Salt-free stable fluid suspension compositions and methods for their preparation

Abstract

The present invention relates to an aqueous, salt-free, stable fluid suspension composition comprising: (i) from about 0.01% to about 30% by weight of at least one cellulose ether; (ii) from about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; (iii) from about 0.01% to about 5% by weight of at least one stabilizer; (iv) from about 0.01% to about 5% by weight of at least one preservative; and v) from about 0.01% to about 70% by weight of water.

Description

[Technical Field]

[0001] The present invention relates to stable fluid suspension compositions, and in particular to aqueous, salt-free stable fluid suspension compositions comprising at least one cellulose ether and at least one insolubilizing agent. [Background technology]

[0002] Cellulose ether polymers are the most commonly used rheology modifiers in aqueous formulations. They are generally supplied in powder form and then dissolved in various aqueous systems to achieve the desired rheological profile. Processing difficulties have been encountered during the incorporation and dispersion of these cellulose ether powders into water-containing liquid formulations, and they often tend to form lumps when added to aqueous systems. When water-soluble polymer powders are added in bulk, particles at the interface between the powder and fluid phases of the aqueous system rapidly hydrate and begin to swell, causing particle clogging at the interface and slowing fluid penetration into the powder phase. This process ultimately leads to the formation of persistent, slowly dissolving gel aggregates of various sizes, adversely affecting the dissolution rate.

[0003] Many approaches have been used in the prior art to produce lump-free dissolutions of water-soluble polymers. Commonly used approaches are (a) slow addition of the water-soluble polymer powder, (b) pre-wetting the water-soluble polymer powder with a water-miscible solvent, and (c) blending the water-soluble polymer powder with other dry ingredients before application. Each of the above approaches has drawbacks. For example, approach (a) significantly slows powder application, and approaches (b) and (c) can carry over significant concentrations of additives that can adversely affect the product to which the water-soluble polymer product is added, either from an environmental compliance or performance standpoint.

[0004] Other known approaches to overcome the problem of lump formation by water-soluble polymers during solution preparation include (i) using glyoxal-retarded cellulose ethers, (ii) pre-dispersing the cellulose ether using an organic liquid, or (iii) dispersing in water heated above the coagulation point (hot-cold method). The problem with glyoxal-treated delayed cellulose ethers is that if the liquid carrier is acidic, the delay is long, while if the solution is too alkaline, the delay is not efficient enough. Pre-dispersing with organic liquids introduces the potential for VOC content, and the hot-cold method is very energy intensive and only suitable for products with a coagulation point below the boiling point of water.

[0005] The use of a fluidized polymer suspension of cellulose ether polymer powder has proven effective in providing better results and overcoming the aforementioned processing difficulties. This method also eliminates the formation of dust when introducing powdered or granular cellulose ether into aqueous product formulations, and offers additional benefits such as accurate dosing, improved measurability, and ease of handling of the powdered cellulose ether component. It also facilitates the rapid distribution of powdered cellulose ether in aqueous product formulations without the formation of lumps.

[0006] U.S. Pat. No. 4,469,627, filed by Colgate Palmolive Co., discloses a method of dispersing hydroxypropyl methylcellulose in a non-aqueous processing organic medium in which it does not swell or dissolve, and then adding the dispersion to an aqueous-containing liquid formulation in which it is readily solubilized.

[0007] US Patent No. 4,883,536 filed by Aqualon discloses a fluid polymer suspension of a cellulosic polymer using an ammonium salt having a multivalent anion.

[0008] US Pat. No. 4,283,229, filed by Hoechst AG, discloses a method for preparing stable aqueous cellulose ether suspensions containing electrolytes and the processing of such suspensions.

[0009] US Patent No. 4,883,537 filed by Aqualon discloses stable aqueous suspensions of water-soluble carboxymethyl cellulose, methods for their preparation, and their processing in various applications.

[0010] US Patent No. 6,025,311 filed by Aqualon discloses the use of aqueous fluid suspensions of polysaccharides in cosmetic, personal care and household applications.

[0011] U.S. Patent Nos. 6,576,048, 6,433,056, 5,268,466, and 5,228,909, filed by Hercules / Aqualon, are yet another list of prior art documents that specifically teach the use of cellulose ether polymers and salts in fluidized polymer suspension compositions.

[0012] To prepare a stable fluid polymer suspension composition, it is essential to limit the swelling behavior of the hydrophilic cellulose ether polymer in an aqueous medium. This can be achieved using several approaches that can effectively reduce the solvating power of the aqueous carrier. Prior art methods include the addition of inorganic salt compounds, and a wide variety of inorganic salts have been found to be useful for this purpose, including sodium chloride, potassium chloride, sodium citrate, sodium sulfate, sodium formate, potassium phosphate, calcium formate, potassium formate, sodium acetate, potassium bicarbonate, sodium bicarbonate, diammonium phosphate, ammonium sulfate, and the like. The concentration of the inorganic salt must be adjusted so that the flocculation (or cloud) point, i.e., the temperature at which the polymer precipitates from solution or gels to form a cloudy dispersion, is below room temperature. The concentration of the inorganic salt in the fluid polymer suspension must be high enough to render the hydrophilic cellulose ether polymer insoluble in saline water at the temperature at which the fluid polymer suspension will be stored and used.

[0013] However, using high concentrations of inorganic salts in fluidized polymer suspensions is highly undesirable for some specialty applications, including, but not limited to, washcoats, drilling fluids, specialty coatings, household products, and agricultural products. It may interfere with or interact with other additives, such as metal particles, in the formulation, or may result in undesirable chemical reactions with the substrate during end-user application, such as poisoning catalytic activity or other materials / fluids it may come into contact with. These inorganic salts also leave some residue on the substrate / surface to which they are coated, and are not completely removable during baking, which is highly undesirable for specialty coating applications such as washcoats.

[0014] Therefore, there is a strong need to formulate stable fluid suspension compositions of water-soluble cellulose ether polymers that do not use any inorganic salt-based insolubilizing agents, thus eliminating the opportunity for any of the aforementioned chemical interactions during the ultimate application of aqueous-based products containing the fluid suspension compositions.

[0015] The above and other objects and features of the present invention will become apparent from the following description. Summary of the Invention

[0016] A principal aspect of the present application is to provide an aqueous salt-free fluid suspension composition comprising: (i) from about 0.01% to about 30% by weight of at least one cellulose ether; (ii) from about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; (iii) from about 0.01% to about 5% by weight of at least one stabilizing agent; (iv) from about 0.01% to about 5% by weight of at least one preservative; and (v) from about 0.01% to about 70% by weight of water.

[0017] In another embodiment of the present application, the cellulose ether is selected from the group consisting of methyl hydroxypropyl cellulose (MHPC), hydroxypropyl cellulose (HPC), methyl cellulose (MC), carboxymethyl cellulose (CMC), carboxymethyl hydroxyethyl cellulose (CMHEC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), ethyl hydroxyethyl cellulose (EHEC), hydrophobically modified ethyl hydroxyethyl cellulose (HMEHEC), methyl hydroxyethyl cellulose (MHEC), and combinations thereof.

[0018] In another embodiment of the present application, methylhydroxypropylcellulose (MHPC) has a degree of polymerization (DP) value ranging from about 600 to about 2200, and hydroxypropylcellulose (HPC) has a degree of polymerization (DP) value ranging from about 600 to about 2200.

[0019] In another embodiment of the present application, the methylhydroxypropyl cellulose (MHPC) has a methoxy group content ranging from about 25% to about 35% and a propoxy group content ranging from about 5% to about 15%.

[0020] In another embodiment of the present application, the hydroxypropyl cellulose (HPC) has a molar substitution (MS) value ranging from about 3 to about 5.

[0021] In another embodiment of the present application, the monosaccharide is selected from the group consisting of glucose, dextrose, fructose, galactose, xylose, ribose, and combinations thereof; the disaccharide is selected from the group consisting of sucrose, lactose, maltose, lactulose, trehalose, and combinations thereof; and the polysaccharide is selected from the group consisting of maltodextrin, starch, amylose, amylopectin, dextran, and combinations thereof.

[0022] Another aspect of the present application discloses a method for preparing an aqueous salt-free fluid suspension composition, the method comprising: (a) adding about 0.01 wt % to about 70 wt % water to a reaction vessel and initiating stirring; (b) adding about 0.01% to about 5% by weight of at least one stabilizer to the reaction vessel of step (a); (c) adding about 0.01% to about 5% by weight of at least one preservative to the result of step (b); (d) adding about 0.01% to about 90% by weight of at least one insolubilizing agent to the result of step (c) and continuing stirring to achieve complete dissolution; and (e) adding about 0.01% to about 30% by weight of at least one cellulose ether to the result of step (d), and continuing stirring until a homogenized fluid suspension composition is obtained.

[0023] Another aspect of the present application discloses a thickened composition comprising an aqueous salt-free fluid suspension composition comprising: (i) about 0.01% to about 30% by weight of at least one cellulose ether; (ii) about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; (iii) about 0.01% to about 5% by weight of at least one stabilizer; (iv) about 0.01% to about 5% by weight of at least one preservative; and (v) about 0.01% to about 70% by weight of water. [Brief explanation of the drawings]

[0024] Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings, which are incorporated herein by reference. [Figure 1] FIG. 1 shows the dissolution behavior of MHPC-based fluidized polymer suspensions for a typical dry cellulose ether powder (Natrosol 250MR HEC) suspended in aqueous solution at pH 3 and ambient temperature. [Figure 2]FIG. 2 shows the dissolution behavior of MHPC-based fluidized polymer suspensions for a typical dry cellulose ether powder (Natrosol 250MR HEC) suspended in aqueous solution at pH 7 and ambient temperature. [Figure 3] FIG. 3 shows the dissolution behavior of MHPC-based fluidized polymer suspensions for a typical dry cellulose ether powder (Natrosol 250MR HEC) suspended in aqueous solution at pH 11 and ambient temperature. [Figure 4] FIG. 4 shows the dissolution behavior of MHPC-based fluidized polymer suspensions for a typical dry cellulose ether powder (Culminal MHEC 6000PR) suspended in aqueous solution at pH 3 and ambient temperature. [Figure 5] FIG. 5 shows the dissolution behavior of MHPC-based fluidized polymer suspensions for a typical dry cellulose ether powder (Culminal MHEC 6000PR) suspended in aqueous solution at pH 7 and ambient temperature. DETAILED DESCRIPTION OF THE INVENTION

[0025] Before explaining at least one aspect of the disclosed and / or claimed inventive concept(s) in detail, it is to be understood that the disclosed and / or claimed inventive concept(s) is / are not limited in its application to the details of construction and arrangement of components or steps or methodologies set forth in the following description or illustrated in the drawings. The disclosed and / or claimed inventive concept(s) is / are capable of other embodiments or of being practiced or carried out in several ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0026] As utilized in accordance with the present disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings:

[0027] Unless otherwise defined herein, technical terms used in connection with the disclosed and / or claimed inventive concepts shall have the meanings commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.

[0028] The singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise or unless the context to which reference is made clearly implies otherwise. The terms "comprising" and "comprises of" include more narrow claims such as "consisting essentially of" and "consisting of."

[0029] For purposes of the following detailed description, other than in any examples, or where otherwise indicated, for example, numbers expressing quantities of ingredients used in the specification and claims should be understood to be modified in all instances by the term "about." The numerical parameters set forth in the specification and appended claims are approximations that may vary depending upon the desired properties obtained in the practice of the invention.

[0030] All percentages, parts, proportions, and ratios used herein are by weight of the total composition unless otherwise specified. All weights relating to listed ingredients are based on the active level and therefore do not include solvents or by-products that may be contained in commercially available materials, unless otherwise specified.

[0031] All publications, articles, papers, patents, patent publications and other references cited herein are incorporated herein in their entirety for all purposes to the extent consistent with the disclosure of this specification.

[0032] The term "at least one" is understood to include one as well as any amount greater than one, including but not limited to 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The term "at least one" can range up to 100 or 1000 or more, depending on the term to which it is attached. Furthermore, the amount of 100 / 1000 should not be considered limiting as a lower or upper limit.

[0033] As used herein, the words "comprising" (and any of its forms), "having" (and any of its forms), "including" (and any of its forms), or "contain" (and any of its forms) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0034] The phrase "independently selected from the group consisting of" means that if a group occurs more than once in a structure, each occurrence of the group can be independently selected.

[0035] The term "inverted sugar" refers to a liquefied form of table sugar commercially produced by acidic or enzymatic hydrolysis in which the chemical bonds between the glucose and fructose molecules have been broken, making it resistant to crystallization and promoting moisture retention.

[0036] In a typical definition, "invert sugar" consists of the "active dry substance content", hereinafter referred to as the "active content", and the "sugar inversion rate", hereinafter referred to as the "inversion rate". As an example, invert sugar syrup 72.7 / 66 consists of 72.7% dry substance and 66% invert sugar, and therefore 34% sucrose.

[0037] The present disclosure relates to an aqueous, salt-free fluid suspension composition comprising: (i) from about 0.01% to about 30% by weight of at least one cellulose ether; (ii) from about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; (iii) from about 0.01% to about 5% by weight of at least one stabilizer; (iv) from about 0.01% to about 5% by weight of at least one preservative; and (v) from about 0.01% to about 70% by weight of water.

[0038] According to one embodiment, the cellulose ether of the present invention is selected from the group consisting of methylhydroxypropylcellulose (MHPC), hydroxypropylcellulose (HPC), methylcellulose (MC), carboxymethylcellulose (CMC), carboxymethylhydroxyethylcellulose (CMHEC), hydroxyethylcellulose (HEC), hydrophobically modified hydroxyethylcellulose (HMHEC), ethylhydroxyethylcellulose (EHEC), hydrophobically modified ethylhydroxyethylcellulose (HMEHEC), methylhydroxyethylcellulose (MHEC), and combinations thereof.

[0039] In another aspect of the present invention, the methylhydroxypropyl cellulose (MHPC) is contemplated to have a degree of polymerization (DP) value in the range of about 600 to about 800, or about 800 to about 1000, or about 1000 to about 1200, or about 1200 to about 1400, or about 1400 to about 1600, or about 1600 to about 1800, or about 1800 to about 2000, or about 2000 to about 2200.

[0040] In another aspect of the present invention, it is contemplated that the molar substitution (MS) of methylhydroxypropyl cellulose (MHPC) comprises a methoxy group content of about 25% to about 27%, or about 27% to about 29%, or about 29% to about 31%, or about 31% to about 33%, or about 33% to about 35%; and a propoxy group content ranging from about 5% to about 7%, or about 7% to about 9%, or about 9% to about 11%, or about 11% to about 13%, or about 13% to about 15%.

[0041] In another embodiment, the hydroxypropyl cellulose (HPC) of the present invention is contemplated to have a molar substitution (MS) value ranging from about 3 to about 3.5, or from about 3.5 to about 4, or from about 4 to about 4.5, or from about 4.5 to about 5.

[0042] According to another aspect of the present invention, the hydroxypropyl cellulose (HPC) is contemplated to have a degree of polymerization (DP) value in the range of about 600 to about 800, or about 800 to about 1000, or about 1000 to about 1200, or about 1200 to about 1400, or about 1400 to about 1600, or about 1600 to about 1800, or about 1800 to about 2000, or about 2000 to about 2200.

[0043] According to another embodiment, a suitable range of the cellulose ether of the present invention may vary from about 0.01% to about 5% by weight; or from about 5% to about 10% by weight; or from about 10% to about 15% by weight; or from about 15% to about 20% by weight; or from about 20% to about 25% by weight; or from about 25% to about 30% by weight, based on the total weight of the fluid suspension composition.

[0044] It has been discovered that the time required for hydration and dissolution of powdered cellulose ether polymers, including, but not limited to, methylhydroxypropyl cellulose (MHPC), hydroxypropyl cellulose (HPC), methylcellulose (MC), carboxymethylcellulose (CMC), carboxymethylhydroxyethyl cellulose (CMHEC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), ethylhydroxyethyl cellulose (EHEC), hydrophobically modified ethylhydroxyethyl cellulose (HMEHEC), methylhydroxyethyl cellulose (MHEC), or combinations thereof, in aqueous formulations can be significantly reduced by using the fluid suspension formulation of the present invention compared to conventional methods involving direct addition of powdered cellulose ether. The rapid dissolution behavior of the fluid suspension composition of the present invention relative to dry cellulose ether powder is highly beneficial in batch processing, significantly reducing residence time in the mixing chamber. Furthermore, the post-addition of the powdered cellulose ether additive during intermediate processing stages is readily possible without the risk of lump formation, flocculation, agglomeration, or other related processing and handling difficulties.

[0045] In another embodiment of the present invention, cellulose ether polymers containing sufficiently high polymer solids have been found to be useful in preparing fluid polymer suspensions, which can be effectively incorporated into aqueous-based compositions or used for post-addition during the preparation of inorganic / metallic slurries or pastes. Suspensions of this type generally contain at least 10% by weight, preferably 15% by weight or more, of a cellulose ether polymer selected from the group consisting of, but not limited to, methylhydroxypropylcellulose (MHPC), hydroxypropylcellulose (HPC), methylcellulose (MC), carboxymethylcellulose (CMC), carboxymethylhydroxyethylcellulose (CMHEC), hydroxyethylcellulose (HEC), hydrophobically modified hydroxyethylcellulose (HMHEC), ethylhydroxyethylcellulose (EHEC), hydrophobically modified ethylhydroxyethylcellulose (HMEHEC), methylhydroxyethylcellulose (MHEC), or combinations thereof, in an aqueous liquid carrier. The aqueous liquid carrier further contains additives dissolved or dispersed in a concentration high enough to prevent the hydrophilic cellulose ether polymer from substantially swelling or dissolving in the aqueous medium, thereby making the hydrophilic cellulose ether polymer fluid and allowing the cellulose ether polymer particles to be properly dispersed and suspended, thereby providing stability. Whenever necessary, a small amount of less than 0.5% by weight of a preservative is added to the composition to avoid microbial degradation and particle coagulation during storage.

[0046] During the preparation of a liquid suspension, it is crucial to ensure sufficient means to limit the swelling and dissolution of the hydrophilic cellulose ether polymer in the aqueous medium. This can be achieved by incorporating appropriate additives that can effectively reduce the solvating power of the aqueous carrier. A traditional approach involves the addition of an insolubilizing agent, such as an inorganic salt. A wide variety of inorganic salts have been found to be useful for this purpose, typically including, but not limited to, sodium chloride, potassium chloride, sodium citrate, sodium sulfate, sodium formate, potassium phosphate, calcium formate, potassium formate, sodium acetate, potassium bicarbonate, sodium bicarbonate, diammonium phosphate, ammonium sulfate, or combinations thereof. The concentration of the inorganic salt must be adjusted so that the flocculation (or cloudiness) point, i.e., the temperature at which the polymer precipitates from solution or gels to form a cloudy dispersion, is below room temperature. The concentration of the inorganic salt in the fluid polymer suspension must be high enough to render the polymer insoluble in saline water at the temperature at which the fluid polymer suspension will be stored and used. Furthermore, the inorganic salt concentration must be so high that swelling of the insolubilized polymer particles in the aqueous medium occurs only to a limited extent, if at all.

[0047] However, using high concentrations of inorganic salts in fluidized polymer suspensions is highly undesirable for some specialized applications, including, but not limited to, washcoats, drilling fluids, specialty coatings, household products, and agricultural products. This can interfere with or affect other additives, such as metal particles, in the formulation in end-user applications, or result in some undesirable chemical reactions with the substrate or other materials / fluids that it may come into contact with. These inorganic salts also leave some residue on the substrate that is not completely removable during firing, which is highly undesirable for applications such as washcoats. Therefore, the present invention contemplates the use of salt-free insolubilizers for the preparation of stable fluid suspension compositions that are highly suitable for the above-mentioned applications.

[0048] According to yet another embodiment, the insolubilizing agent of the present invention is selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof.

[0049] According to another embodiment, suitable monosaccharides of the present invention include, but are not limited to, glucose, dextrose, fructose, galactose, xylose, ribose, and combinations thereof; suitable disaccharides of the present invention include, but are not limited to, sucrose, lactose, maltose, lactulose, trehalose, and combinations thereof; suitable polysaccharides of the present invention include, but are not limited to, maltodextrin, starch, amylose, amylopectin, dextran, and combinations thereof.

[0050] In some embodiments, the insolubilizing agents of the present invention are in the form of a powder, liquid, or an aqueous solution thereof.

[0051] In some embodiments, the insolubilizing agent of the present invention is invert sugar, and suitable ranges of active content of invert sugar may vary from about 65% to about 70%, or from about 70% to about 75%, or from about 75% to about 80%, or from about 80% to about 85%.

[0052] In some embodiments, the insolubilizing agent of the present invention is invert sugar, and suitable ranges of conversion of invert sugar can vary from about 55% to about 60%, or from about 60% to about 65%, or from about 65% to about 70%, or from about 70% to about 75%.

[0053] According to another embodiment, a suitable range for the insolubilizer of the present invention is from about 0.01% to about 5% by weight, based on the total weight of the fluid suspension composition; or from about 5% to about 10% by weight; or from about 10% to about 15% by weight; or from about 15% to about 20% by weight; or from about 20% to about 25% by weight; or from about 25% to about 30% by weight; or from about 30% to about 35% by weight; or from about 35% to about 40% by weight or about 40% to about 45% by weight; or about 45% to about 50% by weight; or about 50% to about 55% by weight; or about 55% to about 60% by weight; or about 60% to about 65% by weight; or about 65% to about 70% by weight; or about 70% to about 75% by weight; or about 75% to about 80% by weight; or about 80% to about 85% by weight; or about 85% to about 90% by weight.

[0054] According to one embodiment, the stabilizing agent of the present invention is selected from the group consisting of xanthan gum, sodium carboxymethylcellulose, sodium alginate, bentonite clay, carrageenan, and combinations thereof.

[0055] According to another embodiment, a suitable range of the stabilizer of the present invention may vary from about 0.01% to about 0.5% by weight, or from about 0.5% to about 1% by weight, or from about 1% to about 1.5% by weight, or from about 1.5% to about 2% by weight, or from about 2% to about 2.5% by weight, or from about 2.5% to about 3% by weight, or from about 3% to about 3.5% by weight, or from about 3.5% to about 4% by weight, or from about 4% to about 4.5% by weight, or from about 4.5% to about 5% by weight, based on the total weight of the fluid suspension composition.

[0056] According to one embodiment, the preservative of the present invention is selected from the group consisting of sodium benzoate, citric acid, benzyl alcohol, propylparaben, ethylparaben, butylparaben, methylparaben, benzylparaben, isobutylparaben, phenoxyethanol, ethanol, sorbic acid, benzoic acid, methylchloroisothiazolinone, methylisothiazolinone, methyldibromoglutaronitrile, dehydroacetic acid, o-phenylphenol, 1,2-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, benzyl bromoacetate, bicyclic oxazolidine, 4,4-dimethyloxazolidine, and combinations thereof.

[0057] According to another embodiment, a suitable range of the preservative of the present invention may vary from about 0.01% to about 0.5% by weight, or from about 0.5% to about 1% by weight, or from about 1% to about 1.5% by weight, or from about 1.5% to about 2% by weight, or from about 2% to about 2.5% by weight, or from about 2.5% to about 3% by weight, or from about 3% to about 3.5% by weight, or from about 3.5% to about 4% by weight, or from about 4% to about 4.5% by weight, or from about 4.5% to about 5% by weight, based on the total weight of the fluid suspension composition.

[0058] According to one embodiment, the present application discloses a method for preparing an aqueous salt-free fluid suspension composition, the method comprising: (a) adding about 0.01 wt % to about 70 wt % water to a reaction vessel and initiating stirring; (b) adding about 0.01% to about 5% by weight of at least one stabilizer to the reaction vessel of step (a); (c) adding about 0.01% to about 5% by weight of at least one preservative to the result of step (b); (d) adding about 0.01% to about 90% by weight of at least one insolubilizing agent to the result of step (c) and continuing stirring to achieve complete dissolution; and (e) adding about 0.01% to about 30% by weight of at least one cellulose ether to the result of step (d), and continuing stirring until a homogenized fluid suspension composition is obtained.

[0059] The resulting polymer suspension compositions of the present invention are typically flowable, pourable, and pumpable. Generally, the suspensions have a viscosity of less than 20,000 mPas one day after preparation, as measured on a Brookfield Model RVT viscometer at 20 rpm / 20°C. For ease of pumping and mixing, preferred products having a total polymer solids content of 15% or greater typically have a suspension viscosity of 20,000 mPas or less.

[0060] In another embodiment, the fluid suspension composition of the present invention is further formulated into aqueous systems, such as for washcoats, mineral, inorganic, or metal powder slurries, etc. The fluid suspension is significantly diluted, and the additive concentration is low enough to facilitate the dispersion and dissolution of the cellulose ether polymer. In fact, because the polymer particles in the suspension are pre-wetted and often slightly swollen, the suspension can disperse and dissolve in aqueous media at a much higher rate than dry polymers. In other words, the present invention allows for short mixing cycles of approximately 5 to 10 minutes, rather than the 1 to 3 hour mixing period required with conventional cellulose ether polymer powder components. This significantly increases the productivity of producing aqueous systems containing (i) the aqueous, salt-free fluid suspension composition of the present invention and (ii) other additives, such as, but not limited to, precious metal particles, inorganic oxides, and acids.

[0061] According to another embodiment, the fluid suspension compositions of the present invention are used to prepare aqueous-based formulations that find use in products including, but not limited to, washcoats, drilling fluids, concrete, joint compounds, mortars, adhesives, cosmetics, personal care products, household products, agricultural products, paints, and paper coatings.

[0062] According to one embodiment, the present application discloses a thickened composition comprising an aqueous salt-free fluid suspension composition comprising: (i) about 0.01% to about 30% by weight of at least one cellulose ether; (ii) about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; (iii) about 0.01% to about 5% by weight of at least one stabilizer; (iv) about 0.01% to about 5% by weight of at least one preservative; and (v) about 0.01% to about 70% by weight of water.

[0063] The thickened compositions of the present application are used in washcoats, drilling fluids, concrete, joint compounds, mortars, adhesives, cosmetics, personal care products, household products, agricultural products, paints, and paper coatings.

[0064] Another embodiment of the present invention provides a method for the continuous preparation of aqueous slurry compositions, which may include, but are not limited to, washcoats, drilling fluids, concrete, joint compounds, mortars, adhesives, cosmetics, personal care products, household products, agricultural products, paints, or paper coatings, involving the use of an aqueous, salt-free, fluid suspension composition comprising: (i) from about 0.01% to about 30% by weight of at least one cellulose ether; (ii) from about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; (iii) from about 0.01% to about 5% by weight of at least one stabilizer; (iv) from about 0.01% to about 5% by weight of at least one preservative; and (v) from about 0.01% to about 70% by weight of water. The method for producing the aqueous slurry composition further comprises the addition of a component comprising a precious metal, an acid, an inorganic oxide, or a combination thereof. Use of the aqueous, salt-free fluid suspension compositions of the present invention further provides rapid viscosity control and ease of handling during the continuous preparation of aqueous slurry compositions.

[0065] Another embodiment of the present invention further provides a washcoat formulation for applying a catalytic coating to a catalyst support. The support is typically in the form of a honeycomb with passages for gas flow. Honeycombs are used in automotive catalytic converters and catalytic incinerators to burn pollutants in an air stream. A typical washcoat also contains alumina and catalytic metal, so that the catalytic coating is applied in a single step. The washcoat is particularly suitable for catalytic converters for automobiles or stationery.

[0066] The washcoat has a high solids content, a tailored rheological profile, and dries to a smooth, crack-free, adherent coating. The washcoat contains a catalytic metal, such as platinum, palladium, rhodium, or other catalytically active component. The catalytic metal is dispersed on alumina, which results in high dispersion of the metal and high catalytic activity.

[0067] Certain aspects of the present application are further illustrated in detail by the following examples, which are provided herein to illustrate, but not to limit, the present application. [Example] Example 1: Preparation of a fluid polymer suspension composition containing inorganic salts [Table 1] A fluid suspension composition according to the above formula was prepared by mixing the ingredients as follows to obtain a 100 g sample: 1.64.64 g of purified water was placed in a reaction vessel equipped with a stirrer. 2. 0.16g of xanthan gum was then added with constant stirring until completely dissolved. 3. 0.2g of Proxel GXL was added to the above mixture and mixed thoroughly. 4. Then 15g of ammonium sulfate was added and stirred thoroughly to obtain a homogeneous mixture. 5. Finally, 20 g of Natrosol 250 MR was dispersed in the above mixture and stirred thoroughly to obtain a homogeneous mixture.

[0068] A fluid suspension composition of Natrosol 250 MR (HEC) was prepared according to the above method and its stability in aqueous systems such as washcoats was evaluated. Washcoat samples were prepared using the fluid suspension composition of Example 1, and viscosity development over time was examined using an Anton Paar MCR102 Rheometer at various time intervals, including (i) immediately after preparation, (ii) after 3 days, and (iii) after 5 days. It was observed that the fluid suspension composition of Example 1 exhibited unpredictable thickening behavior when interacting with washcoat components. Due to the extremely low pH and catalyst components, the HEC (Natrosol 250 MR) in the above formulation reacted in an unpredictable manner and failed to rapidly provide stable rheological values.

[0069] Example 2: Reduction / removal of inorganic salts from fluid polymer suspensions Various fluid suspension compositions of high purity, non-glyoxalated, finely ground grade Culminal MHPC 814 (MHPC) were prepared according to the following method, in which the amount of ammonium sulfate salt was significantly reduced to 5 wt % by incorporating various sugars according to Table 1.

[0070] Fluid suspension compositions according to Examples 2(a)-2(k) of Table 1 were prepared by mixing the ingredients in the following order to obtain 100 g samples. 1. 37.40 g to 54.80 g of purified water shown in Table 1 was placed in a reaction vessel equipped with a stirrer. 2. 0.1 g of xanthan gum was then added with constant stirring until completely dissolved. 3. 0.1g Proxel GXL was added to the above mixture and mixed thoroughly. 4.5 g of ammonium sulfate was added and stirred thoroughly to obtain a homogeneous mixture. 5.20 g to 37.4 g of an insolubilizer (sugar or invert sugar) according to Table 1 was added to the above mixture and dissolved thoroughly. 6. Finally, 20 g of Culminal MHPC 814 was dispersed in the above mixture and stirred thoroughly to obtain a homogeneous mixture.

[0071] After preparation, the flow and foaming behavior of the slurries was evaluated. The goal was to produce a free-flowing liquid suspension. The prepared suspensions were each collected in 100 ml graduated cylinders and sealed. The amount of syneresis for each sample was observed and recorded over a two-month period. [Table 2]

[0072] Results and Observations: Example 2(a): Difficult to dissolve desired amount and exhibited problems due to crystallization. Example 2(b): Unable to dissolve desired amount in water. Example 2(c): Unable to dissolve desired amount in water. Example 2(d): Good solubility, but not good enough by itself to completely reduce the salt content. Example 2(e): Good solubility, but not good enough by itself to completely reduce the salt content. Example 2(f): Very thick and had to be diluted 50:50 with water. Example 2(g): Thinner than 45°, so handling is good, but still too thick. Example 2(h): Based on product data, it is clearly too thick to handle. Example 2(i): Based on product data, clearly too thick to handle. Example 2(j): Thinner than the invert sugar syrup of Example 2(i). Example 2(k): This sugar solution was the most dilute, allowing us to directly disperse Carminal MHPC 814.

[0073] Example 3: Two-component fluid suspension formulation [Table 3]

[0074] A fluid suspension composition according to the above formula was prepared by mixing the ingredients as follows to obtain a 100 g sample: 1.80 g of invert sugar 72.7 / 66 was placed in a reaction vessel equipped with a stirrer. 2. 20 g of Culminal MHPC 814 was then added with vigorous stirring until a smooth suspension was obtained.

[0075] A two-component fluid suspension composition was prepared and tested for stability. Three 100 ml plastic beakers with screw caps were filled with 100 ml of the final FPS formulation. One beaker was stored in the refrigerator, one beaker at room temperature, and one beaker in a heating chamber at 40°C. All samples were stored under the above conditions for one month and periodically checked for separation or other changes. The compositions were found to be stable for more than one month without any decomposition or mold growth, although the compositions did exhibit slight syneresis during storage.

[0076] Example 4: Preparation of a stable fluid suspension composition [Table 4]

[0077] A fluid suspension composition according to the above formula was prepared by mixing the ingredients as follows to obtain a 100 g sample: 1.19.7 g of purified water was charged to a reaction vessel equipped with an impeller agitator. 2. 0.1 g of xanthan gum was then added to the mixture and allowed to dissolve completely. 3. 0.1 g of sodium benzoate was added and dissolved, and then converted to benzoic acid in an acidic environment. 4. 0.1 g of citric acid was then added to achieve a pH of 5. 5. Then 60g of invert sugar 72.7 / 66 was added and dissolved thoroughly. 6. Finally, 20g of Culminal MHPC 814 powder was slowly incorporated into the mixture to avoid air entrapment.

[0078] Liquid suspension compositions were prepared and tested for stability. Three 100 ml plastic beakers with screw caps were filled with 100 ml of the final FPS formulation. One beaker was stored in the refrigerator, one beaker at room temperature, and one in a heating chamber at 40°C. All samples were stored under the above conditions for one month and periodically checked for separation or other changes. None of the samples showed any deviations during the one-month period. The compositions exhibited better stability during storage.

[0079] Example 5: Tests with other cellulose ethers

[0080] Preparation Method: The fluid suspension compositions of Examples 5(a) to 5(c) according to Table 2 were prepared by mixing the ingredients as follows to obtain 100 g samples. 1.19.7 g of purified water was charged to a reaction vessel equipped with an impeller agitator. 2. 0.1 g of xanthan gum was then added to the mixture and allowed to dissolve completely. 3. 0.1 g of sodium benzoate was added and dissolved, and then converted to benzoic acid in an acidic environment. 4. Then 0.1 g of citric acid was added to bring the pH to 5. 5. 60g to 65g of invert sugar 72.7 / 66 according to Table 2 was added and dissolved thoroughly. 6. Finally, 15 g to 20 g of cellulose ether powder according to Table 2 (e.g., Benecel E10M, Culminal MHPC 724, or Klucel HXF) was slowly incorporated into the mixture to avoid air entrapment.

[0081] Fluid suspension compositions of Benecel E10M, Culminal MHPC 724, and Klucel HXF were obtained according to the method described above. After preparation, fluidized polymer suspension composition samples were examined for flow behavior by pouring them from the preparation vessel into a tilted cylinder. Visual inspection provided insight into homogeneity and viscosity. The graduated cylinder was sealed with adhesive foil and left for one week to check for separation and stability. [Table 5] Results and Observations: Example 5(a): Works well and is stable, but a little thicker than Example 4 Example 5(b): Successful and stable, thicker than Example 4 and thinner than Example 5(a) Example 5(c): Works well and is stable, but a little thicker than Example 4

[0082] Example 6: Dissolution Behavior The dissolution behavior of typical dry cellulose ether powders, such as (i) Natrosol 250MR HEC and (ii) Culminal MHEC 6000PR, suspended in MHPC-based fluidized polymer suspensions and aqueous solutions, was measured at ambient temperature and various pH levels (pH 3, pH 7, and pH 11). Torque development over time was measured using a Brookfield R / S+ rheometer using a V80 / 40 vane spindle at 400 rpm. All viscosity values were normalized to the percentage scale to allow for direct comparison of viscosity development.

[0083] Figures 1-3 show the dissolution behavior of MHPC-based fluidized polymer suspensions, showing the dissolution times measured at various pH levels, including pH 3, pH 7, and pH 11, compared to a typical dry cellulose ether powder (Natrosol 250MR HEC) suspended in aqueous solution at ambient temperature. The magnitude of the increase in dissolution rate with the fluid polymer suspension composition is significant. The typical fluid polymer suspension composition takes less than 5 minutes to develop more than 95% of its final solution viscosity, whereas a conventional dry polymer powder takes more than 40 minutes under the same conditions.

[0084] Similarly, Figures 4-5 show the dissolution behavior as a measure of dissolution time measured at various pH levels, including pH 3 and pH 7, for MHPC-based fluidized polymer suspensions of a typical dry cellulose ether powder (Culminal MHEC 6000PR) suspended in aqueous solution at room temperature. Again, the magnitude of the increase in dissolution rate with the fluid polymer suspension composition is striking. The typical fluid polymer suspension composition requires less than 5 minutes to develop 95% or more of its final solution viscosity, whereas conventional dry polymer powders require over 100 minutes under the same conditions.

[0085] Thus, two common problems of dusting and particle agglomeration in conventional solution preparations of dry polymer powder additives are completely eliminated by use of the fluid polymer suspension compositions of the present invention.

Claims

1. i) about 0.01% to about 30% by weight of at least one cellulose ether; ii) from about 0.01% to about 90% by weight of at least one insolubilizing agent selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof; iii) about 0.01% to about 5% by weight of at least one stabilizer; iv) about 0.01% to about 5% by weight of at least one preservative; and v) An aqueous salt-free fluid suspension composition comprising from about 0.01% to about 70% by weight of water.

2. 2. The composition of claim 1, wherein the cellulose ether is selected from the group consisting of methyl hydroxypropyl cellulose (MHPC), hydroxypropyl cellulose (HPC), methyl cellulose (MC), carboxymethyl cellulose (CMC), carboxymethyl hydroxyethyl cellulose (CMHEC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), ethyl hydroxyethyl cellulose (EHEC), hydrophobically modified ethyl hydroxyethyl cellulose (HMEHEC), methyl hydroxyethyl cellulose (MHEC), and combinations thereof.

3. 2. The composition of claim 1, wherein the cellulose ether is selected from the group consisting of methylhydroxypropylcellulose (MHPC), hydroxypropylcellulose (HPC), and combinations thereof.

4. 4. The composition of claim 3, wherein the methylhydroxypropyl cellulose (MHPC) has a degree of polymerization (DP) value ranging from about 600 to about 2200.

5. 4. The composition of claim 3, wherein the hydroxypropyl cellulose (HPC) has a degree of polymerization (DP) value ranging from about 600 to about 2200.

6. 4. The composition of claim 3, wherein the methylhydroxypropyl cellulose (MHPC) has a methoxy group content ranging from about 25% to about 35% and a propoxy group content ranging from about 5% to about 15%.

7. 4. The composition of claim 3, wherein the hydroxypropyl cellulose (HPC) has a molar substitution (MS) value ranging from about 3 to about 5.

8. 10. The composition of claim 1, wherein the amount of the cellulose ether ranges from about 1% to about 25% by weight.

9. 10. The composition of claim 1, wherein the insolubilizing agent is in the form of a powder, liquid, or aqueous solution.

10. 10. The composition of claim 1, wherein the monosaccharide is selected from the group consisting of glucose, dextrose, fructose, galactose, xylose, ribose, and combinations thereof.

11. 2. The composition of claim 1, wherein the disaccharide is selected from the group consisting of sucrose, lactose, maltose, lactulose, trehalose, and combinations thereof.

12. 10. The composition of claim 1, wherein the polysaccharide is selected from the group consisting of maltodextrin, starch, amylose, amylopectin, dextran, and combinations thereof.

13. 10. The composition of claim 1, wherein the invert sugar has an active content of about 65% to about 85% and an inversion rate of about 55% to about 75%.

14. 10. The composition of claim 1, wherein the invert sugar has an active content of about 70% to about 80% and an inversion rate of about 60% to about 70%.

15. 10. The composition of claim 1, wherein the amount of the insolubilizing agent ranges from about 40% to about 85% by weight.

16. 10. The composition of claim 1, wherein the stabilizer is selected from the group consisting of xanthan gum, sodium carboxymethylcellulose, sodium alginate, bentonite clay, carrageenan, and combinations thereof.

17. 10. The composition of claim 1, wherein the stabilizer is xanthan gum.

18. The composition of claim 1, wherein the amount of the stabilizer ranges from about 0.01% to about 2% by weight.

19. 2. The composition of claim 1, wherein the preservative is selected from the group consisting of sodium benzoate, citric acid, benzyl alcohol, propylparaben, ethylparaben, butylparaben, methylparaben, benzylparaben, isobutylparaben, phenoxyethanol, ethanol, sorbic acid, benzoic acid, methylchloroisothiazolinone, methylisothiazolinone, methyldibromoglutaronitrile, dehydroacetic acid, o-phenylphenol, 1,2-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, benzyl bromoacetate, bicyclic oxazolidine, 4,4-dimethyloxazolidine, and combinations thereof.

20. 10. The composition of claim 1, wherein the preservative is selected from the group consisting of sodium benzoate, citric acid, and combinations thereof.

21. 10. The composition of claim 1, wherein the amount of the preservative ranges from about 0.01% to about 2% by weight.

22. 10. The composition of claim 1 used in washcoats, drilling fluids, concrete, joint compounds, mortars, adhesives, cosmetics, personal care products, household products, agricultural products, paints, and paper coatings.

23. 1. A method for preparing an aqueous salt-free fluid suspension composition, comprising: (a) adding about 0.01% to about 70% by weight of water to a reaction vessel and initiating agitation; (b) adding about 0.01% to about 5% by weight of at least one stabilizer to the reaction vessel of step (a); (c) adding about 0.01% to about 5% by weight of at least one preservative to the result of step (b); (d) adding about 0.01% to about 90% by weight of at least one insolubilizing agent to the result of step (c) and continuing stirring to achieve complete dissolution; and (e) adding about 0.01% to about 30% by weight of at least one cellulose ether to the result of step (d) and continuing stirring until a homogenized fluid suspension composition is obtained.

24. 24. The method of claim 23, wherein the preservative or preservative system is selected from the group consisting of sodium benzoate, citric acid, benzyl alcohol, propylparaben, ethylparaben, butylparaben, methylparaben, benzylparaben, isobutylparaben, phenoxyethanol, ethanol, sorbic acid, benzoic acid, methylchloroisothiazolinone, methylisothiazolinone, methyldibromoglutaronitrile, dehydroacetic acid, o-phenylphenol, 1,2-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, benzyl bromoacetate, bicyclic oxazolidine, 4,4-dimethyloxazolidine, and combinations thereof.

25. 24. The method of claim 23, wherein the stabilizer is selected from the group consisting of xanthan gum, sodium carboxymethylcellulose, sodium alginate, bentonite clay, carrageenan, and combinations thereof.

26. 24. The method of claim 23, wherein the insolubilizing agent is selected from the group consisting of monosaccharides, disaccharides, polysaccharides, invert sugars, and combinations thereof.

27. 24. The method of claim 23, wherein the cellulose ether is selected from the group consisting of methyl hydroxypropyl cellulose (MHPC), hydroxypropyl cellulose (HPC), methyl cellulose (MC), carboxymethyl cellulose (CMC), carboxymethyl hydroxyethyl cellulose (CMHEC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), ethyl hydroxyethyl cellulose (EHEC), hydrophobically modified ethyl hydroxyethyl cellulose (HMEHEC), methyl hydroxyethyl cellulose (MHEC), and combinations thereof.

28. A thickened composition comprising the aqueous, salt-free fluid suspension composition of claim 1.

29. 30. The thickening composition of claim 28, used in washcoats, drilling fluids, concrete, joint compounds, mortars, adhesives, cosmetics, personal care products, household products, agricultural products, paints, and paper coatings.

30. 30. The thickening composition of claim 29, used in a range of about 1% to about 30% by weight.

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