Laminate gas barrier layer for pneumatic tires

The invention provides a laminate suitable for use with a pneumatic tire having an inner liner or like air-impermeable layer capable of, for example, maintaining a requisite air pressure. The laminate I of the invention includes laminated films and a rubber layer (R), the laminated films being made of a gas barrier layer (A) and an adhesive layer (B), the layer (B) being provided on at least one side of the layer (A), the layer (A) being formed of at least one member selected from polyamide resins, polyester resins, polyarylate resins, polyamide-based alloys and polyester-based alloys, the laminated films being irradiated in at least one periphery with an electron beam, and the adhesive layer (B) being heat-bonded to the rubber layer (R). The laminate II of the invention includes laminated films and a rubber layer (R), the laminated films being made of a rubber-adhering layer (D), an adhesive layer (B) and a gas barrier layer (A), the layers (D), (B) and (A) being laminated in this order with a structure of at least three layers, the rubber-adhering layer (D) being formed of at least one polyolefin resin, the gas barrier layer (A) being formed of at least one member selected from polyamide resins, polyester resins, polyarylate resins, polyamide-based alloys and polyester-based alloys, the laminated films being irradiated in at least one periphery with an electron beam, and the rubber-adhering layer (D) being heat-bonded to the rubber layer (R).

The present invention relates to a laminate suitable for use, for example, 
with pneumatic tires having a gas-impermeable layer, such as an inner 
liner, which is capable of maintaining a requisite air pressure. 
In accord with the current trends to arouse energy-saving concern, tackle 
measures against global warming arising from the release of carbon dioxide 
and conserve global environment, it has been earnestly desired to reduce 
the weight of automobiles and other machines using a fossil fuel as a 
power source. 
Conventionally, pneumatic tires have been lined with an inner liner of 
materials having relatively low gas-impermeability such as halogenated 
butyl rubber or the like to maintain a requisite air pressure. However, 
halogenated butyl rubber raises a problem as associated with its great 
hysteresis loss. For example, referring to FIG. 1 attached hereto, a 
rubber portion b of the carcass layer, on vulcanization of a tire, may 
become zigzag at a boundary with an inner liner c, namely at a spacing f 
between carcass cords a, a. In this case, on rotation of the tire, the 
rubber of the inner liner c may be deformed together with the carcass 
layer. Consequently, there arises a problem of increased resistance to 
rotational motion. For this reason, usually an intermediate sheet of tie 
gum involving low hysteresis loss is laid between an inner liner of 
halogenated butyl rubber and a carcass layer to unite the two layers. Thus 
the thickness of a halogenated butyl rubber inner liner together with the 
thickness of the intermediate layer of tie gum adds up to a total 
thickness exceeding 1 mm (1,000 .mu.m) which in turn contributes to 
increased weight of the tire. 
Recently a new technique for reducing the weight of an inner liner in a 
tire was proposed. In the proposed pneumatic tire, a gas-impermeable layer 
such as a polyvinylidene chloride film, ethylene-vinyl alcohol copolymer 
film or the like is laminated over the inner periphery of the tire so as 
to form an adhesive layer therebetween such as a polyolefin film, 
aliphatic polyamide film, polyurethane film or the like (Japanese 
Unexamined Patent Publication No. 40207/1994). 
However, if the inner liner disclosed in the publication is comprised of 
laminated films like a polyolefin film/gas-impermeable film/polyolefin 
film (intermediate layers omitted), the vulcanization temperature must be 
lowered to a range which does not fuse or damage the inner liner, because 
said laminated films melt and fracture at a usual vulcanization 
temperature (about 180.degree. C. at the surface of inner liner in 
passenger car). Moreover, when a tire is held under a great load for a 
prolonged period, the laminated films of resins melting at 180.degree. C. 
or higher (such as a polyamide resin, polyester resin or the like) would 
tend to peel off from the inner periphery of the tire because of low 
adhesion. 
Further, if an ethylene-vinyl alcohol copolymer film or a polyvinylidene 
chloride film is used as a gas barrier layer (gas-impermeable layer) in 
the proposed tire, such film, which has low flexibility, tends to impair 
and readily become brittle on vulcanization. Moreover, the gas released 
from the rubber is liable to create bubbles and foams between the film and 
the rubber layer or within the film. For these reasons, the proposed tire 
is undesirable. 
In view of the foregoing situation, an object of the invention is to 
provide a laminate comprising laminated films and a rubber layer, the 
laminate being suitable for use as a component of a pneumatic tire and 
having an air pressure retentivity sufficient to retain the required air 
pressure in the tire, and high heat resistance, endurance and strength, 
and the laminated films being bonded as a gas-impermeable layer to the 
rubber of carcass layer to reduce the weight of the tire. 
According to the present invention, there is provided a laminate comprising 
laminated films and a rubber layer (R), the laminated films being 
comprised of gas barrier layer (A) and an adhesive layer (B), the layer 
(B) being provided on at least one side of the layer (A), the layer (A) 
being formed of at least one member selected from the group consisting of 
polyamide resins, polyester resins, polyarylate resins, polyamide-based 
alloys and polyester-based alloys, the laminated films being irradiated in 
at least one periphery with an electron beam, and the adhesive layer (B) 
being heat-bonded to the rubber layer (R) (hereinafter referred to as 
"laminate I"). 
According to the invention, there is also provided a laminate comprising 
laminated films and a rubber layer (R), the laminated films being 
comprised of a rubber-adhering layer (D), an adhesive layer (B) and a gas 
barrier layer (A), the layers (D), (B) and (A) being laminated in this 
order with a structure of at least three layers, the rubber-adhering layer 
(D) being formed of at least one polyolefin resin, the gas barrier layer 
(A) being formed of at least one member selected from the group consisting 
of polyamide resins, polyester resins, polyarylate resins, polyamide-based 
alloys and polyester-based alloys, the laminated films being irradiated in 
at east one periphery with an electron beam, and the rubber-adhering layer 
(D) being heat-bonded to the rubber layer (R) (hereinafter referred to as 
"laminate II"). 
The laminates I and II of the present invention are excellent in the 
adhesion to the rubber and in the mechanical strength (flex cracking 
resistance), air pressure retentivity, heat resistance, etc. 
When a tire having the laminate I or II inside is vulcanized with heating 
at a temperature of, e.g. 180.degree. C., the laminated films of the 
laminate, because of their high heat resistance, are unlikely to melt or 
fracture at their surface, resulting in an increased molding efficiency. 
The laminated films of the laminates I and II, which are tough although 
thin, contribute to reduced weight of the tire, and provide a tire with 
high endurance. 
The gas barrier (A) having air pressure-retentivity is formed in the 
invention from at least one resin selected from the group consisting of 
polyamide resins, polyester resins, polyarylate resins, polyamide-based 
alloys and polyester-based alloys. 
Examples of useful polyamide resins are aliphatic polyamide resins, 
amorphous polyamide resins, aromatic polyamide resins, and blends thereof. 
Useful aliphatic polyamide resins can be any of suitable resins having no 
aromatic ring in the main chain and/or side chain. Specific examples are 
nylon 6, nylon 66, nylon 610, nylon 12 and like polyamides, nylon 6-66 
copolymers, nylon 6-610 copolymers and like copolyamides, nylon 
66-polyethylene glycol block copolymers, nylon 6-polypropylene glycol 
block copolymers and like polyamide-based elastomers. 
Useful aromatic polyamide resins can be any of suitable resins having an 
aromatic ring in the main chain and/or side chain, such as 
polyxylylene-based polymers prepared by polycondensation of meta- or 
para-xylylenediamine with a dicarboxylic acid having 4 to 12 carbon atoms. 
Such polymers have characteristics such as gas barrier properties, low 
water-absorbing capacity, low moisture permeability, etc. 
The term "amorphous polyamide resins" used herein refers to 
non-crystallizable or scarcely crystallizable polyamide resins but without 
specific limitation. Specific examples are copolymers or terpolymers 
composed of terephthalic acid, isophthalic acid or like dicarboxylic acids 
and hexamethylenediamine or like diamines. Such amorphous polyamide resins 
are excellent in the gas barrier properties at high humidities. 
Useful polyester resins include, for example, polyester-based resins 
composed of a dicarboxylic acid component and a diol component. Examples 
of dicarboxylic acid components are aliphatic dicarboxylic acids, aromatic 
dicarboxylic acids, alicyclic dicarboxylic acids and mixtures thereof. 
More specific examples of aliphatic dicarboxylic acids are adipic acid, 
sebasic acid, dodecanoic acid, etc. which have 2 to 20 carbon atoms. 
Useful aromatic dicarboxylic acids are, for example, terephthalic acid, 
isophthalic acid, naphthalenedi-carboxylic acid, etc. Useful alicyclic 
dicarboxyic acids are, for example, cyclohexanedicarboxylic acid, etc. 
Useful diol components are aliphatic glycols, alicyclic glycols and 
mixtures thereof. Specific examples of aliphatic glycols are ethylene 
glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 
etc. Specific examples of alicyclic glycols are 1,4-cyclohexanediol, etc; 
Polyester resins for use in the invention include, for example, 
polybutylene terephthalate-polytetramethylene oxide glycol block 
copolymers, polybutylene terephthalate-polycaprolactone block copolymers, 
etc. 
Useful polyarylate resins are, for example, polyesters of bivalent phenol 
with aromatic dibasic acid, etc. More specific examples include copolymers 
of bisphenol A with terephthalic acid/isophthalic acid, etc. 
Examples of polyamide-based alloys and polyester-based alloys are 
polymer-based alloys prepared by kneading a sea component and an island 
component, optionally in the presence of a compatibilizing agent. The sea 
component to be used in the invention is at least one member selected from 
said polyamide resins and polyester resins, and the island component to be 
used in the invention is at least one member selected from suitable 
thermoplastic resins such as polyphenylene ether (PPE), polyarylate () 
and polycarbonate (PC). The foregoing sea and island components can be 
used vice versa. Preferred examples of polymer-based alloys are those 
having a sea-island structure, such as polyphenylene ether/polyamide 
alloy, polyarylate/polyamide alloy, polycarbonate/polyamide alloy, 
polyphenylene ether/polyester alloy, polyarylate/polyester alloy and 
polycarbonate/polyester alloy. Optionally a suitable third component may 
be added to the polyamide resins, polyester resins, polyarylate resins, or 
alloys. In the practice of the invention, it is possible to use 
polymer-blended alloys other than the polymer-based alloys of sea-island 
structure. These alloys are included in the range of alloys useful in the 
invention. 
In the above preparation of alloys, useful compatibilizing agents are not 
critical and include, for example, block or random copolymers having an 
affinity for the sea component or the island component, styrene-maleic 
anhydride copolymers, polyphenylene ether-maleic anhydride-modified 
copolymers, arylate-maleic anhydride copolymers, epoxy-containing styrene 
polymers, etc. The amount of the compatibilizing agent used is not 
specifically limited but usually in the range of about 1 to about 5% by 
weight based on the total amount of at least one member selected from 
polyamide resins and polyester resins, and at least one member selected 
from suitable thermoplastic resins such as polyphenylene ether (PPE), 
polyarylate () and polycarbonate (PC). 
Of the above polyamide resins, nylon 6, nylon 66, etc. are preferable, and 
of the above polyester resins, polybutylene terephthalate (PBT), 
polyethylene terephthalate (PET), etc. are preferable. However, these 
resins are not limitative. Useful polyphenylene ethers are not 
specifically limited, and include polymers containing 
poly(2,6-dimethylphenylene oxide) as a main component and having an ether 
bond. Useful polyarylates include, for example, polyesters of bivalent 
phenol with aromatic dibasic acid, etc., such as polyesters of bisphenol A 
with terephthalic acid/isophthalic acid. Useful polycarbonates are 
polymers prepared by interfacial polycondensation of sodium salt of 
bisphenol A with phosgene, or polymers prepared by ester exchange of 
bisphenol A with diphenyl carbonate. 
Useful resins for forming the gas barrier layer (A) in the invention 
include, for example, polyamide resins, polyester resins, polyarylate 
resins, polyamide-based alloys and polyester-based alloys. These resins 
can be used singly or in mixture with each other. 
The adhesive layer (B) formed in the invention is provided to adhere to the 
gas barrier layer (A) and the rubber layer (R) or to adhere to the gas 
barrier layer (A) and the rubber-adhering layer (D). Typical adhesive 
resins for producing the adhesive layer (B) include, for example, modified 
polymers prepared by copolymerizing or graft-copolymerizing a homopolymer 
or copolymer of olefins with maleic acid, fumaric acid, acrylic acid or 
like unsaturated carboxylic acid, anhydrides, esters, metal salts or like 
derivatives thereof, and other modified polymers such as ethylene glycidyl 
methacrylate-methyl acrylate terpolymers, ethylene-ethyl acrylate-maleic 
anhydride terpolymers, etc. The term "modified polymer" used herein 
includes a mixture of said modified polymers with other components such as 
other polyolefin resins. Further, these adhesive resins can be used in 
mixture with each other. A suitable adhesive agent can be used for forming 
the adhesive layer (B). 
Examples of useful polyolefin resins as the component of said modified 
polymers are homopolymers of olefins, copolymers of olefins with each 
other, copolymers of olefins with other copolymerizable monomers, such as 
vinyl monomers, and mixtures thereof. More specific examples of such 
polyolefin resins are polyethylenes having low to high densities 
[including linear low-density polyethylenes (LLDPE), and very low-density 
polyethylenes (VLDPE)], polypropylene, polybutene, copolymers thereof with 
each other, ethylene-vinyl acetate copolymers (EVA), ethylene-ethyl 
acrylate copolymers (EEA), ethylene-acrylic acid copolymers (EAA), 
ethylene-methyl acrylate copolymers (EMA), ethylene-methyl methacrylate 
copolymers (EMMA), ethylene-methacrylic acid copolymers (EMAA), etc. In 
the present invention, these polyolefin resins can be used singly or at 
least two of them are usable in mixture. Polyolefin resins usable in the 
invention include mixtures of such polyolefin resins with a suitable 
elastomer, e.g. ethylene-propylene elastomer, a small amount of styrene 
elastomer or the like. 
The rubber-adhering layer (D) formed in the invention is provided to adhere 
to the rubber layer or the like, for example, superposed on the inner 
periphery of a tire. Polyolefin resins for forming the rubber-adhering 
layer (D) are homopolymers of olefins, copolymers of olefins with each 
other, copolymers of olefins with other copolymerizable monomers, such as 
other vinyl monomers, and mixtures thereof. More specific examples of such 
polyolefin resins are polyethylenes having low to high densities 
(including linear low-density polyethylenes (LLDPE), and very low-density 
polyethylenes (VLDPE)), polypropylene, polybutene and copolymers thereof 
with each other, ethylene-vinyl acetate copolymers (EVA), ethylene-ethyl 
acrylate copolymers (EEA), ethylene-acrylic acid copolymers (EAA), 
ethylene-methyl acrylate copolymers (EMA), ethylene-methyl methacrylate 
copolymers (EMMA), ethylene-methacrylic acid copolymers (EMAA), etc. In 
the present invention, these polyolefin resins can be used singly or at 
least two of them are usable in mixture. Polyolefin resins usable in the 
invention include mixtures of such polyolefin resins with a suitable 
elastomer, e.g. ethylene-propylene elastomer, a small amount of styrene 
elastomer or the like. 
There is no restriction on the composition of the rubber layer (R) 
(corresponding to the carcass layer in FIG. 3). Useful rubber compositions 
comprise at least one member selected from the group consisting of 
diene-based rubbers, hydrogenated diene-based rubbers, olefin-based 
rubbers, halogen-containing rubbers and thermoplastic elastomers. Examples 
of diene-based rubbers and hydrogenated diene-based rubbers are natural 
rubbers, polyisoprene rubbers, epoxidized natural rubbers, 
styrene-butadiene copolymer rubbers, polybutadiene rubbers (high-cis or 
low-cis butadiene rubbers), acrylonitrile-butadiene rubbers, hydrogenated 
acrylonitrile-butadiene rubbers, hydrogenated styrene-butadiene rubbers, 
etc. Typical of olefin-based rubbers are ethylene-propylene-diene 
terpolymer rubbers (EPDM, EPM, etc.), maleic acid-modified 
ethylene-propylene copolymer rubbers (M-EPM), butyl rubber (IIR), 
copolymers of isobutyrene and aromatic vinyl or diene-based monomers, etc. 
Exemplary of halogen-containing rubbers are butyl bromide rubbers, 
chlorinated butyl rubbers, bromide of isobutylene-p-methyl styrene 
copolymer (Br-IPMS), chlorosulfonated polyethylene (CSM), chlorinated 
polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), 
etc. Illustrative of thermoplastic elastomers are styrene-based 
elastomers, olefin-based elastomers and ester-based elastomers, etc. The 
rubber composition may contain additives such as carbon black, process 
oil, vulcanizing agents, etc. The rubber layer (R), although sufficient in 
strength, may contain reinforcements such as carcass cords embedded 
therein. The rubber layer (R) formed in the invention includes all of such 
rubber layers. A layer of suitable material may be deposited, of course, 
on the other side than the side of the rubber layer heat-bonded to the 
laminated films. The carcass layer 2 contains the rubber portion b (rubber 
coating) and the carcass cords a. However, in respect of the tires, the 
carcass layer 2 is treated herein as an equivalent of the rubber layer (R) 
to facilitate understanding.

In the drawings, a carcass cord is designated a; a rubber portion of the 
carcass layer, b; an inner liner, c; a bead core, 1; a carcass layer, 2; 
an inner liner, 3; a side wall, 4; a spliced portion, 5; a belt layer, 6; 
a gas barrier layer, (A); an adhesive layer, (B); and a rubber-adhering 
layer, (C). 
The structure of the pneumatic tire according to the invention is described 
below in more detail with reference to FIG. 2. 
In FIG. 2, a carcass layer 2 is laid between a pair of bead cores 1, 1 at 
left and right sides. An inner liner 3 is formed on the inner periphery of 
the carcass layer 2 inside of the tire, while a side wall 4 is disposed on 
the outer periphery of the carcass layer 2. 
First, the laminate I is described below. 
FIG. 3 is an enlarged sectional view of X portion of FIG. 2. An inner liner 
3 is comprised of laminated films comprising a gas barrier layer (A) and 
an adhesive layer(s) (B). The adhesive layer (B) is made of a modified 
polyolefin resin or the like and is laminated on at least one surface of 
the gas barrier layer (A). The gas barrier layer (A) is formed of at least 
one member selected from the group consisting of polyamide resins, 
polyester resins, polyarylate resins, polyamide-based alloys and 
polyester-based alloys. 
The adhesive layer (B) of the laminate I may be formed, as stated above, of 
a modified polyolefin resin. A modified polyolefin resin may melt or a 
film of this resin may fracture at a vulcanization temperature depending 
on the type of the resin. To avoid this objection, the adhesive layer (B) 
of the laminated films is essentially crosslinked for reinforcement in the 
practice of the invention. The crosslinking can be effected by irradiating 
one side or preferably both sides of the laminated films with an electron 
beam. 
The thickness of the laminated films in the laminate I is at least 10 
.mu.m, preferably 25 to 200 .mu.m, more preferably 50 to 150 .mu.m. If the 
thickness is less than 10 .mu.m, an increased air permeability results. 
For example, if the laminated films of such thickness are used for the 
inner liner of a pneumatic tire, the retentivity of air pressure is 
reduced, whereby it is made unlikely to maintain a requisite air pressure. 
The thickness of the laminated films is not specifically limited, and may 
be, of course, outside said range of film thickness, if necessary. 
The thickness of the adhesive layer (B) to be bonded to the rubber layer 
(R) in the laminate I is in the range of 5 to 200 .mu.m, preferably 10 to 
100 .mu.m, more preferably 15 to 80 .mu.m. A thickness of less than 5 
.mu.m lowers the adhesion of the layer (B) to the rubber layer (R), 
whereas a thickness of more than 200 .mu.m tends to make the layer (B) 
rigid. Thus the thickness outside said range is undesirable. The thickness 
of the gas barrier layer (A) should be sufficient, for example, to sustain 
a requisite air pressure. The thickness of the layer (A) is preferably at 
least 3 .mu.m, more preferably 3 to 50 .mu.m. A thickness of less than 3 
.mu.m decreases the air pressure retentivity, making it unlikely to 
maintain the required air pressure. 
The thickness of the rubber layer (R) to be bonded to the adhesive layer 
(B) is variable depending on the purpose of use and is not specifically 
limited. For example, when the rubber layer is used as the carcass layer 
of the tire, a suitable thickness may be about 0.5 to abut 2.0 mm. 
A preferred embodiment of the laminate I according to the invention 
comprises the rubber layer (R) and laminated films having at least 2-layer 
structure. For example, the adhesive layer (B) is laminated on the gas 
barrier layer (A) while the rubber layer (R) is laminated on the adhesive 
layer (B). That is to say, the embodiment has a structure of (A)/(B)/(R) 
or (B)/(A)/(B)/(R). Optionally the laminate (I) may have at least one 
suitable intermediate layer sandwiched between the layers (A)/(B). A 
specific example of such structure is a combination of 
(B.sub.1)/(B.sub.2)/(A)/(B.sub.2)/(B.sub.1)/(R). In this structure, the 
layers (B.sub.1) and (B.sub.2) may be, of course, made of the same or 
different adhesive resins. 
To produce a tire using the laminate I, the laminate I is arranged, for 
example, on the inner periphery of the tire as described later, and the 
tire is vulcanized and molded in a suitable manner. In this case, the 
adhesive layer (B) is heat-bonded to the rubber layer (R) during 
vulcanization. In this way, usually the heating adhesion is performed 
concurrently with vulcanization. Of course, the heating adhesion may be 
carried out independently of vulcanization. The heating adhesion is 
effected preferably at a temperature of about 130 to about 200.degree. C., 
but the temperature range is not critical. 
A method of preparing the laminated films in the laminate I is described 
below. 
The laminated films of the laminate I are formed in a tubular form by an 
inflation method or in a flat form by a T-die co-extrusion method, 
respectively using a proper device such as a co-extrusion device, without 
specific limitation. When required, the laminated films may be stretched. 
Stretching is carried out, for example, after preheating the laminated 
films cooled after the formation, by various methods such as sequentially 
biaxial stretching, concurrently biaxial stretching, concurrently biaxial 
tube-stretching, stretching by a separate procedure, melt-stretching, etc. 
According to the invention, the draw ratio is not specifically limited. For 
example, the laminated films can be drawn to more than 1 times to 4 times, 
preferably more than 1 times to 2 times, the length and/or the width of 
the films. The drawing temperature is not critical, but usually in the 
range of about 100 to about 200.degree. C., preferably about 120 to about 
180.degree. C. 
Optionally the laminated films may be thermally fixed by conventional 
methods, as by being thermally fixed at a higher temperature than the 
drawing temperature after stretching while being relaxed widthwise of the 
films by several percents. However, the fixing method is not specifically 
limited. 
Lamination methods are not critical in the practice of the invention and 
include various methods in addition to the co-extrusion method described 
above. For example, a pressure heating adhesion method is available which 
comprises separately forming an adhesive layer and a gas barrier layer, 
while optionally forming an anchor coating. Another extrusion lamination 
method is employable. It comprises depositing a melt of resins for forming 
an adhesive layer by extrusion on the surface of a gas barrier layer, 
while optionally forming an anchor coating. 
According to the invention, the laminated films with the adhesive layer (B) 
superposed on at least one side of the gas barrier layer (A) are 
essentially crosslinked to improve the heat resistance and to increase the 
adhesion between the layers (A) and (B). 
Preferably the crosslinking is conducted by irradiating at least one 
surface, preferably both surfaces, of the laminated films with an electron 
beam. In crosslinking the laminated films having the layers (B) on both 
sides thereof, the laminated films are desirably irradiated at both sides 
with an electron beam. Optionally an electron beam crosslinking agent, 
such as triallyl isocyanurate, triallyl cyanurate, trimethylol-propane 
trimethacrylate, etc. may be incorporated into a suitable layer of the 
laminated films. The amount of such crosslinking agent used is not 
critical, but is about 1 to about 5 parts by weight per 100 parts by 
weight of the material used for said layer. When an electron beam 
crosslinking agent is used, the exposure. dose can be reduced. 
The laminated films are irradiated on at least one side with an electron 
beam in a dose of up to 40 Mrad, preferably 5 to 15 Mrad at an 
accelerating voltage of at least 150 kV, preferably 150 to 250 kV, more 
preferably 200 to 250 kV. When an electron beam crosslinking agent is 
used, the exposure dose is up to 40 Mrad, preferably 0.1 to 40 Mrad, more 
preferably 1 to 20 Mrad. 
An accelerating voltage of less than 150 kV is unlikely to expose the 
laminated films to uniform irradiation of electron beam from the front 
side to the rear side of the films and is hence undesirable. An exposure 
dose exceeding 40 Mrad is liable to reduce the adhesion to the rubber 
layer (R) and is hence undesirable. 
The laminated films thus irradiated with an electron beam are crosslinked 
at the layer (B) and are improved in the film strength and heat 
resistance. 
To produce the pneumatic tire according to the invention, the laminated 
films are wound around a drum for forming a tire. Subsequently a carcass 
layer, a side wall, bead cores, bead apexes, a steel belt layer, and a 
tread rubber layer are laminated over each other in a conventional manner 
to form a green tire of unvulcanized rubber. Then the green tire is placed 
into a mold and vulcanized and molded in a conventional manner while the 
films are heat-bonded. In this way, an inner liner comprised of the 
laminated films can be superposed on the inner periphery of the carcass 
layer 2 inside the tire. It is possible in the practice of the invention 
to further incorporate a rubber layer (R') of tie gum or the like between 
the carcass layer 2 and the adhesive layer (B). In this structure, a 
combination of layers is partly shown as "carcass layer 2/rubber layer 
(R')/adhesive layer (B). . ." wherein the rubber layer (R) may be double 
arranged. 
When the adhesive layer (B) is formed at both peripheries of the inner 
liner 3, the adhesive layers (B), (B) are brought into contact with each 
other at a spliced portion 5 of the inner liner 3 as shown in FIG. 4. Thus 
the layers (B), (B) can be firmly bonded together when heated and the air 
pressure retentivity can be increased. Further, this structure can 
eliminate the possibility that a bladder placed inside the tire in 
vulcanization may come into direct contact with the gas barrier layer (A). 
Consequently the gas barrier layer (A) can be thermally and mechanically 
protected. 
Another tire forming method is available. The method comprises the steps of 
laminating the laminated films on the carcass layer 2, winding the 
prelaminated layer (laminated films plus carcass layer) around a tire 
forming drum, superposing a side wall, bead cores, bead apexes, a steel 
belt layer, and a tread rubber layer over each other in a conventional 
manner to give a green tire of unvulcanized rubber, placing the green tire 
into a mold, and vulcanizing the green tire in a conventional manner while 
the films are heat-bonded. In this case, when the adhesive layer (B) is 
arranged at both peripheries of the laminate I, it is possible to prevent 
the gas barrier layer (A) from being directly heat-bonded to the carcass 
layer 2 at the spliced portion 5 of the inner liner 3 as shown in FIG. 5. 
In this case, a high adhesion can be imparted. 
The foregoing inner liner is a layer capable of inhibiting the penetration 
of a gas, as set forth above and may be formed at an intermediate portion 
of a pneumatic tire although termed with a restrictive word "inner". 
Next, the laminate II is described below. 
FIG. 6 is an enlarged view of X portion of FIG. 2. An inner liner 3 is 
comprised of laminated films comprising a gas barrier layer (A), adhesive 
layers (B) and rubber-adhering layers (D). The gas barrier layer (A) is 
formed of at least one member selected from the. group consisting of 
polyamide resins, polyester resins, polyarylate resins, polyamide-based 
alloys and polyester-based alloys. The adhesive layer (B) is made of a 
modified polyolefin resin or the like and is laminated on both peripheries 
of the gas barrier layer (A). The layer (D) is formed of a polyolefin 
resin or the like and may be laid on both peripheries of the layer (B). 
The layer (B) is bonded indirectly to the carcass layer 2 since the layer 
(D) is interposed therebetween. 
The rubber-adhering layer (D) of polyolefin resin in the laminate II may 
pose a problem. A polyolefin resin may melt and the film of this resin may 
fracture at a vulcanization temperature depending on the type of the 
resin. To avoid this objection, the rubber-adhering layer (D) and the 
adhesive layer (B) are essentially crosslinked for reinforcement. The 
crosslinking can be effected by irradiating one periphery, preferably both 
peripheries, of the laminated films with an electron beam. 
The thickness of the laminated films essentially having the rubber layer 
(D) in the laminate II is 20 to 300 .mu.m, preferably 25 to 200 .mu.m, 
more preferably 50 to 150 .mu.m. If the thickness is less than 20 .mu.m, 
an increased air permeability results. For example, if the laminated films 
of such thickness are used for the inner liner of a pneumatic tire, the 
retentivity of air pressure is reduced, whereby it is made unlikley to 
maintain a requisite air pressure. A thickness of more than 300 .mu.m is 
unliable to impart the desired flexibility. Thus a greater or smaller 
thickness of the laminated films in the laminate II than said range is 
undesirable. 
The thickness of the rubber-adhering layer (D) to be bonded to the rubber 
is in the range of 5 to 200 .mu.m, preferably 10 to 100 .mu.m, more 
preferably 15 to 80 .mu.m. A thickness of less than 5 .mu.m lowers the 
adhesion-of the layer (D) to the rubber, whereas a thickness of more than 
200 .mu.m tends to make the layer (D) rigid. Hence the thickness outside 
said range is undesirable. The thickness of the adhesive layer (B) in the 
laminate II is in the range sufficient to bond the layer (D) to the layer 
(A), and is preferably up to 3 .mu.m. The thickness of the gas barrier 
layer (A) is in the range sufficient, for example, to retain a requisite 
air pressure, and is preferably at least 3 .mu.m, preferably 3 to 50 
.mu.m. A thickness of less than 3 .mu.m reduces the air pressure 
retentivity, resulting in an unlikelihood of maintaining a requisite air 
pressure. Therefore, the thickness of the layer (A) outside said range is 
undesirable. 
The thickness of the rubber layer (R) to be. bonded to the rubber-adhering 
layer (D) is variable depending on the purpose of use and is not 
specifically limited. For example, when the rubber layer is used as the 
carcass layer of the tire, a suitable thickness may be about 0.5 to about 
2.0 mm. 
A preferred embodiment of the laminate II according to the invention 
comprises laminated films having the following structure. The adhesive 
layer (B) is present between the gas barrier layer (A) and rubber-adhering 
layer (D). The layers (D), (D) are provided as two external layers and the 
rubber layer (R) can be further laminated thereon. That is, the embodiment 
has a structure of (D)/(B)/(A)/(B)/(D)/(R), or (A)/(B)/(D)/(R). The 
laminate (II) may have a suitable intermediate layer, optionally two or 
more intermediate layers, interposed between the layers (D)/(B)/(A). A 
specific example of such structure is a combination of 
(A)/(B.sub.1)/(B.sub.2)/(D)/(R). In this structure, the layers (B.sub.1) 
and (B.sub.2) may be, of course, made of the same or different adhesive 
resins. 
To produce a tire using the laminate II, the laminate II is mounted, for 
example, on the inner periphery of the tire as described later, and the 
tire is vulcanized in a suitable manner. In the practice of the invention, 
the rubber-adhering layer (D) is heat-bonded to the rubber layer (R) 
during vulcanization. In this way, usually the heating adhesion is 
performed concurrently with vulcanization. Of course, the heating adhesion 
may be carried out independently of vulcanization. The heating adhesion is 
effected preferably at a temperature of about 130 to about 200.degree. C., 
but the temperature range is not critical. 
A method of preparing the laminated films in the laminate II is described 
below. 
The laminated films of the laminate II are formed in a tubular form by an 
inflation method or in a flat form by a T-die co-extrusion method, 
respectively using a proper device such as a co-extrusion device, without 
specific limitation. When required, the laminated films may be stretched. 
Stretching is carried out, for example, after preheating the laminated 
films cooled after the formation, by various methods such as sequentially 
biaxial stretching, concurrently biaxial stretching, concurrently biaxial 
tube-stretching, stretching involving a separate procedure, 
melt-stretching etc. 
According to the invention, the draw ratio is not specifically limited. For 
example, the laminated films can be drawn to more than 1 to 4 times, 
preferably more than 1 to 2 times, the length and the width respectively 
of the film. The drawing temperature is not critical, but usually in the 
range of about 100 to about 200.degree. C., preferably about 120 to about 
180.degree. C. 
When required, the laminated films may be thermally fixed by conventional 
methods, as by being thermally fixed at a higher temperature than the 
drawing temperature after stretching while being relaxed widthwise of the 
films by several percents. However, the fixing method is not specifically 
limited. 
Lamination methods are not critical in the practice of the invention and 
include various methods in addition to the co-extrusion method described 
above. For example, a pressure heating adhesion method is available which 
comprises separately forming a rubber-adhering layer and a gas barrier 
layer so as to produce an adhesive layer between said layers. There is a 
dry laminating method comprising laminating layers and forming 
intermediate layers of an adhesive agent therebetween. Another extrusion 
lamination method is employable. It comprises depositing a melt of resins 
for rubber-adhering layers by extrusion on the surface of a gas barrier 
layer so as to produce adhesive layers between the layers. 
It is essential in the invention, as described hereinbefore, to crosslink 
the laminated films in order to improve the heat resistance. 
Preferably the crosslinking is conducted by irradiating at least one 
surface of the laminated films with an electron beam. In crosslinking the 
laminated films having the layer (D) on both sides thereof, the laminated 
films are desirably irradiated at both sides with an electron beam. 
Optionally an electron beam crosslinking agent, such as triallyl 
isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, etc. 
may be incorporated into a suitable layer of the laminated films. The 
amount of such crosslinking agent used is not critical, but is about 1 to 
about 5 parts by weight per 100 parts by weight of the material used for 
said layer. When an electron beam crosslinking agent is used, the exposure 
dose can be reduced. 
The laminated films are irradiated on at least one side with an electron 
beam in a dose of up to 40 Mrad, preferably 5 to 15 Mrad at an 
accelerating voltage of at least 150 kV, preferably 150 to 250 kV, more 
preferably 200 to 250 kV. When an electron beam crosslinking agent is 
used, the exposure dose is up to 40 Mrad, preferably 0.1 to 40 Mrad, more 
preferably 1 to 20 Mrad. 
An accelerating voltage of less than 150 kV is unlikely to expose the 
laminated films to uniform irradiation of electron beam from the front 
side to the rear side of the films and is hence undesirable. An exposure 
dose exceeding 40 Mrad is liable to reduce the adhesion to the rubber 
layer (R) and is hence undesirable. 
The laminated films thus irradiated with an electron beam are crosslinked 
at the rubber-adhering layer (D) and the adhesive layer (B) and are 
improved in the film strength and heat resistance. 
To produce the pneumatic tire according to the invention, the laminated 
films are wound around a drum for forming a tire. Subsequently a carcass 
layer, a side wall, bead cores, bead apexes, steel belt layer, and a tread 
rubber layer are laminated over each other in a conventional manner to 
form a green tire of unvulcanized rubber. Then the green tire is placed 
into a mold and vulcanized while the films are heat-bonded in a 
conventional manner. In this way, the inner liner 3 comprised of the 
laminated films can be superposed on the inner periphery of the carcass 
layer 2 inside the tire. It is possible in the practice of the invention 
to incorporate a rubber layer (R') of tie gum or the like between the 
carcass layer 2 and the rubber-adhering layer (D). In this structure, a 
combination of layers is partly shown as "carcass layer 2/rubber layer 
(R')/rubber-adhering layer (D). . ." wherein the rubber layer (R) may be 
double arranged. 
When the rubber-adhering layer is formed at both peripheries of the inner 
liner 3, the layers (D), (D) are brought into contact with each other at a 
spliced portion 5 of the inner liner 3 as shown in FIG. 7. Thus the layers 
(D), (D) can be firmly bonded together when heated and the air pressure 
retentivity can be increased. Further, this structure can eliminate the 
possibility that a bladder placed inside the tire in vulcanization may 
come into direct contact with the gas barrier layer (A). Consequently the 
gas barrier layer (A) can be thermally and mechanically protected. 
Another tire forming method is usable. It comprises the steps of laminating 
the laminated films on the carcass layer 2, winding the prelaminated layer 
(laminated films plus carcass layer) around a tire forming drum, 
superposing a side wall, bead cores, bead apexes, a steel belt layer, and 
a tread rubber layer over each other in a conventional manner to give a 
green tire of unvulcanized rubber, placing the green tire into a mold, and 
vulcanizing the green tire in a conventional manner while the films are 
heat-bonded. In this case, when the rubber adhering layer (D) is arranged 
at both peripheries of the laminate II, it is possible to prevent the gas 
barrier layer (A) from being directly heat-bonded to the carcass layer 2 
at the spliced portion 5 of the inner liner 3 as shown in FIG. 8, whereby 
a high adhesion can be imparted. 
The foregoing inner liner is a layer capable of inhibiting the penetration 
of a gas, as set forth above and may be formed at an intermediate portion 
of a pneumatic tire, irrespectively of a restrictive word "inner". 
Described above are preferred embodiments of the present invention to which 
the invention, however, is not limited at all. It is a matter of course 
that other embodiments are employable and various modifications are 
possible without the deviation from the scope of the invention. 
According to one aspect of the invention, there is provided a laminate 
comprising laminated films and a rubber layer (R), the laminated films 
being comprised of a gas barrier layer (A) and an adhesive layer (B), the 
layer (B) being provided on at least one side of the layer (A), the layer 
(A) being formed of at least one member selected from the group consisting 
of polyamide resins, polyester resins, polyarylate resins, polyamide-based 
alloys and polyester-based alloys, the laminated films being irradiated in 
at least one periphery with an electron beam, and the adhesive layer (B) 
being heat-bonded to the rubber layer (R). 
According to another aspect of the invention, there is also provided a 
laminate comprising laminated films and a rubber layer (R), the laminated 
films being comprised of a rubber-adhering layer (D), an adhesive layer 
(B) and a gas barrier layer (A), the layers (D), (B) and (A) being 
laminated in this order with a structure of at least three layers, the 
rubber layer (R) being formed of at least one polyolefin resin, the gas 
barrier layer (A) being formed of at least one member selected from the 
group consisting of polyamide resins, polyester resins, polyarylate 
resins, polyamide-based alloys and polyester-based alloys, the laminated 
films being irradiated in at least one periphery with an electron beam, 
and the rubber-adhering layer (D) being heat-bonded to the rubber layer 
(R). 
The laminated films of the laminates I and II are irradiated with an 
electron beam on at least one periphery thereof. The laminates I and II 
are excellent in the film strength, adhesion to the rubber, gas 
impermeability (gas barrier properties), heat resistance, etc. These 
laminates can be used as the inner layer of a pneumatic tire (e.g. inner 
liner+carcass layer) and contribute to reduced weight of the tire. 
Examples and Comparative Examples are given below to clarify the invention 
in more detail. The invention, however, is not limited to the Examples at 
all. 
EXAMPLES 1 to 4 and COMATIVE EXAMPLE 1 
Adhesion Test 
The laminated films were subjected to confirmatory tests for the adhesion 
to rubbers. 
(1) Composition and Preparation of Test Rubbers 
The composition of test rubbers is shown below in Table 1. 
(i) Preparation of Test Rubbers with Compositions 1 to 7: 
Masterbatches were made by mixing together the other components than a 
vulcanizing accelerator and sulfur using a closed type mixer. The standard 
mixing time was 3.5 minutes and the maximum temperature for mixing was 
150.degree. C. The other components were added to each masterbatch using 
an open roll, giving an unvulcanized test rubber. 
(ii) Preparation of Test Rubbers with Composition 8: 
Masterbatches were made by mixing together the other components than zinc 
flower, a vulcanizing accelerator and sulfur using a closed type mixer. 
The standard mixing time was 3.5 minutes and the maximum temperature for 
mixing was 150.degree. C. The other components were added to each 
masterbatch using an open roll, giving an unvulcanized test rubber. 
TABLE 1 
__________________________________________________________________________ 
Comp. 1 Comp. 2 
Comp. 3 
Comp. 4 
Comp. 5 
Comp. 6 
Comp. 7 
Comp. 8 
__________________________________________________________________________ 
NR 100 65 50 40 25 
SBR 100 20 80 25 
BR 100 15 50 20 30 
EPT 30 
Br-IIR 50 
Carbon black 50 50 50 50 50 50 50 50 
FEF 
Aromatic oil 8 8 8 8 8 8 8 8 
ZnO 5 5 5 5 5 5 3 5 
Stearic acid 3 3 3 3 3 3 1 3 
RD 1 1 1 1 1 1 1 1 
DM 1 1 1 1 1 1 1 1 
Sulfur 2 2 2 2 2 2 2 2 
__________________________________________________________________________ 
Note: Comp. = Composition 
The components shown in Table 1 are specifically set forth below. 
NR: trade name "RSS #1" 
SBR: trade name "NIPOL 1502," product of Nippon Zeon Co., Ltd. 
BR: trade name "NIPOL BR 1220," product of Nippon Zeon Co., Ltd. 
EPT: trade name "ESPLEIN 505 A," product of Sumitomo Chemical Co., Ltd. 
Br-IIR: trade name "EXXON BROMOBUTYL 2244,"product of Exxon Chemical Japan 
Ltd. 
Carbon Black FEF: trade name "HTC 100," product of Chubu Carbon Co., Ltd. 
RD: trade name "NOCRAC 224," (antioxidant), product of Oh-uchi Shinko 
Chemical Industrial Co., Ltd. 
DM: trade name "NOCCELLER DM," (vulcanizing accelerator), product of 
Oh-uchi Shinko Chemical Industrial Co., Ltd. 
(2) Test Films 
Three-layer laminated films were produced by laminating a gas barrier layer 
(A) and adhesive layers (B) each formed from the components shown in Table 
2. The laminated films were prepared by co-extrusion and irradiated at 
both sides with an electron beam in a dose of 15 Mrad at an accelerating 
voltage of 200 kV. The thickness of the laminated films was 96 .mu.m 
((B)/(A)/(B)=30/36/30 .mu.m). The laminated films of Comparative Example 1 
were not exposed to an electron beam since the films were heat resistant. 
(3) Preparation of Samples for Adhesion Test and Method of Adhesion Test 
Samples were prepared and tested according to JIS K 6256. The samples were 
prepared by laminating rubber layers in the order of fabric-reinforced 
rubber/unvulcanized test rubber/test film/unvulcanized test 
rubber/fabric-reinforced rubber. The laminated films were vulcanized at 
180.degree. C. for 10 minutes and cut to 25 mm-wide rectangular sheets. 
The samples were placed on a peel tester, and the tester was operated with 
a gripper movable at a speed of 50.0.+-.5.0 mm/min to measure the peel 
strength between the laminated films and the test rubber. The other tests 
were carried out according to JIS K6256. Table 2 shows the results of 
adhesion test. 
TABLE 2 
__________________________________________________________________________ 
Film 
structure Example 1 Example 2 Example 3 Example 4 Com. Ex. 1 
__________________________________________________________________________ 
Layer (A) Nylon 66 Polyphenylene Nylon 6 Polyphenylene Nylon 66 
(Gas barrier ether-poly- ether-poly- 
layer) amide (nylon amide (nylon 
Thickness = 6) alloy* 6) alloy* 
36 .mu.m 
Layer (B) Ethylene- Ethylene- Ethylene- Ethylene- Nylon 6-66 
(Adhesive ethyl ethyl glycidyl glycidyl 
layer) acrylate-maleic acrylate-maleic methacrylate- methacrylate- 
Thickness = anhydride anhydride methyl 
methyl 
30 .mu.m terpolymer terpolymer acrylate ter- acrylate ter- 
polymer polymer 
__________________________________________________________________________ 
Note: *"ARTLEY Y 20S," product of Sumitomo Chemical Co., Ltd. 
Adhesive 
strength Example 1 Example 2 Example 3 Example 4 Com. Ex. 1 
__________________________________________________________________________ 
Comp. 1 1.58 1.62 2.05 2.10 0.33 
Comp. 2 2.52 2.45 3.08 3.00 0.48 
Comp. 3 2.33 2.27 2.82 2.88 0.45 
Comp. 4 1.89 1.63 2.44 2.52 0.38 
Comp. 5 1.85 1.82 2.26 2.30 0.39 
Comp. 6 1.52 1.48 1.85 1.78 0.28 
Comp. 7 1.12 1.08 1.32 1.35 0.21 
Comp. 8 2.38 2.35 2.95 2.90 0.47 
__________________________________________________________________________ 
Note: Unit = N/mm 
The desired adhesive strength between the test film and the test rubber is 
usually at least 0.5 N/mm. As apparent from Table 2, the films of Examples 
1 to 4 exceeded said adhesive strength range while the film of Comparative 
Example 1 was below said adhesive strength range. 
EXAMPLE 5 
Three-layer laminated films for a tire with a size of 185/65 R14 were 
prepared by co-extrusion so as to laminate adhesive layers (B) of 
ethylene-ethyl acrylate-maleic anhydride terpolymer on both sides of a gas 
barrier layer (A) of nylon 66 in the structure of FIG. 2. The laminated 
films were irradiated at both sides with an electron beam in a dose of 15 
Mrad at an accelerating voltage of 200 kV. The thickness of the laminated 
films was 96 .mu.m ((B)/(A)/(B)=30/36/30 .mu.m). 
The laminated films thus obtained were used as an inner liner. An 
unvulcanized tire with said inner liner laminated on the carcass layer 2 
was vulcanized at 180.degree. C. for 10 minutes to heat-bond the adhesive 
layer (B) to the carcass layer 2, giving a finished tire. Table 3 shows 
the visual evaluation of the obtained tire, visual evaluation of the tire 
after indoor endurance test, results of air leakage test, and measurements 
of the tire weight. 
TABLE 3 
__________________________________________________________________________ 
Example 5 
Example 6 
Example 7 
Example 8 
__________________________________________________________________________ 
Inner liner 
Layer (A) (gas Nylon 66 Polyphenylene Nylon 6 Polyphenylene 
barrier layer) ether/polyamide ether/polyamide 
Thickness = 36 .mu.m (nylon 6) alloy* (nylon 6) alloy* 
Layer (B) Ethylene-ethyl Ethylene-ethyl Ethylene- Ethylene- 
(adhesive layer) acrylate-maleic acrylate-maleic glycidyl glycidyl 
Thickness = 30 .mu.m anhydride anhydride 
methacrylate- methacrylate- 
terpolymer terpolymer methyl acrylate methyl acrylate 
terpolymer terpolymer 
Electron beam Irradiated Irradiated Irradiated Irradiated 
irradiation 
Evaluation after Good Good Good Good 
vulcanization 
Evaluation after Good Good Good Good 
indoor endurance 
test 
Degree of air 2.0 2.2 2.1 2.2 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) (92.4) 
__________________________________________________________________________ 
Comp. Example 2 
Comp. Example 3 
Comp. Example 4 
__________________________________________________________________________ 
Inner liner 
Layer (A) (gas Nylon 66 Nylon 6-10 Butyl rubber 
barrier layer) 500 .mu.m in 
Thickness = 36 .mu.m thickness 
Layer (B) Nylon 6-66 Maleic 
(adhesive layer) anhydride- 
Thickness = 30 .mu.m modified PP 
Electron beam Non-irradiated Non-irradiated Non-irradiated 
irradiation 
Evaluation after Impaired** Impaired (film Good 
vulcanization foamed) 
Evaluation after Impaired in Impaired in Good 
indoor endurance inner liner face inner liner face 
test (unevaluated) 
Degree of air 1.5 3.0 2.8 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.9 
(%) (92.4) (92.4) (100) 
__________________________________________________________________________ 
Note: *"ARTLEY Y 20S," product of Sumitomo Chemical Co., Ltd. 
**The rubber layer and the layer (B) were peeled. 
The rubber composition used for the carcass layer had the formulation as 
shown below in Table 4. The carcass layer had an array of polyester cords 
embedded in the rubber composition. 
TABLE 4 
______________________________________ 
Component Part by weight 
______________________________________ 
Natural rubber 80.0 
SBR 1502 20.0 
Carbon black FEF 50.0 
Stearic acid 2.0 
Zinc flower 3.0 
Sulfur 3.0 
Vulcanizing 1.0 
accelerator (NS) 
Aromatic oil 2.0 
______________________________________ 
In the Examples, the laminated films were evaluated or measured by the 
following methods in respect of the test items indicated in the tables. 
Evaluation After Vulcanization 
The inner periphery of the tire was visually inspected and evaluated after 
vulcanization. If no abnormality was found, the result of evaluation was 
expressed with "Good". If an abnormality was detected, it was represented 
with a word "Impaired" and specifically described. 
Evaluation After Indoor Endurance Test 
The indoor endurance test was carried out under the following conditions by 
the method described below. The inner periphery of the tire was visually 
inspected after the test. A flawless tire was indicated with a word 
"Good", while an impaired tire was expressed with a word "Impaired". The 
impairment of the tire was specifically set forth. 
The conditions for indoor endurance test, the test method, and the criteria 
for evaluation are as follows. 
Rim: 14.times.51/2-J 
Air pressure: 140 kPa Load: 6 kN 
Room temperature: 38.degree. C. 
The tire was let to travel at a speed of 80 km/h on a drum of 1707 mm in 
diameter. After travel over a distance of 10000 km, the inner periphery of 
the tire was visually evaluated. The tires were rated as rejects if 
cracking, flaking, floating layer or the like was detected. 
Degree of Air Leakage 
An air leakage test was performed as follows. 
The tire was fitted on a rim measuring 14.times.51/2-J at room temperature 
(21.degree. C.) and let to stand still for 48 hours under an internal 
pressure of 200 kPa. Then the internal pressure was readjusted to 200 kPa. 
The internal internal pressure was measured every 4 days over a period of 
3 months starting immediately after the readjustment. 
An air leakage coefficient a was calculated according to the formula 
EQU P.sub.t /P.sub.o =exp(-.alpha.t) 
wherein P.sub.t is a measurement of pressure, P.sub.o is an initial 
pressure and t is the number of days. 
A ratio (.beta.) of reduction in the internal pressure over a period of one 
month (%/month) was calculated by substituting 30 (days) for t according 
to the equation 
EQU .beta.=[1-exp(-.alpha.t)].times.100 
wherein .beta. is the ratio of reduction in the internal pressure and t is 
the number of days. 
EXAMPLES 6 to 8 
The procedure of Example 5 was repeated with the exception of using an 
inner liner formed from-the components shown in Table 3. Table 3 shows the 
visual evaluation of the obtained tire, visual evaluation of the tire 
after indoor endurance test, results of air leakage test, and measurements 
of the tire weight. 
COMATIVE EXAMPLE 2 
A tire was produced in the same manner as in Example 5 with the exception 
of using an inner liner formed from the components shown in Table 3 
without exposure to an electron beam. Table 3 shows the visual evaluation 
of the obtained tire, visual evaluation of the tire after indoor endurance 
test, results of air leakage test, and measurements of the tire weight. 
COMATIVE EXAMPLE 3 
A tire was produced in the same manner as in Example 5 with the exception 
of using an inner liner formed from the components shown in Table 3 
without exposure to an electron beam. Table 3 shows the visual evaluation 
of the obtained tire, visual evaluation of the tire after indoor endurance 
test, results of air leakage test, and measurements of the tire weight. 
COMATIVE EXAMPLE 4 
A tire was prepared by laminating, on the inner periphery of a green tire, 
a 500 .mu.m-thick inner liner of unvulcanized butyl rubber having the 
composition shown in Table 5 so as to form an intermediate layer of tie 
gum about 700 .mu.m in thickness therebetween. The green tire was 
vulcanized under the same conditions as in Example 5. Table 3 shows the 
visual evaluation of the tire after vulcanization, visual evaluation of 
the tire after indoor endurance test, results of air leakage test, and 
measurements of the tire weight. 
TABLE 5 
______________________________________ 
Component Part by weight 
______________________________________ 
Butyl bromide rubber 
100.0 
Carbon black FEF 50.0 
Stearic acid 1.0 
Zinc flower 3.0 
Sulfur 1.0 
Vulcanizing 1.0 
accelerator (DM) 
Aromatic oil 10.0 
______________________________________ 
As apparent from Table 3, no impairment was found in the inner liners on 
the tires of Examples 5 to 8 after vulcanization and after indoor 
endurance test. These inner liners were comparable or superior in the 
degree of air leakage to inner liners of butyl rubber. A 7.6% decrease of 
the tire weight was realized by a 1/5 reduction in the thickness of the 
inner liners. 
The tire of Comparative Example 2 produced without exposure to an electron 
beam was rated as unacceptable after indoor endurance test. Hence it was 
improper. 
The inner liner of Comparative Example 3 produced without exposure to an 
electron beam created bubbles although otherwise in accord with the 
requirements of the invention and was evaluated as unacceptable after 
vulcanization. Hence it was improper. 
EXAMPLES 9 and 10 
The procedure of Example 5 was repeated except that the gas barrier layers 
(A) had the thicknesses shown in Table 6. Table 6 shows the visual 
evaluation of the obtained tire, visual evaluation of the tire after 
indoor endurance test, results of air leakage test, and measurements of 
the tire weight. 
TABLE 6 
______________________________________ 
Example 9 
Example 10 
______________________________________ 
Thickness of layer (A) 
3 .mu.m 50 .mu.m 
Electron beam irradiation Irradiated Irradiated 
Evaluation after vulcaniza- Good Good 
tion 
Evaluation after indoor Good Good 
endurance test 
Degree of air leakage 2.7 1.6 
(%/month) 
Tire weight (Kg) 7.3 7.3 
(%) (92.4) (9.4) 
______________________________________ 
EXAMPLES 11 to 13 
The procedure of Example 5 was repeated with the exception of forming inner 
liners from the components shown in Table 7. Table 7 shows the visual 
evaluation of the obtained tire, visual evaluation of the tire after 
indoor endurance test, results of air leakage test, and measurements of 
the tire weight. 
TABLE 7 
______________________________________ 
Inner liner 
Example 11 Example 12 Example 13 
______________________________________ 
Layer (A) (gas 
Polyethylene 
Polyarylate ** 
Polyphenylene 
barrier layer) terephthalate ether-polyester 
Thickness = 36 .mu.m * (polybutylene 
terephthalate) 
alloy*** 
Layer (B) Ethylene-glyci- Ethylene-glyci- Ethylene-glyci- 
(adhesive layer) dyl methacry- dyl methacry- dyl methacry- 
Thickness = 30 .mu.m late-methyl late-methyl late-methyl 
acrylate acrylate acrylate 
terpolymer terpolymer terpolymer 
Electron beam Irradiated Irradiated Irradiated 
irradiation 
Evaluation after Good Good Good 
vulcanization 
Evaluation after Good Good Good 
indoor endurance 
test 
Degree of air 1.7 1.8 2.0 
leakage(%/month) 
Tire weight (Kg) 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) 
______________________________________ 
Note: 
* product of Kanebo Ltd. "PET PEFG13 
** product of Unitika Ltd. "UPolymer U8060 
***product of Mitsubishi Rayon Co., Ltd. "DIA.cndot.ALLOY TX70A 
EXAMPLES 14 to 16 and COMATIVE EXAMPLE 5 
Tires were produced in the same manner as in Example 5 except that the 
laminated films were produced by exposure to an electron beam in a dose of 
5 Mrad, 20 Mrad and 40 Mrad, respectively at an accelerating voltage of 
150 kV, 200 kV and 250 kV, respectively in Examples 14, 15 and 16, or 
without exposure to an electron beam in Comparative Example 5. Table 8 
below shows the visual evaluation of the obtained tire, visual evaluation 
of the tire after indoor endurance test, results of air leakage test, and 
measurements of the tire weight. 
TABLE 8 
______________________________________ 
Example Example Example Comp.Ex. 
14 15 16 
5 
______________________________________ 
Accelerating 
150 kV 200 kV 250 kV Non- 
voltage/ 5 Mrad 20 Mrad 40 Mrad irradi- 
Exposure dose ated 
Evaluation Good Good Good Impaired 
after * 
vulcanization 
Evaluation Good Good Good Un- 
after indoor evalu- 
endurance test ated** 
Degree of air 2.0 2.0 1.9 7.0 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) (92.4) 
______________________________________ 
Note: 
* = Melted and fractured 
** = The inner liner surface was impaired (unevaluated). 
As apparent from Table 8, the inner liners of the invention were kept from 
fracture due to the exposure to an electron beam. The resulting tires had 
inner liners excellent in the adhesion to the carcass layer. 
EXAMPLES 17 and 18 
Three-layer laminated films for a tire with a size of 185/65 R14 were 
prepared by co-extrusion so as to laminate adhesive layers (B) of 
ethylene-ethyl acrylate copolymer (100 parts by weight of copolymer used) 
containing 3 parts by weight of triallyl isocyanurate (TAIC) in the 
structure of FIG. 2 on both sides of a gas barrier layer (A) of nylon 66. 
The laminated films were irradiated at both sides with an electron beam 
under the conditions shown in Table 9. The thickness of the laminated 
films was 96 .mu.m ((B)/(A)/(B)=30/36/30 .mu.m). 
The laminated films thus obtained were used as inner liners. Unvulcanized 
tires with said inner liner laminated on the carcass layer 2 were 
vulcanized at 180.degree. C. for 10 minutes to heat-bond the adhesive 
layer (B) to the carcass layer 2, giving a finished tire. Table 9 shows 
the visual evaluation of the obtained tire, visual evaluation of the tire 
after indoor endurance test, results of air leakage test, and measurements 
of the tire weight. 
The rubber composition used for the carcass layer had the formulation as 
shown above in Table 4. The carcass layer had an array of polyester cords 
embedded in the rubber composition. 
TABLE 9 
______________________________________ 
Example 17 Example 18 
______________________________________ 
Layer (A) (gas 
Nylon 66 Nylon 66 
barrier layer) 
Thickness = 36 .mu.m 
Layer (B) Ethylene-ethyl Ethylene-ethyl 
(adhesive acrylate-maleic acrylate-maleic 
layer) anhydride anhydride 
Thickness = 30 .mu.m terpolymer/TAIC terpolymer/TAIC 
Accelerating 150 kV 150 kV 
voltage/Expo- 0.5 Mrad 3.0 Mrad 
sure dose 
Evaluation Good Good 
after 
vulcanization 
Evaluation Good Good 
after indoor 
endurance test 
Degree of air 1.9 1.9 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 
(%) (92.4) (92.4) 
______________________________________ 
As apparent from Table 9, because of TAIC incorporated in the adhesive 
layer (B), the inner liners of the invention were kept from fracture 
although exposed to only a small dose (0.5 Mrad) of an electron beam, and 
were imparted a high adhesion to the carcass layer. 
EXAMPLE 19 
Five-layer laminated films for a tire with a size of 185/65 R14 were formed 
by laminating, in the structure of FIG. 2, rubber-adhering layers (D) of 
ethylene-ethyl acrylate copolymer (EEA), adhesive layers (B) of 
ethylene-ethyl acrylate-maleic anhydride terpolymer (modified 
ethylene-acrylic acid copolymer) and a gas barrier layer (A) of nylon 66. 
The lamination was conducted as follows. A T-die was connected to 5 
extruders independently operable. Among the five extruders, the resin for 
the rubber-adhering layers (D) was supplied to two extruders, the resin 
for the adhesive layers (B) to two extruders, and the resin for the gas 
barrier layer (A) to the other extruder. After co-extrusion, the molten 
laminated 5 layers were quenched with a roll cooled with water, giving 
laminated films of 5 flat layers with a structure of (D)/(B)/(A)/(B)/(D). 
The thickness of the laminated films was 100 .mu.m 
((D)/(B)/(A)/(B)/(D)=30/2/36/2/30 .mu.m). Subsequently the laminated films 
were irradiated at both sides with an electron beam in a dose of 15 Mrad 
at an accelerating voltage of 200 kV, whereby the laminated films were 
crosslinked. 
The laminated films thus obtained were used as an inner liner. An 
unvulcanized tire with said inner liner laminated on the carcass layer 2 
was vulcanized at 180.degree. C. for 10 minutes to heat-bond the rubber 
layer (D) to the carcass layer 2, giving a finished tire. Table 10. below 
shows the visual evaluation of the obtained tire, visual evaluation of the 
tire after indoor endurance test, results of air leakage test, and 
measurements of the tire weight. 
TABLE 10 
______________________________________ 
Inner liner 
Example 19 Comp. Example 6 
Comp. Example 7 
______________________________________ 
Layer (D) EEA Nylon 6 EVA 
Thickness = 
30 .mu.m 
Layer (B) Ethylene-ethyl Nylon 6-66 LLDPE 
Thickness = acrylate-maleic 
2 .mu.m anhydride 
terpolymer 
Layer (A) Nylon 66 Nylon 66 Nylon 66 
Thickness = 
36 .mu.m 
Electron beam Irradiated Irradiated Irradiated 
irradiation 
Evaluation after Good Impaired* Good 
vulcanization 
Evaluation after Good Unevaluated** Imparied*** 
indoor endurance 
test 
Degree of air 2.0 1.5 2.6 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) 
______________________________________ 
Comp. Comp. Comp. 
Inner liner Example 8 Example 9 Example 10 
______________________________________ 
Layer (D) EVA PP Butyl rubber 
Thickness = (Thickness = 
30 .mu.m 500 .mu.m) 
Layer (B) Maleic Maleic 
Thickness = anhydride- anhydride- 
2 .mu.m modified EVA modified PP 
Layer (A) EVOH Nylon 6-10 
Thickness = 
36 .mu.m 
Electron beam Irradiated Non-irradiated Non-irradiated 
irradiation 
Evaluation after Good Impaired # Good 
vulcanization 
Evaluation after Impaired ## Unevaluated ### Good 
indoor endurance 
test 
Degree of gas 1.3 3.0 2.8 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.9 
(%) (92.4) (92.4) (100) 
______________________________________ 
Note: The abbreviations and emblems used in Table 10 represent: 
EVA: ethylenevinyl acetate copolymer. 
PP: polypropylene. 
LLDPE: linear lowdensity polyethylene. 
EVOH: ethylenevinyl alcohol copolymer. 
*The rubber layer (R) and the layer (D) were peeled. 
**The inner liner surface was impaired (unevaluated). 
***The layers (B) and (A) were peeled. 
# The film was foamed. 
## The film was fractured. 
### The inner liner surface was impaired (unevaluated). 
The rubber composition used for the carcass layer had the formulation as 
shown above in Table 4. The carcass layer had an array of polyester cords 
embedded in the rubber composition. 
COMATIVE EXAMPLES 6 to 8 
The procedure of Example 19 was repeated with the exception of forming 
inner liners from the components shown in Table 10. Table 10 shows the 
visual evaluation of the obtained tire, visual evaluation of the tire 
after indoor endurance test, results of air leakage test, and measurements 
of the tire weight. 
COMATIVE EXAMPLE 9 
A tire was produced by repeating the procedure of Example 19 with the 
exception of forming an inner liner from the components shown in Table 10 
without exposure to an electron beam. Table 10 shows the visual evaluation 
of the obtained tire, visual evaluation of the tire after indoor endurance 
tester results of air leakage test, and measurements of the tire weight. 
COMATIVE EXAMPLE 10 
A tire was produced by laminating on the inner periphery of a green tire, a 
500 .mu.m-thick inner liner of unvulcanized butyl rubber having the 
formulation shown in Table 5 so as to form an intermediate layer of tie 
gum about 700 .mu.m in thickness therebetween. The green tire was 
vulcanized under the same conditions as in Example 19. Table 10 shows the 
visual evaluation of the tire after vulcanization, visual evaluation of 
the tire after indoor endurance test, results of air leakage test, and 
measurements of the tire weight. 
As apparent from Table 10, no impairment was found in the inner liner of 
Example 19 after vulcanization and after indoor endurance. The inner liner 
of Example 19 was comparable or superior in the degree of air leakage to 
inner liners of butyl rubber. A 7.6% decrease of the tire weight was 
realized by a 1/5 reduction in the thickness of the inner liner of Example 
19. 
In the inner liners of Comparative Examples 6 to 8, at least one of the 
layers (D), (B) and (A) deviated from the scope of the invention. The 
inner liners were found unacceptable after indoor endurance test. Hence 
they were improper. 
The inner liner of Comparative Example 9, which met the structural 
requirements of the invention, caused bubbles because of non-exposure to 
an electron beam. The inner liner was evaluated as unacceptable after 
vulcanization. Namely it was improper. 
EXAMPLE 20 
A tire was produced in the same manner as in Example 19 except that the gas 
barrier layer (A) of the laminated films was composed of polyphenylene 
ether/polyamide (nylon 6) alloy ("ARTLEY Y 20S," product of Sumitomo 
Chemical Co., Ltd.). Table 11 shows the visual evaluation of the tire 
after vulcanization, visual evaluation of the tire after indoor endurance 
test, results of air leakage test, and measurements of the tire weight. 
EXAMPLES 21 to 23 
Tires were produced in the same manner as in Example 20 except that the gas 
barrier layer (A) of the laminated films was composed of polyethylene 
terephthalate, polyacrylate or polyphenylene ether/polyester (polybutylene 
terephthalate) alloy ("DIA.multidot.Alloy TX-70A," product of Mitsubishi 
Rayon Co., Ltd.), the rubber-adhering layer (D) was formed from an 
ethylene-methyl methacrylate copolymer (EMMA) and the adhesive layer (B) 
was made of low-density maleic anhydride-modified polyethylene. Table 11 
below shows the visual evaluation of the tire after vulcanization, visual 
evaluation of the tire after indoor endurance test, results of air leakage 
test, and measurements of the tire weight. 
TABLE 11 
__________________________________________________________________________ 
Inner liner 
Example 20 
Example 21 
Example 22 
Example 23 
__________________________________________________________________________ 
Layer (D) 
EEA EMMA EMMA EMMA 
thickness = 30 .mu.m 
Layer (B) Ethylene-ethyl Low-density Low-density Low-density 
thickness = 2 .mu.m acrylate-maleic maleic maleic maleic 
anhydride anhydride- anhydride- anhydride- 
terpolymer modified modified modified 
polyethylene polyethylene polyethylene 
Layer (A) Polyphenylene Polyethylene Polyacrylate Polyphenylene 
thickness = 36 .mu.m ether/polyamide 
terephthalate ether/polyester 
alloy alloy 
Electron beam Irradiated Irradiated Irradiated Irradiated 
irradiation 
Evaluation after Good Good Good Good 
irradiation 
Evaluation after Good Good Good Good 
indoor endurance 
test 
Degree of air 2.2 1.7 1.8 2.0 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) (92.4) 
__________________________________________________________________________ 
As apparent from Table 11, even when the gas barrier (A) of the laminated 
films in the tire was composed of polyphenylene ether/polyamide alloy, 
polyethylene terephthalate, polyacrylate or polyphenylene ether/polyester 
alloy, no impairment was found in the inner liners after vulcanization and 
after indoor endurance as in Example 19. The inner liners were comparable 
or superior in the degree of air leakage to the conventional inner liner 
of butyl rubber indicated in Comparative Example 6. A 7.6% decrease of the 
tire weight was achieved as a result of a 1/5 reduction in the thickness 
of the inner liner. 
EXAMPLES 24 and 25 
Tires were produced in the same manner as in Example 19 except that the gas 
barrier layers (A) of the laminated films used as the inner liners had the 
thicknesses indicated in Table 12. Table 12 shows the visual evaluation of 
the tire after vulcanization, visual evaluation of the tire after indoor 
endurance test, results of air leakage test, and measurements of the tire 
weight. 
COMATIVE EXAMPLE 11 
A tire was produced in the same manner as in Example 19 except that the gas 
barrier layer (A) of the laminated films used as the inner liner had the 
thickness indicated in Table 12. Table 12 shows the visual evaluation of 
the tire after vulcanization, visual evaluation of the tire after indoor 
endurance test, results of air leakage test, and measurements of the tire 
weight. 
TABLE 12 
______________________________________ 
Comparative 
Inner liner Example 24 Example 25 Example 11 
______________________________________ 
Thickness of 
3 .mu.m 50 .mu.m 2 .mu.m 
layer (A) 
Electron beam Irradiated Irradiated Irradiated 
irradiation 
Evaluation Good Good Good 
after 
vulcanization 
Evaluation Good Good Good 
after indoor 
endurance test 
Degree of air 2.7 1.7 2.9 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) 
______________________________________ 
As apparent from Table 12, when the gas barrier layer (A) of the laminated 
films was at least 3 .mu.m in thickness, there was provided a tire which 
was comparable or superior in the air pressure retentivity to tires with 
inner liners of butyl rubber. 
EXAMPLES 26 and 27 
Tires were produced in the same manner as in Example 19 except that the gas 
barrier layers (A) of the laminated films were composed of the 
polyphenylene ether/polyamide alloy used in Example 20 and the 
polyphenylene ether/polyester alloy used in Example 23, respectively and 
had the thicknesses indicated in Table 13. Table 13 shows the visual 
evaluation of the tire after vulcanization, visual evaluation of the tire 
after indoor endurance test, results of air leakage test, and measurements 
of the tire weight. 
TABLE 13 
______________________________________ 
Inner liner Example 26 Example 27 
______________________________________ 
Layer (A) Polyphenylene 
Polyphenylene 
ether/poly- ether/poly- 
amide alloy ester alloy 
Thickness of 3 .mu.m 3 .mu.m 
layer (A) 
Electron beam Irradiated Irradiated 
irradiation 
Evaluation Good Good 
after 
vulcanization 
Evaluation Good Good 
after indoor 
endurance test 
Degree of air 2.7 2.6 
leakage 
(%/month) 
Tire weight 
(Kg) 7.3 7.3 
(%) (92.4) (92.4) 
______________________________________ 
As apparent from Table 13, even when the gas barrier layers (A) of the 
laminated films were composed of polyphenylene ether/polyamide alloy and 
polyphenylene ether/polyester alloy, respectively, the resulting tires 
with the layers (A) of at least 3 .mu.m thickness were comparable or 
superior in the air pressure retentivity to the tire of Comparative 
Example 10 having the inner liner of butyl rubber, and were excellent in 
the heat resistance. 
EXAMPLES 28 to 30 
Five-layer laminated films for a tire with a size of 185/65 R14 were 
produced. The inner liners comprised rubber-adhering layers (D) of linear 
low-density polyethylene (LLDPE), adhesive layers (B) of linear 
low-density maleic anhydride-modified polyethylene (modified LLDPE), and a 
gas barrier layer (A) of nylon 66 in the structure as shown in FIG. 2. The 
lamination was conducted as follows. A T-die was connected to 5-extruders 
independently operable. Among the five extruders, the resin for the 
rubber-adhering layers (D) was supplied to two extruders, the resin for 
the adhesive layers (B) to two extruders, and the resin for the gas 
barrier layer (A) to the other extruder. After co-extrusion, the molten 
laminated 5 layers were quenched with a roll cooled with water, giving 
laminated films composed of 5 flat layers with a structure of 
(D)/(B)/(A)/(B)/(D). The thickness of the laminated films was 100 .mu.m 
((D)/(B)/(A)/(B)/(D)=30/2/36/2/30 .mu.m). Subsequently the laminated films 
were irradiated at both sides with an electron beam in a dose of 5, 20 and 
40 Mrad at an accelerating voltage of 150, 200 and 250 kV, respectively as 
shown in Table 14. Tires were produced by the same subsequent procedure as 
in Example 19. Table 14 below shows the visual evaluation of the tire 
after vulcanization, visual evaluation of the tire after indoor endurance 
test, results of air leakage test, and measurements of the tire weight. 
COMATIVE EXAMPLES 12 to 14 
Tires were produced in the same manner as in Examples 28 to 30 with the 
exception of difference in non-exposure or exposure to an electron beam in 
a dose of 4 or 45 Mrad at an accelerating voltage of 140 or 250 kV as 
shown in Table 14. Table 14 shows the visual evaluation of the tire after 
vulcanization, visual evaluation of the tire after indoor endurance test, 
results of air leakage test, and measurements of the tire weight. 
TABLE 14 
__________________________________________________________________________ 
Example 
Example 
Example 
Comp. Comp. 
Comp. 
28 29 30 Ex. 12 Ex. 13 Ex. 14 
__________________________________________________________________________ 
Accelerating voltage 
150 kV 
200 kV 
250 kV 
Non-irradiated 
140 kV 
250 kV 
Exposure dose 5 Mrad 20 Mrad 40 Mrad 4 Mrad 45 Mrad 
Evaluation after Good Good Good Impaired Impaired Good 
vulcanization (Melted & (Foamed 
broken) surface) 
Evaluation after Good Good Good Unevaluated* Good Impaired** 
indoor endurance 
test 
Degree of air 1.9 1.9 1.9 7.0 1.9 1.9 
leakage (%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) (92.4) (92.4) (92.4) 
__________________________________________________________________________ 
Note: *The inner liner surface was impaired (unevaluated). **The rubber 
layer and the layer (D) were peeled. 
As apparent from Table 14, the laminated films of Examples 28 to 30 were 
irradiated with an electron beam in a dose of 5 to 40 Mrad at an 
accelerating voltage of 150 to 250 kV, and thereby made free of fracture. 
The obtained tires were provided with the inner liners having an increased 
adhesion to the carcass layer. 
EXAMPLES 31 to 33 
Three different laminated films were produced in the same manner as in 
Examples 28 to 30 except that the gas barrier layer (A) of the laminated 
films was composed of polyphenylene ether/polyamide alloy. The laminated 
films were irradiated with an electron beam in a dose of 5, 20 and 40 Mrad 
at an accelerating voltage of 150, 200 and 250 kV, respectively. Using the 
laminated films, tires were produced by the same procedure as in Example 
19. Table 15 shows the visual evaluation of the tire after vulcanization, 
visual evaluation of the tire after indoor endurance test, results of air 
leakage test, and measurements of the tire weight. 
COMATIVE EXAMPLES 15 and 16 
Tires were produced in the same manner as in Examples 31 to 33 with the 
exception of difference in non-exposure or exposure to an electron beam in 
a dose of 100 Mrad at an accelerating voltage of 250 kV as shown in Table 
15. Table 15 shows the visual evaluation of the tire after vulcanization, 
visual evaluation of the tire after indoor endurance test, results of air 
leakage test, and measurements of the tire weight. 
TABLE 15 
__________________________________________________________________________ 
Example 
Example 
Example 
Comp. Comp. 
31 32 33 Ex. 15 Ex. 16 
__________________________________________________________________________ 
Accelerating 
150 kV 
200 kV 
250 kV 
Non-irradiated 
250 kV 
voltage/ 5 Mrad 20 Mrad 40 Mrad 100 Mrad 
Exposure dose 
Evaluation after Good Good Good Impaired* Good 
vulcanization 
Evaluation after Good Good Good Unevaluated** Impaired*** 
indoor endurance 
test 
Degree of air 2.1 2.1 2.1 7.0 1.9 
leakage (%/month) 
Tire weight 
(Kg) 7.3 7.3 7.3 7.3 7.3 
(%) (92.4) (92.4) (92.4) (92.4) (92.4) 
__________________________________________________________________________ 
Note: 
*The inner liner was melted and fractured. 
**The inner liner surface was impaired (unevaluated). 
***The rubber layer and the layer (D) were peeled. 
As apparent from Table 15, the inner liners formed of polyamide-based alloy 
according to the invention were kept from fracture due to the exposure to 
an electron beam in a dose of 40 Mrad or less. The inner liners were 
imparted an increased adhesion to the carcass layer. 
EXAMPLES 34 and 35 
5-layer laminated films for a tire with a size of 185/65 R14 were formed by 
laminating, in the structure of FIG. 2, rubber-adhering layers (D) of 
ethylene-ethyl acrylate copolymer (EEA) (100 parts by weight used) 
containing 3 parts by weight of triallyl isocyanurate (TAIC), adhesive 
layers (B) of ethylene-ethyl acrylate-maleic anhydride terpolymer (100 
parts by weight used) containing 3 parts by weight of TAIC and a gas 
barrier layer (A) of nylon 66. The lamination was conducted as follows. A 
T-die was connected to 5 extruders independently operable. Among the five 
extruders, the resin for the rubber-adhering layers (D) was supplied to 
two extruders, the resin for the adhesive layers (B) to two extruders, and 
the resin for the gas barrier layer (A) to the other extruder. After 
co-extrusion, the molten laminated 5 layers were quenched with a roll 
cooled with water, giving laminated films composed of 5 flat layers with a 
structure of (D)/(B)/(A)/(B)/(D). The thickness of the laminated films was 
100 .mu.m ((D)/(B)/(A)/(B)/(D)=30/2/36/2/30 .mu.m). Subsequently the 
laminated films were irradiated at both sides with an electron beam in the 
dose and at the accelerating voltage shown in Table 16. Tires were 
produced in the same manner as in Example 19. Table 16 below shows the 
visual evaluation of the obtained tire, visual evaluation of the tire 
after indoor endurance test, results of air leakage test, and measurements 
of the tire weight. 
TABLE 16 
______________________________________ 
Inner liner Example 34 Example 35 
______________________________________ 
Layer (D) EEA/TAIC EEA/TAIC 
(thickness = 30 .mu.m) 
Layer (B) Ethylene-ethyl Ethylene-ethyl 
(Thickness = 30 .mu.m) acrylate- acrylate- 
maleic maleic 
anhydride anhydride 
terpolymer/ terpolymer/ 
TAIC TAIC 
Layer (A) Nylon 66 Nylon 66 
(Thickness = 30 .mu.m) 
Accelerating 150 kV 150 kV 
voltage/Exposure 0.5 Mrad 3.0 Mrad 
dose 
Evaluation after Good Good 
vulcanization 
Evaluation after Good Good 
indoor endurance 
test 
Degree of air 1.9 1.9 
leakage (%/month) 
Tire weight 
(Kg) 7.3 7.3 
(%) (92.4) (92.4) 
______________________________________ 
As apparent from Table 16, because of TAIC incorporated in the 
rubber-adhering layers (D) and the adhesive layers (B), the inner liners 
of the invention were kept from fracture although exposed to only a small 
dose (0.5 Mrad) of an electron beam, and were imparted a high adhesion to 
the carcass layer.