DE2737699C3 - Process for modifying the burning behavior of nitrocellulose-containing solid propellants by chemically modifying the nitrocellulose component and using the nitrocellulose produced in this way - Google Patents

Description

The invention relates to a method for modifying the burning behavior of nitrocellulose containing Solid propellants through chemical modification of the nitrocellulose-Kompoiiente and the use in particular as components of gas-generating systems that regulate the rate of combustion for solid propellants and pyrotechnic charges.

Nitrocellulose is a major component of many solid rocket propellants, Gun propellants, solid propellants for inflators and pyrotechnic charges. In Double-base solid propellants (DB-FTS) are nitroglycerine, plasticizers and stabilizers. In addition, there are composite double bases - solid propellants (CDB-FTS) nor binder components such as polyurethanes or polybutadienes and inorganic or organic oxidizers such as z. B. ammonium perchlorate or hexogen. In CDB-FTS, NC is often in the form of colloidal NC with a average grain diameter of S 50 mm incorporated. Gas generators, gun propellants and pyrotechnic Sentences often have analogous compositions.

The burning rate of such systems increases monotonically with increasing pressure. The reduction (Plateau effect) or the interruption (mesa effect) of this monotonous rise is from internal ballistic and for safety reasons desirable. Plateau or mesa effect can be achieved by the Use of Abbrandniodifikatoren with a weight fraction of up to about 5% can be achieved. this applies only if the burn-up modifier is finely distributed and brought into close contact with the NC that it contains can be. For DB-AGVs and systems of the appropriate composition, this has so far been achieved by that the components including the burn-off modifiers are kneaded and added according to the known method Fuels are processed. The demolition modifier lowers the explosion heat of the fuel and with it its performance. For solid propellants made using Colloidal NC with a mean grain diameter of S50 mm to be cast according to the slurry process is by adding of modifiers of the plateau or mesa effect far less pronounced. Since the colloidal NC with a medium grain diameter knife of i50mm from one Solvent / water emulsions are precipitated, they cannot contain any modifiers. The addition of

ίο Modifiers therefore only take place during the slurry casting process, however, as a result, the desirable high degree of distribution cannot be achieved.

The invention has for its object to find a method that a modification of the

¹ S The burning behavior of solid propellants containing nitrocellulose and similar systems is guaranteed regardless of the processing of the components.

This object is achieved according to the invention by the method specified in the characterizing part of claim 1 solved. Further advantageous changes to the method are specified in the dependent claims 2 and 3 as well Possible applications in claims 4 and 5.

The invention relates to a method for chemical modification of the NC, the catalyst chemically binds in finely divided form to the NC chain molecules and the difficulties mentioned eliminated. The modified NC is obtained in a form that can be processed in all applications in the field of gas generating systems enables.

The following examples may illustrate the invention:

Description of the procedure

The starting point for chemical reactions on the nitrocellulose molecule are those caused by unvoiced ones Nitration of existing hydroxyl groups. A nitrocellulose (NC) with a nitrogen content of 13.3% still contains 10% of the hydroxyl groups that were present before the cellulose was nitrated.

This invention relates to methods that activate these alcoholic hydroxyl groups, the otherwise show little tendency towards chemical interaction with heavy metal ions of typical combustion modifiers enter into.

This activation is achieved through reactions through which the alcoholic hydroxyl groups are converted. In principle, this can be done by all halocarboxylic acids, the halogen atoms of which react with the hydrogen atoms of the alcoholic hydroxyl groups of NC with elimination of hydrogen halide under suitable reaction conditions. Suitable carboxylating agents are halogen monocarboxylic acids with λ-, central or terminal halogen atoms such as. B. λ-, β- or y-chlorobutyric acid, ω-chlorocaproic acid, chloroacetic acid and others, but also halodicarboxylic acids such. B. chloromalonic acid, chlorosuccinic acid, chloradipic acids and others, as well as polybasic halocarboxylic acids. These halocarboxylic acids can also belong to the acyclic, heterocyclic or aromatic series.

After the carboxylation has taken place, heavy metal salts that modify the burn are absorbed onto the NC fiber, by entering into a chemical bond with this, so that under suitable conditions a molecular-fine and thus highly effective distribution of burn-up modifiers is made possible. Other advantages of this Method consist in that the chemically to the

Burn modifiers bound to NC fibers are no longer washed out during processing and Even under the toughest long-term storage conditions, they no longer migrate from the finished propellants can. Propellant charges that receive NC remunerated according to this process therefore retain their ballistic properties Properties even under extreme operating conditions.

The anchoring of the erosion modifiers to the carboxyl groups according to this process is chemical Modified NC can be used both in a heterogeneous (see example 1) and in a homogeneous reaction (see Example 2) happen.

example 1

For the carboxymethylation, 100 g of NC with a nitrogen content of 13.3% are dissolved in 2 l of acetone, mixed with an excess of 40 g (120 mol%) of crystallized monochloroacetic acid in acetone solution and Stirred for 4 to 8 hours at 30 to 45 ° C. The reaction temperature can also be up to the reflux temperature can be increased.

The reaction mixture is then slowly poured into about 10 times the amount of water in a fine stream and the reaction product which precipitates out is finely divided by vigorous stirring using a Turrax stirrer. After filtration, the precipitate was taken up in a lot of water and ^{stirred at 100 °} C. for 6 hours. What washing water was renewed twice.

To anchor the erosion modifiers, the carboxymethylated NC is slurried in water and with a water-soluble copper (M) or lead (II) salt, z. B. the heavy metal acetate, stirred in excess for 4 to 8 hours at room temperature. Then it will be like that Washed for a long time until no more heavy metal ions can be detected in the filtrate. With the scanning electron microscope with X-ray fluorescence additive elementary division images show that so ever depending on the nitrogen content of the NC used and depending on the carboxylating agent and conditions used 0.5 to 7% by weight of heavy metal are homogeneously distributed on the NC fiber.

If NC is used for the reaction with the heavy metal salts, not before after this Process was carboxylated, sis emerges unchanged from it, i. H. it is then no copper or Analytically detectable lead.

Example 2

Carboxylation as in Example 1, but without precipitation. The acetone solution obtained in this way carboxylated NC is mixed with an acetone solution of an acetone-soluble heavy metal salt in an appropriate amount, e.g. B. 42 g of (CH ₃ COO) ₂ Cu · H ₂ O are added and the mixture is stirred at 35 to 45 ° C. for 4 to 8 hours. Then isolation as in example 1.

The DB-FTS produced according to the invention clearly showed the intended effect of a modified one Dependence of the burning rate on the pressure. It also saw a significant increase in Explosive heat compared to DB-FTS are recorded, which are chemically with the same composition unchanged NC contained. In some cases, a better plasticization behavior could also be observed, so that the amount of plasticizer that would impair the oxygen balance could be saved. Further Properties such as chemical stability and mechanical strength came together in one for DB-AGVs usual framework.

Claims (5)

Patent claims: 1. Procedure for modifying the combustion behavior of solid propellants containing nitrocellulose by chemical modification of the nitrocellulose component characterized in that residual hydroxyl groups of nitrocelluloses various degrees of nitration with halocarboxylic acids with elimination of hydrogen halide are reacted and burn-mod'fizierende heavy metal ions to the carboxyl groups are chemically bound. 2. The method according to claim 1, characterized in that halogen monocarboxylic acids are used as halocarboxylic acids uses v / earth. 3. The method according to claim 1, characterized in that to increase the carboxyl content of the nitrocelluloses polybasic halocarboxylic acids can be used. 4. Use of the nitrocellulose obtained according to claim 1 and 2 for the production of Powder granulate. 5. Use of the nitrocellulose produced according to claim 1 to 3 as a component in Solid rocket propellants, cannon propellants, solid gas generator propellants, or pyrotechnic Sentences.