Note: Descriptions are shown in the official language in which they were submitted.
~3~33~
27,738
VULCANIZABLE SYSTEM FOR THIODIETHANOL ELASTOMERS
Background of the Invention
Elastomers, based on the condensation of a major
proportion of thiodiethanol with one or more aliphatic
diols containing a sulfur-vulcanizable double bond, are
described by Aloia, U.S. Patent 3,951,927; Chang etal.,
U.S. Patent 3,985,708; Chang, U.S. Patent 4,000,213; and
Li etal., U.S. Patent 4,028,305. Heretofore, application
oE conventional sulfur vulcanization systems, e.g., sulfur,
zinc oxide, benzothiazole sulfenamides, thiuram sulfides,
mercaptobenzothiazole, and the like, to the vulcanization
of these elastomers has been less than satisfactory. Zinc
oxide has heretofore been considered to be essential to
the vulcanization of unsaturated elastomers with sulfur.
In the vulcanization of thiodiethanol-based elastomers of
the invention, conventional sulfur-vulcanization systems
containing zinc oxide result in a fast cure, but the vulcan-
ized elastomers exhibit poor heat ageing as manifested by
high compression set and poor continuous stress-relaxation.
However, when zinc oxide is omitted from the cure system,
the cure rate is impractically slow. All of these factors
indicate that there is a need for a vulcanization system
to vulcanize thiodiethanol-based elastomers.
In order for an elastomer to achieve commercial
~ : . .
-~ success, lt must be vulcanlzable to useful products with
an efficient, practical vulcanization system. It is an
object of the invention to provide useful vulcanized
products from thiodiethanol-based elastomers, and to pro-
: A ~
., . . . - . . , ., ` . . , . ( . .
~L~3~;33~
vide elastomers exhibiting significantly impro~ed aged
properties, such as compression set.
Summary of the Invention
The present inventio:n provides a novel vulcaniza-
tion system for thiodiethanol-based elastomers, comprising
sulfur and an aliphatic linear, branched chain or cyclic
polyethyleneamine, or mixture thereof, or a dissociable
organic salt thereof.
Descrip~ion of the Invention Including Preerred Embodiments
The aliphatic linear, branched chain or cyclic
polyethyleneamines which are useful in the vulcanization
system of the present invention range from relatively simple
polyethyleneamines, which are represented by the formula:
H ~ IIN-(C~l2)2 ~ NH2 (I)
n
wherein n is an integer from 1 to about 10, to complex re-
action products of ethylene dichloride and ammonia, which
20 boil above the boiling point of diethylenetriamine (206.7C),
to dissociable organic salts of polyethyleneamines produced
by reaction thereof with acids having a dissociation constant
less than about 10 3, or mixtures of any of the above
materials.
Polyethyleneamines repxesentative of the above
formula (I) include:
ethylenediamine
diethylenetriamine
triethylenetetramine
tetraethylenepentamine
pentaethylenehexamine, and the like.
The complex polyethyleneamine reaction mixtures
contain linear, branched chain and cyclic structures which
include, for example, the following:
'..;
: . -
'
.' . ': ,
~3~3~
-- 3 --
2 2 2 C~2C~2 NH-C5~2C~2-NH-c~l2c~2-NH-c~2c5~2-NH
~ t~lethylcllel~examine
2 ~ ~2 Nll C~l2c~2-lN-cll2cl~2-Nll~cH2cH2-NH2
C~
icl~2
N112
~ diaminoethyltriaminoethylamine
2N-cll2cll2-N-c~l2c5l2-NH-c~l2cH2-NH CH2CH2-NH2
CE12
C~2
Nli2
Unsy~metr_c ]. diaminoethyltriaminoethylamine
H2N-C~2C~12~ ~ CH2CH2-N~12
N CH2cH2-N
H2~l-cll2cEl -- CE12CH2- NH2
Symmetrical diaminoethyltriethylenetetramine
H2N CH2CE12 Nll-C1~2C~32-N ~ N-CH2CH2-NH-cH2cH2-NH2
Symmetrical diaminoethyldiaminoethyl piperazine
~ C112C~I2 ~ - --- -_- .,. ~.~,.
2N-cll2cll2-N N-C112C512-NII-C112CE12-NII-CH2CE12-N112
C112CI~2
:: :
~3i;3 35~
-- 4 --
Unsymmetric~l ~liaminoethylc1iaminoethyl piperazine
~ Cll?C112
HN N(~ 2C1-12-N11t-3 C~12CH2-NH2
~ C112C~12--
Pip~raz.inocthyl triethylene tetramine
_C~12C112~N-C112C112 N11 C12 2 2
C~12
cil2
I
N
Cl-12 Cl~l2
1112 C}12
~ N
: 11
(N-p~erdzinoethyl)triethylene tetramine
. 20
'' ~ Cl'2C112~ CH2C~2\
HN N-CH2CH2-~11-Cll2c~l2-N\ N-~
2 2 CH2CH2
ispiperazinoethylamlne
~, .
2C1~2 \ / 2 2 \
H2N-C112C112-N j N CH?.C~12 j NH
. C112c}12 C~12C112
~minoethyl diperazinoethane
,~ ", , j
In addition tG the linear, branched chain and
cyclic polyethyleneamines, or~anic salts thereof, which
~: - dissociate under vulcani2ation conditions to liberate the
free amine, may also be used.
-
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Useful organic salts are those which are formed
from acids having a dissociation conskant less than about
10 3, and including salts of aliphatic carboxylic a~ids,
especially those of 2-18 carbon atoms, carbonic acid, carba-
mic acid and the like. Particularly useful salts are thefatty acid salts, e~g., the stearate. Useful salts also
include the condensation products of polyethyleneamines
and the aforementioned fatty acids, for example stearic
acid, such as diethylenetriamine-stearic acid condensate.
The vulcanizable thiodiethanol-based elastomers
useful in the present invention are preferably those dis-
closed in the aforementioned patent to Aloia and Chang et
al ('708).
Specifically, the vulcanizable elastomers of thio-
15 diethanol is a polymer represented by the formula
(II) H ~ OG ~m OHwherein fOG~ comprises randomly alternating structural units
selected from
(E) structural units (III) and (IV)
(III) fC2H4SC2H4
(IV) ~OR~
or ~F) structural units (III), (IV) and (V)
(V) ~OR'~
25 wherein R is one or more radicals remaining on removal of
two hydroxyl groups from:
(a) saturated aliphatic, linear, branched chain
or cyclic diols, or
(b) aliphatic linear, branched chain or cyclic
diols containing external unsaturation having
an allylic hydrogen atom, wherein R' is one
x or more radicals which remain on removal of
two hydroxyl groups from a diphenolic compound,
said polymers comprising structural units (E)
and (F) being characterized in that:
(1) m is an integer sufficient to provide in
said polymer an average molecular weight
~ .
.
~3~339
- 6 -
of at least 8000;
(2) the molar ratio of (III) to (I~), when
said polymer comprises structural units
(E), or the molar ratio of (III) to the
total of (IV) and (~) when said polymer
comprises structural units (F), being not
less than 1:1 and
(3) they contain from about 1 to 10 mole per-
cent of said diol (b) based on the total
of all units (III), (IV) and (V) present
in said polymer.
The vulcanization system of the invention compri-
ses sulfur in an amount of from about 0.3 to 3,0 parts by
weight per hundred parts of elastomer, preferably 0.3 to
15 2.0 parts, same basis. The polyethylene amine may be used
in an amount of from about 1 to 6 parts thereof per 100
parts of elastomer, preferably from about 2 to ~ parts, same
basis
In addition to sulfur and the polyamine compound,
20 the vulcanizable elastomer composition may contain other
conventional rubber compounding ingredients, such as fillers
and reinforcing agents, e.g., carbon black, precipitated
,~ hydrous silica, titanium dioxide, calcium carbanate, calcium
j~ silicate, and the like; calcium oxide or calcium stearate
25 (or other fatty acid salt) to neutralize acid catalyst resi-
dues in the elastomer; processing aids, such as sorbitan
monostearate or stearic acid; sulfur-donating compounds;
mercaptobenzothiaæole; sulfenamides; thiuram sulfides, and
the like, without departing from the scope of the invention.
~` 30 The ~ulcanizable compositions may be prepared by
conventional rubber compounding techniques, using a two-roll
rubber mill or a Banbury mixer, at temperatures of 300F
The compositions are vulcanized at similar temperatures,
preferably about 3~5-350F for about 15 to 60 minutes and,
~ 35 optionally, post-cured for periods of time to de~elop
;~ full cures.
.,
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The following examples are set forth for purposes
of illustration only and are not to be construed as limi-
tations on the present invention. All parts and percentages
are by weight unless otherwise specified.
S Example 1
An elastomeric copolymer of 80% thiodiethanol,
15% isopropylidenebisphenol and 5% trimethylolpropane, mono-
allyl ether was compounded as follows:
Part~y Weight
10 Elastomer 100
Carbon Black 60
Calcium oxide 3
Sorbitan monostearate 2
Sulfur 1.5
15 Tetramethyl thiuram disulfide 1.5
16~.0
To separate portions (168 parts) of the above formulation
was added:
A - B - C
. . . ~ . ~
~, 20 Zinc oxide 5,0 - -
Mercaptobenzothiazole 1.5 2.0 2.0
Polyamine D* - - 4.0
*Mixture of aliphatic and cyclic polyethyleneamines boiling
above 340~C
~, 25Each of the compositions A thru C was cured for
~,~ 60 minutes at 330F and then post-cured for 16 hours at
120C before testing.
Rheology of the compositions was studied using a
Monsanto Oscillating Disc Rheometer operating at 330F.
30Rheometer
~ A B C
; Max. cure rate 6.5 0.1 1.45
(inch - lbs./min.)
Max. torque (inch - lbs.) 40.5 - 87
35 Tor~ue after 15 minutes40.5 g 35
(inch - lbs.)
- Stress-strain properties of the cured compositions
:
-, ~; . - :
,
: , ,
~3~33~ -
using an Instron tester were as follows:
Tensile, psi 1100 750 1660
Elongation, % 220 375 300
Hardness~ Shore "A" 71 60 78
Continuous stress~relaxation studies were made to
measure the thermal stability of the compositions. The
elastomer samples were tested on an autographic stress-
-relaxometer consisting of load-sensing elements, a means
for extending and maintaining the specimens at a constant
10 elongation, and a circulating air oven, The oven tempera-
ture was maintained at a temperature of 150C i 0.1C and
the samples extended to 5 + .05%. The decrease in modulus
with time is recorded automatically. Data relating to the
relative thermal stability are obtained from plots of f(t)/
15 f(0) versus log time, or log f(t)/f(0) versus time, where
f(t) and f(0) are the forces at time t and t - 0, respec-
tively, required to maintain the sample at a given extension.
The data are reported as ~50, which represents the time at
150C that is required for a sample to degrade to a value
20 equal to 50~ of the initial stress, which is a measure of
the amount of degradation experienced by the specimen.
Continuous Stress-~elaxation
A B C
~ 50, minutes 350 - 2450
The data illustrate that Composition A, which re-
- presents a conventional sulfur vulcanization system, pro-
vides a fast cure rate, but exhibits poor thermal stability
compared to Composition C which is many times more stable
and which exhibits a good cure rate and develops good mech-
30 anical properties. Composition B demonstrates that a very
poor cure is obtained without zinc oxide in a conventional
vulcanization system.
Followin~ the procedure of Example 1 an elastomeric
35 copolymer of 90% thiodiethanol -5% diethyleneglycol -5% tri-
methylolpropane, monoallyl ether was compounded as follows:
,
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. ;.
. -......... .. :, :
,, ;, : ~ .,
.~ !
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g
Parts by W~ t
Elastomer 100
Carbon black 50
Antioxidant* 2
5 Tetramethyl thiuram disulfide 1.5
Mercaptobenzothiazole 2.0
Sulfur 1.5
Calcium stearate 3.0
160.0
10 *Di-~-naphthyl-p-phenylenediamine
To separate portions (160 parts) of the above formulation
was added:
D E F
Polyamine D (See Example 1) 2 3 4
15 The compositions were cured for 30 minutes at
330F and post-cured for 16 hours at 120C. Properties
were as follows:
Monsanto Rheometer @ 330F
D E F
20 Max. cure rate 1.4 2l1 2.4
Max. torque 80+ 95+ 95
Torque after 15 minutes 39 S1 51
Instron Stress-Strain ProPerties
- - --
D E F
25 Tensile, psi 1645 1715 1490
Elongation, % 370 300 270
Compression Set, % 89 62 41
(Method B- 22 hrs. at 120C)
Continuous Stress-Relaxati n
30 rS0, minutes 125 425 1200
The data illustrate that good cures are obtained
using 2 to 4 parts per hundred of Polyamine D and that the
higher concentrations tend to provide increased thermal
stability, as mani~ested by improved compression set and
stress-relaxation.
Example;3
An elastomeric copolymer of 90% thiodiethanol - 5%
: . :
'~
:
i33~
-- 10 --
diethyleneglycol - 5~ trimethylolpropane, monoallyl ether
was compounded as follows:
Parts b
Elastomer 100
s Carbon black 50
Clacium stearate 5
Sulfur 1.5
Mercaptoben~othiazole 1.5
; Tetramethyl thiuram disulfide 1.5
159.5
Separate portions (159.5 parts) were compounded
with the following (all at 4 parts per hundred of rubber
of active material).
G H J K
15 Triethylenetetramine 4 _ _ _
Tetraethylenepentàmine - 4 ~ -
Polyamine D** (50% on silica) - - 8
Polyamine H* - - - 4
*Complex polyethyleneamine reaction product boiling a~ove
20 340C and containing 24-28-~ by weight of diethylenetriamine
** See Example 1
The compositions were cured for 30 minutes at
330F and post-cured for 4 hours at 120C.
Torque (inch~pounds) was measured at 330F after
; 25 30 minutes using a Monsanto Oscillating Disc Rheometer.
This is an indication of the extent of cure of the compo-
sition.
G H J K
Torque after 30 min~ 61 60 66 66
The stress-strain properties, obtained on an In-
stron tester, were as follows:
Tensile, psi 1520 1550 1500 1540
Elongation, ~ 490 455 470 435
Hardness, Shore "A" 74 76 75 77
35 Compression Set, % 34 33 37 27
(Method B: 22 hrs~
- at 120C)
.
, :, : : .'... . :
: , . . .
.
33~3
The data illustrate that good cures are obtained
using various polyethyleneamirles with sulfur and that the
cured compositions exhibit good ageing resistance, as mani-
fested by low compression set.
Example 4
An elastomer of 90 percent thiodiethanol - 5~
diethyleneglycol - 5% trimethylolpropane, monoallyl ether,
was compounded as follows:
Control K
Elastomer 100 100
Carbon black 50 50
Calcium stearate 5 5
Sulfur 1.5 1.5
15 Mercaptobenzothiazole 1~5 1.5
Tetramethyl thiuram disulfide 1.5 1.5
Triethylenetetramine stearate - 4
The compositions were cured for 60 minutes at
330F. Stress-strain properties are as follows:
20 Tensile, psi under 1530
Elongation, ~ cured 510
Hardness, Shore "A" ~ 67
Example 5
The procedure of Example 1 was again followed
except that the elastomer was prepared from thiodiethanol
(95 parts) and the monoallyl ether of trimethylolpropane
(5 parts). Similar results were achieved.
Example 6
The procedure of Example 4 was again followed
except that the monoallyl ether was replaced by 3-cyclo-
hexene-l,l-dimethanol. Similar results were achieved.
Example 7
When the procedure of Example 4 was again followed
except that the diethylene glycol was replaced by isopropyl-
idene bisphenol, similar results were achieved.
The procedure of Example 1 was again followed
. - ~
~13~33~
~ 12 -
except that Polyamine D was replaced by diethylenetriamine
carbonate. Excellent results were observed.
ExampLe
Following the procedure of Example 8 except that
the carbonate was replaced by the corresponding carbamate,
the results were comparable.
,
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