A NOVEL NYLON 6.6 CAP PLY

Abstract

The present invention relates to a novel tire cord fabric or strip made of alternating a plurality of first nylon 6.6 cords and a plurality of second nylon 6.6 cords having different twists. Such a novel tire cord fabric or strips improve high speed durability, tread separation resistance and impact resistance when used as zero degree spirally wound cap ply on the belt package in pneumatic radial tires.

Claims

1. A cap ply strip, wherein the cap ply strip is made of a plurality of first nylon 6.6 cords and a plurality of second nylon 6.6 cords, wherein the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords are parallel and alternately disposed; wherein the cap ply strip is circumferentially wound on a belt package of a pneumatic radial tire; wherein a difference between the twist numbers of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords in the cap ply strip is at least 50 tpm; wherein the twist number of the plurality of second cords is not less than 50% of the twist number of the plurality of first cords; wherein the plurality of the first nylon 6.6 cords are a plurality of higher twist cords B and the plurality of the second nylon 6.6 cords are a plurality of lower twist cords A.

2. The cap ply strip according to claim 1, wherein the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords are respectively two-ply cords.

3. The cap ply strip according to claim 1, wherein the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords are respectively three-ply cords.

4. The cap ply strip according to claim 1, wherein the difference between the twist numbers of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords is greater than or equal to 100 tpm.

5. The cap ply strip according to claim 1, wherein a linear density of all the nylon 6.6 cords are greater than or equal to 500 dtex and less than or equal to 6,000 dtex.

6. The cap ply strip according to claim 1, wherein a difference between the linear densities of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords is less than 15%.

7. The cap ply strip according to claim 1, wherein the linear density of the plurality of first nylon 6.6 cords is equal to that of the plurality of second nylon 6.6 cords.

8. The cap ply strip according to claim 1, wherein an arrangement of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords in the strip is as follows: A+B+A+B+A+B and repeats.

9. The cap ply strip according to claim 1, wherein an arrangement of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords in the strip is as follows: AB+AB+AB and repeats as a plurality of paired cords.

10. The cap ply strip according to claim 1, wherein an arrangement of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords in the strip is as follows: A+B+B+A+B+B+A+B+B+A and repeats.

11. The cap ply strip according to claim 1, wherein an arrangement of the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords in the strip is as follows: A+A+B+A+A+B+A+A+B and repeats.

12. The cap ply strip according to claim 1, wherein a cord count in the strip is greater than or equal to 70 epdm (ends per decimeter).

13. The cap ply strip according to claim 1, wherein a difference of the 7% LASE values between the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords is minimum greater than or equal to 15%; wherein the 7% LASE values are determined according to ASTM D885-16.

14. The cap ply strip according to claim 1, wherein a difference of the 7% LASE values between the plurality of first nylon 6.6 cords and the plurality of second nylon 6.6 cords is greater than or equal to 25%; wherein the 7% LASE values are determined according to ASTM D885-16.

15. The cap ply strip according to claim 1, wherein a width of the cap ply strip is greater than or equal to 8 mm and less than or equal to 25 mm.

16. The cap ply strip according to claim 1, wherein a width of the cap ply strip is greater than or equal to 10 mm and less than or equal to 15 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a cross-sectional view of a conventional (prior art) nylon cap ply on cross-ply steel cord belt package after curing process.

[0033] wherein a is cross ply steel cord belt package;

[0034] b is conventional cap ply on belt package;

[0035] c is tread.

[0036] FIG. 2 is a cross-sectional view of a nylon cap ply according to the invention on cross-ply steel cord belt package after curing process.

[0037] wherein a is cross ply steel cord belt package;

[0038] b is cap ply on belt package according to the invention;

[0039] c is tread.

[0040] FIG. 3A is a cross-sectional view of nylon cap ply cord arrangements according to the invention on cross-ply steel cord belt package, (1) before curing process, (2) after curing process;

[0041] A: Nylon 6.6 cord with higher twist or higher twist multiplier having lower modulus;

[0042] B: Nylon 6.6 cord with lower twist or lower twist multiplier having higher modulus;

[0043] H: Penetration difference of A and B cords in rubber matrix.

[0044] FIG. 3B is a top view of nylon cap ply strip made of A (higher twist, lower modulus, lower tension) and B (lower twist, higher modulus, higher tension) cords.

[0045] FIG. 4A is a cross-sectional view of nylon cap ply with side-by-side paired cords according to invention on cross-ply steel cord belt package, (3) before curing process, (4) after curing process;

[0046] FIG. 4B is a top view of side-by-side (paired) A (higher twist, lower modulus, lower tension) and B (lower twist, higher modulus, higher tension) cords in cap ply strip.

[0047] FIG. 5 shows the cord-to-cord distance (rivet area, spacing) changes after curing process;

[0048] S1: Cord-to-cord distance between A and B before process expansion and curing;

[0049] S2: Cord-to-cord distance between A and B after process expansion and curing;

[0050] S3: Cord-to-cord distance between A and A after process expansion and curing;

[0051] S4: Cord-to-cord distance between B and B after process expansion and curing.

[0052] FIG. 6 shows 1+2+1 cap ply cord arrangements;

[0053] (1)A+B+B+A+B+B+A+. . . cord arrangement before process expansion and curing;

[0054] (2)A+B+B+A+B+B+A+. . . cord arrangement after process expansion and curing.

[0055] FIG. 7 shows 2+1+2 cord arrangements;

[0056] (1)A+A+B+A+A+B+A+A+. . . cord arrangement before process expansion and curing;

[0057] (2)A+A+B+A+A+B+A+A+. . . cord arrangement after process expansion and curing.

DETAILED DESCRIPTION OF THE INVENTION

[0058] According to the invention, the spirally wound cap ply fabrics or cap ply strips on belt package of the pneumatic radial tires in circumferential direction, having alternately disposed parallel nylon 6.6 warp cords with different twist levels; [0059] improves the high speed durability due to high modulus of low twist nylon cords, and the increased cord-to-cord distances (less shear stresses) between the cords (cord shiftings in vertical direction, two layer or zig-zag formation), (FIG. 3A, FIG. 3B and FIG. 5). [0060] improves the impact resistance of belt package due to higher energy absorption of high twist, and high extensible nylon cords [0061] and also improves the tread-cap ply separation resistance due to the wavy surface structure of the cap ply. The zig-zag surface enhances also mechanical bonding between cap ply and tread compound.

[0062] The first nylon cords (higher twist cord, A) and second nylon cords (lower twist corsi B) in cap ply strip are two and/or three-ply cords.

[0063] The angle of spirally wound cap ply strips to circumferential center line (or equatorial plane of the tire) is 0 to 5.

[0064] In order to obtain the advantages mentioned above, the minimum twist difference between the alternate nylon cords having the same total cord dtex, should be 50, preferably 100 tpm (e.g. first cord, 1400x2, Z/S, 350/350 tpm, and second cord, 1400x2, Z/S, 250/250 tpm). But minimum cord (cable) twist must not be less than 150 tpm.

[0065] If the cord twist difference is less than 50 tpm between the first and second cords, the LASE, modulus or extensibility difference between the first and second cords becomes insignificant. Under those conditions, the wavy cap ply surface can not be created on the belt package of the tire.

[0066] On the other hand, the twist difference between the first and second cords must not exceed the 50% of the first cord twist (higher twist cord, A), for example 350 tpm vs. 175 tpm.

[0067] The total linear density of the cords is minimum 500 dtex and maximum 6,000 dtex. The cap ply cords having less than 500 dtex are too thin and LASE values are too low which can not provide enough restraining force even with very high cord counts (epdm). Besides this drawback, during process lifting and curing, they can cut the skim compound of the belt layer and contact to steel cords. The cap ply cords having higher than 6,000 dtex are too thick and requires too much rubber for coating. The potential drawback for such cords in tire is increased rolling resistance and heat build-up in the crown area.

[0068] The total linear density difference between the first and second cords is less than 15%. Preferably, the total linear densities of first and second cords should be same.

[0069] According to the invention, the sequence of the higher and lower twist nylon cords which are parallel to each other in a cap ply strip is in a alternating form as follows; A+B+A+B+A+B+. . . and so on, wherein A is the first cord with higher twist, and B is the second cord with lower twist compared to A. Such a cap ply strip creates a uniform wavy surface after curing process, which bonds to tread compound strongly improving tread separation resistance under high speed conditions.

[0070] According to the invention, the sequence of the higher and lower twist nylon cords which are parallel to each other in a cap ply strip is in a alternating form as follows AB+AB+AB+. . . and so on, as paired cords, wherein A is the first cord with higher twist, and B is the second cord with lower twist compared to A.

[0071] According to the invention, the sequence of the higher and lower twist nylon cords which are parallel to each other in a cap ply strip is in a alternating form as follows A+B+B+A+B+B+A +B+B+. . . and so on, wherein A is the first cord with higher twist, and B is the second cord with lower twist compared to A.

[0072] According to the invention, the sequence of the higher and lower twist nylon cords which are parallel to each other in a cap ply strip is in a alternating form as follows A+A+B+A+A+B+A +A+B+. . . and so on, wherein A is the first cord with higher twist, and B is the second cord with lower twist compared to A.

[0073] According to the invention, the cord count in strip is minimum 70 epdm (ends per decimeter). In case of cord counts lower than 70 epdm, the effectiveness of surface waviness is not enough for mechanical bonding to tread.

[0074] According to the invention, the difference between the 7% LASE values of the first and second nylon cords is minimum 15%, and preferably 25% (7% LASE values are determined according to ASTM D885-16).

[0075] According to the invention, the width of the cap ply strips is 8 to 25 mm, preferably 10 to 15 mm.