DE2737699A1 - Chemical modification of nitrocellulose for solid propellants - to improve action of burn rate regulators - Google Patents

Abstract

Nitrocellulose for use in solid propellants is modified by reacting the free OH gps. with halogen-carboxylic acids with splitting of hydrogen halide. Usual heavy metal ions for modifying the burn rate of the propellant are then chemically attached to the COOH gps. in the modified nitrocellulose. The OH gps. which otherwise show little tendency to react with the heavy metal ions, are activated and allow the metal ions to be chemically bonded, preventing washing-out or migration during storage. Dispersion of the burn modifiers is improved, and the propellants retain their ballistic properties under extreme service conditions. Used in solid rocket fuels, tube weapon and gas generator propellants and pyrotechnic charges.

Description

Process for modifying the combustion behavior of nitro

solid propellants containing cellulose by chemical modification of the nitrocellulose component. The invention relates to a method for modification the burning behavior of nitrocellulose-containing solid propellants by chemical Modification of the nitrocelulose component and the use of it to regulate the burning rate Part of gas generating systems, especially for solid propellants and pyrotechnic Sentences.

Nitrocellulose is a major component of many solid rocket propellants, Gun propellants, solid propellants and pyrotechnic charges. In Double-base solid propellants (DB-FTS) are nitroglycerin, plasticizers and stabilizers further components. In addition, there are composite double-base solid abrasives (CDB-FTS) nor binder components such as polyurothanes or polybutadienes and inorganic or organic Oxidizers such as ammonium perchlorate or hexogen. In CDB-FTS, NC is often in Form of fluid ball incorporated. Gas generators, gun propellants and pyrotechnic Sentences often have analogous compositions.

The burning rate of such a system increases with increasing Print monotonously. The reduction (plateau effect) or the interruption (mesa effect) this monotonous increase is due to internal ballistic and safety aspects Reasons desirable. Plateau or mesa affect can be achieved through the use of burn-off modifiers can be achieved with a weight fraction of up to about 5%. This only applies if the erosion modifier finely distributed in close contact with the proportionately contained NC can be brought. For DB AGVs and systems of the appropriate composition this is so far achieved in that the component including Combustion modifiers are kneaded and made into fuels according to the procedures below are further processed. The combustion modifier lowers the heat of the explosion of the fuel and thus its performance, In the case of solid fuels that are using of NC fluid balls using the slurry method. is durob addition of Modifiers of the plateau or. Mesa effect far less pronounced. Since the Fluidballs are precipitated from a solvent / water emulsion, no modifiers can do this contain. Modifiers are therefore only added during the slurry casting process, as a result, however, the desirable high degree of distribution cannot be achieved.

The invention is based on the object of finding a method as a modification of the combustion behavior of solid propellants containing nitrocellulose and similar systems regardless of the processing of the components.

This object is achieved according to the invention by the claims in the identification code 1 specified procedure solved. Further beneficial.

Process changes are specified in subclaims 2 and 3 and possible applications in claims 4 and 5.

The invention relates to a method for chemical modification the NC, which chemically attaches the catalyst in finely divided form to the NC chain molecules binds and eliminates the difficulties mentioned. The modified NC is in a poru that has a processing in all use cases in the field of the generating systems.

The following examples may illustrate the invention: Description of the process As a starting point for chemical reactions on the nitrocellulose molecule serve the hydroxyl groups present due to incomplete nitration. A nitrocellulose (NC) with a nitrogen content of 13.3% still contains 10% of the hydroxyl groups, the were present prior to the nitration of the cellulose.

This invention relates to methods which alcoholisohen these Activate hydroxyl groups, which otherwise show little tendency, with heavy metal ions typical erosion modifiers to enter into chemical interaction.

This activation is achieved through reactions through which the alcoholic Hydroxyl groups are converted. In principle, all halocarboxylic acids can do this done, their halogen atoms with the hydrogen atoms of the alcoholic hydroxyl groups of NC react with elimination of hydrogen halide under suitable reaction conditions. Suitable carboxylating agents are halogen monocarboxylic acids with α, medium or terminal halogen atoms such as α -, ß - or γ -chlorobutyric acid, # -Chlorcaproic acid, chloroacetic acid and others, but also halodicarboxylic acids such as e.g. chloromalonic acid, chlorosuccinic acid, chloradipic acids and others as well as polybasic ones Halogenoarboxylic acids. These halocarboxylic acids can also be alicyclic or heterocyclic or aromatic series.

After the carboxylation has taken place, burn-off-modifying heavy metal salts appear on the NC fiber by forming a chemical bond with it so that under common conditions a molecular-fine and thus highly effective distribution is made possible by burn-up modifiers. There are other advantages of this procedure in that the burn modifiers chemically bonded to the NC fiber in the processing can no longer be washed out and even under the toughest long-term storage conditions can no longer emigrate from the finished propellants. Propellant charges, which after these procedures contain compensated yes, therefore retain their ballistic properties even under extreme operating conditions.

The anchoring of the burn-off modifiers to the carboxyl groups of the According to this procedure, chemically modified NC can be used in heterogeneous (see example 1) as well as in a homogeneous reaction (see Example 2).

Example 1 For the carboxymethylation, 100 g of NC with a nitrogen content are used of 13.3% dissolved in 2 l of acetone, crystallized with an excess of 40 g (120 mol%) Monochloroacetic acid in acetone solution and 4 to 8 hours at 30 to 4500 touched. The reaction temperature can also be increased to the reflux temperature will.

The reaction mixture is then poured into the approx. 10 times the amount of water entered slowly and stirred vigorously by means of a Turrar stirrer ensures that the reaction product which precipitates is finely divided will. After filtration, the precipitate would be taken up in a lot of water and dried for 6 hours. stirred for a long time at 100 ° C. The Wasxhwasser would be renewed twice more.

The carboxymethylated is used to anchor the burn-off indicators NC slurried in water and coated with a water-soluble copper (II) or lead (II) sals, e.g. heavy stable acetate, stirred in excess for 4 to 8 hours at room temperature. It is then washed until there are no heavy metal ions in the filtrate have more to prove. With the scanning electron microscope with X-ray fluorescence add-on recorded Klementverteilungsbilder show that depending on the nitrogen content of the NC used and, depending on the carboxylating agent and conditions used, 0.5 up to 7 wt .-% heavy metal are homogeneously distributed on the NC fiber.

When NC is used for the reaction with the heavy metal salts, which was not previously carboxylated by this process goes unchanged again from this, i.e. no copper or lead can then be analytically proven.

Example 2: Carboxylation as in Example 1, but without precipitation. The 50 obtained acetone solution of carboxylated NC is with an acetone solution of an amount corresponding to an acetone-soluble heavy metal salt; e.g. of 42 g (CH3COO) 2Cu.H2O offset and 4 to 8 hours

stirred for a long time at 35 to 450C. Then insulation as in the example 1.

The DB-FTS produced according to the invention clearly showed the intended one Effect of a modified dependence of the burning rate on the pressure In addition, there was a significant increase in explosion heat compared to DB-FTS which contained chemically unchanged NC with the same composition. Partly a better plasticization behavior could also be observed, so that the oxygen balance harmful plasticizer components could be saved. Other properties such as chemical stability and mechanical strength, moved in one for DB-FTS usual framework.

Claims (5)

P a t e n t a n s p r ü c h e 1. Procedure for modifying the Burning off of nitrocellulose-containing solid propellants by chemical means Modification of nitrocellulose components t that residual hydroxyl groups of nitrocelluloses of various degrees of nitration brought to reaction with halocarboxylic acid with elimination of hydrogen halide and heavy metal ions that burn-up on the carboxyl groups are obemic be bound. 2. The method according to claim 1, d a d u r c h g e k e n n z e i c h n e t that halogen monocarboxylic acids are used as halocarboxylic acids. 3. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that to increase the carboxyl content of the nitrocelluloses polybasic halocarboxylic acids be used. en 4. Use of the / nitrocellulose obtained according to claims 1 and 2 for the production of powder granules such as so-called fluid balls or basegrain powders. 5. Use of the nitrocellulose produced according to claims 1 to 3 as a component in solid rocket propellants, gun propellants, solid propellants for gas generators or pyrotechnic charges.