U.S. patent number 3,755,311 [Application Number 04/670,018] was granted by the patent office on 1973-08-28 for ferrocene derivatives.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Roswitha Zimmer-Galler.
United States Patent |
3,755,311 |
Zimmer-Galler |
August 28, 1973 |
FERROCENE DERIVATIVES
Abstract
Compounds useful as burning rate catalysts for solid propellants
characterized by low volatility and having the formula ##SPC1## Are
disclosed wherein R is O, NR' and S and each R' is hydrogen, lower
alkyl, phenyl, cyano and nitro.
Inventors: |
Zimmer-Galler; Roswitha
(Washington, DC) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
24688645 |
Appl.
No.: |
04/670,018 |
Filed: |
September 19, 1967 |
Current U.S.
Class: |
544/225; 987/3;
149/19.2; 149/76; 149/60; 149/92 |
Current CPC
Class: |
C07D
239/62 (20130101); C07F 17/02 (20130101); C07D
263/62 (20130101) |
Current International
Class: |
C07D
239/00 (20060101); C07D 239/62 (20060101); C07F
17/00 (20060101); C07D 263/00 (20060101); C07D
263/62 (20060101); C07F 17/02 (20060101); C07d
051/00 () |
Field of
Search: |
;260/257,260,439CY,24R |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Levina et al., Russian Chem. Reviews, (English Translation), Vol.
29, pp. 6 to 452 (1960)..
|
Primary Examiner: Sebastian; Leland A.
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is:
1. A compound represented by the general formula: ##SPC3##
wherein R is selected from the group consisting of 0, NR' and S,
each R' being selected from the group consisting of hydrogen, lower
alkyl, phenyl, cyano and nitro.
2. The compound of claim 1 of the formula ##SPC4##
wherein R" is selected from the group consisting of 0 and S.
3. The compound of claim 1 of the formula ##SPC5##
wherein R' is selected from the group consisting of hydrogen, lower
alkyl, phenyl, cyano and nitro.
4. The compound of claim 1 which is 5-ferrocenylmethylene
barbituric acid.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to a novel burning rate catalyst
and more particularly to a novel burning rate catalyst
characterized by very low volatility and which is especially useful
for controlling the burning rate of high energy composite type
propellants.
Solid propellant compositions are generally classed as being either
composite, if they consist of a mixture of a solid oxidant in a
matrix of a resinous or elastomeric fuel-binder composition, or
homogeneous, if they contain in a single molecule all the required
fuel and oxygen necessary for combustion.
The type of propellant composition useful for a given application
often is directly dependent upon the burning characteristics
required by the particular application. For example, to drive the
turbo-pump feed system of the fuel injector of a reaction motor, it
is desirable to use a high gas producing propellant characterized
by slow burning and low flame temperature; a composition often
referred to as a gas generating propellant or simply "gas
generator." For such applications, it would be desirable to use
nitramine oxidant containing composite propellants because of their
generally good burning properties, high energetics and high density
which permits higher energy release per unit volume. However, due
to their exceptionally low burning rates at the operating
temperatures and pressures normally required, the nitramines have
not been successfully adapted for gas generator applications.
Burning of a solid propellant is a localized phenomena in that it
occurs only on the exposed surface of the propellant grain. The
burning surface regresses by burning parallel layers in a direction
perpendicular to the surface in accordance with Saint-Robert's or
Veille's Law;
r = a + b p.sup.n
Where "r" is the burning rate; "a", "b" and "n" are constants and
"P" is pressure. The constant "n" is referred to as the burning
rate exponent.
It has long been known that the Veille Law constants can be
adjusted favorably by adding certain additives, known as burning
rate catalysts, to the composition. These additives tend to
accelerate the exothermic reactions at the burning surface thereby
acting to increase the burning rate of the composition.
Previously, however, no catalyst has been found which is entirely
satisfactory for increasing burning rates of nitramine containing
composite propellants. Ferrocene compounds, for example, although
long known to be effective burning rate catalysts for many
compositions, have not been wholly acceptable for composite
propellants because of their undesirably high volatility at
moderate storage temperatures. Because of this high volatility,
compositions catalyzed by ferrocene compounds possess a continually
changing burning characteristic as a function of storage time due
to vaporization of the ferrocene compounds from the
compositions.
It would be desirable, therefore, to provide a burning rate
catalyst which is essentially non-volatile at normal storage
temperatures and which may be used to control the burning rate of
composite propellants, such as nitramine containing composite
propellants.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a relatively
non-volatile burning rate catalyst which will accelerate the
burning rate of composite propellants without deleteriously
affecting their storage stability. It is also an object of this
invention to provide a burning rate catalyst which is effective in
accelerating the burning rate of nitramine oxidants such as RDX and
HMX.
Finally it is an object of this invention to provide a method for
producing a novel non-volatile ferrocene burning rate catalyst
useful for accelerating the burning rate of composite type
propellants.
These and other objects are achieved herein by providing the novel
burning rate catalysts of the formula: ##SPC2##
wherein R is selected from the group consisting of 0, NR' and S,
each R' being selected from the group consisting of hydrogen, lower
alkyl, phenyl, cyano, and nitro.
BRIEF DESCRIPTION OF THE DRAWING
One of the many advantages of the foregoing burning rate catalyst
can best be appreciated by reference to a drawing.
The solitary FIGURE is a graph illustrating the change in burning
rate as a function of pressure for a polyester RDX type nitramine
containing propellant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The novel burning rate catalysts of this invention are provided by
condensing ferrocene aldehyde with one or more compounds having a
reactive methylene group, such as barbituric acid, thiobarbituric
acid, 2-phenylmalonyl guanidine, 2-methylmalonyl guanidine,
2-ethylmalonyl guanidine, 2-cyanomalonyl quanidine and
2-nitromalonyl guanidine.
Examples of ferrocene compounds provided by this invention include
5-ferrocenylmethylene-2-phenylimino-4,6-dihydroxy pyrimidine,
5-ferrocenylmethylene thiobarbituric acid,
5-ferrocenylmethylene-2-methylimino-4,6-dihydroxy pyrimidine,
5-ferrocenylmethylene-2-ethylimino-4,6-dihydroxy pyrimidine,
5-ferrocenylmethylene-2-cyanoimino-4,6-dihydroxy pyrimidine,
5-ferrocenylmethylene-2-nitroimino-4,6-dihydroxy pyrimidine and
5-ferrocenylmethylene barbituric acid.
Because of the very low volatility (Table II) of these compounds,
they will not vaporize readily from the composition and hence may
be stored almost indefinitely without significantly affecting the
burning characteristics of the propellant as a function of storage
time; a problem characteristic of the prior art ferrocene burning
rate catalysts. While the ferrocene compound of this invention are
useful catalysts for a wide variety of propellant compositions,
they are particularly useful for accelerating the burning rate of
composite type propellants. The drawing is a graph of the log of
the burning rate of a polyester-RDX composite propellant as a
function of the log of the operating pressure. The slope of the
burning rate-pressure curve is the burning rate exponent "n". In
the system illustrated, the burning rate exponent of the unmodified
propellant (curve 2) is 0.72 whereas that containing 1 percent
5-ferrocenyl-methylene barbituric acid (curve 1) is 0.61. As will
be noted, the immediate ferrocene catalyst has a greater effect on
the burning rate at lower operating pressures of about 500 psi,
than at the higher operating pressures of about 1000 psi. Pressure
was determined by burning the propellant in a suitable inert
atmosphere in a pressurized bomb and burning rate was determined by
microwave detection means whereby microwaves are reflected from the
burning surface to a detecting device and the standing wave front
so created is measured as a function of time.
Essentially similar results are obtainable with the other ferrocene
compounds disclosed herein and with other oxidants other than the
nitramines. For example, desirable burning acceleration can be
obtained with ammonium perchlorate or ammonium nitrate containing
propellants.
The particular binder selected for the composite propellant is not
critical to the functioning of these catalysts and a wide variety
may be used in the compositions with similar results. For example,
operable binders include, asphalt, the phenolic resins,
hydrocarbons such as polyethylene and polystyrene, synthetic rubber
such as polybutadiene and modified synthetic rubber such as
butadiene acrylic acid copolymers, also vinyl polymers,
urea-aldehyde resins, nitrocellulose, glycerine, and
polyethyleneglycol adipate.
While it is not understood precisely why the catalysts of this
invention accelerate the burning rate, it is believed that they act
to reduce the decomposition temperatures of the propellants. For
example, at a heating rate 1.degree.C per min, the peak temperature
of decomposition (T.sub.dec) of a polyester-RDX propellant (71%
RDX, 25 percent polyglycoladipate) was affected by addition of
various ferrocene compounds as follows:
TABLE I
71% rdx, 25% polyglycoladipate
Modifier T.sub.dec (.degree.C) unmodified 190.degree.C 1% ferrocene
167.degree.C 1% 5-ferrocenylmethylene barbituric acid
176.degree.C
Having generally described the invention, the following examples
are provided herein for purposes of illustration only and are not
intended to be binding in any manner.
EXAMPLE
A solution of 3 g (0.024 mole) of barbituric acid in 100 ml water
was added to 4.3 g (0.02 mole) of ferrocene-aldehyde in 100 m1
ethyl alcohol. The reaction resulted in the precipitation of a
blue-violet colored product which after filtration was washed with
water and ether. By recrystallization from ethyl alcohol blue
needles were obtained which decomposed >294.degree.C.
(Determined by Differential Thermal Analysis).
C II N Fe Anal. calc'd for C.sub.15 H.sub.12 N.sub.2 0.sub.3 Fe:
55.58 3.73 8.64 17.23 Found 55.70 3.87 8.51 16.86
The yield was 6.1g (94%).
The following compounds can also be prepared in essentially the
same manner except using the corresponding active methylene
containing compound dissolved in a suitable alcohol. Preferably the
reactants are used in approximately equi-molar amounts. Among those
reactants which may be reacted with ferrocene aldehyde include:
2-phenylmalonyl guanidine, thio-barbituric acid, 2-methyl-malonyl
guanidine, 2-ethylmalonyl guanidine, 2-cyanomalonyl guanidine and
2-nitromalonyl guanidine. Condensation of these reactants with
ferrocene aldehyde provides respectively;
5-ferrocenylmethylene-2-phenylimino-4,6-dihydroxy pyrimidine,
5-ferrocenylmethylene thiobarbituric acid,
5-ferrocenylmethylene-2-methylimino-4,6-dihydroxy pyrimidine,
5-ferrocenylmethylene-2-ethylimino-4,6- dihydroxy pyrimidine,
5-ferrocenylmethylene-2-cyanoimino-4,6-dihydroxy pyrimidine, and
5-ferrocenylmethylene-2-nitroimino-4,6-dihydroxy pyrimidine.
Table II describes the vapor pressure of
barbituryl-ferrocenylmethene as compared with the prior art burning
rate catalyst; ferrocene.
TABLE II
Vapor Pressures of Ferrocene Temperature Pressure .degree.C mm Hg
50.0 0.09 63.1 0.27 70.8 0.40 80.5 0.70 92.0 1.47 97.0 2.13
Vapor Pressures of 5-ferrocenylmethylene barbituric acid
Temperature Pressure .degree.C mm Hg 40.0 0.016 55.0 0.025 70.0
0.034 85.0 0.043 98.5 0.055
As will be noted from the foregoing Table, the vapor pressure of
5-ferrocenylmethylene barbituric acid at normal storage
temperatures is significantly lower than that of ferrocene. This
difference in volatility reduces the tendency of the catalyst to
vaporize from its propellant compostion thereby reducing the
tendency for the burning characteristics of the propellant to
change with storage time. Having described the invention, it will
be apparent to those skilled in the art that many modifications and
changes can be without departing from the scope and spirit
thereof.
* * * * *