Note: Descriptions are shown in the official language in which they were submitted.
~$'~
IMPROVED G.~EEN ST
BACKGROUND OF mE DISCLOSURE
The present invention relates to improved green
strength properties o~ elastomer ble~ds. More specifically
the present invention relates to the incorpoxation of an
ionogerlic functionality or group into the backbone of a
s~nthetic elastomer to improve the green s-~rength of
elastomer blends containing ~he synthetic elastomer with
- either natural or synthetic cis~l,~ polyisoprene. ~.
Scie~ce and technology in the elastomer ~ield has
improved to such an extent that synthetic elastomers have : -:
supplemented or replaced natural rubber to a great extent
in the fabrication of tires and okher rubber products.
Stereo-specific polymers and particularly synthetic cis- .
1~4 polyisoprene have demonstrated physical p.roperties
:~ ; similar to and thus are capable of becoming a complete
replacemsnt for natural rubber. However~ a major deficiency . .:
~ o~ synthe~ic elastomers incl.uding synthetic cis~
! polyisoprene is its lack o~ suf~icient green strength
required ~or satisfactory processing or building proper-
ties required as in building tires. The abatement o~ this
deficie~cy has~long been sought b~ the a~t ~Id would. :
: ~ ~ greatI~ ~acilitate in the replacement.o.~ ~atural:rubber
which is solely produced in tropical climates.
: 25 l'he term"greerl strerlgth" while being commonly
employed and generally:~understood by persons skilled in
,
the rubber~lndustry,~ is nevertheless:a~di~ficult property :;
~ : to precisely de~ine,~ Basically~ it~ls that property of a ~
.; ~' ,.
- - . - , . - ,
polymer~ common in natural rubber, which~ under normal
building conditions where multiple components are employed7
results in little or no unwanted relative movement of the
assembled components. Thus, the problem of low gree~
strength, that is the lack of the re~uisite mechanical
strength for processing and fabricating operat~ons neces- .
saril~ carried out prior to vulcanization with a s~lthetic
polymers or copolymers~ is lacking~ That is~ generally
the maximum or "peak" stress which the unvulcanized mate-
: 10 rials will exhibit ~uring deformation is rather low~ ~hus,
unvulcanizea strips or other ~orms o~ the elastomer are
o~en distorted during processing or building operations.
Although numerous additi~es and compounds have been
utilized in association with various elastomers and parti-
cularly synthetic cis 1,~polyisoprene, substantial.imprGve-
ment in green strength has generally not been accomplished.
Green strength has generally been~measured by
stress/strain curves o~ unvulcanlzed ~ompounds. Usually
.~ the per~ormance o~ a green compound is based upon three
points of the stress/strain curve~ namely the ~irst peak
or lnflection o~ the stress, the ultimate o~ breaking
tensile and the percent o~ ultimate elongation~ Iraprove-
ments in an~ one or more o~ these stress proper~ies lndi-
: cate improved ~reen:strength.
Among:the various additive compou.nds or agents
which have been utilized to improve green strength or
synthetic rubber elastom~ers are numerous nitroso compounds
:
as set forth in ~nited States Patent ~umbers 2~57a331;
2,l~77~015~2,5187576; 2,526~504~ 2~o~5g6; 2~690~7~0; and
--2
'
:: :
'
3,093,611~. Additionally, various dioxime compounds ha~e
been utilized such as those se-t forth in U~ S. Patent
Numbers 2,969,341; 37037,954; 3,160,595; and British
Patent 896,309. Yet another class of additives or com~
pounds are the diesters of 5-norbornene as set forth in
U. S. Patent Numbers 3~817~883 and 3,843,613.
U S~ Patent 3~893~983 to Br~ncaccio relates to
improving green strength of polyisoprene by reacting maleic
acid therewith. A similar patent is that o~ Yamauchi~
et al. U. S. Patent 31897j~03 relates to a reaction
between synthetic cis~ polyisoprene and maleic anhydride.
Thesa patents are clèarly dif~erent from the present inven-
tion in that applicant's compound is not incorporat~d in
synthetic or natural cis-l~L~~polyisoprene but rather in a
synthetic elastomer which is then blended with na~ural
rubber or synthetic cis~ polyisoprene.
Ano~her prior art patent which relates to
improved green strength is French Patent~Number 2~215,429
wnich utili~es very small amoun~ of various carbo~ylic
acids with various polymers such as polybutadiene and SBR.
~owever, at higher amounts O.r the carboxylic acids~ the
rubbers are rendered unprocessable~ This patent does not
relate to hlends containing any cis~ -polyisoprene
(natural or synthetic)a which is often needed ~or lts
cured properties such as low heat buildup. Furtherm~re~
at carboxylic acid concentrations which lead to process-
able rubbers~ the improvement of properties is small.
In an artlcle by Brown and Gibbs, it i5 disclosed
.
~ that unsaturated carboxylic acids were copolymerized l~ith
.~.h~
olefins and dienes whereln at least 100 milllequivalents
o~ the acid were utilizea9 Rubber Chemistr~ and Technolo~,
Volume 28~ Pa~e 937 ~1955). However, esse~tially copoly-
mer thermoplastic rubbers were produced which readily
reacted with zinc oxide or other polyvalent metal compounds
to ~orm cross-links which could not be readily worked on
mills or in internal mi~ers using classical mixing pro-
cesses for the preparation o~ rubber compounds. Addition_
ally~ this reference related only to the use of dienes or
olefins and contains no suggestion whatsoever of natuxal
or synthetic cis 1,4-polyisoprene or o~ elastomer blends.
It ls moreover stated that the"physical properties o~ an
unvulcanized carboxylic elastomer having a carboxyl content
of 0.1 e~uivalent or less were essentially those o~ an
analogous non~carboxylic polymer." However, the present
invention finds this statement to be un~rue.
In various articles published in the magazine~
LSDL~t ~ very small amounts o~ carbo~ylic
acids were utilized in a manner similar to that set ~orth
:20 in the French patent above~ Speci~ically in articles by
Ko~alev et al, Voluma ~ 7~ M____dzhera~
~LIIe Ll;~ L~ 1 (197~L2~and Smirnova Vol
(1971) isoprene rubbers as well as butadiene-styrene
thermoplastic rubbers were produced containing carhoxyl
and ester group~s. In general.~ these rubbers show improved
strength. However~ the introduction of the carboxyl or
ester groups were usually carried out at a pressure o~
: about~2~0 atmospheres of ~arbon mono~ide5 a highly toxic
':
4 ~ -
: ' : -
. ~ : . . .. , : ,
gas. Additionall~, the carboxyl or ester groups are
int.roduced into an already preformed polymer such as
polyisoprene or butadiene-styrene polymer. AlSOg none
of these references relate to blends of synthetic elasto-
mers with natural or synthetic cis-l,L~-polyisoprene or of
elastomer blends.
In an. article appearing in the ~51~iL_~
Pol~e.r Science~ Volume~ umber 6~ Pages~5~9.-60~ ~_2
elastomers are ~ormed utilizing carboxylic acids and
esters thereo~ These compounds, when cured~ have
exceedingly high modulus at 300 percent e~te.ntion and are
totally u~suitable to mill. Furthermore~ no green strength
improvement was reported, and no data was reported for
uncured properties. This reference also is solely related
to copolymers o~ butadien.e and not to blends including
natural or synthetic natural rubbers. ~he thrust of
the entire re~erence was towards improved oil resiskance
and low temperature properkies~
SUMMARY OF T~E INVENrION
It is there~ore an object o~ the present inve~
tion:~to improve the green strength of elastomer blends.
It is another objec~ o~ the present invention to
. .
improve the green strength o:~ elastomer blends, as above
wherein the blends comprise .natural or synthetic cis-l~
polyisoprene and synthetic elastomers.
It is a further ob~ect o~ the present invention
to improve the green strength o~ elastomer blends, as . :
. above~ wherein an~ionogenic group is included in the
: backbone o~the s~nthetic elastomer.
- .:
~ ~.
' - , ':
.. . . .
lt is an additional object of tl~e present invention to improve the
green strength of elastomer blends, as above, wherein an unsaturated compound
containing the ionogenlc group may be convenlently added during the polymer-
ization of monomers forming the synthetic elastomer without any major temp-
erature or other process changes.
It ls stllL another object of the present lnventlon to improve the
green strength of elastomer blends, as above, wherein the synthetic e:Lastomer
is any elastomer prepared by a free radical process.
It is still another object of the present invention to improve the
green strength of elastomer blends,as above, wherein the blend may be mixed
or compounded with conventional compounding agents.
It is still a further object of the present invention to irnprove the
green strength of elastomer blends~ as above, wherein large improvements of
green strength properties are obtained whlch permits substituting synthetic
cis-1,4-polyisoprene~for natural rubbers.
It is still an additional object of the instant invention to improve
the green strength of elastomer blends, as above, wherein the blends may be
utilized in radial tire carcasses.
In general, the present invention provides a prevulcanization process
for improving the green strength of blends of syntlletic elastomers and nat-
ural or synthetic cis-1,4-polyisoprene, being characterized by the steps of:
adding an amount of an ionogenic ~msaturated compound to synthetic elastomer-
forming monomers before poly-
. .
.
~ ~ '
: ~ ,
-6-
, ~
merizing such that the amount of said ionogenic compollnd
incorporated in said synthetic elastomer after polymerization~
ranges from about ~ to ab~ut 58 milliequivalents per 100
parts by weight of said synth:etic elastomer, said ionogenic
unsaturated compound having the formula:
r ~ X~ (CH2~ C - A
X2 R1
where Xl and X2 are selected from the group consisting of
hydrogen, methyl, carboxyl, fluorine, chlorine~ bromine~ and
iodi.ne; where R1 is H, C1 through Clo alkyls,- (CHX)n- COOH
where n = 0 to 4, or a halogen is selected from the group con-
sisting of fluorine, chlorine, bromine, and iodine; where
m = 0 to 4, and where .A is OH, NH2 or OM where M is a metal
~. selected from Gro~p lA, 2A, or 3A or 2B of the Periodic
`:~ Table; said synthetic elastomer made from monomers selected :
from the group consisting of at least one diene having from 4 .:
: to about~l0 carbon atoms, a conjugated diene having from 4 to
about:l0 car~on atoms w:ith. an olefin having from 2 to about :.
14 carbon atoms so that a multi-component polymer is formed, ~:
; and combinat~ions thereof; polymerizing said ionogenic un~
saturated compound and said synthetic el.astomer forming mono- : -
mers;~ forrning polymerized synthetic ela.stomers from said
lonogenic compound and said synthetic elastomer forrning mono- ~:
mers~containing;from~about 9;to ab.o~t 58 mil1iequivalents of
- C - A groups~pendant from the backbone of said synth:etic
polymer; Lix~ing~s~aii pclymerlzed synt~hetic elastomers with a
:
.
compound ~elected from the group consisting of natural and
synthetic cis-1~4~polyisoprene to form said elastomer blends,
the amount of said natural or synthetic cis-1~4--polyisoprene
ranging from abou.t 1 to about g9 percent by weight based
upon the total weight of said blend; adding from about 3
percent to about 5 percent by weight based on said blend of a
metal compounding agent; and forming ionogenic bonds between
: said polymeri~ed synthetic elastomers through said pendant
O
- C A groups so that said blend has improved green strength.
-:,
.: DESCRIPTIOM OF ~HE PREFFRKED EMBODIMEN~S
According to the concepts of the precent inven-
tion, improved green strength properties are obtained in .
elastomer blends of synthetic elastomers and natural or syn- ~.
thetic cis-1,4-polyisoprene. The increase in green strength . .
is generally thought to arise from the incorporation of ionic
bonds into the~backbone of the synthetic elasto~er. A:ccord- .~
ing~to the present ihventlOn~ an ionic bond is not introduced ~ .
~ into the:natural or synthetic cis-1,4-polyisoprene but only
into the synthetic elastomer. Generally, the compound which
contains th.e ionic bond is an unsaturated ac:Ld as described .
hereinbelow.
: The:s;ynthetIc elastomers are polymers, copolymers, ~ ::
~ 25~ ~ terpQlymers,:etc~:mad~e from monomersS generally considered
: by t,hose ski.lled in the art, capable of forming ru~bers.
More specifi.cally, the monomers are selected from~the group
ns'~t'~ ,t o e onJ~g~ ~d ~ e h_.'r~ om 4 o
i: ~
~ &~
about 10 carbon atoms, conjugated dlenes having from 4 -to
about 10 carbon atoms and olefins having from 2 -to about
14 carbon atoms, that is interpolymers of these two groups,
and combinations thereof. A preferred group of olefin com-
pounds are the vinyl substituted aromatic hydrocarbons con-
taining from 8 to about 12 carbon atoms and include styrene,
~-methyl-styrene, ortho-
~'
.
;~:: ~ ~ :' '
: : : .
, :~ i : :; :
g~?~
para-, and meta-meth~l and ethylstyrene and the like 0~
the non-aromatic ole~in compounds, the compounds containing
from 3 to 6 car~on atoms are preferred. Specific examples
of olefi.ns include ethene~ propene~ butene~ penteneS
he~ene, heptene, octeneg nonene~ decene, dodecene, and
the like~ Concerning the diene compounds, the dienes having
from ~ to 6 carbon atoms ~re pre~erred.
Speci~ic synthetic elastomers which ma~ be
improved in the present invention include polybutadiene~
both cis ana trans, polyisoprene~ both cis and trans,
polypiperylene~ polydîmethylbutadiene~ polychloroprene~
polyacrylo.nitrile~ copolymers or interpolymers o~ the
dienes, for example, poly(isoprene-co-butadiene), poly
tbutadiene-co-piperylene), and the like, terpolymers such
as pol~butadiene-co-piperylene-co-isoprene)~ and the like.
Additionally7 copol~mers of a diene and an ole~in may
be utilized such as poly(styrene-co butadie~e) 3 poly
talpha-methylstyrene-co~butadiene3, pol~(butadiene-co-
propene)~: poly(butadiene-co-butene), and the like~ ~re-
~0 ~erred elastomers o~ the presen.t invention include pol~-
isoprene7 either cis or trans~ polybutadiene7 elther c-Ls
or trans, and the copolymer of styrene and butadiene.
The synthetic elastomers are prepared according
to well .known methods and processes as well known to those
s~illed i.~ the artD Generally~ a ~ree radical process is
utilized in the present in~ention since the unsaturated
compound would tie up or kill the elastomer catalysts ~or
cationic or anionic processes. Conventional and/or
.~ common ~ree radical catalysts may be used in common or
-9~
'~
'
typical amounts as well known to those skilled in the art.
The process may be carried in solution, bulk, suspension
or preferably in an emulsion.
When copolymers, terpolymers, etc are prepared
utilizing an olefin, the amount of the olefin range may
range from 0.1 to about 99 percent by weight. In other
~ords, so long as a few diene monomers are contained in
the monomeric mi~ture~ the copolymers~ terpolymers~ etcO
can be later vulcanized. Generally~ the weight percent o~
the olefin compound will usually range from 0.1 to about
55 percent with a more desirab~e xange being ~rom about 10
percent to about ~0 percent. A pre~erred range o~ the
ole~in compounds such as styrene or alpha-methylst~rene
ranges from about 15 percent to about 25 percent.
The above-described synthetic elastomer monomers,
when polymerized in the presence of the ionogenic unsatu-
rated compound~ have an ionogenic group included in their
backboneO I~ the present invention~ the term "ionogenic"
is used to mea~ a molecule or a group which may rèadlly
ionize or readily react with ions. Although the synthetic
elastomer containing an ionogenic group can be brought
about by reacting diene polymers or diene copolymers with
a suitable ionogenic compound, a pre~erred method is
simply to add a polymeriæab1e unsaturated ionogenic monomer
to the diene monomers or monomgric mixture containing both
diene monomers and ole~i* monomers~ According to this
method~ no~ additional step is necesgary.
The polymerized synthetlc elastomer containing
the ionogenic group is then blended as in a conve~tio~al
.
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:
.
compounding process with either natural or syntlletic cis-
l~L~ polyisoprene. ~he amount of either the natural or
synthetic cis~ polyisoprene may range from about 1 to
about 99 parts by weight with a preferred range generally
being from about 50 to about 90 based upon the total weight
o~ the blend. It is these blends of the synthetic elas-
tomer with the natural or synthetic cis-l,~polyisoprene
which exhibit improved green strength.
Re~erring to the hereto~ore described ionogenic
unsaturated compound which is polymerized with the syn-
thetic elastomer monomers7 it generally is an u~saturated
carboxylic acid o~ the acrylic type. The unsaturated
compound has the formula:
, , ~ .
Xl (CH2)m ~ C ~ A
C--C
X2
where Xl and X2 are hydrogen7 methyl~ carhoxyl~
or a halogen selected ~rom the group consistlng of
fluorine~ ch1orine, bromine and iodine~ Rl is H, Cl through
C10~ -(CH2)n-COOH~ n = O to ~ or a halogen such as
~luorine~ chlorine~ bromine and iodine~
m = O to 1~ and A is OH~ NH or OM where M is a
metal~selected ~rom Group lA:~ 2~ 3A and 2B o~ the
Periodic Table such as lithium, sodium, po~assîurn~ calcium~
zinc~ boron~ aluminum and the li~e.
Pre~erably, A is hydroxyl. Desirably Xl and X2
are hydrogen and Rl is a hydrogen atom or a methyl group~
, . ~ , . .......... . ........... .
..
-.-
Pref`erably~ the compound o~ the formula is acrylic acid or
methacrylic aciA. Other typical compounds of the formula
which may be used include itaconic acid, fumaric aci
ethacrylic acid, ethylpropenoic acid, prop~lpropenoic acid~
butylpropenoic acid, various substituted propenoic acids
such as l-me~hylpropenoic acid and the like. Additionally;
~arious acrylamides may be used, that is where Xl and X2 is
hydrogen and Rl has 1 to 10 carbon atoms and A is NE2. Addi-
~ionally, the variolis salts of the formula wherein the hyclro-
1~ gen of the hydroxyl group is replaced by a metal o~ the
Group lA elements of the Periodic Table may be used.
Generally~ the amount of io~ogenic functionality
or group basea upon milliequivalents o~ O group per lOQ
- C - A
parts by weight of synthetic elastomer is from 8 to about
95 milliequivalents. A more desirable range is from 9 to
about 60 milliequivalents with a pre~erred range being from
9 to 1~ milllequivalents. An~amount of~ionogenic unsatu-
rated compound is preferably added to the synthetic
elastomer producing monomers or mi~tures of monomers i~
a rubber copolymer is to be made. ~his amount is deter-
mined from the relati~e reactivities o~ the ~rious monomers.
Thus, the backbone of the s~nthetic elastomer will contain ..
a pendant O group through which~ it is thought~
- C - A
ionic bonds will be forme~d with other polymers or
; 25 copolymers and thus result in improved green strength .
For example, through hydrogen bonding ar o-therwise, ~he ~ :
polymer~molecules are~held together through an i.onic bond
:: :
: -12--
.
, ' '- ,
- - . , :
and therefore give improved green strength properties even
when they are blended as through conventional compounding
with another elastomer such as natural or synthetic cis-1,4-
polyisoprene. Generally, the synthetic elastomer containing
the ionogenic group in the backbone has some irnproved green
strength. However, when tire carcasses and treads are made,
heat buildup may be high and thus it is often desirable to
blend the synthetic elastomers containing the ionogenic group
with either natural or synthetic cis-lg4-polyisoprene to re-
duce some heat buildup. Surprisingly, such a blend has im-
proved green strength.
The synthetic elastomers and the natural or syn-
thetic cis-1,4-polyisoprene can be mixed according to conven- -
tional methods and may contain conventional compounding agents
in typical amounts. For example, carbon blacks may be added,
from about 3 to about 5 parts per 100 parts of blend of zinc
oxide may be added, various ~illers such as clays, silicas,
and calcium carbonate, various plasticizers may be added,
various oils such as aromatic or naphthenic oils, various anti-
oxidants, various crosslinking agents, various accelerators,
and the like.
The blends of the present invention find particular
use for the carcass of tires and other tire components~ and
may also be utilized for common industrial uses such as con-
veyor belts, shoe soles, hoses and the like. ;
The invention ~111 be better understo~d by the
~ollowing recipes, examples and data.
A synthe~tic elastomer was prepared in accordance
with Example I. The quantity of the monomer, the methacry-
.
lic acid and the mercaptan were varied as set forth in Table I.
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., :.,:,
~ ~ .
EXAMPLE I
PREPAR~TION 0~ LAI'EX
__
(1) To 18.3 pounds of deionized water was added 1.36
pounds of a 10 percent solution of a sodium salt of
CALSOFT LAs-9g (a traclemark), a linear dodecyl~en-
zenesulfonic acid ~manufactured by the Pilot Chemical
Company and 6.8 grams of Na2SO4.
(2) To 227 ml of water was added 4 drops of sulfuric
acid (66 Baume)3 0.075 grams of FeSO4-7H20, 10 ml
of a 35 percent solution of ~ERSENE ~a trademark),
Fe-3 Ga mixture of tetrasodium salt of ethylene-
diaminetetraacetic acid and the monosodium salt of
N,N~di(a-hydroxylethyl)glycine) manu~actured by
Dow Chemical Company, 0.75 grams of sodium formalde-
hyde sulfoxylate and 0.50 gram of Na2S~01,-2H20.
(3) The mixture of paragraph 2 is added to the mixture
of paragraph 1.
(4) An amount of methacrylic acid, styrene and a ter-
tiary mercaptan such as SULFOLE 120 (a trademark),
(t-dodecylmercaptan as supplied by The Phillips
Petroleum Company) as set forth in Table 1 was
added to a vessel and mixed.
(5) The mixture of paragraph 4 was then added to the
mixture of paragraph 1.
(6) An amount of butadiene (caustic and water washed)
as set forth in Table I was then added to the mix-
ture of paragraph 1.
(7) Then 250 ml of styrene was mixed with 3.0 ml of
p-methane hydroperoxide.
(8) The mixture of paragraph 7 was then added to para-
; graph 1.
(9) A shortstop was prepared by mixing 200 ml o~ water,
20 ml of a 41 percent solution o~ sodium dimethyl-
dithiocarbamate and 2 ml of an 85 percent solution
of diethylhydroxylamine. This mixture was then
added to the mixture of paragraph 1 when 60 percent
conversion of monomer to polymer was attained.
Polymerization was conducted at 600F at 190 rpm
agitation. Polymerization was stopped by the addition of the
s~orts~op set forth in paragraph g and the latex was
-14-
~ .
. .
. . - . , , - . .
steam stripped. The latex was coagulated by pouring it
into two volumes of a 2 percent water solution of
Al2(so4)3-l8H2o
The monomer and modi~ier quanti.ties ~or a
control~ as well as two tested elastomers~ are as ~ollows
as set forth in Table 1.
.. :
:
~:
lP~
~q . ~ + ~ ~ a
~ ~ O O Q,
~-'
00
~0
~ ,n ,Q
r-l ~ ~ O O
C' C~
~ .,
E~
~' O
+
: Q
O
V ~ hD
~ :~ o
.,~ '
h
Oa ~ a a) ~ ~ ;
P ~ ~ ~ h
:
:: , '
:
'
' - '
: ~ . . ~ . ' .. - '
The control had a Mooney of 67 whereas Compound A
had a Mooney of 60 and Compound B had a Mooney of 56. Sheets
1~8 inch thick were molded at 300~ for 30 minutes and 1/10
inch dumbbells were Cllt. Instron (a trademark) tensile
tests were made at room temperature with an extension rate
o~ 508mm/minute (20 inch~minute), The following data was
obtained as set forth in Table l(continued).
~;
2a .::
~: ~
~ -17- .
. .
~ - ~
* co co
* . .
~a ~ o
P o
O ~
o +l +l +I P~ ~n
o ~ co ~
~
~; * *
¢
H ,~ ~ ~ ~ st
~Q ~1 ~ CO
H
O ~
,_ h P-
-- ~
~; ~ H ~}
¢ * *
* --~ o ~ ~ a
~D ~0 0
~1
,_ ~! o +1 ol ~ ~
~1 E~
~o ~ S
E I ~ u~ u~ ' I ' '
æ ~ ~; o o ~ c~l
~_ ~ +1
~ ~0 ~ ~ V ~ :.
H _~ H C' C~ ~7 td U~
~1 ~ ~ C~
: ~:1 O r-l
~1 ~1 ~ ~
¢ 0 ~ CO ,, 5;1 ~
~1 C~J O ^ ~;
+ 1 ~ ~1 ;
* O ,~
U:l
~ ~ r~ rl U~ ~ L
~1 +I I I ~I X
P~ co
,c~ O rd
,~ ~ a) ~d
¢ tq . u~
rd ~ c
- ~ * ~ ~ co a
* a) 5;, ,,,~0:
~ h 0~ ~rl
rl u~ H t~
r-l ~ O ~ ~) M t4
r-l r~ C) ~ r-l $k
0,~ ~ ,
*
* *
* * *
:
:
: ' ~
D~
As apparent~ the terpolymer con-~aining methacrylic
acid i.n the backbone has much improved ph~sical properties
and was about as strong as natural rubber.
EX~MP1E II
A control and Compound B (terpolymer~ described
in Example I were compounded with natural and synthetic
cis~ p~lyisoprene according to ~he ~ollowing formulation:
Natural* or ~ynthetic cis PI ~ 70 (wt)
SBR Control or Compound B 30
Stearic Acid l.5
Zinc Oxi.de 3.5
Mixture of Alkylated Diphenylamine 2.5
,SRF Black 15.5
FEF Black 25.0 i -
Naphthenic Rubber Process Oil 3.0
Coumarone Indene Resin 2~0
* ~ 1 Ribbed Smoked Sheet
The ingredients were mixed in a Brabender at 28~oF ~ .
; ~or 5 minutes. No cure occurred since no sul~ur was con-
tained in the xecipe. Sheets were molded and dumbbells cut
as previously described.
Upon testing on ~n Instron tensile testirlg machine
wherein l~200 percent was the ma~imum stxain obtainab1e by
the machine, the following data was obtained as set forth
in l1ab~e II~ -
.. .: ,
- .....
r~
O ~ O~
~ ~r, lr~ I I .
~h O ~rl (~ C~J OC) '
O O U~ ~ C~ ~ ~
Or~
r~rl C~ C~
Cll O U~ ~ ~ r-l C~
S~O P ~ l r~
1~
C)
ei _ ~p
H ~ ~ ~rl O O C~
~ ~ g ~
~ H ~
~ ~ ~3
~ I:q rl ~) ~D ~ r-l
a: ~ h~ a~ o
C~
rl O C~C`- ~D
~rl ~1) P
~ h ~ :
O
p~ ~ q g
`
o o o ~
l ~
hl h
h a) h a) o a) o a)
P~ ~'
o a) o a) I a~ I a
p~
I P~
_* O * O r-l O r l O
h ~ u~
r~ rl r~ rl ul rl
,Q ~ ~ C) C)
1~ ~rl ~rlC) C
. ~rl rl
~1 ~i
t~
o ~ ~ ~ ~ ~ ~ -
0 0 0 C~ :
:
:
~ : '
.
From Table II, it is apparent that signif'icant
improvements in green strength properties were obtained when
the synthetic elastomer containing methacrylic acid was uti-
lized in blends either with natural or synthetic cis-1,4-
polyisoprene without unduly increasing the compound Mooney.
The rubber blends set forth in Table II were curedutilizing 2.1 parts by weight of sulfur, 0.7 parts by
weight of AMAX (a trademark) ~M~oxydiethylene benzothiazole-
2-sulfenamide) obtainable from The Vanderbilt Rubber Company,
10 and 0.25 part,s of an oil treated symmetrical dipheny].- '
guanidine. ~ -
The rates of cure are shown in Table II A. Note
that the improved synthetic elastomer is lessscorchy than
i the control.
, 15
. .
~.
, - ,
~ 2~0
~: :
:; :
~ u~
a) a~
o~ ~ I~
c~ o
o c~l
a) ~ O O O
~ ~n
: ~ U~
H a) ~ ~) O
Fd o ~ ;
E~ C' O~ O
O
.: r-l OO 0
~_
Fq va~
`
: .', : ' - ,, ' . ' :' . ' ' ,' . ' - ' . . , ' . ' , :
b,;~
Sheets o~ the compoun~ containing natural rubber
and the improved synthetic elastomer were molded for 12
minutes while the other compounds wexe molded for 9 1/2
minutes. Dumbbells were cut as before and tested on an
Instron Tensile Tester 7 as before, and the following data
: was obtaiIled.
' TABLE III
Modulus
~ t~D~g~
Pts. Rubber Pts 100% ~0~ _ _600
~ . . . _, ~ . _ O
~ 10 70 Natural ci.s-1~4-poly- :
- isoprene 30 B 180 ~50 , 1~900
70 Natural cis-l,L~-poly- ~ .
- isoprene 30Control 210 700 2,300
: 70 Synthetic cis-l,~- '
polyisoprene30 B 2l~0 850 ~200
! 70 Synthetic cis~
polyisoprene30 Control 21~0 930 2~0Q
It is apparent that the i,mprovemen~s in green
strength previously mentioned were accomplished without
increasing the ~cured modulus.: ,.
While in accordance with the patent statutes~ the
pre~erred embodiments have been .illustrated and described
in detail, it is to be understood that the invention is not
limited there-to~ the scope o~ the invention being measured
solely ~by the scope Or the attached clai3nsO
.
-23-
.
~' .
- . . . . .