Chemistry of inorganic compounds – Halogen or compound thereof – Hydrogen halide
Reexamination Certificate
1996-03-07
2001-01-23
Nguyen, Ngoc-Yen (Department: 1754)
Chemistry of inorganic compounds
Halogen or compound thereof
Hydrogen halide
C423S484000, C423S488000, C516S105000, C516S106000, C516S107000, C524S438000, C524S462000, C206S000600, C206S000700, C206S335000
Reexamination Certificate
active
06177058
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to hydrogen fluoride compositions. More particularly, the present invention provides compositions of hydrogen fluoride and a polymer that are less hazardous and, therefore, more easily stored, transported, and handled in comparison to pure hydrogen fluoride.
BACKGROUND OF THE INVENTION
Hydrogen fluoride is a well known compound that is used in industry in a variety of processes including in alkylation reactions as a catalyst, in fluorination reactions as a fluorinating agent, in the manufacture of fluorides, in the separation of uranium isotopes, and in the production of fluorine containing plastics. It is well known that hydrogen fluoride is a volatile, extremely hazardous substance the high vapor pressure of which renders it readily aerosolizable.
In an attempt to diminish the hazards of hydrogen fluoride, it has been combined with a variety of substances. U.S. Pat. No. 1,470,772 discloses a glass etching paste of mucilage, sulfuric acid, and ammonium fluoride in which the hydrogen fluoride is formed in situ. U.S. Pat. No. 3,635,836 discloses dispersions of hydrogen fluoride, particulate proteinaceous material and a small amount of carboxyl substituted vinyl polymers useful as pickling agents, plumbing cleaners and paint removers. U.S. Pat. No. 4,383,868 discloses a method of treating anhydrous hydrogen fluoride spills by applying a particulate mixture of polyacrylamide and a polyalkyl(alk)acrylate to the surface of the spill. None of these compositions provides an intimate mixture of hydrogen fluoride and a substance that both reduces the hazards of hydrogen fluoride and, at the same time, permits the ready recovery of the hydrogen fluoride from the composition.
DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS
The present invention provides liquid and solid hydrogen fluoride compositions that are a convenient means of using, transporting, and storing hydrogen fluoride, the compositions being less hazardous than pure hydrogen fluoride. Further, the chemical properties of the hydrogen fluoride in the compositions of the present invention are substantially unchanged from those of hydrogen fluoride in its pure state and hydrogen fluoride may be quantitatively recovered from the compositions.
The compositions of the invention comprise intimate mixtures of hydrogen fluoride and an effective amount of a water-soluble polymer. The term polymer, for purposes of this invention, includes homopolymers, copolymers, and mixtures thereof. It has been discovered that certain polymers in intimate mixture with hydrogen fluoride provide a composition in which hydrogen fluoride volatility is diminished. Additionally, the compositions of the invention are more viscous and have a greater surface tension when compared to pure hydrogen fluoride, hindering formation of a hydrogen fluoride aerosol cloud.
Generally, the polymers used in the invention have molecular weights of from about 5,000 to about 10,000,000. Preferably, polymers with molecular weights of from about 5,000 to about 1,000,000 are used. The polymers useful in the compositions of the invention are water-soluble polymers. By “water-soluble polymer” is meant any high molecular weight compound that swells, to about twice its dry volume, or dissolves with the addition of water at room temperature.
Water-soluble polymer is meant to include semi-synthetic water-soluble polymers, synthetic water-soluble polymers, and mixtures thereof. Semi-synthetic water-soluble polymers are natural water-soluble polymer derivatives. Synthetic water-soluble polymers are not natural water-soluble polymer derivatives and are formed only through chemical reactions.
Exemplary semi-synthetic water-soluble polymers include, without limitation, cellulose ethers, modified starches, starch derivatives, natural gum derivatives, and mixtures thereof Illustrative synthetic water-soluble polymers include, without limitation, polymers, related polymers, and polymer salts of acrylamide, acrylic acid, ethylene oxide, methacrylic acid, polyethyleneimine, polyvinyl alcohol, polyvinyl pyrrolidone, and mixtures thereof. By related polymer is meant that the polymer repeat unit, or a branch thereof, is extended by carbon atoms, preferably from one to four carbon atoms. For example, a related polymer of acrylic acid is one in which the vinyl group is extended by one carbon to form an allyl group.
Preferably, a synthetic water-soluble polymer is used. More preferably, polyacrylic acid or one of its salts is used. Most preferably, the water-soluble polymer is sodium polyacrylate.
To prepare the compositions of the invention, an effective amount of a water-soluble polymer is mixed with hydrogen fluoride in any suitable corrosion resistant vessel to form an intimate mixture. An effective amount of polymer is an amount capable of decreasing the volatility and increasing the surface tension of the hydrogen fluoride to the level desired for the end use. Addition of the polymer and hydrogen fluoride may be performed in any sequence. Mixing may be accomplished by any means convenient, including without limitation stirring or dispersing the polymer into a pool of hydrogen fluoride or passing hydrogen fluoride gas over the polymer. The hydrogen fluoride may be commercially available anhydrous hydrogen fluoride having a water content of 0.1% or less or aqueous hydrogen fluoride. Preferably, anhydrous hydrogen fluoride is used. The polymer may be in any form suitable for mixing with the hydrogen fluoride including, without limitation, granules, beads, pellets, fibers, or mats. Mixing will occur faster for smaller particle sizes of the polymer and slower for larger sizes. Typically mixing is performed at temperatures from about 0 to about 100° C., preferably from about 10 to about 40° C. Pressure is not critical.
The amount of hydrogen fluoride and polymer used will depend in part on the polymer selected and the desired end-use for the composition. If the polymer has a relatively low molecular weight, the resulting HF/polymer composition will be a viscous liquid. If the polymer has a relatively high molecular weight, the resulting composition will be a solid or gel-like solid. Additionally, the amount of polymer used will determine whether or not the resulting composition is a solid or liquid. Generally, when up to about 20 percent by weight, based on the total weight of the composition, of polymer is used the composition will be a viscous liquid. Compositions in which the amount of polymer is at least about 25 weight percent, generally, will take a gel-like solid form.
It should be noted further that the higher the weight percentage of polymer used, the greater the reduction in hydrogen fluoride aerosolization. However, with an increase in weight percentage of polymer, the weight percentage of hydrogen fluoride in the composition decreases which may affect the composition's suitability for a desired end-use. Therefore, the effective amount of hydrogen fluoride and polymer used will depend on a consideration of a number of factors. Generally, from about 2 to about 99.9 weight percent of polymer and from about 98 to about 0.1 weight percent of hydrogen fluoride is used. Preferably, from about 2 to about 50 weight percent polymer and from about 98 to about 50 weight percent hydrogen fluoride, more preferably from about 5 to about 25 weight percent of polymer and from about 95 to about 75 weight percent of hydrogen fluoride is used.
Without departing from the scope of the invention, it will be recognized that other components may be included in the compositions of this invention. The specific nature of these components will depend on the desired end use of the compositions. In general, any component that does not deleteriously effect the surface tension of the composition, or undesirably increase the volatility of the hydrogen fluoride component, may be used.
The hydrogen fluoride may be recovered readily from the composition of the invention by treating the composition so as to liberate hydrogen fluoride vapors. One means of t
Kieta Harold John
Luly Matthew Hermes
McKown Jeffrey Warren
Rygas Tadeusz Piotr
Shankland Ian Robert
Allied-Signal Inc.
Collazo Marie L.
Nguyen Ngoc-Yen
Szuch Colleen D.
LandOfFree
Hydrogen fluoride compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydrogen fluoride compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydrogen fluoride compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452367