Note: Descriptions are shown in the official language in which they were submitted.
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- 1 - 41WC-2043
HEAT RESISTA~T ETHYLENE-PROPYLENE RUBBER WITH IMPROVED
TEN.S ILE PROPERTIES AND INSULATED CONDUCTOR PRODUCT THEREOF
B~CKGROUND OF THE INVENTION
The present invention relates generally to
compositions of ethylene-propylene rubber adapted or use
as insulation compositions and to conductors insulated
with such compositions. More specifically the in~ention
relates to an ethylene-propylene composition having a
desired and needed cornbination of properties as an
insulator including improved ten.sile proper~ies in com-
bination with heat resistant properties and to insulated
conductors having such composition orming the insulation
thereo~.
It is well-known that polymeric compositions,
when used fcr insulating purposes, are used in many
different environments including temperature en~ironments,
and that no one composition is suitable for all uses. To
a large degree the use, which is made of an insulating
~: composition, places important requirements on the compo-
sition and there are many s~andards which have been
established in ~he industry, and by standards organizations
such as the Underwriters Laboratories,ASTM,IPCEA, for wire
insula~ion compositions. In all of the standards whieh
are established there is a close correlation between the
requirements of the insulated composition and of the
insulated wire or cable and the use to which the composi-
tion or cable is to be put. Accordingly, it is well-
established in the wire and cable ~echnology and indus~ry
that direrent combinations o~ ~nsulating properties and
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41WC-2043
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physical properties are required in different cables where
such cables are to be used in applica-tions having particular
criteria such as temperature criteria, atmospheric
criteria, voltage criteria and other measurable criteria
of compositions and of cables.
Another important criteria of insulating
compositions, and o~ cables formed with such composltions,
is the economic criteria or more specifically the ability
to prepare such compositions and cables at reasonable costs.
In some other cases a composition can be prepared
in a bulk form, or an extruded form, or a sheet form and
have good properties but the same properties are not
retained when a product is put on a conductor to form a
wire or cable. For still other compositions the process
; 15 by which the material is applied to a conductor may give
deleterious results in the finished product or may make
the application process uneconomical.
Compositions which have been prepared in the
past of ethylene-propylene rubber and which have very
` 20 desirable heat resistance and other properties for use
as wire and cable insulation are disclosed in U.S. patents
4,069rl90, dated January 17, 1978 and ~,133,936, dated
January 9, 1979, both patents being assigned to the same
assignee as the subject application. As is brought out in
~; 25 these patents the insulating composition and the cable made
with the insulating composition has a combination of proper-
ties, values of which are set forth in the data included in
-- the patents. Further, the composition is made up of a number
of ingredients which are set forth in range values also
explicitly included in the data of the preferred embodiments.
One of the desirable properties which is achieved
in the compositions and product of the U.S. patents referenced
above is heat resistance.
In developing the composition, the heat
resistance needed was not as great as that of silicone
rubbers which had been used in prior compositions but the
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overall combination of propertles including heat
, resistance was achieved at a cost substantially below
: the silicone r~bbers. In other words the newer composi-
. tions of the reference patent:s were substituted ~or
; 5 silicone rubber compositions previously employed as heat
resistant wire insulation compositions.
One of the criteria in achieving heat resis-
tance as is brought out in t~le patents is the avoidance
of cracking and deterioration of the composition when
employed at the elevated temperatures. The heat resistant
properties of the composition of the reference patents are
attributed to a number of factors. In this regard it is
important to appreciate that a COTnpOSitiOn made up of
such a combination of materials achieves a combination
of properties based on the proper blending and curing of
the components as prescribed in the patent. With regard
to the heat resistant properties one of ~he elements or
components which contribute.s to the development of the
heat resistant property, but not the only component, is
the inc].usion of the antioxidants in the overall combina-
tion in the ranges set forth in the reference patents.
Other components are deemed significant in achieving the
overall beneficial combineti~n of properties of the
composition both by itself and also as a wire insulation.
However, with reference to the antioxidant the combina-
tion o.~ ingredients includes the antioxidant which is
present in order to inhibit such reactions at elevated
temperatures as cause deterioration of the composition
and product. As is evident from the text of the prior
art patents,there is also present in the overall composi-
tion a peroxide material which is added according to the
prescribed method to provide the cross-linking as set out
- in the patent. Such cross~linking gives the compositions
of the refe.rence patents some of their higher temperature
properties. It has generally been understood with
respect to higher temperature compositions formed by
peroxide curing that the presence of the peroxide and the
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4lWC-2043
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presence of the antioxidant material can be antagonistic
to each other in the sense that their functions in the
overall composition are for inconsistent purposes. More
specifically the peroxide material is present to include
cross-linking. By contrast the antioxidant material is
present as generally contemplated to l'imit or inhibit the
post-cured oxidation of the composition at the elevated
temperatures at which it is used.
With reference to the aforementioned U.S. patents
10' 4,069,190 and 4,133,936 the compositions and products are
referred to as heat resistant and this heat resistance is
indicated in the statement of the background of the in~en
tion to pertain to the loss of elasticity or to increase
embrittlement upon exposure to temperatures above ambient
temperatures. As stated in the patent: "The deteriorating
effect of heat on elastomers has prompted continuing efforts
-~, and the use of a variety of remiedal measures to improve
their resistance to heat, such as the development and use of
antioxidant or agents which block the action o~ oxygen or
free radical forming ingredients~ and new compound
formulations."
It is well known that different applications
for wires require that the wires have different sets of
~,~ properties depending on the application to be made of the
' 25 wire.
For motor lead and apparatus lead applications
the particular combination of properties which is required
include a basic heat resistance of the insulation compound.
For such applications a preferred combination includes
an economical heat resistant, tough, fle~ible insulation
with a moderate tensile strength and also with good tear
resistance and good abrasion resistance. For such motor
lead and apparatus lead applications the insulation
jacket is integral in the sense that there is no outer
jacket applied over the insulation jacket having these
properties. In other words there is only a single
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insulating jacket appli.ed and that jacket is the one
~ which must have the desirable combination of properties
;~ recited above. Of course, the composition must also have
a needed or standard set of electrical properties.
In general heat res,istant properties o~
polymers may be increased by cross-linking of the
i~ polymer molecules. Such cross-linking can be accomplished
for some polymer syste~ by use of thermally unstable
peroxide compositions. However the aging properties of
polymer systems at high temperature may be adversely
affected by presence of peroxide curing agents and anti-
oxidant compositions ha~e been added to polymer syste~ls
to inhibit or overcome such deleterious effects.
Mechanisms for antioxidant use are discussed
in the following exerpt from a booklet entitled "Handbook
On Antioxidant And Antiozonants" for rubber and rubber
like products published by Goodyear Chemicals. Two
exerpts from page 11 of th~ booklet are as follows:
"~y adding an ant:ioxidant of one or more typesS
the oxidation of polymers can be interrupted
and the degradation slowed down considerably.
There are two ways this can usually be accom-
plished. The first way is to introduce an
antioxidant that will eliminate peroxides
before they can do damage.
R00 ~ AH ~ ROOH -~ A
R00 ~ A 3 ROO~
The antioxidants which will do this ar~ the
phenolics and the aromatic amines. The amines
include most of the staining antioxidants and
the antiozonants.'
* * * * * * *
"Another way of disrupting the oxidative
action is ~o des~roy the hydroperoxides
before then can cause problems.
ROOH ~ AH ~ Stable Products
Two ~ypes of antioxidants do this. They are
~ lWC-2~43 ''
the phosphites and the thioesters~ The mos t ~,'
common phosphi~e .i.s ~risnonylphenylphosphite
and a well known thioester is dilaurylthio~
dipropionate, frequently called simply ..................... '',
DLTDP.
The thioesters are most widely used in ',;,,:
plastics, principally polyolefi.ns, while the
phosphites are used in the rubber industry
almost exclusively as emulsi,on polymer .,;
stabilizers. Both phosphite and thioesters
are affected by vulcaniza~ion systems, losing ,,'
most of their activity. ,',
Often an antioxidant from each of the two 's
groups is used in a polymer to form a :'",
synergistic combination. By combining the , ,-
two, they can work hand in hand to destroy ;,'
both types of destructive radicals. ,
A~tually, such a combination almost always
w ~rks much better than simply increasing ,''
t Le concentration of a singl.e antioxidant.".
O~JECTS OF THE INVENTION
It is accordingly one object of the present ~"
invention to provide a wire product suitable f~r use ''
; as a motor lead or a~paratus lead wire. i~ !
Another object is ~o provide an i~proved j '
insulation composition for disposition and curing on a '
conductor to form a motor lead type of wire.
Another object is to provide an impr~ved cured ! ~ i
insulation composition for use on motor lead t~pe ~ ; '-
30 conductors. , ~,
Another object is to provide a novel ,rubber
composition having a novel combinati~n of properties ,';
including, a resistance to deterioration of such properties
at high temperatures.
It is another object of thijs invention to
provide a novel curable composition a~d products thereof
which have an improved combination o~ proper~ies for use
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in hi~her temperature insula~ion applica~ions and which
when curedhave a desirable cornbination of physical and
~' electrical properties.
~: It is another object of this inven~ion to pro-
vide A new and improved electrical conductor having an
insulation wi.th a novel combination of physical properties
and having apt electrical properties.
It is another object of this invention to
provide an ethylene-propylerle rubber composition possess~
ing a novel combination of physical properties which
make it particularly suitable for use as an ele~trical
insulation for motor lead type conductors.
Other objects and advantages of the invention
will be in part pointed out and in part apparent from
lS the description which follows.
S~IARY OF THE INVENTION
The invention comprises a novel rubber compo-
sition o~ a specific combination of compounded ingredients
and proportions thereof which has a significantly
improved combination of physical properties for use as
an insulation of motor lead type of wlre together with
satisfactory other physical and electrical properti.es.
The novel rubber composition of this invention is
composed o an essential combination of ethylene-
propylene rubber, chlorosulfonated polyethylene, zincoxide, talc, carbon black, vinyl silane, antimony oxide,
amine antioxidan~, imidazole antioxidant, peroxide curing
agent and curing coagent, and can include other optional
components which enhance the overall at~ributes of the
rubber composition. The invention additionally includes
electrical conductors insulated with the novel ethylene-
propylene rubber compound.
BRIEF DESCRIPTION OF ~HE DRAWING
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,rhe figure comprises a perspective view o a
section of an electrical conductor insulated with the
novel and ~mproved rubber composition of this invent~on.
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DEl'AILED _~,S RtPTION C~ A r~E~ D EMBODIMENT
This inven~ion specifically consists of a
~! novel combination of compolmded ingredients and
relative proportions thereoflwhich in total produce an
elastomeric composition having an outstanding combina-
~, tion of physical and electrical properties including
~' stability and resistance to deterioration upon subjection
to elevated ~emperatures over extended periods sui~able
for use in a motor lcad or apparatus lead wire,
The rubber cornposition of this invention com-
prises the combinatlon, in approximate parts by weight,
consisting essentially of:
Ethylene-propylene rubber 100
Chlorosulfonated polyethylene 3 - 10
lS Zinc Oxide 15 30
Talc SO ~ 125
Vinyl silane 0.5 - 3
Carbon black 10 - 32
Antimony oxide 3 - 10
20 Amine antioxidant 1 - 4
Imidazole antioxidant 0.~. - 4
Peroxide curing agent 2 - 8
Curing coagent 2 - S
The ethylene-propylene rubber component com-
p ises ethylene-propylene copolymers and terpolymers of
typical commercially available compositions constituting
about 25 to about 75 parts by weight of ethylene monomer
copolymerized with about 75 ~o about 25 parts by weight
of propylene monomer. Terpolymers of ethylene-propylene
include those commercial rubbers produced by the copoly-
merization of ethylene and propylene together with minor
proportions of dienes such as ethylidene norbornene,
dicyclopen~adiene and 1,4-hexadiene.
Talc~ of course, consists of a well-known but
distinctive mineral form of hydrated magnesium silicate.
It is preEerred that the talc component of this invention
be of the plate type in its physical form.
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41WC-2043
_ g _
In practicing this invention two special
categories of antioxidant must be employed in combination
to achieve the combination of desired physical and
electrical properties in insulation material of the
invention. The first category is the amine antioxidants
and this category is exemplified by reaction products of
diphenyl amine and acetone. The second category is the
imidazole antioxidants and this category is examplified
by a zinc salt of 2-mercaptotolylimidazole.
Peroxide cross-link curing agents for the
ethylene propylene rubber compound of this invention
comprises the free radical forming organic peroxides such
as tertiary peroxides characterized by at least one unit
of the structure
C C
C - C 0 - 0 C C
C C
which is activated by its decomposition at temperatures
in excess of about 295F. The ufse of such peroxides in
cross-linking polymers is described in detail in U.S.
patents 2,888,424, Precopio et al, issued May 26, 1959;
3,079,370, Precopio et al, issued February 26, 1963; and
3,214,422, Mageli et al, issued October 26, 1965. A
commonly used and preferred curing agent for this invention
is dicumyl pero~ide.
The use of a peroxide curing coagent in the
cross-linking of the novel composition of this invention
is required to increase the efficiency of the cure in
accordance with the technology in this art. Apt curing
coagents include, for example, polybutadiene homopolymer.
The following comprise examples illustrating
specific embodiments of this invention and demonstrating
their improved combination of properties in rela~ion to a
control comprising a prior art composition.
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The cornpounds of th~ control and each example
of this invention were all p~epared in an identical
manner, comprising first admixing all components, exc ep k
the peroxide curing agent and ouring coagent, in a
Banbury for about 10 minutes while heating to about
300F. After cooling to room temperature, the curing
eoagent was added to the admixture on a two roll rubber
mill. This was followed by the addit:ion of the peroxide
by dispersal through the other in~redients.
The following comprise examples illustrating
specific embodiments of this invention in rela~ion to
control compositions and ilLustrating by comparison of
the embodiment~ with the control examples the benefits
and advantages made possible through the invention. l~e
improvements which are made are not confined to improve-
ment of a single property and accordingly cannot be
measured by a single criteria of the composition or
cable. Rather, the lmprovements involve beneficial
chang~s in a combination of properties and particularly
those combinations which are needed and beneficial for
the favorable performance of -the composition and cable
in the use applications for which they are prepared.
; One such cormnon use of these materials and cables is in
the motor lead and apparatus lead applications where
cables prepared pursuant to this invention have shown
superior performance and ha~e solved some of the problems
which are particularly associated with such end applica-
tion use.
The compounds of the control examples listed
in Tables I, II, and III and of each listed test example
of this invention are all prepared in an essentially
identical manner. The preparation invol~ed first admixing
all of the components excep~ the peroxide curing agent
and the curing coagent in a Banbury mill for about ten
minutes wh:ile heating to about 300F. After cooling to
room temperature, a curing coagent was added to the
admixture on a two roll rubber mill followed by the
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~ lWC-2043
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addition of the peroxlde. The addition was made so as
'~ to disperse the coagent and the peroxide through the
other ingredients,
A firs~ set of test and control compositions
was made and the combinations of the ingredients of
these composi~ion.s and some of the ~est properties found
are listed in the following chart ldentified as TABLE I.
All amounts are given in parts per lOU parts
of base copolyrner and/or terpolymer.
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41WC-2043
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'i ~ 14 - 41WC-20~3
r'~ Samples of each composition of the controls
.;. and of the test exLInlples of thls invention were prepared
;~ from the Banbury into sheet form having a thickness 4f
' approximately 1/~l" al.though ~he thickness is not
.;, 5 critical in rela~ion to ~he propertles of the material
which result from processing o~ the sheet material. The
only requiremen~ is that the t~ickness of the sheet
material be greater than the thickness of a platen in
which the sheet is to be pressed at an elevated tempera-
ture. A quantity of the sheet mater;al is cut and
wei~hed and it is then placed in a heated platen having
width and length dimenslons greater than that o the
sample of cut sheet materlal but which has thickness
dimensions thinner than that of the cut sample of sheet
material.
The platen is preheated at the time of intro-
duction of the cut sample to a temperature o 350F. The
platen is premounted in a press which is then closed to
appl.y a pressure to the composition and to ~t least
partially cure the composition, to exclude air from the
composition and to compact it to a final thickness of
approximately 80 or 85 mils and a pressure across the
members of the platen of approx. 400~-5000 psi. The
total time during which the sample remains under pressure
in the platen at 350F. temperature is 45 minutes.
The platen press is opened to release and
remove the pressed sample. The prepared test sample is
allowed to cool to room ~emperature. Normally a waiting
period of at least four hours follows the press heat
curing of the composition in the platen before the
physical tests are performed. The three physical pro-
perties, namely ~ensile s~rength, per cent elongation
and 200% modulus, are measured in the units as indicated
in Table I. The measurements were made for the cross-link
cured compositi.on of each control and of the test sample.
Wi~.h regard to the results reported in Table I
it is evident ~hat there was also an accelerated heat
.
- lS ~ ~lWC-2043
! ~ging test conducted for 18 hours in an air oven at
200C. In this test the ends of a 4" x 1/2l' strip
. which had heen subjected to the heat a&ing te~t were
bent together. The measured values obtained were as set
out in Table I. From the data which is presented in
Table I, it is clear that strikingly different physic~l
property values were obtained Eor the example ID 80-87C
as compared to those obtained for ~.he other test samples.
Sample ID 80-87C is ~he only one of the four test samples
listed in Table I which contain Vulkanox ZMB-2 in
addition to ~ . L. E . -25 antioxidant materi.al.
With further regard to the results pre~ented
in Table 1, it will be realizecl that one of the principle
problems which was being addressed in undertaking the
studies, the results of which are reported in Table I, was
the problem of improving the tensile strength and related
properties of the resulting cured composition. The tensile
strength properties tested are really those which refer to
th~ tensile strength property of the insulation for use on
a wire, such as a motor lead wire. The insulation compo-
sition is prepared for deposition as an insulating layer
on a wire as an ~mcured composition. After deposit on
the wire the composition is cured.
Experience prior to this invention has shown
that there are numerous compositions for use or cure and
that such prior art compositions had a highly desirable
set of properties as an insulation for motor lead wire or
for si.Dilar applications. However, it has also been known
that the combination of properties desirable for such
applications might be improved with particular regard to
the tensile streng~h and related properties of the insula-
tion. Referring to Table I and comparing the results of
the tests of the properties of the co~positions reported,
an attempt was made to improve the tensile strength by
increasing the amount of the terpolymer present so
that the amount of the EPDM rubber and particularly
the Nordel 1040 was increased by 25 parts with a con-
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16 - 41WC-20~3
comi~ant decrease in the Vistalon copolymer of 25 parts.
The results of the test Il) 8()-87A which had the 'higher
concentration of terpolymer show that the tensile
property was not improved and also there ~laS no improve-
ment in the modulus. Accordingly this approach towardimproving the tensile strength property was essentially
unsuccessful. It will be noted that the other components
of the ID 80-87A composition are identical with those of
the control 1852 -19-07.
With regard to the test sample ID 80-87B it is
noted from Table I that the Vistalon, Nordel and other
ingredients are the same as those given for the control
1852 -19-07 but that a change was made in the peroxide
employed from the Di Cup T to Di ~wp R. The amount o
Di Cup R used in 87B is slighly less than the amount
of Di Cup T used in 87A. However because of the higher
active level of dicumyl peroxide available from Di Cup R
the dicum~l peroxide contetlt of each compositi.on is about
equal. The use of Vi Cup R was tested to determine
whether the dicumyl peroxide present would be more
effecti.ve in generating a higher degree of cross-linking
- because of the ease of processing to a homogeneous mix
using ~he Di Cup R, However,no difference in effective-
ness was found.
Turning now to example ID 80~87C the ingredients ~,
of this test example were essentially the same as those
of ID 80-87B with ~he exception that there was an increase
in the amount of Di Cup R employed but also there was a
substan~ial increase in the amount and composition of the
antioxidant which was employed. The results in TabLe I
show a very substanti.al increase in both tensile strength
and modulus for the ID 80~87C test example. In act, the
de~ree of increase was quite surprising and unexpected,
particularly inasmuch as the addition of the particular
antioxidant material had the surprising apparent effect
of increasing the degree of cross~linking of the ethylene
propylene material of th~ base composition. In other
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- 17 - ~ C 2043
words, improvements in the tensile properties are
normally associated with increases in the cross-linking
and increases in the cross-l:inking are normally associated
with increases in the amount of cross-linking agent
employed. In this polymer systern the cross-linking
agent is the peroxide and no~ the antioxidant. What is
surprising is the finding that an increase in antioxidant
coupled with a modification :in antioxidant content
apparently gave rise to a substantial. increase in cross-
linking as evidenced by the .increase in the tensi'lestrength and tensile strength related properties.
In fact, in run ID 80 87C the peroxide had
been increased and further sampl.es were prepared to test
whether the increased ter.si'le stren~,th fo~md showld be
attributed to the peroxide or to the modification of
antioxidant or possibly to both.
A second set of trial rulls were made by pre-
paring both control and novel compositions and by testing
them using the procedures and the format which has been
described with reference to the compositions and their
preparation and testing as set out with reference to
Table I.
The results achieved in such tests are listed
in Table II benea~h the compositions which were tested.
; 25 Here again the amounts of the ingredients of
tlle composition are given in parts per 100 parts of
base polymer.
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,-~ It is no~eworthy irst that the eontrol sampleof Table I, namely 1852-19-07 was repeated in rnaking the
,' runs for e~aluation of compositions as carried out with
~ reference to the tests and test results listed under
,~ 5 Table II.
., In this regard please note that although the
components of the composition were essentially identical
for the control sample of Table I and the control sample
of Table II nevertheless there are somewhat different
test results obtained from the measurements of phy~ical
properties. Thus, the tensi:le strength of the control
sample of Table II W2S 866 psi while that o Table I
was 787 psi. Similarly the elongation of Table II was
730~/O whereas that of Table I was 573%. Further, the
modulus of Table II was 532 psi while that of Table I
is 502 psi. It should be understood that in running
tests of this sort different values will be obtained in
the test results due to slight variations in some of the
val-iables of processing or of the mixing or ofthe testing.
The tested property value numbers of the control sample
of Table II are deemed to be entirely compatible and
consistent with the values found for the con~rol of
Table I. However, what is quite remarkable and striking
are the very large di.fferences which are found in the
comparison of the tes~ values of the physical properties
of the control sample of Table II and the test values
for the physical properties measured for the other test
samples of Table II.
Turning now more specifically to the illustra-
tive examples of Table II, the compositions are as set
forth in the Table and are described here principally with
reference to the differences rather than to recitation of
all of the components which were employed in the sample.
Please note that in the test ID 80-87C of Table II, two
parts of Vulkanox ZMB-2 antioxidant were employed together
with one part of B.L.E. -25 an~ioxidant. The same ratios
of Vulkanox ZMB-2 and the B.L.E. -2S are employed in the
.
. ~ ~ ; . ~ '' ~
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- 21 - 41WC-2043
;
; exarnple I~ 80-90A and the only difference in composikion
~s ln the slightly different peroxide content. With
. reference spee:Lfically to the peroxide the purpose of
, using 4.71 parts of Di Cup R in example ID 80~87C is to
, 5 increase the amount of peroxide employed in a manner and
in an amount identical to the increase of peroxide
employed in the example ID 80-87C of Table I. In fact,
the compositions of the two ID 80-87C examples are
identical for the test of Table I and the test of Table
II. However, to demonstrate tha~ the improved results
in physical proper~ies of the ID 80~87C sample was not
the result of increase in peroxide over other samples of
Table I the peroxide content of samples of Table II was
reduced to a level which approximates that of the control,
namely 1852 -19-07 of bo~h Table I and Table II. As is
evident from the reading of the tensile strength elonga-
tion and modulus given in Table II, the improvement in
properties of the novel composition of this invention is
not the result of a modiEication o ~he concentration of
peroxide alone. This last reference is of course to the
example ID 80-90~ as shown in Table II inasmuch as the
peroxide content of example ID 80-9OA of Table II
corresponds closely to that of the control of Table I
and Table II, namely 1852 -19-07.
Considering next the examples ID 80-9OB and
ID 80-SOC, it is evident that these two examples employ
a smaller amount of Yulkanox ZMB-2 than the two previous
examples, namely ID 80-87C and ID 80-9OA. However, as
is evident from the results of the measurements of the
tensile strength, elongation and modulus the values
obtained for measurement of these physical properties
~re very s~bstantially improved over those of the control
1852 -19-07. Further, there is a demonstration of the
relatively low or insignificant effect of the change of
3~ peroxide concentration as between the ID BO-9OB and
~D 80-9OC examples. This confirms again the results
recited above with reference to the ID 80-87C and
3~s~
- ~2 ~ lWC--20l~3
ID 80-9OA examples concerning peroxide conce~tration.
Accordingly it is clear that the improvement in physical
properties is the resul~ of the inclusion of the i.midazole
antioxidan~ in the composition together with the amine
S antioxidant and not a change in peroxide or peroxi~le
concentration.
Considering next the ID ~0-9OD example, this
is precisely the composition which was employed in
examples described below used in the production o an
insulation which was applied to a wire. In this example
it will be noted that the concentration of the Vulkanox
Z~-2 was reduced still further below that in ~he ID 80-
90B and 90C and specifically down to a concentration of
l/2 part of the Vull;anox Z~-2 Nevertheless, very
suhstantial improvernent in tensi.le strength is observed
with reference to the control sample 1852 -1~-07. Also,
substantial decrease in the elongation is found where
the ID 80-9OD sample is compared wit-h the same control of
Table II. Further, a substantial increase in the 200~/~
modulus was achieved al~hough the concentration of the
Vulkanox ZMB-2 was at the relatively low level used and
listed in the example ID 80-90D. In fact, the choice of
the composition of the sample ID 80-9OD was made based on
the overall combination of properties of the composition
and was not made based on onlythe tensile strength, or
on'y the elongation, or only on any other single one of
the properties. The value of the tear resistant property
was influential in the choi.ce which was made inasmuch as
it is desirable to have favorable tear resistant proper-
ties and higher tear resistant properties are generally
favorable. In this regard it is noted that the reduction
in tear resistant properties is smallest for ~he ID 80-9OD
example of Table II when comparison is made with the tear
resistant properties of the control 1~52 -19~07.
Considering next the examples and the technical
data which is assembled as Table II, here again there
was a repetition for the purpose of experimental
~ : . . . . . . .. . .. . . . .. .. ....
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- ~3 - ~lWC-2043
verification and control. of two of the examples which
are given above in Table I. The first is the control
1852 -19-07. The second is the ID 80-87C. The identity
of these two runs with respect to ~he runs listed in
Table I, Table II and Table III are self~Pvident from
a comparison of the content of the three Tables.
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~rl rl ~ 1 ~ rl
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Turning next to the example ID 80-96A, in this
example the test of ID 80-87C is repeated in essence
with the small variation in the Di Cup R component as
has been discussed above. Otherwise the compositions
are essentially iden~ical.
Lastly and significantly, the example ID 80-96B
has a composition which matches that of ID 80-96A with
the exception that the Vulkanox ZMm-2 of example ID 80-
96A is absent from ID 80-96B but the Vanox ZMTI anti-
oxidant component is present in example ID 8~-96B in an
amount which is equivalent to the amount of Vulkanox ZMB-2
present in ID 80-96A.
Again by comparison of the results obtained
there is a significant reaffirma~ion of the improvement
in the test values for tensile strength, elongation and
modulus properties based on the repetition o~ these
respective tests and comparison o~ the values with those
for the control sample 1852 -19-07 of Table III. Further
in Table III there is reported the repetition and con~
firmation of the results for example ID 80-87C as listed
in Tables I and II.
These two examples 1852 -19-07 and ID 80-87C,
are repeated as part of the sets of tests conducted and
reported in each of the three tables and the three
independent confirmatory tests appear in each of the
three tables. Because of the similarity of values '- ;
obtained in each of the three 1852 -19-07 examples and
the similarity of values obtained in the ID ~0-87C
examples coupled with the. substantial differences between
values for the 1852 control and the repeated 80-87C test
example the validity of the improvements obtained by the
coml~ination and addition of Vulkanox Z~2 antioxidant
mat.erial is verified and by the combination of the Vanox
ZMTI, each of which materials is a zin~ salt of 2-mercapto-
~olylimidazole.
~le significance of 96B test is that it confirms
: that the improved resul~s obtained in the data of Tables I
, -
.
3~ 2
~ 27 - 41WC~-2043
and II is not limitecl to the employment of the Vulkanox
~MB-2 alone in the composition which is prepared, bu~ is
tied to and dependent on the use o~ a zinc salt of
2-mercaptotolylimidazole.
Considering next the pertinency and relevancy
of the discovery of the uniquely beneficial effect of
the addition of even small amounts of the combination of
antioxidant compounds, zinc salt of 2 mercap~otolyli-
midazole such as Vul.kanox ZMB-2, and the amine antioxidant
such as B.L.E. - 25 to the compositions as recited in the
tables, the compositions and parti.cularly that of example
ID 80-9OA, were em210yed in preparing insulated wire
samples. In general, the data obtained from the platen
cured materials as recited in the tables do not
correspond, value for value, to the values o~ data
obtained from compositions formèd and deposited on wire.
However, it has been fo~ld that the beneficial effects
which are evident from the study and comparison of the
platen sample data of Tables I, II and III are available
and are present in the cable samples which are prepared
with thesc compositions and particularly with the
selected composition of test example I~ 80-9OD.
As has been indicated previously, the composi-
tions of the present invention are improvements over those
previously known. The results achieved in preparing the
novel compositions and in curing and testing them are
drawn from the labora~ory preparation, cure and test of
platen samples performed with the objective in developing
; the new compo~md not only to provide the novel cured
compound itself and the novel precured composition, but
also to formulate the material for application to wire ~
as the insulation therefor. ~;
Prior art compositions similar to that of the '
control composition of Tables I, II and III have been
known and have been used in the past for a number of
years. Such prior art composition was known and is -
shown in the tables with thc identification 1852 -19-07.
.:
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2B - 41WC-2043
A sample of such prior art composition was applied to a
cable and the composition was cured on the cable by
subjecting ~he composition and cable to a steam atmosphere
at an elevated temperature. Generally the steam pressure
for cure of such prior art compositions on cable is
between about 225 to 250 psig. Saturated steam, such as
may be used in curing such a composition on a wire or
cable would have a temperature of 395F. with a pressure
of 220 psi~. Alternatively, saturated steam at a
temperature of ~06F.and having a pressure of 250 psig
may be used. Using a prior art composition illustrated
by the 1852 -19-07 composition of Tables I, II and III
and using a steam curing procedure in the temperature
and pressure range recited above, a cured insulation was
prepared on a ca~le.
The particular cable is American Wire Gauge
size No. 2/0 AWG. The conductor was stranded tinned
copper and there were 325 strands each having a diameter
of .0~01 inches. An insulation wall thickness of approx.
0.155 inches was deposit.ed and steam cured on the con-
ductor. This construction was the construction for both
a prior art composition according to sample 1852 -19-07
and was also the construction for a sample identified as
T1~52 -19-07C. This latter composition is the same as
the composition identified in Table III as ID 80-9OD.
Subsequent to its preparation of the prior art
cable the insulation was stripped from the cable so that
test samples could be prepared to study the physical
properties of the insulation. The test samples were
prepared in the conventional manner known in the polymer
testing art and the following results were obtained using
the prior art composition. The tensile streng~h based on '~
measuring five samples was 675 psi. Elongation again ;
based on the use of five samples was 819~/o. A tensile
stress a~ 200~/o elongation, also known as 200~/o
modulus, based on a test of five samples was 425 psi.
. .
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29 - ~lW~-~043
Tear resistance of this cured prior art composition was
tested on six samples and fln average tear resistance
of 37.83 pounds per inch was :Eound. The test used is
the ASTM D470 tear resistance test.
For an insulated cable prepared from the
ID 80-9OD composition, extruded onto conductor and steam
cured as described above, folLowed by stripping and
testing of the cured insulation the following physical
properties were found: the tensile strength wa~ 828 psi,
elongation was 881%, the 200% modulus was 502 psi, each
value being based on measurement of three samples.
Tear resistance measurements ~ere made on six
samples and an average tear resistance of 35.9 lbs/in.
was found. The cable was tested for dielectric breakdown
and a value of over 58kv was found.
The properties of the insulation of a second
prior art cable were compared with those of a cable
insulal:ion formed with the preferred composition of
sample ID 80-9OD of Table IL above. The cable construc-
tion for each cable was onP for a 2 AWG made up ofnineteen 7 strand bundles, each strand of which had a
diameter of 0.0223 inches. An insulation wall thickness
of approx. 0.155 inches was formed and steam cured. The
outside diameter was 0.670 inches or the prior art cable
and 0.683 inches for the novel cable of this invention.
The tensile strength of the prior art insulation
was found to be 662 psi and the per cent elongation was
876 based on five tPSt samples. The 200% modulus was 400,psi
again based on five test samples. A tear resistance of
35.88 psi was found based on a measurement of six samples.
A comparable cable was prepared insulated with
the ID 80-9OD composition. The cable was a 2 AWG having
nineteen 7 strand bundles each strand of which had a
diameter of 0.0223 inches. The insulation thiclcness was
approx. 0.155 inches and the insulation was steam cured
following eY~trusion of the insulating wall onto the cable.
_ 30 - ~lWC-~043
On stripping of the cured insulation and
measuremen~ of i~s properties in the conventlonal manner
it was fo~md that the tensile strength was 818 psi and
the per cent elongation was 905 based on a test of three
samples. Also the 200% modulus was 475 psi based on a
test of three samples. A tear resistance o~ 33.8 lbs.
per inch was found based on a test of six samples.
The cables prepared pursuant to this invention
were found to have acceptably apt electrical properties
at least as good as t:hose of prior art cables but having
a combination of significantly superior physical
properties as set forth above.
For most prior art and other cable constructions
it is frequently desirable and often mandatory to include
a film or strip of separator between the stranded con-
ductor and the deposited o~lter layer ofinsulation. A
strip of Mylar having a t~ickness of about 2 mils was
employed as a separa~or on the cable products described
herein. The electrical properties of the cable reported
above are based on a cable made with the Mylar ribbon
sellarator.
Referring to the drawing, there is shown a
typical construction for an insulated electrical wire or
cable product 10, comprising a metallic conductive
25 element 12 and an overlying body of cured elastomeric ~.
insulation 14 extending ~hereabout or covering the
conductor. In the drawing, the product 10 is illustrated
as a short section with the insulation 14 removed from
the end portion of the conductor 12. According to one
embodiment of this invention, the novel ethylene-
propylene rubber composition thereo~ can be used to
provide or form the insulation 14 on a conductor 12 of
wire or cable product 10. It is to be understood from
the ~oregoing, however, that the lnsulation can comprise
35 a coatillg on any portion of a conductive element and that .:
the insulation need not com?letely enclose the element
where such is not necessary for a desired insulative effect.
.
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- 31 - 41WC-~043
Althowgh the invention has been described with
reference ~o certain specific embodiments thereof,
numerous modifications are possible and it is desired
to cover all modifications alling within the spirit
and scope of this invention.
.
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