JP3236247B2 - Elastomer composition and pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastomer composition having improved heat resistance while maintaining flexibility, and further relates to a pneumatic tire using this elastomer composition for a gas permeation preventing layer.

[0002]

2. Description of the Related Art A technique for irradiating a resin film with an electron beam to improve its heat resistance and strength is already common. However, when this technology is used dynamically as a laminate with rubber such as tires, the polymer becomes three-dimensional due to electron beam irradiation and its Young's modulus is increased, so that it lacks in durability and causes film cracks and the like. There was a problem that occurs.

In some cases, a thermoplastic elastomer composed of rubber and a thermoplastic resin is used for an inner liner of a tire (Japanese Patent Application No. 8-183683). In the case of thermoplastic elastomers that use a thermoplastic resin with a low melting point and a melting point below the tire vulcanizing temperature for the matrix, the inner surface of the tire will have poor appearance due to adhesion to the bladder, rubbing with the bladder, etc. is there.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has been studied to solve these problems, and as a result, while maintaining flexibility, an elastomer composition having excellent heat resistance and durability was obtained. In addition, when the elastomer composition is used as an air permeation-preventing layer of a pneumatic tire, while providing excellent flexibility, its heat resistance and durability are excellent, and a molded bladder is provided. An object of the present invention is to provide a use of the elastomer composition for an air permeation prevention layer in a pneumatic tire, which has no adhesion and therefore has a good surface finish.

[0005]

According to the present invention, a matrix is provided.
Beam crosslinked thermoplastic resin and dispersed phase constituting
The present invention provides an elastomer composition obtained by irradiating a thermoplastic elastomer composition containing an electron beam-disintegrating elastomer constituting the above with an electron beam.

Further, according to the present invention, there is provided a pneumatic tire using the elastomer composition for an air permeation preventing layer.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration, operation and effect of the present invention will be described below. As the electron beam crosslinkable thermoplastic resin to be blended in the elastomer composition according to the present invention, a thermoplastic resin having a property of crosslinking when irradiated with an electron beam can be used. A thermoplastic resin that crosslinks by irradiation, and then collapses when irradiated with an electron beam in the air. However, a resin having an acrylic group or an allyl group is used as a crosslinking aid (for example, triallyl isocyanurate (TAIC), When used as trimethylolpropane triacrylate, triallyl cyanurate, etc.), there are both types of thermoplastic resins which crosslink even when irradiated in air.

The former type of thermoplastic resin includes, for example, polyethylene, polystyrene, polyacrylate, polyacrylamide, polyvinyl chloride, polyvinyl acetate, polydimethylsiloxane, polyvinyl alcohol, polyvinylpyrrolidone and polyester. The latter type of thermoplastic resin includes, for example, polyamide, polyvinyl chloride and the like.

The thermoplastic resin blended as an electron beam crosslinkable thermoplastic resin component in the elastomer composition according to the present invention has an air permeability coefficient of 25 × 10 ⁻¹² cc · cm / cm ^2.
· Sec · cmHg or less, preferably 0.05 × 10 ^-12 to 1
Any of the above resins alone or in a mixture of 0 × 10 ⁻¹² cc · cm / cm ² · sec · cmHg can be used, and according to the present invention, the compounding amount is from 15 to 15 per the total weight of all polymer components. 80% by weight, more preferably 1 in terms of flexibility
5 to 60% by weight. If it exceeds 80% by weight, mixing is possible, but the resulting elastomer composition lacks flexibility, and if it is less than 15% by weight, it is insufficient to form a continuous phase containing a thermoplastic elastomer component. Therefore, the predetermined elastomer composition of the present invention cannot be formed.

Further, as the electron beam-disintegrating elastomer compounded in the elastomer composition according to the present invention, a so-called disintegrating rubber having a property of disintegrating upon irradiation with an electron beam can be used. For example, polyisobutylene rubber (IBR), epichlorohydrin rubber (CH
R), isobutylene-isoprene copolymer rubber (IIR)
And brominated paramethylstyrene-isobutylene copolymer (Br-IPMS).

The elastomer blended as an electron beam-disintegrating elastomer component in the elastomer composition according to the present invention may be any of the aforementioned rubbers alone or a mixture thereof. When,
It is 20 to 85% by weight, preferably 40 to 80% by weight, based on the total weight of all polymer components. If the amount is less than 20% by weight, the elastomer composition of the present invention is not sufficient to give the necessary flexibility, and if it exceeds 85% by weight, the amount of the thermoplastic resin component forming the continuous phase is not sufficient, It is not preferable because kneading and molding cannot be performed.

As the thermoplastic resin component to be incorporated in the elastomer composition according to the present invention, it is essential to use the above-mentioned electron beam crosslinkable thermoplastic resin.
An electron beam collapse type thermoplastic resin can be used in combination with this. However, even in that case, in the elastomer composition of the present invention, it is necessary that the matrix phase is composed of an electron beam crosslinkable thermoplastic resin. Under the kneading conditions, the following conditions are satisfied: α = (φ _d / φ _m ) × (η _m / η _d ) <1, where φ _d : volume fraction of the electron beam-degradable thermoplastic resin, φ _m : electron beam It is selected and used so as to satisfy the following: volume fraction of the crosslinked thermoplastic resin, η _d : melt viscosity of the electron beam collapse type thermoplastic resin, η _m : melt viscosity of the electron beam crosslinked thermoplastic resin.

[0013] Here, the melt viscosity means the melt viscosity of any temperature and component at the time of kneading, and the melt viscosity of each polymer material refers to the temperature, shear rate (sec ^-1 ) and shear stress. Because of the dependence, the stress and shear rate of the polymer material are generally measured at an arbitrary temperature in a molten state flowing through the thin tube, particularly at a temperature range during kneading, and the melt viscosity is measured by the following equation (1).

(Equation 1) In addition, a capillary rheometer (Capillograph 1C) manufactured by Toyo Seiki Co., Ltd. was used for measuring the melt viscosity. Further, in the present invention, the melt viscosity may not be a single component, and when two or more polymers are used, each polymer component may be melted at any kneading temperature as a constituent thermoplastic resin component. It can be calculated using a weighted average of the viscosities.

Examples of the electron beam collapse type thermoplastic resin include polypropylene, polyisobutylene, polyα-methylstyrene, polymethacrylate, polymethacrylamide, polymethacrylonitrile, polyvinylidene chloride, and polychlorinated trifluoride. Examples include ethylene and polytetrafluoroethylene.

Further, the elastomer composition according to the present invention comprises a thermoplastic resin having a functional group capable of reacting with the electron beam crosslinkable thermoplastic resin constituting the matrix phase (this resin is an electron beam crosslinkable thermoplastic resin). , Disintegration type) are also possible. For example, when the matrix resin is a polyamide, a thermoplastic resin having a maleic acid group, an epoxy group, and the like, and when the matrix resin is a polyacrylate resin, a thermoplastic resin having a hydroxyl group, an amide group is used. When the matrix resin is a polyvinyl chloride resin, a thermoplastic resin having an amide group is used. When a thermoplastic resin having such a reactive functional group is blended into the elastomer composition of the present invention and is reacted with the matrix resin material, the crystal structure of the matrix resin material is partially inhibited, whereby The flexibility in the elastomer composition of the present invention can be increased.

As the electron beam-disintegrating elastomer component to be blended in the elastomer composition according to the present invention, an electron beam crosslinkable elastomer can be used in combination. When a small amount of the electron beam crosslinkable elastomer is used in combination, the heat resistance and strength of the elastomer composition of the present invention after electron beam irradiation can be increased accordingly. Examples of such an electron beam crosslinkable elastomer include isoprene rubber (IR), natural rubber (NR), epoxidized natural rubber (ENR), and butadiene rubber (B
R), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene propylene terpolymer (EPDM), chloroprene rubber (CR), acrylic rubber (ACM), silicone rubber, fluorine rubber and chlorine Polyethylene (CPE)
and so on.

The elastomer composition of the present invention is obtained by kneading a compounded composition containing the above-mentioned predetermined electron beam crosslinkable thermoplastic resin component and an electron beam collapsible elastomer component, and adding an electron beam to the prepared thermoplastic elastomer composition. Irradiation.

Hereinafter, the method for producing the elastomer composition of the present invention will be described in detail. The method for producing an elastomer composition according to the present invention comprises a step of previously preparing an electron beam crosslinkable thermoplastic resin component and an electron beam collapsible elastomer component (unvulcanized product in the case of rubber), or these components and the above-mentioned other necessary components. Is melt-kneaded in a twin-screw kneading extruder or the like to disperse an electron beam collapsible elastomer or other compounding components in an electron beam crosslinkable thermoplastic resin forming a continuous phase. Here, when a thermoplastic resin having a functional group capable of reacting with the above-mentioned electron beam crosslinkable thermoplastic resin is compounded as another compounding component, this compounding component is used during the melt kneading. Reacts with the thermoplastic resin. When vulcanizing the electron beam collapsible elastomer, a vulcanizing agent may be added under kneading to dynamically vulcanize the electron beam collapsible elastomer. Various compounding agents (excluding vulcanizing agents) for electron beam crosslinkable thermoplastic resin or electron beam collapsible elastomer
May be added during the kneading, but it is preferable to mix them before kneading. The kneading machine used for kneading the electron beam crosslinkable thermoplastic resin component and the electron beam collapsible elastomer component, or these components and required compounding components is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, A shaft kneading extruder and the like can be mentioned. Among them, it is preferable to use a twin-screw kneading extruder from the viewpoint of dispersibility. Further, two or more types of kneaders may be used to knead sequentially. As the conditions for the melt-kneading, the temperature may be at least the temperature at which the electron beam crosslinkable thermoplastic resin melts. The shear rate during kneading is preferably from 500 to 7,500 sec ^-1 . The whole kneading time is 30 seconds to 10 minutes,
When a vulcanizing agent is added, the vulcanization time after the addition is 1
It is preferably from 5 seconds to 5 minutes.

The vulcanizing agent, vulcanization aid and vulcanization conditions (temperature and time) used for vulcanizing the electron beam collapsible elastomer of the present invention are appropriately determined according to the composition of the electron beam collapsible elastomer to be blended. There is no particular limitation as long as it is determined. As the vulcanizing agent, a general rubber vulcanizing agent (crosslinking agent) can be used. Specifically, examples of the sulfur vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide, and the like. 5-4 phr (Elastomer component (polymer) 1
About 100 parts by weight).

The organic peroxide-based vulcanizing agents include:
Benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide,
Examples thereof include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 2,5-dimethylhexane-2,5-di (peroxylbenzoate).
About 1 to 15 phr may be used. Further, examples of the phenolic resin-based vulcanizing agent include brominated alkylphenol resins and mixed cross-linking systems containing a halogen donor such as tin chloride or chloroprene and an alkylphenol resin. Good.

Others include zinc white (about 5 phr), magnesium oxide (about 4 phr), litharge (10 to 20 phr).
phr), p-quinonedioxime, p-dibenzoylquinonedioxime, tetrachloro-p-benzoquinone,
Poly-p-dinitrosobenzene (about 2 to 10 phr),
Methylene dianiline (about 0.2 to 10 phr) is exemplified.

[0022] If necessary, a vulcanization accelerator may be added. Examples of the vulcanization accelerator include general vulcanization accelerators such as aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram, dithioate, and thiourea, for example, 0.5 to 2 phr. The degree may be used.

Specifically, hexamethylenetetramine or the like is used as the aldehyde / ammonia vulcanization accelerator; diphenylguanidine is used as the guanidine vulcanization accelerator; dibenzothia is used as the thiazole vulcanization accelerator. Zirdisulphide (DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt, and the like; sulfenamide vulcanization accelerators include cyclohexylbenzothiazylsulfenamide (CBS);
N-oxydiethylenebenzothiazyl-2-sulfenamide, Nt-butyl-2-benzothiazolesulfenamide, 2- (thymolpolynyldithio) benzothiazole and the like; , Tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetramethylthiuram monosulfide (TMTM), dipentamethylenethiuram tetrasulfide, etc .; Zn-
Thiourea such as diethyldithiocarbamate, Zn-di-n-butyldithiocarbamate, Zn-ethylphenyldithiocarbamate, Tc-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecoline pipecolyldithiocarbamate and the like; Examples of the vulcanization accelerator include ethylenethiourea, diethylthiourea and the like;
As a vulcanization accelerator, a general rubber auxiliary agent can be used in combination, for example, zinc white (about 5 phr),
Stearic acid and oleic acid and their Zn salts (2 to 2)
(About 4 phr) may be used.

When the specific electron beam crosslinkable thermoplastic resin and the electron beam collapsible elastomer have different chemical compatibility, it is preferable to compatibilize both using a suitable compatibilizer as the third component. . By mixing a compatibilizer with the system, the interfacial tension between the electron beam crosslinkable thermoplastic resin and the electron beam collapsible elastomer is reduced, and as a result, the electron beam collapsible elastomer (rubber) forming the dispersed phase Since the particle diameter becomes fine, the characteristics of both components are more effectively expressed. As such a compatibilizer, generally, an electron beam crosslinkable thermoplastic resin component, a copolymer having both or one of the structures of an electron beam collapsible elastomer component, or an electron beam crosslinkable thermoplastic resin or electron beam The copolymer may have a structure having an epoxy group, a carboxyl group, a carbonyl group, a halogen group, an amino group, an oxazoline group, a hydroxyl group and the like which can react with the disintegrating elastomer. These may be selected according to the type of the electron beam crosslinkable thermoplastic resin and the electron beam collapsible elastomer to be mixed, and those usually used include a styrene-ethylene-butylene-styrene block copolymer (SEBS). )
And modified maleic acid thereof, EPDM, EPM and modified maleic acid thereof, EPDM / styrene or EPD
M / acrylonitrile graft copolymer and its maleic acid-modified product, styrene / maleic acid copolymer, reactive phenoxine and the like. The amount of the compatibilizer is not particularly limited, but is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the polymer component (total of the electron beam crosslinkable thermoplastic resin and the electron beam disintegrating elastomer). Is good.

Further, the thermoplastic elastomer composition according to the present invention comprising an electron beam crosslinkable thermoplastic resin before electron beam irradiation and an electron beam collapsible elastomer is used for improving the dispersibility and heat resistance of the elastomer, and the like. In general, reinforcing agents, fillers, softeners, plasticizers, which are blended with elastomers,
Compounding agents such as anti-aging agents, processing aids, and coloring materials can also be arbitrarily added in required amounts.

Next, the thermoplastic elastomer containing the electron beam crosslinkable thermoplastic resin and the electron beam collapsible elastomer produced by the above method is subjected to T-die extrusion molding, inflation molding, or calender molding of ordinary thermoplastic resin. Filmed. The thin film thus obtained has a structure in which the elastomer component is dispersed as a discontinuous phase at a high electron beam collapse type elastomer ratio in the matrix of the electron beam crosslinkable thermoplastic resin.

According to the present invention, an electron beam-crosslinkable thermoplastic resin and an electron beam-disintegrating elastomer formed into a film by the above-described method, or a thermosetting resin containing these and other compounding components, and further necessary various additives are compounded. The required electron beam is irradiated to the plastic elastomer composition. When the film is irradiated with an electron beam, the electron beam crosslinked type thermoplastic resin component forming the matrix phase starts to crosslink, and conversely, the electron beam disintegrating type elastomer component forming the dispersed phase degrades. As a result, since the matrix phase has a three-dimensional structure, it does not flow and the heat resistance is improved. On the other hand, as the matrix becomes three-dimensional and the rigidity of the matrix increases,
Since the elastomer in the dispersed phase collapses and softens, the flexibility and low Young's modulus of the entire elastomer composition are maintained.

The electron beam is irradiated from at least one surface of the film at an acceleration voltage of, for example, 150 kV or more, preferably 150 to 250 kV, more preferably 200 to 250 kV, and the irradiation amount is 2 Mrad or more and 40 Mrad or less.
Preferably, the irradiation is performed so as to be in the range of 5 to 15 Mrad. For this electron beam irradiation, a technique of adding an electron beam cross-linking auxiliary agent such as triallyl isocyanurate, triallyl cyanurate, or trimethylolpropane trimethacrylate to the film layer can be used in combination. Is not particularly limited, but is preferably about 1 to 5 parts by weight per 100 parts by weight of the electron beam crosslinked thermoplastic resin constituting the film layer. When the electron beam cross-linking assistant is used in this manner, the amount of electron beam irradiation can be reduced. The irradiation amount at that time is 2 Mrad
Or less, preferably 40 Mrad or less, preferably 0.1 to 40 Mrad, more preferably 1 to 20 Mrad.
Irradiation is preferably performed so as to be in the range of d. If the acceleration voltage is less than 150 kV, the dose does not tend to be uniform from the front surface to the back surface, which is not preferable. If the irradiation amount exceeds 40 Mrad, the adhesion of the film to the rubber layer tends to decrease, which is not preferable.

The elastomer composition of the present invention obtained as described above has flexibility (Young's modulus of 500 MPa or less).
With good durability and air permeation resistance (air permeability 25 × 10 ^-12 cc · cm / cm ² · sec · cmHg or less)
And has heat resistance that does not flow even when heated.

Hereinafter, a pneumatic tire having an air permeation preventing layer manufactured using the elastomer composition of the present invention will be described. The air permeation prevention layer of the pneumatic tire according to the present invention can be arranged at an arbitrary position inside the tire, that is, inside or outside the carcass layer, or at another position. In short, the object of the present invention is achieved by arranging the tire so as to prevent transmission and diffusion of air from the inside of the tire and maintain the air pressure inside the tire for a long period of time.

FIG. 1 is a half sectional view in the meridian direction illustrating a typical example of the arrangement of the air permeation preventing layer of a pneumatic tire.
In FIG. 1, a carcass layer 2 is mounted between a pair of left and right bead cores 1, 1, and an inner liner layer 3 is provided on the inner surface of the tire inside the carcass layer 2. In the present invention, the inner liner layer 3 is composed of the polymer composition for a tire. In FIG. 1, reference numeral 4 denotes a sidewall.

When the elastomer composition of the present invention is used as an air permeation preventing layer of a tire, the air permeation coefficient is 25 ×.
10 ^-12 cc · cm / cm ² · sec · cmHg or less, preferably 5
× 10 ⁻¹² cc · cm / cm ² · sec · cmHg or less. Although there is no particular lower limit for the air permeability coefficient, it is practically 0.05 × 10
^-12 cc · cm / cm ² · sec · cmHg. 2 air permeation
The thickness of the air permeation preventing layer can be reduced to half or less of the thickness of the conventional air permeation preventing layer by controlling the pressure to 5 × 10 ⁻¹² cc · cm / cm ² · sec · cmHg or less.

On the other hand, the Young's modulus is 500 MPa or less, preferably 10 to 300 MPa, and the thickness is 0.02 to 1.0 m.
m, preferably 0.05 to 0.5 mm. If the Young's modulus exceeds 500 MPa, it is not preferable because it cannot follow the deformation of the tire during running.

In the production of a pneumatic tire having an air permeation preventing layer comprising a thin film of the elastomer composition according to the present invention, an example in which the inner liner layer is disposed inside the carcass layer will be described. Extruded into a thin film of a predetermined width and thickness, and irradiated with an electron beam having a predetermined acceleration voltage and an irradiation amount, and then formed into a cylinder on a tire molding drum. Stick it on. Members used for normal tire production, such as a carcass layer, a belt layer, a tread layer, and the like made of unvulcanized rubber are sequentially laminated thereon, and the drum is pulled out to obtain a green tire. Next, the desired pneumatic tire can be manufactured by heating and vulcanizing the green tire according to a conventional method. In addition, also when providing an air permeation prevention layer on the outer peripheral surface of a carcass layer, it can be performed according to this.

[0035]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to the following Examples.

The following commercially available products were used for the components used in the following Examples and Comparative Examples. Thermoplastic resin component Nylon 11: Rilsan BMNO (Atochem) ... Electron beam crosslinked nylon 6-66 copolymer: Amilan CM6001 (Toray) ... Electron beam crosslinked polypropylene / polyethylene copolymer: PER · M5
52E (Tokuyama): Electron beam-disintegrating maleic acid-modified EEA: Nisseki N-polymer A1600 (Nippon Petrochemical): Electron beam cross-linking epoxy-modified EMA: Bond First 7L (Sumitomo Chemical): Electron beam cross-linking elastomer component Br-IPMS : EXXPRO 98-4 (manufactured by Exxon Chemical) ... electron beam decay type HNBR: Zetpol 1020 (manufactured by Nippon Zeon) ...
Electron beam decay type ENR: 50% Epoxidized Natura
l Rubber (manufactured by Malaya): vulcanization component of electron beam crosslinkable elastomer component Zinc flower: Zinc flower No. 3 (manufactured by Seido Chemical) Zinc stearate: (manufactured by Seido Chemical) Stearic acid: bead stearic acid NY (Japan) TT: Noxeller TT (Ouchi Shinko Chemical Co., Ltd.) M: Nocceller M (Ouchi Shinko Chemical Co., Ltd.) S: Powdered sulfur (Karuizawa Refinery) Crosslinking aid for thermoplastic resin TAIC: Parkerlink 301-70DPD ( Akzo Chemical)

The components of the current butyl rubber used in Comparative Example 3 are as follows. Brominated butyl rubber: Exxon bromobutyl 224
4 Exon Chemical Co., Ltd. FEF carbon black: HTC100 Chubu Carbon Co., Ltd. Stearic acid: Lunac YA Kao Co., Ltd. Zinc oxide: Ginrei zinc flower Toho Zinc Co., Ltd.
Sulfur: Powdered sulfur Karuizawa Refining Co., Ltd. Vulcanization accelerator (NS): Noxeller NS-P Ouchi Shinko Chemical Co., Ltd. Aroma oil: Coumolex 300 Nippon Oil Co., Ltd.

Preparation of Samples Pellets of a given thermoplastic resin component as a matrix resin component shown in Table I below, or Examples 6 to 1
In the case of Comparative Example 0 and Comparative Example 4, the pellets and the pellets of the other predetermined thermoplastic resin component were charged from a first input port of a twin-screw kneading extruder, melt-kneaded, and then supplied from a second input port. The pellets of the elastomer component are charged and kneaded, and the elastomer component in the matrix resin composition, or after finely dispersing this component and other thermoplastic resin components,
The vulcanization-type compounding agents shown in Table I were introduced from the third introduction port,
The elastomer component was dynamically crosslinked (vulcanized) to fix the dispersion of the elastomer phase. Finally, a crosslinking aid of a thermoplastic resin is introduced from the fourth inlet, and the obtained thermoplastic elastomer composition is extruded into a strand shape from the outlet of a twin-screw kneading extruder. And pelletized with a pelletizer. Next, this pellet is
Thickness of 1 using a resin single screw extruder equipped with a die head
After forming into a 50 μm film, the film was irradiated with a predetermined electron beam, and the film was subjected to tests for Young's modulus and air permeability coefficient. However, in Comparative Examples 1 and 3, electron beam irradiation was not performed.

Further, the electron beam obtained above was irradiated with 1
A film having a thickness of 50 μm was used (however, electron beams were not irradiated in Comparative Examples 1 and 3), wound around a tire molding drum, and a carcass and a side coated with a rubber of the following formula (I) thereon Tire members such as a belt and a tread were laminated and inflated to obtain a green tire. The green tire was vulcanized with a vulcanizer at 180 ° C. for 10 minutes to finish the tire with a tire size of 165SR13 as shown in FIG.

Composition of rubber composition (I) Ingredients: parts by weight Commercial product (production company) Natural rubber 80 SIR-20 SBR 20 Nippol 1502 (manufactured by Zeon Corporation) FEF carbon black 50 HCT # 100 (manufactured by Chubu Carbon Co.) 2 Bead stearic acid NY (manufactured by NOF CORPORATION) ZnO 3 No. 3 zinc white sulfur 3 Powder sulfur (Karuizawa Refinery) Vulcanization accelerator 1 Nt-butyl-2-benzothiazylsulfenamide aroma oil 2 desorex 3 ( (Showa Shell Sekiyu Kabushiki Kaisha) Then, using this tire, a tire internal appearance, air leak performance and durability tests were performed.

The measuring method used in the following examples,
The evaluation method is as follows. Measurement method of Young's modulus of film According to JIS K6251 “Tensile test method for vulcanized rubber”. Test piece: The film sample prepared in each example was punched out with a JIS No. 3 dumbbell in parallel with the resin extrusion direction at the time of film extrusion molding. A tangent line was drawn on the curve in the initial strain region of the obtained stress to strain curve, and the Young's modulus was determined from the slope of the tangent line.

Measurement Method of Air Permeability Coefficient of Film According to JIS K7126 “Test Method for Gas Permeability of Plastic Films and Sheets (Method A)”. Test piece: The film sample prepared in each example was used. Test gas: air (N ₂ : O ₂ = 8: 2) Test temperature: 30 ° C

In the case of a tire having a low heat resistance inside appearance, the film is partially taken on a vulcanized bladder after vulcanization of the tire, or the surface layer is broken, and the film is transformed into a rough shape. Such a thing is regarded as reject (x). In addition, those that do not affect the tire performance but decrease the commerciality are indicated by “△”. Those without any abnormalities are judged as acceptable (O).

Tire Air Leakage Performance Test Method 165SR13 Steel Radial Tire (Rim 13 × 4
Using 1 / 2-J), the pressure was measured every 4 days at an interval of 4 days at an initial pressure of 200 kPa under no load conditions at room temperature of 21 ° C. for 3 months. Measured pressure P _t, the initial pressure P _o and the number of days elapsed t, function: to return to _{P t / P o = exp (} -αt) obtaining the α value. Using the obtained α, t = 30
Into the following equation to obtain β = [1-exp (−αt)] × 100 β value. This β value is calculated as the pressure drop rate per month (% /
Month).

Durability test method for inner liner layer 165SR13 steel radial tire (rim 13 × 4
1 / 2-J) and the air pressure is 200 kPa,
Attached to a 1500cc class passenger car, it applies a load equivalent to 4 passengers (65kg / person) and travels 20,000km on an actual road.
After running, the tire is removed from the rim and the liner layer on the inner surface of the tire is visually observed. If the liner layer has cracks, visible wrinkles, or peeling / lifting of the liner layer, it is judged as rejected (x), and if not, it is judged as passed (o).

The results of Examples 1 to 10 and Comparative Examples 1 to 4 are shown in Table I.

[0047]

[Table 1]

[0048]

[Table 2]

From the results shown in Table I, those of Examples 1 to 10 comprising the elastomer compositions satisfying the requirements of the present invention do not have a high Young's modulus (flexibility) and a good internal appearance of the tire ( (Excellent in heat resistance), as well as other air permeability coefficients, air leakage performance and durability. On the other hand, as shown in Comparative Example 1, even if the thermoplastic elastomer composition had the same composition as that of Example 1, the thermoplastic resin component was not irradiated with a predetermined electron beam. It can be seen that the inner liner layer flows and the inner liner layer melts and sticks inside the tire. As a result, the appearance inside the tire and the air leakage performance are extremely poor. When both the thermoplastic resin component and the elastomer component are electron beam cross-linkable as in Comparative Example 2, when the thermoplastic elastomer composition is irradiated with an electron beam, the cross-linking of these two components occurs. As a result, the Young's modulus becomes too high (it becomes rigid) and the durability is poor. Comparative Example 4
If the electron beam collapsible thermoplastic resin is too much blended in the thermoplastic resin component, the required electron beam crosslinkable thermoplastic resin cannot form a matrix phase, so the inner liner layer is formed inside the tire. It can be seen that the peeling-off of the tire occurs, and the internal appearance of the tire and the air leakage performance are extremely poor. Further, when comparing Example 1 and Example 5, a difference occurs in the internal appearance of the tire due to the magnitude of the amount of electron beam irradiation, and therefore, the degree of crosslinking of the thermoplastic elastomer component depends on the amount of electron beam irradiation. It can be seen that the amount is affected. In the case of using the currently used butyl rubber system of Comparative Example 3, the Young's modulus is too small and the air permeability coefficient is large, and even in comparison with this, the thing of the present invention is well balanced in terms of these characteristics. It turns out that it is excellent.

[0050]

As described above, according to the present invention,
An elastomer composition having excellent heat resistance and durability can be obtained while maintaining flexibility, and by using this for the inner liner layer of a pneumatic tire, a tire having excellent performance is provided.

[Brief description of the drawings]

FIG. 1 is a meridional section showing the structure of a pneumatic tire using an elastomer composition of the present invention for an inner liner layer (air permeation preventing layer).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bead core 2: Carcass layer 3: Inner liner layer 4: Side wall

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-54-113637 (JP, A) JP-A-52-101277 (JP, A) JP-A-55-164234 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08L 21/00 C08L 101/00 B60C 5/14

Claims (6)

(57) [Claims] An elastomer composition obtained by subjecting a thermoplastic elastomer composition containing an electron beam crosslinkable thermoplastic resin constituting a matrix phase and an electron beam collapsible elastomer constituting a dispersed phase to electron beam irradiation. 2. The thermoplastic elastomer composition further comprises an electron beam collapsible thermoplastic resin and / or an electron beam crosslinked elastomer, and these resins to be blended are heat-resistant.
The following conditions under kneading conditions during the production of the thermoplastic elastomer: α = (φ _d / φ _m ) × (η _m / η _d ) <1, where φ _{d is} the volume fraction φ _{m of the} electron beam-disintegrating thermoplastic resin. : Volume fraction of electron beam crosslinked thermoplastic resin η _d : Melt viscosity of electron beam collapse type thermoplastic resin η _m : Selected so as to satisfy the melt viscosity of electron beam crosslinked thermoplastic resin. 2. The elastomer composition according to 1. 3. The elastomeric composition of claim 1 comprising a thermoplastic resin having a functional group capable of reacting to the electron beam cross-linked thermoplastic resin constituting the matrix phase. 4. A pneumatic tire a film of elastomeric composition according an air barrier layer in any one of claims 1-3. 5. The physical properties of a film made of the elastomer composition after the electron beam irradiation have a Young's modulus of 500 MPa or less and an air permeability of 25 × 10 ⁻¹² cc · cm / cm ² · sec · cmHg.
The pneumatic tire according to claim 4 , which is: 6. The energy of the electron beam irradiation is 2 Mr.
The pneumatic tire according to claim 4, wherein the tire is at least ad.