Polyester tire cord having excellent heat resistance, and tire comprising same
The present invention relates to a polyester tire cord made of polyester yarn and having a 5% LASE of 1.2 g/d or more as measured according to ASTM D885 at 80° C., a 5% LASE of 1.0 g/d or more as measured according to ASTM D885 at 120° C., and a toughness retention rate of 65% or more at 80° C. and 120° C. The tire cord of the present invention has a modulus comparable to that of rayon even in a high-temperature environment at 120° C. or higher, and has excellent dimensional stability and heat resistance, and thus it can be advantageously applied to a high-performance tire.
1. A polyester tire cord made of polyester yarn and having a 5% LASE of 1.2 g/d or more as measured according to ASTM D885 atz 80° C., a 5% LASE of 1.0 g/d or more as measured according to ASTM D885 at 120° C., and a toughness retention rate of 65% or more at 80° C. and 120° C. as calculated by the following Equation 6:
toughness retention rate ( T 25 −T 80 )=(toughness value at T 80 /toughness value at T 25 )×100
toughness retention rate ( T 25 −T 120 )=(toughness value at T 120 /toughness value at T 25 )×100 [Equation 6]
wherein
the toughness value at T 25 is a toughness value of the polyester tire cord, measured after standing at 25° C. and 65% RH for 24 hours, the toughness value at T 80 is a toughness value of the polyester tire cord, measured at an atmosphere temperature of 80° C., and the toughness value at T 120 is a toughness value of the polyester tire cord, measured at an atmosphere temperature of 120° C.,
the polyester yarn is manufactured by a spinning step and multi-stage drawing steps in which a specific draw ratio (a spin draft/a total draw ratio) is 800 to 1400,
the polyester tire has a cord fineness of 2,000 to 8,000 denier, 2 to 4 plies, and 200 to 400 TPM.
2. The polyester tire cord of claim 1 , having an L/E 80 value of 1.5 kg/% to 3.5 kg/% as measured by the following Equation 1, and an L/E 120 value of 1.0 kg/% to 3.0 kg/% as measured by Equation 1:
L/E T =LASE (kg, @5%)/elongation at load (%, @2.25 g/d) [Equation 1]
wherein LASE represents a load at an elongation of 5%, measured at a predetermined temperature (T) (° C.), and E represents an elongation at a load of 2.25 g/d.
3. The polyester tire cord of claim 1 , having a strength of 5.0 g/d or more and a shrinkage of 3% or less as measured at a static load of 0.05 g/d at 177° C. for 2 minutes.
4. The polyester tire cord of claim 1 , wherein the polyester yarn simultaneously satisfies an elongation of 2.5% to 3.0% at a load of 2.25 g/d, an elongation of 5.0% to 6.0% at a load of 4.5 g/d, and an elongation of 7.5 to 9.0% at a load of 6.75 g/d.
5. The polyester tire cord of claim 4 , wherein the polyester yarn simultaneously satisfies the following conditions (1) to (6):
(1) intrinsic viscosity (I.V.): 0.85 to 1.00
(2) strength: 7.0 g/d or higher
(3) amorphous orientation factor (AOF): 0.70 to 0.80
(4) shrinkage: 4.0% or less
(5) degree of crystallinity: 50% or higher
(6) dimensional stability: 8.5% or less.
6. The polyester tire cord of claim 1 , wherein the polyester is polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalene, or poly(trimethylene terephthalate).
7. The polyester tire cord of claim 1 , wherein the specific draw ratio (the spin draft/the total draw ratio) is 1000 to 1400.
8. The polyester tire cord of claim 1 , wherein the spin draft is 1800 to 2400.
9. The polyester tire cord of claim 1 , wherein the total draw ratio 1.7 to 1.9.
10. A tire comprising the polyester tire cord of claim 1 .
11. The tire of claim 10 , further comprising: a tread; a pair of sidewalls disposed on both sides of the tread; and a pair of bead portions disposed on radially inner sides of the sidewalls of the tire, wherein the carcass comprises the polyester tire cord.