Binder composition for agglomerating ores

Abstract

The present invention relates to a binding composition for the manufacture of ore agglomerates, comprising at least the following two distinct organic binding agents: - a non-ionic or anionic water-soluble synthetic polymer P1 with a weight average molecular weight between 500,000 and 3 million Daltons, - a non-ionic or anionic water-soluble synthetic polymer P2 with a weight average molecular weight greater than 2 million Daltons, polymers P1 and P2 both being in the form of solid particles, P1 being obtained by a gel polymerization process of at least one non-ionic or anionic monomer in the presence of: - at least 1% by weight of a polymer P3, said polymer P3 containing at least 10% by weight of at least one hydrophobic monomer, and / or - at least 1% to 20% by weight of at least one hydrophobic monomer. The invention also relates to ore agglomerates containing between 2000 and 50,000 ppm of this binding composition.

Description

Title of the invention: Binder composition for agglomerating ores Scope of the invention

[0001] The invention relates to the technical field of ore agglomerates. The invention relates to a binding composition that improves, in particular, the agglomeration step for obtaining ore agglomerates at low temperatures. Said binding composition comprises a mixture of at least two organic binding agents of a polymeric nature. The invention also relates, as a product, to ore agglomerates containing said binding composition. Prior state of the art

[0002] The vast majority of metals are obtained from ores found naturally in the ground or in mines. In the first stage of the metal recovery process, the element of interest, i.e., the metal (for example, iron for making steel), is recovered from the molten ore in a blast furnace. In order to be introduced directly into this blast furnace, the ore of the element of interest must be in a standard form of significant size. If this is not the case, it is necessary to convert the ore particles into agglomerates larger than the particle size. Agglomeration is a process based on the adhesion of the ore particles to one another. Five agglomeration technologies exist in metallurgy: briquetting, nodulation, extrusion, pelletizing, and sintering.These techniques are known and described in numerous documents such as Wolfgang Pietsch's book "Agglomeration in Industry" or, in particular, in patent EP 0097486. Nowadays, the increasing use of lower quality ores forces manufacturers to grind the ore more finely, which makes the agglomeration step essential.

[0003] During this agglomeration stage, the use of a binding agent or binding composition is necessary to ensure good physical properties such as the mechanical strength of the agglomerates. A "binding agent" or "binding composition" optimizes the adhesion of the ore particles to each other in order to form an agglomerate with sufficient mechanical properties to withstand the vibrations and movements to which it is subjected during its various handling operations.

[0004] Among the bonding agents traditionally used, we will mention cement (Portland), clays and more particularly bentonites, starch, cellulose, molasses, possibly in combination with lime, etc... The use of these agents Bonding poses problems due to the high presence of impurities that are detrimental to the industrial process (such as sulfur impurities in steelmaking) and / or leads to agglomerates with unsatisfactory physical properties. In recent years, new binding compositions have been developed by manufacturers to counteract these undesirable effects. US patents 5,002,607 and EP 2,548,978 describe processes in which agglomerates are produced using a binding composition comprising at least one synthetic polymer of organic nature and at least one inorganic binding agent.

[0005] Generally, agglomerates such as iron ore pellets are formed by adding a binding agent to crushed ores and stirring them in the presence of a small amount of water to form a wet mixture, then shoveling the mixture to form green (wet) pellets. These green pellets are then baked in a furnace from an inlet temperature of 200-400°C to a final temperature of approximately 1400°C. Such a process for forming iron ore pellets is described, for example, in document EP 0 225 171.

[0006] For the final agglomerate to exhibit good physical properties, the cooking stage is essential. However, this stage is very energy-intensive in terms of fossil fuels. This has a considerable impact on agglomeration plants, both ecologically and economically.

[0007] In view of the current energy situation, it is more than necessary to find sustainable and efficient solutions to obtain quality agglomerates, that is to say respecting the expected physical properties of the technique, while combining productivity gains and energy savings.

[0008] One of the solutions found by manufacturers to limit the environmental impact of producing these agglomerates has been to agglomerate the ore at low temperatures, i.e., at a firing temperature not exceeding 250°C. Unfortunately, this type of process does not allow for obtaining the expected physical properties of the agglomerates, based on the binder compositions mentioned above. The agglomerates crack even before reaching the processing equipment such as blast furnaces. Their handling becomes laborious and their storage is difficult.

[0009] The present invention overcomes the drawbacks of the prior art by describing a binding composition that improves the agglomeration step to allow the low-temperature production of ore agglomerates with satisfactory physical properties. Description of the invention

[0010] The invention relates to a binding composition for the manufacture of ore agglomerates, generally at low temperature, comprising at least the following two distinct organic binding agents (two polymers having the function of binding agents) distinct organic bonds: PI and P2): - a non-ionic or anionic water-soluble synthetic polymer (PI) with a weight-average molecular weight between 500,000 and 3 million Daltons, - a non-ionic or anionic water-soluble synthetic polymer P2 with a weight average molecular weight greater than 2 million Daltons, the polymers PI and P2 both being in the form of solid particles, PI being obtained by a gel polymerization process of at least one non-ionic or anionic monomer in the presence of: - of at least 1% by weight of a P3 polymer, said P3 polymer containing at least 10% by weight of at least one hydrophobic monomer, and / or - in the presence of at least 1% to 20% by weight of at least one hydrophobic monomer.

[0011] Another aspect of the invention relates to ore agglomerates comprising between 2,000 and 50,000 ppm of said binding composition, relative to the weight of the ore agglomerates. Description of the invention Definitions and general information

[0012] In the present application, the term "polymer" refers to both homopolymers and copolymers of at least two distinct monomers.

[0013] As used herein, the expression "water-soluble polymer" means a polymer which gives an aqueous solution free of insoluble particles when dissolved under stirring for 4 hours at 25°C and with a concentration of 20 gL 1 in deionized water.

[0014] An "anionic polymer" means a polymer containing at least one anionic monomer and optionally at least one nonionic monomer. A "nonionic polymer" means a polymer containing only one or more nonionic monomers. Generally, a polymer containing a monomer means a polymer obtained by polymerizing a multitude of molecules of that monomer.

[0015] As used herein, the expression "hydrophilic monomer" refers to a monomer whose octanol / water partition coefficient Kow is less than 1, determined at a temperature of 25 °C and with a pH between 6 and 8.

[0016] The expression "hydrophobic monomer" refers to a monomer whose octanol / water partition coefficient Kow is greater than 1, determined at a temperature of 25 °C and with a pH between 6 and 8.

[0017] The octanol / water partition coefficient Kow is defined as follows: [Math 1] [monomer] octanol Kow = -------F----- [monomer game]

[0018] where [monomer]octanol = equilibrium concentration of the monomer in g / L in n-octanol, and [monomer]water = equilibrium concentration of the monomer in g / L in water.

[0019] According to the invention, the term "low temperature" means a temperature not exceeding 250°C.

[0020] In this application, the term "agglomerate" refers to the product resulting from an agglomeration technology chosen from pelletizing, sintering, nodulation, briquetting or extrusion.

[0021] The "solid particles" according to the present invention are always defined by their sizes. The median number size (D50) of the solid particles is defined as the largest dimension (which is the diameter in the case of spherical particles) of the particles for which half of the particle population lies below this value. The particle size refers to the average diameter measured using a laser diffraction particle analyzer according to conventional techniques known to those skilled in the art. An example of an instrument for measuring the average diameter is the Mastersizer from Malvem Instruments.

[0022] According to the invention, the ranges of values ​​include the lower and upper bounds. Thus, the ranges of values ​​"between 0.1 and 1.0" and "from 0.1 to 1" include the values ​​0.1 and 1.0.

[0023] According to the present invention, the weight-average molecular weight of the polymers is determined by measuring the intrinsic viscosity. The intrinsic viscosity can be measured by any method known to those skilled in the art. In particular, it is calculated by the method of measuring viscosity in solution, which consists of determining reduced viscosity values ​​for different concentrations using a graphical method. This method involves plotting the reduced viscosity values ​​(on the y-axis) as a function of the concentration (on the x-axis), and then extrapolating the curve to zero concentration. The intrinsic viscosity value is read from the y-axis or using the least squares method. The weight-average molecular weight is then determined using the Mark-Houwink equation: [q] = KM“ where [q] represents the intrinsic viscosity of the polymer determined by the solution viscosity measurement method, K represents an empirical constant, M represents the molecular weight of the polymer, and a represents the Mark-Houwink coefficient. a and K depend on the specific polymer-solvent system. Tables familiar to those skilled in the art provide the values ​​of a and K according to the polymer-solvent system. Polymer PI

[0024] The binding composition, according to the invention, comprises a non-ionic or anionic PI water-soluble polymer of weight average molecular weight between 500,000 and 3 million (= 3.106) daltons, more preferably between 500,000 and 2,500,000 daltons, and even more preferably between 500,000 and 2,000,000 daltons.

[0025] The total sum of the monomers is equal to 100% of the PI polymer.

[0026] According to a preferred embodiment, the PI polymer is non-ionic.

[0027] If present, the anionic monomer(s) of the water-soluble polymer PI is preferably chosen from the group comprising monomers possessing a vinyl function, in particular acrylic, maleic, fumaric, malonic, itaconic, or allylic. It may also contain at least one carboxylate, phosphonate, phosphate, sulfonate, or other anionically charged group.Preferred monomers belonging to this class include, for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylamidoundecanoic acid, 3-acrylamido-3-methylbutanoic acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), vinylsulfonic acid, vinylphosphonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropyl acrylate, allylphosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane disulfonic acid, their salts, and mixtures thereof. Preferably, this refers to acrylic acid or itaconic acid. Even more preferably, it refers to acrylic acid.

[0028] Thus, in a particular embodiment of the invention, the anionic monomer(s) can be salified.

[0029] By "salified," it is understood that at least one acid function of the anionic monomer is replaced by a salt that neutralizes the negative charge of the acid function. In other words, the unsalified form corresponds to the acidic form of the monomer, for example RC(=O)-OH in the case of the carboxylic acid function, while the neutralized form of the monomer corresponds to the form RC(=O)-O X+, where X+ corresponds to a positively charged salt. The neutralization of the acid functions of the water-soluble polymer can be partial or total. The salified form advantageously corresponds to salts of alkali metals (Li, Na, K...), alkaline earth metals (Ca, Mg...), or ammonium (for example, the ammonium ion or a tertiary ammonium compound). Sodium salts are preferred. Salification can occur before or after polymerization.

[0030] As explained above, this does not preclude the presence, in the PI polymer, of at least one anionic monomer unit containing (non-neutralized) carboxylic acid functions. In other words, the simultaneous presence of anionic monomers with carboxylic acid functions and the same monomers with carboxylate functions is possible.

[0031] Even more preferably, the PI polymer comprises at least one monomer Anionic polymer containing a carboxylate function that is a salt of acrylic acid. Advantageously, the PI polymer contains at least sodium acrylate as a monomer unit.

[0032] According to a preferred embodiment, the PI polymer comprises at least one hydrophobic monomer selected from the haloalkylated derivatives of methacrylamido-dimethyl aminopropyl comprising a C8-Ci6 alkyl chain, ethoxylated behenyl methacrylate, diethylacrylamide, n-tert-butylacrylamide, and mixtures thereof.

[0033] In a preferred embodiment of the invention, the water-soluble polymer PI does not contain a monomer unit possessing a sulfonic acid function or its salts, such as acrylamido tert-butyl sulfonic acid (ATBS), allyl sulfonic acid or methallyl sulfonic acid.

[0034] Advantageously, the water-soluble polymer PI contains less than 50 mol% of anionic monomer(s), preferably between 10 and 40 mol%, more preferably between 15 and 30 mol%.

[0035] Advantageously, if present, the non-ionic monomer(s) may be chosen, in particular, from the group comprising water-soluble vinyl monomers. The non-ionic monomer(s) are chosen, for example, from the group containing acrylamide, methacrylamide, N-vinylformamide (NVF), N-vinyl acetamide, N-vinylpyridine, N-vinylpyrrolidone (NVP), N-vinyl imidazole, N-vinyl succinimide, acryloyl morpholine (ACMO), acryloyl chloride, glycidyl methacrylate, glyceryl methacrylate, acrylamide diacetone, hydroxyalkyl (meth)acrylates (the alkyl group advantageously being in Ci-C3), aminoalkyl (meth)acrylates (the alkyl group advantageously being in Ci-C3), aminoalkyl (meth)acrylamido (the alkyl group advantageously being in Ci-C3), thioalkyl (meth)acrylate (the alkyl group advantageously being in CrC3) and mixtures thereof.Preferably, at least one non-ionic monomer of the PI polymer is acrylamide.

[0036] The PI polymer advantageously comprises at least 50 mol%, preferably between 60 and 90 mol%, and even more preferably between 70 and 85 mol% of at least one non-ionic monomer.

[0037] Preferably, the PI polymer is a copolymer of acrylamide and sodium acrylate, which preferably comprises between 10 and 40 mol% and even more preferably between 15 and 30 mol% of sodium acrylate, the total sum of the two monomers being preferably equal to 100% of the PI polymer.

[0038] The PI polymer can be linear or structured. By "structured polymer," we mean a non-linear polymer that has side chains arranged in such a way that, when dissolved in water, it becomes highly enmeshed, leading to very high low-gradient viscosities. The structuring can This can result from the presence of at least one polyethylenic unsaturation monomer (i.e., one with at least two unsaturated carbon=carbon groups), such as vinyl, allylic, acrylic, and epoxy groups. Examples include sodium allyl sulfonate, sodium methyl sulfonate, sodium methyl disulfonate, methylenebisacrylamide, diallylamine, triallylamine, triallylammonium chloride, and tetraallylammonium chloride. Structuring can also be achieved with at least one macroinitiator, such as a polyperoxide or polyazole, or with at least one polytransfer agent, such as a polymercaptan.

[0039] The PI polymer can also be structured using controlled radical polymerization (CRP) techniques, and more particularly, RAFT (Reversible Addition Fragmentation Chain Transfer) type techniques.

[0040] The PI polymer can be structured in the form of a comb, a star, or any other structure known to those skilled in the art. The structured PI polymer remains water-soluble.

[0041] Advantageously, the PI polymer is structured in the form of a star, that is to say, it has a central part (called the core) and polymer-based arms extending radially from said central part.

[0042] According to the invention, the PI polymer is in the form of solid particles, with a median size in number of solid particles (D50) generally greater than 500 micrometers (pm).

[0043] The PI polymer is obtained by a gel polymerization process of at least one non-ionic or anionic monomer in the presence of: - of at least 1% by weight of a P3 polymer, said P3 polymer containing at least 10% by weight of at least one hydrophobic monomer, and / or - of at least 1% to 20% by weight of at least one hydrophobic monomer.

[0044] By "A and / or B", according to the invention, means either A, or B, or A and B.

[0045] The gel polymerization of the process of the invention is carried out by radical polymerization. This includes free radical polymerization using UV, azo, redox or thermal initiator(s), as well as controlled radical polymerization (CRP) techniques and more particularly RAFT type.

[0046] At least one transfer agent may be used. It may, in particular, be selected from sulfur compounds such as thioglycolic acid, a mercaptoalcohol, or dodecyl mercaptan; amines such as ethanolamine, diethanolamine, or morpholine; and phosphites such as sodium hypophosphite. In the case of RAFT-type polymerization, one or more specific polymerization regulators, such as those comprising a transfer group including the -S-CS- function, may be used. Examples include compounds from the xanthate family. (-S-CS-O-), dithioesters (-S-CS-Carbon), trithiocarbonates (-S-CS-S-), or dithiocarbamates (-S-CS-Nitrogen). Among the compounds in the xanthate family, O-ethyl-S-(l-methoxy carbonyl ethyl) xanthate can be advantageously used due to its compatibility with acrylic monomers.

[0047] The polymerization initiator(s) used to obtain the PI polymer can be any compound that dissociates into radicals under the polymerization conditions, such as, for example: organic peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds, and redox catalysts. The use of water-soluble initiators is preferred. In some cases, it is advantageous to use mixtures of various polymerization initiators, for example, mixtures of redox catalysts and azo compounds.

[0048] Said polymerization initiators are used in usual quantities, for example in quantities that can vary from 0.0001 to 2%, preferably from 0.001 to 1% by weight, relative to the monomers to be polymerized.

[0049] As an oxidizing component, redox catalysts advantageously contain at least one of the aforementioned compounds. As a reducing component, redox catalysts are advantageously selected from ascorbic acid, glucose, sorbose, hydrogen sulfite, sulfite, thiosulfate, hyposulfite, pyrosulfite, an alkali metal, metal salts, such as iron(II) ions or silver ions, or sodium hydroxymethylsulfoxylate. The reducing component of the redox catalyst preferably used is Mohr's salt (NH₄Fe₂O₆·6H₂O).

[0050] Based on the quantity of monomers used in the polymerization, 5 x 10⁶ to 1 mol% of the reducing component of the redox catalyst system and 5 x 10⁵ to 2 mol% of the oxidizing component of the redox catalyst may, by way of example, be used. Instead of the oxidizing component of the redox catalyst, one or more water-soluble azo initiators may also be used.

[0051] The polymerization of the water-soluble PI polymer is carried out in the absence of oxygen by introducing the initiators in the appropriate order, known to those skilled in the art, into the solution to be polymerized. The initiators are introduced either in soluble form in an aqueous medium or as a solution in an organic solvent.

[0052] All constituents are advantageously solubilized, more advantageously in water.

[0053] As soon as polymerization begins, the reaction mixture is heated or warms up (exothermic reaction) depending on the initial conditions. Advantageously, due to the heat of polymerization released, the temperature of the reaction mixture rises from 80 to 150°C, preferably from 80 to 100°C. Polymerization is advantageously carried out at atmospheric pressure. A person skilled in the art knows how to select the appropriate equipment for optimal polymerization.

[0054] At the end of the polymerization reaction, the PI polymer gel is aged generally for at least 60 minutes.

[0055] By "aging" we mean leaving the gel in the polymerization reactor at the final polymerization temperature.

[0056] The polymerization product is generally a viscous PI polymer gel that is subsequently granulated. Granulation consists of cutting the gel into small pieces. According to the present invention, advantageously, the average size of these gel pieces is less than 1 cm, more advantageously between 4 and 8 mm. A person skilled in the art knows how to choose the appropriate method for optimal granulation. The next step consists of grinding these gel pieces. The grinding step consists of breaking the large polymer particles into smaller particles. This can be done by shearing or by mechanically crushing the particle between two hard surfaces.Various types of equipment familiar to those skilled in the art can be used for this purpose, such as rotor mills, where the particle is crushed against a compression blade by the rotating part, or roller mills, where the particle is crushed between two rotating rollers. The sieving that follows milling then aims to remove, according to specifications, particles of average size that are too small or too large. The next step is to dry the PI polymer. The drying method and its conditions (duration and temperature) are routine choices for those skilled in the art. Industrially, drying is advantageously carried out using fluidized bed or rotor dryers, preferably with air heated to a temperature between 70°C and 200°C, the air temperature depending on the nature of the product and the drying time applied. The PI polymer is then in powder form.

[0057] Preferably, according to one aspect of the invention, the PI polymer is characterized in that it is obtained by a gel polymerization process known to those skilled in the art, in the presence of at least 1% by weight of a P3 polymer, said P3 polymer containing at least 10% by weight of at least one hydrophobic monomer. In addition to the hydrophobic monomer(s), the P3 polymer may comprise at least one hydrophilic monomer. In this case, the PI polymer then forms part of a composition including the PI polymer and the P3 polymer.

[0058] The hydrophilic monomer(s) of polymer P3 have a partition coefficient Kow of less than 1 and are preferably chosen from the group containing acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkylacrylates, hydroxyalkyl methacrylates, and mixtures thereof; monomers possessing a carboxylic acid function and their salts, including acrylic acid, methacrylic acid, itaconic acid, and maleic acid; monomers possessing a sulfonic acid function and their salts, including acrylamido tert-butylsulfonic acid (ATBS), allylsulfonic acid, and methallylsulfonic acid, and their salts; monomers having a phosphonic acid function and their salts; and mixtures thereof. Generally, monomer salts are salts of at least one alkali metal (preferably sodium), at least one alkaline earth metal (preferably calcium or magnesium), or at least one ammonium compound (preferably a quaternary ammonium compound).

[0059] The hydrophobic monomer(s) of polymer P3 have a partition coefficient Kow greater than 1 and are preferably chosen from the compounds in the following list: - (meth)acrylic acid esters having an alkyl and / or arylalkyl and / or ethoxylated and / or propoxylated chain; (meth)acrylamide derivatives having an alkyl and / or arylalkyl and / or dialkyl and / or ethoxylated and / or propoxylated chain; cationic allyl derivatives having an alkyl and / or arylalkyl and / or dialkyl and / or ethoxylated and / or propoxylated chain; hydrophobic anionic or cationic derivatives of (meth)acryloyl; and monomeric anionic or cationic derivatives of (meth)acrylamide bearing a hydrophobic chain; - n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, n-tert-butyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyle (meth)acrylate, myristyle (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, erucyl (meth)acrylamide, erucyl (meth)acrylamide, and their combinations; - hydrophobic monomers corresponding to the general formula CH2=CR1-COO-(EO)n-(PO)m-R2 in which R1 is a hydrogen or a methyl; n is a number at least equal to two, preferably between 6 and 100, even more preferably between 10 and 40; m is a number between 0 and 50, preferably between 0 and 20, EO is an ethylene oxide group (-CH2-CH2-O-), PO is a propylene oxide group (-CH2-CH(CH3)-O-) and R2 is a C8-C30 alkyl group or a C8-C30 arylalkyl group, and n+m being preferably from 6 to 100 or from 10 to 40. These are preferably linear alkyls.

[0060] Among hydrophobic P3 monomers having an alkyl chain, particularly (meth)acrylic acid esters, (meth)acrylamide derivatives, and cationic allyl derivatives, the alkyl groups are advantageously in the C1-C5 position, more advantageously in the C1-C3 position. These are preferably linear alkyls. A dialkyl group It therefore comprises two alkyl groups advantageously at C1-C5. The arylalkyl groups of these monomers are advantageously at C8-C30.

[0061] More preferably, the hydrophobic monomers of P3 are chosen from the compounds in the following list: haloalkylated (preferably bro-moalkylated) derivatives of methacrylamidodimethyl aminopropyl comprising a C8-Ci6 alkyl chain, ethoxylated behenyl methacrylate, diethylacrylamide, n-tert-butylacrylamide and mixtures thereof.

[0062] The P3 polymer contains between 10 and 100% by weight, and even more preferably between 10 and 90% by weight, of at least one hydrophobic monomer.

[0063] Advantageously, the P3 polymer is a terpolymer of diethylacrylamide, n-tert-butylacrylamide and sodium 2-acrylamido-2-methylpropanesulfonate.

[0064] In a preferred embodiment, the polymer P3 is functionalized at the end of its polymer chain by at least one group selected from: hydroxyl, cyano, amine, phosphate, phosphonate, sulfate, sulfonate, xanthate, trithiocarbonate, dithiocarbamate, and dithioester. The polymer P3 may also be free of chain functionalization.

[0065] Preferably, the P3 polymer is free of any carbon-carbon double bonds.

[0066] According to this aspect of the invention, the PI polymer is obtained under the following conditions: - Preparation of an aqueous solution of polymer PI comprising between 1 and 25% by weight, advantageously between 2 and 20% by weight, and even more advantageously between 3 and 15% by weight, of polymer P3, the percentage being expressed by weight relative to the total weight of the aqueous solution. The polymer P3 contains the monomers selected from the list described above; water; and optionally additives, the total mass concentration of monomers being between 10 and 60%, advantageously between 20 and 55%, and even more advantageously between 25 and 50%, by weight relative to the total weight of the aqueous solution. The polymerization compounds are dissolved, for example, by stirring, in the aqueous medium to be polymerized. This solution, also called the polymerization feedstock, is adjusted to an initiation temperature between -20°C and 50°C. Advantageously this initiation temperature is adjusted between -5°C and 30°C, and even more advantageously between 0 and 20°C.A person in the field knows how to define the pH to be achieved as well as the quantity and choice of pH regulators according to the chemistry of the polymer to be synthesized, in particular according to the nature of the monomers (non-ionic, anionic...). - Degassing after dissolution to eliminate any trace of residual oxygen, using at least one inert gas. The inert gas is usually passed through the solution. Suitable inert gases for this purpose are, for example, nitrogen, carbon dioxide, or Noble gases such as neon or helium. Argon can also be used.

[0067] The hydrophilic monomers present in polymer P3 can promote the solubilization of polymer P3 in water, even when it consists mainly of hydrophobic monomers. In this case, the hydrophilic monomers act as a co-solvent for polymer P3. Thus, the polymerization solution is free of insolubles. Generally, polymer P1 is water-soluble, while polymer P3 is not necessarily so.

[0068] According to a second aspect of the invention, the PI polymer is obtained by a gel polymerization process in the presence of at least 1% by weight of at least one hydrophobic monomer. In this specific case, the PI polymer, in addition to its anionic and / or non-ionic water-soluble monomer(s) described above, comprises at least one hydrophobic monomer.

[0069] The hydrophobic monomers are generally chosen from the same list of hydrophobic monomers as that cited above for the P3 polymer. To this end, preferably, 1 to 20% of at least one hydrophobic monomer is introduced into the PI polymerization feedstock. However, preferably, the P3 polymer does not contain any cationic or zwitterionic monomers.

[0070] According to this aspect of the invention, optionally, this or these hydrophobic monomers are brought into contact with one or more surfactants.

[0071] A "surfactant" is an agent capable of emulsifying an oil in water. Generally, a surfactant is considered to be a compound having an HLB greater than or equal to 10.

[0072] The hydrophilic-lipophilic equilibrium (HLB) of a chemical compound is a measure of the degree to which it is hydrophilic or lipophilic, determined by calculating the values ​​of the different regions of the molecule, as described by Griffin in 1949. Griffin assigned a dimensionless number between 0 and 20 to provide information on solubility in water and oil. Substances with an HLB value of 10 are distributed between the two phases such that the hydrophilic group (molecular mass Mh) is completely projected into the water while the hydrophobic group (molecular mass Mp) is adsorbed into the non-aqueous phase. The HLB value of a substance having a total molecular mass M and a hydrophilic portion of molecular mass Mh is given by: HLB = 20 (Mh / Mp)

[0073] The surfactant can be any suitable surfactant selected from anionic surfactants, cationic surfactants, nonionic surfactants, and a combination thereof. In some embodiments, the surfactant(s) may exist in dimer form. For example, the surfactant may comprise one polar head group and two nonpolar tail groups, or two polar head groups and a nonpolar tail group, or two polar head groups and two nonpolar tail groups. The surfactant or mixture of surfactants may be selected from the following list: ethoxylated sorbitan esters such as ethoxylated sorbitan oleate with 20 moles of ethylene oxide (EO210), sorbitan laurate with 20 moles of ethylene oxide, or ethoxylated sorbitan monostearate with 20 moles of ethylene oxide; decaethoxylated oleodecyl alcohol; heptaethoxylated lauryl alcohol; ethoxylated castor oil with 40 moles of ethylene oxide; polyethoxylated alkyl phenols; polyethoxylated cetyl ethers; quaternary amine derivatives; sodium lauryl sulfate; the condensation products of fatty alcohols with ethylene oxide; the condensation products of alkyl phenols with ethylene oxide; the condensation products of amino fatty acids with 5 or more units of ethylene oxide; tristerylphenol ethylene oxide; an alkyl polyglucoside;an amine oxide, a glucamide; a salt of alkylbenzenesulfonic acid, a water-soluble surfactant polymer. Preferably, less than 10 wt% of surfactants are added to the polymerization charge.

[0074] According to a third aspect of the invention, the PI polymer is obtained by a gel polymerization process of at least one non-ionic or anionic monomer in the presence of at least 1% by weight of a P3 polymer and at least 1% to 20% by weight of at least one hydrophobic monomer as described above, in which case the final composition includes PI and P3 and in which case PI contains at least one hydrophilic monomer and at least one hydrophobic monomer. P2 Polymer

[0075] The binding composition according to the invention comprises, in addition to the PI polymer, a nonionic or anionic water-soluble synthetic polymer P2 with a weight-average molecular weight greater than 2 million (2 x 10⁶) Daltons. The water-soluble polymer P2 more preferably has a weight-average molecular weight greater than 5 million Daltons. The water-soluble polymer P2 generally has a weight-average molecular weight less than 40 million Daltons. The polymer P2 comprises at least one nonionic or anionic monomer.

[0076] Preferably, the P2 polymer has a weight average molecular weight greater than the weight average molecular weight of the PI polymer.

[0077] The non-ionic and anionic monomers are preferably chosen from the same compounds mentioned above for PI. Advantageously, the anionic monomer(s) can be salified as previously described.

[0078] Preferably, the water-soluble polymer P2 contains between 5% and 100 mol%, more preferably between 10% and 70 mol%, and even more preferably between 20% and 50% mol%, of at least one anionic monomer.

[0079] Advantageously, the water-soluble polymer P2 does not contain a monomer unit possessing a sulfonic acid function or their salts, such as acrylamido tert-butyl sulfonic acid (ATBS), allyl sulfonic acid and methallyl sulfonic acid.

[0080] The polymer P2 is linear or structured. The polymer P2 can be structured as described above for PI. The structured polymer P2 remains water-soluble.

[0081] The P2 polymer is present in the form of solid particles, for example as a powder or microbeads. The P2 polymer powder can be obtained by gel polymerization, precipitation polymerization, or aqueous solution polymerization followed by drum drying, spray drying, or radiation drying such as microwave drying or fluidized bed drying. The powder form can also be obtained by water-in-oil emulsion polymerization (inverse emulsion), followed by a distillation / concentration step and spray drying of the resulting liquid.

[0082] The P2 polymer microbeads are advantageously obtained by reverse suspension polymerization.

[0083] Preferably, the polymer P2 is in the form of a powder resulting from a gel polymerization or of microbeads resulting from a reverse suspension polymerization.

[0084] According to the invention, the P2 polymer is in the form of solid particles, such that the median number size of the solid particles (D50) is greater than 500 micrometers (pm).

[0085] In a particularly preferred manner, the P2 polymer is a copolymer containing between 5 and 100% by moles of sodium acrylate. Binder composition according to the invention

[0086] For the purpose of agglomerating ores at low temperature, the binding composition according to the invention comprises at least two polymers having the function of distinct organic binding agents: PI and P2.

[0087] According to a preferred embodiment of the invention, the binding composition contains at least 50% by weight of PI polymer.

[0088] According to a preferred embodiment of the invention, the binding composition contains only the two distinct organic binding agents PI and P2. According to this preferred embodiment, the binding composition preferably contains between 75 and 90% by weight of polymer PI and between 10 and 25% by weight of polymer P2. The sum of the weight amounts of P1+P2 is equal to 100%.

[0089] According to another embodiment of the invention, the binding composition may also contain at least one other constituent of a different nature, allowing the physical properties of the agglomerates to be increased and the binding power of said composition to be improved even further.

[0090] One of these constituents may be an organic binding agent other than PI and P2, by For example, an epoxy, polyphenolic, or formaldehyde resin. Rolkem™ brand resins are preferred.

[0091] Thus, according to another aspect of the invention, the binding composition comprises less than 40% by weight of PI polymer, between 1 and 25% by weight of P2 polymer and at least 50% by weight of another organic binding agent other than PI and P2, the sum of the quantities by weight of the components being equal to 100%.

[0092] The binding composition may also include an inorganic binding agent, advantageously in the form of solid particles, hereinafter referred to as LI. The inorganic binding agent LI may be selected from sodium carbonate, sodium bicarbonate, sodium phosphate, sodium silicate, urea, calcium oxide, bentonite, and mixtures thereof. A preferred inorganic binding agent LI is sodium silicate. According to the invention, the binding agent LI may be in the form of solid particles, such that the median size of the solid particles (D50) is between 500 and 5000 micrometers, more preferably between 500 and 2000 micrometers.

[0093] Thus, according to an alternative embodiment of the invention, the binding composition comprises at least 50% by weight of inorganic binding agent LI, between 10% and 49% by weight of polymer PI and between 0.5 and 5% by weight of polymer P2, the sum of the quantities by weight of P1+P2+LI being equal to 100%.

[0094] Another embodiment of the invention relates to a binding composition containing between 10 and 40% by weight of inorganic binding agent LI, between 5 and 20% by weight of polymer PI, at least 50% by weight of an organic binding agent other than PI and P2 and less than 5% by weight of polymer P2, the sum of the quantities by weight of the components being equal to 100%.

[0095] The binding composition according to the invention is formed by mixing its constituents, each of them being in powder form.

[0096] The binding composition particularly preferably contains less than 0.1% by weight of sulfur element. Agglomerations

[0097] The last aspect of the invention relates to ore agglomerates advantageously containing between 2,000 and 50,000 ppm of binding composition relative to the weight of said ore agglomerates.

[0098] These agglomerates are generally formed by adding the binding composition to the crushed ores while stirring, in the presence of a small amount of water to form a wet mixture. The mixture is then agglomerated using the preferred agglomeration technique (pelletizing, sintering, nodulizing, extrusion, or briquetting). The agglomerates thus obtained are then baked in a furnace at a temperature not exceeding 250°C.

[0099] Said agglomerates may undergo further additional physical and / or chemical treatments according to the desired application, as is known to those skilled in the art. Examples

[0100] The following examples illustrate the advantages of the invention in a clear and non-limiting manner. I. Synthesis of a PI polymer:

[0101] Example 1: Synthesis in aqueous liquid process of a low molecular weight acrylamide homopolymer: Pla (counterexample)

[0102] The Pla polymer is synthesized by an aqueous liquid radical polymerization process from an aqueous feed comprising 40.0 wt% acrylamide monomers according to the following protocol: in a 1 L double-jacketed reactor, 133 g of water and 6 g of sodium hypophosphite are introduced in the following order. The pH of the aqueous phase is adjusted to a pH value between 2.0 and 3.0 using a dilute sulfuric acid solution. The feed is then heated to a temperature between 79 and 81 °C using the double jacket. When the aqueous feed is at temperature, 800 g of a 50 wt% acrylamide solution in water is poured over a period of 120 minutes. In parallel, a 6.5 wt% sodium persulfate solution in water is poured over a period of 130 minutes.Once the sodium persulfate pouring is complete, the mixture is left to react for 1 hour at the same temperature to reduce the amount of residual monomers. The resulting PLA polymer is a viscous liquid containing 40% polymer by weight. The PLA polymer has a molecular mass of 100,000 Daltons.

[0103] Example 2: Gel synthesis of an acrylamide / sodium acrylate copolymer Pib, by adding to the polymerization charge 5% by weight of polymer P3 containing 15% by weight of hydrophobic monomer: Pib (invention)

[0104] In a first step, a composition with a concentration of 13.8% by weight, containing: is synthesized by radical polymerization. - The P3 polymer has the following composition by weight: 15% n-tert-butylacrylamide, 39% diethylacrylamide, 8% sodium 2-acrylamido-2-methylpropanesulfonate, as well as, - 38% acrylamide.

[0105] In a second step, the Pib polymer is synthesized by a gel radical polymerization process from an aqueous feed comprising 5% by weight of the composition according to the following protocol: in a 1.5 L beaker, 50 g of the composition (360 g of aqueous solution at 13.8% by weight of composition) are introduced, 79 g of acrylic acid, 403 g of acrylamide at 50% by weight in water, and 70 g of sodium chloride. The feed is neutralized using 87 g of sodium hydroxide at 50% by weight in water to achieve a pH between 6.5 and 7.5. The feed is then cooled to 0°C before being placed in a Dewar flask. 1.5 g of azobisisobutyronitrile is then added to the feed, which is then homogenized using a hand mixer at 500 rpm for 20 seconds before being degassed under nitrogen bubbling for 20 minutes.

[0106] 0.3 g of sodium hypophosphite and 3.8 mg of diethylenetriaminepentaacetic acid (DTPA) are then added to the feedstock. The reaction is initiated by successive additions of 1.4 mg of sodium persulfate and then 8.2 mg of Mohr's salt. The reaction time is 60 minutes, with a final temperature of 94°C. The resulting Pib polymer is in gel form. Consequently, it can be granulated and then dried in an air stream at 70°C for 60 minutes. The dry Pib polymer grains are then ground to obtain a powder with a particle size of less than 1.7 mm. The resulting Pib polymer is 100% water-soluble and has a molar mass of 1,250,000 Da. II. Synthesis of a P2 polymer:

[0107] Example 3: Synthesis of polymer P2a (counterexample)

[0108] The P2a polymer is synthesized by a gel radical polymerization process from an aqueous feed comprising 30.6 wt% monomers according to the following protocol: 79 g of acrylic acid, 403 g of acrylamide at 50 wt% in water, and 70 g of sodium chloride are introduced into a 1.5 L beaker. The feed is neutralized using 87 g of sodium hydroxide at 50 wt% in water to achieve a pH between 6.5 and 7.5. The feed is then cooled to 0°C before being placed in a Dewar flask. 1.5 g of azobisisobutyronitrile are then introduced into the load which is then homogenized using a hand mixer at a speed of 500 rpm for 20 seconds before being degassed under nitrogen bubbling for 20 minutes.

[0109] 0.23 g of sodium hypophosphite and 3.8 mg of diethylenetriaminepentaacetic acid (DTPA) are then added to the feedstock. The reaction is initiated by successive additions of 1.4 mg of sodium persulfate and then 8.2 mg of Mohr's salt. The reaction time is 60 minutes, with a final temperature of 94°C. The resulting P2a polymer is in gel form. Consequently, it can be granulated and then dried in an air stream at 70°C for 60 minutes. The dry P2a polymer grains are then ground to obtain a powder with a particle size of less than 1.7 mm. The resulting P2a polymer is 100% water-soluble and has a molar mass of 1,800,000 Da.

[0110] Example 4: Synthesis of polymer P2b (invention)

[0111] The P2b polymer is synthesized by a gel radical polymerization process from an aqueous feed comprising 30.0 wt% monomers according to the following protocol: 65 g of acrylic acid, 430 g of acrylamide at 50 wt% in water, and 70 g of sodium chloride are introduced into a 1.5 L beaker. The feed is neutralized with 72 g of sodium hydroxide at 50 wt% in water to achieve a pH between 6.5 and 7.5. The feed is then cooled to 0°C before being placed in a Dewar flask. 1.5 g of azobisisobutyronitrile are then introduced into the load which is then homogenized using a hand mixer at a speed of 500 rpm for 20 seconds before being degassed under nitrogen bubbling for 20 minutes.

[0112] 20 mg of sodium hypophosphite and 3.8 mg of diethylenetriaminepentaacetic acid (DTPA) are then added to the feedstock. The reaction is initiated by successive additions of 1.4 mg of sodium persulfate and then 8.2 mg of Mohr's salt. The reaction time is 60 minutes, with a final temperature of 94°C. The resulting P2b polymer is in gel form. Consequently, it can be granulated and then dried in an air stream at 70°C for 60 minutes. The dry P2b polymer grains are then ground to obtain a particle size of less than 1.7 mm. The resulting P2b polymer is 100% water-soluble and has a molar mass of 12,000,000 Da. III. Manufacturing of agglomerates

[0113] In the following examples, iron ore agglomerates are prepared using the binding composition as described in this application, the exact compositions and quantities being shown in Table 2. Compositions according to the invention (“invention”) and counterexample compositions (“CEx”), which are outside the scope of the invention, are also prepared. The quantities of binding agents (as weight percentages) shown in Table 2 are based on the total weight of the iron ore concentrate. The iron ore concentrate used in the examples in Table 2 is a hematite ore concentrate.

[0114] Table 1 below shows the nature of the elements that may be present in the binding composition.

[0115] [Tables 1] Pl-a (CEx) Pi-b (Invention) P2-a (CEx) P2-b (Invention) Lî-I (Invention) Compound Organic Inorganic Nature Polymeric Sodium silicate Molecular Weight 100,000 1,250,000 1,800,000 12(100,000 Atüoniciié 0 28 23 28 ;

[0116] Table 1: Organic and inorganic bonding agents.

[0117] To prepare said agglomerates, the binding composition is first mixed into the dry ore concentrate and homogenized with the required amount of water (moisture content between 2 and 5% by weight). The ore concentrate is mixed with the binding composition using a KitchenAid® type mixer (up to 3 kg of concentrate) and a Hobart type mixer (over 3 kg of concentrate).

[0118] After a mixing time of between 2 and 4 minutes, the ore concentrate is deposited into the inlet hopper of a tangential roller compactor, which may be of the SAHUT-CONREUR, EURAGGLO, or KOMAREK brand. The finished agglomerates, with sizes between 3.5 and 4.5 cm and volumes between 8 and 10 cm³, are collected at the compactor outlet. These agglomerates are placed in an oven at 105°C for 2 to 4 hours to dry them completely (the higher the concentration of inorganic binding agents, the longer the drying time must be).

[0119] The number of falls and the dry strength of the agglomerates obtained were measured for each case, the results being gathered in Table 2.

[0120] As detailed in Table 2, various comparative binding compositions (CEx 1 to CEx 10) and according to the invention (C1 to C5) were prepared. They all consist of an inorganic binding agent LI and two organic binding agents, which are the previously synthesized polymers PI and P2. In each case, the binding composition is prepared by assembly via a mixing process that homogenizes the three components.

[0121] The manufacturing process for ore agglomerates is generally known to those skilled in the art. Various green ore agglomerates were manufactured to test different binding compositions. Number of wet falls (NCH)

[0122] The wet drop number was determined by repeatedly dropping an agglomerate from a height of 46 cm onto a horizontally placed steel plate until a visible crack formed on the surface of the granule. The number of times required for the dropped granule to reach its fracture / cracking point was determined. This measurement was determined for 20 granules. The average of these 20 measurements is called the "wet drop number" (WDN). Dry compressive strength (RCS)

[0123] 20 green granules of sizes between 3.5 and 4.5 cm for volumes between Between 8 and 10 cm³, the pellets were placed in an oven at 105°C for 2 to 4 hours to dry them completely. After drying, the pellets were placed one by one in a standard SCAINE measuring device. The maximum force applied at which the pellet cracked was determined. The average of these 20 measurements is called "dry compressive strength" (DCS).

[0124] [Tables2] Tests Dry Concentrate (g) Water (g) Binder Composition Components (g) Physical Appearance of Agglomerates NCH RCS (kg) PI-a Pl-b P2-a P2-b LI Cl 9800 100 0 90 0 10 0 Good, strong, plastic 10 380 C2 9839 100 0 45 0 15 0 Good, strong, plastic 8 440 C3 9870 80 0 40 0 ​​10 0 Good, strong, plastic 5.5 357 C4 9700 150 0 45 0 5 100 Good, strong, plastic 6.5 > 500 CEx 1 9800 100 0 100 0 0 0 Formed, weak 3 125 CEx 2 9800 100 0 90 10 0 0 Formed, low resistance 3.5 135 CEx 3 9800 100 90 0 0 10 0 Formed, low resistance 5 170 CEx 4 9800 100 90 0 10 0 0 Formed, low resistance 4 165 CEx 5 9800 100 100 0 0 0 0 Formed, low resistance 3 115

[0125] Table 2: Quantity of binding agent and ores per agglomerate, measurements of the physical properties of said agglomerates.

[0126] The cold agglomeration application requires that the agglomerates have a dry hardness greater than 250 kg in order to allow the manufacturer to add these agglomerates directly in very high temperature furnaces (blast furnaces and electric furnaces).

[0127] Table 2 highlights that the agglomerates of examples Cl to C4, which use the binding compositions according to the invention, are better compacted and their strength is greater than the agglomerates of comparative tests CEx 1 to CEx 5.

[0128] Effective compaction results in a surface finish for the agglomerates that is very important for the manufacturer, as the cavities of the compaction wheels will not be clogged by fresh, uncompacted material. Furthermore, good compaction prevents granular and / or uneven surfaces, which increase abrasion resistance, leading to a reduction in the marketable size of the granules and an increase in dust content in the kiln and during handling. The strength and plasticity of the agglomerates prevent breakage and thus reduce tumbling resistance.

[0129] The dry compressive strength for the tests of the binder compositions according to the invention Cl to C4 is improved compared to the tests of the comparative binder compositions CEx 1 to CEx 5. This parameter is crucial for manufacturers because it allows them to understand the behavior of the agglomerates in very high-temperature furnaces: Increased dry compressive strength will prevent broken agglomerates from forming in the columns of blast furnaces and / or electric furnaces, thus avoiding a decrease in productivity due to the presence of excessive fines levels.

[0130] The number of agglomerate falls is also very important for the application of cold agglomeration in order to avoid any breakage of the agglomerates before complete drying, which would lead to an increase in fine particles and a decrease in the dry strength of the agglomerates.

[0131] Comparatively, the comparative binder compositions Cl, C2, and C3 allow for obtaining the values ​​required by the cold agglomeration application. It is also observed that the choice of molecular weights of the PI and P2 polymers is important for achieving good physical properties. The binder compositions according to the invention demonstrate their effectiveness even at lower dosages, which is important for manufacturers because it reduces the logistics and production costs of agglomerates via the cold agglomeration process.

[0132] Tests of comparative binding compositions CEx 1 to CEx 5 demonstrate that it is essential to work with the binding compositions of the invention of the PI and P2 polymers.

Claims

Demands

1. Binder composition, for the manufacture of ore agglomerates, comprising at least the following two distinct organic binding agents: - a non-ionic or anionic water-soluble synthetic polymer PI of weight average molecular weight between 500,000 and 3 million Daltons, - a non-ionic or anionic water-soluble synthetic polymer P2 of weight average molecular weight greater than 2 million Daltons, both polymers PI and P2 being in the form of solid particles, PI being obtained by a gel polymerization process of at least one non-ionic or anionic monomer in the presence of at least 1% by weight of a polymer P3, said polymer P3 containing at least 10% by weight of at least one hydrophobic monomer.

2. Binder composition according to claim 1, characterized in that said binder composition contains at least 50% by weight of PI polymer.

3. Binder composition according to any one of the preceding claims, characterized in that the PI polymer contains at least 50 mole percent of at least one non-ionic monomer.

4. Binder composition according to any one of the preceding claims, characterized in that the PI polymer is non-ionic.

5. Binder composition according to any one of claims 3 or 4, characterized in that the non-ionic PI monomer(s) are selected from the group containing acrylamide, methacrylamide, N-vinylformamide (NVF), N-vinyl acetamide, N-vinylpyridine, N-vinylpyrrolidone (NVP), N-vinyl imidazole, N-vinyl succinimide, acryloyl morpholine (ACMO), acryloyl chloride, glycidyl methacrylate, glyceryl methacrylate, acrylamide diacetone, hydroxyalkyl (meth)acrylates, aminoalkyl (meth)acrylates, aminoalkyl (meth)acrylamido, thioalkyl (meth)acrylate and mixtures thereof.

6. Binder composition according to any one of claims 3 to 5, characterized in that at least one non-ionic monomer of the PI polymer is acrylamide.

7. Binder composition according to any one of claims 1 to 3, characterized in The PI polymer is a copolymer of acrylamide and sodium acrylate.

8. Binder composition according to any one of the preceding claims, characterized in that the PI polymer comprises at least one hydrophobic monomer selected from the haloalkylated derivatives of methacrylami-dodimethyl aminopropyl comprising a C8-Ci6 alkyl chain, ethoxylated behenyl methacrylate, diethylacrylamide, n-tert-butylacrylamide, and mixtures thereof.

9. Binder composition according to any one of the preceding claims, characterized in that the P3 polymer contains between 10 and 90% by weight of at least one hydrophobic monomer.

10. Binder composition according to any one of the preceding claims, characterized in that the P3 polymer is a terpolymer of diethylacrylamide, n-tert-butylacrylamide and sodium 2-acrylamido-2-methylpropanesulfonate.

11. Binder composition according to any one of the preceding claims, characterized in that the P3 polymer is functionalized at the polymer chain end by at least one group selected from: hydroxyl, cyano, amine, phosphate, phosphonate, sulfate, sulfonate, xanthate, tri-thiocarbonate, dithiocarbamate, and dithioester.

12. Binder composition according to any one of the preceding claims, characterized in that the P3 polymer is free of carbon-carbon double bonds.

13. Binder composition according to any one of the preceding claims, characterized in that the P2 polymer is a copolymer containing between 5 and 100% by moles of sodium acrylate.

14. Binder composition according to any one of the preceding claims, characterized in that the P2 polymer has a weight average molecular weight greater than the weight average molecular weight of the PI polymer.

15. Ore agglomerates containing between 2,000 and 50,000 ppm of binder composition according to any one of the preceding claims, relative to the weight of the ore agglomerates.