SELF-INDICATING NEUTRALIZING COMPOSITIONS

Abstract: A unitized, self-indicating, neutralizing composition comprises a neutralizing agent, a binding agent, and a pH indicator. The composition may optionally further include a disintegrant. The composition is convenient to use and is especially useful in the neutralization of wash water from cementitious compositions.

Description: SELF-INDICATING NEUTRALIZING COMPOSITIONS Background of Invention Wash water that has been used to clean equipment that has been exposed to substances which are highly alkaline or acidic, for example, water used to wash cement mixing equipment, will often not be at a neutral pH at the end of washing. The wash water will thus require neutralization before disposal, to comply with environmental regulations, This is usually achieved by addition of a neutralizing agent, and the achievement of an appropriate pH is verified by testing. This can be time-consuming. In addition, in the case of cement mixing equipment, such as mixer trucks, stationary mixers and chutes at job sites, the quantity of residual material is variable, and this makes estimating the amount of neutralizing agent difficult. This means that multiple additions of neutralizing agent and subsequent testing are often needed. What is needed in the art is a neutralizing agent that can indicate when the solution is neutralized without the need for measuring pH. Summary of Invention The present invention provides a unitized, self-indicating, neutralizing composition comprising a neutralizing agent, a binding agent, and a pH indicator. The present invention also provides a method of neutralizing a solution to about a neutral pH comprising adding a sufficient amount of a unitized, self-indicating, neutralizing composition comprising a neutralizing agent, a binding agent, and a pH indicator to the solution, until the solution has about a neutral pH as indicated by the pH indicator, wherein the neutralizing composition dissolves into the solution to effect neutralization. Brief Description of Drawings Figure 1 illustrates one embodiment of the present invention wherein the self-indicating neutralizing composition is severable into smaller units. Detailed Description The composition is unitized to provide ease of use for adding the composition to the solution. By "unitized" it is meant that the composition is solid and in a single unit of suitable size, as opposed to, say, a powder. Such units are generally prepared by compaction. Any known method of compacting powdered or flake solid materials may be used to produce the self- indicating neutralizing compositions. Examples of such methods include extrusion moulding of the self-indicating neutralizing composition, pressing, stamping or tahletting, and moulding, such as by melting and pouring into a shaped mould. The composition can be unitized into any desired shape, preferably a tablet or puck shape. There are cases where compaction is unnecessary; these will be further discussed hereinunder. The result of any such compaction should be that the composition has sufficient strength to allow handling, but is also sufficiently friable to break down under conditions of use and allow the composition to perform its function. The composition is added to a solution that is not at a neutral pH to bring it to a pH that is about neutral, that is, between about 5.5 and about 8.5. The neutralizing agent may be an acid or a base. Preferably, the neutralizing agent comprises an organic chemical. Examples of suitable neutralizing agents include, but are not limited to, citric acid, acetic acid, phosphoric acid, succinic acid, phthalic acid, uric acid, stearic acid, lauric acid, palmitic acid, oleic acid, oxalic acid, tartaric acid, malic acid, lactic acid, carbonic acid, boric acid, sulfuric acid, nitric acid, hydrochloric acid, benzoic acid, monosodium citrate, monopotassium citrate, KHSO4, NaHSO 4 , KH 2 PO , and mixtures thereof. Generally, the neutralizing agent is present to the extent of from 45% to 85% based on the weight of the composition. Preferably, the neutralizing agent is present to the extent of from 65% to 75% based on the weight of the composition. Examples of the binding agent include, but are not limited to, polyethylene glycol, polyoxypropylene glycol adducts, polyoxyethylenestearate, polyvinylbutyral, polyvinyl alcohols, paraffin, polyvinylacetate, polyvinyl methyl ether-nialeic anhydride PNM/MA), cellulose, talc, clays, silicates, silica fume, fumed silica such as "Aerosil" (trade mark), precipitated silica gel, organic pigments, synthetic resins, and mixtures thereof. Generally, the binding agent is present from 5% to 25% based on the weight of the composition. Preferably, the binding agent is present from 6% to 15% based on the weight of the composition. Examples of the pH indicator include, but are not limited to, phenol red, phenolphthalein, cresol red; metanil yellow; m-nitrophenol; curcurmin; alizarin; alizarin yellow R; alizarin blue; methyl orange; litmus; Congo red; bromthymol blue; chlorphenol red; cresol purple; brilliant diazol yellow; salts of phenolphthalein; neutral red; acid R phosphine, Cleves acid; coumaric acid; 3,6-dioxyphthalic dinitrile; magnesium 8-hycIroxyqumolinate; β- methylumbelliferone; l-naphthol-4-sulfonic acid; orcinaurine; patent phosphine; thioflavine; umbelliferone; and mixtures thereof. Preferably, the salts of phenolphthalein are selected from the group consisting of sodium, disodium, potassium, and mixtures thereof. Generally, the pH indicator is present from 0.001% to 0.8% based on the weight of the composition. Preferably, the pH indicator is present from 0.1% to 0.8% based on the weight of the composition. More preferably, the pH indicator is present from 0J % to 0.4% based on the weight of the composition. Additionally, the composition may include a disintegrant to aid in dissolving the composition in the solution. Preferably, the disintegrant is an effervescing disintegrant, activated by contact with the aqueous solution to be neufralized. Examples of suitable disintegrants include, but are not limited to, lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, caesium carbonate, caesium bicarbonate, ammonium carbonate, ammonium bicarbonate, lithium phosphate, sodium phosphate, potassium phosphate, caesium phosphate, ammonium phosphate, borax, magnesium carbonate with citric acid, potassium bitartrate, potassium biphthalate, potassium oxalate, potassium hydrogen phthalate, alkaline perborates, perchlorates, permaganates, chlorates, potassium tetraborate, sodium carbonate peroxide, tartaric acid, Rochelle salt (potassium-sodium tartrate), citric acid, potassium hydrogen tartrate, R carbonate peroxides, hyperoxides, materials that liberate nitrogen, and mixtures thereof, wherein R=C n H 2n +ι, or CβBUX, wherein n is an integer from 1 to 24, and X is selected from the group consisting of COOH, polyethylene oxide, alkyl sulfonate, and mixtures thereof. Preferably, n is an integer from 8 to 18. Suitable examples of materials that liberate nitrogen include, but are not limited to, hydrazine, compounds containing an azo group, and azides. Generally, the disintegrant is present to the extent of from 1% to 30% based on the weight of the composition. Preferably, the disintegrant is present to the extent of from 3% to 21% based on the weight of the composition. The composition can also include other additives for manufacturing as needed. Examples of the other additives include, but are not limited to, dyes, pigments, dyeing assistants, colorants, tannins, colloidal material, toners, clays, talcs, barytes, whitening agents, mould release agents, lubricants, and mixtures thereof. Generally, the quantity of additives present is up to 70% based on the weight of the composition. Preferably, the additives are present to the extent of up to 12% based on the weight of the composition. When the unitized composition is to be formed by compaction, it is preferable to add inert fillers to the self-indicating neutralizing composition. This helps render individual units structurally stable for physical handling and storage, and/or facilitate the rapid breakdown by dissolution and/or fragmentation of the unit when added to an aqueous solution. These characteristics are obtained by balancing the addition percentage of inert filler and the compacting pressure, to provide a self-indicating neutralizing composition unit of desired physical integrity and stability, and of desired solubility, friability or fragmentability. The provision of a suitable structural stability is within the routine skill of the art. Fillers may be present in the self-indicating neutralizing composition in an amount of up to 50% by the weight of the composition, if the sole function of the filler is as a filler. However, if the filler performs another function in the composition in addition to acting as a filler, it can be present in an amount of up to 95% based on the weight of the composition. Preferably, the amount of filler in the composition is from 5% to 15% based on the weight of the composition. Examples of suitable fillers include silica sand, silica fume, other natural or synthetic silica- based materials, "Micro-Cell" (trade mark) E silica (Celite Corp.), silicates, calcium alurriinosilicate, aluminosilicates, clays, alumina, ALUNDUM (trade mark) aluminosilicates (Norton), zeolites, ceramic spheres, fly ash, limestone powder, and finely divided or powdered plastic. Preferably, the neutralizing agent, the pH indicator, the binder, the disintegrant, and any other additive in the composition are solids. If it is desired to use liquid components, these may be processed into solid compacted units by adsorbing them on to carriers, which are advantageously the inert fillers hereinabove described. The carriers are contacted by the liquid components, and preferably at least partially dried, such as by air drying, prior to compaction. For water-alcohol-borne materials, the carriers are fully dried to prevent reaction with other components when compacted. Carriers are preferably present in the composition from 5% to 25% by weight of the composition. In yet another embodiment of the present invention, soluble solid self-indicating neutralizing composition materials may be dissolved in a suitable liquid solvent, such as water, and the resulting solution impregnated or adsorbed on to carriers by contacting the carrier with the solution, and preferably at least partially drying, prior to compaction. Similarly, insoluble solid admixtures may be slurried in a liquid and the carrier contacted with the slurry to form a coated carrier prior to compaction. The self- indicating neutralizing composition units according to the present invention are sized so as to deliver a selected amount of pre-measured self-indicating neutralizing composition to a desired or standardized volume of aqueous solution. It is within the scope of the invention to use multiple units for a given volume of aqueous solution. It is further within the scope of the present invention for the self-indicating neutralizing composition 11 to be compacted into a unit 10 which is severable, such as by providing perforations 12 of the compact or the like, to provide selected, structurally stable fractions for smaller volumes of aqueous solution. (Fig. 1.) For practical considerations, the unit size is preferably small, so as to provide the most efficient packing and ease of handling. A preferred size of the unit is such that it can deliver sufficient self-indicating neutralizing composition for about 15 litres. For ease of handling and storability, the self-indicating neutralizing composition compacted units are preferably somewhat moisture resistant. Such moisture resistance may be imparted by the selection of an appropriate binder, preferably a binder which breaks down at a pH experienced by the unit in the aqueous solution, which may be at pH 11 and above. If such a binder is used, it is possible to produce a self-indicating neutralizing composition article without compaction For situations where the composition units must be stored in a substantially water-free environment, they may be stored individually, but preferably in number, in a sealable plastic bag such as those sold under the trademark "Zip-Loc". Any water-insoluble container, however, is suitable for such storage, so long as it is water-impermeable and not water- degradable. In a further embodiment of the invention, the compacted unit is coated with a material that is at least partially insoluble in water. Coating the compacted unit with a material that is substantially insoluble in water enhances the storage capabilities of the compacted unit in a moist environment and protects any hydroscopic components present in the self-indicating neutralizing composition. Such a water-insoluble coating should be capable of breaking or dissolving at the pH of the aqueous solution, and should preferably be thin, of the order of 0.025-0.25mm. In addition, the material should not be deleterious to the properties desired for the final product. The coating may be selected so as to protect the compacted unit, and/or to protect the user from any hazardous materials in the self-indicating neutralizing composition. Examples of suitable substantially water-insoluble materials include clays, latexes, polystyrenes, polyurethanes, and celluloses wherein the hydroxyl groups have been substituted with alkyls. More information regarding unitization of materials can be found in United States Patent No. 5,728,209 to Bury et al., which is incorporated herein by reference. The present invention also includes a method of neutralizing a solution to about a neutral pH. A v-initized composition is added to the solution and allowed to dissolve in the solution. If the pH indicator does not change color to indicate a pH of about neutral, then additional unitized compositions may be added until the pH indicator indicates a pH of about neutral. A further advantage of the compacted units of self-indicating neutrahzing composition according to the present invention, is that, unlike liquid compositions, they are not prone to freeze, slush or separate at low temperature. The use of compacted units of self-indicating neutralizing composition according to the present invention overcomes job site dusting problems associated with powders, avoids the use of bulky measuring dispensing equipment at the job site for liquids or solid free-flowing components, and overcomes spillage concerns associated with using components of the self-indicating neutralizing composition separately.

Claims: Claims 1. A unitized, self-indicating, neutralizing composition comprising a neutralizing agent, a binding agent, and a pH indicator. 2. The composition of claim 1 further comprising at least one of a disintegrant, a filler, and a carrier. 3. The composition of claim 2, wherein if present, the disintegrant is a effervescing agent. 4. The composition of claim 1, wherein the neutralizing agent is present from 45% to 85% by weight of the composition, the binding agent is present from 5% to 25% by weight of the composition, and the pH indicator is present from 0.001% to 0.8% by weight of the composition. 5. The composition of claim 2, wherein if present, the filler is present up to 95% by weight of the composition, the disintegrant is present from 1% to 30% by weight of the composition, and the carrier is present from 5% to 25% by weight of the composition. 6. The composition of claim 1, wherein the neutralizing agent comprises an organic chemical. 7. The composition of claim 2, wherein if present, the filler is selected from the group consisting of silica sand, silica fume, natural or synthetic silica-based materials, silicates, calcium aluminosilicate, aluminosilicates, clays, alumina, zeolites, ceramic spheres, fly ash, limestone powder, finely divided or powdered plastic, and mixtures thereof. 8. The composition of claim 1, wherein the composition further comprises a coating that is at least partially insoluble in water disposed over the composition. 9. A method of neutralizing a solution to about a neutral pH comprising: adding a sufficient amount of a unitized, self-indicating, neutralizing composition comprising a neutralizing agent, a binding agent, and a pH indicator to the solution until the solution has about a neutral pH as indicated by the pH indicator, wherein the neutralizing composition dissolves into the solution. 10. A method according to claim 9, wherein the solution is wash water from a cementitious composition.

Inventors: BUFFENBARGER JULIE K, GRAUER ZVI, LU RUNHAI, BUFFENBARGER, JULIE, K., GRAUER, ZVI, LU, RUNHAI
Applicants: MBT HOLDING AG
Application year: 2001
Main classification: C02F1
IPC codes: C02F1