Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
  • C01D7/38—Preparation in the form of granules, pieces or other shaped products
  • C01D7/40—Influencing the crystallisation process
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
  • C01D7/10—Preparation of bicarbonates from carbonates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
  • C01D7/22—Purification
  • C01D7/24—Crystallisation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/02—Particle morphology depicted by an image obtained by optical microscopy
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/51—Particles with a specific particle size distribution
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/11—Powder tap density

Definitions

• the invention relates to a process for the preparation of alkaline bicarbonate particles and to the alkaline bicarbonate particles obtainable by said process.
• the invention also relates to a process carried out with a view to controlling the specific gravity by flow of the powders constituted by said particles, and / or carried out in order to control the size of said particles.
• Alkali metal bicarbonates such as sodium bicarbonates
• NaHC0 3 and potassium (KHC0 3 ) are products with many properties, and interesting broad areas of use, ranging from the pharmaceutical industry, to food and feed, to the detergency, the treatment of acid fumes, and the treatment of non-ferrous metals.
• bicarbonates in the form of solid particles
• carbon dioxide a corresponding alkali metal carbonate solution (sodium carbonate or potassium carbonate for example) or a corresponding alkali metal hydroxide solution (eg sodium hydroxide or potassium hydroxide).
• these solutions are aqueous.
• water / alcohol solvent mixtures such as water / ethanol mixtures are also common. It is also common to crystallize bicarbonates by controlled cooling of bicarbonate solutions, or by evaporation of such solutions.
• the end users are interested in particle size cuts defined and optimized for their applications depending on the desired properties: for example dissolution rates, ability to be mixed with other powders homogeneously without segregation, fluidity of the powders for easy handling (measured for example by the angle of repose, or the flow velocity through a calibrated orifice), etc ...
• particle size distributions mass distributions of particles in different size fractions, unimodal or multi-modal distributions, spread or narrow particle size distributions
• particle shape factors circularity, robustness, larger concavity size, surface concavity index
• the present invention relates to a process for the preparation
• the additive is chosen from the following compounds: • sulphates, especially sodium sulphate and organosulphates
• Amines in particular primary amines, cyclic amines, quaternary amines comprising at least one carboxylic acid group;
• alkali metal hexametaphosphate in particular sodium
• Phosphates in particular organophosphates, and phosphonates
• the additive is present in the solution at a concentration of at least 1 ppm, preferably at least 5 ppm, more preferably at least 10 ppm.
• the inventors have in fact surprisingly found that the additives listed above, used during the crystallization of the alkali metal bicarbonate particles, made it possible to obtain particles having a synergy between their particle size, their form factor, and even their potentials. electrical charges on the surface, allowing either an adjustable and significant increase in the specific gravity per flow of the particles obtained, or a reduction in specific gravity. They also make it possible to modulate their granulometry, and their spreading or tightening of the particle size distributions.
• the invention also relates to the alkali metal bicarbonate particles thus obtained, and / or obtainable according to the present process.
• each mode, or variant of embodiment thus defined can be combined with another mode, or with another variant embodiment, for each mode or variant unless otherwise indicated or obviously incompatible when the range of the same value parameter is disjoint.
• any variant indicated as being preferred or advantageous may be combined with another variant or with the other variants indicated as being preferred or advantageous.
• a range of values for a variable defined by a low limit, or a high limit, or by a low limit and a high limit, also includes the embodiments where the variable is selected respectively in the value range: excluding the low limit, or excluding the high limit, or excluding the low and high limits.
• the description of several successive ranges of values for the same variable also includes the description of embodiments where the variable is chosen in any other intermediate range included in the successive ranges. For example, when it is described that "the quantity X is generally greater than 10,
• the present description also describes the embodiment where:" the magnitude X is greater than 11 ", or also the embodiment where:” the magnitude X is greater than 13.74 “, etc. .; 11 or 13.74 being values between 10 and 15.
• an additive means an additive or more than one additive.
• the term 'particle size distribution', or 'span', of a particle size distribution corresponds here to the following ratio: (D90-D10) / D50, the term D90 denoting the diameter for which 90% by weight particles have a size less than or equal to D90, the term D50 designating the diameter for which 50% by weight of the particles have a size less than or equal to D50 (average size by weight), the term D10 denoting the diameter for which %> by weight of the particles have a size less than or equal to D10.
• the present invention relates to a process for the preparation by crystallisation of alkali metal bicarbonate particles from a solution of carbonate and / or alkali metal bicarbonate (hereinafter referred to as 'the solution') in the presence of an additive in the solution, allowing to modify:
• the particle size distribution in particular the fraction of 'fine' particles smaller than 125 ⁇ , or the fraction of 'coarse' particles greater than 250 ⁇ , or particle size spreading (or 'span')
• the various additives mentioned below are crystal crystallization modifiers of alkali metal bicarbonates which can be used in a small amount in a solution of carbonate and / or alkali metal bicarbonate in which the crystals of Alkaline bicarbonate are crystallized.
• alkali metal bicarbonate particles means particles comprising at least 60%, advantageously at least 75%, more preferably at least 85%, even more
• the The alkali metal bicarbonate particles comprise at most 40%, preferably at most 25%, more preferably at most 15%, more preferably at most 10% or at most 5% or at most 1% of alkali metal carbonate.
• the alkali metal particles may also contain low levels of ammonium bicarbonate, generally at most 2%, or at most 1% or at most 0.7% ammonium bicarbonate. This is particularly the case when the particles are crystallized in solutions containing ammonia, such as during the crystallization of sodium bicarbonate in the Solvay process with ammonia, for the production of sodium carbonate.
• the alkali metal bicarbonate particles obtained in this process are generally referred to as "crude bicarbonate" (cf.
• the alkali metal bicarbonate may be lithium, sodium, potassium, rubidium or cesium bicarbonate.
• the alkali metal bicarbonate is sodium bicarbonate or sodium bicarbonate. More preferably the alkali metal bicarbonate is sodium bicarbonate.
• the alkali metal bicarbonate particles are preferably particles comprising at least 99% sodium bicarbonate and less than 1% sodium carbonate or water.
• the present invention has been realized on the discovery of the effects of the additives mentioned herein and the different process and / or product variants obtained by said process variants are described in more detail below.
• Item 1 Process for the preparation by crystallization of alkali metal bicarbonate particles from a solution of carbonate and / or alkali metal bicarbonate (hereinafter referred to as the 'solution') in the presence of an additive in the solution, characterized in that:
• the additive is chosen from the following compounds:
• Amines in particular primary amines, cyclic amines, quaternary amines comprising at least one carboxylic acid group; • hydroxysultaines;
• Alkali metal hexametaphosphate in particular sodium or potassium
• Phosphates in particular organophosphates, and phosphonates
• the additive is present in the solution at a concentration of at least 1 ppm, preferably at least 5 ppm, more preferably at least 10 ppm.
• Item 2 A method according to item 1 wherein the additive is an organo-sulfate and is selected from the following compounds:
• Alkyl sulphates comprising from 4 to 20 carbons, preferably from 8 to 16 carbons, or from 8 to 14 carbons, such as lauryl sulphate (dodecyl sulphate),
• alkyl ether sulphate such as Rhodapex ESB-70 / A2
• Item 3 A method according to item 1 wherein the additive is a sulfonate and is selected from the following compounds:
• Polysulfonates in particular polyvinylsulfonic acid and their alkali metal salts;
• Aminosulphonates in particular: N-methyltaurine, sodium N-methyltaurinate, isopropylamine dodecylbenzene sulphonate;
• amidosulphonates in particular those with more than 6 carbons
• sodium 2- [methyloleoylamino] ethane-1-sulphonate such as Geropon T / 77
• Geropon T / 77 sodium 2- [methyloleoylamino] ethane-1-sulphonate
• Sulphosuccinates in particular sodium docusate
• Primary amines in particular hexamethylenediamine
• Quaternary amines comprising at least one carboxylic acid group, in particular the quaternary amines of formula: (H 3 C) 3 -N-
• Quaternary amines comprising at least one sulphonate group, in particular hydroxysultaines, such as cocamidopropyl hydroxysultaine (such as Mirataine CBS);
• Cyclic amines such as Miranol DM
• polycarboxylate and is preferably chosen from the following compounds: polyacrylates, in particular crosslinked polyacrylates, or
• acrylic copolymers and maleic acid, or sodium prop-2-enoate such as Polyco, Rhotex GS, Acrysol lmw-45N, Hiviswako 105
• acrylic polyacrylates or copolymers, or their alkali metal salts with an average molecular weight of less than 8000 g / mol or greater than or equal to 8000 g / mol;
• Item 6 A method according to item 1 wherein the additive is a polysaccharide, and is preferably selected from the following compounds:
• Guar gums and their derivatives in particular hydroxypropylguar (such as Jaguar HP-105);
• Alginic acid and its salts such as sodium or calcium or copper (such as: Kaltostat, Calginat, Landalgine, Kalrostat, Kelacid, Vocoloid,
• Carboxymethylcellulose such as Aquaplast, Carmethose, Cellofas, Cellpro, Cellugel, Collowel, Ethoxose, Orabase, Lovosa);
• Item 7 A method according to item 1 wherein the additive is a polyether or an ether-phenol or a polyaromatic ester, and is preferably selected from the following compounds:
• Ethoxylated oleyl alcohol such as Rhodasurf ON / 870-E
• Branched octylphenoxy poly (ethyleneoxy) ethanol such as Igepal CA630
• ⁇ Ethoxylated polyarylphenol in particular exoxylated tristyrylphenol
• Sulfosuccinates in particular: sodium docusate (such as Aerosol OT, Constonate, Diomedicone, Clestol, Complemix, Deflin, Dioctlyn, Dioctylal, Diosuccin);
• sodium docusate such as Aerosol OT, Constonate, Diomedicone, Clestol, Complemix, Deflin, Dioctlyn, Dioctylal, Diosuccin
• Item 9 A method according to item 1 wherein the additive is an organophosphate or a phosphonate, and is preferably selected from the following compounds:
• Polyoxyethylene alkyl ether phosphate the alkyl chain advantageously comprising from 6 to 20 carbons, in particular polyoxyethylene octadecenyl ether phosphate (such as Lubrophos LB / 400-E);
• Poly (oxy-1,2-ethanediyl), alpha- (dinonylphenyl) -omega-hydroxyphosphate such as RHODAFAC RM-510;
• Alkyl-diphosphonic acids in particular those of semi-developed formula ((HO) 2 OP) -R- (PO (OH) 2 ) and with R alkyl group, or hydroxyalkyl, in particular with R 1 to 3 alkyl group carbons, or R hydroxyalkyl group comprising 1 to 3 carbons and 1 to 2 hydroxy groups (-OH) (such as etidronic acid ((HO) 2 OP) -C (CH 3 ) OH- (PO (OH) 2 )), or their salts, in particular of alkali metal such as sodium or potassium;
• Item 13 Process according to any one of items 1 to 12 wherein the crystallisation of alkali metal bicarbonate particles is carried out by carbonating the solution with carbon dioxide.
• Item 14 Method according to item 13 in which the carbonation of the solution is carried out at a temperature of at least 20 ° C, advantageously at least 30 ° C, and preferably at most 95 ° C, more preferably at least at most 90 ° C.
• Item 15 Process according to any one of items 1 to 14 wherein the crystallization of alkali metal bicarbonate particles is carried out by evaporation of at least a portion of the solution.
• Item 16 A method according to any one of items 1 to 15 wherein crystallisation of alkali metal bicarbonate particles is achieved by concomitant cooling and carbonation of the solution; or by cooling and by concomitant carbonation and evaporation of the solution.
• Item 19 A method according to any one of items 1 to 18, the additive of which is added to control or modify:
• particle size (such as D10, D50, D90 or span), or
• alkali metal bicarbonate particles obtained after separation of the crystallization solution and the alkaline bicarbonate particles.
• Item 20 Process according to any one of items 1 to 19, the additive of which is added to control or modify:
• alkali metal bicarbonate particles obtained after separation of the crystallization solution and the alkaline bicarbonate particles, and then drying the alkali metal bicarbonate particles.
• Item 21 A method according to item 20 wherein adding the additive increases the EPS, and increasing the ESP of the alkali metal bicarbonate particles by at least 10%, or from less than 20%>, or at least 30%>, or at least 40%>, or at least 50%>, or at least 60%>, or at least 70%>, or at least 80%>, or at least 90%>, or at least 100% relative to the PSE of alkali metal bicarbonate particles obtained under the same crystallization conditions but without addition of additive.
• Item 22 A method according to item 21 wherein adding the additive decreases the EPS, and decreasing the EPS of the alkali metal bicarbonate particles is at least 10%, or at least 15%. % with respect to the PSE of alkali metal bicarbonate particles obtained under the same conditions of crystallization but without addition of additive.
• Item 23 Method according to item 19 made to control the size of the alkaline bicarbonate particles, in particular for controlling the sieve past at 125 ⁇ or the sieve refusal at 250 ⁇ of the alkaline bicarbonate particles.
• Item 24 A method according to any one of items 19 to 21, the addition of which adds:
• additives listed in item 6 polysaccharides), in particular alginic acid or
• Item 25 Process according to item 24, the crystallization of the alkaline bicarbonate particles is carried out by cooling and / or carbonation.
• Item 26 A method according to any one of items 19 to 21, the additive addition of which makes it possible to:
• the additive is chosen from the additives listed in item 5 (polycarboxylates) and chosen from: polyacrylates, in particular crosslinked, or acrylic and maleic acid copolymers or their alkali metal salts, of weight higher average molecular weight and equal to 8000 g / mol.
• the additive is chosen from the additives listed in item 5 (polycarboxylates) and chosen from: polyacrylates, in particular crosslinked, or acrylic and maleic acid copolymers or their alkali metal salts, of weight average molecular weight less than 8000 g / mol.
• Item 28 Process according to item 26 or 27, the crystallization of the alkaline bicarbonate particles is carried out by cooling and / or carbonation.
• additive is selected from the additives listed in item 9 (an organophosphate or a phosphonate).
• Item 31 An alkali metal bicarbonate particle obtainable by the process according to any one of items 1 to 30 and comprising at least 10 ppm, advantageously at least 20 ppm of the additive
• the additives are used in the present invention, generally, at a concentration in the solution of at least 1 ppm, preferably at least 5 ppm, more preferably at least 10 ppm.
• ppm parts per million
• crystallization is done batchwise (batchwise) or corresponds to the proportion of additive introduced relative to the solution fed into the crystallization apparatus if the crystallization is carried out continuously. They correspond to the mg of additive active ingredient per kg of solution.
• the additive is present at a concentration of at most 200 ppm, advantageously at most 100 ppm, more preferably at most 70 ppm, still more preferably at most 50 ppm.
• Amounts of about (i.e., +/- 10%) of: 10 ppm, or 20 ppm, or 50 ppm of additive in the solution are particularly advantageous.
• the amounts of additives can be adjusted in order to adjust the desired value of the parameter, for example the EPS, or the sieve particle size refusal parameter, in particular at 125 ⁇ or at 250 ⁇ .
• the solution of carbonate and / or alkali metal bicarbonate is preferably an aqueous solution comprising from 1 to 30% by weight of alkali metal carbonate and / or comprising 1 to 18% by weight of alkali metal bicarbonate.
• the crystallisation of the particles according to the invention can be done with
• the solution is seeded.
• a quantity of seeds in a batch crystallization with seeding a quantity of seeds in a batch crystallization with seeding.
• Seeding of the order of 0.1 to 10% of crystals of bicarbonate is introduced before the start of crystallization of the bicarbonate particles according to the invention.
• the suspension density of the bicarbonate crystals producing in the crystallization apparatus constitutes the seeding itself.
• suspension densities of alkali metal bicarbonate particles based on the weight of the suspension of particles in the mother liquors of crystallization is generally from 0.1 to 25% by weight.
• the crystallisation of alkali metal bicarbonate particles is carried out by cooling the solution.
• the crystallization of alkali metal bicarbonate particles is carried out by carbonation of the solution with carbon dioxide.
• the crystallization of alkali metal bicarbonate particles is carried out by evaporation of at least a part of the solution.
• the crystallization of alkali metal bicarbonate particles is carried out by cooling and by concomitant carbonation of the solution; or by cooling and by concomitant carbonation and evaporation of the solution.
• the injection of the gas may not be saturated with the solvent of the solution at the temperature of the suspension of the crystallizing particles.
• the injection of the gas is accompanied by partial evaporation of the solvent from the solution. This also causes cooling of the solution.
• the continuous phase is the liquid phase and the gas phase is a dispersed phase in the liquid phase.
• the carbonation of the solution with carbon dioxide is carried out with a gas generally comprising: 10 to 100% of C0 2 by volume on dry gas, advantageously at least 20% C0 2 by volume on dry gas, more advantageously at least 30%> C0 2 by volume on dry gas, still more advantageously at least 35% of C0 2 by volume on dry gas
• the preparation by crystallization of alkali metal bicarbonate particles is generally carried out at a temperature of between 20 ° C and 95 ° C. It is advantageous that the temperature be at least 30 ° C. It is also advantageous if the temperature is at most 90 ° C.
• the flow-specific weight of the alkali metal bicarbonate particles is measured according to the following procedure: the particles are introduced into a frustoconical smooth steel hopper (greater diameter 53 mm, diameter 21 mm lower, height 58 mm) closed on its lower part by a shutter consisting of a slat of smooth horizontal steel. Then open the bottom of the hopper by removing the shutter, and the particles are collected in a cylinder of 50 cm 3 (internal diameter 37 mm, height 46 mm) located (its upper part) less than 5 cm under the shutter.
• Excess particles protruding from the cylinder are then stripped, without compacting the powder, and verifying that the whole cylinder is filled with powder to the brim, and the weight of the powder contained in the 50 cm 3 is weighed and the specific gravity weight ("free") of the powder is expressed by relating the apparent weight of the powder to the volume of 50 cm 3 expressed in kg / liter or kg / m 3 .
• Example 1 Crystallization by cooling of sodium bicarbonate particles - Control of the specific gravity by free flow.
• Equipment used double-shell 500 ml beakers stirred by magnetic bar at 350 rpm. Buchner filter and laboratory vacuum pump.
• BICAR used as inoculation is a sodium bicarbonate of "BICAR® Codex” brand of Pharmacopoeia quality, from SOLVAY sieved between 200 and 250 ⁇ .
• the suspension of bicarbonate particles is filtered on a beaker and washed with 50 ml of sodium bicarbonate saturated ethanol to remove the bulk of the mother liquors of crystallization.
• the particles are then dried in the open air overnight. Agglomerates due to drying are defeated on a stainless steel tray with a rubber stopper with a low pressure of the hand, and the powder
• Rhodacal DSB Rhodacal DSB
• organophosphates or phosphonates are decreases of 5 to 14% of the PSE compared to the reference PES.
• Example 2 Crystallization by cooling of sodium bicarbonate particles - Sieve refusal control.
• the ratio F add / F ref is the ratio of the mass fraction passed to 125 ⁇ of crystallized sodium bicarbonate in the presence of additive divided by the mass fraction passed at 125 ⁇ average of crystallized sodium bicarbonate without additive (ie 26 wt%):
• the ratio F add / F ref is the ratio of the mass fraction refused to 250 ⁇ of crystallized sodium bicarbonate in the presence of additive divided by the mass fraction refused at 250 ⁇ average of crystallized sodium bicarbonate without additive (ie 15 wt%):
• organophosphates such as:
• Example 3 Crystallization by carbonation of sodium bicarbonate particles.
• the present example illustrates a continuous carbonation of sodium bicarbonate manufacture without and with additives.
• the preparation by crystallization of sodium bicarbonate particles by carbonation is carried out in a closed precipitation reactor of 5 liters, agitated with 800 (referenced 'a') or 1070 revolutions per minute (referenced 'b').
• a feed solution containing 100 grams of sodium bicarbonate per kilogram of aqueous solution and 130 grams of sodium carbonate per kilogram of aqueous solution is continuously injected into the center of the stirred reactor at a rate of 3.3 liters per hour.
• Carbon dioxide is injected into the reactor at a rate of 750 normo-liters per hour through a pierced cane placed in the bottom of the reactor under the stirrer.
• the slurry of sodium bicarbonate particles is continuously withdrawn at the reactor base at a rate of 3.3 liters per hour to maintain a constant level in the reactor.
• the carbonation crystallization reactor is placed under relative pressure of the gas sky 200 to 600 mbar relative.
• the additive is prepared in a solution of 1% by mass of active ingredient in water in such a way that the amounts of additive expressed here are in mass of active material per mass of solution to be crystallized.
• the additive solution is injected into the heart of the stirred suspension.
• the average molecular weight of the additive used was 5100 g / mol (less than 8000 g / mol).
• part of the suspension of crystals is recovered which is filtered on Buchner filter and filter paper.
• the filtered solution comprises about 125 grams of sodium bicarbonate per kilogram of aqueous solution and 65 grams of sodium carbonate per kilogram of aqueous solution.
• the particles of sodium bicarbonate obtained on the funnel are washed with 250 ml of ethanol and then dried in the same manner as in Example 1.
• the particle powder thus obtained is characterized. The following measures are carried out:
• the dissolution time (comparative between the different samples) is measured with a conductimetric cell immersed in a beaker stirred with 1 liter of demineralized water maintained at 25 ° C (+/- 1 ° C). Stirring is carried out with a marine propeller at 350 rpm. 10 grams of sodium bicarbonate particles are introduced into the solution, these dissolve and induce an increase in the conductivity of the solution.
• the dissolution time corresponds to the time required to reach 95% of the final value of the conductivity in solution.
• the slope angle, of the powders obtained is measured after formation of a spill cone which the powder forms by dropping a sieve of size 710 ⁇ on a cylinder 50 mm in diameter and 80 mm in height.
• the height of the sieve relative to the top of the cone should be maintained between 2 and 3 cm.
• the slope angle AT (°) is calculated from the measurement of the height H (mm) of the pile of powder remaining on the cone:
• Measurement of fluidity consists in determining the flow of a powder sample, contained in a conical container, through a diameter orifice calibrated. Seven cones, 125 mm high and 43.5 mm in diameter at the high point, have an orifice of increasing flow diameter: 2.4 mm (tube 1), 4.9 mm (tube 2), 8.0 ( tube 3), 9.8 mm (tube 4), 12.3 (tube 5), 15.2 (tube 6) and 18.1 mm (tube 7). The test determines from which minimum opening (tube 1 to 7) the product can flow.
• the wear index at 63 ⁇ consists of the difference of the relative measurement of powder mass of less than 63 ⁇ before and after a wear force.
• the wear test consists of passing 100 grams of powder through a rotating stainless steel drum 150 mm in internal diameter, 22 cm internal length, and equipped with 3 blades 35 mm wide. The rotation of the drum at 40 revolutions per minute lasts 20 minutes.
• test 6 (a) (sodium polyacrylate at 500 ppm): 1.4 m 2 / g.
• Polyacrylate (average molecular weight: 5100 g / mol) added at 5, 10, 50 and 500 ppm, and sodium hexametaphosphate at 50 ppm reduce the particle size of the bicarbonate particles and the EPS.
• the bank angles are increased.
• the dissolution times are decreased except at high polyacrylate addition at 500 ppm - Test 6 (a) where the dissolution time is increased.
• Sodium hexametaphosphate at 50 ppm lowers the particle size of the bicarbonate particles and the EPS.
• Polysaccharides such as alginic acid at 10, 20 and 50 ppm and
• carboxymethylcellulose at 20 ppm increase the particle size, decrease the span, generally increase the EPS, and increase the dissolution time.
• the wear index is improved with a reduction of the fines ⁇ 63 ⁇ generated during the wear test. Photographs of sodium bicarbonate particles, taken under an optical microscope, indicate a more compact shape

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• 2019
  • 2019-05-28 US US16/423,709 patent/US20190276326A1/en not_active Abandoned
  • 2019-07-08 JP JP2019126800A patent/JP2019206474A/ja active Pending

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