JPS6061311A - Pneumatic tire for heavy duty vehicle - Google Patents

Abstract

PURPOSE:To enhance the durability of a penumatic tire for working vehicles without injuring the cut-resistivity and wear-resistivity of the tire, by specifying the structural compositions of styrene butadiene coplymer rubber and the I2 absorption amount of carbon black to form a cap tread for the tire. CONSTITUTION:A cap tread a constituting a tread section 1 is formed with the use of more than 70pts.wt. of styrene butadiene copolymer rubber in which more tha 20pts.wt. thereof has more than one atomic groupes having chemical structures and coupled to molecular chains, to which copolymer rubber 45-70pts.wt., for 100pts.wt. of raw rubber, of carbon black as a reinforcing agent, having an I2 absorption of 70-130mg/g is added. With this arrangement, the high speed duability may be enhanced without injuring the cut-resistivity and ware-resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire for heavy-duty vehicles that has improved high-speed durability without impairing cut resistance and wear resistance.

In general, off-the-road tires that are used for applications where the road surface includes rocky areas or crushed stone sites, industrial vehicle tires, and large tires that run on unpaved roads with a lot of crushed stones are susceptible to cuts on the tire tread while driving. Sometimes. The reality is that these tires are being used at higher speeds than would normally be expected. Cut wounds, which are external injuries to tires, sometimes penetrate through the thick tread and reach the carcass. Additionally, even if the cut is not a large cut like this, the scratch may grow during subsequent driving, or some of the rubber from the tread may be removed and the tire may become unraveled, reducing the lifespan of the tire. .

Conventionally, in order to prevent such cut scratches, a rubber composition mainly composed of styrene-butadiene copolymer rubber (hereinafter abbreviated as SBR) has been used in the trend portion of tires for heavy vehicles. The reason for this is that SBR has a glass transition temperature of natural rubber (hereinafter abbreviated as NR) and cis-1,
Since it is higher than that of 4-polybutadiene rubber, the molecular motion of SBR cannot follow phenomena that suddenly occur in a short period of time, such as trauma, and therefore exhibits excellent cuttability. That is,
In order to maintain a high level of cut resistance and extend the lifespan against external damage, it is desirable to use rubber mainly made of SBR for the tread portion.

Incidentally, tires for heavy vehicles (radial structure, bias structure) have a high load applied to a unit area of the tread surface, that is, a high surface pressure, and therefore wear out at a high rate, so that they are also required to have wear resistance. To improve wear resistance, carbon black, which has strong reinforcing properties, must be used. However, when a rubber mainly composed of SBR is used in combination with carbon black, which has strong reinforcing properties, hysteresis loss increases due to repeated deformation during running, and heat generation increases. In tires with high surface pressure and large tread volume, such as tires for heavy vehicles, the heat generated is not released to the outside of the tire and is stored, causing the temperature of the tread to rise and the carcass to reach the highest temperature. Separation occurs in the vicinity where the belt or tread portion is adhered, leading to tire damage. The heat generated by repeated deformation of a tire of a certain shape while running, and the resulting temperature rise, are determined by the load applied to the tire and the running speed. There is no other option than to lower the vehicle speed or reduce the travel speed. Since the load applied to the tire is determined by the strength of the tire's reinforcing material, the running speed must eventually be reduced.

Therefore, the running speed performance of heavy vehicles is limited by the tires used therein, and it is therefore strongly necessary to improve this limit running speed performance without impairing cut resistance due to external injuries. This is what is currently being requested.

The present invention has been made in view of the above-mentioned circumstances, and the present invention has been made in view of the above-mentioned circumstances, and is aimed at the limit running speed at which the temperature rise during running of the tire causes damage such as separation, without impairing the cut resistance and wear resistance of the tread portion. The purpose of the present invention is to provide a pneumatic tire for heavy-duty vehicles with improved performance.

Therefore, the present invention uses styrene in the camping tread.
The butadiene copolymer rubber should not contain 70 parts by weight or more and a reinforcing agent, and 20 parts by weight or more of the styrene-butadiene copolymer rubber should contain the following formula (where R1 and R2 are hydrogen or substituted). at least one of the atomic groups represented by (m and n represent integers)
This is a styrene-furidiene copolymer rubber in which carbon atoms are bonded to the molecular chain through carbon-carbon bonds. The gist of this invention is a pneumatic tire for heavy-duty vehicles, characterized in that it contains 45 to 70 parts by weight.

Hereinafter, the configuration of the present invention will be explained in detail.

The figure is an explanatory diagram of a meridional cross section of an example of the tire of the present invention.

In the figure, 1 is a trend, 2 is a pair of left and right bead portions 4
, 4, and in the tread 1, a belt reinforcing layer 3 is arranged so as to surround the outer periphery of the carcass 2. 5, 5 are a pair of left and right bead portions 4
These are a pair of left and right sidewall portions that connect to the left and right side walls. Tread 1 has a two-layer structure: Camp Trend A on the outside and Base Tread B on the inside.

In the present invention, Camp Trend A is combined with a styrene-butadiene copolymer rubber (hereinafter referred to as modified SBR) in which at least one of the atomic groups represented by the following formula is bonded to the molecular chain through a carbon-carbon bond. 12 adsorption amount 70-130m9/? as a reinforcing agent Use carbon blank. This is for the following reasons. In other words, in order to improve the critical running speed that can cause separation tire damage during running of large tires for heavy vehicles, it is important to reduce hysteresis loss caused by repeated deformation of the vulcanized rubber used in the tread. As a means (+)S
Either use a raw material rubber with a glass transition temperature lower than that of BR, or (11) From the viewpoint of use of carbon black, use a small amount of (a+ carbon black with low reinforcing properties) or (bl carbon black with strong reinforcing properties). One possible method is to uniformly disperse carbon black in rubber to reduce energy loss due to friction between carbon black particles.However, method m reduces the cuttability, and the Therefore, we considered the idea of < rr ) - (b+) and decided to consider the idea of Even if a carbon blank with high reinforcement properties is used due to this functional group, contact friction between carbon black microparticles will not occur, reducing hysteresis loss, which can occur suddenly and in a short period of time due to external injuries, etc. resists damage phenomena,
This is to maintain cut resistance at a high level.

In the atomic group represented by formula (1) above, R, and R2 are each hydrogen or a substituent. This substituent is not specified, but includes, for example, an amine group, an alkylamino group, and a dialkylamino group. Moreover, m and n are integers.

A styrene-butadiene copolymer rubber in which at least one of such atomic groups is bonded to the molecular chain through a carbon-carbon bond, that is, a modified SBR, is produced by combining styrene and butadiene using an alkali metal-based catalyst. It is produced by reacting and adding benzophenones to the styrene-butadiene copolymer rubber solution obtained after the polymerization reaction is completed. In this case, the alkali metal-based catalyst used is one containing each of the metal elements lithium, sodium, rubidium, and cesium. However, the amount of benzophenones introduced into the styrene-butadiene copolymer rubber is on average 1 or more per rubber molecular chain (i.e., 90.05 to 1.0 parts by weight per 100 parts by weight of rubber). ). As this benzophenone, the above formula (1)
at least one on one or both benzene rings in
Particularly preferred are benzophenones having two amino, alkylamino or dialkylamino groups. Examples of the benzophenone include 4.4'-bis(dimethylamino)-benzophenone, 4.4'-bis(diethylamino)-benzophenone, 4.4'-bis(dibutylamino)-benzophenone, and 4.4'-bis(dibutylamino)-benzophenone. Examples include diaminobenzophenone and 4-dimethylaminobenzophenone.

The modified SBR thus obtained preferably has a styrene content of 10 to 30% by weight and a butadiene moiety having 5 to 40 1,2 vinyl bonds. The styrene content is 30% by weight or more and/or the butadiene moiety is 1
, 2 vinyl bonds above 400 parts by weight are unsuitable because the mobility of the polymer molecules decreases and the hysteresis loss increases; This is because if the weight ratio of 2-vinyl bonds is less than 5, sufficient cut resistance cannot be obtained.

In the present invention, SBR is applied to the cap and tread A at 7
It contains 0 parts by weight or more, and 20 parts by weight or more of the 70 parts by weight or more is replaced with the above-mentioned modified SBR. This is because if the SBR is less than 70 parts by weight, the cut resistance due to external damage is insufficient, and if the modified SBR is less than 20 parts by weight, hysteresis loss cannot be effectively reduced.

In addition, in the present invention, as a reinforcing agent, ■2 adsorption amount 70
~130"9/y of carbon black is contained in the cap/tread A. In this case, ■2 If the adsorption amount is less than 70~1, the wear distribution will be insufficient, and if it exceeds 130, carbon black should be mixed. This is because a sufficient particle dispersion state cannot be obtained when the carbon black is added.The content of carbon black is 45 to 70 parts by weight per 100 parts by weight of the raw rubber.If it is less than 45 parts by weight, the abrasion resistance is insufficient. ,7
This is because if it exceeds 0 parts by weight, hysteresis loss increases and sufficient high-speed durability cannot be obtained.

The dynamic storage modulus (E') of the vulcanized rubber of the cap/tread A made in this way is 3 M at 100°C.
Pa (E'< 7 MPa. E' is 7 MPa
If it is stiffer than a, it will be too hard and crack growth and chipping will occur easily, and if it is less than 3 MPa, the deformation will increase and the movement with the road surface will increase, reducing the wear resistance. In addition, the dynamic loss rate (tan δ) is −δ(0, 20. ta
When nδ exceeds 0.20, hysteresis loss is too large and high-speed durability cannot be improved.

The dynamic storage modulus (E') of the vulcanized rubber of base tread B is 2.5 MPa <E' at 100°C.
< 5.5 MPa, which is in the range of 15-20% lower than Cap Tread A. If it is lower than 2.5 MPa, the deformation of the entire tread portion will be shared by the base tread B, and the heat generated from this portion will increase in the opposite direction to the expected direction. On the other hand, if the pressure is higher than 5.5 MPa, it becomes too hard and difficult to deform. The dynamic loss rate (Ian δ) is 3 δ (0.15). Since wear resistance is not required at the base and tread B, tan δ is lowered to 0.15 or less to reduce internal heat generation. By doing so, durability during high-speed running can be improved.

In the pneumatic tire for heavy-duty vehicles of the present invention, other than the tread portion, vulcanized rubber having physical properties suitable for the purpose can be used. Various compounding agents commonly used in the rubber industry can be appropriately selected and used for all parts including the tread and the tread.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

Example After replacing the stainless steel polymerization reactor with dry nitrogen, 1.3
- 11.6% by weight of butadiene, 39% by weight of styrene, 844% by weight of Hensefu, and 0% by weight of te]rahydrofuran.
n- which became an n-hexane solution in a mixed solution of 08 weight
Butyl lithium 0.21 mmol/total polymerization solution 100f
was added and polymerization was carried out at 45°C for 2 hours without stirring. After the polymerization reaction, 4,4'-bis(dimethylamino)benzophenone (hereinafter referred to as MAR) was added in an amount of 0.31 mmol/total polymerization solution 1002, and stirred for 5 minutes to give a concentration of 1 part by weight per 100 parts by weight of the polymer. The contents of the reactor were taken out into a methanol solution to which 2゜6-di-t-butyl-p-cresol (hereinafter referred to as BHT) had been added, and the resulting polymer was solidified and dried under reduced pressure for 2 days. A modified SBR was prepared by doing the following.

In addition, polymerization was carried out in the same manner as above, and B was added without adding MAB.
SBR was prepared by coagulating with a solution containing H'T.

The composition, microstructure, and Mooney viscosity of the polymer thus obtained are shown in Table 1 below.

Table-1 Using the 5BR1 modified SBR shown in Table-1,
Tread A was added. The contents of this formulation are shown in Table 2 below. The sample tire size is 1000 R201
4PR lug pattern, with 3 + 9 + 15 (0,175) in the carcass and belt parts respectively.
W, 3 (0,20)+6. A steel cord with a (0,35) structure is used. This test tire had a two-layer tread structure, and the cross-sectional area of the base tread B was 20% of the cap tread A. base·
The rubber composition of Tread B is shown in Table 3 below.

(Margin below this page) Table 2 (Note t) I2 adsorption amount 121 m9/y Rice 1,3-dimethylbutyl-p-phenylenediamine Korai N0BS: N-oxodimethyle/-2-be/nothiazolyl Phenamide Table 3 (Note 2) ■2 Adsorption amount 70 m9/g E' and δ were measured using a viscoelastic spectrometer manufactured by Makimoto Seisakusho, frequency 20H2, dynamic strain 10±2%,
Measurements were performed under tensile elongation conditions.

Table 4 shows the measured dynamic viscoelasticity, high-speed durability, abrasion resistance, and cut resistance of the vulcanized rubber used in the tire cap Trueno I-A in an indoor drum test. Wear resistance and cut resistance were measured by driving on unpaved roads at an average running speed of 40 km/h for two months, and displaying the wear conditions at that time as an index with SBR tires set as 100 (the higher the index, the higher the index). The cut resistance was expressed as an index based on the number of cuts that occurred on the surface, with SBR tires set as 100 (the larger the index, the better).

Table-4 I counted the distance traveled.

As is clear from the results shown in Table 4, the gap/l/red part has the specific dynamic performance of the present invention and the base/red part has the specific dynamic performance, which is blended with the SBR containing benzophenones of the present invention. A large tire for heavy vehicles in which the tread portion is combined has significantly improved high-speed durability without sacrificing cut resistance and wear resistance.

[Brief explanation of drawings]

The figure is an explanatory diagram of a meridional cross section of an example of the tire of the present invention. 1...Tread, 2...Carcass, 3...Belt reinforcement layer. Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Noguchi Patent Attorney: Kazuhiko Saishita

Claims (1)

[Claims] The cap/tread contains 70 parts by weight or more of styrene/butadiene copolymer rubber and a reinforcing agent, and 20 parts by weight or more of the styrene/butadiene copolymer rubber is R1 in the following formula C. and R2 represents hydrogen or a substituent, and m and n represent integers) is a styrene/butadiene copolymer rubber in which at least one of the atomic groups represented by the following is bonded to the molecular chain with a carbon-carbon bond, A pneumatic tire for a heavy-duty vehicle, characterized in that (1) 45 to 70 parts by weight of carbon blank with a 2 adsorption amount of 70 to 130 m&/7 is contained based on 100 parts by weight of raw rubber as the reinforcing agent.