Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Reexamination Certificate
2001-01-26
2003-03-04
Hardee, John (Department: 1751)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S019910, C149S108800
Reexamination Certificate
active
06527885
ABSTRACT:
BACKGROUND OF THE INVENTION
Of the explosives used worldwide today, the ammonium nitrate explosives are the largest group. They are widespread particularly in mining. A particularly important group within the ammonium nitrate explosives in this connection are the emulsion explosives, which consist essentially of a water- (or salt)-in-oil emulsion of an aqueous solution, supersaturated at room temperature, in an oil matrix (fuel). The oil phase is the continuous phase and includes small droplets of the supersaturated solution of the oxidizing agent. In this connection, the water content of the solution can be up to below 4% by weight. The dissolved salts are metastable and have a tendency toward crystallization. If, for example, ammonium nitrate crystals form, this has unfavorable effects on the emulsion (solidification, the emulsion is no longer pumpable) and also on the cap sensitivity of the emulsion, i.e. the explosive becomes less sensitive to initial detonation. In order to keep such an emulsion stable, therefore, an emulsifier is generally required which is suitable for the preparation of water-in-oil emulsions. Because of its surface activity, it promotes emulsification of the salt phase in small droplets and prevents coalescence of the formed droplets after the emulsion has formed.
The emulsion, also called matrix, is generally still not ignitable, and therefore, in order to achieve sufficient cap sensitivity, the density of the matrix must be lowered by adding microspheres (glass bubbles), by chemical gassing or by another method, such as, for example, by adding granular ammonium nitrate. The emulsions are then in some circumstances also ignitable without boosters with blasting caps. Such emulsions are safety explosives. This technology was described for the first time in U.S. Pat. No. 3,447,978.
U.S. Pat. No. 3,447,978 discloses explosive emulsions consisting of a salt-in-oil emulsion of a supersaturated ammonium nitrate solution in an oil matrix, an emulsifier of the water-in-oil type, e.g. a sorbitan ester, fatty acid glycerides or phosphoric esters, being used as emulsifiers. These emulsifiers, however, only give emulsions with low long-term stability.
EP-A-0 155 800 discloses emulsion explosive material mixtures which comprise emulsifiers, where at least one emulsifier is strongly lipophilic and an agent for altering the electrical conductivity of the emulsion, which essentially consists of a lipophilic and of a hydrophilic component, and in which the lipophilic constituent has a chain structure derived from a polymer of a monoolefin containing 3-6 carbon atoms. In particular, reaction products of poly(isobutenyl)succinic anhydride with amino alcohols, amines and sorbitol as emulsifiers are described.
EP-A-0 285 608 discloses water-in-oil emulsions, where the emulsifiers present are reaction products of a hydrocarbon-substituted carboxylic acid or a hydrocarbon-substituted anhydride (or an ester or amide derived therefrom) with ammonia or at least one amine, the hydrocarbon radical having on average 20-500 carbon atoms. Polymers containing two or more hydrocarbon radicals are not disclosed. Reaction products of poly(isobutenyl)succinic anhydrides with morpholine and amino alcohols are specifically described.
The emulsifiers cited in EP-A-0 155 800 and EP-A-0 285 608 and based on polyisobutenylsuccinic anhydride (i.e. the reaction product of a long-chain, branched olefin with maleic anhydride), produce, in contrast to the emulsifiers of the first generation cited in U.S. Pat. No. 3,447,978, emulsions with high long-term stability. The base emulsifiers, however, have the disadvantage that their synthesis, because of the underlying ene reaction, requires very high temperatures (180-230° C.) and relatively long reaction times, which leads to a high consumption of energy and correspondingly high preparation costs.
Polymers of polyisobutylene and maleic anhydride are also part of the prior art. WO-A-90/03359 discloses polymers of polyisobutylene and maleic anhydride which, after they have been functionalized using polyamines, can be used as additives in fuels and lubricating oils. EP-A-0 831 104 discloses terpolymers of polyisobutylene, ∀-olefins and maleic anhydride and also reaction products of these terpolymers with polyamines for analogous applications.
The unpublished German Patent Application 198 47 868 describes modified copolymers of polyisobutene and maleic anhydride and, where appropriate, allylpolyglycol ethers as emulsifiers. These products are extremely effective emulsifiers for emulsion explosives. In contrast to the compounds cited in EP-A-0 155 800 and EP-A-0 285 608, these compounds have two or more hydrophobic groups and two or more hydrophilic head groups on the polymer backbone. The parent polymeric anhydrides can be prepared at a significantly lower temperature (80-150° C.) and by free-radical copolymerization significantly more quickly than the alkenylsuccinic acid derivatives of the prior art, meaning that they have ecological and also economic advantages over the prior art. Despite having molecular weights which are significantly higher than those of polyisobutenylsuccinic acid derivatives, the products do not have increased viscosities, meaning that the products can be handled without problems despite the relatively high molecular weight. In this connection, the emulsifying action and emulsion stability of the products, particularly in mixtures with small amounts of coemulsifiers, correspond to at least the products cited in the prior art. However, some of these substances tend to form clouding in the product.
SUMMARY OF THE INVENTION
However, this clouding can, surprisingly, be avoided if copolymers of polyisobutene, maleic anhydride and vinyl esters of carboxylic acids having 2 to 12 carbon atoms are used. These emulsifiers have an emulsifying action which is comparable or better than that of the compounds listed in German patent application 198 47 868 and are prepared in the same way with a low expenditure of energy, but form clear and stable products.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention thus provides an explosive composition comprising
A) an oxygen-donating constituent, which forms a disperse phase,
B) an organic constituent, which forms a dispersion phase, and
C) at least one emulsifier,
wherein the emulsifier includes a copolymer comprising, in random or regular order, structural units derived from
a) maleic anhydride,
b) one or more olefins having more than 40 carbon atoms, and
c) a vinyl ester of carboxylic acids having from 2 to 12 carbon atoms,
where the structural units derived from maleic anhydride have been modified by reaction with alcohols, amino alcohols, ammonia or amines.
In the text below, the term “maleic anhydride” also refers to the maleic anhydride modified in the sense given above by reaction with alcohols, amino alcohols, ammonia or amines.
The emulsifier according to the invention comprises, in the copolymer chain, at least one olefin, preferably an &agr;-olefin having more than 40, preferably from 40 to 500, in particular from 40 to 200, carbon atoms. The copolymer may also further comprise other comonomers.
Suitable olefins for the preparation of the polymers according to the invention are olefins preferably containing a double bond in the &agr;-position or mixtures of the number of such olefins. Particular preference is given to olefins obtained by polymerization of C
2
-C
6
-monoolefins, such as, for example, polypropylenes or polyisobutylenes in the molecular weight range from, preferably, 200-5000 g/mol, and which comprise >30%, preferably >50%, particularly preferably >70%, of isomers containing a double bond in the &agr;-position, i.e., for example, containing an end group R—C(═CH
2
)CH
3
. Such polyisobutylene grades are obtainable, for example, under the trade names Glissopal® or Ultravis®. In this connection, particularly suitable polyisobutylenes are those which have a high content of isomers containing an ∀-position double bond.
Suitable vinyl esters are viny
Bender Ralf
Klug Peter
Clariant GmbH
Hardee John
Silverman Richard P.
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