Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2240/00—Testing
  • H05H2240/20—Non-thermal plasma

Definitions

• the subject of the present invention is a new process for the polymerization of sugars, making it possible to obtain hyperbranched and / or compact polysaccharides in solid form.
• Plasma is an ionized gas that may or may not be at thermodynamic equilibrium. This technology is widely used especially for surface treatment and the depollution of water or air. Plasma assisted polymerization is commonly used for the deposition of organic polymers on inorganic or organic substrates. However, in all cases, the use of volatile and ionizable monomers is necessary so that the latter can be in the gas phase in the plasma zone. Therefore, single monomers are mainly used among which include furans, acrylonitrile, styrene, acetylene, etc. In addition, in current processes, plasma-produced polymers are graft polymers as they develop on the surface of a solid support.
• Another object of the present invention is to provide a rapid process with high productivity.
• Another object of the present invention is to provide a dry process (ie without solvent), not requiring the use of a catalyst or a solid support.
• the present invention relates to a process for preparing a polysaccharide comprising a non-thermal plasma polymerization step of a saccharide monomer.
• the method of the invention therefore consists in polymerizing at least one saccharide monomer by plasma treatment. This polymerization is also called plasma assisted polymerization.
• the specificity of the process of the invention is therefore the presence of a plasma for polymerizing sugars.
• the present invention is based on the use of plasma technology to prepare polysaccharides from saccharide monomer.
• the polymerization step is not carried out in the presence of a solid support.
• the method of the invention is therefore different from a plasma surface treatment method because it does not consist in placing the saccharide monomer on a support to be treated.
• the method of the invention makes it possible to dispense with the use of a solid support, which allows a gain in terms of efficiency because the process does not include a step of recovering and purifying the polysaccharide obtained.
• a plasma is a partially or totally ionized gas. It consists of electrons and ions, possibly atoms or molecules. There are different types of plasma that can be globally differentiated between thermal plasma and non-thermal plasma.
• the thermal plasma is in fact the state of a gas heated to a very high temperature (that is to say above 3000 ° C). At this temperature, the gas is strongly ionized. There is therefore simultaneous presence of free electrons and positively charged species, these different species being in a state of equilibrium, this state persisting as long as the temperature remains the same.
• a very high temperature that is to say above 3000 ° C.
• the non-thermal plasma (or cold plasma) or out of equilibrium corresponds to a transient state of ionization of the gas during which there has been formation of free electrons and thus of positively charged species, which will very quickly recombine or react to form again a neutral, non-ionized gas, the gas being mainly at a low or moderate temperature.
• the gas In general, to create a non-thermal plasma, the gas must be subjected to an intense electric field in order to generate a process of acceleration of the few free electrons still present in the gases and resulting, for example, from the action of cosmic rays. These few electrons, very strongly accelerated by the electric field are then able, by inelastic shocks, to extract electrons from the gas molecules, which in turn will be accelerated.
• This process is called an electronic avalanche and is the initiation step of the non-thermal plasma.
• These highly energetic electrons are then able to activate the molecules of the gas, either by transferring some of their energy or even by breaking chemical bonds, thus making these species very reactive and therefore able to react, even if the average conditions gas would not allow it.
• the device then consists of literally blowing the ions and electrons by a strong gas flow so as to always remain below the concentration of ions and electrons necessary for the formation of the electric arc.
• a particular shape of the facing electrodes whose distance between them is not constant makes it possible to avoid a too high value of the electric field and the risk of formation of the arc.
• the discharge is initiated at the point where the electrodes are closest, then develops, pushed by the gas stream into the area where the electrodes progressively diverge.
• the plasma used according to the invention is a non-thermal atmospheric plasma (NTAP).
• NTAP non-thermal atmospheric plasma
• the process of the invention is carried out with a dielectric barrier discharge plasma.
• the energy required for the creation of the cold plasma is obtained by applying a strong electric field between two electrodes generated by the application of a high electrical voltage between these electrodes, either in the form of a pulse of voltage or alternating voltage.
• the dielectric barrier discharge plasma (DBD) is formed when a dielectric material (glass, quartz, ceramic, alumina ...) is placed between the two electrodes, thus avoiding the transition to the electric arc.
• the presence of the dielectric material also allows the formation of a more homogeneous plasma, distributed over the entire surface of the electrodes.
• the saccharide monomer is deposited directly between the electrodes without the presence of an additional solid support.
• the saccharide monomer is a monosaccharide or a disaccharide.
• the saccharide monomer is a monosaccharide.
• Monosaccharides used according to the invention include glucose, mannose, galactose or xylose.
• disaccharides used according to the invention mention may be made of maltulose, isomaltulose, maltose or turanose.
• the saccharide monomer is in the form of a powder.
• the polysaccharides obtained according to the process of the invention are polymers or copolymers. Indeed, the process of the invention may be a polymerization or copolymerization process.
• the process of the invention makes it possible to synthesize polysaccharides which can also be indifferently called “sugars” or “carbohydrates”.
• the polysaccharides obtained according to the invention are hyperbranched polymers and / or compact or related to dendritic polymers (or dendrimers). They are obtained in solid form.
• the process of the invention advantageously makes it possible to obtain the polysaccharide directly and, preferably, does not comprise a subsequent purification step, contrary to the usual methods of the state of the art.
• the process advantageously makes it possible to control the degree of polymerization of the polysaccharides obtained. It is therefore possible, for example, to stop the polymerization when it is desired and thus to control the degree of polymerization and the molecular weight.
• the polysaccharides obtained according to the process of the invention have molar masses ranging from 1000 g / mol to 100,000 g / mol. They may have degrees of polymerization (DP) of from 3 to 400 and their hydrodynamic radii may vary from 0.8 to 40 nm.
• the polymerization step is carried out at a temperature below the melting temperature of the saccharide monomer, which allows the process to be carried out at a temperature at which the saccharide monomer is solid.
• the polymerization step is carried out at a temperature between 0 ° C and 140 ° C, preferably between 0 ° C and 100 ° C.
• the polymerization step of the process of the invention is carried out in the absence of catalyst and solvent.
• the polysaccharides obtained according to the invention are solid and white products which do not require a post-treatment stage (such as effluent recycling, purification, decolorization steps, etc.) after polymerization, contrary to the processes of the state of the art.
• a post-treatment stage such as effluent recycling, purification, decolorization steps, etc.
• the polymerization step is carried out for a period of less than 30 minutes, preferably of between 5 and 20 minutes.
• the method according to the invention may comprise a first step which consists in placing at least one saccharide monomer in a gaseous medium capable of forming a plasma.
• the saccharide monomer is placed between two electrodes, in particular insulated from each other by a dielectric material.
• the method according to the invention also comprises a step consisting in forming the plasma, in particular by heating the gaseous medium at a very high temperature (thermal plasma) or by subjecting this medium to an intense electric field (non plasma). -thermal).
• the gaseous medium is subjected to an electric field of at least 5.10 5 V / m
• the method according to the invention comprises the following steps:
• the voltage used for the method of the invention is between 8.5 kV and 10.5 kV.
• the process of the invention may further comprise a preliminary step of heating or cooling the reaction medium (corresponding to the space (or reactor) formed by the electrodes ).
• the mannose was placed in the solid state between two 25 cm 2 copper electrodes arranged in parallel and each insulated from each other by a dielectric (called DBD reactor).
• DBD reactor dielectric
• the gap between the two electrodes was set at 4 mm.
• the plasma was created using a bipolar generator at a voltage of 9.5 kV and a frequency of 2.2 KHz.
• the air flow is 100 mL / min.
• mannose samples were taken after 10, 15 and 30 min and then analyzed by steric exclusion chromatography (SEC). It has thus been found that mannose is completely consumed after only 15 minutes of plasma treatment and that products of higher molecular weight are formed.
• the polymerization of mannose can also be indirectly observed by X-ray diffraction analysis (XRD) and by 1 H and 13 C NMR. Indeed, after plasma treatment, a significant widening of the signals is observed in both types of analyzes what is often the signature of anarchic (or disordered) polymerization.
• XRD X-ray diffraction analysis
• 1 H and 13 C NMR 1 H and 13 C NMR
• XPS X-ray photoelectron spectrometry
• XPS X-ray photoelectron spectroscopy
• the mannose polymers were analyzed by GC / MS using commercial standards for assignment of different peaks. More particularly, we focused on the dissincharide fraction in order to determine the different positions of the mannose involved in the polymerization. Disaccharide fraction analysis was performed at 43% conversion of mannose so that the signals could be more accurately quantified. These analyzes reveal that all of the hydroxyl groups are involved in the polymerization of mannose. However, the link between two mannose units is primarily between positions 1 and 6 (71% probability). The selectivity between the ⁇ -1, 6 and ⁇ -1, 6 bonds is respectively 27% and 44%. It is clear that the polymerization of mannose takes place in a disordered manner which rationalizes the signal widening observed by XRD and NMR.
• the mannose polymers were analyzed by SEC / MALS to obtain information on the mass distribution and conformation of the mannose polymers. Elution profiles show at least three different types of populations that differ in their hydrodynamic volume, reflecting a strong polydispersity. These analyzes reveal that the molar masses of the mannose polymer range from 2 ⁇ 10 3 to 9 ⁇ 10 6 g / mol with a hydrodynamic radius ranging from 1.2 to 37.2 nm. More generally, the mannose polymers are characterized by an average molecular weight (M w ) of 95,590 g / mol, an intrinsic viscosity ( ⁇ ) of 7.7 ml / g and a hydrodynamic radius (Rh) of 3.3 nm. Mannose polymers also exhibit high polydispersity (M w / M n) of 15 which is, again, in accordance with a disordered polymerization mannose.
• M w average molecular weight
• ⁇ intrinsic viscosity
• Rh hydrodynamic radius
• Rh and M w are bound together and obey equation (1) where Rh and M w are the hydrodynamic radius and the molar mass respectively, v h is the hydrodynamic coefficient and K h is a constant.
• Rh K h M3 ⁇ 4. equate i 0n (1)
• the hydrodynamic coefficient depends on the general shape of the macromolecules, the temperature and the macromolecule-solvent interactions.
• a v h theoretical of 0.33 is obtained for a sphere, for a 0.5-0.6 shaped coil 1 and to a rod.
• the v h obtained is 0.43.
• a linear relationship between Rh and M w is obtained, meaning that the mannose polymers have similar conformations regardless of the degree of polymerization.
• a v h value of 0.43 means that the mannose polymers adopt a conformation close to a sphere, which means that the mannose polymers have compact and / or hyperbranched structures. This statement is supported by the high solubility of mannose polymers in water (500 g / L).

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• Polysaccharides And Polysaccharide Derivatives (AREA)

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• 2015
  • 2015-07-30 FR FR1557325A patent/FR3039548B1/fr not_active Expired - Fee Related
• 2016
  • 2016-07-28 CN CN201680044791.5A patent/CN107922511A/zh active Pending
  • 2016-07-28 EP EP16745708.4A patent/EP3328900A1/fr not_active Withdrawn
  • 2016-07-28 WO PCT/EP2016/068116 patent/WO2017017243A1/fr active Application Filing
  • 2016-07-28 US US15/748,482 patent/US20180223001A1/en not_active Abandoned

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