FR2697833A1 - Binding agent for propellant charge. - Google Patents

Abstract

The present invention relates to a new system of binding agents for propellant charges based on crystalline explosive. The binder mixture comprises a mixture of polymers containing hydroxyl groups and polybutadiene-based polymers which have pendant succinic acid anhydride groups. These binding agent systems are known per se; they cure without the addition of catalyst at an elevated temperature. The explosive charges that are prepared with this binding agent system are pore-free, void-free and burn evenly. Their mechanical properties correspond to those of explosive charges. They are also elastic at a temperature of -40degree C do not show breakage and do not soften on annealing up to a temperature of 100deg C.

Description

BINDING AGENT FOR PROPULSIVE CHARGE.

  The present invention consists of the use of a crosslinkable mixture comprising a) polymers containing hydroxyl groups and b) polymers based on 1,3-butadiene comprising pendant groups of succinic acid anhydride as d binding agent for the preparation of propellant charges

  base of explosive crystalline bodies.

  It is known to prepare propellant charges based on crystalline explosive bodies linked by mixing a crystalline explosive body with a binding agent comprising a prepolymer with functional groups and a di or polyisocyanate The mixture obtained is transformed to obtain the desired shape at by means of known methods such as for example pot pressing, extrusion or

by means of casting devices.

  The drawbacks of these known methods reside in the fact that many components which can be used as binders such as di or polyisocyanates are toxic and therefore have relatively low MAM values. Furthermore, due to their reactivity, they are reaction partners. nonspecific which partially cause undesired disturbing side reactions with other components such as for example with additives or ingredients, as in the presence of trace, of water coming from the humidity of the air, by cutting of dioxide of carbon It is created in propellant charges, an unwanted porosity which acts

  negatively on the internal ballistics of the load.

  Furthermore, many isocyanate-based binder mixtures have the disadvantage that they have a relatively high vapor pressure and therefore high volatility When used for the production of fillers which are generally carried out under vacuum at temperatures above 30 'C, voids are easily produced in these forms These voids or recesses

  prevent regular combustion of such a propellant charge.

  There was therefore the problem of finding a binder system whose components have no reaction forming gases, before and during the curing with the humidity of the air and that therefore the constituents of the propellant charge If possible, form none or only secondary products which are inert to the propellant charge and which have no negative influence on the components of the propellant charge. Furthermore, the binder must also have a low vapor pressure if possible. particular under the conditions of usual preparation of propellant charges, that it does not therefore have the disadvantages of

  the high volatility of isocyanates.

  This problem has been resolved by the use of a mixture of polymers containing hydroxyl groups and of polymers based on 1,3butadiene comprising pendant groups of succinic acid anhydride, as binding agent for fillers.

  propellants in crystalline explosive bodies.

  The polymers containing a hydroxyl group have on average an average molecular weight of between 1,000 and 10,000 and a hydroxyl content of between 5 and 200 (mg KOH / g) The polymer reacts with polymers based on 1,3-butadiene and comprising pendant succinic acid anhydride groups to form crosslinked polymers, can therefore also be considered as a prepolymer in the mixture This polymer is liquid at room temperature The preferred polymer comprising the hydroxyl groups is a polybutadiene comprising hydroxyl groups Such compounds are known per se; the preparation is for example described in DE-OS 34 36 556. The hydroxyl groups of the polymer can be primary or secondary and can also appear at the ends of the chains. It is also possible that these hydroxyl groups are linked via methyl groups to the chain Such polymers comprising hydroxymethyl groups are preferred as components a) of the

mixture claimed.

  As component a) of the mixture intended to be used, it is also possible to use other polymers containing hydroxyl groups which are liquid at room temperature.

  By way of example, mention may be made of polyethylene glycol, polypropylene-

  glycol, polyester or polyether alcohol.

  The second constituent of the binder mixture used in accordance with the invention is a 1,3-butadiene-based polymer comprising succinic anhydride groups during These polymers are also known in themselves; they are classified as maleic butadiene polymers Their preparation generally consists in condensing maleic anhydride on a polymer based on 1,3-butadiene (see in particular DE-AI-34 36 556) It reacts as already indicated with polymers containing hydroxyl groups by crosslinking in high molecular weight products This polymer

  is also referred to hereinafter as "crosslinking agent".

  The crosslinking reaction is carried out between the anhydride groups of this crosslinking agent and the OH groups of the polymer containing the hydroxyl groups. When a total crosslinking between the prepolymer and the crosslinking agent is desired, the mixture used according to the invention the ratio between the different groups must be stoichiometric. If certain particular characteristics of the crosslinked mixture are desired, it is also possible to use amounts of crosslinking agents which

  are less than the stoichiometric ratio.

  The propellant system intended to be linked comprises crystalline explosive bodies for example nitramine, aromatic or aliphatic nitro derivatives or nitro amino derivatives of which

  the introduction into propellant charges is known in itself.

  Their proportion in the propellant charge is between 70 and

  % by weight and preferably between 80 and 90% by weight.

  The propellant mixture also includes the additives known in propellant systems. Among these additives, mention may be made of residue moderators, emulsifying agents, lubricating agents. The form and the quantities of these additives depend on the particular propellant. to be introduced are known to those skilled in the art. In general, the amount of these additives is between 0.1 and 2% relative to the total weight of the propellant system. The mixture of propellant component and of binding agent can be stored under the non-crosslinked form for a longer period of time without negative influences. Unlike known systems, there is no shrinkage of these systems during storage and can be used with a longer storage period to form solid propellant charges without having the aforementioned disadvantages of charges

known propellants.

  The preparation of the mixture of the components of the propellant charge and of the binding system is carried out in a manner known per se. All the components can be mixed simultaneously together; the mixture obtained is transformed in the molded bodies to the desired dimensions and then hardened by heat treatment. During this hardening, the crosslinking mentioned above occurs. The hardening temperature depends on the system of binding agent; and is generally above 350 C. The upper limit of the hardening temperature must be significantly below the volatilization or transformation temperature of the mixture

explosive propellant.

  The propellant charges which are linked by the mixture according to the invention contain grains of individual propellant charges distributed homogeneously in the mixture. The bodies thus obtained do not contain air bubbles or vacuum, as was the case until present in the propellant charges linked by

  isocyanates These bodies also burn regularly.

  The propellant charges which are prepared with the binder system according to the invention are preferably used as a component providing gas for the munitions in particular

  for large caliber ammunition.

EXAMPLES

  1 Was mixed: 9.0 parts by weight of a polybutadiene containing OH groups 6.3 parts by weight of a maleinic polybutadiene 84.0 parts by weight of Hexogen

0.7 part by weight of additive.

  The mixture was kneaded at room temperature and pressed into cords. These cords were hardened at 35 ° C. and cut into propellant charges. The bodies are elastic up to -40 C and do not represent breakage. For annealing up to 100 C, they do not soften and keep their weight. There is no loss of weight.

  to residues corresponds to known propellant charges.

  2 The preparation method described in Example 1 was repeated.

  The components used were the same, the percentages by weight were modified as follows: Pre-polymer: 13.4 parts by weight Crosslinking agent: 9.5 parts by weight Hexogen: 75.0 parts by weight

Additive: 2.1 parts by weight.

  The additive also included emulsifiers and

  lubricants provided in Example 1 a residue moderator.

  The mixture thus obtained was poured and hardened at 40 ° C. The propellant charge properties correspond to those of Example 1.

Claims (3)

  1 Use of a crosslinkable mixture comprising a) a polymer containing hydroxyl groups and b) a 1,3-butadiene based polymer containing pendant succinic acid anhydride groups as binding agents for propellant charges based explosive crystal.   2 Use of the crosslinkable mixture according to claim 1 in which the crosslinking is carried out in the absence of a catalyst   of crosslinking, by heating to a temperature above 35 C.   3 Use of the crosslinkable mixture according to claim 1 or 2 in which, as the polymer containing hydroxyl groups, polymers based on 1,3-butadiene which contain primary and / or secondary hydroxyl groups are used and   with a hydroxyl value of 5 to 200 (mg KOH / g).