TIRE INNER LINER AND PNEUMATIC TIRE

1 . A tire inner liner formed using a cylindrical film that comprises a thermoplastic material and is obtained by inflation molding,

wherein a ratio of breaking strength in a tire width direction to breaking strength in a tire circumferential direction of the cylindrical film is from 1.35 to 1.80.

2 . The tire inner liner according to claim 1 ,

wherein the tire inner liner is obtained by the inflation molding with a blow ratio of from 1.2 to 1.8.

3 . The tire inner liner according to claim 1 ,

wherein the cylindrical film is formed of a continuous phase of a thermoplastic elastomer and a dispersed phase of a rubber.

4 . The tire inner liner according to claim 3 ,

wherein the thermoplastic elastomer comprises a hard segment comprising polybutylene terephthalate and a soft segment comprising aliphatic polycarbonate.

5 . The tire inner liner according to claim 4 ,

wherein the hard segment comprises an isophthalic acid copolymerized polybutylene terephthalate.

6 . The tire inner liner according to claim 3 ,

wherein the cylindrical film is formed by melting and kneading the thermoplastic elastomer and the rubber with a crosslinking agent so that the rubber is dynamically crosslinked by the crosslinking agent.

7 . A pneumatic tire comprising:

the tire inner liner according to claim 1 .

8 . The pneumatic tire according to claim 7 ,

wherein the tire inner liner is arranged so that an orientation direction as an extrusion direction of the cylindrical film is parallel to the tire width direction in a tread portion and is parallel to a tire radial direction in a sidewall portion.

9 . A method of manufacturing a pneumatic tire, comprising:

extruding and molding a cylindrical film in which a ratio of breaking strength in an extrusion direction to breaking strength in a direction perpendicular to the extrusion direction is from 1.35 to 1.80 by inflation molding using a thermoplastic material;

forming a green tire by placing the obtained cylindrical film on a forming drum so that the extrusion direction becomes a tire width direction; and

vulcanizing and molding the green tire.

10 . The method of manufacturing the pneumatic tire according to claim 9 ,

wherein a blow ratio is set to from 1.2 to 1.8 when the cylindrical film is formed by the inflation molding.

11 . The method of manufacturing the pneumatic tire according to claim 9 ,

wherein a taking-up speed of the cylindrical film extruded from an extruder at the time of the inflation molding is set to from 1 to 10 m/minute.

12 . The method of manufacturing the pneumatic tire according to claim 9 ,

wherein a thermoplastic elastomer and a rubber are melted and kneaded with a crosslinking agent, and the rubber is dynamically crosslinked by the crosslinking agent to obtain the thermoplastic material including the thermoplastic elastomer as a continuous phase and the rubber as a dispersed phase.