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Патент USA US3041326

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June 26, 1962>
-w. R. GRIFFIN
3,041,316
ROOM TEMPERATURE VULCANIZATION OF' FLUORINATED
HYDROCARBON ELASTOMERS
Filed 0G13. 9, 1959
-lî
ff
/60
/20
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`
IN VEN TOR.
@wem/4’. 6'
»
United States;
dce
1
2
polymers having thermal stability at elevated tempera
3,041,316
tures.
ROOM TEMPERATURE VULCANIZATION 0F
FLUGRINATED HYDROCARBON ELASTO
MERS
A still further object of this invention is to provide a
class of room temperature vulcanizable elastomeric halo
gen-containing polymers having ñuid resistance.
Warren R. Grijiin, Dayton, Ohio, assigner to the United
States of America as represented by the United States
Still another object of this invention is to provide a
class of compositions useful as potting compounds for
electronic equipment and as sealant materials in subsonic
Aix- Force
Filed Oct. 9, 1959, Ser. No. 845,579
13 Claims. (Cl. 260-79)
(Granted under Title 35, U.S. Code (1952), sec. 266)
3,041,316
Patented June 26, 1962
aircraft.
10
The invention described herein may he manufactured
and used by or for the United States Government for gov»
ernmental purposes Without payment to me of any royalty
thereon.
This invention relates to the vulcanization of elastomers
and more particularly relates to the room temperature
vulcanization of fluorinated hydrocarbon elastomeric poly
-
The above and still other objects, advantages, and fea
tures of this invention will become apparent upon con
sideration of the following detailed description of speciñc
embodiments thereof, especially when taken in conjunction
with the accompanying drawing which is a graph illus
trating the properties of a vulcanizate produced by this
invention.
lt has been found, in accordance with the invention,
that the aforestated objects are accomplished by first pro~
mers suitable for use in high temperature resistant fuel
viding chemically reactive sites at elevated temperatures
tank and vehicle structure sealants for supersonic aircraft 20 on selected halogenated hydrocarbon polymers followed
and missiles. In a more specific aspect this invention re
by vulcanization at room temperature with a polyfunc
lates to a method of vulcanizing selected fluorine-con
tional compound. The halogenated hydrocarbon-«poly
taining copolymers by ñrst providing chemically reactive
mers found to be of special value in this invention are the
sites on the copolymers at elevated temperatures followed
halogenated alkyl-vinylidene fluoride copolymers which,
by cross-linking through these sites at room temperatures. 25 as is well known, are not easily attacked at room tempera
' Various types of elastomeric materials have been em
ture by cross-linking agents capable of complete reac
ployed as fuel tank sealants. However, with the advent
tion. Accordingly, it was found that by providing chem
of high speed aircraft and missiles, it was necessary> that
ically reactive sites or “handles” on the polymer chain at
sealant materials be developed which would be ñuid re
elevated temperatures, room temperature vulcanization
sistant, resistant to elevated temperatures in the range of 30 could be eifected -by reacting the modiñed .polymer with
500°-600° F. and be capable of vulcanization at room
temperatures. Room temperature vulcanization is a nec
essary feature of the polymeric liquids used as sealants for
polyfunctional cross-linking agents. The formation of the
reactive sight is the ñrst step and is accomplished by using
various amines.
without this feature delicate electronic equipment, wing
The amines which can be employed in this invention
and cabin structures, and perhaps whole aircraft would 35 are primary amines such as ethylamine, propylamine and
have to be subject to harmful exposure to conventionally
the like; secondary amines such as diethylamine, diiso
high vulcanization temperatures during manufacture.
propylamine,
di-n-butylamine, diisobutylamine, di-n-octyl
While such exposures are not impossible, the need for high
amine,
diallylamine,
and the like; and tertiary amines
vulcanization temperatures has discouraged the use of
many elastomeric polymers which would otherwise have 40 such as triethylamine, tripropylamine,. triamylamine, tet
ramethylguanidine, and the like. The methyl homologs
provided a suitable basis for sealant materials.
of the primary secondary and tertiary amines undergo re
Previously, subsonic aircraft employed sealant materials
based on liquid polysuliide elastomers which were gener
arrangement or decomposition and produce a cross-linked
product during the site formation reaction.' Therefore,
ally satisfactory. However, they were limited in thermal
stability to 275° F. and under present `day operating con 45 the methyl homologs are not useful under the conditions
Vdescribed herein. It is theorized that these agents pro
ditions the need for sealant materials resistant at temper
ature ranges of 500°-600° F. is urgent.
vide reactive sites in the halogenated polymer such as
The halogenated hydrocarbon elastomers, as is well
commercially available Viton A (a copolymer of hexailuo
known, possess the necessary thermal stability and ñuid
ropropylenevinylidene fluoride). All of these amines
resistance for high temperature sealant applications. 50 provide double bonds on the polymer chain and in the case
However, prior to this invention the ñuorinated elasto
of the unsaturated primary and secondary amines the
mers required 300° and 400° F. temperatures with ap
plied pressures for complete vulcanization.
Accordingly, it is an object of this invention to circum
vent the above-described limitations so as to produce a 55
sealant material which will operate effectively in high
speed aircraft and missiles.
Another object of this invention is to provide a proc
ess for producing a class of vulcanizable elastomeric halo
gen-containing polymers capable of being vulcanized at 60
room temperatures.
A further object of this invention is to provide room
temperature vulcanizable elastomeric halogen-containing
double bonds of the amines are additional active sites,
Examples of theorized reactive sites are illustrated as
follows:
'
'
3,041,316
4
Hexamethylene dithiol
CASE II.--PRIMARY UNSATURATED AMINES
Presence of tIi-n-amylamine and moisture at 75° F.
C Fs
Additional
sites for
cross-linking
ona-cn-cng-N-orn-oiho'm
[-0 rt-crn-c-cri
25
CFíl
x
The vulcanizate produced -by the method of this inven
tion and ,illustrated lby the. foregoing theoretical `reactions
showedexcellent thermalfstability at 400° F. which sta
Ci F a
30 bility. will be hereinafterï demonstrated in greater detail.
-C Fà-CHrC- C 10i
However, the products preparedusing; saturated and un-V
saturated primary amines and tertiary amines appeared to
The: following,equationillustrates. .the reactive site forl
beinferior to the~ unsaturated andsaturated secondary
mationzwith diallylamine:
REACTION NO. 1.-REACTIVE SITE FORMATION
amines during thermal stability tests. The pendant prod
u uct ofthe primaryk amines are; activated at elevated tem
FOR` CASE IV'
peratures causing undesirable »hardening of the elastomer.
The tertiary` amines de_not form pendant groups and are
[ .-CF
. 2-CH21-Cons
F~C Fr
_
x-l-CHFCH-ï-Oîïzl-NH-CHT-CH--CHQ
Viton A
Diallylamine
Presence of lNIgO
300° F1
therefore freetocontinueïthe dehydrohalogenation reac
tion. until decomposed or volatilized from the polymer.
40 mass.
Thev following examples, inwhich parts given are by
~¿ weight, further illustrate the .principlesinvolved inthis.
invention.l Example l> shows.- al representative .solvent
basedlluorinated elastomeric polymer vulcanized inV ac
45 cordance Íwith this invention. However, it isv to he. clearlyv
understood that true liquid polymers are equally operative
Y withinY the scopeofthis invention.
The purpose of the
solvent _is to provide .aliquid'systenrfrom‘the .dry p__oly
mers, which is preferable .forapplication _as fuel tank seal
The reaction was conducted inthe presence of magne 50 ants. Thev subsequentexamples- are presented to further
sium oxide at 300e F.' for 2 hoursäinthe conñned cavity
illustrate this: inventionfso` that those skilled in the art
of- a rubber mold. Although wide temperature ranges ~ may `hetter‘nnderstand theinvention and the» method by
mayy be employed yin ‘ the „foregoing reaction, a tempera
which the same mayv becarried into effect.
tureranger otapproximately 25,09 to 310° F.V is »prefer-red.
Lower temperatureranges. give a reaction `too’ Yslow Ito-be 55
EXAMPLE l
A vulcanizate having the. following composition, was
ofparticular value-while'the higher temperature ranges
in ,excess «of 320° F. giveundesirable cross-linking. Y
prepared. The composition-was‘separated into two parts,
for storage stability, as-shown-in~the- followingiormu
Following _the »formationof Athe reactive. sites, the modi
ñediìluorinated` polymer was vulcanizedïby employing>
polypfunctional cross-linking . agents active toward the 60 lation.
Part A:
modifiedpolymer and capable of reaction at room tem
perature.
Diallylamine ' _______________ __ _______ __
30.00.
10.00
1.00V
Methyl ethyl ketone ____________ __ _____ __ 141.00
l
Part B:
»
Hexamethylene dithiol¿-______ ____________ _.
end of the molecule. A possible explanation ofv the'roorn
temperature vulcani’zation of ‘ the» modiñedîlñuorinated
polymer is exemplified in the followingreactions:
REACTION NO. 2.-CROSS-LINK FORMATION
Partsby weight
Medium thermal carbon .black ___________ _,
Magnesiumoxide ____________________ ____
the present invention are dimercaptansV such` as hexa
methylene dithiolj and glycol dimercapto-acetate; hetero
cyclic amines such as pipera'zine; and alkanediamines
such as'N,N’ dimethylr hexamethylene.` diamine, which are
dir-secondary amines with a methyl group at each opposite
Y
Viton A 1____ ________________________ __ 100.00;
Examples of`cross-linking agentsV suitable in
.
1.50
Trienëarnylamine _____________________ __
0.50
(1 Viton A is a hexañuoropropylenewinylidene-i‘luoride co-.
havinga molecularweight of_about 60,000 and a
70 polymer.
monomer ratio of 30% vinylid'ene Vfluoride and`,70%` hexa~
ñuoropropylene. It is disclosed and more fully.. described in
a' pamphlet entitled -“Properties `of-v a-,blewy Fluoríne-Containing,
Elastomer,” Contribution No. 111 Elastoniers Laboratory,
FOR CASE IV
Organic Chemicals Department, E. Í. du Pont de Neiuoursnnd.
Polymer with `active‘sitesr
Y
_ +Hs-oHz-CHz-CHZ-Cngg-CHZ-CHZ-SH
Company, lInc.)
75
‘
`
The hexañuoropropylene-vinylidene iluorider. copolymer
5
13,041,316
6
is a Water clear, rubbery gum which easily forms a band
on conventional rubber mixing equipment, hereinafter
upon the concentrations of TAA and moisture. In the
referred to as a mill.
lyst; however, normally suñ‘icient moisture is contained by
the rubber. The increase of either of the two catalysts
The rubbery gum is banded on a
mill with two parallel rolls adjusted to provide a rolling
bank in the nip of the rolls. The rear roll rotates faster
than the front, causing a shearing action which mixes the
rubbery gum with the other ingredients. The remaining
ingredients of Part A are weighed using the dry powdered
carbon black to absorb the liquid diallylamine. The di
allylamine is thereby in a less mobile state and incorpo
rates into the rubber at a faster rate With less danger of
loss. The carbon black-diallylamine mix is added to the
revolving band and is immediately followed by the mag
nesium oxide. The mixing action is continued until all
near absence of moisture TAA does not function as a cata
TAA or moisture, will result in an increase of rate of
reaction. The extent of the cross-linking reaction is de
pendent upon the number of active sites and how many
of these are used in cross-linking. Desirable conditions
would provide just enough HMDT to react with all of the
reactive sites.
The properties of the vulcanizate were determined dur
ing the cross-linking period. A portion of catalyzed solu
tion was ilowed out onto a clean steel plate. After it
had reacted for 24 hours at room temperature (75° F.i5 °)
the ingredients are uniformly blended. Uniformity is as
it had suliicient strength to be stripped from the plate.
sured by cutting the band from the mill roll, forming a
A small part of this flowout was placed in methyl ethyl
roll of the rubbery mass and end passing this roll through
ketone. It swelled but did not dissolve, thus indicating
the mill, which is set closer to provide approximately a
that a substantial amount of cross-linking had occurred.
0.005 inch separation. During the above mixing, atmos
The rate of vulcanization at room temperature was traced
pheric conditions prevail except that the mix is cooled by
20 'by measuring tensile strength, percent elongation, hard
circulating cold water through the hollow mill rolls. The
ness and permanent set after break of the specimen. The
blended rubbery mass, Part A, remains “warm to the
test specimens were micro-dumbbells measuring 1/sf' x 5,/5"
touch” from a balance between the cold water cooling
in the constricted portion, with 1/2'" tabs. AThe tests except
effect and the heat generated by the mixing action. The
hardness were performed on a modified Twing-Albert
blended rubbery mass is next heated to drive the diallyl
25 paper tensile tester, used because of its sensitivity to small
amine-polymer reaction, under conditions which prevent
changes in tensile strength. The test data obtained in the
volatilization of the diallylamine. Two hours at 300° F.
above referred to tests are presented in Table I. The
are sufficient to drive this reaction, to completion. The
tensile strength and percent elongation as a function of
volatilization of the diallylamine is prevented by placing
time for the room ltemperature vulcanizate of Example
the blended rubbery mass in a standard A.S.T.M. cavity
1 (Viton A) is displayed graphically in the drawing.
mold which has been liberally coated with a surfactant 30
mold release agent. The mold is then placed in a hydrau
lic press at 300° F. under suiiicient pressure to keep it
tightly closed. Usually, hydraulic pressures of about 500
pounds per square inch of mold area are sufficient. After
a reaction time of two hours Athe pressure is released and 35
the blended rubbery mass is removed from the mold while
Table I
RATE OF CROSS-LINKING OF ROOM TEMPERATURE
VULCANIZING VITONA
Time After Catalyzing, hrs.
are washed from the mass with cold water.
Tensile
.
Elongation Break Set, Hardness,
Strength, ‘ vpercent
percent
p.s.i.
hot. The mold release agent and other foreign materials
.
Shore A
.
The water
73
235
is allowed to evaporate. The removal of foreign materials
such as are usually encountered in a rubber factory are
810 ‘
1,180
1, 470
1, 590
1, 600
not likely to interfere with or prevent subsequent reactions
but their removal insures a product of more uniform
quality. Part A is now refined, as before, by end passing
1,100
1,500
240
2_60
850
80-
20
45
55
790
730
700
500
70
50
40
20
55
57
58
62
on a tight cool mill in order to break up any agglomerates
and to prepare the rubbery mass for rapid' attack by the
solvent. Generally, ten passes are suñicient and result
in a smooth material similar to the original mixture before
the heat treatment. The refined material in the form of a
thin crumpled sheet is weighed and placed in a container
ture. Therefore, test specimens, exhibiting this state of
esters and ketones, tetrahydrofuran and p-dioxane; how
ever, methyl ethyl ketone is readily available and produces
temperature vulcanized elastomers of Example I displayed
a low viscosity solution with Part A.
additional vulcanization occurring at this higher tempera
The test results outlined in Table I indicated a good
state of vulcanization after seven days at room tempera
vulcanization were subjected to high ‘temperature tests.
Micro-dumbbells,.similar to those. used in the tests 0ut-,
with au equal weight of methyl ethyl ketone solvent. 50 lined in Table I were exposed to .TP-4 jet engine fuel in
Other solvents may be used such as low molecular weight
a pressure bomb at 400° F. for 70 hours. The room
f
excellent resistance to the hot fluid and also showed little
As indicated in the above formulation, -Part B is a 55 ture. Similar test specimens were exposed to 500° F. air
physical mixture of hexamethylene dithiol, hereinafter
for 70 hours in a circulating air oven.
'
i
referred to as HMDT and tri-n-amylamine hereinafter
The results of the foregoing high temperature tests are
referred to as TAA. The HMDT was selected in prefer
summarized in Table II.
I
ence to others because it is in a liquid state and has a low
Table 1I
vapor pressure. The TAA was chosen as the catalyst be-` 60
cause it is liquid at room temperature, strongly basic and
AGING RESISTANCE OF ROOM TEMPERATURE VUL
CANIZING VITON A
found to have little eifect in the vulcanizate after high
temperature exposure. The HMDT and TAA are water
like in appearance and are completely miscible in the
, Tensile
Elonga- Hardness, Volume
proportions used.
The vulcanizate was prepared from a uniform disper
sion of Parts A and B in which 1 part by weight of B
was mixed into 141 parts by weight of A. In the presence
Aging Conditions
-
tion,
p.s.i.
Percent
Shore
Change, .
Percent
1, 500
700
57
70Fuel ___________________ -_
1, B00
550
53
+7
leads to a vulcanized elastomer in approximately seven 70
days. The catalyzed solution may be ejected from a pres
Oven .................. ._
1, 450
320
65
,-.173
sure gun used for applying sealants, worked into place by
l vulcanized 108 hours at room temperature.
of moisture a cross-linking reaction takes place which
using spatulas and the like or ñowed out onto a flat sheet
of metal or other surface to evaporate the solvent and
vulcanize. The rate of the cross-linking reaction depends
Original 1 ________________ __
Strength,
________ __
70 Hours at 400° F., JP-4
Hours at 500° F., Air
The above tests indicate that excellent physical proper
ties are obtained by the room temperature vulcanization
system disclosed herein and that a useful fluorinated elas
3,041,316
8
Part B:
tomeric product is produced which fills an urgent need on
Glycol dimercapto-acetate _________________ __ 1.5
high speed aircraft.
Tri-n-amylamine ________________________ __
'
,
While the invention and the advantages thereof have
5 been illustrated by reference to particular materials, it
will be understood that other materials may be used in
Parts by weight
Triñuorochloroethylene - vinylidene fluoride
copolymer _________________________ __ 100.00
Medium thermal4 carbon black __________ __
30.00
Magnesium ., oxide _____ ___ _____________ __
10.00
Diallyl'amine ________________________ __
1.00
their places. Thus in place of the magnesium compound,
which acts as a stabilizer, other lbasic oxides and carbonatos
such as lead or Zinc be used. The medium thermal carbon
black is a reinforcing ñller and may be replaced by other
conventional reinforcing iìller materials such as other
carbon blacks, clay or diatomaceous earth. The medium
Methyl ethyl ketone ___________________ __ 141.00
Palt’B:
Hexamethylene dithiol _________________ __
1.50
Trien-.amylamine _____________________ __
0.50
thermal carbon black is preferred for its general physical
properties. The aforementioned examples indicate the
The vulcanization of this example'and the subsequent
examples, except Example 7, was conducted in accordance
with the» procedure outlined in Example l. -In Example 7
need for abasic catalyst and the presence of moisture in
order to give a greater degree of control over the room
temperature reaction. The catalyst used most often is tri
n-amylamine. The size of this molecule makes it less reac
tive in dehydrohalogenation yet is basic enough to be an
the> 2 hours at 300° F. treatment was done in 3 days at
room temperature. The triiiuorochloroethylene-vinylidene
fluoride copolymer of Example 2, above, is commercially
20
effective catalyst and suliiciently volatile to escape during
available under the trade name Kel-F and comprises 30 to
open air vulcanization.
50'fmolev percent of chlorotriiiuoroethylene, the remainder
remove the mold release agent from the vulcanized poly
mer, which is employed during the hydraulic press treat
ment of the blended rubbery mass may be eliminated by
being Vvinylidene ñuoride.
EXAMPLE 3
Part'A:
100.00.
Medium thermalV carbon
black _____________ __
herein and in the appended claims is employed in a generic
sense to designate synthetic rubbery polymers and copoly
30.00.
Magnesium carbonate--- 20.00.
30 mers which are cross-linkable with polyfunctional com
Diallylamine` hydrochlo
ride __________ __-__-_
pounds capable of reacting therewith so as to effectuate
1.00.
room temperature vulcanîzation whether or not admixed
Ethyl acetate ________ _.. Dependent on desired vis
with pigments, fillers, softeners, peptizers, antioxidants
cosity.
Part B:
and other like materials.
While specific embodiments of the invention have been
described with particularity, it will be evident to those
skilled in the art that the invention is not limited there
to but that various modifications may be made without
departing from the spirit of the invention as defined by
Y
Glycol dimercapto -vace
tate ______________ __ >1.50.
Tri-naamylamine _____ __ Q10-0.25.
VDependent on desired rate
'«
`
of vulcanization.
Acetone ____________ __ As
needed tol make
40
a
, ' homogeneous solution.
EXAMPLE 4
Part A:
y
_
_
___
___ Y100.0()
Medium thermal carbon black __________ __
30.00
Magnesium carbonate _________________ __
Diamylamine _______________________ ___
10.00
1.00
ethylene-vinylidene fluoride which comprises the steps of
mixing said copolymer with a material capable of modify
ing said copolymer by forming chemically reactive sites
thereon, said material selected from the group consisting
Methyl ethyl 'ketone ____ __ _____________ __ 141.00
Part B: N-,N' dimethylhexamethylene diamine___
of ethylamine, propylarnine, allylamine, diethylamine, di
isopropylamine, di-n-butylamine, diamylamine, diisobutyl
amine, di-n-octylamine, diallylarnine, triethyiamine, tri
propylamine, triamylamine and tetramethylguanidine
1.50
EXAMPLE 5
Part‘A:
Y'
Y
VitonA _____________________________ -_ 100.00
Medium thermal carbon black __________ __
Magnesium 4oxide ___________________ ____
Diallylamine
heating the mixture to a temperature of from. about 250°
30.00
10.00
_____ __ ____ __ ___________ __.
to 310° F. to provide said chemically reactive sites,
cooling said mixture to room temperature, mixing
the modified robbery copolymer with a cross-linking
compound selected from the group consisting of hexameth
1.00
Methylethylïketone____`_ _____ ___ ______ __ 141.00
Part B: Piperazine ____________ __ __________ __
PartlA:
'
.
~
ylene-dithiol, glycol dimercapto-acetate, piperazine and N,
1.00
60
EXAMPLE 6
.
Viton A__'_____ ______________________ __ 100.00
Medium thermal" carbon black ______ __`___.. ‘ 30.00
Magnesium',` oxide. ____________________ __
10.00 .
Triamylamine: _________~_ _____________ __
1.00
Methyl ethyl ketone__________________ ___ 141.00.
Part‘B: Piperazine ______ ___ _________ __ ____ __
the scope of the appended claims.
Having thus described my invention, what I claim and
desire to protect by Letters Patent is:
l. A process for the production of a vulcanized rubbery
copolymer selected from the group consisting of hexa
ñuoropropylene-vinylidene iiuoride and 'tritiuorochloro
'
Parts by weightV
Viton A
The use of Water in order to
the use of cellophane as a releasing material or the- use
of a hot air autoclave.
It is to be understood that the term “rubber” as used
Parts by weight
VitonA _____________ __
-
.2
EXAMPLE 2`
Part‘Az:
1.00
Nf ydimethyl hexamethylene diamine and an amine cata
lyst to causeY a reaction therebetween, and then allowing
said reaction to continue at room temperature, thereby
producing a vulcanized rubbery copolymer.
2. A process in accordance with claim 1 wherein said
polymer is hexatiuoropropylene-vinylideneV ñuoride.
'
3. VA process in accordance with claim l wherein said
polymer is triñuorochloroethylene-vinylidene fluoride.
4. A process in accordance with claim 1 wherein saidv
material'is ethylamine.`
«
EXAMPLE 'I
Part A:
L
f
Y
'
Y
Viton'A _____________________________ „100.00
Medium thermal carbon black'. _________ __ 30.00
'
VMagnesium’ oxide _______ __ _________ ___-
Ethylamine. __ ________ „___-____ ______ __
Methyl ethyl ketone ______________ _______ 141.00 -
5. A. process in accordance with claim l wherein said
material is diarnylamine. '
~
6. A process in accordance with claim l wherein said
materialis triamylamine.
7. A processV in accordance'rwith claim 1 wherein said
material Yis diallylamine.
3,041,316
10
8. A process in accordance with claim 1 wherein said
period of time suiTìcient to produce a vulcanized copoly
material is diethylamine.
lmer.
9. A process in accordance with claim 1 wherein said
compound is hexamethylene dithiol.
References Cited in the tile of this patent
UNITED STATES PATENTS
10. A process in accordance with claim 1 wherein said
compound is glycol dimercapto-acetate.
11. A process in accordance with `claim 1 wherein said
compound is piperazine.
12. A process in accordance with claim 1 wherein said
compound is hexamethylene diamine.
13. A process for the production of a room tempera
ture vulcanized hexañuoropropylene vinylidene fluoride
copolymer which comprises the steps of mixing said co
polymer with diallylamine in order to modify said copoly
mer by forming chemically reacting sites thereon, heating
10
2,423,032
Le Beau ______________ __ I une 24, 1947
2,446,984
Rogers etal ___________ __ Aug. 10, 1948
2,662,874
2,793,200
Brown ______________ _.. Dec. 15, 1953
West ________________ __ May 21, 1957
Ayers et al. ___________ .__ Dec. 1, 1959
2,915,481
OTHER REFERENCES
Moran et al.: “Safe Processing Curing System for Viton
Fluoroelastomers,” Ind. and Eng. Chem., vol. 51, No. 7,
said mixture to a temperature of about 300° F., cooling
said mixture to room temperature, mixing the modified
July 1959, pp. 831-832.
copolymer with hexamethylene dithiol and a triamylamine
October 1959, Elastomers Chemical Department (only
Eubank et al.: “Viton in Mechanical Goods,” BL-360,
Catalyst to cause a reaction therebetween, and then allow
page 3 relied on), E. I. du Pont de Nemours and C0.
ing said reaction to continue at room temperature for a 20 (Inc.), Wilmington 98, Del.
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