The weight ratio of galactomannan (s) / solvent system is from 0.01 to 100, preferably from about 0.1 to 10, more preferably from 1 to 5.

As already indicated, the solvent system may comprise at least one solvent and optionally at least one co-solvent. When said system comprises both the solvent and the co-solvent, the ratio by weight of solvent (s) / co-solvent (s) is between 99/1 and 70 I30, advantageously 95/5 and 85 I15, preferably about 90/10.

With regard to the oxidizing agent (s), the ratio between the amount of oxidizing agent (s), expressed in moles, and the number of equivalents in average galactomannan unit (ie 162) is included between 100 and 1.6 × 10 -4, advantageously between 100 and 4.10 -4. This ratio is more particularly between 0.1 and 5 × 10 3, and preferably between 0.1 and 2.5 × 10 -2.

The reaction time is variable and will of course depend on the desired molecular weight and operating conditions including the temperature of the reaction and the amount of the oxidizing agent. In general, it varies between 1 minute and 2 hours.

After the reaction, the reaction medium is decompressed so as to optionally remove the solvent, the co-solvent, and the oxidizing agent. The oligomer is then recovered in solid form. Subsequently, the oligomer may undergo a drying step.

The process of the invention may be carried out batchwise, semi-continuously, or even continuously.

In the preferred embodiments of the invention, the process is carried out batchwise or semi-continuously.

The process of the invention can be carried out in any type of reactor which makes it possible to carry out processes in heterogeneous medium, especially solid / fluid medium, and to reach the necessary temperatures and pressures.

The reactor may be stainless steel or other materials. It can be arranged horizontally or vertically.

In a batch-type process, the following procedure is preferably used: the reactants are first introduced into the reactor; - The solvent system is then introduced into the reagent mixture resulting in the increase of the pressure inside the reactor; - The reactor is then brought to the desired temperature by supply of heat, for example by a circulation of a heat transfer fluid.

The temperature and the pressure are kept constant for a time which is determined according to the mass of the oligomer that one seeks to obtain.

In a semi-continuous type process, it is possible to advantageously operate in the following manner: the reactor is first loaded with galactomannan (s); the reactor is then brought to the desired temperature by supply of heat, for example by a circulation of a coolant, the mixture of oxidizing agent (s) and solvent system is compressed and introduced under pressure continuously in the reactor maintained at the desired pressure, for example using a high-pressure liquid displacement pump that regulates the flow of the mixture.

The temperature, the pressure and the flow rate are kept constant until the desired oligomer is obtained.

In a continuous type process, one can operate more particularly in the following way - the reactor is continuously charged with galactomannan, using a suitable system such as for example an extruder type screw system; - The reactor is brought to the desired temperature by supply of heat, for example by a circulation of a heat transfer fluid; the mixture of oxidizing agent (s) and of solvent system is then compressed and introduced, under pressure, continuously into the reactor which is itself maintained at the desired pressure, for example with the aid of a high pressure volumetric liquid pump which regulates the flow of the mixture The temperature, the pressure and the flow rate are kept constant until the desired oligomer is obtained.

The subject of the present invention is also the oligomers of galactomannans obtained or obtainable by the process according to the invention.

More particularly, this method makes it possible to access a range of galactomanan oligomers not yet obtained by the known depolymerization processes, that is to say molecular masses of between 2000 and 10,000 g / mol.

The invention also extends to the uses of galactomannan oligomers obtained or obtainable by the process of the invention, in the cosmetics, dyeing, food, detergency, agrochemical, industrial formulations, pharmaceutical, construction, drilling fluids.

Finally, the subject of the invention is the compositions based on oligomers of galactomannans obtained or likely to be obtained by the process of the invention, in the fields of cosmetics, dyeing, food, detergency, agrochemistry, those of industrial formulations, pharmaceutical, building materials, drilling fluids.

Concrete but non-limiting examples of the invention will now be presented.

<B> EXAMPLES <B> <U> </ U> </ U> </ U> </ U> </ U> </ B> methods </ U> </ U> </ B> </ B> </ B> </ B> The oligomers of galactomannans obtained are characterized according to two techniques # size exclusion chromatography (SEC) to obtain the molecular weight by weight; # proton nuclear magnetic resonance (H NMR) to verify the durability of the mannose / galactose molar ratio. # Size exclusion chromatography The analyzes were carried out using an SEC apparatus comprising an injection system (Waters 515 + Wisp +), two chromatographic columns (Shodex SB 806HQ 30 cm 5 Nm and Asahi GFA 30 60 cm 5 Nm) and two detection systems (Waters IRI refractometer 410 and MALLS Wyatt laser light scattering He 633 nm).

The eluting solvent is Millipore 18 Mg2 water at pH 9-10 containing 0.1 M LiCl and 200 ppm NaN3. The solvent flow rate is 0.8 ml / min.

The injected solution (100 NI) contains about 1% of product and the molecular weight is established by MALLS without calibration. Indeed, the extrapolated light scattering at zero angle is proportional to C x M x (dnldc) 2 - C corresponds to the concentration of the oligomer, - M corresponds to the molecular weight by weight, and - the ratio (dnldc) here is equal to 0.140.

 Proton nuclear magnetic resonance </ B> Before analysis, the sample is solubilized in D20 for 20 hours at 80 ° C. The analysis is carried out at 80 ° C. The mannose / galactose ratio (M / G) is directly accessible by comparing the intensities of the lines respectively at 5 and 4.7 ppm.

<B> <U> Example 1 </ U> <U>: <B> </ B> </ U> Oligomer <B> <U> of </ U> </ A 50 cc, batch reactor is charged with 2.5 g of a molar mass 2 guar, 5.106 g / mol.

10 cc of a H 2 O 2 /H 2 O / C 2 H 5 OHOH mixture at 5 × 10 -2 mol / l of H 2 O 2. The whole is brought to 20 MPa by injection of CO2 under pressure at 50 C.

At the end of the reaction, the residual H 2 O 2 / H 2 O / C 2 H 50 H mixture is extracted by flushing with CO 2.

A guar of molecular weight by weight of 100,000 g / mol is recovered.

The M / G ratio of the starting guar (M = 2, 5.106 g / mol) and that of the guar oligomer (M = 100,000 g / mol) is substantially the same.

<B> <U> Example 2 </ U> </ U>: <B> </ B> </ U> Oligomer <B> <U> of </ U> </ B guar A 50 cc reactor, operating semi-continuously, is charged with 2.5 g of a guar molar mass 2, 5.106 g / mol.

The assembly is compressed at 20 MPa by injection of CO 2 under pressure.

20 cc of a mixture of oxidant (H 2 O 2 / H 2 O / C 2 H 5 O 5 to 5 × 10 3 Me / l H 2 O 2) is injected into the reactor with CO 2 in a weight ratio CO 2 / oxidant equal to 90/10.

The whole is brought to 20 MPa by injection of CO2 under pressure at 50 C.

At the end of the reaction, the residual H 2 O 2 / H 2 O / C 2 H 50 H mixture is extracted by flushing with CO 2.

A guar of molecular weight of 92,000 g / mol is recovered.

The M / G ratio of the starting guar (M = 2, 5.106 g / mol) and that of the guar oligomer (M = 92 000 g / mol) is substantially the same.

<B> <U> Example 3 </ U> <U>: <B> Preparation process </ U> of oligomer <B> <U> of </ U> </ B> qua A reactor of 50 cc, operating semi-continuously, is charged with 2.5 g of a guar molar mass 2, 5.106 g / mol.

The assembly is compressed at 20 MPa by injection of CO 2 under pressure.

20 cc of a mixture of oxidant (H 2 O 2 / H 2 O / C 2 H 50 H with 5 × 10 -2 mol / l of H 2 O 2) is injected into the reactor with CO 2 in a weight ratio CO 2 / Oxidizer equal to 90 I 10.

The whole is brought to 20 MPa by injection of CO2 under pressure at 50 C.

At the end of the reaction, the residual H 2 O 2 / H 2 O / C 2 H 50 H mixture is extracted by flushing with CO 2.

A guar of molecular weight by weight of 6000 g / mol is recovered.

The M / G ratio of the starting guar (M = 2, 5.106 g / mole) and that of the guar oligomer (M = 6000 g / mole) is substantially the same.

<U> Example 4: Preparation Process </ U> of oligomer <U> of </ U> guar A 50 cc reactor operating semi-continuously is charged with 2.5 g of a mass guar Molar 2, 5.106 g / mole.

The assembly is compressed at 819 Pa by injection of CO 2 under pressure.

20 cc of a mixture of oxidant (H.sub.2 O.sub.2 / H.sub.2 O / C2H.sub.50H with 5.10-2 mol / l of H.sub.2 O.sub.2) is injected into the reactor with CO.sub.2 in a weight ratio CO.sub.2 / oxidant equal to 90/10.

The whole is brought to 20 MPa by injection of CO 2 under pressure at 50 ° C. At the end of the reaction, the residual mixture H 2 O 2 / H 2 O 1 Cl 2 HSOH is extracted by flushing with CO 2.

A guar of molecular weight by weight of 10,000 g / mol is recovered.

The MIG ratio of the starting guar (M = 2, 5.106 g / mol) and that of the guar oligomer (M = 10 000 g / mol) is substantially the same.

<B> <U> Example 5 </ U> <U>: <B> Preparation process </ U> of oligomer <B> <U> of </ U> </ A 50 cc, batch reactor is charged with 2.5 g of molar mass 2, 5 × 10 6 g / mol.

10 cc of H2021H20 / C2HSOH mixture at 5.10-4 mol / l of H2O2. The whole is brought to 20 MPa by injection of H20 under pressure at 50 C.

At the end of the reaction, the residual mixture H 2 O 2 / H 2 O / C 2 HSOH is extracted by flushing with CO 2.

A guar of molecular weight of 725,000 g / mol is recovered.

The M / G ratio of the starting guar (M = 2, 5.106 g / mol) and that of the guar oligomer (M = 725 000 g / mol) is substantially the same.

Claims (19)

A process for the preparation of oligomers of at least one galactomanan, characterized in that a mixture comprising at least one galactomannan in solid form is subjected to a solvent system comprising at least one solvent and optionally at least one co-solvent, and an oxidizing agent, at a temperature of at most 250 C and a pressure of at most 300 bar. 2. Process according to claim 1, characterized in that the weight-average molecular weight of the oligomers of galactomannan (s) is less than 1.5 × 10 6 g / mol, preferably less than 600 000 g / mol, more particularly between 2000 and 50 ° C. 000 g / mole. 3. Method according to one of claims 1 or 2, characterized in that the weight-average molecular weight of galactomannan oligomers (s) is between 2000 and 10 000g / mol. 4. Method according to claim 1, characterized in that the galactomannan has a ratio mannose / galactose (M / G) of at most equal to 5. 5. Method according to any one of claims 1 to 4, characterized in that the galactomannan is guar. 6. Process according to any one of Claims 1 to 5, characterized in that the solvent is chosen from carbon dioxide, water, ammonia, C1-C5 alkanes and C1- and C2-fluoroalkyls. or in mixtures. 7. Process according to any one of Claims 1 to 5, characterized in that the cosolvent is chosen from C 1 -C 4 alcohols and C 1 -C 4 ketones. 8. Method according to any one of claims 1 to 7, characterized in that the oxidizing agent is selected from air, 02, hydrogen peroxide, nitric acid, and mixtures thereof. 9. Method according to any one of claims 1 to 8, characterized in that the temperature is between 20 and 250 C, preferably between 40 and 150 C. 10. Process according to any one of claims 1 to 9, characterized in that the pressure is between 2 and 20 MPa, preferably between 3 and 9 MPa. 11. Method according to any one of claims 1 to 10, characterized in that the solvent system and the oxidizing agent pass to the state of monophasic fluid during the reaction. 12. Process according to any one of the preceding claims, characterized in that the weight ratio of galactomannan (s) / solvent system is from 0.01 to 100, preferably from approximately 0.1 to 10, more particularly from 1 to 5. 13. Process according to any one of Claims 1 to 12, characterized in that in the solvent system comprising at least one solvent and at least one co-solvent, the ratio by weight of solvent (s) / co-solvent ( s) is between 99/1 and 70/30, preferably 95/5 and 85/15, preferably about 9010. 14. Method according to any one of claims 1 to 13, characterized in that the ratio between the amount of oxidizing agent (s), expressed in moles, and the average number of equivalents of galactomannan is between 100 and 1.6.10-4, advantageously between 100 and 4.10-4. 15. Process according to claim 14, characterized in that the ratio between the amount of oxidizing agent (s), expressed in moles, of between 0.1 and 5.10-3, and preferably between 0.1 and 2.5.10-z. 16. Oligomers of galactomannans obtained by the process according to any one of claims 1 to 15. 17. Oligomers of galactomannans with a weight-average molecular mass of between 2000 and 10,000 g / mol obtainable by the process according to any one of Claims 1 to 15. 18. Use of galactomannan oligomers according to one of claims 16 or 17 in the cosmetics, dyeing, food, detergency, agrochemical, industrial formulations, pharmaceutical, construction materials, drilling fluids. 19. Composition based on galactomannan oligomers according to one of claims 16 or 17, in the fields of cosmetics, dye, food, detergency, agrochemical, those of industrial formulations, pharmaceutical, construction materials, drilling fluids.