JP2906293B2 - 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 improves durability (suppression of heat generation in a tread portion during running), crack resistance (prevention of cracks at the groove bottom on the tread surface), and abrasion resistance of the tread portion. Heavy-duty pneumatic tires.

[0002]

2. Description of the Related Art Heavy-duty tires for trucks and buses have long been required to have a long service life. To solve this problem, use of a tread rubber compound for improving abrasion resistance and groove depth on the surface of the tread portion have been demanded. Directions for increasing the size have been considered. The latter is mainly for securing traction over a long period of time at the drive shaft of the vehicle.

[0003] In this tire (hereinafter referred to as a deep groove tire), cracks due to fatigue often occur at the bottom of the groove of the block on the surface of the tread portion, and the appearance and the rehabilitation of the tire may be significantly impaired. For this reason, in general, the rubber compound (rubber composition) constituting the tread portion is blended with polybutadiene to provide the tread portion with fatigue resistance.
(Crack resistance). For example, Smithers Report (OCTOBER, 1987, TIRE ANALYSI
S, REPOPT) includes GY.G belonging to the category of this deep groove tire.
167, on the incorporation of polybutadiene. However, the combination of polybutadiene can improve fatigue resistance and wear resistance, but on the other hand, the hardness and modulus are reduced, and the tire tread portion during running,
In particular, step wear between blocks due to an increase in movement at the block portion, so-called uneven wear, occurs.

[0004] In order to cope with this, increasing the amount of carbon black is a general method. By increasing the amount of carbon black, the hardness and modulus are increased, and the rigidity of the tread portion is improved. Can be improved. In addition, an increase in the amount of carbon black increases the heat generation term and increases the hysteresis loss, so that crack resistance against distortion during running is improved, and both abrasion resistance and crack resistance can be achieved. However, the rise in heat increases the effect on the internal parts during running, eventually causing separation between the tread and the belt layer, making it incompatible with durability and extending the life of the tire. Will not fit.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been developed in view of the fact that a rubber composition containing a specific polybutadiene (butadiene polymer) is used to constitute a tread portion. It is an object of the present invention to provide a heavy-duty pneumatic tire having improved durability, crack resistance, and wear resistance.

[0006]

The heavy duty pneumatic tire of the present invention has a trans-1,4 bond content of 70 to 95% by weight.
Butadiene polymer, and at its active end,
N-substituted aminoketone, N-substituted thioaminoketone, N
-Substituted aminoaldehyde, N-substituted thioaminoaldehyde, or a compound of the general formula

[0007]

(Wherein M represents an oxygen or sulfur atom)
20 to 69 parts by weight of a terminal-modified butadiene polymer (A) obtained by reacting at least one compound selected from compounds having an atomic group represented by the following, and 80 to 31 parts by weight of the other diene rubber (B) The tread portion is made of a rubber composition containing a rubber component and a rubber component as a rubber component. Less than,
The configuration of the present invention will be described in detail.

The pneumatic tire for heavy load according to the present invention comprises a carcass layer disposed over a pair of beads, a belt layer disposed on a crown of the carcass layer, an annular tread, and the tread. And a pair of side portions communicating from both ends of the tread portion, respectively, and a groove is provided on the surface of the tread portion. The tread portion is composed of a rubber composition containing the following terminal-modified butadiene polymer (A) and another diene rubber (B) as rubber components.

A butadiene polymer having a trans-1,4 bond content of 70 to 95% by weight and having an N-substituted aminoketone, an N-substituted thioaminoketone, an N-substituted aminoaldehyde N-substituted-thioaminoaldehyde, or a general formula in the molecule:

[0011]

Wherein M represents an oxygen or sulfur atom
A terminal-modified butadiene polymer (A) obtained by reacting at least one compound selected from compounds having an atomic group represented by The butadiene polymer used here is a polybutadiene having a high trans bond content of 70 to 95% by weight in the trans-1,4 bond content.

When the content of the trans-1,4 bond is less than 70% by weight, both the breaking strength and the abrasion resistance decrease. Such a butadiene polymer having a high trans-1,4 bond content is:
Butadiene can usually be obtained by polymerization using a composite catalyst containing an alkaline earth metal, but it is difficult to obtain one having a trans-1,4 bond content of more than 95% by weight. The preferred trans-1,4 bond content is 75
~ 95% by weight.

The above compounds used in the terminal modification reaction include, for example, 4-dimethylaminobenzophenone,
-Diethylaminobenzophenone, 4-di-t-butylaminobenzophenone, 4-diphenylbenzophenone, 4,4'-bis (dimethylamino) benzophenone,
4'-bis (diethylamino) benzophenone, 4,4'-bis (di-t-butylamino) benzophenone, 4,4'-bis (diphenylamino) benzophenone, 4,4'-bis
N-substitution such as (divinylamino) benzophenone, 4-dimethylaminoacetophenone, 4-diethylaminoacetophenone, 1,3-bis (diphenylamino) -2-propanone, 1,7-bis (methylethylamino) -4-heptanone Aminoketones and corresponding N-substituted aminothioketones; N-substituted aminoaldehydes such as 4-dimethylaminobenzaldehyde, 4-diphenylaminobenzaldehyde, 4-divinylaminobenzaldehyde and corresponding N-substituted aminothioaldehydes; -Methyl-β-propiolactam, Nt-butyl-β-propiolactam, N-phenyl-β-propiolactam, N-methoxyphenyl-β-propiolactam, N-naphthyl-β-propiolactam Lactam, N-methyl-2-pyrrolidone, Nt-butane Tyl-2-pyrrolidone, N-phenyl-pyrrolidone, N-methoxyphenyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-
Benzyl-2-pyrrolidone, N-naphthyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, N-
t-butyl-5-methyl-2-pyrrolidone, N-phenyl-5-methyl-2-pyrrolidone, N-methyl-3,3'-
Dimethyl-2-pyrrolidone, Nt-butyl-3,3'-dimethyl-2-pyrrolidone, N-phenyl-3,3'-dimethyl-2-pyrrolidone, N-methyl-2-piperidone, N
-T-butyl-2-pyrrolidone, N-phenyl-2-piperidone, N-methoxyphenyl-2-piperidone, N
-Vinyl-2-piperidone, N-benzyl-2-piperidone, N-naphthyl-2-piperidone, N-methyl-3,
3'-dimethyl-2-piperidone, N-phenyl-3,3'-
Dimethyl-2-piperidone, N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methoxyphenyl-ε-caprolactam, N-vinyl-ε-
Caprolactam, N-benzyl-ε-caprolactam,
N-naphthyl-ε-caprolactam, N-methyl-ω-
Laurylolactam, N-phenyl-ω-laurylolactam, Nt-butyl-laurylolactam, N-vinyl-
N-substituted lactams such as ω-laurylolactam, N-benzyl-ω-laurylolactam and their corresponding thiolactams; 1,3-dimethylethylene urea, 1,3-
Examples include N-substituted ethylene ureas such as diphenylethylene urea, 1,3-di-t-butyl ethylene urea, and 1,3-divinyl ethylene urea, and corresponding N-substituted thioethylene ureas.

A diene rubber (B) other than the above-mentioned terminal-modified butadiene polymer (A). Examples of the diene rubber (B) include natural rubber (NR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), and acrylonitrile-butadiene copolymer rubber (NBR). It is preferable to use natural rubber (NR), styrene-butadiene copolymer rubber (SBR), or polyisoprene rubber (IR) generally used for tire treads.

The rubber composition used in the present invention contains 20 to 69 parts by weight of the terminal-modified butadiene polymer (A) and 80 to 31% by weight of the diene rubber (B) as a rubber component. If the amount of the terminal-modified butadiene polymer (A) is less than 20 parts by weight, a sufficient improvement in fatigue resistance represented by crack resistance at the groove bottom cannot be expected. On the other hand, if it is 70 parts by weight or more, sufficient durability and tread portion strength cannot be exhibited as a heavy duty tire, and problems such as cutting and chipping occur.

In addition to the rubber component, carbon black,
Zinc oxide, stearic acid, natural resins, synthetic resins, antioxidants, plasticizers, vulcanizing agents such as sulfur, vulcanization accelerators and the like can be appropriately contained.

[0018]

EXAMPLES Rubber compositions were prepared according to the compounding contents (parts by weight) shown in Table 1 (Examples 1 to 4 and Comparative Examples 1 to 7). These rubber compositions were kneaded, and the vulcanized rubber obtained by vulcanizing at 148 ° C. for 30 minutes was measured for the breaking strength (kg /
cm ² ), elongation at break (%), 300% modulus (kg / cm ² ), J
IS hardness, abrasion resistance, heat build-up, and crack resistance were measured and evaluated. Table 1 shows the results.

Breaking strength, breaking elongation (%), 300% modulus
Lath and JIS hardness : Measured at room temperature (25 ° C.) according to the method specified in JIS K6301. Abrasion resistance : A value measured using a Lambourn abrasion tester at a slip ratio of 25%. It was indicated by an index using the measured value of Comparative Example 1 as a reference (100). The greater the index value, the better the wear resistance.

Heat generation property : A sample having a length of 30 cm, a width of 5 mm and a thickness of 2 mm was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd.
Initial tensile strain 10%, dynamic strain ± 2%: frequency 20Hz, temperature 60 ° C
The calorific value was measured under the following conditions. The measured value of Comparative Example 1 was shown as an index with reference (100). The larger the index value, the greater the heat generation.

Crack resistance (fatigue resistance) : Using a Demasher type fatigue tester, width 20 mm, length 150 m
After a 1 mm cut was made in a strip sample having a thickness of 2 mm and a thickness of 2 mm, the cut growth rate when a dynamic fatigue of 20% strain was given was measured. Obtain the reciprocal of this measured value, and refer to the value of Comparative Example 1.
(100). The larger the index value, the better the crack resistance.

Also, using the above rubber composition, 11R 22.5 1
Four-ply tires were fabricated and evaluated for indoor heat generation durability by the method described below. Table 1 shows the results. Indoor heat generation durability : The tire was run for a certain period of time under JATMA standard conditions, the temperature of the third belt edge of the tire at that time was measured, and the reciprocal of the numerical value was indexed. The higher the index (100 or more), the lower the heat generated during running, which is advantageous for the durability during running of the tire.

[0023]

Note) * 1 Nippon Zeon, polybutadiene rubber, 98% cis, 1% trans, 1% vinyl. * 2 Nippon Zeon, polybutadiene rubber, transformer 91
%, N-methyl-ε-caprolactam reacted at the active end. * 3 N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine. * 4 N-tert-butyl-benzothiazolesulfenamide. * 5 Breaking strength. * 6 Elongation at break. In Table 1, Comparative Examples 1 to 5 are common high-cis polybutadiene (Nipol BR1220) as a tread rubber composition.
Is an example in which is varied.

Comparative Examples 6 and 7 and Examples 1, 2, 3, and 4
Is trans instead of high cis polybutadiene.
-BR was varied from 20 parts by weight to 70 parts by weight, and polybutadiene fatigue resistance with 100 parts by weight of natural rubber (NR)
(Index) shows a value of 100 or more when the polybutadiene is 30 parts by weight or more, indicating that the effect of improving crack resistance is large. The effect of improving fatigue resistance (index) was
It can be seen that it is larger with the R composition.

The abrasion resistance (index) was measured with a Lambourn type abrasion tester, and as shown in Comparative Examples 1 to 5, the increase in the amount of polybutadiene (30 parts by weight or more) showed a value of 100 or more. Is shown. Examples in which trans-BR was blended are shown in Comparative Examples 6 and 7, and Examples 1, 2, 3, and 4. Trance
It can be seen that the effect of improving the abrasion resistance (index) is greater in the case where -BR is blended than in the case where ordinary Hicis-BR is used.

The exothermicity represented by tan δ at 60 ° C. generally shows a tendency to decrease when BR is blended (Comparative Examples 1, 2, 3). However, when the BR content was further increased, the heat buildup tended to increase as shown in Comparative Examples 4 and 5, and there was no clear improvement effect. Meanwhile, transformer-BR
When the amount is increased and the amount is increased, Comparative Examples 6, 7,
As shown in Examples 1, 2, 3, and 4, the exothermicity tends to clearly decrease.

In general, when Hycis-BR is blended, as shown in Comparative Examples 1 to 5, the modulus and hardness tend to decrease as the blending amount increases. Therefore, when these rubber compositions are used in the tire tread portion, since the deformation of the tire tread portion increases due to the decreasing modulus and hardness, the heat generation and the temperature rise of the tire under the constant load deformation during traveling are increased. It does not decrease and the tire durability does not improve (Comparative Examples 1 to 5).

When the deformation of the tread portion becomes large during running, especially in a tire such as a block pattern having a deep groove, the strain applied to the bottom of the groove increases, and the heat generation / Crack resistance / abrasion resistance cannot be achieved at the same time. On the other hand, when increasing the amount of trans-BR in place of the above-mentioned high cis-BR, the modulus does not decrease compared to Comparative Example 1, and the blending amount of the trans-BR in both hardness and modulus is from 20 parts by weight to 70 parts by weight. When the amount is less than the part, the value is particularly improved with respect to Comparative Example 1.

The fact that the above modulus, especially the hardness, does not decrease even when the BR compounding amount is increased means that when these rubber compositions are used in the tire tread portion, the deformation of the tread portion does not increase. Under constant load deformation, the deformation of the tread portion becomes small and the heat generation decreases.
This is supported by tire interior durability data (index values).

Looking at Table 1 in detail, the trans-BR
At 70 parts by weight, the modulus is lower and the hardness is lower than in Example 3. Therefore, the upper limit of the amount of trans-BR is less than 70 parts by weight. The lower limit of the amount of the trans-BR compound can be determined to be 20 parts by weight from the index values of wear resistance and fatigue resistance. From these, the amount of trans-BR in the rubber composition for treads of pneumatic tires was 20%.
It turns out that it is more than 70 weight part by weight or more.

[0032]

As described above, according to the present invention, a butadiene polymer having a trans-1,4 bond content of 70 to 95% by weight and having an N-substituted amino ketone at the active terminal thereof, N-substituted thioaminoketone, N-substituted aminoaldehyde, N-substituted thioaminoaldehyde, or a compound represented by the general formula:

[0033]

(Wherein M represents an oxygen or sulfur atom)
At least 20 parts by weight of a terminal-modified butadiene polymer obtained by reacting at least one compound selected from compounds having an atomic group represented by the following, the tread portion was configured with a rubber composition comprising less than 70 parts by weight. In addition, heat resistance (durability), wear resistance, and fatigue resistance (crack resistance) can be compatible. Therefore, the pneumatic tire of the present invention,
When used for heavy loads with a deep tread groove, it has excellent wear resistance and can run for a long period of time. Also, since the heat generation is reduced, the influence of heat on the belt part is reduced, so that the durability is improved and the distortion at the groove bottom part is reduced,
Crack resistance is improved, thereby making it possible to suppress crack generation and improve rehabilitation.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Fumitoshi Suzuki 2-15-33 Isogo, Isogo-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Shuichi Akita 553-1 Park Hills N-204, Shinanomachi, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture ( 56) References JP-A-59-197442 (JP, A) JP-A-59-196338 (JP, A) JP-A-59-196337 (JP, A) JP-A-58-189203 (JP, A) Hei 3-190944 (JP, A) JP-A-62-96542 (JP, A) JP-A-62-27441 (JP, A) JP-A-61-42552 (JP, A) JP-A-63-218746 (JP, A) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 7/00-21/02 C08C 19/22

Claims (1)

(57) [Claims] 1. A butadiene polymer having a trans-1,4 bond content of 70 to 95% by weight and having an N-substituted aminoketone, N-substituted thioaminoketone, N-substituted amino An aldehyde, an N-substituted thioaminoaldehyde, or a compound of the general formula (Wherein M represents an oxygen or sulfur atom) A terminal-modified butadiene polymer (A) obtained by reacting at least one compound selected from compounds having an atomic group represented by the following formula:
20 to 69 parts by weight and other diene rubber (B) 80 to 31
A heavy-duty pneumatic tire having a tread portion formed of a rubber composition containing a rubber component by weight as a rubber component.