Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
2001-07-13
2004-06-01
Tucker, Philip C. (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S265000, C507S273000, C507S209000, C507S211000, C507S207000, C507S216000, C507S224000, C507S939000, C524S275000, C524S072000, C525S403000, C525S409000, C516S104000, C516S109000, C516S108000, C106S017000, C106S018000, C106S018290, C424S401000, C424S070220, C424S405000
Reexamination Certificate
active
06743756
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stable concentrated non-aqueous suspensions of particles with excellent storage stability. More specifically, the particle suspensions are characterized by having a medium of low molecular weight polyalkylene glycol and a stabilizer of a hydrogenated castor wax.
2. Description of the Related Art
Heretofore, in preparing aqueous dilutions of particles, it has been necessary to utilize solid ingredients that are mixed with water or other aqueous fluid at the job site. A number of disadvantages are inherent in such mixing procedures, particularly when large volumes of solutions are prepared. For example, special mixing equipment for mixing the dry additives with water is required and problems such as chemical dusting, uneven mixing, and extended preparation and mixing time are involved. In addition, the mixing and physical handling of large quantities of dry chemicals require a great deal of manpower, and, where continuous mixing is required, the accurate and efficient handling of chemicals is extremely difficult.
In addition, when particles are used, they are typically added to water to make a dilute solution, resulting in the generation of fugitive dust. This dust has a number of potential detrimental effects. Workers preparing the solution can inhale the dust, and some of the particles that can be suspended in a non-toxic solvent produce dust when handled in a powdered form. This may produce a respiratory allergenic response, irritation, or other toxic effect when inhaled. Dust can also drift to areas where it is not intended.
In the agricultural industry, many handling problems may arise when one is forced to prepare aqueous end-use formulations and/or slurries from solids, especially active solids, e.g. wettable bioactive powders. Farmers preparing tank mixes of herbicides, insecticides and/or other bioactives from solids for applications to crops and soil are exposed to certain safety hazards and inconveniences due to the generation of noxious dusts which may be irritable to the skin and hazardous to breathe.
Additionally, finely ground powders, even so-called powders, of many water-soluble bioactives do not disperse well when prepared as tank mixes. They have poor spontaneity or “bloom” and have low suspendability. They have poor re-dispersibility and are incompatible with other bioactives as compared to liquid bioactive concentrates. Thus, final formulators, such as farmers, when preparing diluted aqueous active compositions find that the handling and application of solids materials, such as fertilizers, are much easier if the material can be supplied in a fluid rather than solid form. Economics then dictate that the active material be supplied in a highly concentrated fluid to the final formulator.
Saturation solubility in water of many water-soluble active constituents, such as potassium chloride, is too low to make it economical for supply to the end-user simply in the form of a solution. Alternatively, highly concentrated suspensions of water-soluble compounds, both in water and in organic liquids, have very poor storage, freeze/thaw, and heat/cool stability. As a result of the spontaneous crystal dissolution-recrystallization process, there occurs a progressive increase in the size of the particulate active material. This increase in particle size results in settling, bleed and changes in visco-elastic properties and thus severely limits concentrate loading levels.
To avoid lump or dust formation and its associated problems, the particles can be added to the aqueous systems as liquid slurries or suspensions. There currently exists a number of methods for accomplishing this, and the compositions prepared thereby. These methods often employ use oil carriers (e.g., mineral, isopariffin or diesel) to suspend and deliver the particles to the aqueous systems. In applications where the materials may be used in off-shore oil well treatment fluids which may be eventually discharged into the environment, recent regulations by the Environmental Protection Agency limit the amount of oil or grease that can be used in offshore oilfield applications for well treatment fluids. The National Pollutant Discharge Elimination System (NPDES) General Permit issued on Apr. 19, 1999 (Federal Register Vol. 64 No. 74) limits the oil and grease to a daily maximum concentration of 42 mg/l and a monthly average of 29 mg/l when the suspension is diluted to the intended use level with fresh or salt water. Unlike the liquid suspensions that contain diesel fuel or other hydrocarbon solvents the suspensions of the present invention contain minimal detectable oil or grease when diluted to the concentration appropriate for well treatment.
U.S. Pat. No. 5,091,448 discloses a suspending medium for a water-soluble polymer, while U.S. Pat. No. 5,631,313 discloses a suspending medium for particles. These two patents utilize isopariffin oils as the solvent for the suspensions where a styrene/isoprene copolymer is used as the suspension agent. Upon dilution to the intended use concentration in fresh or salt water for a well treatment fluid, the dilution contains a much higher concentration of oil and grease than is permitted by the above regulations. Furthermore the styrene/isoprene copolymer that is used to stabilize the suspension is insoluble in water miscible solvents such as the polyalkylene glycols of the present invention.
U.S. Pat. No. 5,925,182 discloses a stable liquid suspension composition including a liquid carrier, a solid fatty acid or a salt thereof, and a solid particulate wherein the liquid carrier is selected from the group consisting of oils, olefins, terpenes, glycols, esters, ethers, alcohols, and combinations of any two or more thereof and the liquid carrier, solid fatty acid or salt thereof, and solid particulate are each present in the composition in a stabilizing amount sufficient to produce a stable liquid suspension. Also disclosed is a stable liquid composition including a liquid carrier, an oil soluble polymer, and a solid particulate wherein the liquid carrier is selected from the group consisting of olefins, terpenes, esters, and combinations of any two or more thereof and the liquid carrier, oil-soluble polymer, and solid particulate are each present in the composition in a stabilizing amount sufficient to effect the formation of a stable liquid suspension. Although this patent includes some solvents that may be environmentally friendly and some that contribute to oil and grease as measured by the EPA method, the suspension agent is based on a fatty acid or salt thereof, or an oil soluble polymer, either of which will be measured as oil and grease.
In addition to the oil carrier fluid, many hydrocarbon solvent based slurries usually contain clay or clay like particulates that act to viscosity and stabilize the non-aqueous suspension. The clay component itself is also often times an undesirable component. This is particularly true in oil and gas field applications where incorporation of the clay into the slurries, which is necessary to keep the particles in suspension, impairs the permeability of the oil or gas bearing strata. This is the very same problem caused by the formation of lumps that the oil suspension or slurry is supposed to eliminate.
Many aqueous suspensions include a variety of inorganic and organic particles that use water as the continuous phase for preparing the liquid solution or suspension. While the use of water is certainly environmentally acceptable and reduces the dusting properties of many solid particles, its use is counterproductive with many solids. Among these are solids that may be reactive with water. Also, particles may be wholly or partially soluble in water and this solubility may limit the maximum concentration of the dispersed phase that can be incorporated into an aqueous suspension. The use of a non-solvent for suspending certain solids results in a controlled release of the solids because the particles must first dissolve into water before they become fu
Benchmark Research and Technology Inc.
Makay Christopher L.
Tucker Philip C.
LandOfFree
Suspensions of particles in non-aqueous solvents does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suspensions of particles in non-aqueous solvents, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suspensions of particles in non-aqueous solvents will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3317059