GB2121399A

GB2121399A - Propellant compositions

Info

Publication number: GB2121399A
Application number: GB08312345A
Authority: GB
Inventors: Hideki Machida; Toshio Kimura; Michinori Takizuka
Original assignee: Nippon Oil and Fats Co Ltd
Current assignee: NOF Corp
Priority date: 1982-05-07
Filing date: 1983-05-05
Publication date: 1983-12-21
Also published as: DE3316676C2; FR2526418B1; FR2526418A1; JPS58194790A; GB8312345D0; GB2121399B; JPS609998B2; DE3316676A1

Abstract

A propellant composition which contains nitrocellulose and nitroglycerine, contains as combustion catalyst copper benzoate and at least one of an organic lead salt, and an inorganic lead compound which compound can be metallic lead. The suggested organic salts include lead salicylate, lead stearate and lead 2- ethyl hexylate. The inorganic compounds may be lead stannate and lead oxide. The composition has a low pressure exponent and can be used as a high specific impulse propellant. The composition may contain, RDX, HMX, ammonium perchlorate, or potassium perchlorate, suitable metal powders stabilisers, plasticisers and polymeric binders.

Description

SPECIFICATION Propellant compositions The present invention relates to propellant compositions having a low pressure exponent and more particularly to high specific impulse type propellant compositions having a low pressure exponent.

There has hitherto been used a double base propellant (hereinafter, abbreviated as DB propellant) consisting mainly of nitrocellulose (hereinafter, abbreviated at NC) and nitroglycerine (hereinafter, abbreviated as NG) in the field of rocket propellant required to be smokeless.

Recently, there have been developed high specific impulse type propellants corresponding to the high performance to be required in the rocket propellant, that is, there have been developed a composite modified double base propellant (hereinafter, abbreviated as CMDB propellant) containing the above described main components of NC and NG and further containing oxidizers, such as ammonium perchlorate (hereinafter, abbreviated as AP), cyclotrimethylenetrinitrame (hereinafter, abbreviated as RDX), and metal powders, such as aluminum powders and the like; and further developed a composite double base propellant (hereinafter, abbreviated as CDB propellant) obtained by adding a binder to the DV propellant or the CMDB propellant.

It is known that the relation between the burning rate and the burning pressure of these propellants is generally represented by the following formula r = ap" wherein r represents a burning rate, p represents a burning pressure, n represents a pressure exponent and a represents a constant inherent to individual propellant.

In the rocket propellant, it is generally desirable from the viewpoint of the design of rocket motor and the burning stability of the propellant itself that the above described pressure exponent n is small.

Particuiarly, when n is nearly equal to O (nO), the burning is called as plateau burning, and when n is smaller than 0 (n < O), the burning is called as mesa burning. These plateau and mesa burning properties are preferable properties for rocket propellant.

It has been known that, as the combustion catalyst capable of giving such preferable properties to DB propellant, there are used an organic lead salt, such as lead salicylate, lead stearate or the like, lead oxide or metal lead alone or in admixture with a copper compound, such as an organic copper salt, for example, copper saiicylate and copper stearate, or copper oxide, or metallic copper (Japanese Patent Application Publication No. 4,928/74).

Such commonly known combustion catalyst can give the above described characteristics to DB propellants having a large NC content and generating a relatively small amount of energy. However, the combustion catalyst is not effective or is hardly effective for lowering the pressure exponent n in DB propellant having a high NG content, and in high specific impulse type propellants, such as the above described CMDB propellants and CDB propellants.

Recently, combustion catalysts capable of lowering noticeably the pressure exponent of such high specific impulse type propellants have been eagerly demanded, and the inventors have variously studied and found out that a novel combustion catalyst consisting of a specifically limited organic copper salt and at least one specifically limited organic lead salts and inorganic leads satisfies the above described demand, resulting in the present invention.

The feature of the present invention is the provision of a propellant composition at least containing NC and NG, the improvement comprising said composition containing, at a combustion catalyst, copper benzoate and at least one of organic lead salts and inorganic leads.

The invention will now be described in detail with reference to the accompanying drawings, wherein: Figs. 1-3 are graphs illustrating the relations between the burning pressure and the burning rate of DB propellants; and Figs. 4 and 5 are graphs illustrating the relations between the burning pressure and the burning rate of CMDB propellant and CDB propellant, respectively.

The combustion catalyst to be used in the present invention consists of copper benzoate and at least one of organic lead salts and inorganic leads. As the organic lead salts, there can be used lead salicylate, lead stearate, lead resorcylate, lead 2-ethylhexylate and the like. As the inorganic leads, there can be used lead stannate, lead oxide, metallic lead and the like. Copper benzoate is used in combination with at least one of these organic lead salts and inorganic leads.

The combustion catalyst is preferably used in an amount of from 0.5 to 5% by weight in total based on the total amount of the propellant composition. It is preferable that the amount of copper benzoate is from 0.2 to 4% by weight based on the total amount of the propellant composition. When the amount of copper benzoate contained in a propellant composition is less than 0.2% by weight and further the amount of organic lead salt or inorganic lead contained in the propellant composition is less than 0.3% by weight, the propellant composition has a high pressure exponent, while when the amount of copper benzoate exceeds 4% by weight and further the total amount of combustion catalyst exceeds 5% by weight, the amount of energetically inactive combustion catalyst is increased, and the resulting propellant composition is low in the specific impulse.Therefore, the use of the combustion catalyst in such a small amount or a large amount is not preferable.

The propellant of the present invention, containing NC, NG and the combustion catalyst, may occasionally contain plasticizers, such as diethylphthalate, dioctyl phthalate, tributyi phosphate, triacetin, dioctyl adipate, dioctyl sebacate and the like; oxidizers, such as RDX, cyclotetramethylenetetranitramine (HMX), AP, potassium perchlorate and the like; metal powders, such as aluminum powders and the like; stabilizers, such as diphenylamine and the like; binders, such as isocyanate-terminated polyester and the like; gelatinizers and the like.

The compounding amount of these ingredients can be generally determined by taking into consideration the specific impulse and other burning performances, mechanical properties, safeness, productivity and ageing resistance of the aimed propellant composition. For example, in the high specific impulse type DB propellant, the compounding amount of NC is 25 to 50% by weight, that of NG is 40 to 65% by weight, that of the total amount of plasticizer and gelatinizer is 3 to 1 5% by weight, and that of stabilizer is 0.3 to 5% by weight. The CMDB propellant is produced by adding from 0 to 40 parts by weight of AP, from 0 to 60 parts by weight of nitramines, such as RDX, HMX and the like, from 0 to 30 parts by weight of aluminum alone or in admixture to 100 parts by weight of the DB propellant having the above described composition.The CDB propellant is produced by replacing from 0.3 to 10% by weight of the total amount of the above described plasticizer and gelatinizer by a binder. In any of the above described DB propellant, CMDB propellant and CDB propellant, the combustion catalyst specified in the present invention must be contained in an amount of 0.55% by weight.

The propellant composition according to the present invention can be produced, for example, in the following method.

NG, a plasticizer and a combustion catalyst are mixed under a reduced pressure. Then, the resulting mixture is occasionally mixed together with an oxidizing agent and metal powders. Further, the resulting mixture is occasionally mixed together with a binder. Then, the resulting mixture is mixed together with a stabilizer and fine powdery NC under a reduced pressure to obtain a slurry of homogeneous mixture.

The slurry is cast into a mold under a reduced pressure, and the molded article is heated and cured to obtain a DB propellant, CMDB propellant or CDB propellant.

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof. In the table, "%" means % by weight.

Example 1 A DB propellant having a composition of Example 1 shown in the following Table 1 was produced in the following manner.

A mixture of 3,200 g of NG and 800 g of diethyl phthalate (DEP) was stirred, charged into a mixer, and then mixed therein at 300C for 20 minutes under a reduced pressure together with 200 g of lead salicylate (Pb-Sa) having an average particle size of not larger than 10 ym and 100 g of copper benzoate (Cu-Be) having an average particle size of not larger than 10,um. After mixing, 200 g of 2nitrodiphenylamine (2-NDPA) and 5,500 g of fine powdery NC were added to the above obtained mixture, and the resulting mixture was mixed at 400C for 40 minutes under a reduced pressure.After mixing, the resulting slurry was cast into a mold under a reduced pressure, and the molded article was cured at 500C for 10 days to obtain a DB propellant. 55 strand samples were produced from this DB propellant and subjected to a strand test according to the following method.

That is, 5 strand samples were burnt under each of pressures obtained by raising every 10 kg f/cm2 within the range of from 30 kg f/cm2 to 1 30 kg f/cm2 under a nitrogen atmosphere by using a Croford type strand apparatus, and the burning rate of the strand samples was measured.

The obtained results are shown by a solid line in Fig. 1. In Fig. 1, the ordinate represents the logarithm of burning rate (r, unit: mm/sec) and the abscissa represents the logarithm of burning pressure (P, unit: kg f/cm2). Fig.1 is a graph illustrating a relation between the burning pressure and the burning rate obtained by plotting an average burning rate under each burning pressure.

Comparative example 1 A DB propellant was produced according to Example 1, except that copper salicylate was used in place of copper benzoate. This DB propellant was subjected to the same test as described in Example 1.

The obtained results are shown by a broken line in Fig. 1.

Example 2 A high specific impulse type DB propellant was produced according to Example 1, except that the amount of NC and NG were changed into the amounts described in Example 2 in Table 1. The specific impulse shown in Table 1 is a value calculated by using a theoretical calculation program of NASA for rocket performance under a burning pressure of 80 kg f/cm2.

The resulting propellant was subjected to the same test as described in Example 1. The obtained results are shown by a solid line in Fig. 2.

Comparative example 2 A high specific impulse type DB propellant was produced according to Example 2, except that copper salicylate was used in place of copper benzoate. The resulting propellant was subjected to the same test as described in Example 1. The obtained results are shown by a broken line in Fig. 2.

Example 3 A high specific impulse type DB propellant having a composition of Example 3 shown in Table 1 was produced according to Example 1, except that lead oxide (PbO) was used in place of lead salicylate.

The resulting propellant was subjected to the same test as described in Example 1. The obtained results are shown by a solid line in Fig. 3.

Comparative example 3 A high specific impulse type DB propellant having a composition of Comparative example 3 shown in Table 1 was produced according to Example 3, except that copper salicylate was used in place of copper benzoate. The resulting propellant was subjected to the same test as described in Example 1.

The obtained results are shown by a broken line in Fig. 3.

Example 4 A CMDB propellant having a composition of Example 4 shown in Table 1 was produced in the following manner.

A mixture of 3,920 g of NG and 640 g of DEP was stirred, charged into a mixer, and then mixed therein at 3O0C for 20 minutes under a reduced pressure together with 1 60 g of lead salicylate having an average particle size of not larger than 10 ,am and 80 g of copper benzoate having an average particle size of not larger than 10 E4m. After mixing, the resulting mixture was further mixed together with 2,000 g of RDX. Then, the resulting mixture was further mixed at 4O0C for 40 minutes under a reduced pressure together with 160 g of 2-NDPA and 3,040 g of fine powdery NC. After mixing, the resulting slurry was cast into a mold under a reduced pressure, and the molded article was cured at 500C for 10 days to obtain a CMDB propellant.The resulting propellant was subjected to the same test, as described in Example 1. The obtained results are shown by a solid line in Fig. 4.

Comparative example 4 A CMDB propellant was produced according to Example 4, except that copper salicylate was used in place of copper benzoate. The resulting propellant was subjected to the same test as described in Example 1. The obtained results are shown by a broken line in Fig. 4.

Example 5 A CDB propellant having a composition of Example 5 shown in Table 1 was produced in the following manner.

A mixture of 6,000 g of MG and 4000 g of DEP was stirred, charged into a mixer, and then mixed therein at 300C for 20 minutes under a reduced pressure together with 200 g of lead salicylate having an average particle size of not larger than 10 ym and 200 g of copper benzoate having an average particle size of not larger than 10,um. The resulting mixture was then mixed at 3O0C for 20 minutes together with an isocyanate-terminated bifunctional polyester having a molecular weight of 3,000, and further mixed at 400C for 40 minutes under a reduced pressure together with 200 g of 2-NDPA and 2,600 g of fine powdery NC. After mixing, the resulting slurry was cast into a mold under a reduced pressure, and the molded article was cured at 500C for 10 days to obtain a CDB propellant.The resulting propellant was subjected to the same test as described in Example 1. The obtained results are shown by a solid line in Fig. 5.

Comparative example 5 A CDB propellant was produced according to Example 5, except that copper salicylate was used in place of copper benzoate. The resulting propellant was subjected to the same test as described in Example 1. The obtained results are shown by a broken line in Fig. 5.

TABLE 1

Example Comparative example 1 2 3 4 5 1 2 3 4 5 NC 55.0 38.0 44.0 30.4 26.0 55.0 38.0 44.0 30.4 27.0 NG 32.0 49.0 44.0 39.2 60.0 32.0 49.0 44.0 39.0 60.0 DEP 8.0 8.0 8.0 6.4 4.0 8.0 8.0 8.0 6.4 4.0 binder - - - - 4.0 - - - - 4.0 2-NDPA 2.0 2.0 2.0 1.6 2.0 2.0 2.0 2.0 1.6 2.0 Composition (%) RDX - - - 20.0 - - - - 20.0 Pb-Sa 2.0 2.0 - 1.6 2.0 2.0 2.0 - 1.6 2.0 PbO - - 1.0 - - - - 1.0 - Cu-Be 1.0 1.0 1.0 0.8 2.0 - - - - Cu-Sa - - - - - 1.0 1.0 1.0 0.8 1.0 * Specific impulse (sec) (P = 80 kg.f/cm) 223 236 234 244 249 223 236 234 244 249 (Note) NC: nitrocellulose, NG: nitroglycerine, DEP: diethyl phthalate, binder: isocyanate-terminated bifunctional polyester having a molecular weight of 3,000, 2-NDPA: 2-nitrodiphenylamine, RDX: cyclotrimethylenetriniramine, Pb-Sa: lead salicylate, PbO: lead oxide, Cu-Be: copper benzoate, Cu-Sa: cooper salicylate.

* Specific impulse is a value calculated by using a theoretical calculation program for rocket performance.

The pressure exponent (n) of the above described formula is represented by the inclination of a plotted line of the relation between the burning pressure (P) and the burning rate (r) on a logarithmic paper. Therefore, the following facts can be understood from the inclination of the solid line of the examples and that of the broken line of the comparative examples in the drawings.

Examples 1-3 and Comparative examples 1-3 illustrate embodiments of DB propellants. As seen from Table 1, Examples 2 and 3 and Comparative examples 2 and 3 illustrate embodiments of high specific impulse type DB propellants, and Example 1 and Comparative example 1 illustrate embodiments of DB propellants not having so high specific impulse.

In Fig. 1, although both the DB propellant of Example 1, which uses a combustion catalyst specified in the present invention, and the DB propellant of Comparative example 1, which uses a commonly known combustion catalyst, exhibit a mesa burning property, it is clear that the DB propellant of Example 1 is steeper in the inclination of the pressure exponent curve, and further is broader in the messa burning region than the DB propellant of Comparative example 1.In Fig. 2, the DB propellant of Example 2 produced by using a combustion catalyst specified in the present invention exhibits a mesa burning property in the high burning pressure region; while the DB propellant of Comparative example 2 produced by using a commonly known combustion catalyst does not become gentle in the inclination of pressure exponent curve in the high burning pressure region.In Fig. 3, although the DB propellant of Comparative example 3 produced by using a commonly known combustion catalyst has a gently inclined pressure exponent curve in the high burning pressure region, the DB propellant of Example 3 produced by using a combustion catalyst specified in the present invention has a noticeably gently inclined pressure exponent curve in the high burning pressure region, and finally exhibit a messa burning property, and further is gentler as a whole than the DB propellant of Comparative example 3 in the inclination of the pressure exponent curve.

Fig. 4 illustrates embodiments of CMDB propellant. The CMDB propellant of Example 4 produced by using a combustion catalyst specified in the present invention is remarkably gentler in the inclination of the pressure exponent curve in the high burning pressure region than the CMDB propellant of Comparative example 4 produced by using a commonly known combustion catalyst, and exhibits substantially a plateau burning property.

Fig. 5 illustrates embodiments of CDB propellant. The CDB propellant of Example 5 produced by using a combustion catalyst specified in the present invention is gentler as a whole in the inclination the pressure exponent curve than the CDB propellant of comparative example 5 produced by using a commonly known combustion catalyst, and has a low pressure exponent n.

As seen from the above described examples, according to the present invention, propellant compositions having a remakably low pressure exponent n is produced by using a specifically limited combustion catalyst, and the present invention is very effective in the production of high specific impulse type propellant composition.

Claims

1. In a propellant composition at least containing NC and NG, the improvement comprising said propellant competition containing, as a combustion catalyst, copper benzoate and at least one of organic lead salts and inorganic leads.

2. A propellant composition according to claim 1, wherein the total amount of copper benzoate and at least one of organic lead salts and inorganic leads is 0.5 to 5% by weight based on the total amount of the propellant composition.

3. A propellant composition according to claim 2, wherein the amount of copper benzoate is 0.2 to 4% by weight based on the total amount of propellant composition.

4. A propellant composition according to claim 1 and substantially as herein described.

5. A propellant composition according to claim 1 and substantially according to any one of Examples 1 to 5 herein.