Fuel and related compositions – Liquid fuels – Heterocyclic carbon compound containing a hetero ring having...
Reexamination Certificate
2001-04-16
2002-05-21
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Heterocyclic carbon compound containing a hetero ring having...
C044S386000, C044S393000, C044S394000, C044S397000, C044S403000, C044S412000, C044S422000
Reexamination Certificate
active
06391070
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and compositions for increasing hydrocarbon conductivity, and more particularly relates, in one embodiment, to blends of halogen-free acrylate copolymer compositions with polysulfone copolymers that increase the conductivity of liquid hydrocarbons, such as solvents and fuels, and thereby control the build-up of potentially hazardous static charges in such liquids, and to methods of making and using such compositions.
BACKGROUND OF THE INVENTION
It is widely known that electrostatic charges can be frictionally transferred between two dissimilar, nonconductive materials. When this occurs, the electrostatic charge thus created appears at the surfaces of the contacting materials. The magnitude of the generated charge is dependent upon the nature of and, more particularly, the respective conductivity of each material.
Perhaps the most well-known examples of electrostatic charge build-up include those which occur when one shuffles across a carpeted floor or when one runs one's hand across another's hair or the fur of an animal. Although it is less commonly known, electrostatic charging can also occur when a solid is mixed with a liquid and when water settles through a hydrocarbon solution. It is the latter situations that are of greatest interest to the petroleum industry, for when such charges are built up in or around flammable liquids, their eventual discharge can lead to incendiary sparking, and perhaps to a serious fire or explosion.
While incendiary sparking is an ubiquitous problem in the petroleum industry, the potential for fire and explosion is probably at its greatest during product handling, transfer and transportation. For example, static charges are known to accumulate in solvents and fuels when they flow through piping, especially when these liquids flow through high surface area or “fine” filters and other process controls such as is common during tank truck filling. Countermeasures designed to prevent accumulation of electrostatic charges on a container being filled and to prevent sparks from the conducting container to ground can be employed, such as container grounding (i.e. “earthing”) and bonding. But it has been recognized that these measures are inadequate to deal successfully with all of the electrostatic hazards presented by hydrocarbon fuels.
Alone, grounding and bonding are not sufficient to prevent electrostatic build-up in low conductivity, volatile organic liquids such as distillate fuels like diesel, gasoline, jet fuel, turbine fuels and kerosene. Similarly, grounding and bonding do not prevent static charge accumulation in relatively clean (i.e. contaminant free) light hydrocarbon oils such as organic solvents and cleaning fluids. This is because the conductivity of these organics is so low that a static charge moves very slowly through these liquids and can take a considerable time to reach the surface of a grounded, conductive container. Until this occurs, a high surface-voltage potential can be achieved which can create an incendiary spark. ignition or explosion can thus occur in an environment of air-hydrocarbon vapor.
One can directly attack the source of the increased hazard presented by these low conductivity organic liquids by increasing the conductivity of the liquid with additives. The increased conductivity of the liquid will substantially reduce the time necessary for any charges that exist in the liquid to be conducted away by the grounded inside surface of the container. Various compositions are known for use as liquid hydrocarbon additives to increase the electrical conductivity of these liquids. For example, in U.S. Pat. Nos. 3,578,421; 3,677,724; 3,807,977; 3,811,848; and 3,917,466 there are described anti-static additives generally of the alpha-olefin-sulfone copolymer class. In U.S. Pat. No. 3,677,725 an anti-static additive of the alpha-olefin-maleic anhydride copolymer class is described. Anti-static amines and methyl vinyl ether-maleic anhydride copolymers are described in U.S. Pat. No. 3,578,421. Still further, anti-static aliphatic amines-fluorinated polyolefins are described in U.S. Pat. No. 3,652,238. Similarly, anti-static chromium salts and amine phosphates are disclosed in U.S. Pat. No. 3,758,283. And, in U.S. Pat. No. 4,333,741 there are disclosed olefin-acrylonitrile copolymers for use as anti-static additives in hydrocarbons.
The olefin-acrylonitrile copolymeric compositions, as indicated above, have proved effective as anti-static agents or “static dissipators,” as they are also known, when combined with volatile liquid hydrocarbons.
In the past, halogen-containing compositions introduced into fuels have played a significant role in achieving anti-static properties in fuels. While these halogen-containing compositions are effective as anti-static agents, in certain situations, some halogen-containing hydrocarbon compounds have been linked to human and animal health risks as well as environmental degradation. Legislative enactments, including the 1990 amendment to “The Clean Air Act” in the United States, signal a trend away from the continued permissible use in some media of compositions containing halogens. Even where the use of halogen-containing compositions is still permitted, stringent regulations often govern the use, storage and, in particular, the disposal of and/or treatment of waste streams containing these compositions. Such factors call into question the continued practical and economic feasibility of anti-static agents containing halogens without regard to the media being treated.
Other prior art compositions have necessarily contained as much as about 10% (by weight of active ingredients) sulfur in a form that increases or creates sulfur contamination of the fuels or other fluids upon their addition thereto. Sulfur in various forms, such as sulfur dioxide, is known as an undesirable contaminant. Its undesirability is due to a variety of reasons, including the problems it causes in handling and its interference with, or undesirable side effects encountered in, the end uses of the sulfur-contaminated fluid. While the presence of sulfur in certain forms in certain fluids is acceptable, it is preferred to minimize the presence of sulfur.
U.S. Pat. No. 5,672,183 concerns a composition having increased electrical conductivity, comprising a liquid hydrocarbon and an anti-static amount of a hydrocarbon soluble copolymer of an alkylvinyl monomer and a cationic vinyl monomer. The copolymer has an alkylvinyl monomer unit to cationic vinyl monomer unit ratio of from about 1:1 to about 10:1, and an average molecular weight of from about 800 to about 1,000,000.
A need has therefore clearly arisen for an effective, low cost anti-static agent that is useful with a wide variety of volatile hydrocarbon liquids. It is especially desirable in many situations that the agent be free of halogens.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel liquid hydrocarbon composition having increased electrical conductivity.
It is another object of the present invention to provide a method to effectively reduce accumulated static electrical charge on a surface of a liquid hydrocarbon.
In carrying out these and other objects of the invention, there is provided, in one form, a composition having increased electrical conductivity, which includes a) a liquid hydrocarbon; b) an anti-static amount of at least one hydrocarbon soluble copolymer of an alkylvinyl monomer and a cationic vinyl monomer, wherein the copolymer has an alkylvinyl monomer unit to cationic vinyl monomer unit ratio of from about 1:1 to about 10:1, the copolymer having an average molecular weight of from about 800 to about 1,000,000; and c) an anti-static amount of at least one hydrocarbon soluble polysulfone copolymer of at least one olefin and sulfur dioxide.
Among the several advantages found to be achieved by the present invention, therefore, may be noted the provision of a composition and method that provides improved anti-static properties for a
Baker Hughes Incorporated
Madan Mossman & Sriram P.C.
Medley Margaret
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