Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Specific organic component
Reexamination Certificate
2000-07-28
2003-07-29
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Specific organic component
C510S492000, C510S506000, C588S259000
Reexamination Certificate
active
06599872
ABSTRACT:
INTRODUCTION
The present invention relates to materials and methods for the treatment of hazardous waste spills, especially work place spills of liquid hazardous materials.
BACKGROUND
It is known to use a layer of foam as a temporary blanket or cover over hazardous material spills. Persistent foams are taught, for example, in U.S. Pat. No. 5,434,192 to suppress the release of hydrocarbon and polar organic vapors during loading of oil tankers, as well as during the transportation, transfer, storage and accidental storage and accidental spillage or crude oil and the like. Aqueous foamable compositions for fighting fires on hydrophobic or hydrophilic liquids are disclosed in U.S. Pat. No. 4,060,489. Each of the two foregoing U.S. patents is incorporated herein by reference in its entirety. Aqueous film-forming foam (AFFF) compositions and other fire fighting foam compositions (such as protein, fluoroprotein and synthetic detergents), referred to here in some cases as aqueous foamable concentrates, are known for these and other applications. Improved compositions are required, however, for treating liquid hazardous waste spills, especially spills of non-neutral pH liquid hazardous materials, that is, spills of acidic or caustic liquids, and especially workplace spills. The paper industry is under pressure to substitute chlorine dioxide for aqueous solution chlorine in paper production processes. Chlorine dioxide is slightly (typically up to about 13%) soluble in water to produce a highly acidic liquid, which decomposes violently, liberating heat, chlorine gas and nascent oxygen. When aqueous chlorine dioxide solution is spilled, noxious vapor of chlorine dioxide gas is readily liberated to the atmosphere. Agitation of spilled chlorine dioxide solution can cause increased release of vapors to the atmosphere. Spraying with water can cause such undesirable agitation and, in addition, can cause an unwanted temperature increase in the spilled material, with consequent increased vapor release, due to heat of reaction released during rapid mixing of the spray water with the acidic chlorine dioxide solution. Likewise, certain aqueous foams breakdown too rapidly over chlorine dioxide spills or other non-neutral pH liquids, thereby causing rapid heating and vapor release. More persistent foams, while avoiding such undesirable heating of the spilled non-neutral pH liquid, may merely blanket the spill and, perhaps, even inhibit effective access for treatment and clean up.
In view of the foregoing difficulties, strongly acidic liquids, such as chlorine dioxide solution spills, cannot always be effectively treated with current methods. Agents such as known aqueous film-forming foams tend to be too rapidly broken down upon application to such spills, potentially causing excessive heating and increased vapor release and requiring application of an undesirable number of additional layers to maintain an unbroken foam blanket over the spill. In addition, treatment employing certain known AFFFs is unsatisfactory, as chlorine dioxide has been reported to have violent reactions with materials frequently employed in such formulations, such as sugar, sulfur, fluorine and difluroamine.
As noted above, foam stability can be an important consideration for treating acidic or caustic spills. Heating of the hazardous liquid due to the exothermic neutralization reaction can be high enough to raise the temperature of the spilled liquid sufficiently to cause substantial increase in vapor release and deterioration of the foam blanket. Three factors have been suggested to control foam stability. In the first stage of foam life, water drainage may primarily control foam stability. As water drains from the foam films or lamellae, the films thin quickly to a small thickness. In a subsequent stage of foam decay, the bubbles slowly begin to collapse or coalesce into fewer, but larger bubbles. Gas diffusion and, more importantly, water evaporation from the foam lamellae may be the primary cause of foam collapse during this stage. In a final or near final stage, foam lamellae becomes so thin that even small pertabations, such as vibrations, shocks or sudden pressure or temperature changes can cause the remaining foam colunms to collapse catastrophically, resulting in breaks or breaches in the foam blanket.
Accordingly, it is an object of the present invention to provide treatment methods and materials to address the problems set forth above. It is a particular object of the invention to provide methods and materials for treatment of hazardous materials spills, especially non-neutral pH liquids, for example chlorine dioxide solutions and other fuming acids and bases. These and other objects and features of the invention will be readily apparent from the following disclosure and Detailed Description of Certain Preferred Embodiments.
SUMMARY
In accordance with a first aspect, aqueous foamable concentrates are provided, comprising foam-forming agent, foam stabilizing polymer and non-aqueous solvent, i.e., solvent additional to water used in the concentrate, effective to solublize the other ingredients of the aqueous foamable concentrate. The aqueous foamable concentrates disclosed here are pH-tolerant and slow-draining. More specifically, foams formed by foaming the aqueous foamable concentrate with water or other aqueous solution are suitable for deployment over non-neutral pH hazardous liquids, including highly-acidic and highly-caustic liquids. The foams are pH-tolerant in that the foam lamellae, when deployed over such non-neutral pH spills, remain slow-draining. That is, water drains from the foam sufficiently slowly so as to avoid excessive heating of the underlying acidic or caustic spill with consequent rapid breaking-up of the foam blanket.
In accordance with another aspect, methods for treating hazardous material spills are provided, in which pH-tolerant and slow-draining foams prepared from the aqueous foamable concentrates disclosed here are deployed over spills of non-neutral pH liquids. In accordance with a preferred and especially advantageous aspect, the foams are formed with non-neutral pH aqueous solutions. For treatment of an acidic spill, a caustic aqueous solution would be employed to produce the foam from the aqueous foamable concentrate. Similarly, a caustic aqueous solution would be used to produce a correspondingly caustic foam for treatment of an acidic spill. In the specific case of a chlorine dioxide liquid spill, a caustic aqueous solution would be employed with the aqueous foamable concentrates disclosed here to produce a caustic, pH-tolerant, slow-draining foam deployed over the chlorine dioxide liquid spill. Caustic aqueous solution drains from the foam into the underlying chlorine dioxide liquid at a rate sufficiently slow to avoid overheating of the chlorine dioxide liquid and increased vapor release beyond merely containing the chlorine dioxide liquid and vapors. The caustic foam serves to, therefore, neutralize or partially neutralize the chlorine dioxide liquid as it breaks down, and the slow-draining nature of the film preserves the integrity of the foam blanket and its vapor containment performance during the neutralization process. In accordance with especially preferred embodiments, non-neutral pH foams disclosed here, deployed over an oppositely non-neutral pH spill (i.e., caustic foam deployed over a ClO
2
or other acidic spill, or acidic foam deployed over a caustic spill) in sufficient quantity (i.e., in sufficient foam density and thickness) to neutralize the spill to pH 7±1, are sufficiently pH-tolerant and slow-draining to remain as a substantially continuous blanket over the spill at least about 15 minutes, more preferably at least about 30 to 60 minutes even when the pH difference between the foam and the original spill is 8 pH units or more, preferably even 12 pH units or more.
It is a particular advantage of the aqueous foamable concentrates according to these preferred embodiments, that they are suitable for mixing with either acidic or caustic aqueous solutions in
Hubert Mitchell J.
Walker Gregory R.
Ansul Incorporated
Banner & Witcoff , Ltd.
Gupta Yogendra N.
Webb Gregory E.
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