Note: Descriptions are shown in the official language in which they were submitted.
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1~4~ 3
Pneumatic Tire Havin ~ ature
Technical Field
This invention relates to a puncture sealing
pneumatic tire. This invention particularly relates
to a pneumatic tire of the tubeless type having a
puncture sealant feature.
Background Art
Modifications to pneumatic tires have historically
been sought for retarding or preventing their deflation
upon being punctured. Many methods, sealants and tire
constructions have been suggested and offered for ordin-
ary passenger vehicle tires for automobiles which are
to be driven over open roadways. Fluid and semi-solid
puncture sealant coatings which seal by flowing into
the puncture hole have been unsuccessful primarily
because they tend to cause the tire to become out of
balance and also because many times they are not operable
or effective over a wide temperature range extending
from summer to winter conditions. Central cores of
cellular material which will physically maintain the
tire shape when punctured generally place a restriction
on the vehicular maximum speed because of eventual
breakdown or destruction of the cells by the effects of
heat and distortion.
Disclosure and Practice Of Invention
_
In accordance with this invention, a self-sealing
pneumatic tire is provided which comprises a tire casing
having a fitted, adherent sealant composite strip,
or sheet, on its inner surface comprised of an admixture
of (A) a partially crosslinked rubber selected from
at least~ bubyl and halobutyl rubber, (B) plasticizer
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843
for said partially crosslinked rubber, (C) butyl rubber-
compatible tackifier for said composite and (D) parti-
culate reinforcement for said composite.
In further accordance with this invention, a
puncture sealing pneumatic tire of the tubeless type
is provided having two spaced, essentially inextensible
beads, a crown portion generally having an outer ground
contacting tread, a pair of individual sidewalls
extending radially from the axial outer edges of said
crown portion to join the respective beads, a supporting
or reinforcing structure for said crown portion and
sidewalls, usually extending from bead to bead and
often referred to as a carcass, and said sealant composite
strip adhered to its inner surface. It is preferred
that the sealant composite sheet is positioned and
adhered circumferentially around the inside of the tire
on its inner surface on the area of its crown portion,
therefore, opposite the tread, although it can, if
desired, cover a major portion or entire inner surface of
the tire by extending essentially from bead-to-bead.
The sealing composite strip can be applied in a
unitary sheet form, as a multiple of individual strips or
as a relatively narrow individual strip spirally adhered
circumferentially around the inner surface of the crown
portion of the tire.
In additional accordance with this invention, a self-
sealing pneumatic tire is comprised of a cured rubber tire
casing having a fitted, adherent sealant composite strip
on its inner surface, said sealant strip comprised of
an admixture of (A) lO0 parts by weight of at least one
partially crosslinked butyl-type rubber selected from
halobutyl or butyl rubber, (B) about 25 to about 150 parts
by weight of at least one plasticizer for said rubber,
selected from at least one of paraffinic, naphthenic, or
aromatic oils, pine tar or liquid synthetic polymeric
plasticizer, (C) about 2 to about 50 parts by weight of a
tackifying resin for said rubber to enhance its tack
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li4~843
2A
selected from natural and synthetic tackifying resins for
rubber having a softening point in the range of 80C. to
120C., and (D) about 10 to about 150 parts by weight of
granular rubber reinforcement selected from at least one
of carbon black and inorganic rubber reinforcement agents;
where said butyl rubber has a molecular weight in the range
of about 100,000 to about 400,000 as the product of
polymerizing isobutylene with a minor amount of isoprene
and said halobutyl rubber is a chloro- or bromo-butyl
rubber, said butyl or halobutyl rubber partially crosslinked
to an extent characterized by being about 20 to about 80
percent soluble in a cyclohexane at 80C.; where said
tackifying resin is a rubber tackifier selected from at
least one of natural rosins and polyterpenes, synthetic
polyterpentenes, thermoplastic polyolefins, pentaerythritol,
esters of hydrogenated resins, thermoplastic hydrocarbon
resins and phenol-formaldehyde resins; and where said
granular reinforcement is of the particulate rubber
reinforcement type having a particle size in the range of
20 about 200 to about 400 sieve size selected from at least
one of carbon black and inorganic materials selected from
zinc oxide, titanium dioxide, aluminum hydrate, lithopone
whiting clays, hydrated silicas, calcium silicates, silica
aluminates, magnesium oxide and magnesium carbonate.
Thus, in further accordance with this invention, a
puncture sealing pneumatic tire of the tubeless type having
two spaced, essentially inextensible beads, a crown portion
generally having an outer ground contacting tread, a pair
of individual sidewalls extending radially from the axial
edges of said crown portion to join the respective beads,
a supporting and/or reinforcing structure for said crown
portion and sidewalls, generally extending from bead to
bead, and said sealant composite strip has a thickness in
the range of about 0.1 to about 0.3 inch and is applied
and adhered circumferentially around the inside of the tire
on its inner surface in its crown area as a relatively
narrow strip in a spiral fashion with sufficient revolu-
tions to achieve a desired width of the sealant composite.
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2B
The method of this invention comprises applying said
sealant composite in the form of a strip to the inner
surface of a cured rubber tire by the sequential steps of
(A) preparing the inner surface of the tire by (i) cleaning
5 with an aqueous detergent solution or hydrocarbon solvent
and allowing it to dry and/or (ii) abrading the surface to
roughen it, (B) optionally heating the tire to a tempera-
ture in the range of about 40C. to about 80C., (C) option-
al~y applying a thin coating of a cement to the prepared
inner tire surface and (D~ applying and adhering said
sheet, or strip, of sealant composite to the inner surface
of the tire or to the optional cement coat as a relatively
narrow strip in a spiral fashionwith sufficient revolutions
to achieve a desired width of the sealant composite.
As a desired feature of this invention, in said
sea~ant composite, said plasticizer (B) is selected from
at least one o~ an oil which is primarily parrafinic and a
semi-solid polyisobutylene having a molecular weight in
the range of about 1000 to about 2300.
The adherent, sealant composite on the inside surface
of the tire has a thickness in the range of about 0.1 (0.25)
to about 0.3 (0.76), preferably about 0.12 (0.3) to about
0.2 (0.5) inches (cm). Thus, a desirable thickness can be
in the range of about 0.12 (0.3) to about 0.25 (0.6) or
0.3 (0.76) inch (cm).
The sealant composite, adhered to the inside surface
of the tire is particularly valuable for sealing against
puncturing objects and for sealing holes left upon their
removal, over a wide range of temperatures, such as from
-40C. to 120C., preferably about -20C. to 100C., there-
fore, including the range of about -20C. to about 120C.
The sealant is also
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particularly valuable because of its resistance to
flow, or a relative resistance to change in its physical
state after being applied to the inner surface of the
tire. Thus, it exhibits an enhanced degree of dimensional
stability.
Uniquely, therefore, the sealant composite is
applied and adhered to the interior surface of a cured
pneumatic rubber tire of the tubeless type in strip
or sheet form having a dimen~ional stability and resis-
tance to flow as opposed to a fluid being spray coated,brushed or poured onto the interior surface of the tire.
Accordingly, the sealant composite sheet, or
adherent layer is provided as an admixture of (A) 100
parts of at least one partially crosslinked butyl-type
rubber selected from halobutyl or butyl rubber, (B~
about 25 to about 150 parts by weight of at least one
plasticizer for said rubber, selected from at least one
of paraffinic, naphthenic, or aromatic oils, pine tar or
liquid sy~thetic polymeric plasticizers, (C~ about 2 to
about 50 parts by weight of a tackifying resin for
said rubber to enhance its tack selected from natural
and synthetic tackifying resins for rubber having a
softening point in the range of 80C. to 120C., and
(D) about 10 to about 150 parts by weight of granular
rubber reinforcement seIected from at least one of
carbon black and inorganic rubber reinforcement agents.
The butyl rubber is of the type prepared by poly-
merizing a mixture of isobutylene and isoprene, with
the major portion being isobutylene and also by modi-
fying such a rubber with a halogen substitution.Typically, it is preferred that the halo substitution
is chlorine or bromine. The halo substitution can
generally be accomplished, for example, by halogenating
the butyl rubber. The butyl or halobutyl rubber is
partially crosslinked to an extent characterized by
about 10 to about 90 percent, preferably about 20 to
about 80 percent soluble in cyclohexane at about 80C.
This compares to about 2 percent soluble for a lesser
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crosslinked buty]. and only about 98 weight percent soluble
for a higher crosslinked butyl.
The butyl rubber typically has an average molecular
weight in excess of 100,000, preferably in the range
of 200,000 to 400,000 and even more preferably in the
range of about 300,000 to about 400, ooo . As already
pointed out, the butyl rubber is partially crosslinked.
The partially crosslinking of the butyl rubber is
intended to provide a composite which is not fully
cured so that it is not fully resilient and has some
capability of deforming under force or pressure, as
opposed to the more resilient, rubbery matrix of a
fully cured material. However, the partially cured
composite is intended to be distinguished from one
which has little or no cure at all so that it maintains
the required degree of dimensional stability.
In these regards, the crosslinking of the butyl
rubber can be accomplished by various means. Such
methods include outright curing with a sulfur or
20 qu~noid system. Purely peroxide cure systems are not
preferred because they generally provide too complete
or efficient of a cure. AlternatelyJ cure-promoting
agents can be included in the polymerizate which
enhances a crosslinking of the butyl upon or after
its recovery from the polymerization system. GEnerally,
such crosslinking methods and techniques are known to
those having skill in the art and it is considered
that the technology need not be repeated here.
Various rubber tackifying, thermoplastic resins
can be used in the practice of this invention to
enhance the composite's ability to seal around the
puncturing. Obviously, a primary purpose is to increase
the inherent tack of the composite of this invention.
~ccordingly, it is intended that such resins of the
type no~mally considered as rubber tackifiers, compatible
or easily mixed with the butyl rubbers. Representative
of such resins are thermoplastic polymers having a
soitening point according to ~STM No. E28-58T, in the
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114U843
range of about 80 to 120C. Such tackifiers may
include natural rosins and polyterpenes, synthetic
polyterpentenes, thermoplastic polyolefins, pentaeryth-
ritol, esters of hydrogenated resins, thermoplastic
hydrocarbon resins and phenol-formaldehyde resins.
Particularly useful resins are olefin/diolefin poly-
merizates with aluminum chloride and phenol-formaldehyde-
type resins.
The particulate reinforcement is in granular form
and is of the rubber reinforcement type. Typically, it
has a particular size in the range of about 200 to
about 400 U. S. Standard Sieve size. Representative
examples of various reinforcing agents are finely
divided, well-known rubber reinforcing agents such as
carbon black and inorganic materials, such as zinc
oxide, titanium dioxide, aluminum hydrate, lithopone
whiting clays, hydrated silicas, calcium silicates,
silica aluminates, magnesium oxide and magnesium
carbonate.
It i8 to be understood that other conventional
rubber compounding ingredients can be included in the
composite mixture such as antioxidants, antiozonants,
coloring pigments, stabilizers and accelerators.
The components of sealant composite can be dry
mixed by conventional means, such as by internal mixers,
mill mixing, calendering or extrusion to form a tacky
sheet or strip havin~ sufficient structural integrity
to have a resistance to flow.
The sealant composite can be conveniently applied
in its sheet form, such as in the nature o a strip, to
the inner surface of a cured rubber tire by the sequen-
tial steps of (A) optionally and preferably cleaning
or preparing the inner surface of the tire by (i)
cleaning with an aqueous detergent solution or hydro-
carbon solvent and allowing it to dry and/or (ii)buffing or abrading the surface to roughen it, (B~
optionally and preferably heating the tire to a tempera-
ture in the range of about 40C. to about 80C., (C)
` optionally, applying a thin coating of a cement to the
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ll~V843
prepared inner tire surface which can be conveniently
coated as a fluid by spraying, brushing or swabbing,
and (D) applying and adhering said sheet, or strip, of
sealant composite to the inner surface of the tire or
to the optional cement coat, if used.
It is to be appreciated that the sealant composite
can be applied circumferentially to the inner surface
of the tire in its crown area as a unitary sheet or as
a narrow strip applied in a spiral fashion with suf-
ficient revolutions to achieve a desired width of thecomposite.
The method or operation of the sealing effect
against a puncturing ob;ect or the sealing of the hole
in the tire is by mechanical means of the sheet composite
sealing around the puncturing object or sealing the
hole itself, relying on both the tack and plasticity of
the composite to stick to the nail or puncturing
object, and by flowing into the hole as the nail or
object is pulled through the sealant composite.
The tire of this invention can self-seal against
various puncturing objects depending somewhat upon the
tack, resiliency and thickness of the sealant composite
as well as the puncturing object. Typically, the tire
can self seal punctures caused by nails and objects of
various sizes. Representative of such nails are No. 4
to 6 nails and nails generally having a diameter up to
about 0.25 (0.63) inch (cm).
The vulcanized rubber tire itself can be of various
cured or vulcanized rubbers such as natural rubber and
synthetic rubber and their mixtures or blends. For
example, it can be rubbery butadiene-styrene copolymers,
butadiene-acrylonitrile copolymers, cis-1,4-polyisoprene,
polybutadiene, isoprene-butadiene copolymers, butyl
rubber, halogenated butyl rubber, such as chloro or
bromobutyl rubber, ethylene-propylene copolymers,
ethylene-propylene terpolymers (EPDM's~, elastomeric
copolyesters and polyurethane elastomers. Typically,
the various polymers are cured or vulcanized by normal
curing meehods and recipes.
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The invention can be further understood with respect
to the accompanying drawings wherein:
Fig. 1 is a side elevational view of a shaped,
molded and cured pneumatic tire with a cut-away portion
showing the circumferential application of an adherent,
cured, layer of ~he sealant composite of this invention
to its inner surface in its crown area opposite its
tread;
Fig. 2 is an enlarged cross-sectional view of the
tire of Fig. 1 at its tread portion illustrating the
unitary sheet of said sealant composite.
Fig. 3 is an enlarged cross-sectional view of
Fig. 1 at its crown and tread portion illustrating the
circumferential application of a sheet in the form of
a narrow strip of said sealant composite applied in a
spiral fashion in sufficient revolutions to achieve a
desired width of said composite.
More specifically, in the drawings, a tubeless
pneumatic rubber tire 1 is shown having the customary
tread portion 2, sidewalls 3 and support member 4,
which typically contains plies to back and reinforce
the tread and sidewall portions as well as an air
barrier layer 5, and particularly a solid, inner,
adherent sealant composite of this invention 6.
With further reference to the figures, the prac-
tice of this invention is more clearly dep~cted by
showing the application of the sealant composite 6
having sufficient dimensional stability to be applied
as a sheet or strip to the inner surface of the cured
tire in its crown area opposite its tread as opposed
to a fluid composite which would require a spray,
brush or swab application~
With further reference to the figures, particu-
larly Fig. 2, the practice of this invention i9 more
clearly depicted by showing the actual puncturing of
the pneumatic tire 1 with a nail 7 and the automatic
sealing of the tire by the sealant composite 6. The
. nail i8 then removed to leave the hole 9 in the tire
extending through ~he sealRot composite 6 The seRlRnt
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composite 6 acts to seal the hole 9 by being pulled
into the hole as the nail is removed.
The sealant composition is formulated to contain
certain specific constituents within narrow and defined
composition ranges. The difficulty lies in providing
a composition which has the ability to both re-heal
cuts in the sealant caused by a puncture and to seal
against a puncturing object or a puncture hole at
temperatures ranging from about -20F. to 130C. Once
the hole has been filled, which must occur very rapidly,
the sealant is to have sufficient strength and stability
to maintain air under pressures, generally at least
up to 24 and preferably up to 40 psig (pounds per
square înch-gauge) and sometimes even higher while the
tire is being flexed and stressed during normal vehicle
use. The sealant composite has been tested and found
effective under general conditions at temperatures up
to 130C., although automotive tires in normal usage
do not generally experience temperatures abovP about
60C.
The practice of this invention is further illus-
trated by reference to the following examples which are
intended to be representative rather than restrictive
of the scope of the invention. Unless otherwise indi-
cated, all parts and percentages are by weight.~XAMPLE I
A tubeless pneumatic rubber tire was prepared,
shaped and cured of the HR78-15 type having a ground
contacting tread, spaced beads, connecting sidewalls
and supporting carcass structure corresponding generally
to Fig. 1.
A strip, or sheet, of sticky sealant composite,
about 8 inches wide and Q.125 inch thick, was circum-
ferentially applied and adhered to the inside of the
tires in its crown area, opposite its tread, with a
cement in the manner generally shown in Fig. 3, although
a unitary sheet could have been applied as in Fig. 2.
A cement had previously been applied as coating
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~ having a thickness of about 0.003 inch to the inside
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of the tire.
The sealant was prepared by mixing the components
of the recipes shown in the following Table 1 and
calendering to ~orm a sheet.
Table 1
Component Parts
Butyl rubber, partially crosslinkedl100
10 Paraffinic oil, rubber plasticizer2 40
Phenol formaldehyde, rubber tackifying resin3 5
Polyisobutylene, rubber exte~der,
plasticizer and tackifier 50
Carbon black (HAF) 90
Zinc stearate 2
Obtained as Bucar Ex 262, a partially crosslinked
butyl rubber from the Columbian Carbon Co., described
as being crosslinked to the extent that it is 20
percent soluble in cyclohexane.
Obtained as Flexon 766, a petroleum oil described
as paraffinic from the Humble Oil and Refining Co.
30btained as SP-1068, a phenol formaldehyde resin from
the Schenectady Chemical Inc.
Obtained as Vistanex LMMS, a polyisobutylene from
The Enjay Chemical Co.
The cement used consisted of 90 percent of a
`rubber solvent as a blend of low molecular weight
paraffinic hydrocarbons and 10 percent of the recipe
according to the following Table 2:
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Table 2
Component Parts
Natural rubber 100
Rosin oil 5
Carbon black (HAF) 30
{~ Zinc Stearate 5
Phenol formaldehyde resin 30
Benzothiazole/guanidine 2.5
Sulfur 1.5
. Obtained as SP-1068, a resin from the Schenectady
Chemical Inc.
EgAMPLE II
A tubeless, pneumatic tire prepared according to
Example I having the adherent sealant sheet composite
applied as a spiral strip having a width of about 2
inches, adhered to its inner surface opposite its tread
portion with an overall sealant width of about 8 inches
was tested according to the following method along with
a control tire.
The tire was mounted on a rim, inflated and allowed
to rotate, under load, against a 67.5 inch diameter
motor-driven wheel. The tire was tested according to
procedure (AB-llOl) at a speed of 50 miles per hour
(mph) under a 1285 pound load with a hot inflation
temperature of 30 pounds per square inch (psi). Under
this test the tire was run for lOO miles or conditioning
purposes and then punctured with a 0.18 inch diameter
nail into and through a major tread groove. The tire
was then allowed to run under the prescribed speed and
load while its internal inflation pressure was periodically
measured.
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In these examples the sealant composite was provided
essentially as an admixture of (A) a partially crosslinked
butyl rubber, (B) a plasticizer for said rubber comprised
of both a paraffinic oil and a semi-solid polyisobutylene,
(C) a phenol formaldehyde rubber tackifying resin and
(D) carbon black as a particulate rubber reinforcement.
In the practice of this invention, with regard to
the polyisobutylene plasticizer, the polyisobutylene is
required to be a semi-solid at 40C., although generally
such a polymer can be described as a semi-solid over a
broad temperature range such as about 20C. to 40C.
This is to distinguish such a polymer from a relatively
hard, elastomeric polyisobutylene. In these regards,
such a semi-solid polyisobutylene generally has an
average molecular weight by osmometry in the range of
about 400 to about 25Q0 and preferably in the range of
about 1000 to about 2300. Its viscosity is generally
in the range of about 50 to about 4500 and preferably
in the range of about 400 to about 4300 centistokes at
210F.
While certain representative embodiments and
details have been shown for the purpose of illustrating
the invention, it will be apparent to those skilled in
this art that various changes and modifications may be
made therein without departing from the spirit or scope
of the invention.
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