JP2000303290A - Reinforcing cord for vibration absorption rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject cord maintaining a high modulus of elasticity of reinforcing material, imparting high performance of the reinforcing material, properly constituting the reinforcing material and improving steering stability, suitable for a tire cord or the like by making the cord have a specific cord strength, a specified load elongation and a prescribed loss tangent. SOLUTION: This cord for rubber reinforcement is obtained by twisting raw threads such as polyethylene naphthalate-based threads, acrylic threads or the like and dipping treatment. The cord has >=4.2 cN/dtex cord strength, <=4.0% elongation under 1.75 cN/dtex load and >=0.06 loss tangent (tanδ) observed by a dynamic viscoelasticity measurement at 70 deg.C, 35 Hz. This reinforcing cord for vibration absorption rubber preferably has >=90% adhesive strength retention after over-vulcanization at 170 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber cord suitable for rubber reinforcement, and more particularly to a fiber cord having improved vibration absorption and suitable for rubber reinforcement such as tire cords and V-belts. Provide code.

[0002]

2. Description of the Related Art Polyester high-strength yarns represented by polyester tire cords are organic fibers having an excellent balance in physical properties and cost, and are widely and widely used as fibers for industrial materials.

[0003] Above all, the tire structure of automobile tires, especially passenger car tires, has become more and more radial, and it is required that the tires be excellent in ride comfort and driving stability during high-speed running and light in weight for fuel economy. Therefore, high strength and high elastic modulus characteristics are strongly required as tire reinforcing fibers.

However, it is a fact that rayon fiber cord is still used as a carcass material for such a radial tire, for example.

Further, nylon 66 is used in an outer layer region of a belt portion called a cap ply of a tire.

There is a reason that each material is properly used in each place. However, none of the materials is satisfactory at present, and improvement is always required.

[0007] For example, rayon cords basically have low strength, and therefore, in order to be used as a rubber reinforcing material, it is necessary to use thicker cords or to overlap a plurality of reinforcing layers.

This not only increases the cost of the cord itself, but also increases the thickness of the rubber-fiber composite, thereby increasing the weight of the composite itself and driving the driving means itself such as tires and driving belts. The amount of energy required for this increases, and the environmental burden increases.

Nylon 66 fiber has a high fiber strength and does not cause the above-mentioned problems of rayon cords, but basically has a low elastic modulus. There has been a problem that the dynamic elastic modulus is relatively low, and the response to driving (for example, steering stability for tires) is low.

[0010] Such a high elastic modulus has been demanded for the purpose of increasing the rigidity of other members, for example, in applications such as a tire cap ply. Because of the possibility, nylon 66 having high heat resistance at the bonded portion was often used.

In spite of cost and weight increase, the combined use of rayon, nylon 66, and steel tires is still being used as a luxury car tire. In addition, the overall performance such as steering stability and ride comfort is excellent. Under the above circumstances, in the case of tires, the balance between steering stability and ride comfort, and in belts and the like, it is necessary to prevent the mechanical load from increasing due to unnecessary vibration or to prevent unnecessary noise. There is a need for reinforced rubber materials.

In order to solve the above-mentioned problems, we decompose the above-mentioned problems into individual factors, sort and analyze the necessary characteristics for each, and then determine the necessary characteristics from the molecular level of the reinforcing fiber. After reviewing and reverting to the components as reinforcement cords, we tried to consider countermeasures.

[0013] The steering stability of the tire and the driving response of the drive belt can be basically improved by increasing the elastic modulus of the reinforcing material. Examples include polyethylene terephthalate (PET) fiber, rayon, aramid fiber, and PBO fiber. It is clear from the preference that is used.

On the other hand, for ride comfort and vibration suppression,
Basically, it is considered that a large contribution is made by dissipating a part of the energy absorbed by the rubber portion as heat.

However, it is not so simple in practice. For example, if PET is replaced with aramid to increase the rigidity, the vibration absorption of the composite is reduced, resulting in a poorly balanced material. On the other hand, it has been empirically known that, although rayon has a higher elastic modulus than PET fiber or the like, the vibration absorption of the composite is not so bad.

That is, generally speaking, if the elastic modulus of the reinforcing material is increased, the vibration absorption is reduced, but the order can be easily reversed depending on the material.

Such a phenomenon is more remarkable particularly in the field of radial tires because the flatness of the tire is increased for the purpose of improving steering stability and the internal pressure of the tire is increased accordingly. It seems to have appeared in.

Such a point is described, for example, in JP-A-10-2
In 97211, the relationship between the dynamic viscoelastic properties of the carcass cord of a pneumatic tire and the steering stability of a motorcycle was investigated.
It has been proposed that a tire having excellent steering stability can be manufactured by using a cord having a dynamic elastic modulus and a loss tangent within a specific range.

In the above invention, the invention is realized by defining the structure of the aramid cord in a specific range. As described above, although the steering stability is improved, the vibration absorption as a composite is improved. Therefore, the vibration absorption is not sufficient in a motorcycle such as a relatively high-end passenger car or a V-belt, which is the purpose of the present application, aside from a motorcycle. It cannot be a substitute material.

[0020]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, to maintain the elastic modulus of the reinforcing member at a high level, to improve the basic performance as a rubber reinforcing member, and to further improve the structure of the reinforcing member. It is an object of the present invention to provide a rubber reinforcing cord in which the vibration absorption of a fiber-reinforced rubber material is improved by optimizing the rubber reinforcing cord.

[0021]

Means for solving the above problems, ie, a first aspect of the present invention is a rubber reinforcing cord obtained by twisting and dipping a raw yarn fiber, and having a cord strength of 4%. 0.2 cN / dtex or more, 1.75 cN / dte
x elongation under load is 4.0% or less, and loss tangent (tan δ) at 70 ° C. in dynamic viscoelasticity measurement at 35 Hz
The fiber cord for reinforcing a vibration-absorbing rubber according to claim 1, wherein the fiber cord is 0.06 or more, and the second fiber is a polyethylene naphthalate-based fiber. The third is the vibration-absorbing rubber reinforcing fiber cord according to claim 1, wherein the raw yarn fibers are acrylic fibers, and the fourth is that the adhesive force retention rate after overvulcanization treatment at 170 ° C. is 90%. % Or more.

In the present invention, the cord strength is 4.2 cN.
/ Dtex or more is indispensable as the basic performance of the reinforcing material. If it is less than / dtex, the thickness of the cord layer becomes large, and as a result, the total weight of the fiber reinforced rubber material becomes large, and the driving force of a tire, a driving belt, The amount of energy required to drive the means itself increases, and the environmental load increases.

The elongation under load of 1.75 cN / dtex is 4.
A value of 0% or less indicates that the cord has a high modulus of elasticity, and is necessary for forming a fiber reinforced rubber material having excellent responsiveness. High performance rubber materials cannot be expected.

The most important feature of the present invention is that it has high strength and high elastic modulus as described above, and also has a loss tangent (t) at 70 ° C.
an δ) is 0.06 or more. The loss tangent is 0.
When it is at least 06, a rubber reinforcing fiber cord which is excellent in vibration absorption balance with a rubber material and extremely excellent in vibration absorption as a composite material can be provided.

However, in the case of the fiber cord having a high loss tangent as described above, not only rubber but also rubber,
Since the energy absorption and heat dissipation of the fiber cord itself increase, the temperature rise of the fiber cord itself becomes a nonnegligible level. At this time, it is known that, particularly in a bonding interface region with the rubber, the load is particularly large, so that the bonding failure is increased.

Therefore, by providing the strength, elastic modulus, and loss tangent as in the present invention, there is provided a fiber cord for rubber reinforcement which basically maintains high performance as a composite material and is excellent in vibration absorption. Although it is possible, it is more preferable that the adhesive strength retention after the overvulcanization treatment at 170 ° C. is 90% or more.

Examples of such a material constituting the fiber cord include polyethylene naphthalate fiber and acrylic fiber.

Polyethylene naphthalate (PEN) fiber is known as a high-strength, high-modulus fiber. For example, P. Rim, Rubber World, November 1995, 23, etc., describe excellent properties as a tire cord. I have. Above all, by using the high elastic modulus of the material, even if the number of twists of the cord is increased, sufficient cord elastic modulus can be obtained, so that it shows higher fatigue resistance than polyethylene terephthalate etc. I have.

However, the cord shown here has a very high modulus of elasticity of 3.5 g / d or less at 3% elongation corresponding to the modulus of elasticity (1.75 cN / dt).
(elongation under ex load is 1.7% or less). In such a region, the elongation of the constituent molecular chains is extremely high, the molecular motion is extremely reduced, and the loss tangent at 70 ° C. is reduced. It does not become a fiber cord excellent in vibration absorption as in the invention.

Regarding this point, for example, Nagai et al. (Chemicals Journal, 51,478 (1997)) subject the as-spun yarn of PEN made of β-type crystal to a tension heat treatment to reduce the loss tangent. It is clear from the matter.

Therefore, when polyethylene naphthalate fiber is used in the present invention, 1.75 cN / dtex
The elongation under load is more preferably 2.0% or more.

By the way, when PEN fiber is used,
Since the chemical stability of the material itself is superior to that of PET, etc., the decrease in adhesive strength when heated is hardly a problem.
Rather, the main focus is on how to improve the initial adhesive strength (improving the absolute value of the adhesive strength), but this is a problem relating to the entire polyester fiber, and the method is not particularly limited.

On the other hand, when an acrylic fiber is used as a material constituting the present invention, the acrylonitrile ratio is preferably 95% or more in order to constitute a high-strength and high-modulus fiber. In view of the heat resistance of the above, it is more preferable that substantially 100% be made of acrylonitrile.

In order to improve the resistance to moist heat, crosslinking may be introduced as long as the strength is not significantly reduced.

An example in which an acrylic fiber is used as a fiber cord for reinforcing rubber is disclosed, for example, in JP-A-10-44251.
Discloses a technique of a rubber composite using high-strength acrylic fiber.

Here, the elongation under load of 2.25 g / d is 2.
Experimental examples of 7-3.2% are disclosed. This is considered to be equivalent to about 2.4 to 2.8% in terms of the elongation under load of 1.75 cN / dtex (up to 2 g / d) specified in the present invention. It is presumed that the configuration makes use of the characteristics, particularly the high elastic modulus.

In the case of the acrylic fiber, the viscoelastic characteristic has a main dispersion at around 100 to 110 ° C., and the absolute value of the PEN fiber (β dispersion) is higher than that of the acrylic fiber. Even if the loss tangent peak decreases due to the high elastic modulus, the effect is small, but the loss tangent at 70 ° C., which is considered to have a large effect on the performance as a product, may be reduced to an undesirable range. There is.
Therefore, in this case as well, an increase in the elastic modulus more than necessary lowers the vibration absorption, particularly 1.75 cN / dt.
ex load elongation is preferably 2.0% or more,
More preferably, it is 3.0% or more.

When the acrylic fiber is applied to the present invention, there is no particular problem in the retention of adhesive force when heated due to the chemical stability of the material and the adhesiveness to rubber. In the case of applying at a temperature of 130 ° C. or less, the moisture content is at most 2% or less, preferably 1% or less,
If not sufficiently dried, the cord will break due to the tension in the heat setting process.

On the other hand, the processing temperature of the heat setting step and the normalizing step is required to be 180 ° C. or higher in order to improve dimensional stability and to obtain a sufficient adhesive force with rubber. It is preferable that the temperature is not lower than ° C. 18
At a processing temperature of 0 ° C. or lower, the shrinkage of the cord increases and the adhesive strength decreases, which is not preferable. As described above, if 2% or more of moisture is introduced into this step, cord breakage will occur. In addition, when the treatment is performed at 200 ° C. or more for a long time, a cyclization reaction occurs between adjacent nitrile groups to form a condensed pyridine ring, and at this time, cyan gas is generated, which is dangerous and requires attention.

As described above, it is necessary to pay attention to the technical points when PEN fiber and acrylic fiber are used in the present invention, but in order to obtain a fiber cord excellent in vibration absorption in the present invention. It is easily analogized that it will be realized by a composite code or the like in combination with other materials or with other materials, and even if a material other than the above materials is used, if the code characteristics defined in the present application are obtained,
It goes without saying that the object of the present invention is achieved.

[0041]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. In addition, the evaluation method of various characteristics followed the following method.

Fineness: 20 according to JIS-L1017
After leaving for 24 hours in a room where the temperature and humidity were controlled at 65 ° C. and 65% RH, the fineness was measured. However, drying was not performed again at the time of measurement.

Strong elongation: 24 hours in a room where the temperature and humidity are controlled at 20 ° C. and 65% RH according to the definition of JIS-L1017.
After standing for a period of time, the tensile strength, breaking elongation,
1.75 cN / dtex elongation under load was obtained.

Loss tangent at 70 ° C .: Using a dynamic viscoelasticity measuring device manufactured by Iwamoto Seisakusho, sample length 3 cm, initial load 1 kg
f, the loss tangent was measured at a rate of 5 ° C./min from room temperature at a frequency of 35 Hz and a strain of 3%, and a measured value at 70 ° C. was obtained.

Adhesive strength retention: Adhesive strength is evaluated by an H test modified from the T test (Method A) of JIS-1017. After embedding the treated cord in rubber for 1 cm length, and vulcanizing at 140 ° C. for 40 minutes and 170 ° C. for 180 minutes, the force required to pull out the cord from the rubber at 300 mm / min is obtained in N units. I asked for it. Adhesive force retention [%] = (adhesive force at 170 ° C. × 180 minutes) / (adhesive force at 140 ° C. × 40 minutes) × 100

[0046]

Examples 1 to 3 and Comparative Examples 1 to 5 Various fibers as shown in Table 1 were treated under the conditions shown in Table 2 to obtain cords.
Table 3 shows the code characteristics. The vibration absorption was determined in the tube fatigue test measurement according to JIS-L1017 from the equilibrium temperature of the tube surface temperature in comparison with the case of rayon cord.

From these results, it can be seen that when the fiber cord has a higher loss tangent at 70 ° C. than the rayon cord while maintaining the basic performance as a rubber reinforcing material and satisfying the strength and the elastic modulus, the heat generation of the tube is caused. Is large, and the vibration energy is well dissipated as heat.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

By using the fiber cord of the present invention, it is possible to provide a fiber cord which is excellent in vibration absorption in addition to the characteristics conventionally required for a rubber reinforcing material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanao Kobashi 10-24, Toyocho, Tsuruga-shi, Fukui Prefecture Toyobo Co., Ltd. Inside Tsuruga Plant (72) Inventor Shuji Chiba 10-24, Toyocho, Tsuruga-shi, Fukui Prefecture Toyobo Co., Ltd. Tsuruga Factory F-term (reference) 4L036 MA04 MA05 MA33 PA18 PA26 RA24 UA25

Claims (4)

[Claims] 1. A rubber reinforcing cord obtained by twisting and dipping a raw yarn fiber and having a cord strength of 4.2c.
Elongation under load of not less than N / dtex and 1.75 cN / dtex is not more than 4.0%, and loss tangent (tan δ) at 70 ° C. is not less than 0.06 in dynamic viscoelasticity measurement at 35 Hz. Fiber cord for vibration-absorbing rubber reinforcement characterized by the following 2. The fiber cord for reinforcing a vibration-absorbing rubber according to claim 1, wherein the raw fiber is a polyethylene naphthalate fiber. 3. The fiber cord for reinforcing a vibration-absorbing rubber according to claim 1, wherein the raw yarn fiber is an acrylic fiber. 4. The fiber cord for reinforcing a vibration-absorbing rubber according to claim 1, wherein an adhesive strength retention rate after overvulcanization treatment at 170 ° C. is 90% or more.