Title of Invention

"AN IMPROVED METALLIZED NITRAMINE BASED COMPOSITE MODIFIED DOUBLE BASE ROCKET PROPELLANT AND A PROCESS FOR PREPARATION THEREOF"

Abstract This invention relates to a process for preparing an improved metallised nitramine based composite modified double base rocket propellant formulation comprising in the steps of mixing 25-35% Spheroidal Nitro-Cellulose (SNC) with 30-40% desensitized Nitro glycerine (NG) in a mixer for 10 to 20 minutes to obtain slurry, adding 1-8% Ammonium Perchlorate (AP) to the slurry obtained by step (a) at 25+ 2°C and mixing for 5-10 minutes, add metal fuels as herein described to slurry obtained from step (b) and mixing for 5-10 minutes at 25+ 2°C, adding 8-15% of energetic component to slurry obtained from step ( c), adding 0.5-5% ballistic modifier to the step ( d) and continued mixing for 10-20 minutes without vacuum and for 40-60 minutes under vacuum of 5-10 mm of Hg at 25+ 2°C, casting the slurry obtained from step (e) in a mould under vacuum of 2-5 mm and releasing the vacuum after casting is completed, transferring cast mould obtained by step (f) to a water jacketed oven at 50+ 2°C and curing as herein described.
Full Text FIELD OF INVENTION
The present invention relates to the process of preparation of an improved metallised nitramine based Composite Modified Double Base(CMDB) propellant wherein the composition obtained has superior combustion characteristics at low pressure, high burn rate, low pressure index value and overall superior performance with clean combustion products.
PRIOR ART
Solid propellant compositions containing ammonium perhclorate (AP) as base have been used for achieving high specific impulse (Isp) for aerospace applications. However, such propellant compositions pose severe pollution hazard due to the presence of chlorine in their combustion products. Another type of compositions employing nitramine, such as cyclotrimethylene-trinitramine (RDX)/cyclo tetramethylene tetranitramine (HMX) have potential in terms of their clean burning characteristics with high specific impulse (Isp). However these nitramine based propellant compositions have also certain disadvantages. One of such disadvantage is of poor combustion efficiency, specifically at low pressure range. Another disadvantage is their low burn rates and high pressure index value.
Still another disadvantage of these propellant compositions based on nitramine is that, when metal fuel, AI is incorporated for enhancing the energetics of this propellant composition, to the level required for modern aerospace applications (Lsp 240-260), there occurs much more severe combustion problem due to high heat of formation of its combustion product A1 O3.
Solid propellant using ammonium nitrate (AN) as base have also been used in many of the compositions for aerospace applications.
One of the disadvantages of these propellant compositions using ammonium nitrate is their poor performance capability and inability to combust Aluminum efficiently. Another disadvantage is their poor structural integrity due to phase change of Ammonium Nitrate (AN) accompanied with volume change in the temperature range of practical significance (at-32°C).
OBJECTS OF THE PRESENT INVENTION
The primary object of the present invention is to provide an Nitramine based metallised Composite Modified Double Base (CMDB) Rocket Propellant composition and a process for preparation thereof wherein propellant has clean combustion products.
Another object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition which provides sustained combustion at low pressure (1 Mpa onwards).
Still another object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition having superior burn rate characteristics.
Yet another object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition having high energy in terms of specific impulse (Isp).
Further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition which uses combination of AP as an Oxidative additive and ballistic modifiers enabling stable combustion at lower pressure in addition to superior burn rate.
Yet further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition which uses simple slurry cast production technique.
Still further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition which incorporates metal fuel like Zr, which improves combustion characteristics.
Yet further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition which incorporates metal fuel like AI which improves energetics.
Even further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition to which Cu-chromite could be added to catalyze the combustion leading to high burn rate.
Still further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition and a process for preparation thereof which eliminates the use of special process equipment.
Even further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition which is homogeneous and ballistically uniform composition.
Still further object of the present invention is to provide an improved metallised Nitramine based Composite Modified Double Base Rocket Propellant composition with improved ballistics of the final product.
SUMMARY OF INVENTION
According to this invention there is provided a process for preparing a metallised nitramine based composite modified double base propellant formulation comprising in the steps of:
a) mixing 25-35% Spheroidal Nitro-Cellulose (SNC) with 30-
40% desensitized Nitro glycerine (NG) in a mixer for 10 to 20
minutes to obtain slurry,
b) adding 1-8% Ammonium Perchlorate (AP) to the slurry
obtained by step (a) at 25+ 2°C and mixing for 5-10 minutes,
c) add metal fuels as herein described to slurry obtained from
step (b) and mixing for 5-10 minutes at 25+ 2°C,
d) adding 8-15% of energetic component to slurry obtained
from step (c),
e) adding 0.5-5% ballistic modifier to the step ( d) and
continued mixing for 10-20 minutes without vacuum and for
40-60 minutes under vacuum of 5-10 mm of Hg at 25+ 2°C,
f) casting the slurry obtained from step (e) in a mould under
vacuum of 2-5 mm and releasing the vacuum after casting is
completed,
g) transferring cast mould obtained by step (f) to a water
jacketed oven at 50+ 2°C and curing as herein described,
SNC with particle size of 25µ gives high viscosity slurry while SNC of particle of more than 35µ gives product of low mechanical properties. RDX is the main energetic component of this solid propellant composition,Zr powder is incorporated to improve combustion at lower pressure, while aluminum is a added to improve propellants overall performance in term of energetics. AP and copper chromite is added to realize high burn rates and combustion at wide range of pressure. AP which poses pollution hazard, is present as oxidative additive and Cu-cbromite which is a non energetic compound is present as ballistic modifier. However, the final product is less hazardous to environment and more energetic. The SNC has particle size 25-35µ and comprises of NC 88-92%. NG 6-8%, sym-diethyl diphenyl urea 2-4% ]. The desensitised NG is in 30-40% and comprises of NG 78-82%, diethyl phthalate 16-20%, 2-nitrophenyl amine 1-2% ]. Other constituents are RDX with (particle size 22-30µ) 8-15%, AP (particle size 3-8µ) 1-8%, Al (particle size 15-20µ) 10-17%, Zr(particle size 2-1 OH) 2-8% and Cu-cromite (particle size 3-8µ) 0.5-5 parts. The composition undergoes sustained combustion even at chamber pressure of 1 MPa. The burn rates of the order of 4-20 mm/s in the pressure range of 1-11 Mpa with Isp of the level of f ~260s at 7 Mpa have been achieved.
The present invention envisage a slurry cast technique for preparation of an improved Nitramine based solid rocket propellant composition which comprises of the following steps:
(a) PREPARATION OF SPHEROIDAL NC
Nitrocellulose is prepared by the nitration of cellulose. This product is fibrous. It is gelletenised in ethyl-acetate and required quantities of NG as well as sym-diethyl diphenyl urea are added. The Spheroidal NC is obtained by precipitation with water in the presence of surfactant. The final composition of SNC is NC 88-92%, NG 6-8%, sym-diethyl diphenyl urea 2-4%.
(b) PREPARATION OF DESENSITIZED NG
NG is obtained by the nitration of Glycerol. It is desensitised by adding it to diethyl phthalate under mild agitation. 2-nitrodiphenyl amine is
added as stabiliser. The final composition of decensitised material is NG 78-82%, diethyl phthalate [email protected], 2-nitrodiphenyl amine 1-
2%.
(c) Spheroidal NC(SNC) [30±5µ particle size] 25-35%, preferably
29-31%, is mixed with desensitized NG 30-40%, preferably
35-37%, in a planetary mixer for 10 to 20 minutes to obtain
slurry.
(d) Adding AP (3-8µ particle size) 1-8%, preferably 3-6% by
weight to the slurry obtained by step (a). The mixing is
continued at 25±2°C and RH (e) Adding metal fuel Zr (2-10µ particle size) 2-8%, preferably 3-
5% by weight in the above slurry obtained from step (b) and
continuing mixing for 5-10 minutes at 25±2°C and RH (f) Adding metal fuel Al(15-20µ particle size) 10-17%,
preferably 12-15% by weight in the above slurry obtained
from step (c) and continuing mixing for 5-10 minutes at
25±2°C and RH (g) Adding RDX(22-30µ particle size) 8-15%, preferably 11-13%
by weight in the above slurry obtained from step (d) and
continuing mixing for 5-10 minutes at 25±2°C and RH (i) Casting the slurry obtained from step (f) above in a mould under vacuum of 2-5 mm of Hg at 25±2°C and releasing the vacuum after casting is completed.
(j) Transferring cast mould obtained by step (g) to a water jacketed over at 50±2°C curing it for 8 to 12 days. Thereafter curing it for 3 to 6 days at 40±2°C.
The different constituents of the Metallized Nitramine propellant formulation of the present invention has synergistic effect on each other such that the combustion characteristics possessed by the formulation is not possessed by any of the individual constituents of the present propellant formulations.
This invention will now be illustrated with a working example which is intended to be typical example to explain the technique of the present invention and is not intended to be taken restrictively to imply any limitation in the scope of the present invention.
WORKING EXAMPLE
Throughout the working of the propellant, all the mixing and casting operations of the composite constituents and the final product are performed in a closed environment controlled room, where the room temperature is maintained at 25±2°C and RH (relative humidity) is not allowed to exceed 55%.
All the ingredients of the propellant are allowed to cool down to the room temperature before commencement of the next step. A load of properly weighed, 1.8 kg of desensitized NG was transferred to planetary mixer and the mixing operation was initiated. Another load of 1.450 kg of SNC (particle size 34µ) was added to the above planetary mixer and further mixing of these two constituents continued for another fifteen minutes to obtain a homogenous slurry. Subsequently, 0.250kg of (fine) AP (particle size 4µ) was added to the same slurry and mixing continued for further five minutes. Subsequently, 0.650kg of Aluminum powder (particle size 16µ) was added to the same slurry and mixing continued for further five minutes. Subsequently, 0.225 kg of Zr powder (particle size 7µ) was added to the same slurry and mixing continued for further five minutes. Subsequently, 0.625kg of RDX (particle size 25µ) was added to the same slurry and mixing continued for further five minutes. Lastly O.lkg of Cu-chromite (particle size 4µ) was added to the same slurry and mixing continued for further fifteen minutes without vacuum and forty-five minutes under vacuum of the order of 8-10 mm of Hg. The slurry so obtained was cast in mould under vacuum of the order of 2-4 mm of Hg. After casting, vacuum was released and the mould was transferred to a water jacketed oven maintained at 50±2°C for 10 days for curing it. Therefore, further curing the case for 4 days at 40±2°C.
The burn rates of the cured compositions were determined in the pressure range of 1-11 Mpa by employing acoustic emission technique. The formulation as per the above example exhibited burn rates varying from 4-20 mm/s in the pressure range of 1-10 MPa as per table given below
a) BURN RATES
(Table Removed)
By varying the ratio of SNC, desensitised NG, Zr, Al, AP and ballistic modifier, the process of the present invention provide compositions with wide range of burn rates. It is therefore to be understood that the method of the present invention is susceptible to modifications, changes and adaptations by those skilled in the art. Such variations/modifications and adaptations are intended to be within the spirit and scope of the present invention which is set forth by the following claims:-






WE CLAIM:
1. A process for preparing an improved metallised nitramine based composite modified double base Rocket propellant formulation comprising in the steps of:
a) mixing 25-35% Spheroidal Nitro-Cellulose (SNC) with 30-
40% desensitized Nitro glycerine (NG) in a mixer for 10 to 20
minutes to obtain slurry,
b) adding 1-8% Ammonium Perchlorate (AP) to the slurry
obtained by step (a) at 25+ 2°C and mixing for 5-10 minutes,
c) add metal fuels as herein described to slurry obtained from
step (b) and mixing for 5-10 minutes at 25+ 2°C,
d) adding 8-15% of energetic component to slurry obtained
from step (c),

e) adding 0.5-5% ballistic modifier to the step ( d) and
continued mixing for 10-20 minutes without vacuum and for
40-60 minutes under vacuum of 5-10 mm of Hg at 25+ 2°C,
f) casting the slurry obtained from step (e) in a mould under
vacuum of 2-5 mm and releasing the vacuum after casting is
completed,
g) transferring cast mould obtained by step (f) to a water
jacketed oven at 50+ 2°C and curing as herein described,
2. A process as claimed in claim 1, wherein Spheroidal Nitro-Cellulose (SNC) preferably comprises of 88-92% Nitro-Cellulose (NC), 6-8% Nitro glycerine (NG) and 2-4% sym-di-ethyl diphenyl urea.
3. A process as claimed in claim 1, wherein the particle of size of Spheroidal Nitro-Cellulose (SNC) is preferably 25-35 microns.
4. A process as claimed in claim 1, wherein desensitized Nitro
glycerine (NG) comprises of preferably 78-82% Nitro glycerine (NG),
16-20% diethyl phthalate and 1-2% 2-nitrodiphenyl amine.
5. A process as claimed in claim 1, wherein said mixing of Spheroidal
Nitro-Cellulose (SNC) and desensitized NG is carried out by taking
29-31% Spheroidal Nitro-Cellulose (SNC) and Nitro glycerine (NG).
6. A process as claimed in claim 1 wherein Ammonium Perchlorate is
present in an amount of 1-8% preferably in 3-6%.
7. A process as claimed in claim 1 wherein metal fuel is Aluminum
present in an amount of 10-17% preferably 12-15% by weight.
8. A process as claimed in claims 1 & 7, wherein metal fuels
Aluminum has particle size 15-20 microns and Zr with particle size
2 to 10 microns.
9. A process as claimed in claim 1 wherein metal fuel Zr is in
quantity 2-8% preferably in quantity 3-5% by weight.
10. A process as claimed in claim 1 wherein particle size of Ammonium Perchlorate (AP) is preferably 3 to 8 microns.
11 .A process as claimed in claim 1 wherein mixing of Ammonium Perchlorate (AP) to the slurry of Spheroidal Nitro-Cellulose (SNC) and desensitized Nitro glycerine (NG) is carried out at 23 to 27°C under controlled relative humidity 12.A process as claimed in claim 1 wherein the energetic component is RDX and present in an amount of 8-15% preferably 11-13% by weight.
13.A process as claimed in claim wherein particle size of RDX is 22-30 microns.
14.A process as claimed in claim 1 wherein the ballistic modifier is cu-chromite and present in an amount of 0.5 to 5%.
15. A process as claimed in claim 14 wherein particle size of copper
chromite is 3 to 8 microns.
16. A process as claimed in claim 14 wherein said addition of copper
chromite is done first without vacuum for 10-20 minutes followed by
mixing under vacuum of 5-10 mm of Hg at 23 to 25°C and RH 17. A process as claimed in claim 1 wherein said slurry casting is done
under vacuum of 2-5 mm of Hg preferably at 23 to 25°C.
18. A process as claimed in claim 1 wherein said curing is carried
preferably at 47 to 52°C followed by curing at 38 to 42°C.
19. A process for the preparation of metallised nitramine based
composite modified double base propellant formulation substantially
described and illustrated in the examples.


Documents:

417-del-2000-abstract.pdf

417-del-2000-assignment.pdf

417-del-2000-claims.pdf

417-del-2000-correspondence-others.pdf

417-del-2000-correspondence-po.pdf

417-del-2000-description (complete).pdf

417-del-2000-form-1.pdf

417-del-2000-form-19.pdf

417-del-2000-form-2.pdf

417-del-2000-form-3.pdf

417-del-2000-form-5.pdf

417-del-2000-gpa.pdf

417-del-2000-petition-137.pdf


Patent Number 239994
Indian Patent Application Number 417/DEL/2000
PG Journal Number 30/04/2010
Publication Date 30-Apr-2010
Grant Date 21-Apr-2010
Date of Filing 07-Apr-2000
Name of Patentee CHIEF CONTROLLER, RESEARCH AND DEVELOPMENT
Applicant Address MINISTRY OF DEFENCE, GOVT OF INDIA B-341, SENA BHAWAN,DHQ P.O. NEW DELHI-110011
Inventors:
# Inventor's Name Inventor's Address
1 NANDAN ASTHANA HEMRL, SUTARWADI, PUNE-411021, INDIA.
2 HARIDWAR SINGH HEMRL, SUTARWADI, PUNE-411021, INDIA.
3 CHANDRAKANT NANASAHEB DIVEKER HEMRL, SUTARWADI, PUNE-411021, INDIA.
PCT International Classification Number C06D 5/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA