GB2272693A

GB2272693A - Binder for propellant bodies

Info

Publication number: GB2272693A
Application number: GB8904060A
Authority: GB
Inventors: Dieter Girke; Hans Peter Hebekeuser; Franz-Willi Herkenrath; Hans Peter Mackowiak
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1988-03-19
Filing date: 1989-02-22
Publication date: 1994-05-25
Anticipated expiration: 2009-02-22
Also published as: GB8904060D0; FR2697833B1; GB2272693B; DE3809297C1; FR2697833A1

Description

1 .ol 2272693 BINDER FOR PROPELLENT BODIES The subject of the present

invention is the use of a cross-linkable mixture of a) hydroxyl group-containing polymers and b) polymers based on 1,3butadiene with succinic acid anhydride groups laterally attached thereto as binder tor the production of propellent bodies which are formed from crystalline explosives.

It is known to produce bound propellent bodies f rom crystalline explosives by mixing the crystalline explosives with a binder consisting of a prepolymer with functional groups and with a di- or polyisocyanate and bringing the mixture obtained into the desired shape with the assistance of known processes. e.g., pressing into a container, extruding or with the aid of casting apparatus.

The many dicomponents MAK-values disadvantage of this known process are that or polyisocyanates employable as binder are toxic and therefore possess relatively low Furthermore, as a consequence of their reactivity, they are unspecific reaction partners which enter, in part, into undesired disturbing side reactions with other components such as au-xiliary substances and additives as well as with traces of water from atmospheric moisture, with splitting off of carbon dioxide. As a consequence. an undesired porosity occurs in the propellent bodies then obtained which has an undesirable effect on the internal ballistics of the body.

Furthermore, many binder mixtures based on 35 isocyanate have the disadvantage that they possess a relatively high vapour pressure and accordingly a high volatility. When they are worked up into shaped bodies, 5j., 1 which is carried out generally under vacuum or at temperatures above about 30 0 C, undesired void formation readi ly takes place in these shaped bodies; these voids prevent a regular combustion of such a propellent body.

There therefore existed the object of discovering a binder system whose components do not enter - into any gas forming reactions with atmospheric moisture before and during the hardening and which do not form with the constituents of the propellent body, as much as possible, JO any by-products or only form those by-products which are inert with respect to the propellent bodies and do not lead to any negative influencing of the propellent components.

Also, the binder should possess as low a vapour 1-5 pressure as possible particularly under the usual working conditions in the production of propellant bodies - in order that the aforementioned disadvantages attributable to the high volatility of the isocyanates do not occur.

It has now been found, in fulfilment of this object, that a mixture of hydroxyl group-containing polymer and polymer based on 1,3-butadiene with succinic acid anhydride groups laterally attached thereto may be used as binder for propellent bodies based on crystalline explosive substances.

The hydroxyl group containing polymer has in general an average numerical molecular weight between 1,000 and 10,000 and a hydroxyl number between 5 and 200 Img KOH/g]. It reacts with the polymer based on 1,3-butadiene with succinic acid anhydride groups laterally attached thereto to form cross-linked polymers and can therefore also be denoted as prepolymer in the mixture. It is liquid at room temperature. The preferred hydroxyl group-containing polymer is a hydroxyl group-containing polybutadiene. Such compounds are known per se; their production is described for example in DE-A- 34 36 556.The hydroxyl groups can accordingly be i 1; 5.,primary or secondary in the polymers and also can be arranged at the respective chain ends. It is also possible that these hydroxyL groups be connected with the chain via methyL groups. Such hydroxymethyL group-carrying polymers are furthermore preferred as component a) of the required mixture.

However, also, other hydroxyL group containing polymers which are Liquid at room temperature can be used as component a). As examples there may be named:

polyethylene gLycoLs,, polypropylene glycols, polyesters or poLyetheraLcohoLs.

The second known constituent of the binder mixture employed according to the invention is a polymer based on 1.3-butadiene with Laterally attached succinic acid anhydride groups. Such polymers are likewise known per se; they are also designated as maleinised butadiene polymers. Their production takes place as a rule by addition of maleic acid anhydride to a polymer based on 1,3- butadiene (see also DE-Al-54 36 556). Reaction takes place, as already stated. with the group-containing polymers with molecular comt)ounds.

hydroxyl cross-linking to high This polymer is therefore also designated in the following as cross- linker.

The cross-linking reaction takes place between the anhydride groups of this cross-linker and the OH groups of the hydroxyl group containing polymer. If a complete cross-linking between the prepolymer and the cross-linker is desired, the ratio of these groupings in the mixture being employed should lie in the stoichiometric range.

It is however also possible to employ such amounts of the cross-linker which lie below the stoichiometric ratio for adjustment of specific properties of the cross-linked mixture.

The propellent crystalline explosive system to be bound encompasses substancesp e.g. nitramines, aromatic or aliphatic nitro compounds or amino-nitro compounds, whose employment in propellent bodies is known _ A-- is 1 per se. Their proportion in bound propellent bodies lies between 70 and 95% by weight, preferably between 80 and 90% by weight.

The propellent mixture encompasses furthermore the additivies known in propellent mixtures. Combustion moderators, emulsifiers and lubricants belong -to these additives. The type and amount of these additives depends on the chosen propellant; the substances to be employed are known to the man skilled in the art. In 1 () general, the amount ot these additives lies between 0.1 and 2.0% by weight related to the propellent system.

The mixture of propellent components and binder system can be stored for a long time in the uncross-linked state without negative influences occurring. In contrast to known systems, such a system does not shrink on storage and can also be hardened to the solid propellent bodies after a longer storage time without these having the previously indicated disadvantages of known propellent bodies.

The production of the mixture of propellent components and the binder system takes place in a manner known per se. All components can be mixed together; the mixture obtained is worked into shaped bodies of desired dimensions and then hardened by temperature treatment.

The above-indicated cross-linking takes place during this hardening. The hardening temperature depends on the chosen binder system; in general it lies above 35 0 C. The upper limit ot the hardening temperature should clearly lie below the detonation or decomposition temperature of the explosive mixture of the propellent charge powder.

Propellant charge bodies which are bound with the aid of the mixture according to the invention contain the individual propellent particles homogeneously distributed in the mixture. The bodies obtained do not contain any air bubbles or voids as occur in the hitherto known propellent bodies, which are bound with the aid of isocyanates. Also, the bodies burn away uniformly.

--5-- The propellent bodies which are produced with the aid of the claimed binder system are preferably employed as gas supplying components for ammunition, in particular for large calibre ammunition.

ExamDle 1. 9.0 parts by weight of an OH-group-containing polybutadiene 6.3 parts by weight of maleinised polybutadiene 84 parts by weight of hexogen M parts by weight of additives were mixed. The mixture was kneaded for 30 minutes at room temperature and then compressed into strips. These strips were hardened at 35 0 C and cut into propellent bodies.

The bodies are elastic even at temperatures to -400C and do not show any brittleness; they do not soften and they retain their weight at temperatures up to about 100 0 C. A loss in weight accordingly does not occur. The combustion behaviour corresponds to that of known 20 propellent bodies.

2. The procedure of Example 1 was repeated. The components employed were the same. merely the weight ratio was changed as follows:

13.4 parts by weight of prepolymer 9.5 parts by weight of cross-linker 75.0 parts by weight of hexogen 2.1 parts by weight of additives.

The additives contained, as well as the emulsifiers and lubricants employed in Example 10 30 combustion moderators in addition.

The mixture obtained was cast into shaped bodies and hardened at 400C. The properties of the propellent bodies obtained corresponded to those of Example 1.

1 CLains:

1. Use of a cross-LinkabLe mixture of a) hydroxyL group-containing poLymer and b) a poLymer based on 1,3-butadiene with succinic acid anhydride groups LateraLLy attached, as binder for propeLLent bodies based on crystaLLine expLosives.

2. Use of a cross-LinkabLe mixture according to cLaim 1, in which the cross-Linking takes pLace in the absence of cross- Linking cataLysts by heating to temperatures above 350C.

3. Use of a cross-LinkabLe mixture according to cLaim 1 and 2, in whicF, those 1,3-butadiene based hydroxyL group containing poLymers are used which contain primary and/or secondary hydroxyL groups and possess a hydroxyL number of 5 to 200 [mg KOH/g3.

X Amendments to the claims have been filed as follows 1. A process for the production of a crystalline high explosive-based propellant body which comprises forming a mixture of cross-linkable binder composition comprising a) a hydroxyl group-containing polymer and b) a polymer based on 1,3-butadiene with succinic acid anhydride groups laterally attached, with one or more crystalline high explosive substances, shaping the mixture and effecting cross-linking of the binder at a temperature above the ambient temperature.

2. A process according to claim 1, in which the cross-linking takes place in the absence of crosslinking catalysts by heating to a temperature above 350C.

3. A process according to claim 1 or 2, in which the hydroxyl-containing polymer is a 1,3-butadiene based polymer which contains primary and/or secondary hydroxyl groups and possesses a hydroxyl number of 5 to 200 [mg KOH/g].

4. A process as claimed in any preceding claim, wherein the hydroxyl groups are contained in hydroxymethyl groups.

5. A process as claimed in any preceding claim, wherein the crystalline high explosive substance(s) constitute(s) between 70 and 95% by weight of the propellant body obtained.

6. A process as claimed in any preceding claims, wherein the crystalline high explosive substance(s) is/are selected from nitramines, aromatic or aliphatic nitro compounds and amino-nitro compounds.

7. A process for the production of a crystalline high explosive-based propellant body, substantially as described in either of the foregoing examples.

I- g-

Claims

8. A crystalline high explosive-based propellant body, whenever produced

by the process claimed in any one of Claims 1 to 7.

p