Thermoplastic resin composition and tire using same

Abstract

Provided is a thermoplastic resin composition for the inner liner of pneumatic tires, which has low air permeability and a small percent change in air permeability from fatigue. A thermoplastic resin composition obtained by dispersing a modified rubber having an acid anhydride group or an epoxy group into a polyamide resin and an ethylene vinyl alcohol copolymer, the thermoplastic resin composition being characterized in that the ratio of the polyamide resin to the ethylene vinyl alcohol copolymer is between 47/53 and 61/39. The percent change in air permeability of the thermoplastic resin composition in the present invention when subjected 1 million times to 20% elongation strain at room temperature is 1.30 times or more. Additionally, a pneumatic tire using a film comprising the thermoplastic resin composition in the present invention as an inner liner has a percent change in air leakage of 1.30 times or less at room temperature after going 70,000 km.

Claims

1. A thermoplastic resin composition comprising a matrix phase which comprises a polyamide resin, wherein the polyamide is not modified with a plasticizer and an ethylene-vinyl alcohol copolymer, and a rubber modified with an acid anhydride group or an epoxy group dispersed in the matrix phase comprising the polyamide resin and the ethylene-vinyl alcohol copolymer, wherein the blending ratio between the polyamide resin and the ethylene-vinyl alcohol copolymer is from 47/53 to 61/39, wherein the composition does not contain a plasticizer.

2. The thermoplastic resin composition according to claim 1, wherein the polyamide resin is at least one selected from the group consisting of nylon 6, nylon 66 and nylon 6/66.

3. The thermoplastic resin composition according to claim 2, wherein the rubber modified with an acid anhydride group or an epoxy group is an ethylene--olefin copolymer having an acid anhydride group or an epoxy group, or an ethylene-acrylic acid copolymer having an acid anhydride group or an epoxy group, an ethylene-methacrylic acid copolymer having an acid anhydride group or an epoxy group, an ethylene-methyl acrylate copolymer having an acid anhydride group or an epoxy group, an ethylene-methyl methacrylate copolymer having an acid anhydride group or an epoxy group.

4. The thermoplastic resin composition according to claim 2, wherein the content of the rubber modified with an acid anhydride group or an epoxy group is from 70 to 280 parts by weight based on 100 parts by weight of the total amount of the polyamide resin and the ethylene-vinyl alcohol copolymer.

5. The thermoplastic resin composition according to claim 2, wherein the change in air permeability when a 20% elongation strain is repeatedly applied 1,000,000 times at room temperature is 1.30 times or less.

6. The thermoplastic resin composition according to claim 2, wherein the air permeability after repeatedly applying a 20% elongation strain 1,000,000 times at room temperature is 1010.sup.12 cc.Math.cm/cm.sup.2.Math.sec.Math.cmHg or less.

7. The thermoplastic resin composition according to claim 1, wherein the rubber modified with an acid anhydride group or an epoxy group is an ethylene--olefin copolymer having an acid anhydride group or an epoxy group, or an ethylene-acrylic acid copolymer having an acid anhydride group or an epoxy group, an ethylene-methacrylic acid copolymer having an acid anhydride group or an epoxy group, an ethylene-methyl acrylate copolymer having an acid anhydride group or an epoxy group, or an ethylene-methyl methacrylate copolymer having an acid anhydride group or an epoxy group.

8. The thermoplastic resin composition according to claim 7, wherein the content of the rubber modified with an acid anhydride group or an epoxy group is from 70 to 280 parts by weight based on 100 parts by weight of the total amount of the polyamide resin and the ethylene-vinyl alcohol copolymer.

9. The thermoplastic resin composition according to claim 7, wherein the change in air permeability when a 20% elongation strain is repeatedly applied 1,000,000 times at room temperature is 1.30 times or less.

10. The thermoplastic resin composition according to claim 7, wherein the air permeability after repeatedly applying a 20% elongation strain 1,000,000 times at room temperature is 1010.sup.12 cc.Math.cm/cm.sup.2.Math.sec.Math.cmHg or less.

11. The thermoplastic resin composition according to claim 1, wherein the content of the rubber modified with an acid anhydride group or an epoxy group is from 70 to 280 parts by weight based on 100 parts by weight of the total amount of the polyamide resin and the ethylene-vinyl alcohol copolymer.

12. The thermoplastic resin composition according to claim 11, wherein the change in air permeability when a 20% elongation strain is repeatedly applied 1,000,000 times at room temperature is 1.30 times or less.

13. The thermoplastic resin composition according to claim 11, wherein the air permeability after repeatedly applying a 20% elongation strain 1,000,000 times at room temperature is 1010.sup.12 cc.Math.cm/cm.sup.2.Math.sec.Math.cmHg or less.

14. The thermoplastic resin composition according to claim 1, wherein the change in air permeability when a 20% elongation strain is repeatedly applied 1,000,000 times at room temperature is 1.30 times or less.

15. The thermoplastic resin composition according to claim 1, wherein the air permeability after repeatedly applying a 20% elongation strain 1,000,000 times at room temperature is 1010.sup.12 cc.Math.cm/cm.sup.2.Math.sec.Math.cmHg or less.

16. The thermoplastic resin composition according to claim 1, wherein the polyamide resin is a modified polyamide resin obtained by melt-blending a polyamide resin and a compound capable of reacting with a terminal amino group of the polyamide resin, said compound being other than said rubber modified with an acid anhydride group or an epoxy group.

17. The thermoplastic resin composition according to claim 16, wherein the compound capable of reacting with a terminal amino group of the polyamide resin has one group being reactive with said terminal amino group and is a monofunctional epoxy compound.

18. A pneumatic tire comprising, as an inner liner, a film comprising the thermoplastic resin composition according to claim 1.

19. The pneumatic tire according to claim 18, wherein the change in air leakage after 70,000 km indoor running is 1.30 times or less.

20. The pneumatic tire according to claim 18, wherein the air leakage after 70,000 km indoor running is 1.5% or less.

Description

EXAMPLES

(1) Raw Materials

(1) The raw materials used in Examples and Comparative Examples are as follows.

(2) As the polyamide resin, nylon 6/66, UBE Nylon 5033B, produced by Ube Industries, Ltd. was used.

(3) As the ethylene-vinyl alcohol copolymer (simply referred to as EVOH), Soanol H4412B produced by Nippon Synthetic Chemical Industry Co., Ltd. was used.

(4) As the modified rubber, a maleic anhydride-modified ethylene-butene copolymer (TAFMER MH-7020 produced by Mitsui Chemicals, Inc.) was used.

(5) As the compound capable of combining with a terminal amino group of the polyamide resin, p-sec-butylphenyl glycidyl ether (Epiol SB produced by NOF Corporation) was used.

(2) Preparation of Thermoplastic Resin Composition

(6) The polyamide resin, the ethylene-vinyl alcohol copolymer and the modified rubber were charged into a twin-screw kneader in the weight ratio shown in Tables 1 and 2 and melt-kneaded at a kneader temperature of 230 C., and the mixture was continuously extruded into strands from the extruder, then cooled with water and cut by a cutter to prepare a pellet-like thermoplastic resin composition.

(7) Also, 100.0 parts by weight of the polyamide resin and 2.0 parts by weight of p-sec-butylphenyl glycidyl ether were charged into a twin-screw kneader (TEX44 manufactured by Japan Steel Works, Ltd.) and melt-kneaded at a kneader temperature of 230 C. to prepare a modified polyamide resin. The modified polyamide resin, the ethylene-vinyl alcohol copolymer and the modified rubber were charged into a twin-screw kneader and melt-kneaded at a kneader temperature of 230 C., and the mixture was continuously extruded into strands from the extruder, then cooled with water and cut by a cutter to prepare a pellet-like thermoplastic resin composition.

(3) Evaluation Method of Thermoplastic Resin Composition

(8) The prepared thermoplastic resin composition was evaluated for air permeability and tire air leakage.

(9) (a) Air Permeability

(10) After forming the thermoplastic resin composition into a film of 0.15 mm and drying the film at 150 C. for 3 hours or more, the air permeability of the thermoplastic resin composition film was measured at a test temperature of 55 C. by using air as the test gas in accordance with JIS K7126-1 Gas Permeability Test Method (Differential Pressure Method) of Plastic Film and Sheet.

(11) (b) Change in Air Permeability after Fatigue

(12) A non-vulcanized rubber composition prepared according to the formulation shown in Table 4 was formed into a 0.5 mm-thick film. This non-vulcanized rubber composition film was laminated with a thermoplastic resin composition film produced in the same manner as in the test method of (a) Air Permeability above and vulcanized at 180 C. for 10 minutes. The obtained laminate was measured for air permeability in the same manner as in the test method of (a) Air Permeability above. After measuring the air permeability, the test piece was repeatedly elongated 1,000,000 times at room temperature under the conditions of an elongation percentage of 20% and 400 times per minute and thereby fatigued. The test piece after fatigue was measured for air permeability in the same manner as in the test method of (a) Air Permeability above, and the change in air permeability defined by the following formula was calculated.
Change in air permeability due to fatigue=air permeability after fatigue/air permeability before fatigue

(13) When the change in air permeability due to fatigue is 1.30 times or less, this is judged as passed.

(14) When the air permeability after fatigue is 1010.sup.12 cc.Math.cm/cm.sup.2.Math.sec.Math.cmHg or less, this is judged as passed.

(15) [Tire Air Leakage]

(16) The thermoplastic resin composition was formed into a film with a thickness of 80 m, and by using the film as an inner liner, a radial tire 195/65R15 was produced by a conventional method. After the produced tire was left standing for 3 months in an atmosphere of air pressure of 250 kPa and 21 C., the change in tire air pressure was measured, and the decrement of tire air pressure, which is expressed in %, was taken as tire air leakage. The tire air leakage was measured also after air was sealed into the produced tire indoors to a pressure of 140 kPa with a standard rim specified in JATMA Standards and on a drum having an outer diameter of 1,700 mm, the tire was caused to run a distance of 70,000 km at a room temperature of 38 C., a load of 300 kN and a speed of 80 km/h. The tire air leakage before running is referred to as tire air leakage before fatigue, and the tire air leakage after running is referred to as tire air leakage after fatigue. The ratio of the tire air leakage after fatigue to the tire air leakage before fatigue is taken as change in tire air leakage due to fatigue. When the change in tire air leakage due to fatigue is 1.30 times or less, this is judged as passed.

(4) Evaluation Results of Thermoplastic Resin Composition

(17) The evaluation results are shown in Tables 1 and 2.

(18) TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 5 6 1 2 3 Polyamide resin [parts by weight] 10.1 20.2 30.3 40.4 42.9 45.4 47.9 50.4 52.9 EVOH [parts by weight] 89.9 79.8 69.7 59.6 57.1 54.6 52.1 49.6 47.1 Modified rubber [parts by weight] 77.6 77.4 77.3 77.2 77.2 77.2 77.1 77.1 77.1 Total [parts by weight] 177.6 177.4 177.3 177.2 177.2 177.2 177.1 177.1 177.1 Air permeability before fatigue [10.sup.12 cc .Math. cm/cm.sup.2 .Math. sec .Math. cmHg] 3.2 3.2 3.8 4.8 5.1 5.2 5.9 6.3 6.7 Air permeability after fatigue [10.sup.12 cc .Math. cm/cm.sup.2 .Math.sec .Math. cmHg] 23.5 10.0 8.0 6.9 6.9 6.9 6.9 6.9 7.1 Change in air permeability due to fatigue [times] 7.3 3.1 2.1 1.44 1.35 1.33 1.17 1.10 1.06 Tire air leakage before fatigue [%] 0.9 0.9 0.9 1.0 1.0 1.0 1.1 1.1 1.2 Tire air leakage after fatigue [%] 6.4 2.7 1.9 1.4 1.4 1.4 1.3 1.2 1.2 Change in tire air leakage due to fatigue [times] 7.1 3.0 2.1 1.40 1.40 1.40 1.18 1.09 1.00

(19) TABLE-US-00002 TABLE 2 Example Comparative Example 4 5 6 7 8 9 10 11 Polyamide resin [parts by weight] 55.4 57.9 60.4 59.5 70.3 90.1 40.4 40.4 EVOH [parts by weight] 44.6 42.1 39.6 40.5 29.7 9.9 59.6 59.6 Modified rubber [parts by weight] 77.0 77.0 77.0 70.0 76.9 76.6 15.4 0.0 Total [parts by weight] 177.0 177.0 177.0 170.0 176.9 176.6 115.4 100.0 Air permeability before fatigue [10.sup.12 cc .Math. cm/cm.sup.2 .Math. sec .Math. cmHg] 7.2 7.7 8.0 9.5 10.7 17.0 0.13 0.10 Air permeability after fatigue [10.sup.12 cc .Math. cm/cm.sup.2 .Math. sec .Math. cmHg] 7.8 8.0 8.5 10.4 11.6 18.6 1.60 1.40 Change in air permeability due to fatigue [times] 1.08 1.04 1.06 1.09 1.08 1.09 12.3 14.0 Tire air leakage before fatigue [%] 1.2 1.2 1.3 1.4 1.5 2.0 0.6 0.6 Tire air leakage after fatigue [%] 1.3 1.3 1.3 1.4 1.6 2.2 7.5 8.5 Change in tire air leakage due to fatigue [times] 1.08 1.08 1.00 1.02 1.07 1.10 12.5 14.2

(20) TABLE-US-00003 TABLE 4 Formulation of Non-Vulcanized Rubber Composition Raw Material Amount (parts by weight) Butyl halide rubber.sup.(1) 100 GPF Carbon black.sup.(2) 30 Wet silica.sup.(3) 20 Aroma oil.sup.(4) 7.5 Zinc oxide.sup.(5) 3 Stearic acid.sup.(6) 1 Sulfur.sup.(7) 1 Vulcanization accelerator.sup.(8) 1.5 Total 164 Note: .sup.(1)BROMOBUTYL X2 produced by LANXESS Rubber. .sup.(2)HTC #G produced by Nippon Steel Chemical Carbon Co., Ltd. .sup.(3)Zeosil (registered trademark) 165GR produced by Rhodia .sup.(4)Extract No. 4 S produced by Showa Shell Sekiyu K.K. .sup.(5)Zinc Oxide Type 3 produced by Seido Chemical Industry Co., Ltd. .sup.(6)Beads Stearic Acid YR produced by NOF Corporation .sup.(7)Kinka Brand Fine Powder Sulfur 150 Mesh produced by Tsurumi Chemical Industry Co., Ltd. .sup.(8)Nocceler DM produced by Ouchi Shinko Chemical Industrial Co., Ltd.

INDUSTRIAL APPLICABILITY

(21) The thermoplastic resin composition of the present invention can be suitably utilized as an inner liner of a pneumatic tire.