Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Maintaining environment nondestructive to metal
Reexamination Certificate
1999-05-03
2003-07-01
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Maintaining environment nondestructive to metal
C422S011000, C422S012000, C252S180000, C252S390000, C252S394000, C252S395000, C252S396000
Reexamination Certificate
active
06585933
ABSTRACT:
Metals are widely used in the construction of equipment associated with aqueous systems. By “aqueous systems” it is meant any system containing metals which contain or are or contacted with aqueous fluids on a regular basis. Water-based fluids are typically fluids that contain at least about 50 weight percent water, the remainder being solids (suspended and/or dissolved) and/or nonaqueous fluids. The term aqueous fluids is intended to include not only water-based fluids, but also fluids that are predominantly non-aqueous but have sufficient water present, at least about 5 weight percent water, so that water soluble treatment components may be effectively employed to limit corrosion. Such non-aqueous fluids may be miscible or immiscible with water.
Typical aqueous systems include, but are not limited to, open recirculating cooling systems which obtain their source of cooling by evaporation, closed loop cooling systems, boilers and similar steam generating systems, heat exchange equipment, reverse osmosis equipment, oil production systems, flash evaporators, desalinization plants, gas scrubbers, blast furnaces, paper and pulp processing equipment, steam power plants, geothermal systems, food and beverage processing equipment, sugar evaporators, mining circuits, bottle washing equipment, soil irrigation systems, closed circuit heating systems for residential and commercial use, aqueous-based refrigeration systems, down-well systems, aqueous machining fluids (e.g. for use in boring, milling, reaming, broaching, drawing, turning, cutting, sewing, grinding and in thread-cutting operations, or in non-cutting shaping, spinning, drawing, or rolling operations), aqueous scouring systems, aqueous glycol anti-freeze systems, water/glycol hydraulic fluids, ferrous-surface pre-treatment, polymer coating systems, and the like. Various types of water may be utilized in such systems, for example fresh water, brackish water, sea water, brines, sewage effluents, industrial waste waters, and the like.
The aqueous systems that may be treated using the compositions of this invention may contain dissolved oxygen, such as might be obtained from absorbing oxygen from ambient air, or they may be substantially or completely oxygen free. Further, the aqueous system may contain other dissolved gases such as carbon dioxide, hydrogen sulfide, or ammonia, or they may be substantially or completely free of such gases.
There may be several different types of corrosion encountered in aqueous systems. For example, aqeuous systems may have uniform corrosion over the entire metal surface. The aqueous system may also have localized corrosion, such as pitting or crevice corrosion, where the corrosion is found only in certain locations on the metal surface. Often, control of localized corrosion may be the critical factor in prolonging the useful life of the metal equipment in the aqueous system. In particular, aqueous systems which contain high levels of aggressive anions such as chloride and sulfate are particularly prone to both generalized and localized attack. These aggressive anions may be present in the water source used for the aqueous system at levels that cause problems, or they may be concentrated to harmful levels in the aqueous system because they are part of a system that evaporates water such as an evaporative cooling system.
Localized corrosion may pose even a greater threat to the normal operation of the system than general corrosion because such corrosion will occur intensely in one location and may cause perforations in the system structure carrying the fluid stream. Obviously, these perforations may cause leaks which require shutdown of the entire aqueous system so that repair can be made. Indeed, corrosion problems usually result in immense maintenance costs, as well as costs incurred as a result of equipment failure. Therefore, the inhibition of metal corrosion in aqueous systems is critical.
In the descriptions that follow, we utilize the terms oligomer, polymer, co-oligomer, and co-polymer. By oligomer we mean materials produced by the polymerization of a single monomer where the number of monomer units incorporated in the product is between 2 and about 10. By polymer, we mean materials produced by the polymerization of a single monomer without restriction on the number of monomer units incorporated into the product. By co-oligomer, we mean materials produced by the polymerization of more than one type of monomer (including 2, 3, 4, etc. different monomers) where the total number of monomer units incorporated in the product is between 2 and about 10. By co-polymers, we mean materials produced by the polymerization of more than one type of monomer (including 2, 3, 4, etc. different monomers) without restriction on the number of monomer units incorporated into the product.
We have discovered that certain tetrazolium compounds given by the generalized formula:
wherein R
1
, R
2
and R
3
can be various organic and inorganic substituents, e.g., from the group consisting of lower alkyl, branched lower alkyl, aryl, substituted aryl, alkylaryl, substituted alkylaryl and heterocyclic substituted aryl with the proviso that none of R
1
, R
2
or R
3
contain more than 14 carbon atoms, and n may be 1 or 2, synergistically combine with a wide range of compounds to provide effective general and localized corrosion protection for metals in aqueous systems. If the components chosen to be combined with the tetrazolium compounds are also scale and/or deposition inhibitors, the combinations will also provide scale and/or deposition inhibition for these aqueous systems.
Anions and/or cations may be associated with the above structure to balance the charge depending upon the substitutions employed. If R
1
, R
2
and R
3
are all neutral, then the structure shown in the above formula will be positively charged and anionic species will be needed.
Examples of such tetrazolium compounds that may be utilized according the this invention include Nitroblue Tetrazolium chloride (3,3′-(3,3′-Dimethoxy-4,4′-biphenylene)-bis-[2-p-nitrophenyl-5-phenyl-2H-tetrazolium chloride]), hereafter referred to as NBT, Distyryl Nitroblue Tetrazolium Chloride (2,2′-Di-p-nitrophenyl-5,5′-distyryl-3,3′-[3,3′-dimethoxy-4,4′-biphenylene]ditetrazolium chloride), hereafter referred to as DNBT, Tetranitroblue Tetrazolium chloride (3,3′-(3,3′-Dimethoxy-4,4′-biphenylene)-bis-[2,5-p-nitrophenyl-2H-tetrazolium chloride]), hereafter referred to as TNBT, and Iodonitro tetrazolium chloride (2-(4-Iodophenyl)3-(4-nitrophenyl)-5-phenyltetrazolium chloride) hereafter referred to as INT.
Examples of compounds that may be combined with the tetrazolium compounds to provide synergistically improved corrosion protection include: inorganic phosphates, such as orthophosphates or polyphosphates, borates, nitrites, and compounds that release a metal anion in water, where the metal anion is selected from the group consisting of molybdates, tungstates, vanadates, metavanadates, chromates or mixtures thereof.
Additional materials that may be combined with the tetrazolium compounds include polycarboxylates. The polycarboxylates may be simple aliphatic compounds containing between 4 and about 20 carbon atoms which are multiply substituted with carboxylate groups (e.g., C
4
-C
15
&agr;,&ohgr;-dicarboxylates or compounds such as 1,2,3,4-butanetetracarboxylic acid) or may be polymeric compounds. The polymeric polycarboxylates may be homopolymers or copolymers (including terpolymers, tetrapolymers, etc.) of ethylenically unsaturated monomers that contain a carboxyl group. Examples of such polymeric polycarboxylates include polyacrylic acid, polymaleic acid, and polymaleic anhydride. Additionally, the polycarboxylates may be hydrocarbyl polycarboxylates as disclosed in U.S. Pat. No. 4,957,704, herein incorporated by reference.
Additional materials which may be combined with the tetrazolium compounds of the present invention include alkyl hydroxycarboxylic acids or a mixture of su
Cheng Longchun
Ehrhardt William C.
Stasney Dawn
Whitaker Kim A.
BetzDearborn Inc.
Boyd Steven D.
Cross LaToya I
Warden Jill
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