HETEROGENEOUS PARTICULATE SOLID CONCENTRATES

FOR YIELD STRESS FLUIDS

CROSS-REFERENCE TO RELATED APPLICATION(S ^' )

[0001 ] This application is being filed on March 6, 2015, as a PCT International Patent application and claims priority to U.S. Patent Application Serial No. 61/949,778 filed on March 7, 2014, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND FIELD

[0002] Yield stress fluid heterogeneous particulate solid concentrates and methods for the preparation of yield stress fluids from, the solid concentrates using recirculating agitation are provided. The yield stress fluids are useful for fire extinguishment and fire protection.

DESCRIPTION OF THE RELATED ART

[0003] Aqueous yield stress fluids have a long standing history of having been proposed as materials used for fire suppression or protection from fire. By yield stress fluid it is meant a substance that has the properties of a solid in the absence of shear stress and the properties of a liquid in the situation of sufficient shear stress. As pertains to compositions used for fire suppression, yield stress fluids may also be referred to as aqueous dispersions, aqueous suspensions, gels, gelled water fire suppressants and enhanced water.

[0004] Well know examples of yield stress fluids include aqueous suspensions of water insoluble highly water swellahle polymers, which may commonly be referred to as superabsorbent polymers (S AP's). When swollen with water and even when swollen and compacted, water insoluble highly water swellahle polymer particulates retain their individual identity with interstitial space existing between adjacent particles. Typically water insoluble highly water swellable particles consist of water soluble polymers that have been derivitized in a way so as to provide maintenance of individual particle identity and so as to minimize interparticle adhesion and coalescence, treatments which are important for sustaining interstitial capillaries that allow for influx and absorption of bodily fluids in applications such as hygiene products including disposable diapers,

[00051 When suspended in water in sufficient amounts, wafer insoluble highly wafer swellable particles give sludgy solid compositions that have the rheological properties of slushes including liquification under shear and therefore are a subset of the group of yiel d stress fluids. Compared to other yield stress fluids, those that comprise water insoluble highly water swellable particles have unique properties that are advantageous. For example the property of maintaining individual particle identity is useful for forming aqueous yield stress fluids from concentrates because the tendency for formation of large, difficult to dissolve agglomerates during mixing with water is minimized,

[0006] Unfortunately, the particulate nature of water insoluble highly water swellable suspensions also gives rise to undesirable properties for fire suppression. Insolubilization that is accomplished by crosslinking polymer particles, especially on the surface, results in a more highly constrained polymer which occupies less volume than a less crosslmked water soluble polymer of similar composition. This means that a. greater concentration of water insoluble highly water swellable polymer is required to give equivalent yield stress and thickening compared to a water soluble polymeric thickener of similar composition.

[0007] Another undesirable property of suspensions of w ^r ater insoluble highly water swellable polymer particles is that disparities in viscosity and yield stress can emerge during flow as a result of congregation or piling up of particles in a logjam effect. As applied to a vertical surface, coatings exhibit regions of high concentrations of particles that strongly resist flow and regions where particles have flowed away from and been strained out by the high concentration regions, resulting in locally reduced coating weights and gaps. Gaps in coatings results in diminishment of the effectiveness of extinguishment and structural protection. During pumping, local disparities in concentration of particles may give rise to regions of high yield stress sufficient to cause blockage and pump cavitation. Because there is a very steep dependence of yield stress on the concentration of water insoluble highly water swellable polymer particulates it is difficult to prepare fluids at the precise solids concentration so as to provide sufficient gel stiffness for fire suppression while at the same time allowing sufficiently low flow viscosity for effective pumping. A further problem with suspensions of water insoluble highly water swellabie particles is that they can settle fairly rapidly, compounding the problems of concentration control and acceptable pumping characteristics.

[00081 Separate from water insoluble, highly water swellabie polymer particles of the type used to make diapers, are water soluble polymeric thickeners that dissolve in water so as to give homogeneous solutions. Such water soluble polymeric thickeners may also be referred to as soluble polymer gellants, dissolvable yield stress polymers, or polymeric high yield suspending agents.

[0009] The use of water soluble polymeric thickeners (high yield suspending agents) has been described by Hagquist et al, US Patent No. 7,476,346, "Composition inhibiting the expansion of fire, suppressing existing fire, and methods of manufacture and use thereof, which is incorporated herein by reference. According to Hagquist et ai., a solid concentrate is provided by admixing solid powders of sodium hydroxide, starch, clay, and polyacrylic acid. However, solid concentrates according to Hagquist et al. are difficult to dissolve. In attempting to prepare an aqueous yield stress fluid by pouring solid concentrate into a reservoir of recirculating water, the solid concentrate according to Hagquist is observed to coalesce into large agglomerates which do not easily disperse or dissolve. [0010] However advantageous the use of water soluble polymeric thickeners may be for fire suppression and protection, they suffer a disadvantage that they are difficult to dissolve. In attempting to form aqueous yield stress fluids from dissolvable yield stress polymers, particles can coalesce into large agglomerates which do not disperse or dissolve even with long periods of agitation. Compounding the problem is the fact that agitation available at the point of use of fire suppressant materials is often poor. At the site of generation, it, is unacceptable to use in situ type reactions such as predispersion of a polymer that is water insoluble that reacts with a solubilizing reagent in a reaction such as neutralization as a means of preparing yield stress fluids. [0011] After many years of trying to do so, there has not yet been developed a practical and commercially viable method of suppressing fire with yield stress fluids derived from solid concentrates comprising water soluble polymeric thickeners, in spite of process improvements such as incorporation of solid concentrates into fluid flowing water using eduction and preparation of solid concentrates comprising hydrophobic agglomerating agents.

[0012] Therefore, for practical use of yield stress fluids in large scale fire suppression, it would be desirable to provide a solid concentrate that can be combined with water at the point of use to rapidly provide a yield stress fluid that is non-settling, comprises a water soluble polymeric thickener, and has a value of yield stress that is sufficient to provide a continuous, non-gapping coating when applied to inverted and vertical surfaces.

SUMMARY OF THE INVENTION

[001 ] Yield stress fluid heterogeneous particulate solid concentrates and methods for the preparation of yield stress fluids from the solid concentrates using recirculating agitation are provided. The yield stress fluids are useful for fire extinguishment and fire protection. [0014] In some embodiments, a method is provided for forming a yield stress fluid composition for fire suppression comprising adding an aqueous fluid to a fluid reservoir; providing agitation in the fluid reservoir by withdrawing and returning the fluid through an external circuit; and introducing a heterogeneous particulate solid concentrate into the fluid in the reservoir while providing agitation to form a yield stress fluid composition for fire suppression, wherein the heterogeneous particulate solid concentrate comprises a water soluble polymeric thickener. In some embodiments, the heterogeneous particulate solid concentrate further comprises a. viscously inert material. In some aspects, the external circuit comprises a vertical return line or a horizontal return line. In some aspects, the vertical return line or horizontal return line extends beneath a surface of the fluid in the reservoir. [0015] In some embodiments, a heterogeneous particulate solid concentrate is provided for preparing a yield stress fluid for fire suppression, wherein the particulate solid concentrate comprises a water soluble polymeric thickener selected from the group consisting of neutralized polyacrylic acid, methylcellulose, sodium carboxy methylcellulose, xanthan gum, guar gum, and carboxyvinyl polymer sodium salt. In specific aspects, the particulate solid concentrate comprises a water soluble polymeric thickener selected from carboxyvinyl polymer sodium salt or neutralized polyacrvlic acid. In some embodiments, the heterogenous particulate solid concentrate comprises between about 5 weight percent and 45 weight percent, between about 10 weight percent and 40 weight percent, or between about 15 weight percent and 37 weight percent water soluble polymeric thickener.

[0016] In some embodiments, the heterogenous particulate solid concentrate comprises a water soluble polymeric thickener that passes two or more, or three or more, of the following tests: (1) exhibits continuity in a coalescence test; (2) exhibits a ratio of nonvolatile content in a lower liquid layer relative to nonvolatile content in an upper liquid layer of <2.0 in a centrifugation test; (3) does not exhibit settling in a settling test; and (4) exhibits filterability in a filterability test.

[0017] In some embodiments, the heterogeneous particulate solid concentrate comprises a water soluble polymeric thickener and a. viscously inert material is selected from one or more of the group consisting of starch, clay and sugar. In some aspects, a particulate solid concentrate composition is provided comprising a water soluble polymeric thickener and from 30-85 wt%, 33-80 wt%, or 55-70 wt% total viscously inert material.

[0018] In some embodiments, the heterogeneous particulate solid concentrate has a D10 particle diameter greater than about 100 microns, greater than about 200 microns, or greater than about 300 microns.

[0019] In some embodiments, a heterogeneous particulate solid concentrate is provided that is a conglomerate particle. In some aspects, a conglomerate particle is provided exhibiting a core-shell structure comprising a relatively higher concentration of water soluble polymeric thickener in the core and a. relatively higher concentration of viscously inert material in the shell.

[0020] In some embodiments, a heterogeneous particulate solid concentrate is provided for forming a yield stress fluid composition for fire suppression, wherein the composition comprises a water soluble polymeric thickener and a viscously inert material, in some aspects, the viscously inert material comprises an intumescent material, such as a starch.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021 ] FIG. I A shows a diagram of a recirculating agitation mixing apparatus featuring a vertical return line 20 for generation of yield stress fluids.

[0022] FIG . I B shows another view of the diagram of a recirculating agitation mixing apparatus according to FIG. 1A, illustrating an off vertical angle Θ of vertical return line 20,

[0023] FIG. 1 C shows a diagram of 5 gallon scale recirculating agitation equipment, featuring a vertical return line 20, used for the recirculating agitation mixing test of yield stress fluid solid concentrates.

[0024] FIG. 1 D shows a diagram of 200 gallon skid unit recirculating agitation equipment used for the Large scale mixing test.

[0025] FIG. 2A shows a scanning electron microscope image of an intact heterogeneous particulate yield stress fluid solid concentrate particle prepared according to Example 2 at X I 00 magnification.

[0026] FIG . 2B shows a scanning electron microscope image of a fractured heterogeneous particulate yield stress fluid, solid concentrate particle prepared according to Example 2 at X400 magnification.

[0027] FIG. 2C shows a scanning electron microscope image of a heterogeneous particulate yield stress fluid solid concentrate particle from FIG. 2B at X250 magnification.

[0028] FIG. 3A. shows Energy Dispersive X-ray Spectroscopy (EDS) of heterogeneous yield stress solid concentrate particle at point 1 in FIGs. 2B, 2C.

[0029] FIG. 3B shows Energy Dispersive X-ray Spectroscopy (EDS) of heterogeneous yield stress solid concentrate particle at point 2 in FIGs. 2B, 2C. [0030] FIG. 3C shows Energy Dispersive X-ray Spectroscopy (EDS) of heterogeneous yield stress solid concentrate particle at point 3 in FIG. 2C.

[0031] FIG. 4 shows a graph of viscosity versus time for mixing comparative example sodium polvacrylate yield stress fluid solid concentrate (Comparative Example A) with water using recirculating agitation.

[0032 ] FIG. 5 shows a graph of viscosity versus time for mixing a comparative example potassium polyacrylate yield stress fluid solid concentrate (Comparative Example B) with water using recirculating agitation.

[0033] FIG. 6 shows a graph of viscosity versus time for large scale mixing of a comparative example potassium polyacrylate yield stress fluid solid concentrate (Comparative Example B) with water using recirculating agitation.

[0034] FIG. 7 shows a graph of viscosity versus time for mixing a comparative example potassium polyacrylate yield stress fluid solid concentrate (Comparative Example C) with water using recirculating agitation. [0035] FIG. 8 sho ws a graph of viscosity versus time for mixing a comparative example sodium polyacrylate yield stress fluid solid concentrate ((Comparative Example D with water using recirculating agitation.

[0036] FIG. 9 shows a graph of viscosity versus time for mixing a comparative example powder blend yield stress fluid solid concentrate (Comparative Example E) with water using recirculating agitation.

[0037] FIG. 1 0 sho ws a graph of viscosity versus time for mixing a comparative example powder blend yield stress fluid solid concentrate with hydrophobic agglomerating agent ((Comparative Example F) with water using recirculating agitation.

[0038] FIG. 1 5 shows a graph of viscosity versus time for mixing a comparative example yield stress fluid solid concentrate (Comparative Example G) with water using recirculating agitation. [0039] FIG. 12 shows a graph of viscosity versus time for mixing a comparative example yield stress fluid solid concentrate (Comparative Example H) with water using recirculating agitation.

[0040] FIG. 13 shows a graph of viscosity versus time for mixing a comparative example yield stress fluid solid concentrate (Comparative Example I) with water using recirculating agitation.

[0041] FIG. 14 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 1) with water using recirculating agitation. [0042 ] FIG. 15 shows a graph of viscosity versus time for Large scale mixing of a heterogeneous particulate yield stress fluid solid concentrate (Example 1) with water using recirculating agitation.

[0043] FIG. 16 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 2) with water using recirculating agitation.

[0044] FIG. 17 shows a graph of viscosity versus time for mixing of a heterogeneous particulate yield stress fluid solid concentrate (Example 3) with water using recirculating agitation.

[0045] FIG. 1 8 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 4) with water using recirculating agitation.

[0046] FIG . 19 shows a graph of viscosity versus time for Large scale mixing of a heterogeneous particulate yield stress fluid solid concentrate (Example 4) with water using recirculating agitation. [0047] FIG. 20 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 5) with water using recirculating agitation. [0048] FIG. 21 shows a graph of viscosity versus time for l arge scale mixing of a heterogeneous particulate yield stress fluid solid concentrate (Example 6) with water using recirculating agitation.

[0049] FIG. 22 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 7) with water using recirculating agitation.

[0050] FIG. 23 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 8) with water using recirculating agitation. [0051 ] FIG. 24 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 9) with water using recirculating agitation.

[0052] FIG. 25 shows a graph of viscosity versus time for mixing a heterogeneous particulate yield stress fluid solid concentrate (Example 10) with water using recirculating agitation.

DETAILED DESCRIPTION OF THE INVENTION

[0053] All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure. Wt% is based on the total weight of the particulate composition or yield stress fluid.

[0054] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. [0055] As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise. [0056] As used herein, "have", "having", "include", "including", "comprise",

"comprising" or the like are used in their open ended sense, and generally mean "including, but not limited to." It will be understood that the terms "consisting of and "consisting essentially of are subsumed in the term "comprising," and the like.

[0057] Heterogeneous particulate solid concentrate compositions are provided for preparing yield stress fluids for fire suppression that can be effectively mixed with water using recirculating agitation. The compositions and methods provided herein overcome the prior art disadvantages of powder solid concentrates being difficult to dissolve, and coalescing into large agglomerates which do not disperse or dissolve even with long periods of agitation. [0058] The yield stress fluid formed by methods provided herein comprising mixing a particulate solid concentrate with water can be pumped or sprayed by typical high pressure pumping equipment or by low-pressure individual tanks. The yield stress fluid can have a "high yield value" (the force that must be applied to a fluid layer before any movement is produced), meaning it has an initial resistance to flow under stress but then is shear thinning, and when used, exhibits "cling," meaning it has the ability at rest, to return to a pseudo-plastic or thixotropic gel. The yield stress fluid composition does not readily separate or settle and can be easily sprayed and thickens when it contacts an indoor or outdoor surface. In firefighting application, for example, this gives the firefighter the ability, unlike water alone, to build thickness and hold the dispersion or aqueous gel on vertical or overhead surfaces. [0059] The heterogeneous particulate solid concentrate compositions comprise a water soluble polymeric thickener. Preferred solid concentrate particles are heterogeneous and comprise a water soluble polymeric thickener and a second material that contributes negligible viscosity to the yield stress fluid aqueous composition. Materials that contribute negligible viscosity to aqueous compositions are referred to as viscously inert materials. [0060] The term "water soluble polymeric thickener" is used herein to describe a high molecular weight, water soluble polymer. Preferred water soluble polymeric thickeners are lightly crosslinked high molecular weight, water soluble polymers, however the extent and nature of the crosslinks are such that the polymer remains soluble in water at room

temperature at concentrations up to about 1 percent by weight and preferably 2 percent by weight. The property of being water soluble can be determined by tests provided herein including filtering tests, centrifugation tests, and settling tests. Useful water soluble polymeric thickeners may include mixtures or two or more discrete compounds.

[0061] Water soluble polymeric thickeners are polymers that typically are film forming and capable of coalescence at room temperature. When homogeneous particles of water- soluble polymeric thickeners are wetted with water, they become very strongly mutually adhesive by nature of their capability for coalescence. Unlike fairly weak associations between water insoluble, highly water swellable polymer particles (e.g., SAPs), bonds between water wetted water soluble polymeric thickener particles are not easily disrupted even by intense agitation.

[0062] Water soluble polymeric thickener solutions can be distinguished from

suspensions of water insoluble, highly water swellable particulate suspensions in a number of ways including: (1) being transparent and not hazy, (2) being non-settling, (3) being capable to be filtered, and (4) not separating upon centrifugation. [0063] Solutions of water soluble polymeric thickeners can be distinguished from solutions of water insoluble, highly water swellable polymers by subjecting the solution to the following specific tests, A solution of a water soluble polymeric thickener (WSPT) will generally conform to two or more, or three or more of the following criteria: (1) exhibit continuity in a coalescence test; (2) exhibit a ratio of nonvolatile content in a lower liquid aliquot relative to nonvolatile content, in an upper liquid aliquot of <2.0 in a centrifugation test; and/or does not exhibit a supernatant layer in a centrifugation test , (3) does not exhibit settling in a settling test; and (4) exhibits filterability in a filterability test.

[0064] In contrast, a solution of a water insoluble, highly water swellable polymer (WTHWS) will generally exhibit (1) discontinuity, or fail, the coalescence test,(2) a ratio of nonvolatile content in a lower liquid aliquot relative to nonvolatile content in an upper liquid aliquot of >2.0 in a centrifugation test; and/or a measurable supernatant layer in a

centrifugation test; (3) settling in a settling test; and (4) fail the filterability test.

[0065] One way to identify a solution of a water soluble polymeric thickener is the absence of settling. For example, when dissolved in water containing 0.10% sodium chloride at 0.10 weight percent polymer, water soluble polymeric thickeners will not exhibit visible settling after standing 24 hours.

[0066] Another way to identify of a solution of a water soluble polymeric thickener is the capability to pass through an 11 micron nominal pore size filter (for example, Whatman Number 1 filter).

[0067] Another way to identify of a solution of a water soluble polymeric thickener is that trae solutions, including solutions of water soluble polymeric thickeners, tend to be clear and not hazy, as opposed to suspensions, including suspensions of water insoluble highly water swellable polymer particles which exhibit some haze. However, although solutions of water soluble polymeric thickeners themselves are non-settling, filterable and not hazy, they may contain impurities, including impurities in the water soluble polymeric thickener, which settle, prevent filtration, or cause haze.

[0068] Another way to identify a solution of a water soluble polymeric thickener is stability towards centrifugation. For example, a characteristic of a. solution of a water soluble polymeric thickener that is unaffected by the presence of adventitious materials which may otherwise interfere with filtration and clarity is stability towards centrifugation. Solutions of water soluble polymeric thickeners, upon centrifugation, do not produce a supernatant layer whether or not they contain components such as suspensions of other materials that interfere with filtration and clarity. Furthermore, whether a supernatant layer is visible or not, compositions comprising water soluble polymeric thickeners have minimal differences in percent non-volatile content between liquid removed from the bottom of a centrifuge tube and liquid removed from the top of a centrifuge tube after centrifugation. For example, the ratio of the percent non-volatile content of liquid removed from, the bottom 10 mL of a centrifuge tube after centrifugation to the percent non-volatile content of liquid removed from the top 10 mL of a 50 rnL conical bottom centrifuge tube is less than about 2 to 1 after centrifugation using an IEC Model 35472H operating at maximum rpm for 30 minutes.

[0069] Examples of various material test results are shown in Table 1. These results show that Carbopol EZ-3 (neutralized polyacrylic acid), Ticacel HV (methyl cellulose), Aqualon CMC Gum 7H4 (sodium carboxy methyl cellulose), VAN GEL Xanthan Gum (xanthan gum), NEUTRAGEL® DA(sodium olyaciylate), Ticagel onnjac High Viscosity Guar Gum (guar gum), and Tic Gums Pre-Hydrated® Guar Gum 8/24 are water soluble polymeric thickeners ( WSPTs). Each of these water soluble polymeric thickeners pass three or more, of the following tests: (1) exhibits continuity in the coalescence test: (2) exhibits a ratio of nonvolatile content in a lower liquid layer relative to nonvolatile content in an upper liquid layer of <2.0 in the centrifugation test: (3) does not exhibit settling in the settling test; and (4) exhibits filterability in the filterabiiity test.

[0070] In contrast, Table 1 shows AQUASORB® (sodium polyacrylate), FIREICE® (potassium polyacrylate), and AQUAGEL® (potassium polyacrylate) are water insoluble, highly water swellabie polymers (WIHWSPs). Each of these water insoluble, highly water sweliable polymers fail three or more of the following tests: (1) exhibits continuity in the coalescence test: (2) exhibits a ratio of nonvolatile content in a lower liquid layer relative to nonvolatile content in an upper liquid layer of <2.0 in the centrifugation test; (3) does not exhibit settling in the settling test; and (4) exhibits filterability in the filterability test. [0071] In general, water soluble polymers become more difficult to dissolve in water as the molecular weight increases. Although the cost effectiveness of water soluble polymeric thickeners increases as the molecular weight increases, so does the difficult of dissolution and the susceptibility of the polymer chains to rupture if excessive shearing occurs during dissolution. Very high molecular weight water soluble polymeric thickeners, when introduced into water and dissolved using high shear, may give viscosity as a function of time that reaches a maximum, value and then declines as polymer chains are ruptured. The maximum, viscosity may be reached before the polymer completely dissolves and further evolution of rheology is determined by competition between dissolution of more polymer and chain rupture of already dissolved polymer, both of which result from generation of shear forces in the solution.

[0072] One potential solution to the difficulty of dissolving water soluble polymeric thickeners is to employ greater concentrations of relatively lower molecular weight, easier to dissolve polymers. In some cases the monomer composition of the polymer is the same as that of higher molecular weight polymers, but polymerization has been carried out to a lesser degree.

[0073] One disadvantage of using lower molecular weight water soluble polymeric thickeners is that they often cost insignificantly less per unit weight but require greater concentrations, in which case the cost of achieving similar levels of thickening is considerably greater. A further disadvantage of using lower molecular weight water soluble polymeric thickeners is that the amount of solid concentrate required for adequate thickening and the capability to formulate are impacted.

[0074] A variation of using water soluble polymeric thickeners of relatively lower molecular weight that avoids the problem of greater cost of achieving similar levels of thickening is to increase the effective molecular weight of the water soluble polymeric thickener once it has been dissolved. An example of this approach is borate thickening of saccharide gums such as guar gum and xanthan gum. A large portion of yield stress fluids used in subterranean operations such as hydraulic fracturing (fracking) are based on borate thickened guar gum. Guar gum can be provided in easier to dissolve forms such as agglomerated and pre-hydrated. An example of an agglomerated, pre-hydrated guar gum. is Pre-Hydrated® Guar Gum 8/24 Powder available from Tic Gums, Belcamp MD.

[0075] In some embodiments, the effective intrinsic yield value of Guar Gum can be increased by reaction with sodium borate which provides hydrogen bonding interaction association of hydroxyl groups on the polymer. For subterranean operations, one important mode of operation is to pump freshly mixed borate plus guar gum composition before the viscosity and yield stress become impractically high. Once pumped, the reaction of borate and polymer hydroxy! groups continues and the viscosity and yield stress increase. As applied to fire suppressants, using borate to thicken hydroxyl functional polymers is undesirable because it requires mixing two materials, the kinetics of viscosity increase can't be sufficiently controlled and because borate thickening gives diiatant (shear thickening) rheology as opposed to shear thinning. For use in wildland firefighting applications, boron containing compositions are also not preferable because of environmental concerns. Preferable yield stress fluids for fire suppression contain less than about 50 ppm, less than about 20 ppm, and less than about 5 ppm of boron by weight. In some embodiments, a method for forming a yield stress fluid composition for firefighting is provided, wherein no isolated sodium borate is added to the yield stress fluid composition, and/or wherein the yield stress fluid

composition does not contain a quantifiable amount of sodium borate. [0076] In some embodiments, water soluble polymeric thickeners are copolymers that comprise di- and poly- functional monomers incorporated into polymer chains consisting mostly of water soluble monofunctional monomers. Preferred water soluble polymeric thickeners comprise mono- and di- or poly- functional monomers in such a way that the chain architecture may be described as branched or lightly crosslinked. For water soluble polymeric thickeners that comprise di- and poly- functional monomers, it is preferred that the branching (i.e. crossiinking) sites occur near the polymer chain initiation point rather than near the polymer chain termination point. Branching that occurs near the beginning of chain growth is an important method for providing high molecular weight distributions of water soluble polymers, especially in water soluble polymeric thickeners prepared by vinyl addition polymerization. By incorporating branches early in the chain, more than one propagating chain per growing polymer molecule is provided. Having more than one propagating chain per growing polymer molecule increases the probability of achieving high molecular weight before the growing polymer chain terminal free radicals are extinguished by reaction with other free radicals or by chain transfer. One way to promote early chain growth incorporation of crosslinks is by selecting monofunctional monomers and di- or poly- functional crossiinking monomers with appropriate reactivity ratios. In particular it is preferred that in the case that monomer 1 is the monofunctional monomer and monomer 2 is the di- or poiyfunctional monomer, that the ΐ reactivity ratio ( defined as the rate of reaction of a polymer chain ending in a radical derived from monomer 1 reacting with monomer 1 divided by the rate of reaction of a polymer chain ending in a radical derived from monomer 1 reacting with monomer 2 ) be less than 1. In this case the growing free radical chain of the more abundant monofunctional monomer 1 preferentially selects for the di- or poly functional monomer 2, leading to a bias in monomer 2 addition and early incorporation of the crosslink site in the propagating chain. When the monofunctional monomer is designated as monomer 1 and the di- or polyfunctional monomer is monomer 2, preferred water soluble polymeric thickeners comprise monofunctional monomers and di- or polyfunctional monomers such that the reactivity ratio rj is less than i , less than 0,5, and less than 0.2.

[0077] Whether polymers comprise vinyl addition di- or poly- functional crosslinking monomers or not, and whether or not branching or crosslinking occurs near the beginning or end of polymer chains, further crosslinking after completion of vinyl addition polymerization may be done to change polymer properties. Typically crosslinking after polymerization is complete is effective to diminish solubility of the polymer. In the case that polymers are further crosslinked subsequent to completion of vinyl addition polymerization, the secondary crosslinking occurs near the end of propagated chains and can be directed to occur on or near the surface of polymer particles. Such crosslinking may be referred to as surface crosslinking. Surface crosslinking of polymer particles that comprise carboxylic acid functional monomers may be accomplished by condensation reactions, i. e. reactions that produce water as a reaction product such as esterification and amidation reactions. Surface crosslink sites of carboxylic acid functional polymers can include carbonyl containing moieties such as esters, sulfoesters, and amides. For use in heterogeneous particulate solid concentrates for yield stress fluids, preferred water soluble polymeric thickeners have not been subjected to secondary crosslinking that to a degree that renders them insoluble and preferably remain water soluble as determined by tests including filterahility, settling, and centrifugation. In some embodiments, preferred water soluble polymeric thickeners that comprise carboxylic acid groups or carboxylate groups are essentially free from bond forming carbonyl moieties including esters, sulfoesters, and amides,

[0Θ78] Exemplar)' water soluble polymeric thickeners include alkalai metal salts of poiyacry!ic acid copolymers including lightly crosslinked copolymers; ammonium salts of polyacrylic acid copolymers including lightly crosslinked copolymers; natural gums such as guar, locust bean, and xanthan gum; cellulose derivatives such as methyl cellulose, hydroxy ethyl cellulose, and carboxy methyl cellulose; polyacrylamide copolymers including lightly crosslinked copolymers; copolymers of 2-Acrylamido-2-methylpropane sulfonic acid (AMPS); copolymers of hydroxy! functional acrylate and methacrylate monomers such as hydroxyethyl niethaerylate and hydroxypropyi methacrylate; homopolymers and copolymers of ethylene oxide, and copolymers of vinyl alcohol. [0079] in some specific embodiments, the water soluble polymeric thickener (VVSPT) is selected from the group consisting of a neutralized poiyacrylic acid (e.g., neutralized

CARBOPOL® EZ3;Lubrizol), niethylceliulose (e.g., TICACEL® HV powder, TIC Gums), sodium carboxy niethylceliulose (e.g., CMC AQUALON® CMC Gum 7H4, Hercules, Inc.), xanthan gum (e.g., V ANGEL® Xanthan Gum), guar gum (e.g., Tic Gums, TICAGEL® onjac High Viscosity or Pre-Hydrated® Guar Gum 8/24, agglomerated guar gum), and carboxyvinyl polymer sodium salt, also known as pre-neutralized sodium polvacrylate (e.g., NEUTRAGEL® DA, 3V Sigma, or PNC™4G0, 3V Sigma), and powdered cross-linked polvacrylate (e.g., POLYGEL® CK, or POLYGEL® CA 3V Sigma).

[0080] In one embodiment, the water soluble polymeric thickener is neutralized poiyacrylic acid, for example, neutralized CARBOPOL® EZ3 (Lubrizol), hydrophobically modified crosslinked polvacrylate powder. In some aspects, the neutralized polyacrviic acid is provided by obtaining poiyacrylic acid neutralized with 90% of the theoretical

stoichiometric amount of sodium hydroxide =125 niL of 0.1 N NaOH per 1.00 g polymer.

[0081] In another embodiment, the water soluble polymeric thickener is niethylceliulose . In some aspects, the methyl cellulose is a high viscosity niethylceliulose, for example, TICACEL® I I V powder (TIC Gums).

[0082] In another embodiment, the water soluble polymeric thickener is sodium carboxyii ethylcellulose. In some aspects, the sodium carboxyniethylcelluiose for example, AQUALON® CMC Gum 7H4 (Hercules, Inc.) anionic water-soluble polymer, sodium carboxyniethylcelluiose (CMC).

[0083] In a further embodiment, the w ^r ater soluble polymeric thickener is a guar gum. In some aspects, the guar gum is selected from a high viscosity guar gum or a pre-hydrated guar gum. In one aspect, the guar gum is TICAGEL® Konjac High Viscosity Guar Gum (Tic Gums). In another aspect, the guar gum is Pre-Hydrated® Guar Gum 8/24, agglomerated guar gum (Tic Gums).

[0084] In a further embodiment, the water soluble polymeric thickener is a sodium poly acrylic acid salt. In a specific aspect, the water soluble polymeric thickener is

INEUTRAGEL® DA (3V Sigma, carboxyvinyl polymer sodium salt, pre-neutralized sodium poly aery late) and

[0085] In some embodiments, the water soluble polymeric thickener passes two or more, or preferably, three or more, of the following tests: (I ) exhibits continuity in the coalescence test; (2) exhibits a ratio of nonvolatile content in a lower liquid layer relative to nonvolatile content in an upper liquid layer of <2.0 in the centrifugation test; (3) does not exhibit settling in the settling test; and (4) exhibits fiiterabiiity in the filterability test.

[0086] in some embodiments, the heterogeneous particulate solid concentrate comprises between about 5 wt% - 45 wt%, 10 wt% - 40 wt%, or 15 wt% - 37 wt% water soluble polymeric thickener.

[0087] In some embodiments, preferred water soluble polymeric thickeners have intrinsic yield values of greater than about 500 cm, greater than about 1000 cm, and greater than about 1500 cm.

[0088] in some embodiments, the heterogeneous particulate solid concentrate

compositions comprise a water soluble polymeric thickener and further comprise a viscously inert material.

[0089] In certain embodiments, particles of the heterogeneous particulate solid concentrate comprise a water soluble polymeric thickener and a solid material that is viscously inert.

[0090] The term "viscously inert material" as used herein refers to a substance that when dissolved, suspended, or dispersed in distilled water at room temperature at 1 weight percent concentration provides a liquid that has less than 500 cps viscosity when measured using a Brookfield RV-DVE viscometer and #5 spindle at 5 rpm. In various aspects, the viscously inert material is selected from a water insoluble solid and/or a water soluble solid. In some embodiments, the viscously inert material is a solid that is insoluble in water at the

temperature of mixing or a solid that is soluble in water at the teniperatiire of mixing. In some embodiments, the viscously inert material is selected from one or more viscously inert materials.

[0091 ] in some embodiments, water soluble solids are non-ionic and are not salts. A non- limiting list of useful water soluble solids includes sugars; polysaccharides; modified or pre- gelatinized starches; and water soluble polymers with sufficiently low molecular weight so as not to provide greater than 500 cps viscosity when measured using a Brookfield RV -DVE viscometer and #5 spindle at 5 rpm,

[0092] In some embodiments, the viscously inert material is selected from one or more water insoluble solids. By water insoluble solid, it is meant that the solubility in water at room temperature is less than about 1 wt%.

[0093] in some embodiments, the viscously inert material is a solid that is insoluble in water at the temperature of mixing such as starch, clay, a water insoluble organic compound, a water insoluble inorganic compound, or any combination thereof. A non-limiting list of useful water insoluble solids includes clays; silicon dioxide; starch and starch derivatives; cellulose and cellulose derivatives; water insoluble polymers; and water insoluble organic compounds. [0094] In some embodiments, a particulate solid concentrate composition is provided containing from 30-85 wt%, 33-80 wt%, or 55-70 wt% total viscously inert material.

[0095] In some embodiments, the viscously inert material includes a clay. In some embodiments, the clay is selected from one or more of a Bentonite (montniorillonite), Hectorite, Magnesium Aluminum Silicate, Saponite, Sepiolite, Reidellite, Nontronite and Sauconite clay. In specific embodiments, the clay is a montmorillonite clay or a hectorite clay. For example, BENTONE® MA is an natural hectorite clay (Elementis Specialities Inc., Highstown NJ), BENTONE® EW NA is a natural hectorite clay (Elementis Specialities Inc., Highstown, NT), BENTONE® LT is a cellulose modified hectorite clay (Elementis Specialities Inc., Highstown, NJ), VOLCLAY® FD-181 is a natural sodium bentonite clay (American Celloid Company, Hoffman Estates 1L), and BENTONE® EW-NA is a montmorilionite clay. In some embodiments, a particulate solid concentrate composition is provided containing from 0-10 wt%, 2-8 wt%, or 3-7 wt% clay. [0096] In some embodiments, the viscously inert material in the particulate solid concentrate for preparing yield stress fluid for fire suppression comprises a starch or modified starch. In some embodiments, the starch is selected from corn, wheat, potato, tapioca, barley, arrowroot, or rice starch, or any combination of starches.

[0097] In some embodiments, the viscously inert material is an intumescent material. Intumescent compounds are defined as compounds that swell as a result of heat exposure, thus increasing in volume and decreasing in density. Intumescent compounds may also include compounds that decompose to give barrier layers when heated and compounds which dissolve and thicken aqueous compositions when heated. Starch forms suspensions when dispersed into water at room temperature, wherein the suspended particles become w ^r ater soluble and swellabie when heated in a process known as gelatinization.

[0098] For example, as an aqueous starch-containing dispersion is heated, the starch will begin to swell at approximately 65 to 70 degrees centigrade, turn into an amorphous, jelly-like mass at about 150 degrees centigrade, and then as water is driven off, will decompose at approximately 230 degrees centigrade and higher, giving off steam and C0 ₂ as decomposition products. This behavior contributes to the effectiveness in fire suppression following application of the yield stress fluid.

[0099] Polysaccharides and saccharides including gelatinized starch and simple sugars dehydrate when heated and are capable to be condensed to layers through which gases generated by heat exposure exhibit slow diffusion. In this way, starch provides two beneficial effects which are thickening and barrier layer formation. Preferred intumescent materials include starches. A particularly preferred intumescent material is cornstarch. In some embodiments, the viscously inert material is a cornstarch. In some aspects, the starch is Cornstarch (e.g., product B20F available from GPC Incorporated, Muscatine, Iowa). In some embodiments, a particulate solid concentrate composition is provided containing from 30-70 wt%, 33-65 wt%, 35-55 wt%, or at least 40 wt%, at least 50 wt% starch or at least 60 wt% starch.

[00100] In some embodiments, the viscously inert material comprises a water soluble solid. A non-limiting list of useful water soluble solids includes sugars; polysaccharides; modified or pre-gelatinized starches; and water soluble polymers with sufficiently low molecular weight so as not to provide greater than 500 cps viscosity when measured using a Brookfield RV-DVE viscometer and #5 spindle at 5 rpm. In some embodiments, the viscously inert material is a solid that is soluble in water at the temperature of mixing such as water soluble saccharides and polysaccharides. In some embodiments, the viscously inert material is a sugar. In some embodiments, the viscously inert material is a powdered sugar (e.g., C and H powdered sugar; or product of Alimentos y Maquila, S. A., Santa Catarina, NL Mexico).

[00101] In some embodiments, the viscously inert material is a selected from two or more viscously inert materials. In specific embodiments, a particulate solid concentrate is provided comprising a viscously inert material comprising a starch and a clay; or a starch and a. sugar. [00102] In some embodiments, a vegetable oil is included in the particulate solid concentrate composition. Any vegetable oil or mixture of vegetable oils can be utilized in the formulations described herein. V egetable oil is a triglyceride that can be degraded

biologically. Some examples of vegetable oil are cottonseed oil; flaxseed oil: soybean oil: safflower oil: sunflower oil; corn oil; canola oil; and peanut oil. The vegetable oil can be any useful grade including food grade, partially liydrogenated, hydrogenated, or winterized grade, for example. In some embodiments, the oil is selected from one or more of cottonseed oil, soybean oil, glycerin, soy methyl ester, paraffin or olefins (e.g., BioBase 200 material or mineral oil). Exemplary oils are selected from Canola oil (Roundy's Supermarkets,

Milwaukee, WI), Soybean oil 100 (Columbus Vegetable Oils, Des Plaines, IL), cottonseed oil 300 (non-winterized cottonseed oil, Columbus Vegetable Oils, Des Plaines, IL), cottonseed oil 310 (winterized cottonseed oil, Columbus Vegetable Oils, Des Plaines, IL), cottonseed, castor, fla seed, canola, rice bran, safflower and peanut oils are all commercially available from Soap Goods, Smyrna, GA. In various aspects, the oil is present in 0-5 wt%, 1-3 wt%, or about 2 wt%. In specific aspects, the particulate solid concentrate comprises one or more of a cottonseed oil and'or a soybean oil.

[00103] In some embodiments, the viscously inert material can include functional additives. Useful functional additives include dyes, colorants, opacifiers, antimicrobial compounds, buffers, anticorrosion agents, sequesterants, and intumescent compounds.

100104] in some embodiments, yield stress fluids for fire suppression are visible once applied. This is particularly important in the case of aerial application to avoid unnecessary repeat application and having gaps in the area of application. In some embodiments, yield stress fluids and/'or particulate solid concentrates, further comprise a colorant, an opacifier, or both. Preferred colorants are non-toxic and biodegradable and can include dyes and pigments. Particularly preferred dyes include rhodamine compounds such as Acid Red 52. Preferred opacifiers include titanium dioxide including surface treated titanium dioxide such as Dupont Ti-Pure R-706 and Dupont Ti-Pure R-900 and polymeric opacifiers such as Dow Ropaque AF-1353 and Arkema Celocor Opacifier. In some embodiments, the opacifier or colorant is present in the particulate solid concentrate at 0-5 wt%, 0.01-3 wt%, or 0.1-2 wt% of the composition.

[00105] In some embodiments, yield stress fluids for fire suppression are stable once mixed, preferably not diminishing more than 50% in yield stress over the course of two weeks and not exhibiting discoloration, separation, or microbial growth. [00106] In some embodiments, a particulate solid concentrate further comprises one or more antimicrobial or preservative compounds. Antimicrobial or preservative compounds are selected from any compounds that are effective to diminish microbiological activity in water. Preferred antimicrobial or preservative compounds are solid particulates with sufficient water solubility so as to be effective in water and are not fugitive and do not readily decompose. In some embodiments, the antimicrobial or preservative compound is selected from

preservatives evaluated here were citric acid, sorbic acid, potassium sorbate, mycoban calcium propionate, methyl paraben and propyl paraben (available, e.g., from Chem/Serv, Inc., Minneapolis, Minnesota). Particularly preferred antimicrobial or preservative compounds include paraben esters such as propyl paraben and methyl paraben. Propyl paraben is commercially available under the same trade name from Acme Hardesty

Oleochemicals, Blue Bell, PA. In specific aspects, the particulate solid concentrate comprises methyl paraben and/or propyl paraben. In some embodiments, the antimicrobial or preservative compound is employed in the particulate solid concentrate composition at from 0 - 10 wt%, 1 -8 wt%, or 3-7 wt%.

100107] Preferable yield stress fluids exhibit neutral, non-corrosive pH values from about pH 6 to about pH 8, preferably from about pH 6.5 to about pH 7.5, and are not destructive towards vegetation, metals, polymers, and painted objects.

[00108] In some embodiments, where the water soluble polymeric thickener comprises carboxyiic acid groups, buffering is provided by partial neutralization. For other polymers such as those based on acrylamide copolymers, poly ethers such as methyl cellulose and poly (ethylene oxide), N- vinyl pyrrolidone copolymers, and hydroxyl functional polymers such as polysaccharides and vinyl alcohol copolymers, it may be desirable to add a suitable buffer. Useful buffers include any that are effective in the pH range from about pH 6 to about pH 8. Particularly preferred buffers are based on hydroxides, such as NaOH, or KOH, and amine compounds such as tris(hydroxymethyl) aminomethane). In other embodiments, pH modifiers include phosphates, or carboxyiic acid compounds. For example, a particularly preferred buffer is partially neutralized citric acid.

[00109] In some embodiments, to minimize variability in the yield stress of fluids generated from solid concentrates, compounds are added to the solid concentrate that sequester multivalent ions. Preferred sequesterants include carboxyiic acid functional compounds such as EDTA, acrylic acid copolymers, and phosphate compounds.

[00110] For some applications it is preferable to add anticorrosion agents to the solid concentrate or yield stress fluid composition to minimize corrosion of metals. It is particularly important, to minimize the corrosion rate of metals that are materials of construction of aircraft in the case that yield stress fluid fire suppressants will be applied aerially. In some embodiments, the particulate solid concentrate further comprises one or more anticorrosion compounds selected from nitrates, molybdates, and benzoates. A.

particularly preferred corrosion inhibitor is sodium molybdate. In some embodiments, the particulate solid concentrate comprises 0-5 wt%, 0.01-3 wt% or about 0.05-2 wt% of a corrosion inhibitor.

[00111] The ratio of the volume of water soluble polymeric thickener to viscously inert particles is important both for practical preparation of heterogeneous particulate solid concentrates and for their distribution and dissolution into water. It is also believed that the ratio of the volume of water soluble polymeric thickener to viscously inert particles is critical to successful industrial processing to generate heterogeneous secondary particles. While not wishing to be bound by theory, it is believed that both heterogeneous particle manufacturing and use by dissolution become difficult as interstitial volume between viscously inert particles is exceeded by the volume of water soluble polymeric thickener. In the case that the amount of water soluble polymeric thickener exceeds the interstitial volume between viscously inert particles and exists increasingly on the surface of heterogeneous particles, when the water soluble polymeric thickener on the surfa ce of particles becomes wetted with water and mutually self-adhesive the heterogeneous particles also may become more mutually self- adhesive, leading to the formation of large contiguous masses.

[00112] Unlike particles of water insoluble, highly water swellabie polymers (e.g., SAPs) which by virtue of their crosslinked particulate nature exclude other particles from the particle interior even when swollen, water soluble polymeric thickeners become highly viscous liquids when in contact with water and can engulf other particles including viscously inert particles. [00113] Because viscously inert particles are not segregated to the peripheries of polymer domains of water soluble polymeric thickeners as in the case of water insoluble, highly water swellabie particulates, viscously inert particles are less efficient at interrupting contact between adjacent heterogenous particles comprising water soluble polymeric thickeners than adjacent heterogeneous particles comprising water insoluble, highly water swellabie polymers. Without being bound by theory, it is believed that the key to preparing successful heterogeneous particulate solid concentrates for yield stress fluids is minimizing contact between adjacent heterogeneous particles sufficiently so that they may remain separated or weakly associated during the manufacturing process to make them and so that they can be widely distributed in water without forming strong interparticle adhesive bonds such that they dissolve separately to give aqueous yield stress fluid fire suppressant compositions without forming large contiguous masses. Because of the physical strength of interparticle bonds, lumps formed by adhesive bonding between heterogeneous particles which comprise water soluble polymeric thickeners are more capable to be disintegrated by dissolution than by shearing such as is available by recirculating agitation. Because solubilization requires diffusion of water through the polymer which is typically very slow, lumps comprising water soluble polymeric thickeners once formed are often observed to never dissolve.

[00114] Problems with both heterogeneous particle formation and dissolution become exacerbated as the interstitial volume between viscously inert particles is exceeded by the volume of water soluble polymeric thickener. In the case of random loose packed monodisperse particles, the ratio of interstitial volume to particle volume is about 2 to 3 or about 40 % of the total occupied volume. Therefore, in some embodiments, preferable heterogeneous particulate solid concentrates comprise less than about 40 % by volume of water soluble polym eric thickener and greater than about 60 % by vol ume of viscously inert material. Because most particulate materials including those of viscously inert materials are poly disperse and exhibit a range of particle sizes, and because the volume packing of polydisperse materials is more efficient and provides less interstitial volume than

monodisperse materials, it is preferable to have an even lower volume ratio of water soluble polymeric thickener to viscously inert material. Preferred heterogeneous particulate solid concentrates comprise less than about 40 %, less than about 33 %, and less than about 25 % by volume water soluble polymeric thickener. Water soluble polymeric thickeners and viscously inert materials often have similar densities in which case preferred heterogeneous particulate solid concentrates comprise less than about 40 %, less than about 33 %, and less than about 25 % by weight water soluble polymeric thickener. [00115] Preferable heterogeneous particulate solid concentrates for yield stress fluids comprise a sufficient concentration of water soluble polymeric thickeners so as to pro vide a capability to give yield stress of about 2 cm with concentrations of solid concentrate less than 1 .5 weight percent, less than 5.25 weight, and less than 1 ,0 weight percent. Accordingly, preferable heterogeneous particulate solid concentrates comprise greater than about 5 weight percent, greater than about 10 weight percent, and greater than about 15 weight percent of water soluble polymeric thickener.

[00116] In some embodiments, a heterogeneous particulate solid concentrate is provided for forming a yield stress fluid composition for fire suppression, the composition comprising a water soluble polymeric thickener and a viscously inert material. In some embodiments, particles of the yield stress fluid particulate solid concentrate are heterogeneous, that is, they comprise more than one chemical compound.

[00117] Any method whereby conglomerates of similar or dissimilar primary particles may be formed may be useful in preparation of heterogeneous yield stress fluid solid concentrates including agglomeration, and compaction. Agglomeration refers to a process in which a liquid is combined with a particulate solid in such a way that clustering or aggregation of primary particles to give larger conglomerates results. Compaction refers to a process in which solid particles are subjected to compressive force resulting in adhesion to give larger conglomerates. In both agglomeration and compaction, overly large conglomerate particles may be crushed or comminuted to provide a desirable conglomerate particle size distribution.

[00118] In some embodiments, the particles may be used as prepared, or sorted, for example, by a screener. In some embodiments, the heterogeneous particulate solid concentrates have relatively less fine particles. While not wishing to be bound by theory, it is believed that fine particle size heterogeneous particles may be more strongly mutually self- adhesive, more difficult to be distributed into water before becoming adhesive, or both.

Removing fine particles from heterogeneous particulate solid concentrates improves the capability for complete and consistent mixing in water to give yield stress fluids. The relative amount, of fine particles can be expressed in terms of a D 10 diameter, which is defined as the particle diameter such that less than 10% of the particles by weight have diameters less than the D10 diameter.

[00119] In some embodiments, heterogeneous particulate solid concentrates are provided with D10 particle diameter (diameter such that less than 10% of the particles by weight have diameters less than the Dl 0 diameter) of greater than about 100 microns, greater than 200 microns, greater than 300 microns or greater than about, 350 microns. [00120] In some aspects, the particles are screened with screens of 16 mesh and 100 mesh, for example, to result in a heterogenous solid concentrate with particle size smaller than 16 mesh and larger than 100 mesh (0.15 mm to 1.2 mm particle size), or are screened to provide a particle size between 14 and 140 mesh (14 X 140), between 15 and 50 mesh (15 X 50), or between 35 and 50 mesh (35 X 50).

{00121 ] The concept of using aqueous yield stress fluids for fire suppression is that the composition is a liquid above a critical value of stress (the yield stress), allowing it to be pumped and sprayed, yet is a. solid in the absence of sufficient stress allowing it to coat and stay on vertical and inverted surfaces. Sufficiently stiff gels (gels with sufficiently high yield stress) form aqueous layers that are sufficiently thick so as to effectively cool and smother surfaces that are burning or prevent ignition on surfaces confronted with a source of ignition such as radiant heat or cinders,

[00122] Although yield stress fluids may be referred to as gels, they are in fact the subset of gels that have the property of being liquid in the situation of a sufficient value of shear stress (the yield stress). In common scientific usage, yield stress fluids may also be referred to as Bingham plastics or Bingham fluids. Familiar examples of yield stress fluids include ketchup, mayonnaise, latex paint, and mustard.

[00123] An important property of yield stress fluids used for fire suppression is the Bingham number. The Bingham number is the ratio of yield stress (also called gel strength) to flow viscosity. It is desirable to have the maximum possible Bingham number in order that the gel can be as strong and thick as possible as applied to burning surfaces or surfaces to protected from burning and yet have the lowest possible viscosity so as to allow being pumped through hundreds of feet of fire hose without, unacceptable pressure loss when under shear stress. The Bingham number of yield stress fluids useful for large scale fire suppression is orders of magnitude greater than the Bingham number of common yield stress fluids such as ketchup, mayonnaise, latex paint, and mustard.

[00124] In some embodiments, a method for method for forming a yield stress fluid composition for fire suppression is provided comprising adding an aqueous fluid to a fluid reservoir; providing agitation in the fluid reservoir by withdrawing and returning the fluid through an external circuit; and introducing a heterogeneous particulate solid concentrate into the fluid in the reservoir while providing agitation to form a yield stress fluid composition for fire suppression.

100125] in some embodiments, the aqueous fluid used in the method for forming a yield stress fluid is water. In some aspects, the water used in the method for forming a yield stress fluid is selected from distilled water, RO water, softened tap water, un-softened tap water, well water, or surface water. Generally as the water hardness increases, the viscosity level of the yield stress fluid decreases. Therefore, in some embodiments, the water has < 600, < 500, < 400, or preferably < 200 Total Dissolved Solids (TDS). In some embodiments, the water is softened water, reverse osmosis (RO) water, or distilled water. Water containing dissolved minerals such as calcium bicarbonate and magnesium bicarbonate may diminish the yield stress of fire suppressants, especially in the case of carboxylic acid functional water soluble polymeric thickeners.

[00126] In some embodiments, to minimize variability in the yield stress of fluids generated from particulate solid concentrates, compounds are added to the water or yield stress fluid that sequester multivalent ions. Preferred sequesterants include carboxylic acid functional compounds such as EDTA, acrylic acid copolymers, and phosphate compounds.

[00127] In some embodiments, a method for forming a yield stress fluid composition for fire suppression is provided, wherein the method comprises adding an aqueous fluid to a fluid reservoir; providing agitation in the fluid reservoir by withdrawing and returning the fluid through an external circuit; and introducing a heterogeneous particulate solid concentrate into the fluid in the reservoir while providing agitation to form a yield stress fluid composition for fire suppression.

[00128] The reservoir may be any reservoir fitted for recirculating agitation. Chemical manufacturing to produce products such as personal care products which comprise solutions of water soluble polymeric thickeners typically employs vessels designed so as to give good mixing which are generally equipped with rotary mixers. By rotary mixer, it is meant a rotating impeller or rotor, or a series of such impellers or rotors. Rotary mixing devices are characterized by comprising a rotating cylindrical shaft with one end inside a fluid reservoir, wherein the shaft end inside the fluid reservoir lacks cylindrical symmetry as in a propeller. A stationary component referred to as a stator may be used in combination with the rotor in rotor/stator devices which constitute a subset of the group of rotary mixing devices.

100129] By contrast, agitation that is available to dissolve yield stress polymers and compositions outside of chemical manufacturing facilities preferably does not comprise a rotar}' mixer. Instead, preferable agitation is provided by pumping liquid out of and back into a reservoir or a tank. Such systems are generally characterized as comprising a fluid reservoir plus an external circuit plus a. means of providing flow in the external circuit such as by a pump. Preferred pumps include diaphragm pumps, centrifugal pumps, rotary gear pumps, rotary vane pumps, and piston pumps. Agitation that is provided by a system of a fluid reservoir plus external circuit and pump is called recirculating agitation.

[00130] According to the present disclosure, solid concentrates comprising heterogeneous particulates are introduced into a reservoir containing water where agitation is provided by recirculating agitation. By recirculating agitation, it is meant that the fluid is withdrawn from the reservoir via a pump and pumped back into the reservoir. The solid concentrate can be introduced to the reservoir using an eductor as described in assignee's patent application WO 2012096719A1 "Eductor System," incorporated herein by reference, or poured onto the surface of the recirculating water. Preferably, the solid concentrate is poured onto the surface of the recircul ating water which avoids the requirement of the eductor and also probl ems associated with the use of eductors such as introduction of air into the reservoir, which can result in foaming.

[00131] In one embodiment, a method is provided for the preparation of a yield stress fluid from a solid concentrates comprising recirculating agitation. In some recirculating agitation systems, the flow rate of water is sufficient, such that the volume of liquid in the reservoir is circulated through the pump and external circuit, once every 30 seconds, once every 3 minutes, once every 6 minutes, or once every 12 minutes.

[00132] In some aspects, the recirculating agitation comprises a vertical return line. In some recirculating agitation systems, the return flow is vertical and oriented either upwards from the bottom of the reservoir or downwards from the top of the reservoir. In some recirculating agitation systems, the return flow has a vertical orientation with a horizontal deflectio angle Θ of between 1 degree and 89 degrees from vertical, or between 5 degrees and 30 degrees from vertical. In some specific aspects, the recirculating agitation comprises a vertical return line extending below the surface of the fluid. In some recirculating agitation systems, the horizontal deflection of the return flow is sufficient to provide a tangential flow and circulation of the water in the reservoir. 00133] In some embodiments, the reservoir fitted for recirculating agitation is selected from 1 gal-5,000 gal, 2-3,000 gal, or 5-2,000 gal capacity tank. In specific embodiments, the reservoir is selected from a 5 gal, 72 gal, 134 gal, 200 gal, 450 gal, 1 ,000 gal, 1 ,600 gal, 2,000 gal, or 2,200 gal reservoir. In specific aspects, the reservoir fitted with means for

recirculating agitation comprises a vertical return line. In some aspects, the vertical return line extends beneath the surface of fluid in the filled reservoir. The reservoir may be made of any material appropriate for handling aqueous solutions. In some aspects, the reservoir is made from plastic. In specific aspects, the reservoir is selected from a polyethylene, polypropylene, or reinforced PVC reservoir.

[00134] FIG. 1 A shows a schematic diagram of a reservoir fitted with a means for recirculating agitation for use as a mixing apparatus for generation of yield stress fluids. A reservoir 10, is fitted with a centrifugal pump 30, with an outflow line 40, and a vertical return line 20. In some embodiments, the return line extends beneath the surface of the fluid in the reservoir.

[00135] FIG. I B shows a reservoir fitted with a centrifugal pump 30, an outflow line 40, with an off vertical angle of return line 20 indicated at Θ. In some reservoir recirculating agitation systems, the return flow has a vertical orientation with a horizontal deflection angle Θ of between 1 degree and 89 degrees from vertical. In one embodiment, the return line 20 extends below the surface of the water or yield stress fluid present in the reservoir 10.

[00136] FIG . I C shows a drawing of a 5 gallon plastic pail reservoir 10, is fitted with a centrifugal pump 30, with an outflow line 40, and a vertical return line 20, for use as a mixing apparatus for generation of yield stress fluids. The arrows indicate the direction of flow. [00137] FIG. ID shows a 200 gallon reservoir skid unit 10 fitted with a means for recirculating agitation for use as a mixing apparatus for generation of yield stress fluids. The reservoir 10 is fitted with an upper port 20 for top loading of materials, e.g., solid concentrate, equipped with centrifugal pump 40, vertical return line 30, gas tank 90, horizontal outlets 80 from pressurized manifold 120, pump outflow 50, eductors for addition of materials at 60, 70, and 100, and horizontal return 110. The apparatus can be used in 4 modes including (l)top load, horizontal exit and horizontal return; (2) top loading, horizontal exit and vertical return; (3) educator loading, horizontal exit and horizontal return; and (4) educator loading, horizontal exit and vertical return. In some embodiments, the reservoir vertical return line 30 extends beneath the surface of the fluid in the reservoir during recirculating agitation. In some embodiments, the reservoir horizontal return line 1 10 extends beneath the surface of the fluid in the reservoir during recirculating agitation. The 200 gal skid unit is appropriate for on-site use in fire-fighting, e.g., appropriate for use in a pick-up truck, or forest service truck.

[00138] In some embodiments, the means for providing agitation to the reservoir comprises means for external recirculating agitation.

[00139] In one embodiment, a yield stress fluid particulate solid concentrate composition is provided comprising a water soluble polymeric thickener and a viscously inert material that can be effectively mixed with water using recirculating agitation without formation of large contiguous slowly dissolving agglomerates. [00140] In some embodiments, the yield stress fluid solid concentrate composition comprises particles that are heterogeneous, that, is, they comprise more than one chemical compound.

[00141] In some embodiments, the water soluble polymeric thickener is an alkali metal salt of a poly acrylic acid copolymer including lightly cross-linked copolymers. [00142] In some embodiments, the yield stress fluid heterogenous particulate solid concentrate is characterized by having conglomerate particles, that is, particles which comprise smaller primary particles that are joined together. For example, FIG. 2A shows a scanning electron microscope (SEM) image of an intact heterogenous particulate solid concentrate conglomerate particle prepared according to Example 2. Smaller primary particles are shown on the surface of the intact particle.

[00143] In some embodiments, the heterogenous particulate solid concentrate comprising a water soluble polymeric thickener and a viscously inert material is characterized by having conglomerate particles with a core-shell structure. In some embodiments, the solid concentrate conglomerate particles have a core that comprises a relatively higher

concentration of water soluble polymeric thickener and a shell that comprises a relatively higher concentration of viscously inert material. In other embodiments, the solid concentrate conglomerate particles have a core that comprises a relatively higher concentration of viscously inert material and a shell that comprises a relatively higher concentration of water soluble polymeric thickener.

[00144] Evidence for one type of particle core-shell structure is provided by SEM images in FIGs. 2B and 2C showing images of a particle fractured by crushing. FIG. 2B shows a scanning electron microscope (SEM) image of a. fractured heterogenous particulate solid concentrate conglomerate particle at x400. In FIG. 2B, Point 1 shows an interior core of a fractured particle, whereas Point 2 shows an exterior shell surface of the particle. FIG. 2C shows a fractured particle at a different magnification x250. The fractured images show distinct conglomerate particles at the exterior, and the interior, of the fractured particles.

[00145] Further evidence for one type of particulate core-shell structure is provided by Energy Dispersive X-ray Spectroscopy (EDS) elemental analysis performed at the points 1 , 2 and 3 indicated by the arrows in FIG 2C. FIG. 3A shows EDS spectrum at point 1 , FIG. 3B shows EDS spectrum at point 2, and FIG. 3C shows EDS spectrum at point 3. The EDS spectmm at, a surface (shell) point 3 is distinctly different than that at an interior (core) point 1. For example, the relative intensity of the oxygen peak O is greater than the carbon peak Cat shell point 3, shown in FIG. 3C. In contrast, the C peak is more intense than the O peak at core point 1 , as shown in FIG. 3 A. FIG. 3C EDS at shell point 3 also shows higher intensities of Si, Mg and Na peaks relative to the C peak, when compared to FIG. 3A EDS of core point 1 . The elemental analysis of the particle of Exampl e 2 indicates a core-shell structure comprising a relatively higher concentration of water soluble polymeric thickener in the core (e.g., NEUTRAGEL® DA) and a relatively higher concentration of viscously inert material (e.g., starch and clay) in the shell.

[00146] In other embodiments, a method is provided for making a yield stress fluid by a process of mixing water with a yield stress fluid solid concentrate using recirculating agitation wherein the solid concentrate comprises a water soluble polymeric thickener. By mixing using recirculating agitation, it is meant that the solid concentrate is mixed into water in a process wherein the agitation is provided by withdrawing and returning fluid from a reservoir using a. pump. According to the present invention, solid concentrates are provided such that recirculating agitation is effective to dissolve the water soluble polymeric thickener component of the particulate solid concentrate giving a thickened fluid with a useful value of yield stress with the substantial avoidance of the formation of large coalesced masses. While not wishing to be bound by theory, it is believed that heterogeneous particulates are capable to be widely distributed in water before becoming beginning to dissolve in with water and becoming mutually self-adhesive. [00147] In some embodiments, it is preferable to provide a yield stress fluid composition for fire suppression comprising 2 cm of yield stress in 200 gallons of moderately hard water (250 ppni total dissolved solids as measured by conductivity) using less than 20 pounds (1.2 wt%), preferably less than 18 pounds (1.08 wt %), and preferably less than 16 pounds (0.96 wt %) of solid concentrate wherein the solid concentrate comprises greater than about 60 percent by weight of functional ingredients such as viscously inert in tumescent compounds including starch and sugars.

[00148] To achieve a desirable level of thickening, it is preferable to use water soluble polymeric thickeners that have sufficiently high molecular weight so as to provide effective thickening capability at low concentrations. Because the thickening that is important for fire suppression is yield stress, the thickening capability of water soluble polymeric thickeners is best expressed as intrinsic yield value. Intrinsic yield value of water soluble polymeric thickeners is similar to intrinsic viscosity which expresses the viscosity of a standardized concentration of polymer except that the metric of thickness is yield stress instead of viscosity. Also, as opposed to intrinsic viscosity which expresses differences in viscosity for standardized concentrations, intrinsic yield value expresses differences in polymer concentration required to provide a standardized value of yield stress. This latter difference is important because yield stress may vary steeply as a function of polymer concentration in the range of useful yield stress for fire suppression, and may vary differently for different polymer architecture. Preferably, intrinsic yield value is expressed in units of cm of yield stress per weight fraction polymer as measured in distilled water and taken at the units of cm.

EXAMPLES

100149] Yield stress polymer property tests:

[00150] Liquid height yield stress capability test. This test measures the concentration of yield stress polymer required to give provide a specified value of yield stress. Yield stress polymer aqueous gels were prepared by sprinkling 4.0 g of polymer onto the surface of 396 g of distilled water and blending for one minute using an immersion blender ( itchenAid 2- Speed immersion Hand Blender) operating on the lowest speed setting. The resulting gels were sequentially diluted with additional distilled water and the yield stress measured by pouring about 8 ounces of fluid into a 16 ounce cold beverage cup with a 0.4 cm hole in the middle of the base. The fluid was allowed to drain from the bottom of the cup and the height of the fluid was measured when the fluid dripping rate was approximately 1 drop per second. The concentration at which the yield stress was 1.8 to 2.2 cm was recorded. In some cases the intrinsic yield value of the polymer was sufficiently low that greater than 1 weight percent polymer solutions were required to achieve greater than 2 cm of yield stress as the starting point for sequential dilution. 001S1] Rheometer yield stress capability test. Yield stress polymer gels were prepared with 0.08, 0.12, 0.16, 0.20, and 0.24 weight percent NEUTRAGEL® DA in distilled water. A sweep from high to low shear rate of apparent shear stress versus shear rate was measured using a TA Instruments AR-G2 viscometer with 40 mm diameter roughened (using adhesively bonded 600 grit sandpaper) parallel plates and 1000 micron gap for each gel. The yield stress was recorded as the plateau value of apparent shear stress which has plateaued for each sample by the time the shear rate had dropped to approximately 0.01 sec ^{" 1} . The yield stress was plotted versus concentration and extrapolated from the two closest points to determine the concentration of yield stress polymer required to give yield stress 50 Pa. For NEIJTRAGEL® DA water soluble polymeric thickener, 0.21 weight percent was required. In a separate test, the procedure was repeated using 0.40, 0.60, 0.80, 1.00, 1.20, and 1.40 weight percent FIREICE® (92 - 98 weight percent potassium polyacrylate) and the concentration required to give yield stress = 50 Pa was determined to be 0.86 weight percent. In a separate test, the procedure was repeated using 0.40, 0.50, 0,60, 0.70, and 0.80 weight percent AQUASGRB® Premium SAP (92 - 98 weight percent potassium polyacrylate) and the concentration required to give yield stress = 50 Pa was determined to be 0.39 weight percent.

[00152] A number of thickening agents were subjected to each of the following tests following dissolution or suspension in water as described below to classify the material as either a water soluble polymeric thickener (WSPT), or as a water insoluble, highly water sweliable polymer (WTHWS), Water soluble polymeric thickeners were employed in the heterogenous particulate solid concentrates described below.

[00153] Filterability Test. Aqueous polymer compositions with 0.1 weight percent polymer were prepared by sprinkling 0,5 g of polymer onto the surface of 499 g of distilled water and blending for two minutes using an immersion blender (KitchenAid 2-Speed Immersion Hand Blender) operating on the lowest speed setting. After mixing was complete, the aqueous polymer composition was allowed to stand for one hour. After one hour, 396 g of the aqueous polymer composition was blended for 30 seconds, 4.00 g of 10% NaCl solution in distilled water added, and blending was continued for an 30 seconds. Aqueous polymer composition thus prepared (150 g) was filtered through a tared 70 mm Whatman Grade 1 disposable FilterCup filter funnel (available from VWR International, Radnor, PA) into a 250 ml, filtering flask evacuated using a Thermo Scientific hand operated vacuum pump (available from VWR International) at maximum vacuum (approximately 635 Torr, with hand pumping to maintain the vacuum throughout the period of filtering) until filtration was complete or for up to 10 minutes for slowly filtering compositions. If less than 150 g of liquid filtered in 10 minutes, the amount of filtrate collected in 10 minutes was noted. The weight percent nonvolatile material in the filtrate and in unfiltered aqueous polymer composition was determined by evaporation in an aluminum pan on a hot plate at 325 F. According to this test, aqueous polymer compositions are considered filterable solutions if all of the liquid composition passes through the filter in 10 minutes and the weight percent polymer in the filtrate is greater than 50% of that of the unfilterecl aqueous composition (i.e., greater than 0.05 weight percent). In some embodiments, the water soluble polymeric thickener exhibits filterability in the filterability test. [00154] Settling Test. IJnfiltered portions of the aqueous polymer compositions prepared for the Filterability test with 0.10 weight percent polymer and with 0.10 weight percent polymer plus 0.10 weight percent NaCl were allowed to stand for 24 hours. Settling in samples is observed as a line of demarcation above which the liquid is clear and not hazy and through which 1 1 point text can be read and below which is hazy and text cannot be read. In some embodiments, the water soluble polymeric thickener does not exhibit settling in the settling test,

[00155] Coalescence Test. Unfiltered portions of the aqueous polymer compositions prepared for the Filterability test with 0, 10 weight percent polymer were coated onto glass substrates using a #225 Mayer rod and dried at 50 C for one hour. Samples were observed for film formation according to the description in ASTM Standard D2354 - 10 Standard Test Method for Minimum Film Formation Temperature (MFFT) of Emulsion V ehicles, that is, after the film has dried, observe for discontinuity as evidenced by whitening or cracking or both. In some embodiments, the water soluble polymeric thickener exhibits continuity, in other words, minimal to no evidence of whitening and/or cracking, in the coalescence test. [00156] Centrifugation test. Yield stress polymer aqueous compositions were prepared using distilled water with concentration of yield stress polymer equivalent to that which gives yield stress = 2 cm. Samples of the yield stress polymer compositions (50.0 g) were placed into a 50 mL conical bottom polypropylene centrifuge tube and centrifuged using an IEC Model CL clinical laboratory centrifuge with a swing type rotor operating at 2400 rpm for 60 minutes. The relative centrifugal force (average radius of rotation of the 50 mL centrifuge tube = 8.9 cm) was 600 x g. After centrifugation, samples were observed for evidence of separation into two discrete phases and if observed, the volume in mL of the upper layer was recorded. The upper 50.0 mL of liquid was carefully removed from the top of the tube using a disposable pipette and the weight % nonvolatile content was determined by evaporation to constant weight on a hot plate set to 135 C. The lower 10.0 mL of centrifuge tube contents were removed by inserting a plastic pipette to the 45 mL mark (5 mL from bottom) and carefully removing liquid and the nonvolatile content was also determined by evaporation to constant weight at 135 C, The ratio of nonvolatile content in the lower liquid layer to that in the upper liquid layers was calculated as a measure of resistance to settling under centrifugation, with lower numbers indicating a greater resistance to settling. In some embodiments, the water soluble polymeric thickener exhibits a ratio of nonvolatile content in the lower liquid layer to that in the upper liquid layer of <2.0, < 1.7, or preferably < 1.5 in the centrifugation test.

[00157] A number of thickening agents were subjected to ea ch of the yield stress polymer property tests following dissolution in water as described. Results of yield stress polymer property tests are presented in Table 1.

Table 1. Summaiy of the results of yield stress polymer property tests.

WSPT - water soluble polymeric thickener; WIHWS = water insoluble, highly water swellable; * neutralized with 90% of the theoretical stoichiometric amount of sodium hydroxide (125 mL of 0.1 N NaOH per 1.00 g polymer)

00158] The results shown in Table I illustrate that Carbopol EZ-3 (neutralized polyacrylic acid), Ticacel HV (methyl cellulose), Aqualon CMC Gum 7H4 (sodium carboxy methyl cellulose), V ANGEL Xanthan Gum (xanthan gum), NEUTRAGEL® DA (sodium

polyacrylate), Ticagel onnjac High Viscosity Guar Gum (guar gum), and Tic Gums Pre- Hydrated® Guar Gum 8/24 are water soluble polymeric thickening agents. Table 1 also shows that AQUASO B® (sodium polyacrylate), FIREICE® (potassium polyacrylate), and AquaGel (potassium polyacrylate) are water insoluble, highly water swellable polymers.

[00159] Thus, the water soluble polymeric thickeners each passed three or more, of the following tests: (1 ) exhibited continuity in the coalescence test; (2) exhibited a ratio of nonvolatile content in a lower liquid layer relative to nonvolatile content in an upper liquid layer of <2.0 in the centrifugation test; (3) did not exhibit settling in the settling test; and (4) exhibited filterability in the filterability test.

[00160] Tests of yield stress fire suppressant solid concentrates: [00161] Solid Concentrate yield stress capability test. This test measures the concentration of solid concentrate required to give a yield stress of 2 mm, using the procedure of the liquid height yield stress capability test as described above and using unsoftened tap water. The unsoftened tap water was the same water as used for the recirculating agitation mixing test described below. For all solid concentrates, the water Total Dissolved Solids (TDS) measured using a T.D.S mini handheld meter (model TDS - 999 mini, product of Captive Purity, available from Marine Depot, Garden Grove, CA ) was between 200 and 400 ppm.

[00162] immersion blender viscosity test. The amount of solid concentrate needed to provide the aqueous composition with yield stress of 2 cm was determined as described for the yield stress polymers in the Liquid height yield stress capability test. Accordingly, 4.0 g of solid concentrate was added to the top of 396 g of unsoftened tap water or 8.0 g of solid concentrate was added to 392 g of unsoftened tap water in the case of solid concentrates with lower intrinsic yield values and the solid concentrate combined with the water by blending for one minute using a KitchenAid 2-Speed Immersion Hand Blender at the lowest speed setting. The resulting yield stress fluids were sequentially diluted with additional unsoftened water until the concentration which gave yield stress = 1.8 to 2.2 cm was reached. Subsequently the viscosity was measured using a Brookfield RV -DVE viscometer using a #5 spindle rotating at 5 rpm. [00163] Recirculating agitation mixing test. The mixing behavior of solid concentrate in the amount needed to provide the concentration of solid concentrate with yield stress of 2 cm as determined above was determined as follows: A 5 gallon pail was fitted with an outlet consisting of nominal ½ inch diameter PVC pipe 1 terminating about one inch from the bottom of the pail and leading to a ½ hp centrifugal pump about 4 inches from the pail, as shown in FIG, IC. A return line consisting of nominal ½ inch diameter PVC pipe extended vertically from the centrifugal pump for 17 inches and then horizontally back to the top of the pail through 7 inches of nominal ½ inch diameter PVC pipe. The terminus of the return line was constructed from 3/8 inch galvanized pipe and was directed 10° or 20 from vertical (off vertical angle Θ of return line) about, 2 inches from, the wall of the pail. In this way most of the flow within the pail was vertical while the 1.0° or 20 departure from, vertical provided a moderate tangential flow. A diagram, of the recirculating agitation mixing test apparatus is shown in FIG. I C. According to this mixing method no vortex exists when the pump is nan with 4 gallons of water in the system, with a flow rate of 12.8 gallons per minute. With 4.0 gall ons of water in the mix apparatus and the pump running at 12.8 gal lons per minute, solid concentrate samples were introduced into the middle of the pail through a funnel that had been cut to size so as to allow complete powder addition in approximately three seconds. The amount of fire suppressant solid concentrate added was sufficient to provide a yield stress as measured by the cup method of 2.0 cm. After addition of the solid concentrate, the viscosity of the mixture was measured in two minute increments using a Brookfield RV-DVE viscometer using a #5 spindle rotating at 5 rpm. The plateau viscosity was determined as the value of viscosity at which there was less than about 5% change in viscosity between measurements separated by two minutes. The presence or absence of undispersed solid concentrate during the mixing experiment was noted. 001 4] The mixing test was repeated three times for each solid concentrate sample to assess reproducibility. Variability in the plateau viscosity amongst the repeated runs is indicative of incomplete dissolution in runs with low viscosity, that is, some solid concentrate has formed coalesced masses and is not dispersed into water.

[00165] Large scale mixing test. The mixing behavior of solid concentrate in the amount needed to provide the yield stress of 2 cm as determined above was determined as follows: A 200 gallon skid unit (available from EarthClean Corporation, South Saint Paul MN) equipped with centrifugal pump (model PB18-2525F, product of Waterous, South Saint Paul MN) powered by an 18 hp Briggs and Straiten gasoline engine was filled to capacity with 200 gallons of untreated municipal water. The TDS value of the water was determined using a handheld TDS meter and a small amount of water withdrawn to determine the concentration of solid concentrate required to give a yield stress of 2 cm. With the fluid path selected to be horizontal return to the tank and the 18 hp motor operating at full throttle, the amount of solid concentrate required to give yield stress = 2 cm was poured from a plastic container with a 5 inch lid perforated with a plurality of 3/8 inch holes through the opening in the top of the skid unit. Pouring the solid concentrates through the perforated lid was effective to admit the required quantity of solid concentrate to the tank over a period of about 90 to 120 seconds. With the motor operating at full throttle, the viscosity of the fluid in the tank was measured using a Brookfield RV-DVE viscometer with a #5 spindle rotating at 5 rpm at approximately 2 minute intervals and the fluid was observed though the top opening to determine if undissolved material was present. [00166] Large scale pumping and spraying test. Solid concentrate was mixed with water as per the Large scale mixing test as described above. After the recirculating fluid had reached constant viscosity and no undissolved material was observed to be present, the fluid flow was redirected from recirculation to a hose line of 100 feet of 1 .5 inch diameter municipal fire hose equipped with a hydrostatic pressure gauge at the distal end and a Protec No. 366 selectable gallonage nozzle (available from Protec Firefighting, Inc., Markham Ontario) with the flow rate set to 95 gallons/minute and the spray pattern set to fan spray. The gasoline motor was throttled back to give a manifold pressure equal to 125 psi and the hydrostatic pressure in the distal end of the hose was measured to determine the hydrostatic pumping pressure drop of the fire suppressant yield stress fluid for comparison to water (for water the hydrostatic pressure was 105 psi at the nozzle with manifold pressure = 125 psi and nozzle flow rate setting set to nominally 95 gallons/ ^' min).

[00167] Comparative Example A. NEUTRAGEL® DA (sodium poiyacrylate) was obtained from 3V Corporation, Georgetown SC and used as received. The concentration required to give yield stress ^:=: 2 cm using the liquid height yield stress capability test was 0.37 weight percent (400 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 8160 cps. The dissolution properties of NEUTRAGEL® DA were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 4. [00168] Comparative Example B. FIREICE® (potassium poiyacrylate) was obtained from GeiTech Corporation, Jupiter FL and used as received. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.96 weight percent (400 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 4400 cps. The dissolution properties of the FIREICE® solid concentrate sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 5.

[00169] The dissolution properties of the FIREICE® solid concentrate were evaluated according to the large scale mixing test and the results are shown in Table 2.

[00170] Table 2. Observations for large scale mixing of FIREICE® solid concentrate (Comparative Example B).

one or two football sized

19 1600

agglomerates

at least one football sized

26 1840

agglomerate

changed water return to vertical and

30 1840

broke up agglomerates by hand

40 2480 no agglomerates were observed

[00171] According to this test, 16.7 pounds of FIREICE® were poured over a period of 125 seconds onto the top of 200 gallons of recirculating water with 405 ppm TDS and temperature ^::: 19 C using horizontal return to the tank and with the pump operating at full throttle. It was observed that the viscosity did not reach the ultimate value in 30 minutes of mixing ami that agglomerated clumps of material larger than a football remained. Subsequent to mixing for 30 minutes without intervention and with horizontal return to the tank, clumps of agglomerated polymer were fairly easily broken up by hand and the return flow to the tank was changed to vertical and within about 10 minutes the dispersion of the polymer into water was complete and effective to give a uniform, slightly grainy translucent yield stress fluid with the consistency of a fine slurry and viscosity (measured using a Brookfiekl RV viscometer with a #5 spindle at 5 rpm) was 1840 cps at 32 C. The viscosity of the fluid as a function of time is shown in FIG. 6. After mixing was complete (45 minutes after solid addition), the FIREICE® composition was pumped from the tank with manifold pressure = 125. The pressure at the nozzle was 80 psi and the pressure drop in 100 feet of 1.5 inch municipal hose was 45 psi.

1001 2] What this example shows is that potassium polyacrylate super absorbent polymer is not capable to be reliably dissolved by recirculating agitation, however with intervention including manual comminution of agglomerates and vertical return to the tank, adequate dissolution is possible over a period of 40 minutes. [00173] In a separate test, the pumpability of FIREICE® fire suppressant yield stress fluid was again determined. FIREICE® (16.0 pounds) was poured slowly over about 9 minutes onto the top of 200 gallons of recirculating water with 366 ppni TDS and temperature = 18°C using vertical return to the tank and with the pump operating at full throttle. In this way, agglomerates were avoided and the batch reached a plateau viscosity of 2880 cps within 20 minutes. With the manifold pressure at 125 psi, the FIREICE® yield stress fluid was pumped through 100 feet of 1.5 inch municipal fire hose and sprayed with the nozzle flow setting set at nominally 95 gallons with a nozzle pressure = 80 psi (45 psi pressure drop). It took 90 seconds to pump 100 gallons of liquid Comparative Example C, AquaGei (potassium polyacrylate) was obtained from ICL Corporation, St. Louis MO and used as received. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.85 weight percent (200 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 4800 cps. The dissolution properties of the AquaGei K solid concentrate sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG.

[00174] Comparative Example D. AQUASORB® Premium. SAP (sodium polyacrylate) was obtained from Ark Enterprises, Peculiar MO and used as received. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.70 weight percent (250 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 2400 cps. The dissolution properties of the AQUASORB® Premium SAP solid concentrate sample was evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 8. [00175] Comparative Example E. Cornstarch (1050 pounds, product B20F available from GPC Incorporated Muscatine LA), NEUTRAGEL® DA sodium poly acrylic acid salt (720 pounds), propyl paraben (100 pounds, product of Acme Hardesty Company, Blue Bell PA), and montmorillonite clay (100 pounds, product BENTONE® EW-NA available from

Elementis Specialties, Elementis Specialties, East Windsor, NJ ) were added to a 70 ft. ³ ribbon blender and mixed for 20 minutes. With the ribbon blender running Cottonseed Oil (30 pounds, product Butcher Boy Non-winterized Cottonseed Oil available from Columbus Vegetable Oils, Des Piaines, IL) was sprayed onto the mixture over the course of about twenty minutes and ribbon blending was continued for another five minutes to give an unagglomerated solid concentrate as a fine, dusty powder with a flour like consistency. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.90 weight percent (400 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 7600 cps. The dissolution properties of the solid concentrate sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG, 9.

[00176] Comparative Example F (yield stress fluid solid concentrate with hydrophobic agglomerating agent according to US Patent 8,192,653). Preblend: Cornstarch (GPC B20F Corn Starch, 50.0 g) and NaOH (JT Baker Caustic Soda Pearls, 50. Og) were added to a rock tumbler (model 635, product of MMX NSI International, Inc., Farmingdale NY), tumbled at 60 rpm for 30 minutes, and allowed to stand for 24 hours. The process of making preblend was repeated two more times. Solid Concentrate: Polyacrylic acid (Lubrizol EZ-3, 349 g) was added to a cement mixer (Red Lion model 636001 BigCat, Concrete Mixer) rotating at 30 rpm. Olefinic hydrocarbon liquid (Biobase 200, product of Shrieve Chemical Products, The Woodlands TX, 16.0 g) was sprayed onto the mixing Lubrizol EZ-3 as a fine mist, using a hand pump spray bottle and the mixer allowed to rotate for 10 minutes. Com starch (427 g of GPC B20F Corn Starch) was added and mixing continued for 50 minutes, and then 123 g of preblend was added and 84 additional grams of olefinic hydrocarbon liquid sprayed onto the product over the course of 10 minutes. Mixing was allowed to continue for 30 minutes after the final olefinic hydrocarbon liquid addition and the product was passed through a US mesh size equivalent No. 8 sieve to give a solid concentrate agglomerated with 10 weight % hydrophobic agglomerating liquid. The concentration required to give yield stress ^::: 2 cm using the liquid height yield stress capability test was 0.65 weight percent (220 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 9680 cps. The dissolution properties of the yield stress fluid solid concentrate with hydrophobic

agglomerating agent sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 10.

[00177] Comparative Example G. Ashland Aqualon CMC 7H4 sodium carboxy methyl cellulose was obtained from Ashland Specialty Ingredients, Covington Y and used as received. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 1.00 weight percent (250 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 6240 cps. The dissolution properties of the Ashland Aqualon CMC 7H4 sodium carboxy methyl cellulose solid concentrate sample was evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 1 1.

[00178] Comparative Example H. Vanzan Xanthan Gum was obtained from Vanderbilt Mineral, Norwalk CT and used as received. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.80 weight percent (250 ppm ^' TDS water). The viscosity measured using the immersion blender viscosity test was 7520 cps. The dissolution properties of the V anzan Xanthan Gum solid concentrate was evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 12. Comparative Example I. Ticagel onjac High Viscosity guar gum was obtained from Tic Gums, Belcamp MD and used as received. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.75 weight percent (250 ppm TDS water). The viscosity measured using the immersion blender viscosity test was 5440 cps. The dissolution properties of the Ticagel Konjac High Viscosity guar gum. solid concentrate sample was evaluated according to the recirculating agitation mixing test described above. The plot, of viscosity vs mixing time for each of three runs is shown in FIG. 53. [00179] Example 1. Cornstarch (420 pounds, product B20F available from GPC

Incorporated), NEUTRAGEL® DA sodium poly acrylic acid salt (288 pounds), propyl paraben (40 pounds), and BENTONE© EW-NA montmorillonite clay (40 pounds) were added to a 16 ft. ³ ribbon blender and mixed for 15 minutes. With the ribbon blender running Cottonseed Oil (12 pounds, product of Columbus Vegetable Oils) was sprayed onto the mixture over the course of about five minutes and ribbon blending was continued for another five minutes to give a solid premix. The solid premix was fed into a Fiexomix FX- 160 mixer at the rate of 500 pounds per hour with mixed rate of 2800 RPM and blade set to 5° forward. While the solid premix was fed into the Fiexomix, a 0.25 weight percent solution of

NEUTRAGEL® DAin water was sprayed into the Fiexomix through four nozzles at a combined rate of 125 pounds per hour for liquid addition rate of 25%, The wetted powder fell from the Fiexomix by gravity into a three zone fluidized bed fed by air at approximately 250 ^C F where it was dried until the fluidized bed temperature reached 135°F at which point the fluidized powder was allowed to convey by a bucket elevator to a Sweco screener with screens of 16 mesh and 100 mesh. The resulting heterogenous solid concentrate with particle size smaller than 16 mesh and larger than 00 mesh (0.15 mm to 1 .2 mm particle size) was collected to give a heterogeneous yield stress fluid solid concentrate labeled as "16 X 100 solid concentrate."

[00180] The particle size of the solid concentrate was determined by laser light scattering using a Horiba 950 particle size analyzer. The D10 diameter for the solid concentrate

(diameter such that less than 10% of the particles by weight have diameters less than the D10 diameter) was determined to be 228 microns. The concentration of 16 X 100 solid concentrate required to give yield stress = 2 cm by the liquid height yield stress capability method was 0.86 weight percent in water with 400 ppm TDS. [00181] The viscosity measured using the immersion blender viscosity test was 6850 cps. The dissolution properties of the 16 X 100 solid concentrate sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 14. The dissolution properties of the solid concentrate were evaluated according to the large scale mixing test and the results are shown in Table 3.

[00182] Table 3. Observations for large scale mixing of 16 X 100 solid concentrate (Example 1). large number of marble size

2 0

agglomerates on fluid surface

moderate number of marble size

9 960

agglomerates on surface

much fewer marble size

1 1 4000

agglomerates on surface

no marble size agglomerates and

53 6640 small amount of millimeter sized

floes observed

15 8160 smooth and homogeneous

[00183] According to this test, 14.4 pounds of 16 X 100 solid concentrate were poured over a period of 90 seconds onto the top of 200 gallons of recirculating water with 326 ppm TDS and temperature = 8 C using horizontal return to the tank and with the pump operating at full throttle. It was observed that the viscosity plateaued to its ultimate value and there were no visible lumps 15 minutes after solid concentration addition was complete. The viscosity of the fluid as a function of time is shown in FIG. 15. Ten minutes after mixing was complete (25 minutes after solid addition), the 16 X 100 solid concentrate yield stress fluid was pumped from the tank with manifold pressure = 125. The pressure at the nozzle was 86 psi a d the pressure drop in 100 feet of 1.5 inch municipal hose was 39 psi.

[00184] What this example shows is that a particulate solid concentrate which comprises heterogeneous particles is capable to be reliably dissolved by recirculating agitation, wherein the resulting yield stress fluid is smooth and homogenous after only 15 minutes.

[00185] Example 2. The 16 X 100 solid concentrate of Example 1 was further graded using a 50 mesh size sieve to remove particles less than 0.3 mm to give a 16 X 50 solid concentrate. The particle size of the solid concentrate was determined by laser light scattering using a Horiba 950 particle size analyzer and the D10 diameter was determined to be 356 microns. The concentration required to give yield stress = 2 cm using the liquid height yield stress capability test was 0.95 weight percent (400 ppm hardness water). The viscosity measured using the immersion blender viscosity test was 5920 cps. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 16.

[00186] Example 3. The 16 X 50 solid concentrate of Example 2 was further graded to remove particles greater than about 0.5 mm to give a 35 X 50 solid concentrate. The particle size of the solid concentrate was determined by laser light scattering using a Horiba 950 particle size analyzer and the Dl 0 diameter was determined to be 280 microns. The concentration of solid concentrate required to give a liquid with yield stress = 2 cm was 0.84 weight percent (400 ppni TDS). The viscosity measured using the immersion blender viscosity test was 5200 cps. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 17.

[00187] Example 4. Cornstarch (200 pounds, product B20F available from GPC

Incorporated), NEUTRAGEL® DA sodium poly acrylic acid salt (88 pounds), POLYGEL® CK powdered cross-linked polyacrylate (17 pounds) and powdered sugar (200 pounds, product of Alimentos y Maquila, S. A., Santa Catarina, NL Mexico) were added to a 16 ft. ³ ribbon blender and mixed for 15 minutes to give a. solid premix. The solid premix was fed into a Flexomix FX- 160 mixer at the rate of 500 pounds per hour with mixed rate of 2800 RPM and blade set to 5° forward. While the solid premix was fed into the Flexomix, a 0.25 weight percent solution of NEUTRAGEL® DA in water was sprayed into the Flexomix through four nozzles at, a combined rate of 125 pounds per hour for liquid addition rate of 25%. The wetted powder fell from the Flexomix by gravity into a three zone fluidized bed fed by air at approximately 250°F where it, was dried until the fluidized bed temperature reached 135°F at which point the fluidized powder was allowed to convey by a bucket elevator to a Sweco screener with screens of 16 mesh and 100 mesh. The resulting heterogenous solid concentrate with particle size smaller than 16 mesh and larger than 100 mesh (0.15 mm to 1 .2 mm particle size) was collected to give a heterogeneous yield stress fluid solid concentrate labeled as "16 X 100 sugar solid concentrate." The concentration of 16 X 100 sugar solid concentrate required to give yield stress ^:::: 2 cm by the liquid height yield stress capability method was 5.20 weight percent in water with 240 ppm TDS. The viscosity measured using the immersion blender viscosity test was 7600 cps. The dissolution properties of the 16 X 100 solid concentrate sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 18. The dissolution properties of the solid concentrate were evaluated according to the large scale mixing test and the results are shown in Table 3. According to this test, 20.0 pounds of 16 X 100 solid concentrate were poured over a period of 110 seconds onto the top of 200 gallons of recirculating water with 240 ppm TDS and temperature = 18 ^U C using horizontal return to the tank and with the pump operating at full throttle. It was observed that the viscosity plateaued to its ultimate value 10 minutes after solid concentration addition was complete. The viscosity of the fluid as a function of time is shown in FIG. 19. Ten minutes after mixing was complete (25 minutes after solid addition), the 16 X 100 sugar solid concentrate yield stress fluid was pumped from the tank with manifold pressure = 125. The pressure at, the nozzle was 88 psi and the pressure drop in 100 feet of 1.5 inch municipal hose was 37 psi. What this example shows is that a solid concentrate for a yield stress fluid which comprises heterogeneous particles is capable to be reliably dissolved by recirculating agitation.

[00188] Example 5. The 16 X 100 sugar solid concentrate was further graded to remove particles greater than about 0.5 mm to give a 16 X 50 solid concentrate. The concentration of solid concentrate required to give yield stress = 2 cm was 1.2 weight percent (230 ppm TDS). The viscosity measured using the immersion blender viscosity test was 7840 cps. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 20

[00189] Example 6: The premix of Example 1 was fed into a Pharmapaktor compactor (product of Hosokawa-Bepex, Leingarten, Germany) to produce flakes that were ground in a Rietz® RD Series Disintegrator and then screened to give particulates greater than 100 mesh size and smaller than 16 mesh size, labeled "compacted 16 x 100 solid concentrate." The concentration of compacted 16 X 100 sugar solid concentrate required to give yield stress ^::: 2 cm by the liquid height yield stress capability method was 0.85 weight percent in water with 370 ppm TDS, The viscosity measured using the immersion blender viscosity test was 7840 cps. The dissolution properties of the 16 X 100 solid concentrate sample were evaluated according to the recirculating agitation mixing test described above. The plot of viscosity vs mixing time for each of three runs is shown in FIG. 21 . [00190] Example 7. The compacted 16 X 100 solid concentrate was further graded to remove particles greater than about 0.5 mm to give a 16 X 50 solid concentrate. The concentration of solid concentrate required to give yield stress = 2 cm was 0.87 weight percent (380 ppm TDS). The viscosity measured using the immersion blender viscosity test was 8240 cps. The plot of viscosity vs mixing time for each of three runs is shown in FIG, 22.

{00191 ] Example 8. Ashland Aqualon CMC 7H4 sodium carboxy methyl cellulose (50 g), C and H Powdered Sugar (50 g) and GPC B20F corn starch (50 g) were placed in a Presto Model 0290003 Household Food Processor. While processing, 24.9 g of water was added dropwise. The process was repeated two more times. The resulting coarse, clumpy solid was dried for 3 hours at 80 C screened to collect the fraction with particle size between 14 and 140 mesh. The concentration of the 14 x 140 solid concentrate solid concentrate required to give yield stress = 2 cm was 3.00 weight percent (240 ppm TDS). The viscosity measured using the immersion blender viscosity test was 7120 cps. The dissolution properties were determined using the recirculating agitation mix test. The plot of viscosity vs mixing time for one run is shown in FIG. 23.

[00192] Example 9. Vanzan Xanthan Gum (50 g), C and H Powdered Sugar (50 g) and GPC B20F corn starch (50 g) were placed in a Presto Model 0290003 Household Food Processor. While processing, 30 g of water was added dropwise. The process was repeated two more times. The resulting coarse, clumpy solid was dried for 3 hours at 80 C screened to collect the fraction with particle size between 14 and 140 mesh. The concentration of the 14 x 140 solid concentrate solid concentrate required to give yield stress = 2 cm was 3.00 weight, percent (240 ppm TDS). The viscosity measured using the immersion blender viscosity test was 7120 cps. The dissolution properties were determined using the recirculating agitation mix test. The plot of viscosity vs mixing time for one run is shown in FIG . 24. [00193] Example 10. Ticagel onjac High Viscosity guar gum (50 g), C and H Powdered Sugar (50 g) and GPC B20F corn starch (50 g) were placed in a Presto Model 0290003 Household Food Processor. While processing, 20 g of water was added dropwise. The process was repeated two more times. The resulting coarse, clumpy solid was dried for 3 hours at 80 C; and screened to collect the fraction with particle size between 14 and 140 mesh. The concentration of the 14 x 140 solid concentrate solid concentrate required to give yield stress = 2 cm was 3.00 weight percent (240 ppm TDS). The viscosity measured using the immersion blender viscosity test was 7120 cps. The dissolution properties were determined using the recirculating agitation mix test. The plot of viscosity vs mixing time for one run is shown in FIG, 25.

100194] A summary of the results of solid concentrate mix tests are shown in Table 4. What these results show is that solid concentrates for yield stress fluids comprising homogeneous particles of water soluble polymeric thickeners including mixtures with homogeneous particles of viscously inert materials are not capable to be dispersed in water using recirculating agitation mixing to give useful yield stress fluids. Inventive heterogenous particulate solid concentrates are capable to be dispersed in water to give useful yield stress fluids without formation of large coalesced masses of material. Preferred particulate solid concentrates have reduced amounts of fine particles. Although solid concentrates for yield stress fluids comprising homogeneous particles of water insoluble, highly water swellable polymer (WIHWS) particles may be capable to be dispersed in water using recirculating agitation mixing to give yield stress fluids without of the formation of coalesced masses, the weight percent yield stress polymer required to give useful levels of yield stress is greater than that used with water soluble polymeric thickeners.

00195] Table 4: Summary of results for mixing solid concentrates with water using recirculating agitation