JPH01321940A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To obtain the subject tire having excellent physical properties at high speed, etc., and tire productivity by using core-sheath type mixed fiber consisting of core component of polyester-based polymer and sheath component of polyamide-based polymer as fiber filament yarn composing fiber cord in carcass layer. CONSTITUTION:Cord of core-sheath type mixed fiber consisted of core component of polyester-based polymer and sheath component of polyamide-based polymer is used as carcass cord comprising carcass layer. Said cord exhibits high modulus as well as polyester fiber cord and excellent adhesion and resistance to chemicals to rubber as well as nylon cord.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a fiber cord (casscord) constituting a carcass layer, which uses a polyester polymer as a core component,
The present invention relates to a novel pneumatic radial tire that uses a fiber cord made of a core-sheath composite fiber filament whose sheath component is a polyamide polymer, and which has excellent high speed performance and durability.

[Conventional technology]

A radial tire has a crown part reinforced with an extremely highly resilient heldbrie layer along the circumferential direction of the tire.
The tire also has a sidewall portion reinforced with carcass plies arranged in a direction substantially perpendicular to the tire circumferential direction. In a radial tire having such a structure, if the rigidity of the sidewall portion decreases, the steering stability of the vehicle will significantly decrease due to an imbalance with the rigidity of the crown portion. Therefore, it is necessary to ensure that the sidewalls have a degree of rigidity that does not impair the ride comfort of the vehicle.

Conventionally, from this point of view, fiber cords with a small initial modulus, such as polyamide fiber cords such as nylon 6 and nylon 66, have rarely been used in carcass plies of radial tires. Fiber cords with relatively large initial modulus have been used.

However, the polyester fiber 21-de had a small amount of functional groups contained in its polymer chain, and its adhesion to rubber was low. Therefore, it was necessary to perform a two-step process of treating with an epoxy or isocyanate adhesive and then treating with a mixture of resorcinol/formalin initial condensate and rubber latex (so-called RFL), making the adhesive process complicated. . Moreover, in the case of polyester fibers, the ester bonds in the polyester are hydrolyzed by amine compounds and moisture generated from the vulcanization accelerator in the rubber, resulting in a decrease in the strength of the fiber cord and deterioration of the adhesion with the rubber. It had the disadvantage of poor chemical stability.

In recent years, flat radial tires such as VR or ZR, which are required to have ultra-high-speed performance and have been developed along with the development of expressway networks, are more effective at high speeds than conventional radial tires, especially at the ends of the belt layer. If the adhesion between the carcass layer and the belt layer is low as a result of increased heat generation, the ultra-high speed performance will not be satisfied.

Therefore, fibers that cause adhesive deterioration such as polyester fibers cannot be used, and therefore rayon, which has good adhesive properties and a relatively high initial modulus, is preferably used. However, this rayon has a significant hygroscopic property, and since the initial monylus is reduced due to moisture absorption, strict moisture (humidity) control is required, and there is a problem that the productivity of the tire is extremely poor.

In addition, polyester fiber cords are used as carcass cords for light truck and trunk radial tires that are used under relatively harsh conditions, but due to problems with adhesive deterioration and chemical stability of polyester fibers, these Since the tire has low durability and the carcass cord deteriorates significantly, it is practically difficult to retread the tire (retread μ/7d), and there is also a problem from an economic point of view. For this reason, some tires use steel cords for the carcass cord, but when steel cords are used for the carcass, the weight of the tire decreases, resulting in a problem that the fuel efficiency of the tire decreases. Further, steel cords have the disadvantage that they rust due to moisture, resulting in deterioration of adhesion and reduced durability.

As is clear from the above description, the carcass cord constituting the conventional radial tire does not simultaneously satisfy both the performance as a radial tire and the productivity (economical efficiency) of the tire.

[Purpose of the invention]

The object of the present invention is to create a new pneumatic radial tire that eliminates the drawbacks of the pneumatic radial tire using the polyester fiber cord as a carcass cord and satisfies both tire performance such as high speed and durability as well as tire productivity (economical efficiency). To provide a pneumatic radial tire.

[Structure of the invention]

The pneumatic radial tire of the present invention has at least one carcass layer in which the fiber cords are arranged in a direction substantially perpendicular to the tire circumferential direction, and the fiber filament yarns constituting the fiber cords are polyester-based. It is characterized by being composed of a core-sheath type composite fiber having a polymer as a core component and a polyamide polymer as a sheath component.

The pneumatic radial tire of the present invention requires that the fiber cords constituting the carcass layer are arranged in a direction substantially perpendicular to the tire circumferential direction. When there are two or more carcass layers, the carcass cords of the carcass layers stacked one above the other do not need to be arranged in exactly the same direction, but only need to be arranged in substantially the same direction. More specifically, the angle between the carcass cord and the axis perpendicular to the circumferential direction of the tire is less than 2.5 degrees, and the intersection angle of the carcass cords of the carcass layers stacked above and below is less than 5 degrees. preferable.

FIG. 1 is a half-sectional view showing an example of the pneumatic radial tire of the present invention. As shown in the figure, a bell l-layer 5 is provided at the bottom of the tread 1, and a carcass layer 4 is provided below this belt layer 5. 2 indicates the side mail, 3 indicates the heat, 6 indicates the cover layer, and EE' indicates the tire circumferential direction (equatorial plane). Further, 10 and 10a are a differential transformer and a roller, respectively, for measuring the side unevenness of the tire.

As shown in FIG. 1, the pneumatic radial tire of the present invention each has a pair of bead wires and a sidewall part, and a heel 1-- between a trend part 1 and a carcass layer 4 that are continuous with both sidewall parts. It has IW5. As this heald layer 5, a steel cord is mainly used, but an aromatic polyamide fiber cord such as "Kevlar" manufactured by DuPont may also be used.

Further, in order to further improve the high speed performance of the tire, it is preferable to insert a cover layer 6 made of nylon fiber cords having a cord angle of 00 with respect to the tire circumferential direction between the belt layer 5 and the tread rubber portion 1.

A feature of the present invention is the use of a cord made of core-sheath composite fiber filament yarn as the carcass cord, which has a high modulus comparable to that of a polyester fiber cord, excellent adhesion to rubber equivalent to a nylon cord, and chemical stability. It is in the point of doing. FIG. 2 is a sectional view showing an example of such a core-sheath type composite fiber, where C is a core component and S is a sheath component.

As shown in the figure, a core-sheath type composite fiber has a core component C at the center of the single fiber cross section, which is surrounded by a sheath component S, which is similar in the longitudinal direction of the fiber. Refers to something that has a form. Core component C present in sheath component S
The number of trees may be one as shown in FIG. 2, or it may be two or more trees.

Core-sheath type composite IMi 1 constituting the carcass cord of the present invention
It is necessary that the core component be made of a polyester polymer and the sheath component be made of a polyamide polymer. This is because if the arrangement of these two types of combined components is opposite (reverse), even if this is used as the carcass layer -F of a radial tire, it will not be possible to satisfy both high-speed durability and durability at the same time. In other words, the core component polyester polymer is covered with a polyamide polymer as a sheath component, which isolates the polyester polymer, which has low adhesiveness, from the rubber layer, and makes the fiber surface in contact with the rubber layer have good adhesiveness. It can be formed from a polyamide-based polymer. Therefore, this core-sheath type composite fiber not only has a high modulus equivalent to that of polyester fibers, but also has significantly superior adhesive properties compared to polyester fibers, and because the core component polyester polymer is coated, polyester fibers It does not cause adhesive deterioration unlike other fibers, and has excellent chemical stability.

A typical example of the polyester polymer constituting the core component of the core-sheath composite fiber is polyethylene terephthalate, which has ethylene terephthalate as a repeating structural unit of the polymer chain, but it has a high degree of polymerization, preferably orthochlorophenol. As a solvent, polyethylene terephthalate having an intrinsic viscosity measured at 25° C. of at least 0.80 is preferred. This polyethylene terephthalate may be copolymerized with a small amount of a copolymerizable third component such as a carboxylic acid such as isophthalic acid or oxybenzoic acid or a derivative thereof.

In addition, the polyamide polymer of the sheath component includes fiber-forming nylon 66 (polyhexamethylene adivamide), nylon 6 (polycaprolactam), nylon 46 (polytetramethylene adipamide), and copolymers thereof. You can list combinations, etc. Among these,
Particularly preferred is nylon 66, which has a high melting point close to that of polyester polymers and a relative viscosity of at least 2.8 in sulfuric acid at 25°C.

The composite ratio (the cross-sectional area ratio of the core component and the sheath component) of the core-sheath type composite fiber is not particularly limited, but it may be necessary to improve the adhesion of the core component polyester polymer to rubber or the chemical stability. The cross-sectional area ratio of the core component made of polyester polymer may be selected to be as large as possible within a range that maximizes the effect and minimizes the decrease in modulus. Specifically, this composite ratio is
The core:sheath cross-sectional area ratio is appropriately selected within the range of 90:10 to 10:90, preferably 80:20 to 20:80, and more preferably 70:30 to 30Nia. The ratio of this sheath component is too small,
If the core component becomes too large, the polyester polymer of the core component will be exposed, which is undesirable since the adhesion to rubber and chemical deterioration resistance will decrease. On the other hand, if the sheath component becomes too large, the proportion of the polyamide-based polymer becomes excessive and the initial modulus of the fiber cord becomes low, which reduces the tire casing rigidity and thus reduces the steering stability.

The core-sheath type composite fiber used in the present invention is preferably obtained by a high-speed spinning method in which the spinning speed is at least 2000 m/min, preferably 3000 m/min or more. This is because by applying this high-speed spinning method, the bonding (adhesion) force between the core component made of a polyester polymer and the sheath component made of a polyamide polymer is improved. The reason for this is not clear, but the crystallization of the above two polymers, especially the crystallization of the easily crystallized polyamide polymer, is suppressed due to high-speed spinning, and the polymer chains are oriented in the fiber axis direction. This is presumed to be due to the fact that, since it is simultaneously bonded to the core component polyester polymer oriented in the fiber axis direction, stress concentration at the bonding interface between both components during spinning and drawing processes is significantly suppressed. .

A plurality of filaments 1- made of the core-sheath composite fibers are converged and twisted to form a carcass cord. The twist to be applied to this cord is determined by considering the fiber cord's convergence, initial adhesive strength, fatigue resistance, strength, initial modulus, etc., K=TJ In the above formula, K is the twist coefficient, T represents the number of twists (twists/10 cm), and D represents the total denier of the cord.

The twist coefficient represented by is in the range of 1000 to 3000, preferably in the range of 1400 to 2400.

This twisted cord is then treated with adhesive as shown in 2.
It is desirable that the elongation rate under a load of 25 g/d is 6.5% or less, and the dry heat shrinkage rate at 150°C is 6.0% or less.

In the radial tire, if the elongation rate of the adhesive-treated cord exceeds 6.5χ, the initial modulus as a carcass cord is too low and the steering stability as a radial tire decreases. Furthermore, if the dry heat shrinkage rate exceeds 6.0x, the uniformity of the tire will deteriorate as the fiber cord shrinks during tire vulcanization, and the initial modulus of the cord will also decrease.

In the present invention, the number of cords driven into the carcass auxiliary layer varies depending on the type of tire, but usually,
20-70 pieces 15cm, preferably 30-60 pieces 15cm
It is best to keep it within the range of m.

EXAMPLES Hereinafter, the effects of the present invention will be specifically explained with reference to Examples.

In the examples, the high-speed durability, durability, and side unevenness of the tires are values measured by the following methods, respectively.

High-speed durability: Using tires with a tire size of 205/60VR15,
The tires were run under the following conditions in an indoor high-speed durability test until they broke, and judgments were made based on the results.

Test conditions internal pressure 3. OKgf/cm2゜Load JATMΔ Design Regular Design Regular Load 515 Kudram Diameter 1707mm0 Rim 15X5 1/2 JJ.

Load durability: Using tires with a tire size of 205/60 and R15,
The tires were run under the following conditions in an indoor load durability test until they broke, and judgments were made based on the results.

Test condition Internal pressure JATMΔATMΔ pressure 2.5Kgf/cm2.

Load JATMA design regular design regular load 515 speed
81km/hr.

Drum diameter: 1707mm.

Rim 15X51/2 JJo Site unevenness: Measure the side unevenness, which is a measure of the dimensional non-uniformity of the tire in the circumferential direction, that is, the dimensional change in the tire radial direction on the tire circumference by 50 mm, and calculate the peak and The peak and peak was measured over the entire circumference of the tire, and the maximum value was taken as the site unevenness. The internal pressure of the tire at the time of measurement was determined according to JASOC607, using a roller (10
The diameter of a) was 20 mm, the measurement rotation speed was 25 rpm, and a differential transformer (10) was used as the detector.

Examples and Comparative Examples Polyethylene terephthalate is used as the core component, and nylon 6
A core-sheath type composite fiber foramen 1-system of 15,000 having a composite ratio of 50,150 in cross-sectional area ratio with 6 as a sheath component was
The number of upper twists is 404710cm, and the number of lower twists is 40.
A twisted cord with twist/1.0 cm and twist coefficient K of 2191 was created. The cord was treated with resorcinol-formalin-rubber latex (RFL) adhesive at 235°C to 0.00%.
Heat treated under 5g/d tension, elongation rate under 2.25g/d load is 4.8χ, dry heat shrinkage rate at 150°C is 4.3
We created an adhesive processing code that is χ.

This treated cord was embedded in unvulcanized rubber with a number of 50 pieces of 15 cm, forming a green tire, and vulcanized to make a tire with a 205/60 VR15 tire (
A tire (hereinafter referred to as the tire of the present invention) was created.

The performance of the obtained tires is shown in the table.

For comparison, we used two 1500D polyester fiber cords.
A twisted cord was created by aligning the wood tension and twisting the yarn to have an upper twist of 40 times/10 cm, a lower twist of 40 times/10 cm, and a twist coefficient K of 2191. After pre-treating this cord using the polyester adhesive "Haluriki Bond TE" manufactured by Vulnax, the above 1':! F L, treated with adhesive, 235
Heat treated at °C under 0.5 g/d tension, 2.25 g/d
An adhesive-treated cord was prepared with an elongation rate under a load of d of 4.4χ and a dry heat shrinkage rate of 3.6χ at 150°C. This treated cord is embedded in an unvulcanized comb with the number of implants of 50 pieces of 15 cm to form a green tire, which is vulcanized to form a 205/60 VR15 tire (hereinafter referred to as
A comparative tire (referred to as a comparative tire) was prepared, and the performance of the obtained tire is shown in the table.

High-speed durability, load durability, and side unevenness are all index values with the measured value of the comparative tire being 100, and larger values indicate better performance.

From the table, it can be seen that the tires of the present invention are superior in high-speed durability, load durability, and side surface irregularities as compared to conventional tires.

〔Effect of the invention〕

According to the present invention, by using, as a carcass cord, a fiber cord consisting of a core-sheath type composite fiber filament yarn whose core component is a polyester spinning wheel combined and whose sheath component is a polyamide polymer, the characteristics of the carcass cord can be improved from that of a polyester spinning wheel. It has high initial modulus, lath, or stiffness equivalent to fiber cord, and has chemical stability (deterioration) resistance.
The heat resistance, adhesion, etc. are significantly improved, and the radial tire is not only durable, but also has excellent unevenness on the noid part.

In addition, since it has excellent adhesion as a carcass layer, it can provide excellent adhesion to rubber with just one step of adhesive treatment, for example by RFL, simplifying the adhesive treatment process and improving tire productivity. I can do it.

[Brief explanation of the drawing]

Regarding the first aspect, FIG. 2 is a half cross section showing an example of a pneumatic radial tire of the civil engineering invention, and FIG. 2 is a cross section M showing an example of the core-sheath type composite fiber used in the present invention. C. Core component, S. Sheath component, 1. I. Red, 3
...Bead wire, 4u...Upper carcass layer, 4d
...Lower carcass layer, 5u...Upper belt layer, 5d
...lower heald layer. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] The fiber cord has at least one carcass layer arranged in a direction substantially perpendicular to the circumferential direction of the tire, and the fiber filament yarns constituting the fiber cord have a polyester polymer as a core component and a polyamide-based fiber cord. A pneumatic radial tire made of a core-sheath type composite fiber whose sheath component is a polymer.