JPH01282359A - Pneumatic bias tire - Google Patents

Abstract

PURPOSE:To obtain a tire hardly generating flat spot, chemical deterioration or adhesive deterioration by applying core-sheath type conjugate fiber containing polyester-based polymer as core and polyamide-based polymer as sheath to carcass. CONSTITUTION:In a bias tire including at least two carcasses in which directions of fiber cords contained in adjacent layers are crossed each other, the fiber cord is constructed with a filament of core-sheath type conjugate fiber of core component of polyester-based polymer and sheath component of polyamide-based polymer. Ratio of cross section areas of core and sheath is preferably 70:30-30:70.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention has a plurality of carcass layers made of a core-sheath type composite fiber filament cord having a polyester polymer as a core component and a polyamide polymer as a sheath component. ,durability,
This invention relates to a pneumatic bias tire with excellent handling stability and reduced noise.

(Prior art) Conventionally, fiber cords made of polyamide fibers or polyester fibers have been used for the carcass of pneumatic bias tires, but these fiber cords have advantages and disadvantages due to their characteristics as carcass cords. Therefore, it was difficult to use fiber cords made of the same material regardless of the type of tire.

For example, in the case of polyamide fibers such as nylon 6 and nylon 66, compared to polyester fibers,
Due to its excellent adhesion to rubber, fatigue resistance, and strength, it is used as a carcass with a high number of brakes for bias tires for trucks, buses, and construction vehicles, where durability is of the utmost importance. However, this polyamide fiber has a low initial modulus and a low glass transition point, so
When used in tires with a small number of carcass plies, such as bias tires for passenger cars and bias tires for light trucks, handling stability deteriorates and flat spots tend to occur due to the low glass transition temperature. Ta.

On the other hand, polyamide fibers have a slightly lower strength than the above-mentioned polyamide fibers, but their initial modulus is large, so their handling stability is relatively good, and their glass transition temperature is high, so they are similar to polyamide fiber cords. Na hula 7
It does not cause tospots and is preferred as a carcass cord for bias tires for passenger cars.

However, with this polyester fiber, the strength of the cord decreases and the adhesion with the rubber deteriorates due to hydrolysis of the ester bonds in the polyester due to the amine compounds generated from the vulcanization accelerator in the rubber and moisture. It has the drawbacks of being easily degraded, having poor chemical deterioration resistance, and having poor durability as a tire. In addition, its molecular structure has few functional groups, so its adhesion to rubber was low. Therefore, the adhesive treatment requires pretreatment with an epoxy or isocyanate adhesive, etc., and then treatment with a mixed solution of resorcinol-formalin first #J shrink metal and rubber latex, so-called RFL. A two-stage process with a low temperature was required.

Therefore, when used as carcass cords for bias tires for light trucks as well as high-earth tires for large trucks and lotus vehicles used under high-speed loads, there is a problem in that the durability of the tire is extremely low.

In particular, the carcass cords of bias tires, which are arranged in a mutually intersecting relationship, generate a large amount of heat due to the large shear strain between the carcass layers. In addition, there was a problem of low durability due to lack of adhesive deterioration resistance.

Therefore, at present, it is virtually impossible to use fiber cords made of the same material as carcass cords, from passenger cars with a small number of carcass plies to construction vehicles with a large number of carcass plies, in response to the required characteristics of tires. It was possible, and it was common to use them separately.

Moreover, with the development of motorization in recent years, the requirements for bias tires have become fairly severe. For example, with the advent of home delivery services, there is a strong demand for bias tires for light trucks and lotuses using polyamide fiber cords to have improved handling stability, lower noise, and reduced flat spot characteristics. There is a strong demand for fibers for carcass cords that have high modulus and glass transition temperature, as well as excellent adhesiveness, chemical deterioration resistance, and durability.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of conventional bias tires that use polyamide fiber cords or polyester fiber cords as carcass cords, and to provide excellent handling stability and durability as well as low noise. Our goal is to provide pneumatic bias tires.

[Structure of the invention]

The pneumatic bias tire of the present invention has a carcass layer composed of at least two layers as a bias tire, and fiber cords intersect between adjacent layers. Further, the fiber filaments constituting the fiber cord (carcass cord) are made of core-sheath type composite fibers having a polyester polymer as a core component and a polyamide polymer as a sheath component.

In the present invention, a bias tire refers to a tire having at least two carcass layers, with fiber cords (carcass cords) intersecting each other between adjacent layers. Generally, if the direction of the fiber cords of one carcass layer is +θ in the tire circumferential direction T, the direction of the fiber cords of the other carcass layer adjacent thereto is set to be 10. The angle θ of the fiber cord with respect to the tire circumferential direction T is preferably in the range of 20'' to 45'' with respect to the tire circumferential direction at the tire equatorial plane.

FIGS. 2(a) and 2(b) are views showing one example of a bias tire useful as a pneumatic bias tire of the present invention, particularly for trucks and light trucks. In the figure, 1 is a tread, 2-a, 2-b, 2-c
and 2-d are carcass layers each consisting of four layers, 3 is a belt layer, 4 is a sidewall, and 5 is a bead core.

The four carcass layers are constructed such that the fiber cords constituting these are sequentially +θ, −θ, They form angles of +θ and -θ and intersect between adjacent carcass layers. Each ply is a cross ply, forming a so-called structure advantageous in terms of casing rigidity.

In the present invention, a core-sheath type composite fiber has a core component C at the center of a single fiber cross section, which is surrounded by a sheath component S, as shown in FIG. It refers to something that has a similar shape in the long plane direction. The number of core components C present in the sheath component S may be one as shown in FIG. 1, or may be two or more.

In the carcass cord of the present invention, in such a core-sheath type composite fiber, the core component must be composed of a polyester polymer, and the sheath component must be composed of a polyamide polymer. This is because if a composite fiber in which the two types of combined components are arranged in the opposite manner is used as a carcass cord of a bias tire, it becomes impossible to simultaneously satisfy handling stability and durability. In other words, by covering the core component polyester polymer with a polyamide polymer as a sheath component, the polyester polymer with low adhesion is isolated from the rubber layer, and the polyamide polymer with good adhesion is always used. It can be brought into contact with the rubber layer, greatly improving the adhesion of fiber cords (carcass cords), preventing adhesive deterioration of polyester polymers, and having low chemical stability. Defects can be eliminated.

As the polyester polymer constituting the core component of the core-sheath type composite fiber, it is preferable to use polyethylene terephthalate, which is a typical polymer thereof, and has ethylene terephthalate as a repeating structural unit of the polymer chain. A polymer with a high degree of polymerization is applicable, and preferably polyethylene terephthalate has an intrinsic viscosity of at least 0.80 as measured at 25° C. using orthochlorophenol as a solvent. 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 p-oxybenzoic acid or a derivative thereof.

In addition, the polyamide polymer of the sheath component includes fiber-forming nylon 66 (polyhexamethylene adipamide), nylon 6 (polycaprolactam), nylon 46 (polytetramethylene adipamide), and copolymers thereof. Examples include merging. 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 determined to maximize the effect of improving the adhesion and chemical stability of the core component polyester polymer to rubber, and to increase the modulus of the polyester polymer as much as possible. It may be selected within a range that minimizes the decrease. This composite ratio is not particularly limited, but the core:sheath cross-sectional area ratio is 90:10 to 10.
:90, preferably 80:20 to 20:80, more preferably 70:30 to 30:0. If the ratio of the sheath component is too small and the core component is 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 polyamide polymer will become excessive, which will lower the initial modulus of the fiber cord and reduce the tire casing rigidity, resulting in decreased handling stability and tire noise. increase

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 made of the core-sheath composite fibers are converged and twisted to form a fiber cord (carcass cord). The twist given to this fiber cord is expressed as y:,=-rfte (in the above formula, K is the twist coefficient, T is the number of twists (twices/10cm), and D is the denier of the cord). The twist coefficient is preferably in the range of 1,000 to 3,000, preferably in the range of 1,400 to 2,400. When this twist coefficient becomes smaller than 1000, the convergence of the twisted cords decreases, and the initial adhesion strength decreases, as well as fatigue resistance decreases, and the durability of the tire having a carcass layer made of this cord decreases. do.

On the other hand, if the twist coefficient exceeds 3000, the initial modulus and strength of the cord will decrease significantly, leading to a decrease in the steering stability of the tire and an increase in noise.

This twisted fiber cord has an elongation rate of 6°5% or less when a load of 2.25 g/d is applied after adhesive treatment, and a dry heat shrinkage rate of 6.0z at 150°C. It is desirable to have the following. When the elongation rate of the adhesive-treated cord exceeds 6.5χ, the initial modulus as a fiber cord is too low, resulting in a decrease in steering stability as a tire.

In addition, if the dry heat shrinkage rate exceeds 6.0χ, the tire uniformity will deteriorate due to the shrinkage of the fiber cord during tire vulcanization, and the initial modulus of the fiber cord will decrease, reducing steering stability. do.

In the present invention, the number of fiber cords driven into the carcass layer varies depending on the type of tire, but usually 20 fiber cords are driven into the carcass layer.
It is recommended that the number be within the range of 70 pieces 15 cm, preferably 40 to 60 pieces 15 cm.

〔Example〕

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

In the examples, tire durability, handling stability, and noise characteristics were measured using the following methods.

Durability: In accordance with the "durability" test stipulated in JIS D 4230 r Automobile Tire J, an indoor high-speed durability test was conducted under the following conditions, and the total distance traveled until the tire broke was expressed as an index. did.

Tire size: 650-1510PR.

Rim: 15 x 5.50F.

Internal pressure: JATMA maximum air pressure 5.0Kg/cm".

Load: JATMA Design Regular Design Regular Load 97.

Speed: 81km/hr.

Drum diameter: 1707mm.

Performance - ◇ [Sensitivity] Evaluated by a real vehicle feeling test conducted by a professional driver, and expressed as an index value with the conventional example (conventional tire B) set at 100.

W sound characteristics: Measured in an anechoic chamber under the following conditions, and the noise difference during steady running at a speed of 60 km/hr is shown in dB.

Load: JATM 8 maximum 8 large load 970Kg: 15
X5.50F.

Internal pressure: 5.0Kg/cm2.

Examples, Conventional Examples Polyethylene telecrate is used as the core component, and nylon 6 is used as the core component.
6 as a sheath component, a composite ratio of 50150 in cross-sectional area ratio, and a total denier (D) of 15000. Two core-sheath type composite fiber filaments with a total denier (D) of 15000 were twisted together and twisted 40 times/
10cm, first twist 40 times/10cm, twist coefficient = 2191
A fiber cord was created. RFL (
After treatment with adhesive (resorcinol, formalin, rubber latex), a tension of 0.5 g/d was applied and the temperature was increased to 235°C.
The elongation rate under a load of 2.25 g/d was 4.
An adhesive treated cord having a dry heat shrinkage rate of 4.3χ at 150°C was prepared.

A green tire consisting of 4 carcass layers embedded in unvulcanized rubber was formed by driving 50 of these treated cords into a length of 15 cm, and vulcanization was performed to obtain a tire size of 650-1510.
I wanted to create a bias tire for PR's light trucks (hereinafter referred to as the tire of the present invention). The performance of the obtained tire of the present invention is shown in the table.

For comparison, as an example of a conventional bias tire, 15
A fiber cord with a twist coefficient of 2191 was created by aligning two 000 polyester fiber cords with an upper twist of 40 times/10 cm and a lower twist of 40 times/10 cm. After pre-treatment using "VALKABOND E", it was treated in two stages with the RFL, heat treatment temperature was 235℃, and the tension was 0.5g/d, and the elongation rate under heavy load was 2.25g/d@4. .4χ, 1
An adhesive-treated cord having a dry heat shrinkage rate of 3.6χ at 50°C was created. Enter this processing code and make 50 pieces 15cm
A green tire consisting of four carcass layers embedded in unvulcanized rubber was formed using vulcanization treatment to obtain a tire size of 650.
- A 1510P bias tire for light trucks was created (hereinafter referred to as conventional tire A).

Separately, pull two 12600 nylon 66 together and twist them 4 times.
0 times/10cm, first twist 40 times/10cm, twist coefficient = 2
A fiber cord of 008 was prepared. RF this fiber cord
The elongation rate under a load of 2.25 g/d was 8.
An adhesive treated cord having a dry heat shrinkage rate of 2.6χ at 150°C was created. I would like to form a green tire consisting of 4 carcass layers embedded in unvulcanized rubber by driving 50 of these treated cords and 15 cm each, and then vulcanize them to create a bias tire for light trucks with a tire size of 650-1510PR. (hereinafter referred to as conventional tire B).

The performance of these conventional tires A and B was evaluated and shown in the table.

Note: Both durability and handling stability are expressed as index values with the measured value of Conventional Example B as 100.

〔Effect of the invention〕

According to the present invention, by using a cord made of a core-sheath type composite fiber whose core component is a polyester polymer and whose sheath component is a polyamide polymer as a carcass cord, the characteristics of the carcass cord can be improved from those of the polyester fiber. While maintaining high initial modulus or stiffness equivalent to carcass cord, it has significantly improved chemical stability (deterioration) resistance and heat-resistant adhesion, improving the durability and handling stability of bias tires. Moreover, noise can be reduced. In addition, by having excellent adhesive properties as a carcass cord, it is possible to impart excellent adhesion to rubber with just one step of adhesive treatment using RFL, which simplifies the adhesive treatment process and simplifies tire production. can improve sexual performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the core-sheath composite fiber used in the present invention, FIG. 2(a) is a partially cutaway semi-perspective sectional view showing an example of the bias tire of the present invention, and FIG. 2(b) is It is a partially cutaway plan view showing the laminated structure of the carcass layer of the same tire. C...core component, S...sheath component, 1...tread,
2-a,'l-b,'lc and 2-d...carcass layer. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] A core comprising at least two carcass layers in which fiber cords cross each other between adjacent layers, and the fiber filaments constituting the fiber cords have a polyester polymer as a core component and a polyamide polymer as a sheath component. A pneumatic bias tire made of sheath-shaped composite fibers.