Note: Descriptions are shown in the official language in which they were submitted.
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DEFLATED TIRE LUBRICANT
Background of the Invention
Field of the Invention
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This invention relates to lubricants for
pneumatic tires for vehicles and specifically to a
lubricant for a tire running while deflated or under-
inflated.
Description of the Prior Art
A basic problem with all pneumatic tires is
that they occasionally become underinflated or completely
deflated and when this occurs, the tire must be changed
and a spare tire put on. In some cases a blowout can
cause the vehicle to go out of control~
A tire which can be run flat has for some time
been a desirable objective in the tire-making art. If
a tire could be run flat for an appreciable distance,
the driver could run on the flat tire until a replace-
ment tire was obtained or the tire repaired. This
would eliminate changing tires on the road and depend-
ence on a spare. A driver could also run on thesuddenly deflated tire until a safe place to stop the
car is found, thus avoiding sudden stopping on crowded
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streets and highways.
There are many problems associated with running
a conventional tire flat. A flat tire is unstable,
making steering difficult. The lack of inflation
pressure causes the tire beads to unseat, and eventually
the tire may come off the wheel rim. In addition, rid-
ing with a flat tire can be an uncomfortable experience
since there is practically no cushion between the wheel
rim and the road surface.
A number of designs have been proposed to
increase the stability and rideability of the tire when
defla~ed or flat. Some of these proposals, such as
U. S. Patents Nos. 3,394,751 and 3,421,566 relate to
movable sidewalls so that the tire tread force is com-
municated directly to the rim. Other proposals, such
as U. S. Patents Nos. 2,04~,645; 3,392,722 and
3,610,308 have special units in the interior of the
tire.
A problem generated by tires run flat is the
friction which develops from the upper and lower portions
of the deflated sidewall rubbing against each other.
The friction produces excess heat and causes the side-
walls to wear excessivelyO To reduce this friction,
the inclusion of either liquid or solid lubricants on
the tire interiors has been proposed. U. S. Patent No.
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2,040,645, for instance, suggests a graphite lubricant, U.S. Patent No.
3,610,308 mentions the use of liquid silicone, and U.S. Patents Nos.
3,739,829 and 3,850,217 describe the use of polyalkylene glycols, glycerol,
propylene glycol, silicone and other lubricants. These lubricants, however,
are not believed to be as satisfactory as the preferred lubricant of the
present invention.
Summary of the Invention
-
The present invention provides a stable lubricant for a
pneumatic tire for use when the tire is operated in an uninflated or deflated
condition, said lubricant comprising:
a. 100 parts of a water/ethylene-glycol mixture wherein
there is at least one part of water for every 4 parts
of ethylene glycol;
b. from about 0.05 to about 2 parts by weight of a
polyethylene oxide of a molecular weight of about
500,000;
c. from about 0.15 to about 2 parts by weight of a
polysaccharide having a molecular weight of at
least about 10,000; and
d. up to 8 parts by weight of cellulose fibers, said
fibers having a length not more than 400 microns.
A lubricant of a viscosity such that the fibers will remain dispersed when
the tire is subjected to 200 g's at 70C.
The lubricant of the present invention is a solution of
polymer molecules, with the solution comprising water and ethylene glycol,
with the solute comprising small amounts of a polyethylene oxide and a poly-
saccharide as well as other materials, e.g. sodium nitrite, a corrosion
inhibitor and Triton N-101, Trade Mark for alkylaryl polyether alcohol (NPE
9 to 10), a wetting agent.
Brief Description of the Drawings
Figure 1 is a sectional view of a tire of the present
invention in its first embodiment.
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Description of the Preferred Embodiment
Referring to Figure 1, there is shown a pneumatic tire. The
tire has a thick tread portion 11 which extends circumferentially around the
tire, and sidewalls 12 which extend from the tread portion along the sides
of the tire. The tire is designed to be unted on a conventional wheel
rim 13 which has at its outer edges outwardly flared
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flanges 14 also of conventional design. Wire bead rings
15 are provided in the bead portion 16 of the tire where
- the sidewall meets the rim 13. In accordance with con-
ventional tire construction~ the beads are designed to
keep the tire on the rim when the tire is inflated. The
inflation pressure of the tire forces the beads 15
against the flange 14, keeping the tire on the rim and
maintaining tire inflation.
The tire shown in the drawing may be of the
conventional bias/belted or radial type. These tires
have two bias or radial plies 17 and 18 extending around
the interior of the tire. The plies extend from bead
to bead and are folded around the bead rings 15 so that
the ends 19 and 20 of the plies are located in the side-
wall region. There are also two steel or fabric belts21 and 22 extending circumferentially around the interior
of the tire and located directly interior to the tread
portion 11. Conventional rubber compositions are used
to form the tread and sidewall portions of the tire and
the air-retaining inner liner.
A feature of this particular tire is the circum-
ferential locking lug 24. The lug results from a speci-
ally designed increase in the thickness of the sidewall
at the end of the rim flange as shown. The locking lug
24 does not interfere with the normal characteristics of
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the tire when inflated. Upon deflation, however, the
locking lug 24 wraps around the flange 14 to secure the
tire to the rim 13. Thus, the deflated or flat tire is
secured to the rim allowing the tire to be driven flat
for a period of time.
The drawing ilLustrates a size BR78-13 SBR tube-
less tire mounted on a standard rim, and it will be
understood that a larger tire, such as size HR78-15
could have about the same shape. The rubber used in the
tire can be the same as used in conventional tires, in
which case the elastic rubber of the sidewall portions
could be an SBR rubber with a Shore A durometer hardness
in the range of 40 to 80. Butyl rubber can be used in
the inner liner to provide maximum resistance to gas
permeation.
It is preferable to provide a lubricant on the
interior surface of the sidewall portions at 47 to
reduce the friction and heat generated by the rubbing of
the upper and lower halves of the sidewalls when they are
in contact during operation of the deflated collapsed
tire. The viscous lubricant employed has excellent
lubricity, a viscosity which does not change appreciably
as the temperature is increased from 25C to 85C, and
stability when operated for long periods of time at high
radial accelerations such as 200 g's or higher~
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The lubricants preferred for use in the present
invention have excellent lubricity, are compatible with
the rubber of the inner liner of the tire, are stable
and operable over a wide range of temperatures and shear
rates, have a viscosity and composition such that the
ingredients remain uniformly distributed in service, and
have puncture-sealing capability.
Prior to this invention there were no lubricants
which met all of these requirements. The preferred
lubricant as disclosed hereinafter meets all of these
requirements.
The preferred lubricant of this invention com-
prises a high molecular weight polymeric material dis-
solved in a solvent, such as water, and having high
viscosity in the temperature range of 25C. to 90C.
The molecular weight of the polymer is at least 10,000
and preferably at least 50,000. A mixture of polymers
is preferably employed to provide a puncture-sealing
lubricant with a high viscosity at 25C. (such as 100,000
centipoises or more) which is not much higher (for example,
no more than 10 percent higher) than the viscosity at
85C. This can be accomplished by employing a small
amount, usually less than 2 percent by weight, of a water-
soluble gum or polysaccharide as described hereinafter~
The polysaccharide may have a molecular weight of 10~000
to 50,000 or more.
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The high polymer used with the polysaccharide pre-
ferab~y imparts good elastic properties to the solution
and is selected to provide good lubricity. Excellent
results are obtained using water-soluble high polymers
such as polyethylene oxides with a high molecular weight
of at least 10,000 and preferably 50,000 to 5,000,000,
such as "Polyox WSR 205", "Polyox W5R 301" and other
.
conventional polyethylene oxide polymers.
The water-soluble gums or polysaccharides are
employed because of their low viscosity-temperature coef-
ficient. Suitable polysaccharides for use in this inven-
tion are pentosans (C5H804)n, hexosans (C6H1005)n, gums,
mucilages, derivatives thereof, and the like and include
starches, methyl celluloses and other celluloses, hemi-
celluloses, modifications and derivatives thereof, andsimilar water-soluble high polymers. The molecular weight
can be 50,000 to 300,000 or higher. A large number of
different water-soluble gums or polysaccharides can be
used which are described in more detail in the textbook
"The Chemistry of Plant Gums and Mucilages" by F. Smith
and R. Montgomery, copyright 1959 by Reinhold Publishing
Corporation. Suitable water-soluble polysaccharide gums
and mucilages include Xanthan gum, gum arabic, many other
natural and synthetic gums and mucilages, derivatives
thereof and the like as described, for example, in said
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textbookO The monosaccharide building units of the gums,
mucilages and vegetable polymers may be of different types
and may/ of course, be modified in various ways without
destroying the usefulness of the polymers.
When the water-soluble polymers described above
are dissolved in waterJ they behave uniquely and tend to
assume voluminous configurations which lead *o a tremend-
ous increase in solution viscosity. It has been found
that when two polymers, such as polyethylene oxide and a
polysaccharide, are dissolved in a mixture of water and
ethylene glycol, an unexpected synergism is achie~ed and
a high-viscosity puncture-sealing lubricant is obtained
having excellent lubricity and the ability to function
well over a wide range of temperatures and shear rates.
The preferred lubricant of this invention may be
made by mixing at least 20 parts by weight of water with
not more than 80 parts by weight of ethylene glycol, about
0.05 to about 3 parts and preferably 0.05 to 1.5 parts by
weight of a very high molecular weight polyethylene oxide,
and about 0O05 to about 4 and preferably no more than 2
parts by weight of a high molecular weight polysaccharide.
The lubricant may also contain a very small amount of an
antioxidant and small amounts of other ingredients. It
preferably contains cellulose fibers or other suitable
filler in an amount such as 3 to 8 percent by weight and
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preferably 4 to 6 percent by weight. The fibrous filler
may comprise fibers with a length from 20 to 400 microns,
for example~
The preferred lubricant employs water and ethylene
glycol, about 0.05 to about 2 percent by weight of the
polyethylene oxide polymer, about 0.15 to about 2 percent
by weight of the polysaccharide, and about 4 to about 6
percent by weight of cellulose fibers. With respect to
the water-ethylene glycol mixtureJ the ma~or portion of
the mix should be ethylene glycol to minimize volatile
loss. Synergism is indicated, as shown by the examples
which follow, because the viscosity-temperature coeffi-
cient of the composite solutions is lower than the
individual polymer solutions containing the same amount
of fibers. In addition, the lubricant can be compounded
so that the viscosity is relatively insensitive to temp-
erature variation in the range of 25C. to 85C.
The polymers and ingredients of the lubricant are
selected to provide a viscosity (Brookfield) suitable for
the effect desired. For good lubricity the viscosity
should be at least 1,000 centipoises at 25C. Where
good puncture-sealing properties are also desired, the
viscosity may be 100,000 to 400,000 centipoises at 25C.
The viscosity may be such that the ingredients of the
lubricant remain uniformly distributed during service and
is preferably such t~ t they remain properly distributed
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when the lubricant is continuously subjected to 200 g'sat 700CL for 20 hours or more.
The total amount of the polysaccharide and the
water-soluble resin may be very small where the molecular
weight is very high and is usually no more than 5 percent
by weight~ However, more may be required to obtain the
desired viscosity if a lower molecular weight is employed.
For example, the amount of "Polyox WSR 205" with a mole-
cular weight of 600,000 may be 2 to 4 percent by weight
as compared to l percent or less of a similar polymer
having a molecular weight of l to 5 million.
A series of polymer solutions were prepared for
testing using formulations A, B, C and D indicated below:
Table I
.
_ Parts by Wei~ht
Ingredient A B C D
.
Ethylene glycol 50 50 50 50
Water 50 50 50 50
Polyethylene oxide -- 0.75 0.75 0~75
Polysacch~lde (KELZAN) 1.5 -- 0.95 1.5
Solka Floc SW 40 4.0 3O0 3~0 3.0
Solka Floc BW 200 2.0 l.5 l.5 l.5
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The viscosity of the polymer solutions was measured
at 25C~ and 88C. using a conventional Brookfield visco-
meter, model LVT with the following results:
Table II
. .
5 Viscosity (centipoises) A B C D
at 25C. 183,000 8,150 195,000 290,000
at 88C. 154,000 2,475 170,000 301,000
Percent chan~e -16% -69% -13% +3.8%
In the formulations A to D, the polyethylene oxide
was "Polyox WSR 301" made by Union Carbide and the poly-
saccharide was '~ELZAN" Xanthan gum made by Kelco
Corporation. Such polyethylene oxide has a molecular
weight of around 4 million.
Solka Floc is made by DiCalite Division of GREFC0
and comprises conventional cellulose fibers. SW 40 fibers
are about 100 microns long and about 16 microns thick.
8W 200 fibers are about 50 microns long and about 17
microns thick.
The wetting of the inner liner by the lubricant has
not been a problem~ However, it has been found that some
additives effect a significant decrease in the surface
tension of the lubricant and hence better wetting. Such
a material is Triton N 101, a nonyl phenoxy polyethoxy con-
taining 9 to 10 mols of ethylene oxide manufactured by
Rohm and Haas.
As shown in Table II, the polymer solution B con-
taining just polyethylene oxide exhibits a drastic
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reduction in viscosity upon heating while the polymer solu-
tions C and D containing a small fraction of the polysac-
charide are almost temperature insensitive.
The coefficient of friction of a typical vulcanized
radial-type inner liner compound sliding against itself was
measured first in the absence of a lubricant, then in the
presence of a silicone-graphite lubricant, and finally in
the presence of the above polymer solution lubricant C.
The results are shown below:
Table III _
Static Dynamic
Lubricant used Friction Friction
-Coefficient Coefficient
No lubricant 0.92 0.85
Silicone-graphite lubricant 0.20 0.12
Polymer solution lubricant 0.07 0.06
The results indicate that the polymer-solution lubri-
cant is about twice as effective as the silicone-graphite
and that it reduces the coefficient of friction by a decade
or a factor of 10.
In addition to favorably affecting the rheological
behavior of the lubricant, the addition of the cellulosic
fibers imparts puncture-sealing capability to the lubricant.
The lubricant can successfully seal a puncture in a subscale
tire resulting from a 6-penny nail. Leakage of air can
occur upon puncturing with larger size nails; however, the
puncture sites become covered with small amounts of the
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lubricant, and leakage is reduced.
The viscosity of the lubricant is essentially unaf-
fected by shearing when sheared at a rate of 30 sec~l for
2-1/2 hours.
The cellulose fibers remain suspended under the
influence of centrifugal force equivalent to a tire running
at about 50 mph (about 80 km/hr). After subjecting each of
the lubricants C and D to a large centrifugal force of about
220 g's at a temperature of 71C. for 24 hours, the lubricant
remained a uniform solution with the fibers still uniformly
dispersed~ Similar testing of the lubricant B without poly-
saccharide, on the other hand, resulted in a nonuniform
distribution of the fibers.
The lubricant does not swell the inner liner compound
of a typical radial tire. Samples of a radial tire inner
liner compound and urethane compound were immersed into a
lubricant solution for more than two weeks at 50Co Negli-
gible change in the samples' dimensions was observed.
Three size BR78-13 steel radial tires were coated
with the lubricant formulation set out below. About 454
(one pound) grams was used for each tireO These tires,
except for the sidewall which had a higher than usual
stiffness, were built to a commercial specification~ Two
similar tires were used as controls. The valve stems were
25 removed so that the tires would not hold air~ They were
mounted on 5" rims and run at a speed of 25 mph on a
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pulley wheel with an applied load of 784 lbs. (355~9 kg.),
Table IV below sets out the number of miles to failure in
run flat condition. It can be seen that the tires con-
taining the lubricant ran substantially more miles than
those without the lubricant.
Table IV
Tire Bead Lock Miles to Failure in -
No.LubricantMechanism Run-Flat Condition
1 No Rim well band 21
2 No Machine screws 19
3 YesMachine screws 43
4 YesMachine screws 42
Yes Rim well band 48 -~
The lubricant solution used in the above tires was
15 prepared using the formulation set out below:
In~redient
ethylene glycol 70 parts
water 30 parts
polyethylene oxide WSR 101 .05 parts
polyethylene oxide WSR 205 .03 parts
Kelzan 0.15 parts
Triton N-101 10.0 parts
Sodium metasilicate .075 parts
Sodium Nitrite .075 parts
Diethylene triamine .01 parts
Thiourea .01 parts
Total parts 110.4
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To further demonstrate the efficacy of the lubricant
of the present invention, a further series of tires size
BR78-13 Dual Steel II radial tires manufactured by
The General Tire & Rubber Company were coated with a
solution of the above lubricant of the invention~ In
each instance the tire was mounted on the right front of
a Vega automobile at the load specified in the table
below, The rim well band was made of rubber and it fit
snugly in the rim well, thus preventing the bead fr~om
unseating. In one instance as a control, a tire with no
lubricant was used. The valve was removed and the test
commenced without any tire warm-up periodO The endurance
mileage of each tire is shown in the table below:
Table V
Tire Load, Amount ofBead Locking Endurance
No.lbso Lubricant MechanismMileage
1 970 None Rim well band 25.3
2 970 1 lb. Machine screws 49.9
3 970 1 lbo Rim well band 70.9
4 970 1 lbo Machine screws 42.9
970 2 lbs. Machine screws 65~6
6 1080 1 lb~ Rim well band 22.7
7 1080 2 lbs. Rim well band 28.8
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The lubricant is serviceable over a broad temperature
range, from about -35Co to about 110Co This range can be
further extended easily by increasing the ethylene glycol
content of the lubricant at the expense of water with mini-
5 mum anticipated effects on the other propertiesO
As used herein and in the claims, the term "high
polymer" refers to polymers having a very high molecular
weight, such as 50,000 or more, and the term "watersoluble",
as applied to the gums, mucilages and other polymers,
indicates that the polymer is either dissolved or that it
swells to form a viscous solution.
Unless the context shows otherwise, "parts" means
parts by weight and all percentages are by weight.
The invention as shown herein is applied to a con-
lS ventional bias-belted or radial tire construction; however,
it is understood that the invention can be practiced with
other standard designs of tires. While the invention has
been shown and described with respect to specific embodi-
ments thereof, these are intended for the purpose of
illustration rather than limitation, and other modifica-
tions and variations will be apparent to those skilled in
the art all within the intended spirit and scope of the
inventionO ~ '
