DE4139367C2 - Process for the production of fine explosive grain and application of the process - Google Patents

Description

The invention relates to a new method for manufacturing places of fine explosive grain, like that Application of this manufacturing process to manufacture solid fuel (AGV) or gas generator mixture .

The fine grain production by mechanical comminution Change in mills, attritors, etc. Explosives are problematic in two ways dar,

• - because of their often high impact and Friction sensitivity and
• - because of the mechanical activation of Solids (energy accumulation) in Grinding process.

There is therefore considerable risk, particularly with dry grinding risk of spontaneous combustion due to impact or Frictional forces during the grinding process. For fabrics with a blow sensitivity <40 Nm (e.g. triaminoguanidine nitrate, TAGN: 4 Nm) is therefore unaffected by dry grinding things to refrain from.

Fine grain is, however, because of its high spec. Ober area to achieve a rapid burnup of the AGV needed, and especially for use as "pores filler in the coarse grain pile ". Coarse grain is common (Crystals) in its grain form (e.g. lamellas or Needles) little to hardly pourable. The grain has to be there ge to achieve better flowability ge be rounded, either by spherulitic crystals stallisation if the substance has this property sits, or by rounding in a milling process.

Fine grain is often used as a "filler for pore volume reduction of coarse-grained solids gene or the like, or another fixed comm component in pourable solid / binder systems tigt (rocket fuel, gas generators), whereby the Degree of filling and the burning properties of the AGV can be improved. The bulk density of a Solid mixture can be z. B. assuming a homogeneous ball packing (with narrow grain distribution only increase if coarse and fine grain in certain grain diameter ratios and Parts by weight are used, for. B. in bimodal Grain distribution.

The intimate contact in a particle pile (Ge mixed) necessarily increases the number of Contact points between the particles and thus that  Adhesion or agglomeration behavior of the festival substance, whereby the rheological properties in the Kneading / mixing process can be deteriorated. That is, of the maximum filler content of the solid / bindery stems - e.g. B. here the oxygen carrier TAGN - is limited by adhesive forces between the particles or a higher proportion of liquid binder is used All particles must be wetted. Both limits the possible specific energy content of the pourable AGV mixture.

An increase in the adhesion behavior of the particle particle mischs (deterioration in flowability) avoid using bimodal or multimodal Grain distributions with certain (void-filling) Grain diameters and corresponding quantity ratio sen. This ensures that the Particle mixtures achieved, with simultaneous optima Packing density. The internal friction in the solid / Binder system is divided into a large number of cones cycle points; this is the point pressure reduced (viscosity reduced). The physical chemical properties of a solid / binder However, they are also essentially of the type affects the pretreatment of the components, e.g. B. by mechanical activation in the grinding process, so probably material structure, like physico-chemical changes changes, but also chemical reactions. In or occur on solid substances during or after De formation, breakage and mechanical dispersion regulated states with different lifetimes on. Such processes, increasingly with inelastic Fabrics with decreasing grain size always have an effect an increase in free energy or enthalpy Solid particles (energy accumulation).  

High impact and impact loads, especially with Dry grinding z. B. in attritors or jet mills, but leads to severe structural destruction (amorphism tion).

DE 36 01 593 describes a method for wet grinding known from explosives. With this two-stage pro zeß is in a first phase a suspension of Explosives formed with water and in a second Phase using a colloid mill to destroy the explosives grind and then separated. The disadvantage here is it is a two-step process, d. H. there must be a separate premix and that with colloid mills basically the danger of so-called "creaming" exists. In colloid mills occurs especially with explosives unpleasant separation effect, namely a solid enrichment in the grinding tool (until it runs dry), because the suspension liquid runs through quickly. Colloid mills are therefore usually high Solids content (50% and more) driven; the regrind is just moistened, so to speak. Because of the very high Frictional heat during grinding can even localize the ground material "drying". Explosive / water mixtures are, however Flammable from 30% solids content, depending on friction temp sensitivity. Compliance with solids contents is below 30% when feeding colloid len not secured, not even by connecting upstream a stirred tank. From Römpp-Chemie-Lexikon, 9. Edition 1990, Vol. 3, pages 1845 and 8th edition, Vol. 6, page 4413 is known to have homogenization effects with fast running machines, e.g. B. by rotor Stator stirrers can be achieved.

Task of the present the invention is therefore a wet grinding process for To specify fine grain that does not require colloid mills,  the properties of the product, i.e. H. of the ge ground fine grain, at least with those of the colloid grinder must be comparable and use of this very fine grain in AGVs or gas generator fuel fen. The invention is characterized by the characteristics of procedural claims 1-3 and by the user claim 4 solved.

Surprisingly, it has now been found that wet grinding from Z. B. TAGN in inert or low solving rivers liquids such as B. trichlorethylene, 1,1,1-trichlor ethane, ethanol or water leads to a fine grain, that the expectations of workability and own properties of the AGV, such as high solids content in the solid / binder system with simultaneous casting ability of the kneading / mixing mass, high burn rate strength with good strength properties and high thermal stability of the propellant charge. The meal The course becomes when about 1/10 grain is reached diameter of the later AGV or gas generator Coarse grain used fuel. The Ex Plosivkornkorn is thereby caused by constant change zen crushed in a mixing vessel. The circulation can in Mixing vessel with high-performance agitators (rapid agitation rern) or by conveying in a circuit using In-Li ne dispersion chambers.

For the production of AGVs or gas generator fuels the fine grain thus ground with coarse grain in Ratio of 70% coarse grain to 30% fine grain mixed in kneading / mixed mass.

The following table are for better understanding the most important data of triaminoguanidine nitrate (TAGN) / Polyurethane (PU) propellants compared to  Ammonium nitrate (AN / PU) propellants compared poses.

Comparison of TAGN / PU and AN / PU propellants

TAGN / PU propellants are superior to AN / PU propellants due to higher burning rate, higher gas emissions loot, lower combustion temperature, higher che mixing and thermal stability (wide range of uses rich) particle-free and non-corrosive exhaust gas (non-toxic and environmentally friendly). TAGN / PU drift sentences also show low sensitivities (Sen sitivity against shock) and better mechanical egg properties like Doublebase-AGV.

TAGN propellants are also not sensitive to moisture (AN: hygroscopic!) And in a wide temperature range can be used, both at low and high levels exercise temperatures (phase change from AN to AN / PU-  DTS or cold brittleness of double base FTS ent falls).

According to the invention, z. B. with TAGN using a High-speed stirrer and an inert solvent Suspension created. The solids content (e.g. TAGN) in the grinding suspension should not exceed 20% stride. Advantageously, "single stage" worked, d. H. the suspension is produced and then the grinding process with the same stirrer continued.

Wet grinding is done "gently" (large Surface increase with little structural destruction), being an increase in the surface reactivity of the Particles due to pressure and shear stress in the meal operation occurs, which affects the training of Binder phases in the kneading / mixing and casting process cheap affects, but also on the mechanical strength of the finished AGV (no relaxing grid changes).

While colloid mills produce stable foams that practically no longer disintegrates, there is a foam effect with rapid stirrers. (In the "Meal gap "there is a significant pressure jump: Ultra sound).

Because in both cases work in a cycle must to achieve the desired degree of comminution The need arises for colloid mills degassing in an additional operation Vacuum degassing to the particle suspension (during of the grinding process). This does not apply for quick stirrers.  

Another advantage of high-performance grinding Stirrers appear when the ground material is separated from the suspension liquid. The solid settles out quickly, is therefore easy to filter, which is the case with "Foam" is not possible. Vacuum filtration (Ab suction) of the solid before drying is eliminated likewise, is even disadvantageous since it has been shown that this for strong agglomeration (caking) of the Grist leads, so that (after drying) again must be crushed.

The sedimented solid sludge is also favorable freeze and then dry (vacuum freeze-dry without thawing (sublimation drying). There through the regrind remains loose and fine, what the subsequent mixing and incorporation into a bin dermatrix relieved. After freeze-drying venting the mill base with dry nitrogen advantageous to avoid reagglomeration. To the rapid sublimation drying should not be under 13.3 Pa are evacuated or cyclically with dry Nitrogen is ventilated to transfer the heat to improve the heating plate / regrind (vacuum control tion between 13.3 Pa and about 1.3 · 10³ Pa by Ein conduct dry nitrogen).

The grinding process with high-speed stirrers can be done both in Batch operation (with stirring shaft and dispersing head) as in circulation mode (with inline dispersion chamber) the grinding suspension operated. The grain size decreases with increasing dispersion time. The Mahlergeb nis is comparable to grinding in colloid mill len, both in terms of grain size achieved (Grinding time) like efficiency.  

By wet grinding of explosive substances in liquid with a low solids content (e.g. <20%) will also self-ignite Impact or friction excluded.

High impact sensitive substances, such as. B. hexogen or PETN, but also TAGN, detonate in inert liquid only with solids contents above 20%, as they do e.g. B. are common in colloid mills or in Always have the same grinding gap. The wet grinding offers "in dilution" using high-performance stirrers therefore a significant security aspect.

The invention is illustrated by the following examples explained.

example 1

3-3.5 kg of coarsely crystalline TAGN (d₅₀ ≈ 150 µm) were stirred in 20 l of 1,1,1-trichlorethylene with a high-speed stirrer (10,500 rpm).
Final grain size: d₅₀ ≈ 15 µm.

Example 2

Approx. 3 kg of coarsely crystalline TAGN were ground in 20 l of ethanol using a high-speed stirrer and dispersing head as before 2 hours.
Final grain size: d₅₀ ≈ 15 µm.

Example 3

Approx. 3 kg of octogen, coarse (d₅₀ ≈ 280 µm) were ground in 20 l of water using a high-speed stirrer and dispersing head as before 2 h.
Final grain size: d₅₀ ≈ 18 µm.

Claims (4)

1. A process for the production of fine explosive grain by wet grinding in a one-step process, wherein a suspension of the explosive grain is produced with an inert or low-solvent, the explosive grain is broken up by circulating in the stirring vessel by means of a high-speed stirrer and the inert solvent is separated off , and characterized in that the solids content in the grinding suspension does not exceed 20%, and in that the grinding process is terminated when approximately 1/10 grain diameter of the coarse grain used in the later solid fuel (AGV) or gas generator mixture is ended. 2. The method according to claim 1, characterized in that as an inert solution medium chlorinated hydrocarbons or low Some alcohols, preferably ethanol, or water are used becomes. 3. The method according to claim 1 or 2, characterized in that as a solid Hexo gen, octogen, triaminoguanidine nitrate (TAGN) or Pentaerythritol nitrate (PETN) is used.   4. Application of the method after at least one of claims 1 to 3, characterized in that coarse grain with the ground, dried fine grain in the ratio 70: 30 in the solid binder system in one Kneading / mixing process is mixed.