Note: Descriptions are shown in the official language in which they were submitted.
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1 General purpose rubbers are employed in the manu
2 facture of a wide variety of rubber articles including
3 automotive tires. The term "general purpose rubber" as
4 used in the present specification means the highly un-
saturated rubbers of commerce:
6 styrene butadiene rubber (SBR)~ polyisoprene, polybuta-
7 diene and natural rubber. While these rubbers exhibit
8 excellent physical properties in their vulcanized state,
9 they are sub~ect to attack by elemen-tal oxygen, especially
ozone. The resistance to oxidation and oxidative degen-
11 eration may be improved by the addition of an antio~idant
12 or antiozonant at a concomitant increased cost in the rub-
13 ber product.
14 It is well known in the art to improve the ozone
resistance of such general purpose rubbers by blending the
16 general purpose rubber ~GPR) with an EPDM terpolymer. See,
17 for example, United States Patent 3~492,371.
18
19 It has been found that the EPDM rubber may be
made more compatible with the GPR by brominating the EPDM.
~1 See~ for example, United States Patent 3,524,826. The
22 disclosures of that patent teach that a requirement for
23 operability of the invention is that the EPDM ccntain at
24 least one wt. ~ bromine. The blends so formed have im-
proved ozone reslstance in addltion to outstanding physi-
26 cal properties.
27 Heretofore, although compositions of GPR and
28 EPDM demonstrated improved ozone resistance, they were
29 lacking in flex properties and therefore had limited ap-
plication in tire flexing components.
31 It has surprisingly been discovered that tire
32 ~idewalls and coverstrips having superior ozoneJ flex and
,~ ~
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weather resistance can be prepared rrom vulcanizates based
on binary ~lends of 70-75 wt. ~ of a general purpose rub-
ber and 25-30~ of a halogenated EPDM.
The compositions so formed have excellent tensile
strengths. These compositions are non-staining and do not
require costly antidegradants for stability.
This invention relates to a method for improving
the flex, ozone and weather resistance of general purpose
rubbers. In particular~ thls invention relates to a blend
o~ general purpose rubbers comprising about 70-75~ of a
general purpose rubber and 25-30 wt. ~ of a halogenated
EPDM. The term l'EPDM" as used in the speciflcation and
claims is used in the sense of its definition as found in
ASTM D-1418-64, and is intended to mean a terpolymer con-
taining ethylene and propylene in the backbone and diene
enchainment with residual unsaturation in the sidechains.
Illustrative methods for producing these terpolymers are
found in U.S. Patent 3,280,082, British Patent 1,030,989
and French Patent 1,386,600.
More particularly, the present invention
concerns a method for improving the weather resistance
flex and ozone resistance of tire flexing components
prepared from blends of general purpose rubbers, said
blends comprising 50 to 60 percent by weight of natural
rubber, the balance of said blends being styrene butadiene
rubber or polybutadiene rubber which comprises incorporat-
ing into the tire flexing composition about 25 to about
40 parts per hundred based on the general purpose rubber
blend of a chlorinated EPDM containing about 0.1 to about -
4.0 weight percent chlorine.
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The term "tire flexing component" as used in
the specification and claims means automotive or truck
tire sidewalls, coverstrips or treads.
The preferred polymers contain about 45 to about
80 wt. % ethylene and about 2 to about 10 wt. ~ diene
monomer. The balance of the polymer is propylene. Pref-
erably, the polymer contains 50 to 60 wt. % ethylene,
e.g., 56 wt. ~, and about 2.6 to 4 wt. ~ diene monomer,
e.g., 3.3 wt. %. The diene monomer is a non-con~ugated
diene. Illustrative of these non-con~ugated diene mono-
mers which may be used in the terpolymer (EPDM) are~hexa-
diene, dicyclopentadiene, ethylidene norbornene, methylene
norbornene, propylidene norbornene and methyltetrahydro-
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~OS6S3~
1 indene. A typical EPDM is Vistalon 3509 (Exxon Chemical
2 Company, U.S.A.), a polymer having a Mooney Viscosity at
3 212F. of about 90 prepared from a monomer blend having an
4 ethylene content of about 56 wt. ~ and a non-con~ugated
diene content (methylene norbornene) of about 2.6 wt. ~.
6 Typical of an EPDM containing ethylidene norbornene as a
7 diene monomer is Vistalon 4608 (Exxon Chemical Company,
8 U.S.A.), a polymer having a Mooney ~iscosity a~ 260F. of
9 about 62, and an ethylene content of about 56 wt. ~.
Methods for preparing halogenated EPDM are well
11 known in the art. The halogenated polymers may be pre-
12 pared by reacting an EPDM consisting of ethylene, an alpha-
13 olefin other than ethylene~ and a small amount of non-con-
14 jugated diolefin with a halogen or halogens, such as chlor-
ine or bromine in a chlorinated hydrocarbon such as carbon
16 tetrachlorideg chl~roform, trichloroethylene, tetrachloro-
17 ethylene, or monochlorobenzene in the presence or absence
18 of a free radical initiatorg e.g., W light or chemical
19 initiators, etc. When a mixture of chlorine and bromine
is used, usually bromination is effected first and chlori-
21 nation followsO
22 Illustrative of chlorinated EPDM is chlorinated
23 Vistalon*6505 (Exxon Chemical Company, U.S.A.) having the
24 following properties: ethylene content, 48 wt. ~; ethy-
lene norbornene content, 9 wt. ~; and a chlorine content
26 of o.65 wt. ~. The polymer has an iodine number of 18.6
27 and a Mooney Viscosity ML 260 of 67.
28 The chlorinated EPDM usefu~ in the practice of
29 this invention contains ab~ut 0.1 to about 4 wt. % chlorine,
more preferably about 0.5 to about 3 wt. ~ chlorine, most
31 preferably about o.65 to about 2.5 wt. ~ chlorlne, e.g.g
* Trade Mark
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about ~7 to about 1.5 wt. % chlorine. As will be seen
in the examples, a further preferred range for the
chlorinated EPDM is from about O.l to about 0.9 wt. %
chlorine.
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1 The chlorinated EPDM blends o~ this invention
2 comprise at least 25 parts per hundred by weight of chlori-
3 nated EPDM based on the general purpose rubber. Prefer-
4 ably, the composition comprises about 25 to about 40 phr
chlorinated EPDM; more preferably about 25 to about 35 phr;
6 most pre~erably about 25 to about 30 phr.
7 The advantages of the instant invention m~y be
8 more readily appreciated by reference to the followlng
9 examples~
EXAMPLE 1 - Halogenation of EPDM
11 A. Typical Solution Halogenation Procedure
12 A 5-1 round bottom ~lask was fitted with stirrer,
13 condenserJ thermometer~ and a tem~erature controller. Nor-
14 mal heptane (3 liters) was placed into the ~lask and heated
to 80~C. EPDM (150 g) was cut into small pieces~ placed
16 into the flask, and stirred ~or 6-24 hours until completely
17 dissolved. N-halosuccinimide and 0.20 g o~ benzoyl per-
18 oxide were added and the mixture was stirred for 4-33 hours
19 to effect the halogenation. The mixture was cooled to
ambient and the insoluble by-products allowed to settle.
21 The solution was decanted into a separating funnel and the
22 polymer was precipitated by slowly adding the heptane so-
23 lution to 2 volumes of vigorously stirring acetone. A~ter
24 drying to constant weight under vacuum at 40C.~ Ca. 146 g
of polymer was recovered.
26 B. Typical Neat Halogenation_Procedure
27 EPDM (100 g), 1,3-dihalo-5,5-dimethylhydantoin
28 (DMK) and (Optionally) O.5 g o~ benzoyl peroxide were
29 thoroughly blended on a cool rubber mill. TAe amount o~
DMH was chosen such that the theoretical amount of reac-
31 tive halogen was 0.5-1.0 g. The mixture was then heated
32 between mylar sheets in a hydraulic press at 320~F. for
~051~53~
1 20 minutes to e~fect the halogenation.
2 EXAMPLE 2 - Polymers Pre~ared Via Solution Chlorination
3 ~arious ethylene-propylene-diene monomer poly-
4 mers were chlorinated by the solution method~ set forth in
Example 1 using N-chlorosuccinimide as the chlorinating
6 agent. The results are shown in Table I~
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1 EXAMPLE 3
2 Various blends of general purpose rubber were
3 prepared using EPDM) choro-EPDM and halogenated butyl rub-
4 ber in an effort to improve the physical properties of the
general purpose rubber. All the vulcanizates described in
6 this example were press cured for 30 minute9 at 307F.
7 Formulations used in this example are as follows:
8 ~ s~_e~ hY~E~
9 Elastomer as ~hown
Carbon Black ~F~F) 50
11 Plasticizer (Flexon 580 oil) 12
12 Sunolite 127 wax 1.5
13 S~earic acid
14 Zinc oxide 3
Sulfur 0.4
16 Mercaptobenzothiazyl-
17 disulfide (MBTS) 0.6
18 Alkylphenol polysulfide
19 (Vul~ac #5) 2~0
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1 EXAMPLE 4
2 ~arious compositions were prepared in a sidewall
3 formulation. The samples were press cured ~or 30 minutes
4 at 307F. The formulation used in the example was as
~ollows: .
6 Comeonent Parts per hundred
7 Elas'comers as shown
8 Carbon Black (GPF~ 60
9 ~lexon 580 Plast~cizer Oil 30
Ssearic acid 2
11 Zinc ox~ d~ 3
12 Sul~ur O 8
13 MBTS O . 8
14 Vult2c #5 1.5
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1 Run 5 of Table II and Run 10 of Table III show
2 the current state of the art in that in order to achieve
3 the outstanding properties shown, 45 phr of specialty
4 elastomer is required. The composition o~ this inven-
tion on the other hand (Runs 1, 2, 6 and 7) requires only
6 25-30 phr to achieve the same results, resulting in ob-
7 vious economics.
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