Liquid purification or separation – Processes – Preventing – decreasing – or delaying precipitation,...
Reexamination Certificate
2000-12-21
2001-11-27
Henderson, Christopher (Department: 1713)
Liquid purification or separation
Processes
Preventing, decreasing, or delaying precipitation,...
Reexamination Certificate
active
06322708
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to novel low molecular weight, structured polymer compositions. The invention also relates to methods for inhibiting scale formation, precipitation or deposition; increasing dispersion of insoluble precipitates in process waters; treating cooling and boiler water; and reducing the viscosity of mineral slurries using the aforementioned polymer compositions.
BACKGROUND OF THE INVENTION
Industrial and residential waters contain naturally occurring contaminates (i.e., calcium, iron, barium, bicarbonate, carbonate, oxide, oxylate, sulfate, phosphate, zinc, etc.) that under conditions of use can chemically combine to form water insoluble precipitates. Additionally, water insoluble contaminates such as clay, silica and iron oxides can settle out of the water. These precipitates and inert materials can collect on surfaces of containers and piping in the form of deposits and scale, which reduce heat transfer, inhibit flow, increase likelihood of corrosion and enhance bacterial growth. In mining applications, compositions which aid in fluidizing insoluble particulates are desirable in order to more efficiently procure and transport the mined materials.
Current mechanisms for controlling scale and deposits involve preventing formation of insoluble precipitates (e.g., limiting crystal growth) or keeping inert insoluble materials dispersed in the system. Dispersants fluidize precipitates, silts, solids and combinations thereof. Chelants or sequestering agents can be used to bind cations to help prevent the formation of insoluble precipitates. Surface active agents can be used to aid in the dispersion of inert clays and silica. By nature, some of these agents may also be useful in fluidizing high solids slurries of ores and minerals.
Certain low molecular weight organic polymers (less than 100,000 MW) are capable of both inhibiting precipitation and keeping insoluble contaminates dispersed. These polymers are comprised of polycarboxylic and polysulfonic acids and their salts, copolymers of these acids, and co- and interpolymers of these acids with acrylamide, cationic monomers, vinyl esters and ethers.
In U.S. Pat. No. 3,463,730, Booth and Mead describe a process for controlling or preventing scale deposits in aqueous systems by addition of a low molecular weight (1,000-8,000) unhydrolyzed polyacrylamide. Booth and Cornelius, in U.S. Pat. No. 3,709,815 disclose polymers containing 2-acrylamido-2-substituted propane-1-sulfonic acid with an average molecular weight of at least 20,000 for use as boiler water dispersives and conditioners. In U.S. Pat. No. 3,898,037, Lange et al., describe polymers and co-polymers of acrylamido-sulfonic acid used in dispersing water-insoluble compounds of iron, calcium, magnesium, aluminum and commonly occurring particles of silt and clay. Amick et al., in U.S. Pat. No. 4,711,725, disclose a variety of copolymers, terpolymers and interpolymers also utilzed for these applications. In each patent, the polymers described are linear in structure and completely water-soluble.
Low molecular weight organic polymers that are linear and water soluble have also been disclosed to fluidize or disperse minerals in high concentration slurries. This allows more economical storage and transport forms of the minerals. Amick et al., in U.S. Pat. No. 4,711,725 demonstrates the abilities of co- and terpolymers of carboxylic and sulfonic acids to reduce the viscosity of clay and calcium carbonate slurries. Again, these polymer compositions have a linear structure and are water soluble.
Structured, high molecular weight polymers have been previously disclosed. Ryles et al., in U.S. Pat. No. 5,171,808, disclose cross-linked, anionic or amphoteric, organic, polymeric microparticles for use in flocculating dispersions of suspended solids. In European Patent Application 0 374 458, Neff et al. disclose water-soluble, branched polymeric flocculants based on polymerization of ethlyenically unsaturated monomers and branching agents in the presence of a chain-transfer agent. Both of these patents disclose compositions of high molecular weight polymers used as flocculating agents, and used to induce massing and precipitation of insoluble materials rather than dispersion of insoluble materials in a multiphase system.
While the aforementioned compositions utilized as scale inhibitors and dispersants may be applicable under specific conditions, they are only moderately effective or ineffective under certain circumstances. Therefore, a need exists for alternative compositions and methods for inhibiting scale formation, precipitation or deposition; increasing dispersion of insoluble precipitates in process waters; treating cooling and boiling water; and reducing the viscosity of mineral slurries.
SUMMARY OF THE INVENTION
This invention provides novel low molecular weight structured polymer compositions comprising ethylenically unsaturated monomers and structure-inducing agents. These structured polymers possess molecular structure that is branched, cross-linked or some combination thereof, as opposed to polymers that possess linear molecular structure. The structured polymers of this invention have improved capability for inhibiting the formation, precipitation or deposition of scale, improved capability of dispersing insoluble precipitates in aqueous systems, improved capability in treating cooling and boiler water, and improved capability to reduce the viscosity of mineral slurries compared to existing polymers.
It is a principal object of this invention to provide polymer compositions having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer or salts thereof, and at least one structure-inducing agent.
Other objects of this invention are to provide: methods for inhibiting scale formation, precipitation or deposition in an aqueous medium comprising the step of adding to said aqueous medium an effective amount of a polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent; methods for increasing dispersion of insoluble precipitates in process waters comprising the step of adding to said process waters an effective amount of a polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent; methods of treating cooling and boiler water comprising the step of adding to said cooling and boiler water an effective amount of a polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent; and methods of reducing the viscosity of a mineral slurry comprising the step of adding to said slurry an effective amount of the polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent.
DETAILED DESCRIPTION OF THE INVENTION
In order that the invention herein described may be more fully understood, the following detailed description is set forth. In the description, the following abbreviations are used:
Designation
Reagent or Fragment
AA
acrylic acid
AM
acrylamide
AMPS
2-acrylamido-2-methylpropane sulfonic acid
COM.
commercial
DADMAC
diallyldimethylammonium chloride
EDTA
ethylenediaminetetraacetic acid
GPC
gel permeation chromatography
MA
methyl acrylate
MAn
maleic anhydride
MBA
methylenebisacrylamide
MBS
sodium metabisulfite
ME
2-mercaptoethanol
NVP
N-vinylpyrrolidone
PAA
polyacrylic acid
SAHS
sodium allyloxy-2-hydroxypropylsulfonate
T-BAM
t-butylacrylamide
The following terms are employed herein:
The term “branching” refers to the creation of branches or additional termini relative to the two original termini that exist in linear entities.
The term “branching agent” refers to an agent which causes branching to occur.
The term “cross-link” refers to an interconnection between polymer chains.
The term “cross-linking agent” refers to an agent which induces cross-linking, branching or a combination thereof to occur.
The term “ethylenically unsaturated” refers to the presence of at least one unsaturated
Dixon Lisa A.
Fish & Neave
Henderson Christopher
Hintz John M.
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