Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-01-12
2003-05-20
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S492000, C524S526000, C525S331700, C525S332300, C060S200100, C060S204000
Reexamination Certificate
active
06566420
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a novel composition and method for providing insulation for solid propellant rocket motors, and more particularly to EPDM compositions having fibrous components such as carbon fibers or powder fillers such as silica, or also containing Kevlar reinforcing fibers and suitable for internal and external insulation applications on such rocket motors.
2. Background and Description of the Related Art
It is generally accepted current industry practice to prepare insulations for solid propellant rocket motors from a polymeric base importantly composed of an EPDM (ethylene-propylene-diene monomer) terpolymer blend and containing as one of the diene monomer components of the EPDM blend a 1,4-hexadiene (HD).
This EPDM terpolymer, which is commonly designated as the primary EPDM terpolymer since it is present in a higher concentration than the secondary EPDM terpolymer, has been established as a standard for solid propellant rocket motor insulations due to its superior ablation characteristics, excellent physical properties and processability.
For instance, an exemplary carbon fiber-filled rocket motor insulation composed of NORDEL 1040 as the primary terpolymer is commonly known in the industry as the STW4-2868 thermal insulation and has the following composition as shown in Table 1:
TABLE 1
STW4-2868 THERMAL INSULATION FORMULATION
(carbon fiber; parts by weight)
Parts by
Ingredient
Function
Weight
NORDEL 1040
Primary EPDM terpolymer base
80
Neoprene FB
Secondary polymer base
20
Zinc oxide
Activator
5
Sulfur
Curative
1
HAF carbon black
Pigment
1
MBT
Accelerator
1
AGERITE Resin D
Antioxidant
2
AGERITE HPS
Antioxidant
1
Tellurac
Accelerator
0.50
Sulfads
Accelerator
0.75
VCM carbon fibers
Filler
41
Total Parts by Weight
153.25
Alternatively, solid rocket motor insulations are also composed of compositions employing finely divided powder silica as a filler, with or without the added presence of a fibrous reinforcing agent.
Exemplary silica-filled rocket motor insulations have also included NORDEL 1040 and NORDEL 2522 as the primary terpolymer in their formulations and the resulting compositions are respectively commonly known in the industry as the 053A and DL1375 thermal insulations. They have the following compositions shown in Table 2:
TABLE 2
THERMAL INSULATION FORMULATION
(silica filled; parts by weight)
DL1375
053A
(parts by
(parts by
Ingredient
Function
weight)
weight)
NORDEL 1040
Primary EPDM
80
terpolymer base
NORDEL 2522
Primary EPDM
80
terpolymer base
Neoprene FB
Secondary
20
20
polymer base
Zinc oxide
Activator
5
5
Sulfur
Curative
1
AGERITE Resin D
Antioxidant
2
2
AGERITE HPS
Antioxidant
1
1
Captax
Accelerator
1
1
Tellurac
Accelerator
0.5
0.5
Sulfads
Accelerator
0.75
0.75
HiSil 233
Filler
35.5
35.5
Total Parts by Weight
146.75
146.75
In addition, an EPDM terpolymer comprising the HD monomer is sold under the tradename NORDEL 2722E. An exemplary silica-filled rocket motor insulation comprising NORDEL 2722E as the secondary terpolymer is commonly known in the industry as the DL1552A thermal insulation and has the following composition as shown in Table 3:
TABLE 3
DL1552A THERMAL INSULATION FORMULATION WITH SILICA
Parts by
Ingredient
Function
Weight
Buna EP T 3950 (Bayer Corp., Fiber,
Primary EPDM
75
Additives and Rubber Division of
terpolymer base
Orange, Texas)
NORDEL 2722E (DuPont Dow
Secondary EPDM
20
Elastomers)
terpolymer base
with high
ethylene content
WINGTACK 95 (hydrocarbon resin)
Tackifier
7
(Goodyear Tire and Rubber Co.,
Chemical Division of Beaumont,
Texas)
IRGANOX 1010 (tetrakis[methylene-3-
Antioxidant
1
(3′-5′-di-tert-butyl-4′-hydroxyphenyl)
proprionate]methane) (Ciba Specialty
Chemicals, Additives Division,
Tarrytown, N.Y.)
TRYCOL DA-6 (decyl
Wetting agent
0.5
polyoxyethylene alcohol)(Chemical
Associates, Inc. of Copley, Ohio)
Stearic acid (including palmitic acid)
Cure activator
1
(Harwick Standard Distribution Corp.
of Akron, Ohio)
HiSil 233 (silica hydrate)(PPG
Reinforcing filler
45
Industries, Inc. of Lake Charles,
Louisiana)
Aluminum oxide C (Al
2
O
3
)(Degussa
Reinforcing filler
0.3
Corporation of Ridgefield Park, N.J.)
N330 carbon black (Columbian
Pigment and
Chemicals Co. of Marietta, Ga.)
reinforcing filler
KALENE 1300 (butyl gum elastomer)
Co-vulcanizing
20
(Hardman Division of Harcros
plasticizer
Chemicals, Inc. of Belleville, N.J.)
HYPALON 20 (chlorosulfonated
Cure activator
5
polyethylene)(DuPont Dow
Elastomers)
AGERITE Resin D (polymerized
Antioxidant
0.25
trimethyl dihydroquinone)(R.T.
Vanderbilt Co., Inc. of Buena Park,
Ca.)
TZFD-88p (zinc oxide dispersed in an
Cure activator
2
EPDM binder)(Rhein Chemie Corp. of
Trenton, N.J.)
SP 1056 (bromomethyl alkylated
Curing agent
15
phenolic resin)(Schenectady Int'l, Inc.
of Schenectady, N.Y.)
Total Parts by Weight
193.05
An exemplary aramid fiber filled rocket motor insulation comprising NORDEL 1040 is commonly known in the industry as R196 thermal insulation and has the following composition as shown in Table 4:
TABLE 4
R196 THERMAL INSULATION FORMULATION WITH KEVLAR
Parts by
Ingredient
Function
Weight
NORDEL 1040 (EPDM terpolymer)
Polymer base
80
NATSYN 2200 (polyisoprene)
Polymer base
20
(Goodyear Tire and Rubber Co.,
Chemical Division of Akron, Ohio)
WINSTAY S (styrenated phenols)
Antioxidant
1.0
(Goodyear Tire and Rubber Co.,
Chemical Division of Akron, Ohio)
Dechlorane Plus 515
Flame retardant
40
(1,2,3,4,7,8,9,10,13,13,14,14-
dodecachloro-
1,4,4a,5,6,6q,7,10,10a,11,12,12a-
dodecahydro-1,4,7,10-
dimethanodibenzo (a,e) cyclooctene)
(Occidental Chemical Corporation of
Dallas, Texas)
Antimony oxide (Sb
2
O
3
)(Harcros
Flame retardant/-
20
Chemicals, Inc. of Kansas City,
filler
Kansas)
¼″ KEVLAR fiber (aramid staple fiber)
Fiber
20
(E.I. duPont de Nemours and Co., of
Wilmington, Delaware)
VAROX DBPH-50 (2,5-dimethyl-2,5-
Curing agent
2.5
di(t-butylperoxy)hexane on a carrier)
(R.T. Vanderbilt Co., Inc. of Buena
Park, Ca.)
Total Parts by Weight
183.5
Numerous past efforts to develop effective replacements for these standard solid rocket motor insulation formulations have not been successful.
The only manufacturer currently producing the foregoing primary EPDM terpolymer in adequate quantities to meet the demands of the rocket motor insulation industry is DuPont Dow Elastomers of Beaumont, Tex., which markets and sells an EPDM terpolymer comprising the HD monomer under the tradename NORDEL 1040 and Nordel 2522.
However, the ability of the industry to produce STW4-2968, DL1375, 053A, DL1552A, R196 and other thermal insulations containing NORDEL 1040 and NORDEL 2522, and NORDEL 2722E as a primary or secondary EPDM terpolymer has recently been placed in jeopardy due to the announcement by DuPont of its intention to cease production of NORDEL 1040, 2522, 2722E and, generally, other EPDM polymers formed from 1,4-hexadiene. There is therefore a need in this industry, previously not satisfied, to find an effective alternate or a replacement for the above-described standard STW4-2868, DL1375, 053A DLl1552A and R196 thermal insulations. Development and formulation of a suitable primary EPDM terpolymer replacement is especially critical for these discontinued NORDEL insulation formulations.
The requirements for an acceptable, functionally effective, insulation for solid propellant rocket motors are well known to be quite severe due to the extreme conditions to which the insulation is exposed. These conditions not only include exceedingly high temperatures but also severe ablative effects from the hot particles (as well as gases) that traverse and exit the rocket motor interior. Unless the insulation will withstand such conditions, catastrophic failure may (and has) occur.
U.S. Pat. No. 3,347,047, an early patent describing asbestos fiber filled insulations, states that flame temperatures encountered in the combustion of propellants, part
Guillot David G.
Harvey Albert R.
Alliant Techsystems Inc.
Sullivan Law Group
Yoon Tae H.
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