Note: Descriptions are shown in the official language in which they were submitted.
2093~0~
M~EI~AL FILLED EPDM/lEPR COMPOSlTIONS FOR
VVlIlTE SIDEWALL TII~E COMPOUNDS
S TEOEIN~CAL FIELD
The present invention relates generally to compositions for white sidewall tire
compounds. The white sidewall tire compounds comprise a blend of ethylene-
propylene-diene terpolymer, referred to herein as EPDM, ethylene-propylene
copolymer, referred to herein as EPR, or other similar olefin type polymers or blends
10 thereof with a crystallinity enhancing thermoplastic polymeric additive such as a
homopolymer of polyethylene or polypropylene as well as copolymers of ethylene/octene
and ethylenelbutene or the like. More particularly the compounds contain non-black
mineral fillers as replacements for carbon black. Oftentimes, a stain barrier skim (some
20 to 30 mils in thickness) is inserted at the interface of the black sidewall and white
15 sidewall compounds in order to prevent staining materials such as oils and antioxidants
(i.e., p-phenylenediamines) from migrating into the white sidewall compound. Thewhite sidewall compound is adhered directly to the stain barrier skim (optional) or black
sidewall of a solid or pneumatic tire using heat and some pressure and without solvents
or water based adhesives. Moreover, a thin thermoplastic film can be provided between
20 the white sidewall compound and the stain barrier skim or black sidewall to improve
adhesion therebetween.
.
BACKGROllND OF THE ~VENTION
Tires having white or decorative sidewalls are conventionally made by
25 building the white sidewall in place, applying a thin black cover strip thereover and
curing the tire. The purpose of the cover strip is to protect the white sidewall during
handling and curing so that it does not become discolored by contact with staining black
components of the tire or mold residue materials. After the tire has been cured and
cooled, the cover strip is buffed away, exposing the white sidewall. Nevertheless, the
30 white sidewall is relatively soft and can be subsequently blemished, marked or scuffed
during shipment with other tires and general handling until it is installed onto a vehicle
and thereafter.
9201013 FIR.P.US0068
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Thus, the art has recognized a need for a white sidewall compound that has
improved deformation resistance and durability over conventional compounds as well
as a white sidewall that can be applied to a tire subsequent to cure, thereby obviating
the need for the cover strip and subsequent removal operations. Also, the white
5 sidewall composition can be applied to a cured tire without the use of an adhesion
system. An example of an uncured applique being co-cured with a green tire is
described in U.S. Pat. No. 5,058,647 and an example of an uncured applique applied
to a cured tire is described in U.S. Pat. No. 5,049,220. However, neither patentteaches the use of a tougher EPDM/EPR-based compound.
10Various EPDM compounds having high crystallinity are known but not the
use thereof in white sidewalls. U.S. Patent No. 5,086,121, for instance, is directed
toward a thermoplastic olefin composition. In this composition, there is provided a
polyolefin component, such as high density polyethylene and two rubber components,
only one of which is cured by a cure package. For example, the two rubbers employed
15 may include a halogenated butyl rubber and EPDM. A certain cure package, such as
a zinc oxide system, is added so that only the halogenated butyl rubber is cured. The
second rubber component remains uncured. A preferred EPDM is a highly crystalline
terpolymer. Therefore, this pater~t discloses an uncured EPDM in the presence of a
polyolefin such as a high density polyethylene. It is further noted that such a
20 composition provides improved physical properties, such as improved tensile strength
and the like.
U.S. Patent No. 4,036,912 discloses a thermoplastic polymer blend of, for
:-example, EPDM polymer with crystalline polypropylene. The blends achieve higher
tensile strength and high structural integrity. No curing or cross linking agents are used
25 to obtain these characteristics. The polymers are mixed in a range of from about 5 parts
by weight to about 200 parts by weight of polypropylene for every 100 parts by weight
of EPDM.
.U.S. Patent No. 3,941,859 discloses a highly crystalline EPDM polymer
blended with a polyolefin to form a blend having superior tensile strength. No cure
.~
9201013 FIR.P.US0068
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package is employed. Similarly, U.S. Patent No. 3,919,358 also discloses a crystalline
EPDM blended with a polyolefin.
SUMl\/IARY OF THE I~VENTION
5It is therefore an object of the present invention to provide a white sidewall
that can be applied circumferentially in a groove of the black sidewall of a cured tire
using heat and some pressure.
It is another object of the present invention to provide a white sidewall
compound comprising blends of EPDM and EPR with thermoplastic crystallinity
10enhancing polymeric additives and non-black mineral fillers.
It is still another object of the present invention to provide a white sidewaU
compound that can be applied to the black sidewall of a tire without the use of
adhesives.
Yet another object of the present invention is to provide a thermoplastic layer
15of material that can be interposed between the white sidewall and black sidewall of the
tire for the application of the former thereto.
It is a further object of the present invention to provide a method for
applying a white sidewall to the black sidewall of a tire, without the use of adhesives.
It is still another object of the present invention to provide a tire at least
20partially cured and having a black sidewall area featuring a circumferential groove to
which a non-black mineral-filled, thermoplastic polymeric composition of matter is
adhered.
In general the present invention relates to a non-black mineral-filled white
sidewall compound prepared from a thermoplastic polymeric composition of matter
25comprising (A) 100 parts by weight of a polymer blend comprising (1) from at least
about 10 to 95 parts by weight of a polyolefin having from about 0.5 to about 13percent by weight crystallinity, the polyolefins being prepared from monomers having
at least 2 carbon atoms and mixtures thereof; and (2) from about 5 to 90 parts by weight
of a thermoplastic crystallinity enhancing polymeric additive; (B) from about 20 to 200
30parts by weight of a filler selected from the group consisting of reinforcing and non-
9201013 F~R.P.US0068
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- 4 -
reinforcing fillers and mixtures thereof per 100 parts of the polymer blend; and (C) from
about 20 to 150 parts by weight of a processing material and mixtures thereof, per 100
parts of the polymer blend; the white sidewall compound being adherable to
conventional, cured tire sidewalls without the use of solvents or water-based adhesives.
Also included in the invention is a method for applying a thermoplastic non-
black mineral-filled white sidewalI compound to conventionally cured tire sidewalls
comprising the steps of providing a tire at least partially cured and having a sidewall;
applying an uncured non-black mineral-filled white sidewall compound to the tiresidewall to form a white sidewall; and bonding the white sidewall to the tire sidewall
ur.der sufficient pressure and heat to provide acceptable adhesion without the use of a
solvent or a water based adhesive.
The present invention also provides a tire having a sidewall area and a non-
black mineral:filled white sidewall compound adhered thereto prepared from a
thermoplastic polymeric composition of matter comprising (A) 100 parts by weight of
15 a polymer blend comprising (1) from at least about 10 to 95 parts by weight of a
polyolefin having from about 0.5 to about 13 percent by weight crystallinity, the
polyolefins being prepared from monomers having at least 2 carbon atoms and mixtures
thereof; and (2) from about 5 to 90 parts by weight of a thermoplastic crystallinity
u enhancing polymeric additive; (B) from about 20 to 200 parts by weight of a filler
20 selected from the group consisting of reinforcing and non-reinforcing fillers and
mixtures thereof per 100 parts of the polymer blend; and (C) from about 20 to 150 parts
by weight of a processing material and mixtures thereof, per 100 parts of the polymer
blend.
At least one or more of the foregoing objects which shall become apparent
25 to those skilled in the art are described in greater detail with reference to the
specification which follows.
9201013 FIR.P.US0068
5 209~)aO~
;
BRIEF DESCRIPrION OF THE DRAWINGS
Fig. 1 is a side elevation of a tire depicting a white sidewall;
Fig. 2 is a fragmentary enlarged section of the molded tire prior to forming
a circumferential groove therein;
Fig. 3 is a fragmentary enlarged section of the tire depicted in Fig. 1 similar
to Fig. 2 but depicting a circumferential groove in the sidewall area;
Fig. 4 is a fragmentary further enlarged cross-section, taken substantially
along line 4-4 of Fig. l;
Fig. 5 is a further enlarged exploded section depicting the white sidewall of
10 the present invention, a layer of thermoplastic film and the circumferential groove in the
black sidewall area of the tire; and,
Fig. 6 is a diagrammatic flow chart presenting the steps of the method
according to the present invention.
PRE~ERRED EMBODIl\~ENT OF TIIE INVENIION
As noted hereinabove, the white sidewall compounds used in the present
invention comprise blends of EPDM, EPR or other similar olefin type polymers
prepared from monomers having at least 2 carbon atoms. The term EPDM is used in
the sense of its definition as found in ASTM-D-1418-85 and is intended to mean a20 terpolymer of ethylene, propylene and a diene monomer with the residual unsaturation
portion of the diene in the side chain. Illustrative methods for preparing such
terpolymers are found in U.S. Pat. No. 3,280,082, the disclosure of which is
incorporated herein by reference. The preferred polymers have from about 50 to about
95 weight percent ethylene and from about zero to about 12 weight percent of the diene
25 with the balance of the polymer being propylene or some other similar olefin type
polymer.
The diene monomer utilized in forming the EPDM terpolymer is preferably
a non-conjugated diene. Illustrative examples of non-conjugated dienes which may be
employedaredicyclopentadiene,alkyldicyclopentadiene, 1,4-pentadiene, 1,4-hexadiene,
1,5-hexadiene, 1,4-heptadiene, 2-methyl-1,5-hexadiene, cyclooctadiene, 1,4-octadiene,
9201013 FIR.P.US0068
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- 6
I ,7-octadiene,5-ethylidene-2-norbornene,5-n-propylidene-2-norbornene,5-(2-methyl-2-
butenyl)-2-norbornene and the like. A typical EPDM is Vistalon~ MD-744 (Exxon
Chemical Co.) a terpolymer having a Mooney Viscosity (ML14 at 125C) of about 52;
an ethylene/propylene (E/P) ratio of 60/40 weight percent and 2.7 weight percent of
5 unsaturation.
Particularly useful and preferred are EPDM's and EPR's having a high
degree of crystallinity as opposed to amorphous (non-crystalline) EPDM's or EPR's,
although the latter can also be employed. Examples thereof include Royalene~ 375- (Uniroyal Chemical Co.); and EPsyn~ 5508 and EPsyn0 MDE-249 (Copolymer Rubber
1~ & Chemical Corporation). Royalene~ 375 has a Mooney Viscosity (MLJ4 at 125C) of
about 50.8; an E/P ratio of 75/25 weight percent and about 2.0 weight percent ofunsaturation (dicyclopentadiene) and a weight average molecular weight of
approximately 190,000. EPsyn0 5508 has a Mooney Viscosity (ML/4 at 125C) of
about 55.6; an E/P ratio of 73/27 weight percent and about 3.7 weight percent of15 unsaturation. EPsyn0 MDE-249, an experimental terpolymer has a Mooney Viscosity
(ML/4 at -125C) of about 56; an E/P ratio of 71/29 weight percent and about 1.7weight percent of unsaturation (5-ethylidene-2-norbornene) can also be employed. Also
useful in preparing a white sidewall compound for practice of the present invention is
Vistalon0 MD-744 (Exxon Chemical Co.) an EPDM rubber having a Mooney Viscosity
20 (ML/4 at 125 C) of about 53; an ethylene/propylene (E/P) ratio of about 60/40 weight
percent; about 2.7 weight percent of unsaturation (5-ethylidene-2-norbornene) and a
weight average molecular weight of approximately 360,000. A more complete
discussion of such polymers is set forth in our copending application, U.S. Ser. No.
07/594,457, the subject matter of which is incorporated herein by reference.
The term EPR is used in the sense of its definition as found in ASTM D-
1418-85 and is intended to mean a copolymer of ethylene and propylene. The preferred
copolymers contain from about 30 to 95 weight percent ethylene with the balance to
total 100 weight percent being propylene. A typical EPR is Vistalon0 719 (Exxon
Chemical Co.) having an E/P ratio of about 75/25 weight percent.
9201013 FIR.P.US0068
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Also, useful in forming the white sidewall compounds of the present
invention is a copolymer of ethylene and butene. This particular copolymer has about
82 weight percent ethylene with the balance to total 100 weight percent being butene.
A typical ethylene/butene copolymer is GERS- 1085 (Union Carbide Corporation3 having
an Mw, as measured by GPC of at least about 221,000. Other similar olefinic polymers
(e.g., ethylene/octene copolymer) can be used to practice this invention. Generally
speaking any polyolefin having more than about 2 percent by weight crystallinity and
selected from the group consisting of polyolefins prepared from monomers containing
at least 2 carbon atoms can be employed. For purposes of discussion herein, references
- 10 to EPDM, EPR or similar olefinic polymers are intended to include any of the
polyolefins of the present invention.
To be useful as a white sidewall compound in the present invention it is
preferred that the EPDM have from about 0.5 up to about 13 weight percent crystallinity
from the ethylene component; an Mn as measured by GPC of at least about 30,000 up
-
to about 120,000, and an Mw, as measured by GPC of at least about 100,000 up to
about 375,000. Similarly, the EPR should have from about 0.5 weight percent to about
13 percent crystallinity (ethylene); an Mn, as measured by GPC of at least about 30,000
up to about 120,000, and an Mw, as measured by GPC of at least about 100,000 up to
about 375,000. We have found that the selection of an EPDM or EPR having high
crystallinity (at least 2 percent by weight) and weight average molecular weight (Mw
= 100,000) is preferred to provide a white sidewall compound which does not re~uire
curing prior to application, and which does not re~uire any type of adhesive, solvent-
based or the like, to adhere the white sidewall to the black sidewall of the tire.
In addition to the foregoing polyolefins, amorphous polyolefins having up
to about 0.5 percent by weight crystallinity and prepared from monomers having at least
2 carbon atoms can be employed. In order to have utility in this invention polyolefins
having less than two weight percent crystallinity may be blended with varying amounts
of one or more of the thermoplastic crystallinity enhancing polymeric additives listed in
Table I. Again, for each of discussion, this component of the polymeric composition
of matter may be referred to herein as EPDM, EPR or other polyolefin.
9201013 FIR.P.US0068
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.
The thermoplastic crystallinity enhancing polymeric additives that may be
employed in the polymer blends of thc present invention and are selected from the group
consisting of polyolefin homopolymers, random copolymers and block copolymers.
Homopolymers include polyethylene and polypropylene. Random copolymers include
5 poly(ethylene~propylene) copolymers. Block copolymers include poly(ethylene-b-octene) and poly(ethylene-b-butene) copolymers. Mixtures of the foregoing polymers
can be employed or a single polymer can be employed to comprise from about 10 to 95
`~ parts by weight of EPDM or EPR polymer blended with from about 5 to 90 parts by
weight of a crystalline enhancing polymeric additive for a total of 100 parts of polymer.
10Typical examples of commercially available thermoplastic crystallinity
enhancing polymeric additive additives that can be blended with EPDM, EPR or other
similar polyolefims, materials have been set forth in Table I along with peak melt
temperatures and percent of crystallinity by differential scanning calorimetry (DSC) at
a heating rate of 10C per minute.
9201013 FIR.P.US0068
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.. g
TABLE I
Thermopl~stic Crystallinity Enhancin~ Polnneric Additives
ETHYLENE HOMOPOLYMERS Tm. C* % crvstallinity
POLYWAX 2000a 128 89.9
POLYWAX 3000b 121 93.2
LDPE 722C 112 39.1
LDPE 132d 109 27.7
LDPE 640e 113 39.9
LDPE 768f 119 45.8
LDPE CG-2523g 111 53.6
HDPE 12065h 134 66.8
HDPE 62013i 131 61.2
PETROLlTE E-202Q1 116 85.9
POLYPROPYLENE HOMOPOLYMERS
EASTOBOND D-?682-109Sk 153 4.7
A-FAX 5001 155 5.8
ETHYLENE/PROPYLENE COPOLYMERS
RLX-020m 152 35.8
ETHYLENE/OCTENE COPOLYMERS
ATTANE 4003n 123 36.9
ATTANE 4001 124 35.0
DOWLEX 2047AP 124 39.8
DOWLEX 2045q 124 42.2
DOWLEX 2038r 127 53.6
DOWLEX 2027S 113 41.5
ETHYLENE/BUTENE COPOLYMER
GERS-1085t 71 2.3
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- 10-
*) Peak Melt Temperature
a) High melting polyethylene having a molecular weight of about 2000 (Petrolite)
b) High melting polyethylene having a molecular weight of about 3000 (Petrolite)
:r C) Low density polyethylene resin, density 0.916 (Dow Chemical)
. . 5 d) Low density polyethylene resin, density 0.919 (Dow Chemical)
. e) Low density polyethylene resin, density 0.922 (Dow Chemical)
f) Low density polyethylene resin, density 0.930 (Dow Chemical)
g) Low density polyethylene resin, density 0.923 (Dow Chemical)
-` h) High density polyethylene resin, density 0.94 (Dow Chemical)
i) High density polyethylene resin, density 0.94 (Dow Chemical)
j) Petroleum-derived oxidized hydrocarbon having an acid number of 22
(Petrolite)
k) Amorphous polypropylene (Eastman Chemical)
1) Amorphous polypropylene (Himont, USA, Inc.)
m) Ethylene/propylene copolymer (2% Ethylene) molecular weight about 400,000
(Phillip's Petroleum)
n) Ethylene-octene copolymer, density 0.905 (Dow Chemical)
o) Ethylene-octene copolymer, density 0.912 ~Dow Chemical)
p) Ethylene-octene copolymer, density 0.917 (Dow Chemical)
q) Ethylene-octene copolymer, density 0.920 (Dow Chemical)
r) Ethylene-octene copolymer, density 0.935 (Dow Chemical)
s) Ethylene-octene copolymer, density 0.941 (Dow Chemical)
t) Ethylene-butene copolymer (about 82% ethylene), density 0.884 (Union
Carbide Corporation)
The thermoplastic crystallinity enhancing polymeric additives are necessary,
or of greater importance, when the polymer blend comprises increasing amounts ofpolyolefins having less than 2 percent by weight crystallinity. However, even if the
30 polyolefin selected is exclusively one having crystallinity greater than 2 percent by
9201013 FIR.P.US0068
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- 11
weight, the presence of a thermoplastic crystallinity enhancing polymeric additive of the
present invention provides deformation resistance, abrasion resistance, durability,
blemish resistance and the like.
The composition employed to form the white sidewall compound comprises
5 a blend of 100 total parts by weight of EPDM,EPR or other similar type olefin type
polymers, including mixtures of two or more types, and a thermoplastic crystallinity
enhancing polymeric additive to which is added basically fillers and processing oil as
well as optionally other components, all of which are discussed hereinbelow.
With respect first to the non-black mineral fillers, suitable fillers are selected
10 from the group comprising of hard clays, soft clays, chemically modified clays, calcined
clays, mica, talc, alumina trihydrates, calcium carbonate, titanium dioxide, amorphous
precipitated hydrated silica, silicates, silicon dioxide and mixtures thereof. These fillers
may, either partially or completely replace "black" fillers, i.e. carbon black and other
related petroleum-derived materials.
15Some four basic types of clays are normally used as reinforcing fillers for
rubber elastomers. The different types of clay fillers include; airfloated, water washed,
calcined and surface treated or chemically modified.
The airfloated clays are the least expensive and most widely used. They are
divided into two general groups, hard and soft, and offer a wide range of reinforcement
20 and loading possibilities. Hard Clays are used in the amount of about 20 parts to about
200 parts per 100 parts of polymer (phr), preferably in an amount from about 65 to 175
phr. Any commercially available hard clay may be used. The preferred airfloated hard
clays used are: Suprex0, Barden R0; LGB0 all commercially available from J.M.
Huber Corporation.
The airfloated soft clays are used in the amount of about 20 parts to about
200 parts per 100 parts of polymer(phr), prefera~ly in an amount from about 75 to 175
phr. The preferred airfloated soft clays used are Paragon0; Hi-White R0, and K-780
commercially available from J.M. Huber Corporation.
Water washed clays are normally considered as semi-reinforcing fillers. This
30 particular class of clays are more closely controlled for particle size by the water-
9201013 FIR.P.US0068
2095~04
- 12-
fractionation process. This process permits the production of clays within controlled
particle size ranges. The preferred ranges of water washed clays are very similar to the
preferred amounts of airfloated soft clays mentioned hereinabove. Some of the
preferred water washed clays include Polyfil~ DL, Polyfil~ F, Polyfil~ FB, Polyfil~ HG-
S 90, Polyfil0 K and Polyfil0 XB, all are commercially available from J.M. Huber
Corporation.
The third type of clay includes the calcined clays. Clays normally contain
approximately 14 percent water of hydration, and most of this can be removed by
calcination. The amount of bound water removed determines the degree of calcination.
The preferred ranges of calcined clays are very similar to the preferred amounts of
airfloated hard clays mentioned hereinabove. Some of the preferred calcined clays
include Polyfil~ 40, Polyfil0 70, and Polyfil~ 80, all commercially available from J.M
Huber Corporation.
The final type of elay includes the chemically modified reinforcing clays.
Cross-linking ability is imparted to the clay by modifying the surface of the individual
particles with a polyfunctional silane coupling agent. Chemically modified clays are
used in the amount of about 20 parts to about 200 parts per 100 parts of polymer(phr),
preferably in an amount from about 60 to 175 phr. Normally the specific gravity of
most clays is about 2.60 at 25 C. The preferred chemically modified clays are
commercially available from J.M. Huber Corporation and include: Nucap0 100, Nucap0
200, Nucap0 190, Nucap0 290, Nulok0 321, Nulok0 390 and Polyfil0 368.
Other useful non-black fillers include amorphous silica (silicon dioxide).
Silicas are generally elassed as wet-process, hydrated silicas because they are produced
by a ehemical reaetion in water, from which they are precipitated as ultrafine, spherical
partieles. Silica can be employed in the amount of about 20 parts to about 50 parts per
100 parts of polymer(phr), preferably in an amount from about 20 to 50 phr. The
useful upper range is limited by the high viscosity imparted by fillers of this type. Some
of the commereially available silicas whieh may be used inelude: Hi-Sil0 215, Hi-Sil~
233, Hi-Sil0 EP and Silene0 D all produced by PPG Industries. Also, a number of
useful eommercial grades of different silicas are available from J.M. Huber Corporation.
9201013 FIR.P.US0068
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Finely ground calcium carbonate is employed in the amount of about 20 parts
to about 200 parts per 100 parts of polymer(phr), preferably in an amount from about
35 to 90 phr. Calcium carbonate generally has a specific gravity of about 2.71 and is
commercially available from a number of suppliers including Harwick Chemical, J.M.
SHuber Corporation, Georgia Marble, Genstar Stone Products and Omya, Inc.
Titanium dioxide is employed in the amount of about 5 parts to about 80
parts per 100 parts of polymer(phr), preferably in an amount from about 10 to 50 phr.
Both the rutile and anatase form of titanium dioxide may be used, however, the rutile
form is preferred and includes such products as TiPure~ R-960, which is a fine, white
10powder having a specific gravity of 3.90 and commercially available from DuPont Co.
Other commercially available non-black mineral fillers that may be employed
to practice this invention include; talc (magnesium silicate), mica (mixtures of sodium
and potassium aluminum silicate) and alumina trihydrate.
Optional ingredients include, for example, other elastomers (e.g., butyl
15elastomer, neutralized sulfonated EPDM, neutralized sulfonated butyl) in place of minor
! amounts of the EPDM, and conventional amounts of other conventional agents, such as
zinc oxide, stearic acid, antioxidants, antiozonants, flame retardants, and the like.
With respect to the processing material, it is included to improve the
processing behavior of the composition (i.e. reduce mixing time and increase rate of
20sheet forming) and includes processing oils, waxes and the like. The process oil is
included in an amount ranging from about 20 parts to about 150 parts process oil phr,
preferably in an amount ranging from about 60 parts to about 135 phr. A preferred
processing oil is a paraffinic oil, e.g. Sunpar 150 which is available from the Sun Oil
Company. Other petroleum derived oils including naphthenic oils are also useful.25The compounding ingredients can be admixed, utilizing an internal mixer
(such as a Banbury rnixer), an extruder, and/or a two-roll mill, or other mixers suitable
for forming a viscous relatively uniform admixture. When utilizing a type B Banbury
internal mixer, in a preferred mode, the dry or powdery materials such as the fillers are
added first followed by the liquid process oil and finally the polymer (this type of
30mixing can be referred to as an upside-down mixing technique).
9201013 FIR.P.US0068
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During the construction of a tire, 20 to 30 mil film of uncured stain barrier
skim stock is applied over the black sidewall in the region of the white sidewall
circumferential groove. Once the tire has been properly cured, the white sidewall
groove featuring a 20 to 30 mil film of the stain barrier skim is buffed before
S application of the white sidewall compound. The white sidewall compound can be
extruded into a circumferential groove which is located in the black sidewall region of
the tire using heat and some pressure. The ideal temperature of the white sidewall
extrudate is between about 205 and 320F (96 and 160C). The mineral-filled white
sidewall compounds are self-adhering without the use of a solvent or water-basedadhesive. Also, due to the thermoplastic behavior of the mineral-filled EPDM/EPRcompositions of the present invention, a sulfur-accelerator cure package is not necessary.
Additionally, the thermoplastic EPDM/EPR compounds are expected to produce
excellent ozone aging and weathering resistance. As noted hereinabove, the
compositions can comprise EPDM, EPR or other polyolefin, as well as blends thereof.
The present invention can also utilize a thermoplastic film between the
EPDM or EPR white sidewall compounds descAbed herein and the black sidewall to
improve compatibility. The thin thermoplastic film of the present invention may
comprise a polyolefin prepared from a monomer or monomers having from 2 to about8 carbon atoms, such as polyethylene, polypropylene, polybutene, polyoctene and the
;~ 20 like, as well as ethylene-vinyl acetate copolymers and blends thereof. Generally, the
thickness of the film can range between from about 2 to about 20 mils although greater
thicknesses may be employed and thus, are not precluded.
Mils of thickness and peak melt temperature (as determined using the
Differential Scanning Calorimeter) for two high density polyethylene films used to
practice the invention are provided in Table II.
9201013 FIR.P.US0068
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- 15 -
Table II
Thermoplastic Films
Liner Thickness (mils! Tm. C
(by DSC)
High MW Polyethylene film
pl50a 6 139.4
p5Soa 20 140.5
a) Stamylan UH~ (Engineering Plastics - DSM)
In order to demonstrate practice of the present invention, three different
white sidewall compounds, within the scope of the disclosure were prepared. The
EPDM polymers selected included EPsyn~ MDE-249 and Vistalon~ MD-744.
Characterization of each of the polymers is presented in Table m hereinbelow.
, .
9201013 ~IR.P.US0068
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TABLE m
EPDM Polymer Characterization Studv
EPsyn~ Vistalon~
MDE-249 MD-744
ML14 at 125C 56 53
Ethylene Content, wt % 71 60
Crystallinity, wt % 9.3 <1
Tg, C ~by DSC) -47.5 -56.4
Tm, C (by DSC) 38.3 41.6
Unsaturation, % 1.7 2.7
Type of unsaturation E~a E~a
Mn 106,0Q0 73,200
Mw 332,900 360,400
Mn/Mw ratio 3.14 4.92
15 a) 5-ethylidene-2-norbornene
The white sidewall compounds of the present invention were prepared
according to the formulation presented in Table IV hereinbelow. Parts and percentages
20 are by weight, unless otherwise indicated. These examples are submitted for the
purpose of further illustrating the nature of the present invention and are not to be
considered as a limitation on the scope thereof.
9201013 FIR.P.US0068
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TABL,E IV
White Sidewall Compounds
Comp~ound No. 1 2 3
Vistalon~ MD-744 60
EPsyn~ MDE-249 ~ - 60 60
HDPE-12065 40 40
Dowlex~ 2047Aa - - 40
NuCap~ 190 clay 20 20 20
TiO2 10 10 10
Sunpa~D 150 oilb 11 11 11
Ultramarine blueC 0.30 0.30 0.30
Antioxidantd
TOTAL 142.3 142.3 142.3
;; 15
a) ethylene-octene copolymer
b) paraffinic process oil having a flash point of 495C, a refractive index of
1.4805 and specific gravity of 0.8740.
c) Inorganic blue pigment - prepared by heating a mixture of sulfur, clay, alkali
and a reducing agent at high temperatures. A colorant for rubber products,
especially white sidewall compounds.
d) 2,2' methylene-bis-(4-methyl-6-tert-butylphenol)
In order to demonstrate practice of the present inventions, a conventional
sulfur cured, black sidewall compound was prepared according to the formulation set
forth in Table V hereinbelow to which the white sidewall compounds were adhered.
9201013 FIR.P.US0068
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TABLE V
Passen~er Black Sidewall Stock
Polybutadiene 60
Natural rubber 40
S FEF carbon black (ASTM N-550) 55
Zinc oxide - 3
Stearic acid l.50
Santoflex 13a
Wax blend 3.0
Antioxidantb 1.5
Naphthenic process oil 13.0
Rosin oil blendC 4.0
Rubber Masterbatch 184.33
Crystex sulfur 2.62
Santocure NSd 0.80
TOTAL 187.7',
a) N-(l ,3-dimethylbutyl)-N'-phenyl-paraphenylenediamine
b) Polymerized 2,2,4-trimethyl-1 ,2-dihydroquinoline
c) Blend of petroleum hydrocarbons and tall oil rosin
d) N-tert-butyl-2-benzothiazyl-sulfonamide
It is also conventional to employ a stain barrier skim stock in tires having
a white sidewall so as to protect the latter from staining caused by bleeding through of
antioxidants, color of the aromatic process oils and the like which have a deleterious
25 effect on the white sidewall compound. The stain barrier skim stock composition is not
novel to the present invention, a typical formulation being presented in Table VI
hereinbelow. The white sidewall compounds of the present invention were also adhered
to the stain barrier stock.
9201013 FIR.P.US0068
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TABLE VI
Stain BalTier ~kim Stock
Skim Stock
Natural rubber 30
Chlorobutyl 25
EPDM ~ 20
Polybutadiene 25
HAF black (ASTM N-330) 30
Naphthenic process oil 10
Wax blend 3
Alkyl phenol formaldehyde resin 2
Rubber Masterbatch 145.0
Rubber Masterbatch 145.0
Zinc oxide 3.0
Stearic acid 1.20
Crystex sulfur 2.62
: Altax-MBTSa 0.70
Vultac 7lob 117
TOTAL 153.69
a) Benzothiazyl disulfide
b) alkyl phenol disulfide, sulfur content 29.4 to 31.8~ by weight, specific gravity
1.18
The thermoplastic white sidewall compositions provided in Table IV are
tubed or extruded, preferably at a temperature in excess of 132C, into a circumferential
groove located in the black sidewall of a cured tire. The groove itself is formed in the
black sidewall during the curing of the tire. Prior to application of the thermoplastic
9201013 FIR.P.US0068
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white sidewall material the groove should be buffed, preferably with a wire brush.
Buffing removes mold release residue, as well as any surface "bloom'', i.e., sulfur, oils,
etc., that may reduce the level of adhesion between the white and black sidewall.
Buffing also increases the amount of surface area between the thermoplastic white
sidewall and cured tire. In order to minimize discoloration of the white sidewall, a stain
barrier skim (about 20 to 30 mils in thickness) as shown in Table VI, can be applied to
the black sidewall during construction of the uncured tire. The width and depth of the
circumferential groove can vary.
With reference to the drawing figures, a conventional tire is depicted in
Fig. 1 generally by the numeral 10. The tire 10 is typically pneumatic and comprises
the tread 11, tread reinforcing belts 12, 13, body ply 14, inner liner 15, bead 16, first
bead apex 18, bead toe 19, second bead apex 20, sidewall 21 and shoulder 22. Because
the tire design can vary, it is to understood that the present invention is not to be limited
by the construction of any particular tire, or to pneumatic tires as opposed to solid tires.
In the manufacture of a tire having a conventional white sidewall, it is
customary to provide a stain barrier skim stock, the purpose of which is to inhibit the
migration of processing oils, antioxidants and other components that would discolor or
stain the white sidewall, A stain barrier skim stock 23 is depicted in Fig. 2 for such
purpose and is otherwise a conventional component.
In order to apply the white sidewall, generally 25, to the tire 10, a
circumferential groove 26 is provided, as depicted in Fig. 3. The circumferential
groove 26 can be formed by buffing the sidewall 21, in the region depicted by arrow
A in Fig. 2, after the tire has been cured or, it could be formed during cure in an
appropriately designed tire mold using a metal ring. The size of the circumferential
groove 26 can be varied depending upon the amount of white sidewall desired for
current styling and appearance. Generally, it may be about 0.5 to 1 inch wide (1.25 to
2.5 cm) as shown at W and approximately 0.1875 inch (0.48 cm) deep, as shown at D,
but not so deep as to exceed the thickness of the stain barrier skim stock 23. Acommon dimension is 0.75 inch wide (1.91 cm) and 0.1 inch deep (0.25 cm).
9201013 FIR.P.US0068
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The white sidewall 25 is applied to the circumferential groove 26 in an
uncured state via suitable means, such as extrusion or the like. Preferably, a thin layer
or sheet of the thermoplastic film 28 is applied between the circumferential groove 26
and white sidewall 25, to improve adhesion therebetween and provide additional stain
5 resistance. Nevertheless, the film 28 is optional.
Following application of the white sidewall 25, it is subjected to heat at about133 to 160C under slight pressure, on the order of about 8 to 200 psi, for about 5 to
30 seconds. This application of heat and pressure is sufficient to bond the white
sidewaU to the stain barrier skim stock in the circumferential groove 26 without10 necessitating the use of solvents or water based adhesives, although use of either should
not be construed as a means to practice outside the scope of the present invention. The
white sidewaU 25 is preferably about 90 mils thick, shown at T, and provides an
exterior surface 29 slightly below the exterior surface 30 of sidewall 21, as depicted in
Fig. 4. Of course, the thickness of white sidewall 25 can be varied and may be equal
15 to or greater than the depth of the white sidewall 26.
Owing to the composition of the white sidewall 25, which is harder than
conventional rubber compounds employed for white sidewalls, a more durable sidewaU
is obtained which has improved resistance to abrasion, scuffing, curbing, marring and
the like. Moreover, because the white sidewall is applied after the tire has been
20 manufactured, the use of a cover strip to protect the conventional white sidewaU during
building and curing is obviated as is the need for subsequent removal.
- Although practice of the present invention is preferred for use in the
manufacture of newly manufactured tires, post cure, it is within the scope of the present
invention to subject the tire to less than a total cure. Moreover, the method of the
2S present invention is not limited to newly manufactured tires, inasmuch as thecircumferential groove 26 could be buffed into existing tires for conversion to a white
sidewaU tire. Thus, the application can be done at the point of sale in response to
immediate demand. For such out-of-plant application, the method of the invention is
currently carried out by applying the thermoplastic white sidewall compound in the form
30 of strips or a completely formed ring. Where desired, the thermoplastic film can be
9201013 liIR.P.US0068
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used and bonding may be facilitated by the application of heat, say in the amount of
about 133-160C and pressure, say about ~ to about 200 psi.
Application of the white sidewall, according to the method of the present
invention is set forth in the block diagram flow chart of Fig. 6 and includes as a first
step providing a tire that is at least par~ially cNred and having a sidewall, box 31. Next,
a circumferential groove is formed in the sidewall of the tire, during curing, box 32.
A non-black mineral-filled thermoplastic white sidewall compound is applied to the black
sidewall of the tire, per box 33. Application includes the optional step of applying a
thin sheet of thermoplastic film between the white sidewall compound and the black
sidewall of the tire, box 34.
As discussed hereinabove, the preferred mode for the step of applying
includes the step of providing a circumferential groove in the black sidewall,
circumferentially positioned of the tire prior to curing, per box 32, or by buffing the
circumferential groove into the black sidewall post cure, per box 35.
Following application of the white sidewall compound and optional
thermoplastic-film to the circumferential groove, the method includes the step of
bonding the white sidewaU via the application of heat and some pressure, box 36. Once
the white sidewall component has cooled to room temperatures the tire is then ready for
use.
Having thus described the physical construction of a typical tire to which the
white sidewall of the present invention is applied, and the method for the application,
test results have been reported which demonstrate the degree of adhesion that is obtained
without the use of solvents, or water-based adhesives.
In the examples which follow, the white sidewall compound of Example 1
: 25 in Table IV was applied to the black sidewall compound of Table V with and without
a layer of thermoplastic film therebetween. The composition exemplified is submitted
for the purpose of further illustrating the nature of the present invention and is not to
be considered as a limitation on the scope thereof. The white sidewall compounds of
Table IV were also applied to the stain barrier skim stock compound of Table VI.
9201013 FIR.P.US0068
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Adhesion test pads of the various stock were prepared for peel adhesion testing
according to the following procedure.
Detailed Peel Adhesion Test Procedure
s
A thermoplastic white sidewall compound and cured stain barrier skim were
subjected to adhesion testing which necessitated the building of adhesion test pads
comprising 6 x 6-inch unreinforced layers of rubber, according to the following
procedure:
1. A 10 x 20-inch two-roll mill was utilized to prepare a number of 6 x 6-inch sheets
of stain barrier skim approximately 75 mils in thickness or thermoplastic white
sidewall approximately 25 mils in thickness for building rubber-to-rubber adhesion
test pads.
2. The 75 mil 6 x 6-inch sheets of unreinforced stain barrier skim were cured in a
. positive pressure mold for about 35 minutés at li9C~.
3. The 6 x 6-inch unreinforced sheets of cured stain barrier skim were wire brush
buffed using a 1.5-inch wide by ten-inch diameter wire brush wheel mounted on
a floor model electric buffing machine.
4. A 25 mil thick 6 x 6-inch sheet of unreinforced thermoplastic white sidewall was
applied to the buffed surface of the cured, unreinforced stain barrier skim. Thethermoplastic white sidewall - buffed, cured stain barrier skim combination was
covered with a layer of mylar film and placed in the cavity of a metal curing mold
- (cavity dimensions: 6 x 6 x 0.100-inch)
..
5. Adhesion pads consisting of 75 mils of a buffed, cured, unreinforced stain barrier
skim and a 25 mil layer of an unreinforced thermoplastic white sidewall was
9201013 FIR.P.US0068
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- 24 -
pressed for about six minutes in a 6 x 6 x 0.100-inch curing mold using very lowmolding pressure ( < 200 psi - press platens touching) and a curing temperature of
about 149C. The adhesion test pads were allowed to equilibrate for 24 hours
before testing.
S
6. Using a Clicker machine and~a one-inch wide metal die a number of six-inch long
by one-inch wide test specimens were prepared for peel adhesion testing.
7. Testing machine: Model 1130 Instron~ Universal Tester - a testing machine of
,~` 10 the constant rate-ofjaw separation type. The machine was equipped with suitable
grips capable of clamping the specimens firmly and without slippage throughout
the tests.
8. The one-inch wide specimens were tested at the rate (both crosshead and chartspeed) of two inches per minute using the adhesion test set forth in ASTM D-413
(machine method). Peel adhesion strength was determined at room temperatur,e
(i.e.; 230Cj as weli as occasionaliy at 38 and, 50C. ~est ,specim,ens were
allowed 15 minutes' to preheat prior to testing at elevated temperatures.
20 9. Adhesion strength is measured as: peel adhesion strength ~bs/inch) = pounds
force x sample width.
In Table VII the black sidewall of Table V, in both cured and uncured
forms, and a white sidewall formulation in Example 1 of Table VI were joined together
with and without a high density polyethylene liner. The thickness of the polyethylene
25 liner itself can be anywhere from 5 to 18 mils. Heat and pressure conditions were as
specified.
9201013 FIR.P.US0068
2~95~04
- 25 -
.c
~
~ r~
g ' ~ e a~
~4 ~ V
~ E E ;~
O ~ .e
e ~ ~ ~
- ~ m ~ *
<~n1n1~ T~TR P TT.Cn~;~
209a~04
- 26 -
In Table VIII peel adhesion properties obtained for Examples No. 1-6 have
been reported.
TABLE vm
SPeel Adhesion Between Black Sidewall and W~hite Sidç~all Compounds
Ex. No._ 1 2 3 4 5 6
Stock-to Stock Adhesion at 23C
lbs/inch 0.6 0.9 1.3 >38 ~35 >23
Type failure (A) (A) (A) (B) (B) (D)
10 Stock-to Stock Adhesion at 38C(a)
lbs/inch -- -- -- > 18 >33 > 11
Type failure -- -- -- (B) (B) (C)
Stoc_to Stock Adhesion at 50C(a)
lbs/inch -- -- -- > 4.5 > 25 > 4
15 Type failure -- -- -- (C) (D) (C)
,: , .. ':
(a) Specimens preheated for 15 minutes prior to testing
(A) = Separation occurred between the black sidewall/white sidewall compounds
20 (B) = Some tearing into the black sidewall compound. Chunks of black
sidewall adhered to the HDPE liner, white sidewall showed some
stretching and necking during testing
(C) = The white sidewall compound elongated and broke during initial peel
adhesion testing. Essentially no tearing resulted at the black
sidewalVwhite sidewall interface
(D) = The white sidewall compound experienced considerable stretching and
necking before separating at the black sidewalVwhite sidewall interface.
At the failed interface, a thin, black film of black sidewall compound
adhered to the white sidewall compound
9201013 FIR.P.US0068
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- 27 -
Next, in Table IX, 75 mil thick 6 x 6-inch slabs of cured stain barrier skim from
Table VI were wire brush buffed via machine and individually molded to the three white
sidewall compounds in Table IV using a curing mold for about six minutes using very
low molding pressure ( < 200 psi - press platens touching) and a temperature of about
5 149C. No polyethylene film liner was employed. Peel adhesion tests at temperatures
ranging from 23C to 50C were conducted and reported in Table IX.
TABLE ~
Peel Adhesion Between Stain Barrier Skim and White Sidewall Compounds
Example No. 1 2 3
Stock-to-Stock Adhesion at 23C
lbs./inch > 10.2> 15.6> 18.2
Type failure (E) (E) (E)
15 Stock-to-Stock Adhesion at 38C(a)
lbs./inch > 5.4> 8.3> 12.1
. Type failure (E) (E) ~E)
Stock-to-Stock Adhesion at 50C(a)
lbs./inch ~>3.8>5.7 >9.3
Type failure (E) (E) (E)
(a) Specimens preheated for 15 minutes prior to testing
(E) = The mineral-filled white sidewall compound experienced considerable
stretching and some necking before separating at the stain barrier
skim/white sidewall interface. At the failed interface, a thin, black film
of stain barrier skim adhered to the surface of the white sidewall
compound. Occasionally a small section of white sidewall compound was
observed on the surface of the stain barrier skim.
. 9201013 ~IR.P.US0068
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- 28 -
In conclusion, it should be clear from the foregoing examples and
specification that the use of mineral-filled white sidewall compounds comprising a blend
of semi-crystalline thermoplastic EPDM, EPR or other olefin-type polymers, with a
thermoplastic crystallinity enhancing polymeric additive, provides a white sidewall
5 composition that can be adhered to the surface of the black sidewall of a cured tire using
sufficient heat and some pressure and without the use of adhesives. Fully acceptable
peel adhesion involving white sidewall and either wire brush buffed passenger black
sidewall or stain barrier skim compounds resulted at test temperatures ranging from 23
to 50C without the use of a polyethylene liner. After peel adhesion testing small
10 sections (chunks) of white sidewall adhered to the surface of either the passenger black
sidewall or the stain barrier skim. Additionally, a thermoplastic film can be interposed
between the white sidewall and the black sidewall to improve adhesion further.
It is to be understood that the invention is not limited to the specific types
of therrnoplastic films or EPDM exemplified herein or by the disclosure of other typical
15 EPDM, EPR or other olefin type polymers provided herein, or by the disclosure of
crystalline enhancing polymers herein, the examples having been provided merely to
: demonstrate the practice of the subject invention. Those skilled in the art may readily
select other thermoplastic films, or other EPDM, EPR or other similar olefin polymers
including copolymers of ethylene and butene and ethylene and octene, according to the
20 disclosure made hereinabove. Similarly, the invention is not ne essarily limited to the
particular thermoplastic crystallinity enhancing polymeric additives, fillers and
processing materials exemplified or the amounts thereof. Finally, although the present
invention does not re~uire the use of solvents or adhesives between the white sidewall
composition and the black sidewall, the use of either should not be construed as a means
25 to avoid practice of the invention.
Thus, it is believed that any of the variables disclosed herein can readily be
determined and controlled without departing from the scope of the invention herein
disclosed and described. Moreover, the scope of the invention shall include all
modifications and variations that fall within the scope of the attached claims.
9201013 FIR.P.US0068
