Title of Invention

"A PROCESS FOR PREPARATION OF AN IMPROVED ELASTOMER-DOUBLE BASE-COMPOSITE PROPELLANT "

Abstract

This invention relates to an improved elastomer—double base-composite propel lant-having improved properties. The composit has a propellant such as nitrocellulose an elastomer binder, A liquid oxidizer such as nitroglycerine. A curing agent having terminal isocyanate groups and additivee such as solid oxidiser and/or animonium perchlorate. A metallic fuel such as aluminium powder, a stabilizer, a catalyst, an additional stabiliser and processing aid. Further this invention relates to a process for preparing an elastomer double base composite propellant comprising reacting liquid oxidiser in a planetory mixer with the additives such as oxidiser, metallic, fuel, stabiliser, catalyst and curing agent which are added step by step at a temperature of 45 to 70ºC under partial vacuum.

Full Text

The present invention relates to a process for preparation of an improved elastomer-double base-composite propellant and method of preparation thereof. Composite propellants (CP) and composite modified double base propellants are generally used to meet the requirement of superior energy. For such known propellants in the prior art, nitrocellulose, hereinafter to be named as NC is incorporated as binder, more particularly in case of double base propellant, hereinafter to be named as DBP and composite modified double base propellant. herein after to be named as CMDBP. The major drawback of such known propellants in the prior art is that the binder like NC has poor solid loading capability and as well as poor low temperature properties. To overcome these limitations of known such propellants in the prior art, various types of elastomers are required to be incorporated in DBP and CMDBP formulations to get the resulted elastomer modified composite double base propellant, hereinafter to be named as EMCDBP. The elastomers applied in such cases are generally like polyglycol adipate, polyethylene glycol, polycaprolactone, hydroxy terminated poly butadiene, hereinafter to be named as HTPB etc. of these elastomers, HTPB is generally used as binder to form CP formulations. This formulation has inherent disadvantage of its own like non-compatibility and immiscibility of HTPB with nitrate ester plasticiser. This disadvantage has been overcome by incorporating ester or glycol blocks in HTPB chain by block copolymerisation technique wherein HTPB is used for ring opening polymerization to yield a block copolymer. Such known propellants are not free from disadvantages. Such known EMCDBP using the said block copolymer, comprising HTPB incorporated with ester or glycol block, alone as binder has limited ambient stress capabilities because of the longer cross link length of the block-copolymer in the propellant formulations. Yet another disadvantage of such known propellant of the prior art is the unsuitability in cartridge loading applications wherein lower elongation and better tensile strength properties are essentially required to provide structural integrity of cured propellant grains. Therefore, there is a great need for perfecting the EMCDBP formulations with improved stress capabilities, homogenitv. selected chain length of elastomer, suitable for cartridge loading capability and structural integrity of the propellant grains. An object of this invention is to propose an improved elastomer modified-composite-double base propellant with improved properties to overcome the drawback and disadvantage of the prior art as stated herein above, and to a method of preparation thereof. Another object of this invention is to propose an improved elastomermodified ftmnniitr double base propellant with improved mechanical properties suitable for cartridges loading capability, Nccnrding to this invention there is provided a process for preparation of an improved elastomer double base composite propellant comprising the steps of :- (a) preparing a block copolymer by reacting Hydrnvy Terminated Pn!y-Butadiene (HTPRi with caprolactone manomer (b) reacting 8-1! parts of block co polymer thus obtained by step(a) with !4 IS parts of Nitro-Glycerine (NG) as a liquid oxidizer and 1.5 to 2 parts of dicthylphthalate as an inert plasticiser, at a temperature of 45 to 60°C, in a reaction vessel, thus obtaining an elastomer-binder; .;) preparing curing agent by mixing poryols and toluene diisocyanatc in the ratio of ! :3; (d) mixing with the elastomer-binder obtained by step (b) 1.5 to 2.5 parts of curing agent obtained by step (c) with constant stirring £>:• 2!) to 4ft minutes followed by addition of 0.5 to 1 part of nitro-cellulose as a propellant, 16 parts of aluminium powder as metallic fuel. 0.5 parts of carbamite as stabilizer, 10 to 5S parts of ammonium perchlorate as solid oxidizer 0.04 parts of catalyst mixture and 0.1 part of lecithin as processing aid wherein the said ammonium perchlorate comprises mixture of ammonium per chlorite particles of two sizes with 14 to 17 parts of 8 to 10 micron size and 35 to 41 parts of 150-250 microns size, and wherein further said catalyst mixture comprises 0.02 parts of ferric acetic acetonate and 0.02 parts of triphenyl bismuth; (e) casting of propellent formulation in metallic moulds at a temperature of 45 to 70°O under partial vacuum of less than 10mm Hg. In accordance with this invention, the propcllant comprises of NC, csscntialh' spheroidal nitrocellulose (SNC) in minor proportions, and curing is carried out by using novel cm-iag agent as stated herein above made up of reaction of mixed polyols and toluene diisocyanatc, preferably in proportion of about 1:3, as stated above. The elastomer binder in the proposed propcllant formulation is essentially a block copolymer which in turn is preferably prepared from HTPB and caprolactone monomer and essentially having limited chain length. According to the preferred embodiment of the present ivention, the proposed propellant formulation comprises of additives such as oxidiser, metallic fuel, stabliliser, catalyst, curing agent, additional stabiliser and processing aid. According to another preferred embodiment of the present invention, the oxidiser is, preferably a rolid oxidiser like ammonium perchlorate, herein after to be named as AP, which in turn is of particle sizes in selected proportions like 60 to 70% of 150 to 250 microns and 30 to 4 0% of 8 to 10 microns . The metallic fuel according to the present invention is preferably aluminium powder of preferably 14 to 17 microns to give high heat during the functioning of the proposed propellant formulations and stabiliser for the proposed NC and NG system of the proposed propellant formulations is preferably carbamite in proportion of 1 to 2 parts of NG and wherein NC is preferably in 0.3 to 5 parts of the total propellant formulations. The said NC preferably with bulk density of 0.9 to 1 gm / cc and is essentially a spheroidal NC with 11.2 to 12.2% nitrogen content and subsequently serves as cross linker with elastomeric binders using the said novel curing agent. According to another preferred embodiemnt of the present invention, the said catalyst preferably is the combination of ferric acetic acetonate of about 0.01% and tri phenyl bismuth of 0.01%. According to another preferred embodiment of the present invention, the additional stabiliser like resorcinol of about 0.1% is incorporated which in turn stabilises the AP and UG, system. According to another preferred embodiment of the presort invention, process aid, preferably lecithin, can also be used of about 0.1% of the total propellant formulations. According to the yet another preferred embodiment of the proposed invention, the said binder like block copolymer which reacts with said liquid oxidiser like NG in weight ratio of preferably 1:1 to 1: 2.5, which in turn results in dor, i red energetic and mechanical properties of the propellant. Small amount of inert plasticiser preferably like dj-ethyl-phthalate in 1 to 2 parts of the total propellant formulations is incorporated to facilitate the mircibility of the said liquid oxidiser with the proposed propellant formulations. According to another preferred embodiment of the present invention, the said solid oxidiser like AP, essentially incorporated with the said .liquid oxidiser like NG and is preferably taken from 3:1 to 5:1 by weight ratio of the said metallic fuel like aluminium powder, wherein the percentage of aluminium powder generally does not exceed 20% in the proposed propellant formulations. According to still another preferred embodiment of the present invention, an improved elastomer -double base-composite propellant formulation is proposed preferably comprising of an inhibitor to acheive restricted burning surface of the proposed propellant wherein thn r..-»id inhibitor preferably comprises of the proposed block copolymer like HTBCP and essentially a novel curing agent like reaction product of polyols and diisocyanates and essentially a filler, preferablly antimony trioxide. According to the proposed process of the present invention, the said block copolymer preferably, prepared from HTFB and caprolnctone monomer, is first reacted with the liquid oxidiser , preferably NG in a planetary mixer, wherein other additive such as said oxidiser, said metallic fuel, said stabiliser, said catalyst and novel curing agent are added step by step. The said process avoids undue increase in viscosity . According to another preferred embodiment of the said process, the casting of the propellant formulations is undertaken under partial vacuum, preferably of less than 10 mm of mercury in metallic moulds, preferably of aluminium which in turn is subjected to a heating cycle of 45 to 70°C , preferably 45 to 50°C to achieve solidification of the propellant slurry. According to another preferred embodiment of the present invention, spheroidal NC, xidisers like AP, metallic fuel, aluminium powder are essentially added in the propellant compositions after drying in oven at preferable temperature of 45 to 60°c for several days in varying proportions from 2 to 7 to achieve the reduction in the moisture level of about 0.6%. Still, according to the another embodiment of the present invention, the solution comprising of HTBCP, NG, di-ethyl-phthalate is first treated to 45° to 60°C in the said reaction vessel to which the said additives are added step by step. Accordingly, the present invention proposes a process wherein the proper distribution of novel curing agent is further ensured by continuing stirring preferably under vacuum of less than 10 mm of mercury for a period of 20 to 40 minutes after complete addition of the said curing agent. Other objects of the present invention will become more apparent when taken in conjunction with the working examples described herein below which are not intended to limit the scope of the proposed invention. Any such modifications made herein falls within the scope of the present invention. Example 1 An elastomer -double base - composite propellant prepared according to the described method comprises of a hydroxy terminated block copolymer 11 parts, nitroglycerine 18 parts, diethylphthalate 2 parts, carbamite 0.5 parts, ammonium perchlorate of 8 micron particle size 14.7 parts and 150 -250 micron size 34.3 parts, aluminium powder 16 parts, nitrocellulose in dense form 1 part, curing agent 2.5 parts, ferric acetyi acetonate -l0i02 parts, triphenyl bismuth 0.02 parts and lecithin 0.1 part and gave elongation = 14.0%, density = 1.70 gm/cc, calorimetric value = 1463 cal/gm and burn rate at 70 Kg/cm2 pressure = 9 mm/s.. Example 2: An elastomer -double base - composite propellant prepared according to the described method comprises of a hydroxy terminated block copolymer 8 parts, nitroglycerine, 14.5 parts, diethyl phthalate 1.5 parts, carbamite 0.5 parts, ammonium perchlorate of Size 10 microns, 17.4 parts and 150 -250 microns 40.6 parts, aluminium powder 16 parts, nitrocellulose 0.5 parts» curing agent 1.5 parts, ferric acetyl acetonate 0.02 parts, triphenyl bismuth 0.02 parts and lecithin o.l p^rt and gave percentage elongation = 10%, density-- 1.74 gm/cc, calorimetric value = 1650.cal/gm and burn rate at 70 Kg/cmn2 pressure = 11 mm/s. I CLAIM: 1. A process for preparation of an improved elastomer doable base composite propellant comprising the steps of :- (a) preparing a block copolymer by reacting Hydroxy-Terminated-Poly-Butadiene (HTPB) with caprolactone monomer; (b) reacting 8-11 parts of block co-polymer thus obtained by step(a) with 14-18 parts of Nitro-Glycerine (NG) as a liquid oxidizer and 1.5 to 2 parts of diethylphthalate as an inert plasticiser, at a temperature of 45 to 60°C, in a reaction vessel, thus obtaining an elastomer-binder; (c) preparing curing agent by mixing polyols and toluene diisocyanate in; the ratio of 1:3; (d) mixing with the elastomer-binder obtained by step (b) 1.5 to 2.5 parts of curing agent obtained by step (c) with constant stirring for 20 to 40 minutes followed by addition of 0.5 to 1 part of nitrocellulose as a propellant, 16 parts of aluminium powder as metallic fuel, 0.5 parts of carbamite as stabilizer, 49 to 58 parts of ammonium perchlorate as solid oxidizer 0.04 parts of catalyst mixture and 0.1 part of lecithin as processing aid wherein the said ammonium perchlorate comprises mixture of ammonium per chlorite particles of two sizes with 14 to 17 parts of 8 to 10 micron size and 35 to 41 parts of 150-250 microns size, and wherein further said catalyst mixture comprises 0.02 parts of ferric acetic acetonate and 0.02 parts of triphenyl bismuth; (e) casting of propellent formulation in metallic moulds at a temperature of 45 to 70°C under partial vacuum of less than 10mm Hg. 2. A process as claimed in claim 1 wherein nitro-cellulose used is preferably spheroidal nitrocellulose with bulk density of 0.9 to lgm/cc and with nitrogen content of 11.2 to 12.2%. 3. A process as claimed in claim 1 wherein the aluminium powder as metallic fuel has size of 14 to 17 microns. 4. A process as claimed in claim 1 wherein 0.1 parts of resoreinol are used as an additional stabilizer. 5. A process as claimed in claimed in claim 1 wherein said casting of propellant is preferably carried out in aluminium moulds. 6. A process as claimed in claim 1 wherein said casting is carried out? preferably at 45 to 50°C. 7. A process as claimed in claim 1 wherein said addition of said curing agent is carried out preferably under vacuum of less than 10mm Hg. 8. A process as claimed in claim 1 wherein optionally a filler like antimony tribxide is used as an inhibitor. 9. A process for preparation of an improved elastomer double base composite propellant as substantially described and illustrate herein.

Documents:

2391-del-1995-abstract.pdf

2391-del-1995-claims.pdf

2391-del-1995-correspondence-others.pdf

2391-del-1995-correspondence-po.pdf

2391-del-1995-description (complete).pdf

2391-del-1995-form-1.pdf

2391-del-1995-form-2.pdf

2391-del-1995-form-3.pdf

2391-del-1995-form-4.pdf

2391-del-1995-gpa.pdf