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Patent 1100401 Summary

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Claims and Abstract availability

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(12) Patent: (11) CA 1100401
(21) Application Number: 1100401
(54) English Title: SEALANT LAMINATES
(54) French Title: TRADUCTION NON-DISPONIBLE
Status: Term Expired - Post Grant
Bibliographic Data
(51) International Patent Classification (IPC):
  • B60C 17/00 (2006.01)
  • C9D 5/34 (2006.01)
(72) Inventors :
  • BOHM, GEORG G. A. (United States of America)
  • ANDERSON, JOHN N. (United States of America)
(73) Owners :
  • FIRESTONE TIRE & RUBBER COMPANY (THE)
(71) Applicants :
  • FIRESTONE TIRE & RUBBER COMPANY (THE) (United States of America)
(74) Agent: ROBIC, ROBIC & ASSOCIES/ASSOCIATES
(74) Associate agent:
(45) Issued: 1981-05-05
(22) Filed Date: 1977-08-12
Availability of licence: N/A
Dedicated to the Public: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
716,493 (United States of America) 1976-08-20
737,884 (United States of America) 1976-11-02

Abstracts

English Abstract


ABSTRACT OF THE DISCLOSURE:
This disclosure relates to a sealant laminate to be
primarily used in pneumatic tires to seal punctures made by
external objects, such as nails. The laminate of the invention
comprises a puncture sealing layer and at least one other layer,
the puncture sealing layer containing a polymeric material that
has been at least partially degraded by exposure to irradiation
or to heat in the presence of a peroxide to yield its sealant
properties; the degraded polymeric material is selected from
the group consisting of polyisobutylene, copolymers containing
polyisobutylene and polyethylene oxide. The laminate may be
in sheet or strip form with various cross-sectional shapes.
The layers in the laminate comprise rubber compounds, some of
which may contain agents which either assist or retard cure by
irradiation so that the layers will have different physical
characteristics during the manufacture of end products containing
the laminate. The laminate may be cured by any known method,
either irradiation or thermal, after its assembly into the
final product.


Claims

Note: Claims are shown in the official language in which they were submitted.


The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A laminate comprising a puncture sealing layer
and at least one other layer, said puncture sealing layer
containing a polymeric material that has been at least partially
degraded by exposure to irradiation or to heat in the presence
of a peroxide to yield its sealant properties, said degraded
polymeric material being selected from the group consisting of
polyisobutylene, copolymers containing polyisobutylene and
polyethylene oxide.
2. The laminate of claim 1, wherein said degraded
polymeric material is polyisobutylene.
3. The laminate of claim 1, wherein said degraded
material has been degraded by exposure to irradiation.
4. The laminate of claim 1, wherein said polymeric
material has been degraded by a heat treatment in the presence
of a peroxide.
5. The laminate of claim 4, wherein said peroxide
is 2,5-bis (t-butylperoxy) 2,5 dimethylhexane.
6. The laminate of claim 1, wherein said puncture
sealing layer also contains a polymeric material that has
cross-linked on exposure to the degradation treatment.
7. The laminate of claim 6, wherein said cross-
linked polymeric material is selected from the group consisting
of natural rubber, copolymers of butadiene and styrene, and
halogenated butyl rubber.
32

8. A laminate comprising at least three layers
having two outer layers and a puncture sealing layer forming
an inner layer, said inner, sealant layer containing a polymeric
material that has been degraded by exposure to irradiation to
yield its sealant properties, with said two outer layers
relatively unaffected by said irradiation, said degraded polymeric
material being selected from the group consisting of polyiso-
butylene, copolymers containing polyisobutylene and polyethylene
oxide.
9. The laminate of claim 8, wherein said degraded
polymeric material is polyisobutylene.
10. The laminate of claim 8, wherein the outer
layers contain sulfur and sulfur cure accelerators so that
said outer layers will vulcanize when exposed to a subsequent
heat treatment.
11. The laminate of claim 8, wherein at least one of
said layers varies in thickness across its cross-section so
that said laminate is contoured to provide more of said
variable layer in certain, predefined areas along its width.
12. The laminate of claim 8, wherein said inner,
sealant layer also contains a polymeric material that has cross-
linked on exposure to irradiation so that said inner layer has
a degraded polymeric material trapped within a cross-linked
polymeric material.
13. The laminate of claim 12, wherein said cross-
linked polymeric material is selected from the group consisting
of natural rubber, copolymers of butadiene and styrene, and
halogenated butyl rubber.
33

14. In the method of manufacturing a laminate
comprising a puncture sealing layer and at least one other
layer, the steps comprising providing a layer with a polymeric
material which at least partially degrades on exposure to
irradiation or to heat to form a material having sealant
properties, the degradable layer containing a peroxide when
the degradation is to be effected by the application of heat,
said degradable polymeric material being selected from the group
consisting of polyisobutylene, copolymers containing polyiso-
butylene and polyethylene oxide, assembling said degradable layer
with said at least one other layer to form said laminate and
exposing said laminate to irradiation or to heat whereby said
degradable polymeric material degrades to form said puncture
sealing layer.
15. The method of claim 14, wherein said degradable
layer contains a peroxide and said degradation is effected by
the application of heat.
16. The method of claim 14, wherein said degradation
is effected by the application of irradiation.
17. The method of claim 16, wherein said at least
one other layer contains a sensitizing agent which promotes
cross-linkage therein when said irradiation is applied.
18. The method of claim 14, wherein said laminate
contains three layers with said degradable layer forming the
middle layer, the outer two layers at least partially cross-
linking when exposed to the degradation treatment.
19. The method of claim 14, wherein said degradable
layer also contains a polymeric material that will cross-link
on exposure to the degradation treatment.
34

20. In the method of manufacturing a laminate
containing at least five layers in which one of said layers
contains a puncture sealant material, the steps comprising
providing at least two outer layers with a desensitizing
agent which retards cross-linkage when subjected to irradiation,
providing two inner layers with a sensitizing agent which
promotes cross-linkage when subjected to irradiation, providing
a middle layer located between said sensitized layers with a
polymeric material which degrades on exposure to irradiation
to form said puncture sealant material, said degradable poly-
meric material being selected from the group consisting of
polyisobutylene, copolymers containing isobutylene and poly-
ethylene oxide, assembling said laminate with said middle layer
located between the two sensitized layers and one of said
desensitized layers located outside of each of said sensitized
layers, and subjecting said laminate to irradiation so that
said layers are differentially cross-linked with said sensitized
layers being cross-linked to a greater degree than said
desensitized layer and said middle layer being degraded to yield
a puncture sealing layer.
21. The method of claim 20, wherein said sensitizing
agent is selected from the group consisting of paradichloro-
benzene and the thioetherpolythiols.
22. The method of claim 20, wherein said
desensitizing agent is selected from the group consisting
of 2,6-di-t-butyl-p-cresol; phenyl beta-naphthylamine;
4,4' thiobis (6-t-butyl-m-cresol); N-(1,3-dimethylbutyl)-N'
phenyl-p-phenylene diamine; syn-di-betanaphthyl-p-phenylene
diamine; aromatic oils, sulfur and sulfur cure accelerators.

23. A vulcanizable pneumatic tire comprising as one
of its rubber components a laminate comprising a puncture
sealing layer and at least one other layer, said puncture
sealing layer containing a polymeric material that has been at
least partially degraded by exposure to irradiation or to heat in
the presence of a peroxide to yield its sealant properties, said
degraded polymeric material being selected from the group
consisting of polyisobutylene, copolymers containing poly-
isobutylene and polyethylene oxide.
24. A vulcanizable pneumatic tire comprising as
one of its rubber components a laminate comprising at least
three layers having two outer layers and a puncture sealing
layer forming an inner layer, the outer layers having a higher
degree of cross-linkage than the inner, sealant layer, said
sealant layer comprising a blend of an irradiation degraded
polymeric material with puncture sealing properties and an
irradiation cross-linked polymeric material, said degraded
polymeric material being selected from the group consisting
of polyisobutylene, copolymers containing polyisobutylene and
polyethylene oxide.
25. A vulcanizable pneumatic tire having an
innerliner comprising a laminate of a puncture sealing layer
and at least one other layer, said puncture sealing layer
comprising a blend of an irradiation degraded polymeric
material with puncture sealing properties and an irradiation
cross-linked polymeric material, said degraded polymeric
material selected from the group consisting of polyisobutylene,
copolymers containing polyisobutylene, and polyethylene oxide,
and said cross-linked polymeric material selected from the group
consisting of natural rubber, copolymers of butadiene and
styrene, and halogenated butyl rubber, said polymeric materials
36

being present in a ratio between 75% degraded-25% cross-linked
to 25% degraded-75% cross-linked.
26. A vulcanizable pneumatic tire having an
innerliner comprising a laminate of at least two layers in which
an outer layer has a higher degree of cross-linkage than an
inner, sealant layer, said sealant layer comprising a blend of
an irradiation degraded polymeric material with puncture
sealing properties and an irradiation cross-linked polymeric
material, said degraded polymeric material selected from the
group consisting of polyisobutylene, copolymers containing poly-
isobutylene, and polyethylene oxide, and said cross-linked
polymeric material selected from the group consisting of natural
rubber, copolymers of butadiene and styrene, and halogenated
butyl rubber, said polymeric materials being present in a ratio
between 75% degraded-25% cross-linked to 25% degraded-75% cross-
linked.
27. A pneumatic tire comprising as one of its rubber
components a laminate comprising at least five layers in which
one of said layers contains a puncture sealant material, said
tire manufactured by the steps comprising providing at least two
outer layers with a desensitizing agent which retards cross-
linkage when subjected to irradiation, providing two
inner layers with a sensitizing agent which promotes
cross-linkage when-subjected to irradiation, providing a middle
layer located between said sensitized layers with a polymeric
material which degrades when exposed to irradiation to form
said puncture sealant material, said degradable polymeric
material being selected from the group consisting of poly-
isobutylene, copolymers containing isobutylene and polyethylene
oxide, assembling said laminate with said middle layer located
between the two sensitized layers and one of said desensitized
37

layers located outside of each of said sensitized layers,
subjecting said laminate to irradiation so that said layers are
differentially cross-linked with said sensitized layers being
cross-linked to a greater degree than said desensitized layers
and said middle layer being degraded to yield a puncture sealing
layer, assembling said laminate into said tire and vulcanizing
said tire.
28. A pneumatic tire comprising an annular, road-
engaging tread surface, two sidewalls each connecting a side of
said tread surface to an annular bead, reinforcing body plies
extending from one bead to the other through the sidewalls and
tread and a laminated innerliner member located radially inwar-
dly of said reinforcing body plies, said laminated innerliner
comprising at least two layers in which one of said layers
contains a puncture sealant material, said tire manufactured
by the steps comprising providing a first layer of said lamina-
ted innerliner with a polymeric material that cross-links on
exposure to irradiation, providing a second layer of said
laminated innerliner with a polymeric material that at least
partially degrades on exposure to irradiation to form said punc-
ture sealant material, said degradable polymeric material being
selected from the group consisting of polyisobutylene, copolymers
containing isobutylene and polyethylene oxide, assembling said
layers into said laminate, subjecting said laminate to irradiation
whereby said second layer degrades to yield a puncture sealant
layer, assembling said laminate into said tire with said sealant
layer located between said first layer and said reinforcing
body plies, and vulcanizing said tire.
38

29, The tire of claim 28, wherein said degraded
polymeric material is polyisobutylene.
30, The tire of claim 28, wherein said sealant
layer comprises a blend of said irradiation degraded polymeric
material and another irradiation cross-linked polymeric
material.
31. The tire of claim 30, wherein said cross-linked
polymeric material is selected from the group consisting of
natural rubber, copolymers of butadiene and styrene and
halogenated butyl rubber.
32. The tire of claim 31, wherein said degraded
and cross-linked polymeric materials are present in a ratio
between 75% degraded - 25% cross-linked to 25 degraded-75%
cross-linked.
39

Description

Note: Descriptions are shown in the official language in which they were submitted.


This invention relates to a laminate composite sheet
or strip of rubber compound which is made up o~ several
separa-te layers of specifically designed rubber compound. The
laminate may be made by any of the known methocls, such as
calendering and the like; however, it is preferred that the
laminate be formed by a process known as coextrusion in which
two or more rubber compounds passed through the preform die
to ~orm separate layers which are joined in the final die. A
recent technique for this is disclosed in U.S. Patents
3,479,425 and 3,557,265. This coextrusion process has been
applied to plas-tics and thermal plastic elastomers -to form
laminates -thereof.
This inven-tion :is speciEicall,y reLatecl to a laminate
t:hat conta:ins a sealant layer, wherein the :La,yer corlta:ins a
mater:ia.l. that ifi at least partially deyraded when exposed to
irradiation or hea-t in -the presence oE a peroxide. In
addition, the sealant layer may also contain a material that is
partially cured by these same treatments.
In this invention the term "degrade" is used to
characterize a chain scission type reac-tion in the polymer
phase. The term "cure" is used to characterize a cross-linkage
typc reaction in the pol,ymer phase.
- 2 - ~,
.

~o~
The use of layers of sealant material in pneumatic tires
to seal punctures is well known in the art' for example,
see U.S. Patents 3,048,509; 3,62~,585 and 2,877,819. These
teachings disclose a laminate in which the sealant layer is
encased in one or more cover layers to retain the flowable,
soft, sealant layer in its proper location during the service
life of the -tire. Use of a sealant layer without these cover
layers is also disclosed. The laminates taught by these
references comprise a sealant layer of unvulcanized rubber and
cover layers of rubbers that are vulcanized during the tire
curing operation. The sealant layer is devoid of materials
which would cause vulcaniza-tion.
Additionally, other laminated articles are known in which
the separate layers comprise materials which have different
properties. Such articles have been utilized in the manufacture
of tires wherein a stiff, partia:L:Iy cured rubber compound has
beQn sandwiched betweerl tw~ layers of soft, tacky, uncured
ru~ber compouncl by caLerldering the soft :Layers onto t~e a:Lr~ady
partially cured co~npound. Sl;rips oE this type 'have beon elnpLoyed
in the bead area of the tire, where the tire contacts the rim,
as an abrasion gum strip, to resist the chafing -that takes place
between the tire and the rim.
In all laminates, an uncured rubber compound tends to flow
during the curing operation, thereby decreasing its effective
gauge or thickness. In the above described type of composite
strip the partial precure of the stiff compound enables it to
retain its gauge or thickness during the -tire curing operation,
but the precure renders the strip inheren-tly dry, causing an
~d~lesion pro'blem between it and the other parts of the -tire
during the building and curing operation. The ex-ternal layers
of the soft, -tacky, uncured rubber compound in the laminate
help to overcome this deficiency and provide the necessary
uncured adhesion so that the composi-te strip will not separate
from the remaining pieces of the tire prior to its final cure.
However, there is still an adhesion problem because layers
(-the external layers) are being adhered to a partially cured
layer.
Additionally, all of these prior composite strips have
been difficult and expensive to manufacture. The process has
been to calender the inr.er, stiff strip, subject it to a curing
-3-
';~

4C~
operation in which it is partially cured, and then calender
the soft, tacky strips on both sides of the then stiff strip
to form the final composite laminate. With the sealant type
laminates, the soft, uncured layer is calendered onto the
soft cover layersO These operations have ~een e~pensive and
time consuming in the past and involve several stepsO Due to
the limitations of the calendering operation, it has also
necessitated the use of thicker strips for an adequate safety
margin than are necessary to perform the functions in t~.e
final produc:t.
The product of -this invention has greatly simplified and
improved the composite strip -technology thereby enabling the
use of multilayer composite strips in pneumatic tires as the
air impervious liner which covers the inner periphery of the
tire. ~
" /
,
.. _ . .. . . . . .. .
_~_
;~',

4~
In prior sealant laminates where ths material is a
fluid or semi-fluid great difficulty has been encountered in
¦ ~he marlu.facturing operation- l'he fluid or semi-fluid nature
1 of ~he material result;s in inherent processing dif~iculties
5 ¦ in trying to obtain thi.s ~aterial i~ a workable form and retain
. I it in this forrn until th~ final product is finished. ~e .
present inventiorl eliminates these drawbacks. In the present .
i~vention the material is in a solid, workable form durin~
. ¦ the initial manufacture; that is, the construction of the
¦ lamirlat;~~ In the radi.ati.on cure system the material retains
¦ its soli.d cha~act~r until the i.~radiatiorl ~tep ~/here :it attain~
¦ i~, flu:icl or ';C~ rltl:kl Char~lCt¢X~ `li.S CIOe; not oc~ur urltil .
¦ af~er the lami.~ate ha.s bee~n con~;t;ruct;ecl ancl the~ flui.d laye
¦ is surroundeà by solid m~terial 1;hat remaills solid. In ths
15 ¦ peroxide ~ystem the mate~ial retains i.ts solid condition ~til
the final curing operation in the marluflcture of the product,
such ~s the pne~atic tlre.
.he techIlolog~ and in~entiorl of thi~ applica-tion. are
not limi.ted to thi.s place lrl a p~eumati.c,t.ire. ~he technolo~y
m~y be ap~lied to ~ny of ~ver~l end prodllct~, su~h as conveyo~
~elt.~, containers and in~ust~ial product,sO .
~ he product of the inve~tion is paxticularly useful whs-~ e
it is necessary to have one material retain a certain thick~ess
iu the end product. This has usually been accomplished in the
past by using an excess a~oun-t of material -to insure ths mini~ a
is present in the final product after it has thinned out in
the processing s-teps. Ths prior partial pre-cure method,
although a help, stlll nad this defici.ency because only a ~
partial cure could be obtained; a full cure w~uld hav~ rendered
~0 the cure~ _tock unusable due to its poor a~hesi.on~
. r~ - .
I , ''.

~ :
This invention provides an improved laminate by
~;e~lectively altering some of the layers in the lamir.ate so . ~ .
that thS3 layers will either be uneffec1,ed 1 paxtially cur~d,
lully cured, partiall~ d~raded or ful~y de~raded wherl subjected ..
to irxadiation or heat in the presenc e of a peroxl~e D
- This technique eliminates at least one of the steps
necessa~- iIl the prior processes, In th~s technique, the
cumposil,e strip i.s obtairle(l by calendering or, preferably~
by coes:trv;sionD l~1e rubber co~pou.nds i.n the va:cious layers
lO ~ay be ~,electively either se~sitizecl or deseIIsitiz.ecl to react
t;o ir~aclia-~;ion in variou.s. cle~:r~e~D Th~ c,ompc)s:it~ ~ltrip is
th~ ject~:d 1:;o irrad1.at;io~ rh~Ie~ l;h~: ~.;clns:~.'JiY.~cl :I.a~e~
ox~ e~ 3 I~r~ i.all y c u~ed. c~r fUIly cux~d and. l;h~ d~se~ izcd
lrly~r o c layers are uI1crfecte(l. t)n~ of t:hc~ layers also conl;ains
a materi.al that ~,ril] dee;rade on exposure to irradiati.on or a ~ .
blelld of a degcadable material a.~d a cross linkable materlal~ The
~egradation and cross~lin~cage may cllso be obtained by heating
in the presence Or a peroxide~ This xesull;s in the differ~rlt; . .
].ay~rs in the c or~ osite h~vin~; di.î1`ererlt physical
c,llalr~ct:~r;.stlcs which may be uti liY~ed i.n l;h~: u].ti.~nate m~nufact;ur:? . .
Or the ~ld ~)roduct.
. It i~; an ob~eot oî this iIIvent;ion to prc)vi(l.e a 1 a~ ate
which can be rr1e~nufactuIed in a relati-vely ch~ap and
uncomplicat,ed manner~ . . .
2S ~t is a fu~t;hcr object of this in~ention to provide a
l~minclte i.~ ~.hich the thi.clcness of th2 separate~ laye~s is
. dictated by the amount of the layer necessary ~o perform its
. function and not by the prob]ems inherent in the manufactur~
of the la~inate~
. . , '.
. .' I

It is a further object of this invention to provide a
sealant laminate in which one layer contains a material that
will at least partially degrade when exposed to irradiation
or heat in the presence of a peroxide.
In its broadest aspec-t, the present invention provides
a laminate comprising a puncture sealing layer and at least
one other layer, the puncture sealing layer containing a
polymeric material that has been at least partially degraded
by exposure to irradiation or to heat in the presence of a
peroxide to yield its sealant properties; the degraded polymeric
material is selected from the group consisting of polyisobutylene,
copolymers containing polyisobutylene and polyethylene oxide.
The invention relates to the technology of obtaining
a composite laminate of several layers of material and the
res~ltillg laminate. It is known that rubber compounds may be
sensitized to cure or partially cure when subjected to
irradiation. Also, it is known certain materials wlll degrade
when exposed to irradiation or heat in the presence of a
~peroxide. The inven-tion's utilization of these concepts is
novel in that it may yield laminates with layers having
sensitizing materials,
-- 7 --
l B~ ' '

I4~ :`~
layer avin~; desens it izin~; materiAls, ~nd layers hav ~ng de~ra~d~
mate~:ials. This results in ~he laminate ha~tins cure~l laye.rs,
relat:ively uneured laycrs and de~;Iaded layers after it has
been subject~d to irradiationv Thi.s tech:llique enables the
producti3n of composite laminates ir~ which predc'c~rlllined 12.;ers
have predetermi.ned physioal charac,t~istics ~hich are clesirable
in the manuîactvr~ oî the ul'cima1;e end prod.uctO
For ~xample, the i~lexlinc~r in a pneumatic tir~ muC t
b~ ufl ici.~l~.tly iL~pervi.ous to aix l;cJ pre~c~nt the air in t~le
inf]aJGion charnber from ~.ntering inko th~ t;.ire. I* the air do~s
eJ~ter ix~l;o thc t;i.rc, i.-l; ~!i.ll c~p~md dllo l;o the hea-t ~renerated
clu~:i.n~!; op~rnt; i.c~n arld ~ nt;~ l,y c:a~l~3e ~ pa.x~ltioll in t;h~
~ h~ r~ , a:i.x~ r~ vi.~ t~ r ~3xalr,~)~.0, ~ . .
halo~lcnal;~d b~ yl rubbora, do ~o t ~)0~;5eS~ ~oocl builcllI16 tac k
15 1 c~ld aclhesi.on, are soft, ~nd will t;hi.n out in the hi~ll press~lre - .
areas when the tire is expanded &nd v~llcani7..ed in the
I Vu ~L c E3~ g ~) I O C, e S S . , ,
¦ . It :i~ nec essa~y that the innf?rl.ine~7 be sufîi.c,ient;ly
I air iJnpervious and retc~ i ts (limen~;iona]. s I;~bility so that i.t
2C) ¦ wil]. rlol; 1,11i.n olll; in the.se hi~h pI~s~ re ale~.s c)f t~le t:ire
y:icl~ ; a~ s~l.r.r;.~.iont l,~Iickne.s.c; to ~îfe~cl;ively ~it;o}? I;h.
nir passa~r~ t~hrol~hout the enti.le inn~l~ pe~iphery OI the tire
~;o that the mi.nimum l;hickness is mail)taiIled. in the high press~xe
areas (the tre-ld shoulders) of the tixe. ~his invent:ion may - f
25 . eliminate the necessity for provicling a thick innerliner acro,ss
; the entire periphel~jr o~ the tire by proIile extrusion~ ~hen
~ this echnique is uti~lized, it is possj.ble to exh~ude e ¦
. . , ' ' ' . ,~
. ' ' ~ ' . ,~, : "
. ' . ,J'` ;
. ,. , ~",

contoured innerliner in which the thickness is increased in
the high pressure areas o-E the tire without an increase in the
thickness in t~le low pressure areas. This results in a
significant savings of rnaterial as the minimum amount of
material necessary may be utilized across the en-tire periphery
of the innerliner.
This invention also enables the manufacture of an innerliner
in which inner layers of the laminate may be designed to give
certain characteristics to t'he overall laminate and the outer
layers may be designed to give building adhesion so that
separations will not occur prior to -the vulcanization of the
tire. This is accomplished by having one of the inner layers
comprised of a halogenated butyl compound which will give
the necessary air impermeability, another inner layer comprised
of a polybutadiene rubber compound which provides the stiffness
on exposure to irradiation so that it will maintain its
dimensional integrity during the~ vulcanizatio~ operation, and
an outer layer on both sides comprised Oe a nat:ura:l rubber
cornpound having suEEicient tac'k ko adhexe to t'he contiguous
components of the tire and to i~sele in th0 spLice area of thQ
innerliner~ The two inner layers may be sensitized to cross~
link or cure on exposure to irradiation whereas the outer
layers are desensitized so tha-t such irradiation treatment does
not effect any tacky characteristics. This composite strip can
be manufa~ured at much lower gauges than the prior art strips
due to this technique, thereby saving a considerable amount of
raw materials and costs.
The innerliner laminate also contains a layer of material
which will have sealant properties in the end product. The
la~er with sealant properties will be in a condition that
permits easy processing during the manufacture of the laminate
and until it is subjec-ted to the treatment which will degrade
one of the materials in the laminate. This degradation results
in a softening of the sealant material to a soft or semi-fluid
orfluid composition. In this degradaiion process a relatively '
high molecular weight material is degraded (chaln scission) to a
lower molecular weight material which is moreE~ . 'rhe
degradable material will act as, and process as, a high
molecular weight material until the degradation s-tep.
This degradation is obtained either by irradiation or by
heat in the presence of a peroxide. One such rnaterial which
_g_
~, ' '
. .

~ ;aQ~
will degrade upon exposure to irradiation or upon ~he
application of heat in the presence o a peroxide is poly-
isobutylene tPIB) and its copolymers. Another such material
is a polyethylene oxide. These materials are mixed with -
carbon black and oil to achieve desired end properties~ Such
a rubber compound will be degraded upon exposure to irradiation. '
Alternatively, a peroxide may be added to this compound so
that the compound will degrade-on exposure to heat and the
irradiation step eliminated.
The sealant layer may contain a blend of one of the
degradable materials mentioned above and a cross-linkable
material along with carbon blaclc and oil. The cross-linkable
rnaterial may be any Oe the dioleE:Lrl elastomeric types, either
copolymers or homopol~ners. The ratio o the degradable
material to the cross-:lin]cable material in -the b:lend is
within the range of 25% degradable-75% crosa linkable to
75% degradable-25% cross-linkable. Such blends may be
heterogeneous or non-miscible having a continuous phaGe and
a discontinuous phaseO ~he blend may also be a co-continuous
mixture of the degradable and cross-linkable materials when
appropriate mixing techniques are used.
If a heterogeneous blend i9 Eormed, the degradable
material is contained in the discontinuous phase, as the
dispersed phase, and the cross-lin]cable material for the
continuous phase, as the matrix phase. It has also been
found that the levels of carbon black and oil are important
to processability.
rrhe physical character of the sealant layer may range
from a fluid to a semi~fluid or a solid type consistencyO rrhis
fluid nature is directly proportional to the amount of
degradable material (low molecular weight material) present
--10--
~ 1~?~

in the layer; that is, as the amoun-t of low molecular weight
material increases, the sealant layer becomes more fluid or
more soft. When the sealant layer contains no high molecular
weight material, i-ts final consistency, after irradiation or
heat in the presence of a peroxide is -fluid or very soft in
nature. When higher levels of the cross-linkable material
(high molecular weight) are present, the final consistency
of the sealant layer is solid in nature.
In the ratios disclosed above adhesion problems may
occur between the sealant layer and o-ther layers. This type
of problem is more predominant when the sealant l~yer contains
higher levels oE the degradable material.
rrhe invention is not limite~ to a spccific cnd use but
may be ~mployc~ in other ~nd products, such as, l:in~rs for
tanks and containers Oe all types, hoses and fabric reinforce-
ment for the manufacture of tanks. It is envisioned that
composite laminates may be manufactured with layers of
different materials dependiny upon the properties desired and
the end use.
~ny of the standard, rubber curing peroxides may be
utiliz~d in the peroxide system used to obtain the degradable
material~ ~xamples of such peroxides are dicumyl peroxide
and Varox powder which is a blend of inert filler with 50%
of 2, 5-bis (t-bu-tylperoxy) 2,5 dimethylhexane.
Several chemicals have been found usefal to accelerate,
in varyin~ degrees, the cure of rubbercompounds by irradiation
and several chemicals have been found useful to inhibit the
cure of rubber compounds by irradiation. These promoters and
retarders are classified as sensitiæing or desensitizing agents.
The type of rubber utilized in the compound is critical and
dictates the type of promoter or retarder that will function.
--11--

4~
The type of promoter or retarder will vary when different type~
of rubbers are used in the compound and the amount of the~e
chemicals may vary depending upon the type of rubber used or
the dosage (amount) of irradiation which the rlubber compound
receives~
Specifically, it has been determined that paradichloro-
benzene ~PDCB) is an effective for irradiation cure in rubber
compounds. It has also been determined that certain of the
thiotherpolythiols are effective promoters. The specific
polythiols which have been evaluated and found useful are set
out in Table I. Compound 2 identified in this table was
utilized in the examples which follow and is designed "TEPT"
therein.
TABLE I
POLYTHIOETHER POLYT~IIOLS DERIVED FRO~
.. , .. ..., . .. ~
TRIEN~ DITHIOL OR TRIENE-H2S POLY_ADDITIONS
COMPOUND THIOL FUNCT. IDEALIZED CHEMICAL
SH. E~UIV.~GM STRUCTURE_AND DER VATION
0050 ,r--rl-r~S ~CH2 ) 3S~ from
cyclodocetriene and 1,3
0
propane dithiol.
2 .0082 , S~CH2CH2 r I
~ ~(C~l2cH2s}i)272
from trivinyl cyclohe~ane
and H2S.
3 .0045 S/CH2CH2
( CH2 C~2 S ( C~2 ) '
SH)~/2 from trivinyl
cyclohexane and ethanol
dithiol.
4 .00~ r-/CH2CH2~S(CH2)~Sl~3f rom
trivinyl cyclohexane and
1,4 butane dithiol.
12-
,

COMPOUMD THIOL FUNCT. IDEALIZED CHEMICAL
SH. EQUIV./~M STRUCrURE AND DERIVATION
_
S ~ H2)2 ~ ((CH232
(CH2) 3SH 272from trivinyl
cyclohexane and 1,3 propane
dithiol.
It has also been determined that effective retarders of
irradiation curing or cross~linking include aromatic oils,
sulfur, sulfur cure accelerators and some rubber antioxidants
and/or antiozonants of the substituted diphenylamine type,
such as N (1, 3-dimethylbutyl)N'-phenyl-p-phenylene diamine,~
Table II lists some commercial antioxidants/antiozonants
which h~ve been found useful as retarders o~ irradiation cure~
A higher swelling ratlo indicates more retarding ~ffect. ~he
swelling ra-tio were ob-tained by compounding one part of the
particular antioxidant into 100 parts of polybutadiene rubber,
subjecting the compound to S Megarads of irradiation, immersing
the sample in toluene for 48 hours at room temperature and
measuring the weight of the swollen rubber against the weight
~ of the dry rubber.
T~BLE II
TEST ANTIOXIDANT CHEMICAL COMPOSITION _ SWELLING
RATIO :
1 None --- 11.5 .
2 DBPC 2,6-di-t-butyl-para
cresol 15.1
3 Santowhite* 4,4'thiobist6-T-butyl-m-
Crystals cresol) 13.6
4 PBNA phenyl beta-naphtylamine 14.7
Agerite White* syn-di-betanaphthyl-p- 1:1.9
phenylene diamine - :
*trademark
-13-
. .
:

- 1~0~4~
TEST ANTIOXIDANT CHEMICAL CO~lIPOSITION SWELLING
RATIO
6 Santoflex* 13 N-(1,3 dimethylbutyl)-N' 27.4
phenyl-p-phenylene diarnine
The dosage of irradiaticn which is utilized to accompiish
this invention and the conditions under wh;ch the dosage is
applied are dependent upon ~everal variables, the type of
rubber in the rubber compound, the promoter or retarder -
utilized in the rubber compound, the level of the promoter
or retarder utilized in the rubber compound, the thickness of
the layer of material, the thickness of adjacent layers of
materials, the sequence of the layers of material, the number
oE the layers oE material and whether the irradiation is
app:Lied to one or both sicles of the colTIpo~ite str:ip. The
proper combination is obtained to yield the desired physical
properties in the laminate.
The dosage also may be controlled by conditions under
which the dosage is applied, such as the amount of energy
of the electron beam employed. This may be controlled so that
the electrons do not completely penetrate the entire strip. This
results in the irradiation of part of the strip, but not the
entire stri~. . .
DET~II,ED DESCRIPTION OF TIIE INVE:NTION
Figures 1 and 2 are partial cross-section views of this
invention as embodied in a sealant containing innerliner
for tires.
Figure 3 is a partial cross-section view of this
inven~ion as embodied in a contoured, sealant containing
innerliner for tires.
Figure 4 is a partial cross-sectional view of another
embodiment of this inven-tion which is used for a self-sealing
innerliner for tiresO
*trademark
~ ` :

4~
Figure 5 is a cross-sectional view of a tire embodying
this invention as an innerlinerO
Figure 6 is a cross-sectional view of a tire embodying
this invention wherein the sealant layer is only located in
the crown of the tire.
In Figure 1 the laminate is shown generically as 10
havin~ internal layer, 12, and two external layers, 11. The
internal layer contains a material which will de~rade when
subjec-ted to irradiation or heat in the presence oE a peroxide,
or a blend of the degradable material and one that cross-links
when subjected to irradiation or heat in -the presence of a
peroxide. The outer layers, 11, are designed to be relatively
uneEEected by irradiation~ ~ley may comprise a rubber compound
~es:Lgned to hav~ air L~lpermeability properties or a rubber
compound designed to have good building tac]~. An exa~ple of
the latter t~pe is a rubber cornpound comprising 100 parts of
natural rubber, 4S parts of carbon black and other compounding
ingredients, including the following which retard irradiation
cross-links, Santoflex 13, Aromatic Oil, Sulfur and Sulfur
Cure Accelerators.
When the irradiation s~stem is used, the laminate, 10,
after its construction, is subjected to an irradiation treatment
which will degrade the degradable material in layer 12, whether
this material be blended with one that cross-links or not, will
cross-link the cross-linkable material in layer 12, if any is
present; and will have little effect on layers 11. The laminate
is then placed in the final product and the subsequent processing
steps accomplished to yield the final produc-t, including the
vulcanization thereof which cures layers 11 and does not
degrade layer 12.
When the peroxide s~stem is used, a peroxide compound is
mixed into the internal layer. After the laminate is constructed
-15-

it is placed in the final product and the product is cured.
This curin~ process wîll degrade the degradable material in
layer 12 whether -this material be blended with one that cross-
links or not; will cross-link the cross-linkable material in
layer 12, if any is present; and will cure layers 11.
In the application of this invention, the laminate, 10,
may be obtained by calendering or coextrusion. The coextrusion
method is preferred as it provides better control of the
-thickness of the layers at lower gauges, gives better adhesion
between the layers and permits the formation of laminates
having contours at preselected positions, such as those sh~wn
in Figure 3.
~ lalninate of the construct:ion shown in I'igure 1 was
as~mbl~d wherein the degradable, sealant layer, 12, comprised
a compound having the following :ingredients:
Parts per 100 Polymer
Solution styrene/butadiene polymer 25
Polyisobutylene 75
Carbon black 60
oil
I'his compound was calendered into a sheet 8 inches wide and
.082 inches thick. A standard, halogenat~d butyl rubber
containing innerliner compound was used for layers 11. Strips
of this compound were calendered and faced on each side of the
sealant layer. These external layers were .014 inches thick,
making the total laminate .110 inches thick This laminate
was irradiated by two passes with a single side surface dose
of 8.5 Megarads(MRADS). This resulted in a radiation dose of
10.8 MRADS on the back side of the laminate. A portion of this
laminate was cured in a laboratory press and subjected to the
laboratory puncture sealank tes-t described below. This laminate
yielded good air reten-tion results on this tes-t:.
-16-

This cured laminate was placed in a laboratory apparatus
to determine its sealing properties. The laminate was first
covered with a backing layer of fabric coated with cured skim
stock to provide support for the laminate during the test.
In this apparatus a strip of the laminate covers a chamber ;-
which is supplied with an internal pressure by an air cylinder.
The chamber is equipped with a gauge to measure the pressure
in the chamber. The pressure is regulated by a valve between
the cylinder and the chamber. The apparatus is so constructed
that a nail may be driven into the laminate and then removed~
Upon removal of the nail from the laminate, the pressure retained
in the chamber is determined. The coverage of -the nail with
the s~alan~ mat~ria:l is also evaluated.
In thls test on the cur~d laminate descrlbed a~ove, a 16
penny nail was repeatedly driven into and then pulled out of
the laminate. The nail had a uniform coating of the sealant
material after it had been pulled out. ~o significant air
loss occurred in the chamber even after repeated nail punctures.
Tires have been manufactured and tested containing the
laminate described above. Production tires were built
containing this laminate by the following techni~ue. During
the production o~ a standard E78-l~ size tire having two
polyester cord body plies and two glass cord belt plies the
sealant laminate was applied to thé building drum. The splice
in this strip was covered with a layer of the body ply compound.
The remainder of the tire was built and vulcanized using
standard methods and e~uipment~ This resulted in a tire in
which the crown area had an 8 inch wide s-trip of the sealant
laminate, similar to the construction shown in Figure 6.
This tire was tested according to a test specified by the
General Motors Corpora-tion for tires with puncture sealan-t
.""~
, .. ..

capabilities. Under this test procedure the tire is mounted
and inflated on its recommended rim. The tire is then run
2 hours at 50 miles an hour using its rated load and inflation
on a laboratory tire testing wheel After this break-in
period, one of the center grooves of the tire is punctured `
with a 20 penny nail. The nail is removed, the tire air
pLessure is checked, and the hole is checked ~or air leakage
by the application of a soap solution with any bubbles in the
solution indicating air leakage. In the test on this tire no
leakage was detected. Tbe tire is then run for 1,000 miles
on the test wheel, again at 50 miles an hour and rated load.
At the end of this 1,000 miles, the tire is again checked for
leakage with the soap solution and the inElation pressure is
again checked. In this test no leakage was detected and th0
in~lation pressure was the same as the initial inflation
pressure.
At this time, a shoulder groove is punctured with the
20 penny nail and the nail is removed. The leakage and pressure
checks are repeated and the tire is run a second 1,000 miles.
At the end of the second 1,000 miles the leakage check procedure
is repeated and the inElation is checked. Again, with this tire
no lea]cage was dictated and no loss of inflation pressure was
indic&~ed.
At this time, a third puncture is made in~the tire with
the 20 penny nail in a groove intermediate between the center
groove and the shoulder groove~ The leakage and pressure tests
are again performed on this third hole and the tirc is then run
another 1,000 miles. After this third 1,000 miles the -tire is
removed and the test is completed.
In the test performed on this tire, the tire was run
965 miles making a total mileage of 2,965. No leakage was
found at any o~ the puncture holes a-t the end of the test and
-18-
;:'~. ' .

4~
the inflation pressure was .5 psi less than the initial inflation
pressure. It is believed that this pressure loss was due to
the technique of measuring the pressure and not to any air
loss through any of -the punctures.
To demonstrate the feasibility of the feature of the
differential properties in the laminate layers in this invention,
laminated were manufac-tured having a layer of soft, natural
rubber compound comprising 100 parts of natural rubber, 45 parts
of carbon black and other compounding ingredients, such as
Santoflex 13, aromatic oil, sulfur and sulfur cure accelerators,
all of which have a desensitizing effect on irradiation cure,
and a layer of a hard, rubber compound comprising 100 parts of
a soLution styrene/butadiene copoLymcr, ~0 parts o~ reitl~orcing
c~rbon black and ~our parts of PDC~, a sensitl~ing ,Igent. In
thi3 laminate the ~oft, natural rubber cornpound had a thickness
of ~045 inches (.1143 cm) and the hard, solu-tion styrene/
butadiene compound had a thickness of .035 inches (.0889 cm).
These layers were separated by two Layers of Mylar and a blue
cellophane dosimetry layer to measure the irradiation dosage
used. Two identical pairs o-f laminate samples were initially
subjected to irrad:iation on one side and were turned over and
subjected to irradiation on the other side; a double side
irradiation. ~fter this irradiation step the laminates were
disassembled. The layers of one of each pairs of such strips
were ch~cked for physical properties (stress-strain data).
These results are set out in Table III under the column
"Radiation Cure". The separated layers of the remaining
irradiated strips were~ given an additional thermal cure for
10 minutes at 328 degrees F. in a .040 gauge mold and their
physical properties were then ob~ained. These resul-ts are
reported in Table III under the column "Radiation and Thermal
Cure". Three separate -tests were run in this manner, each a-t
a di~erent dosage as shown in Table III.
--19--
; ' . .

4~
TABLE III
TEST RADIATION CURE RADIATION AND
THERMAL CURE
Rubber Desensitized Sensitized Desensitized Sensi-
Compou~d Natural Rubber Stereon Naturaltized
Rubber _Stereon
TE~T 1
Ave. Dosage
8.6 Megarads
Tensile Strength
(psi) 590 228S 2860 2490
Modulus (psi) at
100% elongatiorl ~5 570 285 670
200% elongat:ion 75 :L290 800 1815
300% elongation 150 2240 1590
Elongation at
Break (%) 560 300 445 260
Tl~:ST 2
':
Ave. Dosage
11 Meqarads
Ten~ile Strength
(pBi ) 840 2620 28951695
Modulus ~psi) at
100% elongation 50 605 260 530 :
200% elongation 90 1495 700 1200
300% elonga-tion 190 2515 1435
Elongation at
Brcak (%) 630 315 ~60 260
TEST 3
Ave. Dosage :~.
12.3 Megarads
Tensile Streng-th
(psi3 855 2440 25~5 2050
-20-
: :~

Rubber Desensitized Sensitized Desensitized Sensi
Compound Natural Rubber StereonNatural tized
Rubber _ Stereon
Modulus (psi) at
100% elongation 55 705 220 610
200% elongation 100 1745 690 1425
300% elongation 205 - 1295
Elongation a-t
Break ~%) 595 265 455 265
This data clearly demonstrates the feasibility of this
invention showing khat the sensitized layer is cure~ by the
irradiation step, the desensit:Lzed :layer is not, the desensitized
l~yer i~ cured by the ~ub~equ~nt vulcanizatlon step and the
sensitized layer is not adversely a~fected by the subsequent
vulcanization step.
In Figure 2 the sealant laminate is shown generally as
20 havin~ two layers, 21 and 22O Layer 21 is the layer
containing the degradable sealant type ma-terial. Layer 22 is
the external layer which is used to cover the sealant material
so that it wi~l remain in its proper position in the end
product. Layer 22 may be the standard tire innerliner compound
or it may be a standard tire skim stock as previously described
in this specification. Figure 5, which will be discussed later,
demonstrates the utilization of the laminate of Figure 2 as a
sealant layer in a pneumatic tire.
If a sealant material which will be de~raded upon exposure
to irradiation is used, the procedure for Figure 1 will be
3U followed. Alternatively, the peroxide system described in
relation to Figure 1 may be used. As explained in relation to
Figure 1, in this sys-tem the irradiation step is not ut.ilized.
-21-
~, .

Upon the application of heat, such as in the tîre vulcanization
s-tep, the peroxide degrades the degradable material and cross-
links the cross-linkable material.
qhis peroxide system may be utili~:ed with a rubber compound
containing 100% of degradable material (PIB) or blends of the
degradable material with a cross-linkable diolefin. When
blends are utilized, the split masterbatch technique of mixing
is preferred to insure that the peroxide does not prei~erentially
cross-link the cross-linkable material wi-th a small amount of
degradation in the degradable material.
In the split masterbatch technique, separate masterbatches - `
are made containing l()0 parts o~ the degradable or cross-lin}cahle
rnateri~l with 60 parts carbon b:Lack and 40 parts oil. These
sepaxat~ mast~rbatches ma~ t,hen be bLended in any desired
proportions to obtain any ratio Oe degradable materLa:L to
cross-Linkable material thak may be desired. The peroxide is
added during this blending operation. By this technique the
Applicants have made sealant layers with varying levels of the
degradable material and have subjected these layers to the
laboratory puncture sealant tes-t described above. r~le results
Oe these determinations are disc Losed. Table IV along with a
compound containing 100% Oe the degradable mat~rial.
TABLE IV
PIB (Degradable) 100 75 50 25 75 50 25
Solution SBR
(cross-linkable) - 25 50 75 25 50 75
Carbon black 60 60 60 60 60 60 60
oi 1 ~o ~o a~o ~o ~o ~o ~o
Peroxide 2 2 2 2
Seal good good good bad good good bad
This data demonstrates the feasibility Oe -the peroxide
system to obtain a ma-terial with puncture sealant properties.
-22
.. ~ .

Li4~
It is understood that the levels of oil, carbon black ~nd
peroxide, as we~l as the ratio of the degradable material to the
cross-linkable material, are within the discretion of the
persons skilled in the art and depend upon the speci~ic nature
of each ingredient used and the overall manufacturing system to
which the compound is subjected. '
Figure 3 represents another embodiment of the innerliner
laminate o~ this invention. This figure demons-trates the
contoured embodil~ent . In Figure 3 ext~rnal layers, 3:L, are
comprised of a soft rubber compound designed to have good
building tack and, when the irradiation system is used, these
layers may be desensitized against curing by, Eor examp:le, t'he
inclusion of an antiox:Ldant such as Santoflex ~3. Inte:rnal
.~ay~rs 3~ and 33 are showrl as 'being thic]cer irl certain
p~edetermined areas. 'I~lis excessive thickness rnay be pre'located
in an area of the end product (in this case a pneumatic tire)
where the laminate is subjected to the highest pressure in its
shaping and curing operation. This extra thickness provides
additional material in the high pressure areas which yields an
end product with an adequate thickness of the mater.ial in the
high pressure areas without having the ex-tra thickness in lower
p.ressure areasO 'I'his erabo~irnent resu:lts in a savincJs of
material.
In a pneuraatic tire innerliner application of -the
contoured shape, the thicker areas of the lamin~te are located
in the area of the tire that is subjected to the highest pressure
in the shaping and curing operations or the greatest expansion
in these opera-tions. The extra thickness in high expansion
areas prevents innerliner thinning out and cord shadowing (body
cords actually striking through the thinned-out innerliner) that
may occur in this area of the tire. By this Application, the
con-toured strip provides the necessary thickness in the trouble-
-23-

~LQC~4~
some areas without having to retain that thickness across the
complete width oE the strip as in prior laminates~
In Figure 3 layer 32 may be a hard rubber layer which is
sensitized to cure when subjected to irradiation. This layer
may be comprised of a solution polybutadiene rubber and reinforcing
carbon black. As such, this layer is utilized to retain the
thickness of the laminate during the subsequent shaping and
curing operations. Alternatively, this layer may be a hard
rubber layer comprised of a halog~nated bu-tyl rubber and
reinforcing carbon black. As such, this layer is the barrier
layer w~lich resists the passage o~ air from the internal air
chamber of the tire into the tire.
The layer, 33, in Figure 3 ls the puncture sealant layer.
tk ma~ be compr:ised o~ any o~ th~ sca:Lant mater:lals that are
disclosed in thi~ sp~ciE~cation. ~t rnay conl;ain a peroxide for
the peroxide degradation system previously described or it may
not and be used in the irradiation system previously described.
~ t is understood that additional layers may be included
in any of the lamina'es disclosed in this specification or that
any combination of the layers disclosed in this specification
may be contained in one laminate. For example, a laminate may
contain two external layers o~ soEt rubber compound designed to
have good building tack, and an internal sealant layer designed
to seal when punctured and containing a ma1erial that is
degraded upon exposure to irradiation or upon exposure to heat
in the presen~e of a peroxide, another internal layer containing
a halogenated butyl compound designed to provide a barrier
against the passage of air and yet another in-ternal layer of a
hard rubber compound designed to cross-link when exposed to
irradiation to provide a layer which will maintain the integrity
of -the laminate during subse~uent processing steps.
Fi~ure ~ represents another embodiment of an innerliner
-2~-

laminate. In Figure 4 the laminate is designated generically
as 40. It contains two ou-ter layers, 41, comprising a soft
rubber compound which is designed to have good building tack
and is desensitized against irradiation curing by, ~or exampler
the inclusion of an antioxidant such as Santoflex 13. Two
intermediate layers, 42 and 43, are located inside OI layers
41. These layers comprise a hard rubber compound ~ontaining
halogenated butyl rubber and reinforcing carbon black which
have been sensitized to cure on exposure to irradiation, ror
exarnple, by the inclusion o~ TEPT. Between layers 42 and 43 is
a layer of polyisobutylene, 44, without any sensitizing or
desensitizing agen~s~ This material may or may not contain
solne r~inforcing material, such as carbon black~ Bridges 45
and ~6 o~ the salne material uti:Lized :in layers ~ and 43 conneck
layers 42 and 43 to one another. These bridges form pockets
which contain the layer 44.
When the laminate of Figure 4 is subjected to irradiation,
the layers 41 will be unaffected and will remain soft and tacky
to provide adhesion during the subsequent processing steps for
the end product. The layers 42 and 43 wilL partially or fully
cure t~e~eby providing a stiff, hard foundation for the
composite lamin,3te. r~he material in layer ~4 wilL be degraded
by chain scission and will form a liquid, pasty material. This
laminate can -then be applied as the innerliner of a tire and
subjected to the later vulcanization step. The resulting tire
will have an innerliner wllich contains pocKets of the liquid
polyisobutylene ma-terial. '~liS material will ac-t as a sealant
to any punctures which may occur in the tire thercby giving
the tire a self-sealing capability. The bridges 45 and 46 are
necessary to maintain the integrity of the colnposite laminate
arter the irradia-tion step due to the fact that the layer 44
is liquified by the irradia-tion step.
-25-

~10~
The laminate of Figure 4 is feasi~le because irradiation
causes chain scission in the polyisobutylene while the cross-
linking which occurs will not balance the degradation due to
this chain scission reaction in this material. Standard butyl
rubber, a copolymer of polyisobutylene and isoprene, is degraded
to a certain degree by irradiation but this degradation is
partially compensated by a concurrent cross-linking reaction.
The same two compensating reactions occur in halogenated butyl
rubbers except the cross-linking reaction is more predominant
in the halogenated butyl than it is in the standard butyl. This
performance of the butyl rubbers demonstrates the critical nature
of the irradia-tion treatment and the criticali-ty of selecting
the propor sonsitizing or desensitizing acJents for ~ach specific
rubber.
It ls envisioned that this chain-scission versus cross-
linking situations may also be employed in a three layer laminate
in which the two outer layers are soft, tacky rubber compounds
desensitized to resist irradiation cure and the inner layer
contains a blend of polymers, such as polyisobutylene and
halogenated butyl rubber. Upon irradiation the poly:isobutylene
will degrade and form a liquid which will be trapped in the
cross-linked halogenated butyl rubber. Th:is composite would
have self-sealing ~haracteristics.
Figure 5 represents a tire containing this invention. The
tire is shown generically as 50 having tread 51, sidewalls, 52,
and beads, 53. The placement of the innerliner of this invention
on the inner periphery of the tire is shown as strip 54. ~he
other featureof -the tire may be any of the known constructions
(radial, bias, belted-bias) for passenger, truck, airplane
off-the-road, tractor or industrial tires.
Figure 6 represents a tire containing a sealant layer as
described in Figure 2. The basic components of the tire in
-26-
.~
.

~0~4~
Figure 6 are identical to the components in Figure 5.
Additionally, Figure 6 depicts the laminate, 20, of Figure 2,
with sealant layer 21 and cover layer, 22, in the crown area
o-F the tire. This is the area where nail punctures predominantly
occur, It is understood that layer, 22, of laminate, 20, may
contain air-resistant properties such as those provided by
halogenated butyl innerliner compounds.
Table V demonstrates the sensitizing and desensitizing
characteristics of severa:l. chemicals on a rubber compound
of the followin~ basic formula:
Solution styrene/butadiene copolymer (SBR) - 100 parts
Reinforcing furnace black ~CB) - 50 parts
Each comparison is llsted under a test number, the first
c~lumn d~f in~s tl~ g~di~nts .in th~ above basic :Eormula, the
second colurnn the modulus at different elongations and the
last the average irradiation dosage to which each compound was
exposed. In the tests the two compounds were laminated
together and irradiated, the compounds were then separated and
the physical properties of each determined.
TABLE V
'rest 1 Modulus at Elongation Dosage
100% 200% 300% Ave. Meqarads
SBR/CB 187 - - 7.3
SBR~CB + 3.5 TEPT* 1004 - - 7.2
Test 2
SBR/CB ~ 3.5 TEPT 889 - - 7.6 :
SBR/CB ~ 3.5 Santo-
flex 13 127 - - 7.2
Test 3
, - . ~ .
SBR/CB 219 325 _ 6.9
SBR/CB ~ 1.5 TEPT,
2 PDCB** 632 1824 - 7.1
:
-27~
., , . - - . . -

~o~
Test 4 Modulus at Elongation Dosage
100% 200% 300% _ Ave. Meqarads
SBR/CB + 3.5 Santo-
flex 13 178 213 - 6.9
SBR/CB + 1.5 TEPT,
2 PDCB 623 1706 - 6.9
Test 5
-
SBR/CB + 1.5 TEPT,
2 PDCB, 30 naphthenic
oil*** 235 683 1447 8.3
SBR/CB + 3.5 Santo-
flex 13, 30 aromatic
o:il**** 48 57 6~ 8.0
~r~ 6
SBR/CB + l.S TEPT,
2 PDCB, 20
naphthenic oil 315 1090 - 10.1
SBR/CB + 3.5 Santo-
flex 13,
20 aromatic oil 68 85 _ 10.1
Te t 7
SBR/CB -~ 1.5 TEPT, ...
2 PDCB,
10 naphthenic oil4051165 2267 7.8 '
SBR/CB + 3.5 Santo-
flex 13
10 aromatic oil 88 110 145 7.6
'l'~st 8
SBR/CB + 1.5 TEPT,
2 PDCB, 20
naphthenic oil 325 1033 - 9.6
-28-

~A
3L~ILQ(~4~1
Modulus at Elongation Dosage
100% 200%300O/oAve. Meqarads
SBR/CB ~ 3.5 Santo-
flex 13 -
20 aromatic oil 55 55 - 3O5
Test 9
SBR/CB + 20
Naphthenic oil 141 302 702 9.9
SBRfCB + 20
Aromatic oil 75 10~ 143 10.0
Test 10
SBR/CB + 3.5 TEPT293 963 1793 8.3
SBR/CB + 3.5
,Santoflex 13, 20
Aromatic oil 57 72 92 ~.2
*TEPT= Thioetherpolythiol (compound 2 in Table I)
**PDCB= p-dichlorobenzene
***naphthenic oil= Sunthene 4240
****aromatic o11= Dutrex 72~
This data demonstrates the selective cure of the rubber
compound in a laminate when the rubber compounds have been
s~nsit.ized or desensitized to react to the irrad.iation
treatment. A11 of the tests were subje~cted -to the double side
irradiation treatment except Test 6 which was irradiated on
only one side, the side having -the higher dosage.
Table VI demonstrates the application of this invention in -
a composi-te strip wherein the inner layer is cured by irradiation
arld thc two outcr layers aro uncffcct(?~. T}leso laminates werc
prepared with three layers each containing a solution styrene/
bu-tadiene copolymer, as indicated in Table V. Mylar film was
placed between each layer to facilitate later separation. The
laminates were subjec-ted to d double side irradia-tion trea-tment;
-29-
:!
,

~ .
the layers were then separated dnd tne physical properties
determined for each layer.
Table VI
Laminate A Gauge Dosage Modulus at Tensile Elonga-
(inches3 ~Megarads) 300% Elong- Strength tion(%)
ation ~psi) (pSi)
A. 100 SBR/70CB
40 aromatic
oil/2 San-to-
flex 13.021 3.8 41 51 800
B. 100 SBR/50CB/
2 PDCB .030 3.5 258 822 733
C. 100 SBR/50CBj
2 Santoflex .33 3.75 :L~3 303 992
~3
Lamina-te B `
-
A. 100 SBR/70CB/
2 Santoflex
13, 40 aro-
matic oil .023 5.7 67 107 840
B. 100 SBR/50CB/
2 PDCB .034 5.4 383 1.391 713
C. 10~ SBI~/50CB/
2 Santoflex 13
.035 6 196 628 860
This data demonstrates the irradiation cure of the . .
sensitized inner layer of a three layer lamina-te while the
desensitized outer layers are une~fecte~d by the~ irradiation
treatment. The outer layers re-tain their building tack while
the inner layer is hardened and will retain its dimensionO
The dosage received by the layers in the above examples
was measured by the use o~ strips of blue cellophane containing
-30-

methylene blue dye. These strips were applied to the top and
bottom of the laminates to be irradiated. Op-tical density
measurements were taken on the strips before and after
irradiation. The irradiation reduce~ the dye to a colorless
state with the amount of bleaching being proportional to the
irradiation dose received by the strip.
The dose on the strip is determined from a plot of the
change in op-tical density (before and after irradiation) as
a function of dose size. The average dosage on a layer is
calculated from the surface dose and a previously determined
depth-dose distribution curve for the particular electron
accelerator being used. ~ uniform dosage throughout each
layer is obtained by a proper se:lectlorl oE the amount oE
~lectrorl energy an~ the double~ si~e dosage tec~hnique.
This invention takes max:imum advantage of the lamlnate
theory that the greater the number of interfaces, the greater
the resistance to flow of the laminate. This invention
makes possible lamina-tes containing more layers and thinner
layers -than previously obtained. The in-terfaces more evenly
dis-tribute the expansion stresses ~nd give the laminate more
d:imensional ~tabil:ity.
-31-
,

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Event History

Description Date
Inactive: IPC from MCD 2006-03-11
Inactive: Expired (old Act Patent) latest possible expiry date 1998-05-05
Grant by Issuance 1981-05-05

Abandonment History

There is no abandonment history.

Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
FIRESTONE TIRE & RUBBER COMPANY (THE)
Past Owners on Record
GEORG G. A. BOHM
JOHN N. ANDERSON
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Cover Page 1994-03-13 1 13
Claims 1994-03-13 8 308
Abstract 1994-03-13 1 26
Drawings 1994-03-13 1 29
Descriptions 1994-03-13 30 1,219