Stabilization and use of propargyl bromide

Plant protecting and regulating compositions – Plant growth regulating compositions – Organic active compound containing

Reexamination Certificate

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C514S745000

Reexamination Certificate

active

06777375

ABSTRACT:

BACKGROUND
Propargyl bromide (3-bromopropyne) is known to be useful as a soil fumigant for control of fungi, nematodes, and undesirable plant life. See for example U.S. Pat. No. 2,794,727. For such usage it would be necessary to store and transport propargyl bromide from its manufacturing site to other locations and ultimately to farmlands where it would be put to use. And, in order to utilize propargyl bromide most effectively as a soil fumigant it would be desirable to have the ability to use it in pressurized dispensing systems wherein the pressurized fumigant is injected subsurface to the soil during cultivation.
Propargyl bromide is, however, a high energy material that is sensitive to physical shock or impact, and that is also susceptible to rapid thermal decomposition upon exposure to high temperatures or fires. In order to more safely produce, purify, store, transport, handle and use propargyl bromide, it is desired to stabilize the propargyl bromide against physical shock and exposure to elevated temperatures both in the liquid and vapor phase especially when in a confined space. In addition, since use of propargyl bromide as a soil fumigant would often involve having the product housed in pressurized systems or containers so that it can be injected into the soil, stabilization of propargyl bromide against physical shock and exposure to elevated temperatures when confined under pressure is another goal to be accomplished.
The hazardous character of propargyl bromide has been recognized heretofore, and certain stabilizing materials have been proposed for use. For example, as indicated in Brit. 1,132,417, propargyl bromide is shock sensitive, and when in a confined space, propargyl bromide may ignite spontaneously and decompose with explosive violence, and may detonate. To provide stabilization, Brit. 1,132,417 indicates that certain solvents were effective, namely toluene, xylene, a non-cyclic ether, tetrahydrofuran, dioxane, beta-ionone, and ethanol. Brit. 1,132,417 further points out that many organic liquids had been tried for the purpose of stabilizing propargyl bromide, but only a few had been successful, that no firm rule had been established for predetermining which liquids would be successful and which would not, and that among materials that were tested and found ineffective were hexane, benzene, chloroform, formamide, and light petroleum oil.
In a paper entitled “Explosibility and Stabilization of Propargyl Bromide”,
Loss Prevention
, 1967, 1, 6-9, it is noted that propargyl bromide is sensitive to both shock and to temperature, and that under suitable conditions may be detonated, and that stabilization by dilution was explored as a possible solution to this problem. The authors of this paper report that at a diluent level of 15%, benzene, formamide, chloroform and hexane were judged by impact tests to be poor stabilizers for propargyl bromide, and that diethyl ether and diisopropyl ether appeared promising but were considered less attractive than toluene, xylene, and ethylhexylsorbitol. Based on processing considerations and impact test results, toluene and xylene were selected by the authors of this paper for further testing. In confinement tests toluene was judged by them to be the material of choice, especially at a dilution level of 20-30%. At present, propargyl bromide diluted with 20% of toluene is available as an article of commerce.
Unfortunately, toluene and xylene are both incapable of effectively stabilizing propargyl bromide in the vapor state. Thus conditions could be encountered in which propargyl bromide in admixture with toluene might nonetheless undergo explosive decomposition. Also, in order to use propargyl bromide as a soil fumigant it is important to avoid contaminating the soil with materials that leave residues that are not readily broken down by naturally-occurring microorganisms in the soil. Aromatic hydrocarbons such as toluene and xylene are not environmentally friendly as they are not rapidly consumed by such naturally-occurring microorganisms.
Thus a need exists for a new, environmentally-friendly way of effectively stabilizing propargyl bromide against both shock-induced and rapid heat-induced decomposition when in the vapor state and in the liquid state, and especially when under confinement under pressure. Because of the hazardous characteristics of propargyl bromide this need exists at all stages of its existence, including production, recovery, purification, handling, storage, transportation, and use.
This invention enables fulfillment of this and other needs as well.
BRIEF SUMMARY OF THE INVENTION
It has been found that propargyl bromide can be effectively stabilized by combining propargyl bromide with an environmentally-acceptable inert liquid solvent that forms an azeotrope with propargyl bromide, such as a paraffinic and/or cycloparaffinic hydrocarbon solvent that forms an azeotrope with propargyl bromide. By “azeotrope” is meant a mixture that under temperature and pressure conditions encountered at any normal stage of the life-cycle of propargyl bromide, the propargyl bromide and a stabilizing amount of the hydrocarbon when in the liquid or vapor state remain together at all times. Thus the stabilization activity provided by the solvents used pursuant to this invention protects the propargyl bromide against hazardous shock-induced or thermally-induced decompositions whether the propargyl bromide is in the liquid state or in the vapor state. And accordingly, it is now possible to produce, recover, purify, handle, store, transport, and use propargyl bromide without fear of disastrous consequences, such as those resulting from rapid exothermic decomposition.
By “environmentally-acceptable” is meant that the inert liquid satisfies or, if not yet evaluated, will satisfy the requirements for listing as an “inert” or “other ingredients” in categorized List 1, List 2, List 3, or List 4 of the Office of Pesticide Programs of the United States Environmental Protection Agency, such lists as updated Jun. 12, 2001. Such lists are incorporated herein by reference as if fully set forth herein, except that all substances on such lists which do not meet all criteria specified herein are excluded from such lists because they are incapable or unsuitable for use in the practice of this invention.
Another embodiment of this invention is a closed container such as a drum, tank, tank car, tank trailer, or the like containing (i) a solution comprising propargyl bromide and a solvent that is compatible with propargyl bromide, and (ii) a headspace or vapor space within said container, wherein said headspace or vapor space contains an inert gas such that the headspace or vapor space is devoid or substantially devoid of air and elemental oxygen. The solvent in this embodiment of the invention can be any solvent such as those described in Brit. 1,132,417, in the above paper entitled “Explosibility and Stabilization of Propargyl Bromide”,
Loss Prevention
, 1967, 1, 6-9, or U.S. Pat. No. 2,794,727, such as toluene or zylene, but preferably is an environmentally-acceptable inert liquid solvent that forms an azeotrope with propargyl bromide. More preferably, the solvent results in the composition being classifiable as a “flammable liquid”, in accordance with
Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria
, 3rd Revised Edition, published by United Nations, New York and Geneva, 1999 (ISBN 92-1-139068-0).
The various embodiments of this invention will be still further apparent from the ensuing description and appended claims.
FURTHER DETAILED DESCRIPTION OF THE INVENTION
This invention enables propargyl bromide to be protected from the moment of its creation until the moment of its ultimate consumption, provided the material does not encounter some extraordinary set of conditions along the way. And even if the propargyl bromide encounters a dangerous condition such as a fire during storage or transportation, a collision during transportation, or excessive heat and pressure buildup during confinement, the severity an

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