Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2003-01-30
2004-10-05
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S729000, C106S730000, C106S802000, C106S804000, C106S815000, C106S819000, C106S823000
Reexamination Certificate
active
06800129
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to enhancing processing of cement from clinker, and more particularly to a liquid-dispensable, high solids-loaded cement additive composition comprising at least one salt and optionally an amine, glycol, and/or carbohydrate, and to processes for making the same.
BACKGROUND OF THE INVENTION
Cement additives are known for enhancing the processing of cement from the grinding of clinker, gypsum, and fillers such as limestone, granulated blast furnace slag, and other pozzolans.
Cement additives comprising salts are also known. Such additives typically comprise a calcium chloride salt or sodium chloride salt, and optionally an amine and/or a carbohydrate. Such additives, usually in the form of aqueous solutions, are intended to enhance properties of cement such as strength and set time. The maximum amount of active solids in these aqueous solutions is limited by the solubility of the least water-soluble component, which is usually the chloride salt, in the water component. Salt-containing additives, which are commercially available from Grace Construction Products, Cambridge, Massachusetts, under the tradename TDA®, typically have total solids contents of 30-40% dry weight solids.
If the concentration of a given salt exceeds its solubility limit, then the salt will precipitate out of the aqueous solution and render the cement additive product difficult to use and dispense in the cement grinding operation. This is because the precipitation will clog the dispensing system and form solid masses in storage tanks. The cement additive then becomes a mixed-phase material, because one or more of its components, due to precipitation, will no longer be in solution while other components may remain in solution. The result is that the proportions of the components within the cement additive product will likely be less than ideal for the intended application, since the precipitated components will not be pumped or dispensed into the cement clinker grinding operation as intended.
Thus, one of the problems with using high concentration salt solutions is the risk that precipitation can occur. Any number of factors, such as a decrease in temperature, evaporation of water, or nucleating events such as contamination, can prompt a highly salt-saturated solution to precipitate. The precipitation will cause pump-dispensing problems and/or dosage miscalculations and inefficiencies. The typical dosage for these liquid products is 1500-2500 grams of cement additive product per ton of cement, clinker, and fillers. Hence, if the cement manufacturing plant (mill) were to use a cement additive product to produce 70 tons of cement per hour, then approximately one truckload (about 45,000 pounds) of the liquid cement additive product would be required on a weekly basis. Given the influence of the cement additive on the strength or set time performance characteristics of the cement, a missed shipment could mean that there will be a significant decrease in the quality of the cement being produced.
The shipment, storage, and handling of large volumes of liquid additive materials is highly inconvenient. However, the use of dry powders is not a more convenient or desirable alternative, because dry powders are difficult to dispense accurately -and they present a health concern due to the dust arising from the dry powder.
Accordingly, the present inventors believe that the use of a highly concentrated liquid additive provides great value and resolves problems discussed above. Until the present invention, however, it has not been possible to use and dose an extremely highly concentrated liquid salt-containing cement additive. Such a highly concentrated salt liquid, moreover, needs to be stable in suspension for long periods of time, resistant to temperature changes, and capable of being pumped so that it can be dispensed into the clinker cement grinding operation.
SUMMARY OF THE INVENTION
In surmounting the disadvantages of the prior art, the present invention provides a novel high-solids liquid cement additive compositions and method for making them. Exemplary liquid cement additive compositions of the invention comprise at least one salt, a liquid carrier, and a viscosity-modifying agent (VMA) that increases the amount of total active solids that can be suspended in the liquid carrier. If the liquid carrier is water, then exemplary embodiments of the invention further comprise a VMA-dispersing agent that not only disperses the VMA within the aqueous environment, but enhances the capacity of the liquid cement additive composition to load the salt and other cement additives at levels higher than would be possible by mere solubilization of the salt and other additives.
In particular, aqueous liquid carriers are used to dissolve a first portion of a particular cement additive (e.g., salt) while a second portion of the cement additive is suspended in the form of non-dissolved solid particles, through the use of the VMA and VMA-dispersant.
Thus, an exemplary liquid cement additive composition of the invention comprises: a liquid carrier for suspending a first cement additive, such as an alkali or alkaline earth metal salt, in the form of solid particles substantially uniformly throughout the liquid carrier. The salt may comprise a chloride, nitrate, nitrite, thiocyanate, borate, polyphosphonate, gluconate, or mixture thereof. Preferably, a second cement additive, which is different from the first cement additive, is contained within the liquid carrier as a solute and/or as non-dissolved solid particles. For example, the second cement additive may comprise an amine, an alkanolamine, a poly(hydroxyalkylated) polyethyleneamine, a glycol, a carbohydrate, a surfactant, or mixture thereof.
Exemplary liquid cement additive compositions have a total salt content of 50-90% by wt. based on total weight of said liquid cement additive composition, and a total solids content of 70%-100% by wt. based on total weight of said composition.
If the liquid carrier is an aqueous suspension, then it will be possible that a first portion of the alkali or alkaline earth metal salt is contained as a solute, while a second portion is in the form of non-dissolved solid particles, such that the liquid cement additive composition can contain solids in amounts that exceed the water-solubility factor for individual solids.
In preferred embodiments, a viscosity modifying agent (VMA), preferably with a dispersing agent operative to enhance the ability of the liquid carrier to suspend the solids (e.g., salt) particles, is used. In a preferred exemplary method, a VMA, such as biopolymer S-657, is mixed first with a polycarboxylate polymer, which is preferably a comb polymer having pendant oxyalkylene groups, and water, thereby forming a first suspension; and this first suspension is mixed with at least one alkali or alkaline earth metal salt to obtain a second suspension, which then may be used as a liquid cement additive composition which can be dispensed into the grinding operation whereby clinker is ground to provide cement.
As an alternative to the foregoing method wherein an aqueous suspension is employed, other exemplary methods of the invention involve a non-aqueous liquid carrier for dispersing the VMA. For example, a nonaqueous liquid carrier medium can include an amine, an alkanolamine, a poly(hydroxyalkylated) polyethyleneamine, a glycol, a surfactant, or mixture thereof is combined with the VMA to provide a first (nonaqueous) suspension; and then this first suspension is mixed with water to allow the VMA to hydrolyze and increase in viscosity prior to adding the at least one alkali or alkaline earth metal salt to obtain a second (aqueous) suspension. Exemplary compositions of the invention made by this method therefore comprise the nonaqueous liquid carrier, a VMA, and at least one alkali or alkaline earth metal salt, wherein the VMA and salt are present in the amount ranges summarized above.
As a further alternative, the VMA can first be dispersed in a dry blend with an alkali or alkaline earth
Jardine Leslie A.
Myers David F.
Ranganathan Anandakumar
Baker William L.
Leon Craig K.
W. R. Grace & Co.,-Conn.
Wood Elizabeth D.
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