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WO2025010348A2 - Préparation d'un dpam à température de réaction élevée présentant une viscosité standard et une solubilité aqueuse améliorées - Google Patents

Préparation d'un dpam à température de réaction élevée présentant une viscosité standard et une solubilité aqueuse améliorées Download PDF

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WO2025010348A2
WO2025010348A2 PCT/US2024/036757 US2024036757W WO2025010348A2 WO 2025010348 A2 WO2025010348 A2 WO 2025010348A2 US 2024036757 W US2024036757 W US 2024036757W WO 2025010348 A2 WO2025010348 A2 WO 2025010348A2
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redox
acid
polymerization
reaction temperature
acrylamide
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WO2025010348A3 (fr
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Susanna HOLAPPA
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Kemira Oyj
Kemira Water Solutions Inc
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Kemira Oyj
Kemira Water Solutions Inc
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00—Polymerisation catalysts
    • C08F4/04—Azo-compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
    • C08F2/40—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation using retarding agents

Definitions

  • the present invention generally relates to compositions and methods for preparation of high reaction temperature dry polyacrylamide (DPAM) polymers.
  • the disclosure provides methods for adiabatic redox initiated free-radical polymerization of reaction mixtures comprising at least acrylamide monomers, optional free-radical scavenger stabilizers, azo initiators, and redox initiators under pH and initial temperature conditions that allow heat of polymerization to increase reaction temperatures to above 100 °C (Tmax > 100 °C). Gel polymerization under these conditions produces anionic DPAM polymers for use in variety of industrial applications with improved standard viscosity and high water-solubility
  • Polyacrylamide homopolymers and copolymers having high molecular weight, high watersolubility, and high standard viscosity in solution are used in many fields of industry, for example as thickeners, flocculants, strengtheners for paper, for enhanced oil recovery, for tailings treatment, wastewater treatment, drinking water treatment, and for mining applications.
  • Such polymers are of critical importance for enhanced oil recovery (EOR).
  • EOR techniques such as polymer flooding wherein large volumes of a polymer solution are injected into a subterranean oil reservoir, can be used to increase the amount of unrefined petroleum (e.g., crude oil) that may be extracted from an oil reservoir (e.g., an oil field).
  • unrefined petroleum e.g., crude oil
  • an oil reservoir e.g., an oil field
  • an oil reservoir e.g., an oil field
  • traditional primary and secondary recovery techniques e.g., by water injection or natural gas injection.
  • polyacrylamide is to flocculate solids in a liquid for the purpose of dewatering and filtering.
  • Many industrial processes use dewatering and filtering steps, in which the water content of a bulk solid or slurry is reduced by filtering or other methods.
  • Dewatering processes are necessary, for example, in the treatment of sludge (for example, in sludge ponds or sludge from municipal wastewater treatment process), slurries and in paper-based pulp as well as in other paper treatment processes.
  • Dewatering methods are also used in mining, for example, in dewatering of mine tailings, and metal ores.
  • the mining, processing, and purification of naturally occurring minerals often involve one or more processing or treatment operations in which fine mesh size particles of the mineral of interest are suspended or dispersed in a continuous medium, e.g., a continuous aqueous medium, and the mineral particles are then separated from the medium.
  • Flocculants that comprise polyacrylamide homopolymers and copolymers having high molecular weight are commonly used as a chemical treatment for dewatering oil sands tailings, sludge, and other wastewater.
  • Polyacrylamide flocculants are widely employed in the purification of drinking water as well as in sewage treatment, storm-water treatment, treatment of industrial wastewater streams, and to facilitate settling in slurries comprising mined mineral and ore.
  • Polyacrylamides and copolymers thereof are also used extensively in pulp and paper applications. Polyacrylamide homopolymers and copolymers are used as retention aids (if molecular mass > 2 million g/mole), dry-strength resins, pitch-control agents, and micro-polymer drainage aids.
  • the present invention generally relates to compositions and methods for preparation of high reaction temperature dry polyacrylamide (DPAM) polymers.
  • the disclosure provides methods for adiabatic redox initiated free-radical polymerization of reaction mixtures comprising at least acrylamide monomers, optional free-radical scavenger stabilizers, azo initiators, and redox initiators under initial pH and redox initiation temperature conditions that allow heat of polymerization to increase reaction temperatures to above 100 °C (Tmax > 100 °C).
  • Tmax 100 °C
  • Gel polymerization under these conditions produces anionic DPAM polymers for use in variety of industrial applications with improved standard viscosity, high water-solubility, and little to no residual insolubles.
  • the present invention provides a method for preparing a high reaction temperature dry polyacrylamide (DPAM) by redox initiated free-radical polymerization, the method comprising: [0013] (a) providing or producing an aqueous solution of ethylen ica lly unsaturated monomers comprising water and (i) acrylamide or (ii) acrylamide and one or more additional monomers capable of copolymerizing with acrylamide;
  • additives including but not limited to, one or more chelators, and optionally, one or more chaotropic agents, one or more chain transfer agents, or any combination thereof;
  • the method further comprises, after step (i) drying and milling said high reaction temperature polyacrylamide gel to form said high reaction temperature DPAM as a homopolymer, copolymer, or terpolymer.
  • (b) occurs under a high pressure which is greater than atmospheric pressure and is maintained optionally by heating by said exothermic heat of polymerization or by pressurizing with an inert gas, including but not limited to, nitrogen, argon, helium, or any combination thereof, and further wherein said high pressure is sufficient to prevent boiling of the aqueous reaction mixture when subjected to temperatures greater than 100 °C.
  • a high pressure which is greater than atmospheric pressure and is maintained optionally by heating by said exothermic heat of polymerization or by pressurizing with an inert gas, including but not limited to, nitrogen, argon, helium, or any combination thereof, and further wherein said high pressure is sufficient to prevent boiling of the aqueous reaction mixture when subjected to temperatures greater than 100 °C.
  • said redox initiation temperature ranges from -10 to 25 °C, -10 to 15 °C, -10 to 10 °C, -10 to 5 °C, or -6 to 3 °C;
  • said final reaction temperature ranges from 100 to 150 °C, 100 to 140 °C, 100 to 130 °C, 100 to 120 °C, 100 to 110 °C, or 100 to 105 °C;
  • said curing time ranges from 10-240 min, 30-180, or 60-120 min.
  • said one or more additional monomers comprises: [0032] (a) one or more ethylenically unsaturated, preferably water-soluble, nonionic monomers, including but not limited to, (meth)acrylamide; N-alkylacrylamides, including but not limited to, N- methylacrylamide, N-ethylacrylamide, N-propylacrylamide, and N-butylacrylamide; N,N- dialkylacrylamides, including, but not limited to, N,N-dimethylacrylamide and N,N-diethylacrylamide; N-alkyl methacrylamides; alkyl acrylates; hydroxyalkyl acrylates and methacrylates, including but not limited to, hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4- hydroxybutyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methyl me
  • (b) one or more ethylenically unsaturated anionic monomers including but not limited to, acrylic acid, methacrylic acid; sulfonic acids, phosphonic acids, maleic acid, itaconic acid, vinyl sulfonic acid, acrylamido tertiary butyl sulfonic acid (ATBS) , acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, vinyl phosphonic acid, and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof; and
  • anionic monomers including but not limited to, acrylic acid, methacrylic acid; sulfonic acids, phosphonic acids, maleic acid, itaconic acid, vinyl sulfonic acid, acrylamido tertiary butyl sulfonic acid (ATBS) ,
  • said aqueous solution of ethylenically unsaturated monomers comprises:
  • said one or more optional stabilizers comprise one or more radical scavengers, including but not limited to, thiourea, N,N'-dimethylthiourea, N,N'-diethylthiourea, N,N'-diphenylthiourea, thiocyanates, tetramethylthiuram disulfide, 2-mercaptobenzothiazole (MBT) and salts thereof, 2- mercaptobenzimidazole and salts thereof, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate 2,2'-dithiobis(benzothiazole ), 4,4'-thiobis( 6-t-butyl-m-cresol), dicyandiamide, cyanamide, paramethoxyphenol, 2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole, 8-hydroxyquinoline, 2,5-di(t-amyl)hydroquinone
  • said one or more additives comprise:(i) said one or more chelators, including but not limited to, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid (EDTA) and salts thereof, 2,2',2",2"'-(l,4,7,10-Tetraazacyclododecane-l,4,7,10-tetrayl)tetraacetic acid (DOTA), phosphoric acid, and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof; (ii) said one or more chaotropic agents, including but not limited to, urea, thiourea, alcohols, glycerol, guanidine, and guanidinium halide salts; (ill) said one or more chain transfer agents, including but not limited to, hypophosphorous acid and salts thereof, sodium hypophosphite, sodium formate, pentamethyldisilane (PMDS), isopropy
  • chelators including
  • said one or more azo initiators are selected from the group consisting of azobisisobutyronitrile (Al BN), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride; 2,2-azobis(2- methylpropionamidine) dihydrochloride; 2,2'-azobis(N-(2-carboxyethyl)-2-methylpropionamidine hydrate; 2,2'-azobis ⁇ 2-[l-(2-hydroxyethyl)-2-imidazolin-2-yl]propene ⁇ dihydrochloride; and 2,2'- azobis(l-imino-l-pyrrolidino-2-ethylpropane) dihydrochloride; and
  • said one or more redox initiators are selected from the group of redox initiator systems consisting of ammonium persulfate and ammonium iron ( 11) sulfate (APS/FAS); tert-butyl hydroperoxide and sodium sulfite (tBHP/SS); Fe(ll)/Fe(lll)-hydrogen peroxide systems, Fe(l I )/Fe( II I)- alkyl hydroperoxides systems, alkyl hydroperoxides-sulfite systems, peroxides-thiosulfate systems, alkyl hydroperoxides-sulfinates systems; alkyl hydroperoxides-hydroxymethanesulfinate systems, and t-butyl hydroperoxide-sodium hydroxymethanesulfinate systems.
  • APS/FAS ammonium persulfate
  • tBHP/SS tert-butyl hydroperoxide and sodium sulfite
  • said one or more optional stabilizers comprise sodium 2-mercaptobenzothiazole (Na-2- MBT);
  • said one or more azo initiators comprise AIBN;
  • said one or more redox initiators comprise ammonium persulfate and ammonium iron(ll) sulfate (APS/FAS) or tert-butyl hydroperoxide and sodium sulfite (tBHP/SS).
  • said one or more additives comprise:
  • said redox initiated reaction mixture comprises:
  • an equilibrium redox initiator product concentration e.g., oxidant x reductant
  • an equilibrium redox initiator product concentration ranging from 50-6000, 100-5000, 200-5000, 500-5000, 1000-5000, or 1000-3000 [(pmol/kg) 2 ].
  • the pH ranges from 7.2-7.8, the equilibrium redox initiator product concentration of tBHP/SS ranges from 750-5000 [(pmol/kg) 2 ], the redox initiation temperature ranges from -4 to 6 °C, -4 to 2 °C, or -4 to -2 °C, and the total monomer concentration ranges from 36-42% by wt; or
  • the pH ranges from 7.2-7.8, the equilibrium redox initiator product concentration of APS/FAS ranges from 50-400 [(pmol/kg) 2 ], and the redox initiation temperature ranges from -4 to 6 °C, -4 to 2 °C, or -4 to -2 °C, and the total monomer concentration ranges from 36-42% by wt.
  • said high reaction temperature DPAM said high reaction temperature DPAM:
  • (a) has a standard viscosity (SV) ranging from 6.0-7.5 mPas, 6.5-7.4 mPas, or 7.0-7.2 mPas, determined using a Brookfield viscometer DV1MLV with a UL adapter and a ULA-DIN-Y spindle at 25 °C ⁇ 0.2 °C and 60 rpm;
  • SV standard viscosity
  • (b) has a high water solubility as determined by residual insoluble gel content ranging from 0- 0.5% by wt, 0-0.2% by wt, 0-0.1% by wt, or 0- ⁇ 0.1% by wt, determined by dissolving 1 g of said high reaction temperature DPAM in 1 L of water at 25 °C and then filtering through a 300 pm aperture;
  • (c) has a higher standard viscosity (SV) and higher water solubility compared to a DPAM polymer prepared using the same monomers and same high temperature (Tmax > 100 °C) method with the exceptions of lower pH; or
  • the present invention provides a method for preparing a high reaction temperature dry polyacrylamide (DPAM) by redox initiated free-radical polymerization, the method comprising:
  • said high reaction temperature DPAM is a homopolymer, copolymer, or terpolymer.
  • said redox initiated reaction mixture comprises:
  • the present invention provides a composition comprising a high reaction temperature dry polyacrylamide (DPAM), obtainable by a method according to any of the foregoing.
  • DPAM high reaction temperature dry polyacrylamide
  • FIG 1 provides an exemplary graph of SV (UL Viscosity) vs. pH of reaction for high reaction temperature DPAMs prepared according to Examples 1-6 and Comparative Examples 1-3.
  • FIG 2 provides an exemplary graph of SV (UL Viscosity) vs. maximun reaction temperature (Tmax) for high reaction temperature DPAMs prepared at varying pH, redox level, and monomer concentration including Examples 1-10 and Comparative Examples 1-6.
  • EOR enhanced oil recovery
  • IOR improved oil recovery
  • tertiary mineral oil production generally refers to techniques for increasing the amount of unrefined petroleum (for example, crude oil) that may be extracted from an oil reservoir , such as an oil field .
  • EOR techniques include, for example, miscible gas injection (e.g., carbon dioxide flooding), chemical injection (sometimes referred to as chemical enhanced oil recovery (“CEO R"), and which includes, for example, polymer flooding, alkaline flooding, surfactant flooding, micellar polymer flooding, conformance control operations, as well as combinations thereof such as alkaline - polymer flooding or alkaline - surfactant - polymer flooding), microbial injection, and thermal recovery (e.g., cyclic steam, steam flooding, or fire flooding).
  • miscible gas injection e.g., carbon dioxide flooding
  • chemical injection sometimes referred to as chemical enhanced oil recovery (“CEO R")
  • CEO R chemical enhanced oil recovery
  • thermal recovery e.g., cyclic steam, steam flooding, or fire flooding
  • the EOR operation may include a polymer (“P”) flooding operation, an alkaline - polymer (“AP”) flooding operation, a surfactant - polymer (“SP”) flooding operation, an alkaline - surfactant - polymer (“ASP”) flooding operation, a conformance control operation, or any combination thereof.
  • P polymer
  • AP alkaline - polymer
  • SP surfactant - polymer
  • ASP alkaline - surfactant - polymer
  • conformance control operation or any combination thereof.
  • polymer flood or “polymer flooding” generally refer to a chemical enhanced EOR technique that typically involves injecting an aqueous fluid that is viscosified with one or more water - soluble polymers through injection boreholes into an oil reservoir to mobilize oil left behind alter primary and / or secondary recovery.
  • the oil may be forced in the direction of the production borehole, and the oil may be produced through the production borehole.
  • polyacrylamide generally refer to polymers and copolymers comprising acrylamide moieties, and the terms encompass any polymers or copolymers, including terpolymers, comprising acrylamide moieties, e.g., one or more acrylamide (co)polymers of acrylamide and additional monomers capable of copolymerizing with acrylamide.
  • PAMs may comprise any of the polymers or copolymers discussed herein.
  • high reaction temperature DPAM refers to DPAMs that have been produced by a method wherein the maximum reaction temperature (Tmax) reached during polymerization is greater than 100 °C.
  • High reaction temperature DPAMs produced by exemplary embodiments of the present methods may be used in friction reduction, papermaking retention, as strengtheners for paper, as thickeners and/or flocculants, water treatment, tailings treatment, wastewater treatment, drinking water treatment, mineral ore mining applications, and oil and gas mining applications, such as any EOR technique, including but not limited to, polymer flooding.
  • the term "monomer” generally refers to nonionic monomers, anionic monomers, cationic monomers, zwitterionic monomers, betaine monomers, and amphoteric ion pair monomers.
  • polymer or “polymeric additives” and similar terms are used in their ordinary sense as understood by one skilled in the art, and thus may be used herein to refer to or describe a large molecule (or group of such molecules) that may comprise recurring units.
  • Polymers may be formed in various ways, including by polymerizing monomers and/or by chemically modifying one or more recurring units of a precursor polymer. Unless otherwise specified, a polymer may comprise a "homopolymer” that may comprise substantially identical recurring units that may be formed by, for example, polymerizing a particular monomer.
  • a polymer may also comprise a "copolymer” that may comprise two or more different recurring units that may be formed by, for example, copolymerizing, two or more different monomers, and/or by chemically modifying one or more recurring units of a precursor polymer.
  • a polymer or copolymer may also comprise a "terpolymer” or a "tetrapolymer” which generally refer to polymers that comprise three, four, or more different recurring monomer units.
  • the term "polymer” as used herein is intended to include both the acid form of the polymer as well as its various salts. Polymers may be amphoteric in nature, that is, containing both anionic and cationic substituents, although not necessarily in the same proportions.
  • nonionic monomer generally refers to a monomer that possesses a neutral charge.
  • exemplary nonionic monomers may comprise but are not limited to comprising monomers selected from the group consisting of acrylamide ("AMD"), methacrylamido, vinyl, allyl, ethyl, and the like, all of which may be substituted with a side chain selected from, for example, an alkyl, arylalkyl, dialkyl, ethoxyl, and/or hydrophobic group.
  • a nonionic monomer may comprise AMD.
  • vinyl amide e.g., acrylamide, methacryl
  • Nonionic monomers include N-isopropylacrylamide, N-vinyl formamide, methacrylamide; N-alkylacrylamides, including but not limited to, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, and N- butylacrylamide; N,N-dialkylacrylamides, including, but not limited to, N,N-dimethylacrylamide and N,N-diethylacrylamide; N-alkyl methacrylamides; alkyl acrylates; hydroxyalkyl acrylates and methacrylates, including but not limited to, hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 3- hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl
  • anionic monomers may refer to either anionic monomers that are substantially anionic in whole or (in equilibrium) in part, at a pH in the range of about 1.0 to about 10.0.
  • the "anionic monomers” may be neutral at low pH (e.g., from a pH of about 0-1, 0-2, or 0-3) depending on the pKa values of acidic protons contained therein.
  • Some anionic monomers are obtained in anionic form as alkali metal salts, alkaline earth metal salts, and ammonium salts, e.g., acrylic acid and sodium acrylamido tertiary butyl sulfonic acid (ATBS).
  • anionic monomers which may be used herein include but are not limited to those comprising acrylic, methacrylic, maleic monomers and the like, acrylic acid, calcium diacrylate, and/or any monomer substituted with a carboxylic acid group or salt thereof.
  • anionic monomers may be substituted with a carboxylic acid group and include, for example, acrylic acid, and methacrylic acid.
  • an anionic monomer which may be used herein may be a (meth)acrylamide monomer wherein the amide group has been hydrolyzed to a carboxyl group. Said monomer may be a derivative or salt of a monomer according to other embodiments.
  • anionic monomers comprise but are not limited to those comprising sulfonic acids or a sulfonic acid group, or both.
  • the anionic monomers which may be used herein may comprise a sulfonic function that may comprise, for example, 2-acrylamido-2- methylpropane sulfonic acid (acrylamido tertiary butyl sulfonic acid or "ATBS").
  • anionic monomers may comprise organic acids.
  • anionic monomers may comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamido methylpropane sulfonic acid, vinylphosphonic acid, styrene sulfonic acid and their salts such as sodium, ammonium and potassium.
  • anionic monomers may comprise acrylic acid, methacrylic acid; sulfonic acids, phosphonic acids, maleic acid, itaconic acid, vinyl sulfonic acid, acrylamido tertiary butyl sulfonic acid (ATBS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, vinyl phosphonic acid, and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof.
  • ATBS acrylamido tertiary butyl sulfonic acid
  • Anionic monomers can be combined for example to form a terpolymer of acrylamide , acrylic acid and acrylamido tertiary butyl sulfonic acid (ATBS).
  • one or more acrylamide (co)polymers may comprise at least one monoethylenically unsaturated monomer comprising acid groups, for example monomers that comprise at least one group selected from - COOH, SO3H, or -PO3H2.
  • Examples of such monomers may include , but are not limited to, acrylic acid, methacrylic acid, vinyl sulfonic acid, allyl sulfonic acid or 2-acrylamido -2-methylpropane sulfonic acid, particularly preferably acrylic acid and/or 2-acrylamido-2-methylpropane sulfonic acid, and most preferred acrylic acid or the salts thereof.
  • one or more acrylamide (co)polymers, or each of the one or more acrylamide (co)polymers may comprise acrylic acid and/or 2-acrylamido-2-methylpropanesulfonic acid or salts thereof.
  • water-soluble polymer generally refers to any polymer that may dissolve and/or disperse in water.
  • Said polymers may modify the physical properties of aqueous systems undergoing gelation, thickening, viscosification, or emulsification/stabilization.
  • Said polymers may perform a variety of functions, including but not limited to use as dispersing and suspending agents, stabilizers, thickeners, viscosifiers, gellants, flocculants and coagulants, film-formers, humectants, binders, and lubricants.
  • aqueous solution generally refers to a mixture of water and a water-soluble solute or solutes which are completely dissolved with little to no residual undissolved polymer gel.
  • the solution may be homogenous.
  • the polymer product is preferably fully dissolved and the obtained polymer solution is preferably free from discrete polymer particles or granules or residual gel.
  • gel polymerization refers to a polymerization reaction that is performed without stirring and results in a solid polymer gel.
  • the preparation of high molecular weight polyacrylamides can particularly advantageously be undertaken by means of adiabatic gel polymerization.
  • a solution of acrylamide and optionally water-soluble copolymers is first made up in water.
  • the concentration of the monomers maybe 20 to 70% or 30 to 60% by weight.
  • the solution is polymerized without stirring and the reactor is typically neither heated nor cooled. This gives rise to a solid polymer gel, which is dried and ground to give granules or powder.
  • redox initiated free-radical polymerization refers to a free-radical polymerization that is initiated by free radicals formed by single electron transfer redox reactions between an oxidizing agent and a reducing agent.
  • Free-radical polymerization is a polymerizing approach by which successive addition of free radicals takes place to form a polymer unit. It is a type of chaingrowth polymerization by which a polymer forms by the successive addition of free-radical building blocks (repeat units). Free radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules. Following its generation, the initiating free radical adds (nonradical) monomer units, thereby growing the polymer chain.
  • Chain lengthening ends via a termination step, in which two radicals react to form a stable covalent bond.
  • Virtually all free-radical chain reactions require a separate initiation step in which a radical species is generated in the reaction mixture. The mechanism involves, in order, initiation, chain propagation, and then chain termination. Initiation may be achieved by adding a stable free radical, one that shows little or no tendency for self-combination, directly to the reactants, but a separate initiation step is still involved because these stable radicals are typically inorganic ions or metals.
  • a very effective method of generating free radicals under mild conditions is by one-electron transfer reactions, the most effective of which is redox initiation.
  • This method has found wide application for initiating polymerization reactions and has industrial importance, e.g., in low-temperature emulsion polymerizations. Besides the very short induction period (almost negligible), a lower energy of activation (40-80 kJ/mol) allows the redox polymerization to be carried out under milder conditions than thermal polymerization. This lowers the possibility of side chain reactions giving high molecular weight polymers with a high yield.
  • redox initiator or "redox initiator system” refers to chemicals (e.g., oxidant and reductant) which react by means of a redox reaction to form a radical, which can then initiate a free- radical polymerization reaction.
  • chemicals e.g., oxidant and reductant
  • redox initiators provide a reliable source of free radicals under mild conditions (e.g., temperatures below 25 °C, below zero °C, or below -2 °C).
  • Redox initiators for free-radical polymerization are known in principle to those skilled in the art.
  • redox initiator systems include ammonium persulfate and ammonium iron ( 11 ) sulfate (APS/FAS); tert-butyl hydroperoxide and sodium sulfite (tBHP/SS); Fe(ll)/Fe(lll)-hydrogen peroxide systems, Fe(l I )/Fe( II I)- alkyl hydroperoxides systems, alkyl hydroperoxides-sulfite systems, peroxides-thiosulfate systems, alkyl hydroperoxides-sulfinates systems; alkyl hydroperoxides-hydroxymethanesulfinate systems, and t-butyl hydroperoxide-sodium hydroxymethanesulfinate systems.
  • Oxidant and reductant may be added separately or together (i.e., premixed) as individual compounds or as solutions.
  • Redox initiator systems may be added shortly before, simultaneous with, or after addition of monomers, azo initiators, additives, and optional stabilizers. Redox initiator systems are not regenerable, and may consumed; therefore, time between redox initiator addition and monomer addition must be minimized.
  • redox initiators are added simultaneous with or after monomers are added to the reactor.
  • redox initiators are not added until immediately before the polymerization. Preference is given to using a solution, for example an aqueous solution, of the redox initiators. They can be metered in, for example, during or after the charging of the polymerization reactor.
  • the redox initiators can be metered into the monomer feed of the polymerization reactor during the charging of the reactor.
  • the monomer feed can advantageously be equipped with a static mixer. Under adiabatic conditions, heat generated by the redox initiated polymerization causes the reaction temperature to increase, thereby providing enough heat to cause homolytic bond dissociation in azo initiators, which may be present in solution.
  • redox initiation temperature is the reaction temperature at which the redox initiator is added. Suitable redox initiation temperatures range from-10 to 25 °C, -10 to 15 °C, -10 to 10 °C, -10 to 5 °C, or -6 to 3 °C.
  • the term "equilibrium redox initiator product" "oxidant x reductant” may be calculated using the initial concentrations of redox initiators present (e.g., ammonium persulfate and ammonium iron(ll) sulfate (APS/FAS); tert-butyl hydroperoxide and sodium sulfite (tBHP/SS)) in the kinetic rate expression for each redox reaction.
  • the equilibrium redox initiator product has units of [(pmol/kg) 2 ].
  • stabilizers of this kind include sulfur compounds, for example 2-mercaptobenzothiazole, or sterically hindered amines.
  • WO 2010/133258 Al and literature cited therein give an overview of the use of various stabilizers in polymer solutions for prevention of free-radical degradation by molecular oxygen for tertiary mineral oil production. The reactivity thereof with respect to the free radicals which occur in the free-radical polymerization must not be so great that they significantly influence the polymerization. Suitable stabilizers therefore have only low reactivity under the conditions of the polymerization or are inert with respect to the free radicals which occur in the course of polymerization.
  • stabilizers comprise one or more radical scavengers, including but not limited to, thiourea, N,N'-dimethylthiourea, N,N'-diethylthiourea, N,N'-diphenylthiourea, thiocyanates, tetramethylthiuram disulfide, 2-mercaptobenzothiazole (MBT) and salts thereof, e.g., sodium MBT (Na 2-MBT), 2-mercaptobenzimidazole and salts thereof, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate 2,2'-dithiobis(benzothiazole ), 4,4'- thiobis( 6-t-butyl-m-cresol), dicyandiamide, cyanamide, paramethoxyphenol, 2,6-d i-t-butyl-4- methylphenol, butylhydroxyanisole, 8-hydroxyquinoline, 2,5-di(t-a)
  • Stabilizers can be optionally added at any point in the polymerization process, e.g., before, during, or after polymerization.
  • stabilizers may be optionally added directly to the aqueous monomer solution at any time prior to during or after monomer addition.
  • Single or multiple stabilizers may be added.
  • Stabilizers may also be added before or after cooling, before or after pH adjustment, and before or after redox initiation. More than one stabilizer may be added together or successively in a single dose or multiple doses.
  • the stabilizer e.g., MBT or Na 2-MBT
  • the stabilizer is added directly to the aqueous solution of ethylenically unsaturated monomers prior to adjusting pH, prior to cooling, and prior to redox initiation.
  • azo initiators refers to compounds commonly added to polymerization reactions to form free radicals by homolytic bond cleavage (heat or light initiated) to form free radicals that participate in initiation of polymerization.
  • the aqueous solution further comprises at least one azo initiator, which has a 10 h half-life in water of 40° C to 90° C, preferably 50° C. to 75° C.
  • the 10-hour half-life temperature of azo initiators is a parameter known to those skilled in the art which describes the behavior of initiators. The values describe the temperature at which, after 10 h in each case, half of the amount of Initiator originally present has broken down.
  • Corresponding values can be taken, for example, from the data sheets for azo initiators. On the basis of the 10 h t half-life of 40° C. to 75° C., the initiators do not decompose, or at least do not do so at a significant rate, at room temperature. The values are based on a solution in water.
  • initiation temperatures range from -10 °C to room temperature (e.g., about 25 °C).
  • cooler temperatures such as -10 °C to 10 °C, or -6 °C to +3 °C are used for initiation.
  • the heat of polymerization released heats up the mixture.
  • the azo initiator begins to break down to form radicals and likewise initiates the polymerization.
  • Suitable azo initiators include azobisisobutyronitrile (AIBN), 2,2'-azobis[2-(2- imidazolin-2-yl)propane]dihydrochloride; 2,2-azobis(2-methylpropionamidine) dihydrochloride; 2,2'- azobis(/V-(2-carboxyethyl)-2-methylpropionamidine hydrate; 2,2'-azobis ⁇ 2-[l-(2-hydroxyethyl)-2- imidazolin-2-yl] propene ⁇ dihydrochloride; and 2,2'-azobis(l-imino-l-pyrrolidino-2-ethylpropane) dihydrochloride.
  • AIBN azobisisobutyronitrile
  • 2,2'-azobis[2-(2- imidazolin-2-yl)propane]dihydrochloride 2,2-azobis(2-methylpropionamidine) dihydrochloride
  • the azo initiators are preferably fully water-soluble, but it is sufficient that they are soluble in the monomer solution in the desired amount.
  • AIBN azobis(isobutyronitrile)
  • Azo initiators may be added before or after cooling, before or after pH adjustment, and before, simultaneous with, or after redox initiation, preferably simultaneous with or before redox initiation.
  • Single or multiple azo initiators may be added. More than one azo initiator may be added together or successively in a single dose or multiple doses.
  • the azo initiator e.g., AIBN
  • the azo initiator is added directly to the aqueous solution of ethylenically unsaturated monomers prior to adjusting pH, prior to cooling, and prior to redox initiation.
  • Suitable chelators diethylenetriaminepentaacetic acid penentetic acid
  • ethylenediaminetetraacetic acid EDTA
  • salts thereof 2,2' ,2" ,2"'-(l,4,7 ,10- Tetraazacyclododecane-l,4,7,10-tetrayl)tetraacetic acid (DOTA)
  • phosphoric acid and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof, which may be added before or after cooling, before or after pH adjustment, and before, simultaneous with, or after redox initiation, preferably simultaneous with or before redox initiation.
  • Single or multiple chelators may be added.
  • chelators may be added together or successively in a single dose or multiple doses.
  • the chelator e.g., pentetic acid
  • the chelator is added directly to the aqueous solution of ethylenically unsaturated monomers prior to adjusting pH, prior to cooling, and prior to redox initiation.
  • chaotropic agents refers to molecules in water solution that can disrupt the hydrogen bonding network between water molecules (i.e., exerts chaotropic activity). This has an effect on the stability of the native state of other molecules in the solution, mainly macromolecules (e.g., polymers) by weakening the hydrophobic effect and preventing higher order polymer structures from forming and to prevent aggregation.
  • a chaotropic agent is a structure disrupting additive, general examples of which might include, surfactants, low molecular weight polymers, urea, some salts, etc.
  • a chaotropic agent as an additive that induces or increases the "chaos" or entropy in a system.
  • chaotropic agents for preventing aggregation during gel polymerization include urea, thiourea, alcohols, glycerol, guanidine, and guanidinium halide salts, which may be added before or after cooling, before or after pH adjustment, and before, simultaneous with, or after redox initiation, preferably simultaneous with or before redox initiation.
  • Single or multiple chaotropic agents may be added.
  • Multiple chaotropic agents may be added together or successively in a single dose or multiple doses.
  • the chaotropic agent e.g., urea
  • the chaotropic agent is added directly to the aqueous solution of ethylenically unsaturated monomers prior to adjusting pH, prior to cooling, and prior to redox initiation.
  • chain transfer agents refer to molecules that participate in chain termination reactions in polymerization and which affect the final molecular weight of the polymer and may also result in branching.
  • chain transfer agents In the conventional free radical polymerization, the control of the polymer chain length is difficult to attain.
  • the classical method of controlling molecular weight is the addition of chain transfer agents to the polymerization medium to lower the molecular weight of the polymer strands and to prevent aberrantly long polymer chains from forming. Such aberrantly long strands may contribute to improper solubility of the final polymer.
  • the chain transfer agent e.g., sodium hypophosphite
  • the chain transfer agent is added directly to the aqueous solution of ethylenically unsaturated monomers prior to adjusting pH, prior to cooling, and prior to redox initiation.
  • adiabatic conditions or "essentially adiabatic conditions” refer to conditions which allow little to no heat to escape the polymerization reaction.
  • “Adiabatic” is understood by the person skilled in the art to mean that there is no exchange of heat with the environment. This ideal is naturally difficult to achieve in practical chemical engineering.
  • "adiabatic” shall consequently be understood to mean “essentially adiabatic”, meaning that the reactor is not supplied with any heat from the outside during the polymerization, i.e., is not heated, and the reactor is not cooled during the polymerization.
  • An adiabatic reactor is properly insulated to allow minimal heat to flow in or out of the reactor.
  • inertized atmosphere or “inert gas atmosphere” are phrase generally known in the art to mean under an atmosphere comprising sufficiently high concentration of inert gasses (e.g., N 2 , argon, helium, or the like) and sufficiently low in reactive gasses (e.g., less than 300 ppb, 200 ppb, or 100 ppb O 2 ) to allow for a redox initiated polymerization reaction to occur.
  • inert gasses e.g., N 2 , argon, helium, or the like
  • reactive gasses e.g., less than 300 ppb, 200 ppb, or 100 ppb O 2
  • % by wt denotes grams / kilograms of dry mass of additive per dry mass of solids in the formulation, solution, or slurry, multiplied by 100%.
  • the present invention generally relates to compositions and methods for preparation of high reaction temperature dry polyacrylamide (DPAM) polymers.
  • the disclosure provides methods for adiabatic redox initiated free-radical polymerization of reaction mixtures comprising at least acrylamide monomers, optionally free-radical scavenger stabilizers, azo initiators, and redox initiators under pH and initial temperature conditions that allow the heat of polymerization to increase to reaction temperatures to above 100 °C (Tmax > 100 °C). Gel polymerization under these conditions produces DPAMs with improved standard viscosity and water solubility.
  • SV 6-7.5 mPas standard viscosity
  • solubility i.e., less than 0.5% by wt insolubles
  • SV 6-7.5 mPas standard viscosity
  • solubility i.e., less than 0.5% by wt insolubles
  • the inventive process for preparing acrylamide polymer of the present invention comprises polymerizing acrylamide monomer alone or a monomer mixture composed of acrylamide monomer and a monomer capable of copolymerizing with acrylamide monomer in the presence of an azo series initiator in an aqueous medium having a pH of 7 or higher at a reaction temperature range increasing to above 100 °C, and then drying the resulting material.
  • an azo series initiator in an aqueous medium having a pH of 7 or higher at a reaction temperature range increasing to above 100 °C
  • the present invention generally relates to compositions and methods for preparation of high reaction temperature dry polyacrylamide (DPAM) polymers.
  • the disclosure provides methods for adiabatic redox initiated free-radical polymerization of reaction mixtures comprising at least acrylamide monomers, optional free-radical scavenger stabilizers, azo initiators, and redox initiators under initial pH and redox initiation temperature conditions that allow heat of polymerization to increase reaction temperatures to above 100 °C (Tmax > 100 °C). Gel polymerization under these conditions produces DPAMs with improved standard viscosity, improved water solubility, and little to no residual insolubles.
  • the present invention provides a method for preparing a high reaction temperature dry polyacrylamide (DPAM) by redox initiated free-radical polymerization, the method comprising:
  • additives including but not limited to, one or more chelators, and optionally, one or more chaotropic agents, one or more chain transfer agents, or any combination thereof;
  • the total % monomer content (M solids) is greater than 36% by wt
  • the pH ranges from 7.25-7.5
  • the redox initiator system comprises tert-butyl hydroperoxide and sodium sulfite (tBHP/SS) and is added at high enough redox dosage level to initiate polymerization. Further improvements in solubility may be achieved by addition of hypophosphite or urea.
  • the method further comprises, after step (i) drying, and milling said high reaction temperature polyacrylamide gel to form said high reaction temperature DPAM as a homopolymer, copolymer, or terpolymer.
  • Adiabatic redox initiated free-radical gel polymerizations may be performed without agitation in any suitable adiabatic polymerization reactor system capable of being pressurized to prevent boiling of the reaction mixtures wherein temperature exceeded 100 °C.
  • (a) occurs under an atmosphere comprising nitrogen, argon, helium, or a combination thereof;
  • (b) occurs under a high pressure which is greater than atmospheric pressure and is maintained optionally by heating by said exothermic heat of polymerization or by pressurizing with an inert gas, including but not limited to, nitrogen, argon, helium, or any combination thereof, and further wherein said high pressure is sufficient to prevent boiling of the aqueous reaction mixture when subjected to temperatures greater than 100 °C.
  • a high pressure which is greater than atmospheric pressure and is maintained optionally by heating by said exothermic heat of polymerization or by pressurizing with an inert gas, including but not limited to, nitrogen, argon, helium, or any combination thereof, and further wherein said high pressure is sufficient to prevent boiling of the aqueous reaction mixture when subjected to temperatures greater than 100 °C.
  • reaction mixtures Prior to addition of redox initiator system, the reaction mixtures may be cooled to a redox initiation temperature that is suitable to prevent thermal initiation by the azo initiator.
  • the method comprises one or more of the following:
  • said redox initiation temperature ranges from -10 to 25 °C, -10 to 15 °C, -10 to 10 °C, -10 to 5 °C, or -6 to 3 °C;
  • said final reaction temperature ranges from 100 to 150 °C, 100 to 140 °C, 100 to 130 °C, 100 to 120 °C, 100 to 110 °C, or 100 to 105 °C;
  • said curing time ranges from 10-240 min, 30-180 min, or 60-120 min.
  • said one or more additional monomers comprise:
  • (b) one or more ethylen ically unsaturated anionic monomers including but not limited to, acrylic acid, methacrylic acid; sulfonic acids, phosphonic acids, maleic acid, itaconic acid, vinyl sulfonic acid, acrylamido tertiary butyl sulfonic acid (ATBS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, vinyl phosphonic acid, and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof; and
  • ethylen ically unsaturated anionic monomers including but not limited to, acrylic acid, methacrylic acid; sulfonic acids, phosphonic acids, maleic acid, itaconic acid, vinyl sulfonic acid, acrylamido tertiary butyl sul
  • said aqueous solution of ethylenically unsaturated monomers comprises:
  • the method comprises one, two, three or all four of the following:
  • said one or more optional stabilizers comprise one or more radical scavengers, including but not limited to, thiourea, N,N'-dimethylthiourea, N,N'-diethylthiourea, N,N'-diphenylthiourea, thiocyanates, tetramethylthiuram disulfide, 2-mercaptobenzothiazole (MBT) and salts thereof, 2- mercaptobenzimidazole and salts thereof, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate 2,2'-dithiobis(benzothiazole ), 4,4'-thiobis( 6-t-butyl-m-cresol), dicyandiamide, cyanamide, paramethoxyphenol, 2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole, 8-hydroxyquinoline, 2,5-di(t-amyl)hydroquinone
  • said one or more additives comprise:(i) said one or more chelators, including but not limited to, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid (EDTA) and salts thereof, 2,2',2",2"'-(l,4,7,10-Tetraazacyclododecane-l,4,7,10-tetrayl)tetraacetic acid (DOTA), phosphoric acid, and alkali metal salts, alkaline earth metal salts, and ammonium salts thereof; (ii) said one or more chaotropic agents, including but not limited to, urea, thiourea, alcohols, glycerol, guanidine, and guanidinium halide salts; (ill) said one or more chain transfer agents, including but not limited to, hypophosphorous acid and salts thereof, sodium hypophosphite, sodium formate, pentamethyldisilane (PMDS), isopropy
  • chelators including
  • said one or more azo initiators are selected from the group consisting of azobisisobutyronitrile (Al BN), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride; 2,2-azobis(2- methylpropionamidine) dihydrochloride; 2,2'-azobis(N-(2-carboxyethyl)-2-methylpropionamidine hydrate; 2,2'-azobis ⁇ 2-[l-(2-hydroxyethyl)-2-imidazolin-2-yl]propene ⁇ dihydrochloride; and 2,2'- azobis(l-imino-l-pyrrolidino-2-ethylpropane) dihydrochloride; or
  • said one or more redox initiators are selected from the group of redox initiator systems consisting of ammonium persulfate and ammonium iron ( 11) sulfate (APS/FAS); tert-butyl hydroperoxide and sodium sulfite (tBHP/SS); Fe(ll)/Fe(lll)-hydrogen peroxide systems, Fe(l I )/Fe( II I)- alkyl hydroperoxides systems, alkyl hydroperoxides-sulfite systems, peroxides-thiosulfate systems, alkyl hydroperoxides-sulfinates systems; alkyl hydroperoxides-hydroxymethanesulfinate systems, and t-butyl hydroperoxide-sodium hydroxymethanesulfinate systems.
  • APS/FAS ammonium persulfate
  • tBHP/SS tert-butyl hydroperoxide and sodium sulfite
  • said one or more optional stabilizers comprise sodium 2-mercaptobenzothiazole (Na-2- MBT);
  • said one or more azo initiators comprise AIBN;
  • said one or more redox initiators comprise ammonium persulfate and ammonium iron(ll) sulfate (APS/FAS) or tert-butyl hydroperoxide and sodium sulfite (tBHP/SS).
  • said one or more additives comprise:
  • said redox initiated reaction mixture comprises one or more of the following:
  • a stabilizer concentration ranging from 0.01-2%, 0.02-1.5%, or 0.05-1.0% by wt based on total weight of monomers therein; and [0178] (e) an equilibrium redox initiator product concentration (e.g., oxidant x reductant) ranging from 50-6000, 100-5000, 200-5000, 500-5000, 1000-5000, 1000-3000 [(pmol/kg) 2 ].
  • an equilibrium redox initiator product concentration e.g., oxidant x reductant
  • the pH ranges from 7.2-7.8, the equilibrium redox initiator product concentration of tBHP/SS ranges from 750-5000 [(pmol/kg) 2 ], the redox initiation temperature ranges from -4 to 6 °C, -4 to 2 °C, or -4 to -2 °C, and the total monomer concentration ranges from 36-42% by wt; or
  • the pH ranges from 7.2-7.8, the equilibrium redox initiator product concentration of APS/FAS ranges from 50-400 [(pmol/kg) 2 ], and the redox initiation temperature ranges from -4 to 6 °C, -4 to 2 °C, or -4 to -2 °C, and the total monomer concentration ranges from 36-42% by wt.
  • said high reaction temperature DPAM comprises one or more of the following:
  • the present invention provides a method for preparing a high reaction temperature dry polyacrylamide (DPAM) by redox initiated free-radical polymerization, the method comprising:
  • redox initiators selected from the group of redox initiator systems consisting of ammonium persulfate and ammonium iron(ll) sulfate (APS/FAS) system; tert-butyl hydroperoxide and sodium sulfite (tBHP/SS) system, thereby producing a redox initiated reaction mixture;
  • group of redox initiator systems consisting of ammonium persulfate and ammonium iron(ll) sulfate (APS/FAS) system; tert-butyl hydroperoxide and sodium sulfite (tBHP/SS) system, thereby producing a redox initiated reaction mixture;
  • said high reaction temperature DPAM is a homopolymer, copolymer, or terpolymer.
  • said redox initiated reaction mixture comprises one or more of the following:
  • the present invention provides a composition comprising a high reaction temperature dry polyacrylamide (DPAM), obtainable or obtained by a method according to any of the foregoing.
  • DPAM high reaction temperature dry polyacrylamide
  • Adiabatic redox initiated free-radical gel polymerizations were performed in a cryogenic flask that was placed in a pressurizable chamber to prevent boiling of the reaction mixtures wherein temperature exceeded 100 °C.
  • the pressure chamber was modified in-house from a pressure pot for spray painting (Paint Pressure Tank 10 Liter No Agitator, manufacturer Protima and distributed by Pressurepots.co.uk). Modifications were done for additional safety features and obtaining temperature measurement inside the pot.
  • Polymerization reagents e.g., monomers, azo initiators, additives, including but not limited to, chelating agents, stabilizers, and/or chain transfer agents
  • the pH was adjusted and the mixtures were cooled and purged with N 2 gas.
  • Redox initiators were added and the polymerizations were visually inspected to verify initiation of the polymerization by observation of gel strings and/or temperature increase.
  • the pressure chamber was then closed and pressurized with N 2 gas to prevent boiling as reaction temperatures increased above 100 °C. Heat generated by the polymerization reaction caused the reaction temperature to increase to a maximum temperature (Tmax) above 100 °C. After reaching Tmax, the reactions continued at Tmax for a desired maturation time (i.e., reaction time), and then the chamber pressure was reduced to atmospheric pressure. Resulting polymer gels were cooled, comminuted, dried, and milled according to standard processing and drying procedures. The resulting polymers were evaluated for gel content and standard viscosity (SV).
  • SV standard viscosity
  • the standard viscosity was determined in each case.
  • the resulting polymer was dispersed in deionized water and stirred until the polymer was dissolved. Then NaCI solution was added so that the polymer concentration was 0.1 % and the NaCI concentration was 1.0 M.
  • the UL viscosity (standard viscosity, SV) was determined at 25 ⁇ 0.2 °C using a Brookfield viscometer DV1MLV with a UL adapter and a ULA-DIN-Y spindle at 60 rpm.
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical gel polymerization was performed according to the General Methods. To a glass beaker with magnetic stirrer was added 82.1 g of distilled water and then successively, 267.4 g of acrylamide (49.9% aqueous solution), 170.0 g of a 35% aqueous solution of sodium acrylate (SODAC), 15.9 mg of chelating agent diethylenetriaminepentaacetic acid, pentasodium salt (pentetic acid sodium salt, as 40% aqueous solution), 0.38 g of free-radical oxygen scavenging stabilizer sodium 2-mercaptobenzothiazole (Na-2-MBT, as 50% aqueous solution) and 185.0 mg of azo initiator 2,2'-azobis(2-methylpropionitrile) (AIBN) dispersed in small amount of monomer solution. AIBN has a ti/ 2 of 10 h in toluene at 67 °C.
  • the monomer solution was adjusted to pH 7.25 with a 50% sulfuric acid solution and then cooled to a temperature of -5 °C.
  • the cryogenic flask was placed in a pressure chamber. After visualization of proper initiation of the polymerization (gel strings / temperature increase), the N 2 purging was removed. The chamber was closed and then pressurized with N 2 gas. The temperature rose from -
  • the resulting solid polymer gel block was comminuted using a meat grinder (LM-10/P, Koneteollisuus Oy, Finland) and the gel granules obtained were dried in a fluidized bed dryer at 95 °C (FBD95) for 30 min. A white, hard granular material was obtained, which was converted to a coarse powder with particle size ⁇ 1000 pm by means of a centrifugal mill.
  • Example 2 Second preparation of a high reaction temperature DPAM copolymer
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using less redox initiator.
  • Redox initiation (tBHP/SS) was achieved by addition of 2.4 mL of 0.051% aqueous solution of t-butyl hydroperoxide (tBHP) and 3.2 mL of a 0.057% aqueous sodium sulfite (SS) solution.
  • Table 1 Polymerization conditions and results for high reaction temperature DPAMs.
  • Example 3 Third preparation of a high reaction temperature DPAM copolymer
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a different redox initiator.
  • Redox initiation (APS/FAS) was achieved by addition of 2.4 mL of 0.074% aqueous solution of ammonium persulfate (APS) and 2.4 mL of a 0.127% aqueous ammonium iron(ll) sulfate hexahydrate (FAS) solution.
  • Example 4 Fourth preparation of a high reaction temperature DPAM copolymer
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a higher pH and less redox initiator.
  • Redox initiation (tBHP/SS) was achieved by addition of 2.4 mL of 0.051% aqueous solution of t-butyl hydroperoxide (tBHP) and 2.4 mL of a 0.127% aqueous sodium sulfite (SS) solution.
  • Example 5 Fifth preparation of a high reaction temperature DPAM copolymer
  • Initiation temperature -3 °C.
  • Monomer ratio 69% by weight of acrylamide and 31% by weight of sodium acrylate.
  • Example 6 Sixth preparation of a high reaction temperature DPAM copolymer
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a higher pH and more redox initiator.
  • Redox initiation (tBHP/SS) was achieved by addition of 4 mL of 0.051% aqueous solution of t-butyl hydroperoxide (tBHP) and 4 mL of a 0.178% aqueous sodium sulfite (SS) solution.
  • Example 7 Seventh preparation of a high reaction temperature DPAM copolymer
  • Initiation temperature +3 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a higher pH, a higher initiation temperature, higher monomer concentration, and more redox initiator.
  • AIBN azo initiator 2,2'-azobis(2-methylpropionitrile)
  • the monomer solution was adjusted to pH 7. 5 with a 50% sulfuric acid solution and then cooled to a temperature of +1 °C.
  • the cryogenic flask was placed in a pressure chamber. After visualization of proper initiation of the polymerization (gel strings / temperature increase), the N 2 purging was removed. The chamber was closed and then pressurized with N 2 gas. The temperature rose from +3 °C to a Tmax of 127 °C within 20 min. After Tmax was observed, the gel was matured at Tmax for another 2 h and then the N 2 pressurization was removed.
  • the resulting solid polymer gel block was comminuted using a meat grinder (LM-10/P, Koneteollisuus Oy, Finland) and the gel granules obtained were dried in a fluidized bed dryer at 95 °C (FBD95) for 30 min. A white, hard granular material was obtained, which was converted to a coarse powder with particle size ⁇ 1000 pm by means of a centrifugal mill.
  • Example 8 Eighth preparation of a high reaction temperature DPAM copolymer
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 with the addition of a chain transfer agent.
  • the monomer solution was adjusted to pH 7.25 with a 50% sulfuric acid solution and then cooled to a temperature of -5 °C.
  • the cryogenic flask was placed in a pressure chamber. After visualization of proper initiation of the polymerization (gel strings / temperature increase), the N 2 purging was removed. The chamber was closed and then pressurized with N 2 gas. The temperature rose from - 3 °C to a Tmax of 107 °C within 50 min. After Tmax was observed, the gel was matured at Tmax for another 2 h and then the N 2 pressurization was removed.
  • the resulting solid polymer gel block was comminuted using a meat grinder (LM-10/P, Koneteollisuus Oy, Finland) and the gel granules obtained were dried in a fluidized bed dryer at 95 °C (FBD95) for 30 min. A white, hard granular material was obtained, which was converted to a coarse powder with particle size ⁇ 1000 pm by means of a centrifugal mill.
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical gel polymerization was performed according to the General Methods. To a glass beaker with magnetic stirrer was added 62.9 g of distilled water and then successively, 240.1 g of acrylamide (49.9% aqueous solution), 216.4 g of a 35% aqueous solution of sodium acrylate (SODAC), 15.9 mg of chelating agent diethylenetriaminepentaacetic acid, pentasodium salt (pentetic acid sodium salt, as 40% aqueous solution), 0.39 g of free-radical oxygen scavenging stabilizer sodium 2-mercaptobenzothiazole (Na-2-MBT, as 50% aqueous solution) and 185.0 mg of azo initiator 2,2'-azobis(2-methylpropionitrile) (AIBN) dispersed in small amount of monomer solution. AIBN has a ti/ 2 of 10 h in toluene at 67 °C.
  • the monomer solution was adjusted to pH 7. 5 with a 50% sulfuric acid solution and then cooled to a temperature of -5 °C.
  • the cryogenic flask was placed in a pressure chamber. After visualization of proper initiation of the polymerization (gel strings / temperature increase), the N 2 purging was removed. The chamber was closed and then pressurized with N 2 gas. The temperature rose from - 3 °C to a Tmax of 110 °C within 60 min. After Tmax was observed, the gel was matured at Tmax for another 2 h and then the N 2 pressurization was removed.
  • the resulting solid polymer gel block was comminuted using a meat grinder (LM-10/P, Koneteollisuus Oy, Finland) and the gel granules obtained were dried in a fluidized bed dryer at 95 °C (FBD95) for 30 min. A white, hard granular material was obtained, which was converted to a coarse powder with particle size ⁇ 1000 pm by means of a centrifugal mill.
  • Example 10 Tenth preparation of a high reaction temperature DPAM copolymer
  • Initiation temperature -3 °C.
  • Comparative Example 1 Preparation of a first comparative copolymer
  • Initiation temperature -1 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a lower pH and less redox initiator.
  • Redox initiation (tBHP/SS) was achieved by addition of 4 mL of 0.018% aqueous solution of t-butyl hydroperoxide (tBHP) and 4 mL of a 0.026% aqueous sodium sulfite (SS) solution.
  • Comparative Example 2 Preparation of a second comparative copolymer
  • Initiation temperature -2 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a lower pH and less redox initiator.
  • Redox initiation (tBHP/SS) was achieved by addition of 4 mL of 0.024% aqueous solution of t-butyl hydroperoxide (tBHP) and 4 mL of a 0.034% aqueous sodium sulfite (SS) solution.
  • Comparative Example 3 Preparation of a third comparative copolymer
  • Initiation temperature -2 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a lower pH and less redox initiator.
  • Redox initiation (tBHP/SS) was achieved by addition of 2.8 mL of 0.043% aqueous solution of t-butyl hydroperoxide (tBHP) and 4 mL of a 0.076% aqueous sodium sulfite (SS) solution.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 1 using a lower pH, a higher initiation temperature, higher monomer concentration, and less redox initiator.
  • AIBN azo initiator 2,2'-azobis(2-methylpropionitrile)
  • the monomer solution was adjusted to pH 6.85 with a 50% sulfuric acid solution and then cooled to a temperature of +4 °C.
  • the cryogenic flask was placed in a pressure chamber. After visualization of proper initiation of the polymerization (gel strings / temperature increase), the N 2 purging was removed. The chamber was closed and then pressurized with N 2 gas. The temperature rose from +5 °C to a Tmax of 133 °C within 15 min. After Tmax was observed, the gel was matured at Tmax for another 2 h and then the N 2 pressurization was removed.
  • the resulting solid polymer gel block was comminuted using a meat grinder (LM-10/P, Koneteollisuus Oy, Finland) and the gel granules obtained were dried in a fluidized bed dryer at 95 °C (FBD95) for 30 min. A white, hard granular material was obtained, which was converted to a coarse powder with particle size ⁇ 1000 pm by means of a centrifugal mill.
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 8 without Na-2-MBT.
  • Initiation temperature -3 °C.
  • Adiabatic redox initiated free-radical polymerization was performed according to Example 4 using a higher pH. Polymerization did not initiate and gel strings / temperature increase were not observed.
  • FIG. 1 An exemplary graph of SV (UL Viscosity) vs. pH of reaction for high reaction temperature DPAMs prepared according to Examples 1-6 and Comparative Examples 1-3 is provided in FIG 1.
  • the present method for preparing a high reaction temperature dry polyacrylamide (DPAM) by redox initiated free-radical polymerization also provide a means for improving manufacturing capacity.
  • An exemplary graph of SV (UL Viscosity) vs. maximun reaction temperature (Tmax) for high reaction temperature DPAMs prepared at varying pH, redox level, and monomer concentration including Examples 1-10 and Comparative Examples 1-6 is provided in FIG 2. Data points only with good solubility are shown, i.e., insoluble content ⁇ 0.5 wt%. The lines are added to denote the maximum viscosity achieved. Dashed line denotes the maximum viscosity obtained for process products pH ⁇ 7.
  • Dotted line denotes the maximum viscosity obtained for process products pH > 7.
  • This repulsion serves to minimize unwanted side reactions, thereby minimizing unwanted side reactions between vicinal strands, which causes decreasing molecular weight, branching and in worst case insolubility.
  • the present method likely controls the MW distribution and polymer structure. Thus, insoluble gel content is minimized, even at high temperatures.

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  • Organic Chemistry (AREA)
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Abstract

La présente invention concerne de manière générale des compositions et des procédés de préparation de polymères de polyacrylamide sec (DPAM) à température de réaction élevée. En particulier, la divulgation concerne des procédés de polymérisation de radicaux libres initiée par redox adiabatique de mélanges réactionnels comprenant au moins des monomères d'acrylamide, des stabilisants de fixateurs de radicaux libres facultatifs, des initiateurs azo et des initiateurs redox dans des conditions de pH et de température initiale qui permettent à la chaleur de polymérisation d'augmenter les températures de réaction à plus de 100 °C (Tmax > 100 °C). La polymérisation en gel dans ces conditions produit des polymères DPAM anioniques destinés à être utilisés dans diverses applications industrielles avec une viscosité standard améliorée et une solubilité aqueuse élevée.
PCT/US2024/036757 2023-07-05 2024-07-03 Préparation d'un dpam à température de réaction élevée présentant une viscosité standard et une solubilité aqueuse améliorées Pending WO2025010348A2 (fr)

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