CAP PLY STRIP WITH DIFFERENT NYLON 6,6 CONSTRUCTIONS

Abstract

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

Claims

1. A cap ply strip comprising: alternately woven nylon 6.6 cords and single ply twisted nylon 6,6 yarns circumferentially wound on a belt package of a pneumatic radial tire; wherein a twist factor of the nylon 6,6 cords, determined according to the following formula
Twist factor=Cord twist (tpm)(total linear density of cord as dtex).sup.1/2, is at least 10,000 and maximum 15,000; and a twist factor of the single ply twisted nylon 6,6 yarn is at least 5,000 unit less than the twist factor of the nylon 6,6 cord.

2. The cap ply strip according to claim 1, wherein the nylon 6,6 cords are two-ply cords.

3. The cap ply strip according to claim 1, wherein the nylon 6,6 cords are three-ply cords.

4. The cap ply strip according to claim 1, wherein the twist factor of the single ply twisted nylon 6,6 yarn, determined according to the following formula
Twist factor=Ply twist of yarn (tpm)(linear density of yarn as dtex).sup.1/2, is minimum 5,000 and maximum 8,000.

5. The cap ply strip according to claim 1, wherein a linear density of the nylon 6,6 cords is minimum 700 dtex and maximum 5,000 dtex.

6. The cap ply strip according to claim 1, wherein a linear density of the single ply twisted nylon 6,6 yarns is minimum 350 dtex and maximum 3,000 dtex.

7. The cap ply strip according to claim 1, wherein a linear density of the single ply twisted nylon 6,6 yarn is not less than 50% of a total linear density of the nylon 6,6 cord.

8. The cap ply strip according to claim 1, wherein the nylon 6,6 cords and the single ply twisted nylon 6,6 yarns are arranged alternatively in the cap ply strip such that each nylon 6.6 cord is followed by one single ply twisted nylon 6.6 yarn.

9. The cap ply strip according to claim 1, wherein the nylon 6,6 cords and the single ply twisted nylon 6,6 yarns are arranged in a repeated pattern where one nylon 6,6 cord is followed by two single ply twisted nylon 6,6 yarns in the cap ply strip.

10. The cap ply strip according to claim 1, wherein the nylon 6,6 cords and the single ply twisted nylon 6,6 yarns are arranged in a repeated pattern where two nylon 6,6 cords are followed by one ply twisted nylon 6,6 yarn in the cap ply strip.

11. The cap ply strip according to claim 1, wherein a cord count in the cap ply strip is minimum 70 epdm (ends per decimeter).

12. The cap ply strip according to claim 1, wherein a width of the cap ply strip is minimum 8 mm and maximum 25 mm.

13. The cap ply strip according to claim 1, wherein a width of the cap ply strip is minimum 10 mm and maximum 15 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a cross-sectional view of conventional (prior art) nylon cap ply on cross-ply steel cord belt package after curing process.

a is cross ply steel cord belt package
b is conventional cap ply on belt package
c is tread

[0035] FIG. 2 is a cross-sectional view of nylon cap ply according to invention on cross-ply steel cord belt package after curing process.

a is cross ply steel cord belt package
b is cap ply on belt package according to invention
c is tread

[0036] FIG. 3 is a cross-sectional view of nylon cap ply cord and yarn arrangements according to invention on cross-ply steel cord belt package, (1) before curing process,

(2) after curing process
A: Two-ply nylon 6.6 cord with higher twist factor, lower modulus and higher extensibility
B: Single ply twisted nylon 6.6 yarn with lower twist factor, higher modulus and lower extensibility
H: Penetration difference of A and B in rubber matrix

[0037] FIG. 4 shows the cord-to-cord distance (rivet area, spacing) changes after curing process.

[0038] (1) before curing process, (2) after curing process

[0039] S1: Cord-to-cord distance between A and B before process expansion and curing.

[0040] S2: Cord-to-cord distance between A and B after process expansion and curing

[0041] S3: Cord-to-cord distance between A and A after process expansion and curing

[0042] S4: Cord-to-cord distance between B and B after process expansion and curing

[0043] FIGS. 5 and 6 are similar to FIGS. 3 and 4 but with lower dtex single ply twisted nylon 6,6 yarns

(1) before curing process. (2) after curing process

[0044] FIG. 7 shows 1+2+1 cap ply cord and yarn arrangements.

(1) before curing process, (2) after curing process
(1) A+B+B+A+B+B+A+ . . . cord arrangement before process expansion and curing
(2) A+B+B+A+B+B+A+ . . . cord arrangement after process expansion and curing

[0045] FIG. 8 shows 2+1+2 cap ply cord and yarn arrangements.

(1) before curing process, (2) after curing process
(1) A+A+B+A+A+B+A+A+ . . . cord arrangement before process expansion and curing
(2) A+A+B+A+A+B+A+A+ . . . cord arrangement after process expansion and curing

DETAILED DESCRIPTION OF THE INVENTION

[0046] According to invention, the spirally wound cap ply fabrics or cap ply strips on belt package of the pneumatic radial tires in circumferential direction, having alternate nylon 6.6 cords and nylon 6,6 single ply twisted yarns as warp; [0047] improves the high speed durability due to high average strip modulus, and increased cord-to-cord and yarn-to-yarn distances (less shear stresses) because of yarn shiftings in vertical direction (two layer or zig-zag formation, FIGS. 3, 4, 5 and 6). [0048] improves the impact resistance of belt package due to higher energy absorption of high twist, and high extensible nylon cords (upper level cords are more responsive to the impacts, and lower level cords are more responsive to the tire growth). [0049] 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.

[0050] The nylon 6,6 cords have two or three-ply cord constructions. The alternately disposed yarns are single ply twisted yarns.

[0051] The angle of spirally wound cap ply strips to circumferential center line (or equatorial plane of the tire) is 0 to 50.

[0052] In order to obtain the advantages mentioned above, the twist factor of nylon 6,6 cords determined according to the formula (1a) given below is minimum 10,000 and maximum 15,000.

Twist factor=Cord twist (tpm)(total linear density of cord as dtex).sup.1/2(1a)

[0053] According to the similar formula given below (1b), the twist factor of the single ply twisted yarn is minimum 5,000 and maximum 8,000.

Twist factor=Ply twist of yarn (tpm)(linear density of yarn as dtex).sup.1/2(1b)

[0054] According to the invention, the twist factor of the single twisted nylon 6,6 yarn is at least 5,000 unit less than the twist factor of the cord in the same cap ply strip (e.g. 14002, 250/250 tpm, and 14001, 180 tpm).

[0055] If the twist factor difference is less 5,000 unit, the wavy cap ply surface can not be created on the belt package of the tire.

[0056] According to the invention the total linear density of the cord is minimum 700 dtex and maximum 5,000 dtex, and the linear of the single ply twisted yarn is minimum 350 dtex and maximum 3,000 dtex. Those linear density limits prevent excessive rubber cuttings and too high rubber gauges. Excessive rubber cuttings may lead to the contact of cap ply cords and yarns with steel cords of belt layer and abrasion-induced breakages. Too high rubber gauge in crown area cause high heat buildup and increased rolling resistance.

[0057] The linear density of the single ply twisted yarn maximum 50% less than the total linear density of the cord.

[0058] According to the invention, the sequence of the cords and the yarns which are parallel to each other in a cap ply strip is in an alternating form as; A+B+A+B+A+B+ . . . and so on, wherein A is two or three ply nylon 6,6 cord, and B is single ply twisted nylon 6,6 yarn (FIGS. 3, 4, 5 and 6). 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.

[0059] According to the invention, the sequence of the cords and the yarns which are parallel to each other in a cap ply strip is in an alternating form as follows A+B+B+A+B+B+A+B+B+ . . . and so on, wherein A is two or three ply nylon 6,6 cord, and B is the single ply twisted nylon 6,6 yarn (FIG. 7).

[0060] According to the invention, the sequence of the cords and yarns 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 two or three ply nylon 6,6 cord, and B is single ply twisted nylon 6,6 yarn (FIG. 8).

[0061] 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.

[0062] According to the invention, the width of the cap ply strips is 8 to 25 mm, preferably 10 to 15 mm.