JP3307996B2 - Heavy duty pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic tire for an aircraft or the like.

[0002]

2. Description of the Related Art In general, safety is the first performance required for heavy duty pneumatic tires, particularly aircraft tires, but at the same time, economy is also required, and weight reduction of tires is required. . However, safety and weight reduction of tires are conflicting performances, and it is extremely difficult to achieve both.

Under such circumstances, nylon fibers have excellent strength, durability and heat resistance among cord materials for tire reinforcement, and therefore, nylon fibers are used for trucks and other vehicles, including aircraft.
It is widely applied to heavy duty pneumatic tires for buses, construction, etc. On the other hand, in order to reduce the weight of tires conventionally, we have responded by reducing the number of plies, and the shortage of the total strength of the plies was addressed by adopting a high strength ply reinforcement cord, Safety has been ensured. However, simply using a high-strength cord as a tire reinforcing cord, while ensuring the total strength of the ply, has led to a decrease in the bending rigidity and shear rigidity of the cord. As a result, when the tire rotates, a large compressive strain is applied to the cord at the stepped portion and the kick-out portion, so that the ply reinforcing cord may be fatigued and broken. Until now, in order to solve such a problem, when using a high-strength ply reinforcement cord, it is customary to increase the elasticity of the embedded rubber of the cord and reduce the strain applied to the cord. Was.

[0004]

In recent years, nylons having greatly improved strength as compared with conventional nylons have been developed (for example, Japanese Patent Application Laid-Open No. 61-70008), and the strength has been reduced even after vulcanization. A method of treating the rubber reinforcing cord with an adhesive which can be minimized has also been developed (for example, JP-A-2-91276), and the ply reinforcing cord can maintain a strength of 9.0 g / d or more in the tire. It became so.

However, the strength of the ply reinforcing cord is 9.
At 0 g / d or more, even if the embedded rubber is made to have high elasticity as described above, it is not possible to sufficiently reduce the strain on the cord, and this has been a major bottleneck in reducing the weight of the tire. Accordingly, an object of the present invention is to improve the high-speed durability and fatigue resistance of a ply reinforcing cord using ultra-high-strength nylon fibers to enhance the safety of a tire,
It is an object of the present invention to provide a heavy-duty pneumatic tire capable of further weight reduction.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies from the viewpoint of the compounding of the rubber embedded in the cord. The present inventors have found that the rubber in which the cord is embedded has an optimum sulfur content range and an optimum modulus range, and have completed the present invention.

That is, the present invention relates to a heavy-duty pneumatic tire reinforced with a polyamide fiber cord, wherein the strength of the polyamide fiber cord is 9.0 g / d or more, and the sulfur content of the rubber in which the cord is embedded. Is in the range of 1.0 to 4.0 parts by weight based on 100 parts by weight of the diene rubber, and the 100% modulus of the rubber is 25 to 60 k.
The present invention relates to a heavy-duty pneumatic tire having a g / cm ² range.

Hereinafter, the present invention will be described specifically. In the heavy duty pneumatic tire of the present invention, when the tire is a radial tire, the polyamide fiber cord according to the present invention is used for reinforcing a carcass ply and / or a belt ply. / Used for reinforcement of breakers.

The polyamide fiber cord used in the present invention may be of any type as long as it is an ultra-high strength cord having a cord strength of 9.0 g / d or more.
-Nylon, 6-nylon, 4,6-nylon, 6,1
Examples thereof include aliphatic polyamide fiber cords of 0-nylon and a copolymer or a mixture thereof in combination with 6,6-nylon or 6-nylon having 8%.
Aliphatic polyamide cords occupying 0% by weight or more are preferred, and 6,6-nylon cords of both are most preferred because of their high heat resistance. Further, the single-fiber fineness of this cord is preferably in the range of 3 to 8 denier.

In order to achieve the object of the present invention, such an ultra-high-strength polyamide fiber cord can prevent a decrease in strength at the time of adhesive treatment and vulcanization, and improve fatigue resistance under repeated compression strain. Preferably, an adhesive treatment is performed. Hereinafter, preferred examples of the resorcin-formaldehyde / rubber latex (so-called RFL) adhesive used for the adhesive treatment will be described.

That is, a preferred RFL adhesive is a resorcinol / formaldehyde total molar ratio (R / F), and a solids weight ratio (RF / L) of the total amount of resorcinol and formaldehyde to the total amount of rubber latex solids. ), Weight percent of alkali metal hydroxide (usually NaOH) or alkaline earth metal hydroxide based on total solids of RFL adhesive solution
(S), NH ₄ OH-based weight% of aqueous NH ₃ solution based on total solid content of RFL adhesive liquid (A), S + A, RF
Weight ratio of the total solid content of the L adhesive liquid (C), the solid content of vinylpyridine (VP) latex (normally VP content 5-20%) to the total latex solid content weight
(A), the weight ratio% of the solid content of styrene butadiene rubber (SBR) latex to the total latex solid weight (b), and the total latex solid content of the natural rubber (NR) and / or the solid content of isoprene rubber (IR) latex It is necessary that the weight ratio% (c) based on the weight per minute satisfies all of the following relationships.

1 / 2.3 ≦ R / F ≦ 1 / 1.1, preferably 1 / 2.0 ≦ R / F ≦ 1 / 1.3, more preferably 1 / 1.8 ≦ R / F F ≦ 1 / 1.5 (molar ratio), 0.05 ≦ S ≦ 0.8, preferably 0.1 ≦ S ≦ 0.5, more preferably 0.1 ≦ S ≦ 0.3 (weight %), 10 ≦ C ≦ 24, preferably 14 ≦ C ≦ 22 (% by weight), 10 ≦ a ≦ 80, preferably 30 ≦ a ≦ 60 (% by weight), 0 ≦ b ≦ 70, preferably 10 ≦ b ≦ 50 (% by weight), 20 ≦ c ≦ 60, preferably 25 ≦ c ≦ 50 (% by weight),

However, a latex other than those described above may be contained as the latex component, and SiO ₂ , carbon black, a boron compound and the like may be added. In performing the adhesive treatment of the polyamide fiber cord using the above-described RFL adhesive, the cord tension T when immersing the polyamide fiber cord in the RFL adhesive liquid is to achieve good penetration of the adhesive liquid into the cord. Preferably 0.2 g /
d or less, more preferably 0.1 g / d or less.

Next, the rubber embedded in the polyamide fiber cord will be described. It is important that the amount of sulfur contained in the embedded rubber according to the present invention be within the above range, and that the 100% modulus be within the above range.
If such conditions are satisfied, the compounding agent to other rubber compositions, for example, a vulcanization accelerator, a vulcanization accelerator, carbon black, a softening agent, an antioxidant, etc., in a usual amount of additives to be compounded. Of course, it can be added.
The structure of the heavy-duty pneumatic tire of the present invention is a structure known per se for aircraft, trucks and buses, construction, etc., and reduces the number of plies stacked, reduces the number of cords to be driven, and reduces the cord thickness. It is not necessary to change the structure at all, except that the tire is reduced in weight by reducing the thickness of the tire.

[0015]

The pneumatic tire for heavy loads according to the present invention requires the use of a polyamide fiber cord having a cord strength of 9.0 g / d or more as a cord for reinforcing the ply. When the strength is less than 9.0 g / d, the total cord strength of the entire tire when the number of plies is reduced is insufficient. For example, when the tire rotates at a high speed as in a state immediately before takeoff of an aircraft,
The tire may be broken. Therefore, in order to reduce the weight of the tire intended for the present invention, 9.0 g
/ D or more strength is required.

In the present invention, the amount of sulfur contained in the rubber in which the above-mentioned polyamide fiber cords are embedded is 100 or less.
It must be in the range of 1.0 to 4.0 parts by weight based on parts by weight. If the amount of sulfur is less than 1.0 part by weight, the rigidity of the rubber cannot be increased, and the ply reinforcing cord will be fatigued. On the other hand, when it exceeds 4.0 parts by weight, fatigue of the ultrahigh-strength polyamide fiber cord due to running is promoted, and the breaking strength of the ply reinforcing cord is greatly reduced.

Further, the buried rubber needs to have a 100% modulus of 25 to 60 kg / cm ² .
If this value is less than 25 kg / cm ² , the bending rigidity and the shearing rigidity are not sufficient, and even if the cord has excellent strength retention and fatigue resistance due to the RFL adhesive treatment as described above,
This leads to cord fatigue and tire destruction. On the other hand, in order to exceed 60 kg / cm ² , if the amount of sulfur is limited to 4.0 parts by weight as described above, increase the amount of carbon black or use carbon black having a small particle size. Heat generation increases, leading to a reduction in high-speed durability.

In the present invention, by using the above-mentioned rubber in combination with the above-described ultra-high-strength polyamide fiber cord as described above, it is possible to avoid the use of an ultra-high-strength polyamide fiber cord. The distortion can be reduced and the cord fatigue can be prevented. As a result, the high-speed durability and fatigue resistance of the cord are improved, and even if the weight of the tire is reduced by reducing the number of plies laminated, reducing the number of cords inserted, and making the cord thinner, the safety of the tire can be improved. Thus, a heavy-duty pneumatic tire that achieves both weight reduction and safety without loss of performance is obtained.

[0019]

Next, the present invention will be described in detail with reference to examples. As a fiber cord for reinforcing a ply of a pneumatic tire for heavy load, a high-strength 6,6-nylon having an original yarn strength of 10.0 g / d was used in Comparative Example 1, and an original yarn strength of 12.2 was used in other Comparative Examples and Examples. Ultra-high strength 6,6-nylon of 0 g / d was used in a twisted structure of 1260 d / 2 (39 × 39 times / 10 cm).

The RFL adhesive solution in this example and the comparative example was prepared by dissolving resorcinol in soft water and then adding NaO
H aqueous solution was added, then formalin was added, and the mixture was aged at room temperature for 6 hours. Then, an NH ₃ aqueous solution was added, latex was added, and the mixture was further aged at room temperature for 24 hours. Was. The content of the adhesive liquid is as follows.

[0021]

The content of the adhesive solution is the same as that described above, which is suitable for the present invention, ie, resorcinol /
It satisfies all the above-mentioned relations with respect to the molar ratio of the total amount of formaldehyde (R / F) and the solid weight ratio of the total amount of resorcinol and formaldehyde to the total amount of rubber latex solids (RF / L, etc. The temperature, exposure time, and cord tension conditions of the drying zone, hot zone and normalizing zone in the drying heat treatment after immersion in the adhesive liquid were set as follows.

Drying zone: 130 ° C. × 120 seconds × 0.8 g / d Hot zone: 235 ° C. × 40 seconds × 0.8 g / d Normalizing zone: 230 ° C. × 40 seconds × 0.5 g / d

Each of the obtained processing codes has a size AP
It was used for reinforcing the ply of SH44.5 × 16.5-2026PR tires, and in Comparative Examples and Examples, the number of such plies was reduced by two with respect to Comparative Example 1. When the weight of the tire at this time is represented by an index by taking the tire of Comparative Example 1 as 100, it becomes 90 as shown in Tables 1 and 2 below. The compounding composition (parts by weight) of the rubber embedded in the cord is as shown in Tables 1 and 2.

The 100% modulus of the cord embedded rubber, the breaking strength of the ply reinforcing cord, the weight reduction of the tire, the high-speed durability of the tire and the fatigue resistance of the cord were measured as follows. 100% modulus of cord embedded rubber From a rubber sheet of about 0.2 mm thickness cut out from a vulcanized tire, S3A specified in DIN-53504
Create a dumbbell-shaped sample using a blade of the size,
Pull at a pulling speed of 100 mm / min at room temperature,
The stress when the strain of the parallel portion of the sample became 100% was determined. Breaking strength First, after taking out the ply reinforcing cord from the tire after vulcanization, a tensile test was performed using an autograph manufactured by Shimadzu Corporation in accordance with JIS L1017, and the strength at break (k
g) was determined. For the cord in the tire after vulcanization, 10 filaments were extracted from the collected cord, the diameter of each filament was determined using an optical microscope, and the cross section was regarded as a perfect circle from the average filament diameter. The cross-sectional area was determined. From this and the total number of filaments counted by observing the cross section, the volume per length is simply determined, and this is simply converted into the weight per length (denier) using the density ρ = 1.14, and the estimated denier number is calculated. Was calculated, and the strength was calculated according to the following equation. Strength (g / d) = breaking strength / estimated denier

Degree of Lightening of Tire With reference to Comparative Example 1, other Comparative Examples and Examples reduced the number of such plies by two. At this time, Comparative Example 1
The weight of each of the other comparative examples and examples was represented by an index, with the weight of the sample taken as 100. The smaller the value, the lighter the weight. High-speed durability of tire When the speed was increased from 0 to 225 MPH every 60 seconds at a load of 39600 LBS and an internal pressure of 12.7 kg / cm ² , the time until the tire was broken was measured.
And 100 as an index. The higher the value, the better the result. Fatigue Resistance of Cord The time until the cord was broken was measured at a load of 39600 LBS, an internal pressure of 12.7 kg / cm ² and a speed of 40 MPH, and the index was indicated as an index with Comparative Example 1 being 100. The higher the value, the better the result. The obtained results are shown in Tables 1 and 2.

[0027]

[Table 1]

[0028]

[Table 2]

In the table, 1) N-phenyl-N'-isopropyl-p-phenylenediamine 2) N-tert-butyl-2-benzothiazolesulfenamide

[0030]

As described above, the pneumatic tire for heavy load according to the present invention has the strength of an ultra-high-strength polyamide fiber cord for reinforcing a ply, the sulfur content of rubber embedded with the cord and the 100% modulus. Is set in the optimum value range, the high-speed durability and fatigue resistance of the ply reinforcing cord are improved, and the weight of the tire can be reduced without impairing the safety of the tire. Therefore, for example, it is extremely useful as a pneumatic tire for aircraft.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 9/00-9/08 B60C 9/18-9/20

Claims (1)

(57) [Claims] 1. A heavy-duty pneumatic tire reinforced with a polyamide fiber cord, wherein the polyamide fiber cord has a strength of 9.0 g / d or more, and the rubber in which the cord is embedded has a diene rubber. It is in the range of 1.0 to 4.0 parts by weight per 100 parts by weight, and the 100% modulus of the rubber is 25 to 60.
A heavy-duty pneumatic tire characterized by being in the range of kg / cm ² .