Methods for preparing age-stabilized propellant compositions

• US 6,059,906 A
• Filed: 12/19/1997
• Issued: 05/09/2000
• Est. Priority Date: 01/19/1994
• Status: Expired due to Term

• Current Assignee: Goodrich Corporation (Rtx Corporation)
• Original Assignee: Universal Propulsion Company Incorporated (Rtx Corporation)
• Inventors: Olander, Donald E., McSpadden, Hugh J., Fleming, Wayne C.
• Primary Examiner(s): Miller, Edward A.
• Application Number:
  US08/994,983
• Time in Patent Office: 872 Days
• Field of Search: 149/19.92, 149/46, 149/109.6
• US Class Current: 149/19.92
• CPC Class Codes: C06B 23/006 Stabilisers (e.g. thermal stabilisers) processes C06B21/0091; foam stabilisers C06B23/002
• CPC Class Codes: C06B 31/28 the salt being ammonium nitrate
• CPC Class Codes: C06B 31/30 with vegetable matter; with resin; with rubber
• CPC Class Codes: C06B 45/105 The resin being a polymer bearing energetic groups or containing a soluble organic explosive

Abstract

The present invention is directed to an age-stabilized and/or strengthened ammonium nitrate propellant composition wherein the strengthening agent is selected from the group consisting of azodicarbonamide, dicyandiamide, oxamide and mixtures thereof and wherein the age-stabilizing agent is a molecular sieve having a pore size of 13 angstroms or less.

Claims

1. A process of forming an age-stabilized propellant composition, said process consisting essentially of the steps of:

providing a quantity of ammonium nitrate;

mixing an amount of synthetic zeolite having pores sized and adapted to absorb water with said ammonium nitrate to form a first mixture;

aging said first mixture for a first aging period, wherein the first aging period is less than about 48 hours;

grinding said first mixture to yield a second mixture so as to increase the absorbability and retention of water in the pores of the synthetic zeolite; and

adding a binder with the second mixture to form a propellant composition, said binder being added in a sufficient amount to permit formation of said propellant composition into a desired shape, wherein said propellant composition is substantially smoke-free upon combustion.

2. The process of claim 1 wherein said first aging period is selected to be from about 0.25 to 48 hours.

3. The process of claim 1 further comprising selecting the synthetic zeolite to have a pore size of between about 3 angstroms to 13 angstroms and providing the synthetic zeolite in an amount from about 0.2 to 6 weight percent of the propellant composition.

4. The process of claim 3 wherein said combining step further comprises adding at least one of a material selected from the group consisting of strengthening agents, nitroplasticizers, energetic additives, nitrate ester stabilizers, opacifiers, cure catalysts, and antioxidants to the combination of said second mixture and the binder to yield the propellant composition.

5. The process of claim 4 further comprising

aging the propellant composition for a second aging period, wherein the second period is from about 0.25 hr to about 48 hr;

and

thereafter, combining a curing agent with the propellant composition.

6. The process of claim 1, wherein the ammonium nitrate is provided in an amount from about 40 to 85 weight percent of the propellant composition.

7. The process of claim 1, wherein the grinding provides the ammonium nitrate with an average size from about 5 to 400 microns.

8. The process of claim 5, wherein the second aging period is selected to be from about 0.25 to 48 hours.

9. The process of claim 1, wherein the synthetic zeolite is selected to comprise an aluminosilicate.

10. The process of claim 1, wherein the pore size is selected to be from about 3 to 5 angstroms.

11. The process of claim 1, wherein the binder is selected from the group consisting of a thermoplastic elastomer, a cure hardening material, and mixtures thereof.

12. The process of claim 11, wherein the binder is selected to comprise a cure hardening material selected from the group consisting of a hydroxy terminated polybutadiene, hydroxy terminated polyether, polyglycol adipate, glycidylazide polymer, poly bis-3,3'"'"'-azidomethyl oxetane, poly-3-nitratomethyl-3-methyl oxetane, polyethylene glycol, polypropylene glycol, cellulose acetate and mixtures thereof.

13. The process of claim 1, wherein the binder is provided in an amount from about 3 to 40 weight percent of the propellant composition.

14. The process of claim 4, wherein the strengthening agent is selected from the group consisting of azodicarbonamide, dicyandiamide, oxamide, and mixtures thereof;

the nitroplasticizer is selected from the group consisting of a nitrate ester, a nitramine, and mixtures thereof;

the energetic additive is selected from the group consisting of cyclotrimethylene trinitramine, cyclotetramethylene tetranitramine, dinitroxyethylnitramine, and mixtures thereof;

the nitrate ester stabilizer is selected to be N-methyl-4-nitroaniline;

the opacifier is selected to be carbon black;

the cure catalyst is selected from the group consisting of triphenyl bismuth, maleic anhydride, magnesium oxide, a tin dilaurate, metal acetylacetonate, and mixtures thereof;

the antioxidant is selected from the group consisting of 2,2'"'"'-bis(4-methyl-6-tert-butylphenol), 4,4'"'"'-bis(4-methyl-6-tert-butyl phenol) and mixtures thereof.

15. The process of claim 4, wherein the strengthening agent is provided in an amount of about 2 to 20 weight percent, each nitroplasticizer is provided in an amount from about 5 to 25 weight percent, the energetic additive is provided in an amount from about 5 to 25 weight percent, the nitrate ester stabilizer is provided in an amount from about 0.1 to 3 weight percent, the opacifier is provided in an amount of up to about 2 weight percent, the cure catalyst is provided in an amount of up to about 0.3 weight percent, and the anti-oxidant is provided in an amount of up to about 1 weight percent, each by weight of the propellant composition.

16. The process of claim 5, wherein the curing agent is selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, trimethylxylene diisocyanate, dimeryl diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, dianisidine diisocyanate, phenylene diisocyanate, xylylene diisocyanate, other diisocyanates, triisocyanates, higher isocyanates than the triisocyanates, polyfunctional isocyanates and mixtures thereof.

17. The process of claim 5, wherein the curing agent is provided in an amount from about 0.5 to 5 weight percent of the propellant composition.

20. A process for preparing an age-stabilized propellant composition comprising adding an amount of a strengthening agent to the second mixture of claim 1, and then combining the binder with the second mixture.

21. The process of claim 20, wherein said strengthening agent is selected from the group consisting of azodicarbonamide, dicyandiamide, oxamide, and mixtures thereof.

22. The process of claim 21, wherein the adding step further comprises providing at least one member selected from the group consisting of a nitroplasticizer, an energetic additive, a nitrate ester stabilizer, an opacifier, a cure catalyst, a synthetic zeolite, and an antioxidant to yield the propellant composition.

23. The process of claim 22, further comprising adding a curing agent to the propellant composition.

24. The process of claim 20, wherein the strengthening agent is provided in an amount of about 2 to 20 weight percent.

25. The process of claim 21, which further comprises:

providing ammonium nitrate in an amount from about 40 to 85 weight percent of the composition;

grinding the ammonium nitrate sufficiently to decrease the ammonium nitrate to particles having an average diameter from about 5 to 400 microns; and

combining from about 2 to 20 weight percent of the strengthening agent, a nitroplasticizer, and from about 3 to 40 weight percent of a binder with the ammonium nitrate to form the propellant composition into a desired shape, wherein said propellant composition is substantially smoke-free upon combustion.

18. A process of forming an age-stabilized propellant composition, said process consisting essentially of the steps of:

providing ammonium nitrate in an amount from about 40 to 85 weight percent of the composition;

mixing a synthetic zeolite having pores which are from about 3 angstroms to 13 angstroms in diameter with said ammonium nitrate to form a first mixture;

aging said first mixture for a first aging period, wherein the first aging period is less than about 48 hr;

grinding said first mixture to yield a second mixture so as to increase the absorbability and retention of water in the synthetic zeolite and decrease the ammonium nitrate to particles having an average diameter from about 5 to 400 microns; and

adding a binder in an amount from about 3 to 40 weight percent of the composition with said second mixture to form a propellant composition into a desired shape, wherein said propellant composition is substantially smoke-free upon combustion.

19. A process of forming an age-stabilized propellant composition, said process consisting essentially of the steps of:

providing ammonium nitrate in an amount from about 40 to 85 weight percent of the composition;

mixing a synthetic zeolite having pores which are from about 3 angstroms to 13 angstroms in diameter with said ammonium nitrate to form a first mixture;

aging said first mixture for a first aging period, wherein the first aging period is less than about 48 hr;

grinding said first mixture to yield a second mixture so as to increase the absorbability and retention of water in the synthetic zeolite and decrease the ammonium nitrate to particles having an average diameter from about 5 to 400 microns;

adding a binder in an amount from about 3 to 40 weight percent of the composition with said second mixture to form the propellant composition into a desired shape;

aging the propellant composition for a second aging period, wherein the second aging period is from about 0.25 hr to about 48 hr; and

adding a curing agent with the propellant composition, wherein said propellant composition is substantially smoke-free upon combustion.