Note: Descriptions are shown in the official language in which they were submitted.
' 1062398
Th~ pre~ent i~rentlon relates to impro~ements in ne~
or recapped pneumatic tires having a tread composed of modified
elastomers oi th~ et4ylene-Q_olefin-termonomer typeO
~ la~tomer~ Or the etbylene-propylene-termonomer type~
al~o known under the designation "EP'~" or IIEPD~" are, a~ i~
kno~n~ copolymers Or et4ylene, propylene~ and a noncon~ugated
diene. The noncon~ugated diene ~hich may be c~clic or linear~
ie intended to introduce unsaturation~ ~hich make ela~tomer~
Or the etbylene-propylene type capable Or being ~ulcanized ~ith
~ulrur; it ~ay ior instan¢e be dicyclopentadiene, l~S-c~clo-
octadiene~ 1~4-he~adiene, ethylidene-norbornene, methylene-nor-
bornene~ te~rah~droindene, ~et~yltetrahydroindene~ etc.~ or so~e
other diene ~hich is copoly~erizable ~ith ethylene and propylene.
The ~PDMs are ela~tomers obtained ~rom ra~ materials
~uch as ethylene and prop~lene, ~hich are less e~pensi~e than
~utadienc and styrene, since the~ are less hlghly proce#sed pro-
du¢ts tb~n the latter.
- ~hese elastomers have certain aa antsges, particularly
their resistanco to aging and to o~idation~ related on the one
hand to their lo~ degroe Or unsaturation and on the other hand
to the position Or the double bQnds ~ith respeot to the chaln.
Thereiore their use ln the produotion Or r~bber articles~ and
~n particular tires~ may be ad~antageous; hlle their general
properties aro eatisfaotor~ as co~pared ~ith those Or the cus-
to~ary oon~ugated diene elastomers~ the EæD~8 on the other band
~ ha~o a eerious dra~back ~hich up to no~ has liDited thoir field
; o~ use~ namely they have a lo~ skid reslsta~ce~ m~ing lt dir-
ncult to use them to ~orm tlre treads.
-~ ~arlous solutlons ha e boo~ proposed ~n order to ro-~0 ~edy thie ma~or tra~back. It hae been atto~pted to cbange the
nature and the peroentage Or the ter~onom~r or olse tbe oompos~-
tlo~ of the monomors~ but contra~y to ~hat i9 true in the case
``
`~
. : .
.; ~,062398
oi the ordinary con~ugated diene elastomers in ~hich it is
po~sible to modi~y the dampening and the ~kid resistance by the
nature o~ the component~ o~ the polymer~ ~odiiicatio~ Or the
ethylene and prop~lene composition Or the copolymer do not
m~ke it possible to obtain products having a su~ilcient skid
resistance together ~ith satisractory properties oi utllization
and mechanical properties~
Thus with ela~tomers or.the EPDM type, these chanees
do not mske it pos~ible to obtain an elastomer ~hich has a sui-
iiciently bigh ~kid resistance to constituto a tread ~hich hassuiiicient adheren¢e to the road in all ~eather, ~hate~er the
estent to ~hich the tread i8 ~orn. ~ike~ise~ it has been at-
t~mpted to increa~e the amount Or carbon Uac~ or oil illler.
However~ ~hen the proportion oi carbon blac~ or oil in the mises
i8 inoreased~ ~hile the skid resistance 18, it is truo, impro~ed
thereby~ thero i8 at the s~me time obtained a ¢onsiderable re-
duction in the ~ysteresis properties and mechanical properties.
It has no~ been found that the abo~e-mentioned dra~-
~ao~s can be a~oided in a surprising and economically ad~anta-
goous rashion and that the lntended goal oi pro~iding elastomersof ~PD~ t~pe ~or tiro treads ~hich ha~e an excellent skid rosis-
tanoe and substantially normal hysteresis propertios as co~-
pared ~ith thoso oi a eon~entional EPD~ co~taining a nor~al ill-
~lng Or oarbon blae~ and oil i8 reaehed br uslng ~PD~-tJpo elas-
to ere modlfled in ac¢ordanee ~ith tho prosent in~ontlon.
Tho tiro or tho tread in aeeordanee ~ith the in~ention
i8 charaetorizod by tho iact that the tread is foraod Or an
olastomor of tho ot~yleno-o-oleiin-noneon~u4ated diene tetra-
~, poly~or t~pe oonta~ning a stericallr hi~dori~g ~ono-oloii~ mo-
noDer or a ~ixture oi sterieally hinderl~g mono-olefin monomere.
~y stexicall;y hi~doring mono-olo~in monomer there i8 undorstood
a mono~er ~hich, ~hon introduced in small quantit~ ma~os it
-2-
.
,
,
1062398
possible to increase the vitreo~i transition temp~ratllr~ of the
tetrapolymer.
In other words, the invention consists in using EPDMs,
the flexibility of the macromolecular chains of which has been
reduced by incorporating sterically hindering mono-olefin monomers.
These elastomers show an improvement in the shock-absorbing
properties and in particular an improvement in the skid resistance
which do not bring about any substantial reduction in the
hysteresis properties.
10The sterically hindering compounds which are ~mployed
in accordance with this invention have a high rate of l)olymerizati
and consist of norbornene and derivatives of norbornene of the
following general formula:
~. IR5
ch Rl~ R2~ R3~ R4~ Rs~ R6~ R7~ R8 represent hydrogen, a- 20 halogen,an aliphatic, cycloaliphatic or aromatic halo~enated or
unhalogenated hydrocarbon radical.
The sterically hindering compounds which are preferred
are 2-norbornene, 5-methyl-2-norbornene, 5-chloromethyl-2-
norbornene, 5-hexyl-2-norbornene, 5,6-dimethyl-2-norbornene,
5-phenyl-2-norbornene, (5,2,1,0 ,6) tricyclo-8-decene (6,2,1,13'6,
, o2~7) tetracyclo-9-dodecene. The elastomer obtained contains 3 %
`. to 30 % by weight of these monomers and preferably 5% to 15%.
The skid resistance is, as a matter of fact, a direct function of
the amount of these compounds in the polymer.
~;
,~
- 3 -
B
;.
106Z398
Ihe ~-ole~ins u~ed in con~unc~ion ~ith ethylene are
those ha~ing the iormula R-CH = C~ in ~hich R repre~ents a
hydrogen or an alkyl radicsl ha~ing one to eight carbon atoms.
~8 ~-olefins mention ma~ be made of l-propene, l-butene, l-pentene,
4~ethy1-1-pentene~ he~ene, etcO
As tetrapolymers used there mag be mentioned ror ins-
tance those:
oi ethylene-propylene-1,4-hexadiene-2-norbornene
Or ethylene-propylene-1,4-he~adiene-5-methyl-2-norbornene
oS ethylene-propylene-1,4-he~adiene-5-pheny1-2-norbo~neno
Or ethylene-prop~lene-1,4-hexadiene-5-chloro~ethyl-2-norbornene
oi eth~lene-prop~lene-eth~lidene norbornene-2-norbornene
o$ ethylene-propglene-ethylidene norbornene-5-methyl-2-norbornene
Or ethylene-prop~lene-et~ylidene norbornene-5-phenyl-2-norbornene
o* eth~lene-propylene-ethylidene norbornene-5-¢hloromethyl-2-
: norbornene~ etcO
These polymers are prepared by.methods ~hich are ~nown
por seO They can be obtained b~ reacting them on a c~ta1Jtic
~ystem formed oi
.a) a co~pound oi a transltlon ~etal belongin~ to
Groups IV to VIII oi the Mendelee~ periodic table Or elements~
and
b) compounds oi elements Or main Groups I to III Or
the ~endelee~ periodic table of elements. The preierred.compounds
tho elements oi Groups I to III aro aluminum compounds ot
tho for~Nla ~1 RXl~ in ~hich R repreeents a hydrocarbon radlcal
or a h~drogen ato~ and Xl and ~ ~hich osy be identical or
diirerent, ha~e the s~me mea~ing as R or may represent halogensO
~oro F ticularl~ mentlon ~ay be o~de oi the ~ 1 aluslnum
eosquichlorides, the dialkyl alumlnu~ halides~ the monoalkyl
al~ nu~ halides and the trial~yl or triaryl aluminu~s.
Suitable compounds of metsls oi Groups IV to ~III
.
.~ , .
106Z398
Or the periodic sy~tem are titanium tetrachloride, the esters
o~ chlorotitanic acids, the derivati~es of ~anadium such as
~anadium tetrachloride, vanadium oxytrichloride, the esters o~
~anadium such as ~anadyl butylate, vanadyl isopropylate, vanadium
triacetate, ~anadium acetylacetonate~ etc.
The copolymerization can be carried out in liquified
monomers, possibly under pressure, ln the presence of inert
diluent# such as aliphatic,.¢y¢loaliphati¢, or aromatic bydro-
¢arbons~ possibly _alogenated~ ~ith~n a ~ide temperature rango
estending from -20C. to ~60~C. The rea¢tion i8 stopped by the
co~ventional pro¢esses and the polymers are re¢overed arter e~a-
poration of the diluent by steam distillation.
~ he in~ention i8 illustrated but not limited by the
rolio~ing esample~. In these examples the structural ¢haracter-
- istics Or the poly~ers ha~e in ~eneral been determined in the
folloRing manner: The ¢ompositlon Or propylene is determined
in in~rared spectrography~ the composition Or hindering monomers
i8 deter~ined b~ nuclear ~ag.netic rosonance; the inherent ~18-
co dtios are determinod in ethylene tetrachlorlde ln a con¢en-
tration o~ Ool g~ in 100cco~ the skid reslsta~ce indes (SRT
index) at 20Co corre#ponds to the "~et skid indes" meagured
~ith the skid reslstance tester (SRT) marketed bg the Stanley
Co~pany~ the higher the indes~ the bettor the s~id resietanceO
.. ~he ~uloanization is eirected at a temperature close to 150-Co
~or about 20 minutesO
EDa~le 1
In thls eDa~ple~ copolymers Or the ethrlene-prop~lene
~ termo~omer (EPD~) type ~hlch are con~entional ~ith respeot to
thelr properties are co~pared ~ith an ordlnary con~ugated diene
elastomer ao a control. In the case Or the EPDM I/l and I/2
types continuous polymerlzation i# carried out in an 8 liter
r~actor ~hile the folloRlng rates Or flo~ in llters/hour ~ere ..
-5-
1062398
~aintained constant :
For ~PD~ I/l For EPD~ I/2
-
~eptane 15.5 Toluene 15.5
Ethylene Z70 Ethylene 300
Propylene 700 Propylene 675
1,4-hexadiene 0.12 Ethylidene o.i
norbornene (4 % by
weight solution in
toluene)
CO~OE:NTRA~I!IONS 0~ CJL~
VO (OBu)3: 0.21 m.mole/liter of heptane (for EPDM I/l)
0.047 m.mole/liter of toluene (for EPDM I/2)
Cl3Aa2 (C2H5)3: 2.1 m.mole/liter of heptane (for EPDM I/l)
0.47 m.mole/liter of toluene (for EPD~ I/2)
The properties are set forth in Table I below.
TAB~E I
EP~ ~ NORDæ~ 10?0* CO~TRO~
_ I/l I/2 I/3
% by weight propylene42 40 41
in polymer
~ r~nt ~ieooslty 2.58 2.85 3.32
Iodine number 5.2 6-3 8.6
(l~i) at 130~C. 60 83 70
~O~WIA~IONS AND PROPE~IES
olymer 100 100 100 . 100
~1 40 40 55 38
~AF Black 7
dulu~ of elongation16 14.4
(100 ~ g/cm2
o8. ~) 32. 6 37 37 34
S~ ~aeY at 20C. 87 82 83 100
-6-
, . . . .
' ` 106Z3g8
TABLE I cont'd
Test No.
~IP~lM EI~D2M NOR/DEL 1070* CQNTROL
Termonomer1,4-Hexadiene Ethylidene 1,4-Hezadiene
norbornene
* Nordel 1070 is a trademark of DuPont de Nemours, representing an
ethylene-pro~ylene-1,4-hexadiene copolymer.
~ he control con~ist~ of a mixture of 65 ~ by ~eight
of SBR 1500 and 35 % by ~elght of polybutadiene.
It can be ~en that vie~ed from the standpoint of their
~ 10 use as tire tread, the~e EPDM polymers have an insufficient
- 3kid resistance index of les~ th~n 90.
~amDle 2
In thi~ e~ample, the properties of ~arious conventional
polymer6 of ~PDM type are compared ~ith tho~e of conventional
csnjugated diene elastomer~. The propertie~ are set forth in
~ Table II.
:. ~
. Natural~or~el Nordel
Elastomei SBR 1500 rubber 1040* 1070
.. . . _ . .. _
~ulc~n1 zing S/Santocure S/Santocure S/TMTMS/MBT S/TMT~S/
. system MBT
; Pormulation: 50 5 5 70
Carbon bla¢k
Oil 5 8 40
~i~'' Polymer 100 100 100 100
. .
~odulu~ of
elongatlon
` (100~), ~ cm219.7 26.5 18 13.5
~ 30 Hy tece~)lo~s32 . 22.5 31.5 33.5
- SRT inde~ at 20oc. 100 70 74 76
L ~
.
1 0 62398
It ie noted that the SR~ inde~ of the EPDM~ i8 l~w
compared with that of the butadiene-styrene copolymer (SBR 1500)
marketed by Shell. It i~ insufficient to ma~e thege EPD~s
~uitable for use in tire tread3.
* Nordel 1040 is an ethylene-propylene-1,4-hexadiene
copolymer marketed by DuPont de Nemour~.
Santocure (n-cyclohexyl-mercaptobenzothiazole-sulienamide)
$8 marketed by ~onsanto.
TM~æ (tetramethylthiuram~monosulfide) is marketed under
the tradename ~oNE~ by the ~augatuck Chemi¢al C~.
~BT (mercaptobenzothiazole) i8 marketed under the trade-
name C~PTAX by Vanderbilt Company~ In¢.
Esam~le 3
This esa~ple describes the manufacture of a tetrapolymer
- in a¢cordan¢e with the in~ention, namely ethylene-propylene-e-
thylidene norbornene_5-phenyl-2-norbornene.
The polymerization is effe¢ted batchwise in a reactor into
~hi¢h toluene 1~ introduced at 200.~ it being then saturated
for 25 minutee ~ith agitation by means of a stream of ethylene
and propylene ~bi¢h had pre~iouely been mi~ed. ~he rate of
flow of ethylene i~ 1.2 liters/minute and that Or propylene 0.6
liters/minute.
.~ . .
~here are then introduoedS
- 1.5 c¢. Or ethylidene norbornene
- ~ariabls guantities of 5-pheny1-2-norbornene
- 0.25 m.mole of V0 (OBu)3 di~sol~ed in toluene
- 2,50 m.mole of Cl3Al2 ~C ~5)3 disso~red in toluene
and the rates of flo~ of ethylene and propylcne are modifled
by ohanging to 1.6 liter/minute and 0.8 liter/mlnute, respeo-
3 ti~ely. The reaotlon i9 stopped after 20 ~inutes by the addit~on
~ o~ acetone~ and the polymers are reco~ered.
- The following formulation i8 used (part~ by ~eight)
.
_ ~ .
. - ~ .
10 62 39 8
- polymer 100
_ carbon blacl~ 65
- oil 25
_ ZnO
- ~tearic acid
- ~lfur 2. 2
_ ~hcr~as 0.6
_ MBT 0.2
The properties are ~et forth in Table III.
~ABI E III
.
~est No~ III/l II~/2 II2/3 III/4
_ . .
S_phenyl-2- g- 3 g 5 g- 8 g.
norborne~e introduced
into the reac~ion
Weight o~ polymer
obtained 28 g. 27 gO 2604 g.25.4 g.
% by ~eight of 5- 0 6 9 12
phenyl 2-norbornene
in the modified EPDM
~ by weight of propylene 37 35 34 32
~n the modified EPD~
i~herent ~iscosity 2.50 2.63 2.47 2.53
(dl/g)
~itreous transition 51C. _46C. _44C. _40C.
temperature
modul~s of elong~-
tlon (100 %), kg/cm2 24.5 25 22 2~.5
~ystere~is 109~ at 27.7 30.1 29.4 - 32.6
60¢- ( %)
SCott fracture: 207 236 248 260
~up.~ure force
~/cm2)
Elongatiqn at 475 512 540 540
rUPtUre (~)
S~ inde~ at 20C. 100 112 118 126
. .
... _g_
. . .
- . . . . . _ _
.. . .
.
~ . ' ' ' -~ . . ,; ' '
106Z398
It can be noted that this EPDM modified in accordance
with the invention ~hows a substantial improvement in the 6kla
resistance index without substantial los~ of the hysteresis
properties ~urthermore, it i~ noted that the increase in the
skid resistance index is a direct function of the amount of
5-phenyl norbornene in the polymer.
Example 4
This example relates to the tetrapolymer ethylene-
propylene-1,4-hexadiene_5-phenyl-2-norbornene oontaining varying
amounts of the hindering monomer.
The polymerization is effected continuously ~ith the
following rates of flow in liters/hour:
heptane 15.5
ethylene 175
propylene 450
1,4-hexadiene 0.160
with the following concentration~ of catalyst:
VO(o Bu)3: 0.142 m. mole/liter in heptane
C134 2(C2H5)3: 1.14 m. mole/liter in heptane
The formulation of the mixture~ i~ identical to that
of E~ample 3.
~he properties are ~et forth in ~able IV.
;~ `.
-10_
_ . .
. .
~06Z398
o~
~1 ~ ~N N 1
N
U~ O --
:
:' .
~ ~ 2 ~ ~D
P~ N CO g~ o ~1 ~I
. ..
.....
N
N U~ N g~ N ,~
'-'' ~
.'. ~
.1 8 u~ ~
æ æ ~ ~ o
.,
~ 3~ b
., .
.
.
. . ... . .
. . ..
106Z398
There can be noted a substantial ~mpro~rement in the
~kid re~stance index without substantial reduction in the h~s_
tere~i~ properties. The mechanical properties, particularly
the Scott fracture, are also improved.
Fig. 1 shows the ch~nge in the SRT inde~ (on the
ordinate) as a function of the amount of 5-phenyl-2-n~rbo~nene
incorporated (on the ab~cissa).
Fig. 2 sho~s the obange in the hysteresis 1058 at
60C. (on the ordinate) as function of the amount of 5-phenyl-2-
norbo~nene incorporatea (on the abscis~a).
Pig. 3 sho~e the change in the S~T index (on the
ordinate) as a function of the h~steresis 1088 at 60o0. (on
the abscissa). The compromise bet~reen road adherence and hyste-
resis 1088 is obtained by mea~s: 1
a) of ethylene-propylene-1,4-hesadiene-5-phenyl-2-
norbornene polymers (curve a), or
b) of a con~entional 1,4-heYadiene E~!Dlll (~ordel 1660)
by modifying the percentages o~ carbo~ black (cur~e b) lrith a
formulation comprising 100 parts of pol~rmer and 75 parts of oil.
It ~8 noted that the higher the skid resistanoe index,
the poorer the hysteresis properties and that t~e best oompromi~e
bet~een road adherence and hyeteresis-propert$es i8 obtained by
means o$ tho pol~mers of the in~ention.
E~cam~le 5
Thig e~mple con¢erns the tetrapolymer eth~rlene-pro-
pylene-ethylidene norbornene-2-norbornene. ne operates under the
~ame conditions as those used in E~ample 1 for Test V/l~ sdd~ng
the 2-norbo~ene lrith a oo~ce~tratio~ of 6 g./l for Te~t V/2.
!l~he ~ollow~g ~reight fomlulat~on i~ employedS polymer 100, carbon
bla¢lc 70, oi~ 40~ ZnO 4, steario aoid 1~ sulfur 2~ DS 0.6
IIBT 0.2. ~e properties are set $orth in Table V below:
(TII~DS z tetromethylthiuD-d~sulfide, Dlarketed by Naugotuck
. . ,
--12--
.:
., , - . .
0 6239 8
~hemical CO.)
~AB~E V
Test No. r/l V/2
% by weight 2-norbornene in the O 11
modified E2DM
% by weight propylene in the 41 38
mod~fied E2D~
Inherent viscosity (dl/g) 3.05 2.98
Mo~ulus of elongatio~ (100 ~)
~g/cm2 . 14.4. 14
Hygtere~is los~ at 60C. (%) 37 40
S¢ott fr~cture: rupture 202 230
for¢e kg/cm2
Elongation at rupture (%) 823 850
SR~ indes at 20C. lQO , 116
E~amPle 6
~hie exa~ple concerne the tetrapolymer ethylene-pro-
pylene-1,4-hexadiene-2-norbornene.
One operates under the same conditions as those used
in E~ample 1 for Test VI/l~ adding the 2-norbornene in a con-
oentration of 4 gD/l and 5.3g./1 in Tests VI/2 and YI/3, respec-
.` 20 ,........... .
: ti~ely. In this example, the influence Or the percentages by
.: ~eight of oil and carbon black are shown.
Formulation a) polymer 100, carbon black 100~ oil
75~ ZnO 3, ~tearic acid 0.5~ sulfur 1~ ~BT o.5, T~TDS 1.
~ormulation b) polymer 100, carbon black 70~ oil 40,
ZnO 5~ steario acid 1, sul~ur 1~ ~D~S 5~ MBT 0.5-
; ~he propertles are set forth in Table VI.
- ~AB~,~
. Te~t No. ~ VI/2 VI/3
`,j
; % by ~elght o~ 2-norbornene 0 6-5 9.5
: in the dified EPD~
.. % by ~eight Or ropyl~ne in
the moairiea EP ~ 44 42 39
Inherent ~iscosity (dl/g) 2.65 2.57 2.55
. -13-
~ . ,~ . . .. .
1062398
~A13I.E VI cond't
~e~t No. I/ rI/2 VI/3
llodulus of ~longation a) b) a) b) a) b)
(100 ~), k~cm2 _
13 16.1 12.7 14.4 12.4 14.5
Hy~tere~is 108~3 at 60C.
( % ) 41.3 32.6 44.1 35.5 45.4 37.3
Sl~ indeY at 20C. 114 100 125 111 1~4 118
Scott fracture: rup- 179 203 179 216 181 233
ture forc~ kg/cm2
ngation at rupture 693 640 730 726 747 737
It is noted that the ~nvention applies to all the
modified EPDMs ~hate~er the fo~ulation used for the vulcanizers~
sinoe it i8 the nature of the polymer which i8 modified.
Exam~le 7
In ~his example, there are de~cribed the properties
(see !I!able VII) of the tetrapolymer# obtained by the ~anner of
procedure set forth in E~;ample 4 with the follo~ng different
derlvatlvea of norbornene:
5-chloromethyl-2-norbornene
5,6-dimethyl-2-norbornene
5-he~yl-2-norbornene
(5~2~1,02'6) tricyclo-8-decene
,. .
.
.: ~0
:. . .
- , . .
106Z398
~,Q
n h o~ N N O ~ ~ O
. N ~ ,~
~ ~ N t~ ~ 2 2
"
., ~N C~
HCN O ~ 0 C~i ~ O N N
-~ O ~ ~ ~ ~1
b I ~3 o FJ ,i ~ W `D
~ .
:' . ~
~ ~1 o ~ æ æo~ 8
~ ~ 3 ~ 7 i ~7
--15--
~` :
1062398
4 1 these modified EPDM polymers contatn 2% 1,4-
heYadiene a~d 35~ propylene by ~eight. The Yulcanized products
studied ha~e the formulation: polymer 100, carbon black 65,
oil 25, ~tearic acid 1, sulfur 2.2, T~TMS 0.6, MBT 0.2.
There i9 noted a substantial increase in the skid
resistance index (wet skid index) associated with ~ufficient
mechanical and hysteresis properties.
.
:
" '' '
.
. , .
, 30
-16-
';
- - . . . ~ . ~ . . _.
.. :
- ,
~ ~ .
