JPS6061310A - High speed large size pneumatic tire - Google Patents

Abstract

PURPOSE:To enhance the low rolling resistance and durability of a high speed large size tire for busses or the like, by specifying the structural compositions of polybutadiene rubber, the I2 absorption amount of carbon black, blending the post-vulcanization characteristics to form an outer surface rubber layer having a two layer structure. CONSTITUTION:An outer surface layer 1 having a loss tangent, after vulcanization, of less than 0.25-100 deg.C is formed for 0.6-0.9 of the entire tread section with the use of, for 100pts.wt. of rubber component, 80-90pts.wt. of natural rubber and/or synthetic polyisoprene rubber, 20-40pts.wt. of polybutadiene rubber in which more than 10pts.wt. of the polybutadiene rubber has more than one atomic groups having specific structure formulae and coupled to moelcular chains by carbon-carbon coupling, and also has 1, 2 vinyle coupling content of 5-50wt%, and 40-60pts.wt. of carbon black having I2 absorption amount of 50-128g/kg. Further an inner surface rubber layer 2 is formed such that it has a loss tangent of less than 0.15 at 100 deg.C after vulcanization. With this arrangement, the low rolling resistance and durability of the tire may be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a large pneumatic tire for high speed use that has low rolling resistance and improved durability.

In recent years, due to the expansion and development of automobile-only roads and the improvement in the paving rate of general roads, there has been an increasing demand for higher speeds for large tires, such as those for trucks and buses.

A problem with increasing tire speeds is heat generation due to deformation of the tire rubber during driving. As the running speed of the tire increases, the amount of heat generated by the deformation of the rubber also increases, and heat accumulates inside the tire. This increases the temperature inside the tire, and in severe cases, the rubber components decompose, weakening the tire and eventually causing it to burst.

Even before this happens, the breaking strength of the rubber decreases due to the rise in tire internal temperature, which shortens the lifespan of tires that are not prone to various failures (such as cracks at the bottom of the grooves, chipping, etc.).

Therefore, as a countermeasure against this problem, a so-called cap-under laminated structure has been proposed. In order to reduce heat generation inside the tire tread, the tire trend part has a two-layer structure: an outer rubber layer (cap layer) and an inner rubber layer (underlayer), and the underlayer generates more heat than the gear layer. This is a method of arranging rubber with even lower properties.

As a result, we were able to achieve some effects. However, the current performance requirements cannot be met simply by making the trend part a two-layer structure; it is necessary to further reduce heat generation and durability (resistance to groove cracking in the trend part, etc.) in the cap layer or under layer. It is. For this reason, attempts have been made to replace a portion of the natural comb (NR), which is said to have a low hysteresis loss and has been conventionally used in the cap layer, with polybutadiene (BR), which has an even lower hysteresis loss. Since BR has good crank resistance, it is also good for improving trend part groove crack resistance.

However, BR has a large amount of strain when subjected to stress,
Since the calorific value increases accordingly, the amount of compounding is limited, so that sufficient effects cannot be achieved.

Generally, one way to improve the durability of tires is to improve the durability of the cap layer rubber. To this end, it is necessary to make the cap layer comb of rubber with lower hysteresis loss. The method is as follows:
Examples include (1) using a polymer with low hysteresis loss as a rubber component, (2) using carbon black with low reinforcing properties as a reinforcing agent, and (3) lowering the blending amount of carbon black. . However, methods (2) and (3) are not preferred because the strength of the rubber is extremely reduced. Therefore, (1) remains, but as mentioned above, NR/BR systems have been used in this method, and since these IJ polymers are so-called low energy loss polymers, they are not sufficiently durable. It's not something that can be improved.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a large-sized pneumatic tire for high-speed use that maintains the crank resistance of the tread groove at the current level and has improved high-speed durability. purpose.

Therefore, the present invention provides a pneumatic tire in which the trend portion is composed of at least two layers, an outer surface rubber layer and an inner surface rubber layer, in which the outer surface rubber layer comprises (1) natural rubber and/or
or synthetic polyisoprene comb 80 to 60 parts] and 20 to 40 parts by weight of polybutadiene rubber, with a total rubber content of 100 parts by weight, and at least 10 parts by weight of the polybutadiene rubber. , the following formula (wherein R1 and R2 represent hydrogen or a substituent, m
and n represents an integer) is bonded to the molecular chain through a carbon-carbon bond, 1,2
- Polybutadiene rubber with a vinyl bond content of 5 to 50% by weight, and (2) an iodine adsorption amount of 50 to 50% as a reinforcing agent.
1.289/Kq carbon black to raw rubber 1.0
Contains 40 to 60 parts by weight relative to 0 parts by weight, (3
) The loss tangent (-δ) at 100°C of the rubber after vulcanization of the outer surface side rubber layer is less than 0.25, and (4) the ratio of the outer surface side rubber layer is 0.6 to 0.9 of the entire trend part. and
Furthermore, the object of the present invention is to provide a large, high-speed pneumatic tire in which the loss tangent (taIIδ) at 100° C. after vulcanization of the inner side rubber layer is less than 0.15.

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

FIG. 1 is an explanatory diagram of a meridional half cross section of an example of the tire of the present invention. In FIG. 1, T is a tolerado portion, which is composed of a cap layer (rubber layer on the outer surface side) 1 and an under layer (rubber layer on the inner surface side) 2. 6 is a pair of left and right bead portions 4
This is a carcass mounted between . Moreover, 5 is a side wall part.

In the present invention, an ER with a 1,2-vinyl bonded gold content of 5 to 50% by weight, 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, is used in the camp layer 1. (hereinafter referred to as modified BR) and
Iodine adsorption amount is 50 to 128 as a reinforcing agent? 9 carbon blanks are contained in /. This is for the following reasons.

That is, originally, the performances required of the tread camp layer of a durable tire are (1) small energy loss, (2) small reversion during overvulcanization,
(3) It has high strength, etc. Taking these into consideration, mixed rubbers such as NR/BR are currently used for the cap layer.

However, it still does not fully satisfy this required performance. Therefore, it is possible to consider (a) using a polymer with lower energy loss, and (b) using carbon black with lower reinforcing properties and keeping the blending amount low. However, in method (b), the strength of the rubber decreases, and in method (b), for example, simply increasing the blending ratio of BR, which has low energy loss, reduces the strength, especially the strength at high temperatures. This is not desirable as it will be extremely low. From this point of view, as a result of intensive studies, we arrived at the use of carbon black in the above-mentioned modified BR with an iodine absorption amount of ~128 r/9. In other words, by using modified BR, which has lower energy loss than conventional polymers, and carbon blanks, which have greater reinforcing properties, we aim to improve the tire's low rolling resistance and durability.

In the atomic group represented by formula (1) above, R+, R
2 is hydrogen or a substituent, respectively. This substituent is not specified, but includes, for example, an amino group, an alkylamino group, and a dialkylamino group. Also, rl
l and n are integers.

At least one of these atomic groups is bonded to the molecular chain through a carbon-carbon bond, and the 1,2-vinyl bond gold content is 5 to 5.
50% by weight BR, that is, modified BR, is produced, for example, by polymerizing butadiene using an alkali metal catalyst and adding benzophenones to the butadiene rubber solution obtained after the polymerization reaction is completed. In this case, the alkali metal based catalyst used is lithium.

The base material is each metal element of sodium, rubidium, and cesium. Furthermore, the number of benzophenones introduced into the polybutane compound is on average 1 or more per rubber molecular chain (that is, 0 per 100 parts by weight of rubber).
．． 05-10 parts by weight). As the benzophenones, benzophenones having at least one amide group, alkylamino group, or dialkylamino group in one or both benzene rings in the formula (1) are particularly preferred. 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 4'-diaminobenzophenone and 4-dimethylaminobenzophenone.

The microstructure of the modified BR obtained as described above is 1
, 2-vinyl bound gold content is 5 to 50% by weight, preferably 5 to 35%. When the 1,2-vinyl bond content exceeds 50% by weight, the energy loss of the rubber is extremely reduced. This modified BR has greater interaction with the carbon blank than normal rubber that is not treated with benzophenone.

This is because, when the amount of bound rubber is measured in an unvulcanized product of rubber blended with this modified BR, it is approximately twice as much as that of normal rubber. This is because the amount of bound rubber increases due to the benzophenone treatment, and therefore, the modified BR has a higher
It is thought that it is strongly connected to the carbon blank.

Furthermore, the vulcanized rubber containing modified BR has a lower −δ and a lower calorific value than a vulcanized rubber containing ordinary rubber.

In the present invention, the cap layer 1 is made of natural rubber (NR).
and/or synthetic polyisoprene rubber (IR) 80~
60 parts by weight of polybutadiene rubber, 20 to 40 parts by weight of polybutadiene rubber, the total rubber content is 100 parts by weight, and at least 10 parts by weight of the polybutadiene rubber is modified BR.
Replace it with . (NR and/or IR) /
If the BR ratio exceeds 80/20, the BR will decrease and the improvement in heat generation will not be sufficient, while if it is less than 40/60, the (NR and/or IR) will decrease and the strength (crank resistance) will decrease. will decrease.

In addition, in the present invention, iodine e is used as a reinforcing agent.
Is it 50-128? /Ky carbon blank is contained in the cap layer 1 at a ratio of 40 to 60 parts by weight based on 100 parts by weight of the raw rubber.

This carbon blank ranges from so-called HAF to 15AF.
It is essential to meet the requirements for reinforcing properties. Carbon black has an iodine adsorption amount of 50 P/9.
If it is less than 128f/9, the reinforcing property will be significantly reduced, and if it exceeds 128f/9, it will become SAF class, and the mixing processability will be difficult. Moreover, if the blending amount exceeds 60 parts by weight, it is unfavorable from the viewpoint of exothermic properties, and if the blending amount is less than 40 parts by weight, the strength will drop significantly.

10 of the rubber after vulcanization of the cap layer 1 formed in this way.
The loss tangent (tan δ) at 0° C. is less than 0.25. This is because when the temperature exceeds 025, the amount of heat generated increases.

In addition, the ratio of camp layer 1 to the entire tread portion is 0.6
~0.9. That is, the ratio of the cap layer (N) to the under layer (B) is 0.6 < A/(A + B) <
It is 0.9. This is because if the ratio of the cap layer 1 is less than 0.6, the ratio of the underlayer increases, the rigidity of the trend portion decreases, and the steering stability at high speeds becomes insufficient.

Furthermore, in the present invention, 1 after applying a of the underlayer 2.
The loss tangent (t8Ilδ) at 00°C is less than 0.15. The underlayer is inside the tire tread and is tangential to the carcass or bell). Therefore, in order to minimize the heat generation due to transfer under load as part of the casing, it is necessary that -δ be less than 015.

In the large high-speed pneumatic tire of the present invention, a vulcanized rubber having suitable physical properties depending on the purpose can be used except for the lug portion. In addition, various compounding agents commonly used in the rubber industry can be appropriately selected and used in all parts including the tread part.

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

As shown in Example Table 1, in the blend system of NR and BH,
55 parts by weight of carbon black, 10 parts by weight of aroma oil, 3 parts by weight of anti-aging agent (N-phenyl-1,3-dimethylbutyl-p-7 enylene diamine), 2.
0 parts by weight, N-oxydiethylene-2 as a vulcanization accelerator
-Benzothiazolylsulfenamide (NOBS)
1.0 part by weight was blended to form cap layers 1, 2, and 3.4. Here, BR-2 and -3 are modified BRs treated with 4,4'-bis(dimethylamine)benzophenone. BR-1 is a normal rubber (without benzophenones added).

Here, (1) tensile strength, elongation, and tensile stress are determined by J
According to Engineering 5K6301. (2) Heat resistance and fatigue resistance are measured by Gutdrich and Flexmeter.
A cylindrical test piece measuring 2 inches and 1 inch in height was subjected to a load of 50 bonds, a dynamic strain of 225%, and a vibration frequency of 180 rpm, and the amount of heat generated was measured using a thermocouple inserted at the bottom of the test piece. The fatigue life was determined by measuring the number of repetitions until . (3) To evaluate the energy loss of the rubber, the loss tangent (-δ) determined by a known method using a viscoelastic spectrometer (manufactured by Wakagi Seisakusho) was used. That is, the test rubber was attached to the apparatus as a strip-shaped sample with a length of 10 mm, a width of 9 mm, and a thickness of 20 mm, and the temperature was 100 mm.
℃, frequency of 20 Hz, and dynamic strain of 5%, shear vibration is performed, and -δ is measured. Furthermore, the dynamic elastic modulus (E') is also measured at the same time.

Note that Table 2 shows the microstructures of BR-1, -2, and -3.

(Margins below this page) Table 2 Note) (2) 2-vinyl amount Measured by IH-NMR method.

The benzophenones introduced here will eventually become mo4, 4
'-bis(dimethylamino)benzophenone.

Next, camp layers 1 and 2 were selected in Table 1, and a truck bus bias tire 1000-20.14 PH was selected.
The tire was placed as a trend part cap layer rubber, and its heat resistance and fatigue resistance as a tire were evaluated and confirmed by an indoor drum durability test.

The thickness of the base rubber of the tire used in this test (a) in Figure 2 has a profile of a:b=1:1, which is considered typical for bias tire traps for truck buses. (See Figure 2). Also, the volume ratio of the cap layer (4) and the under layer (B) is A/(A + B) =
It is 0.70.

This indoor drum durability test was conducted under the so-called FMV-3SA119 conditions, in which the drum was run at a constant speed of 57 min/hr and the load was increased in time steps shown in Table 3 below. evaluated. The results are shown in Table 4 below. Regarding the heat generation property, before driving, we tested the area m (the part where the heat generation level is the highest when the tire is running) in Figure 2 with a diameter of 4mm. A drill hole was pre-drilled, and the temperature was measured with a thermocouple at each step, and the heat resistance was evaluated based on the temperature level.

Table 3 FMV-8S (A119 conditions) Furthermore, four tires were installed on each rear wheel of the truck, and the paving ratio ioo
An actual vehicle durability test was conducted with four vehicles each driven by high-speed users who drive at least 80% of the time on highways. The running period is 3 months. After running, the rubber of the cap layer was cut out from the tire and its physical properties were measured. This was compared with the rubber physical properties of a new tire, and durability was evaluated based on the rate of change. The results are shown in Table 4.

Although a bias structure tire was used in this embodiment, a radial structure tire may also be used.

Table 4 From Table 1, rubber containing modified BR (BR-2, -3) is B
It can be seen that compared to the rubber containing R-1, although the tensile properties are the same, the heat generation property is improved.

Table 4 shows that tires in which rubber containing modified BR is placed in the camp layer of the tread have improved durability in indoor durability tests, as well as improved rubber deformation in actual vehicle durability tests. It is clear that this is an improvement.

That is, in the indoor durability test, the amount of heat generated was low, and the running distance was improved by about 10 to 14%.

In addition, generally, the elastic properties of rubber deteriorate due to running fatigue. It is judged that the larger the rate of change in physical properties, the poorer the fatigue resistance. In this sense, the improved durability of camp layer 2 is proven.

From the above results, it is clear that a large tire in which a specific amount of modified BR is blended and a rubber having rubber physical properties within a limited range is arranged in the tire trend portion cap layer has significantly improved durability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a meridian half cross section of an example of the tire of the present invention, and FIG. 2 is an explanatory view of a partially enlarged cross section of the shoulder thereof. T... Trend part, 1... Camp layer, 2... Under layer, 6... Carcass, 4... Bead part, 5...
・Side wall section. Agent: Patent Attorney Shin Ogawa − Patent Attorney Ken Noguchi Patent Attorney Kazuhiko Saishita Figure 1 Figure 2

Claims (1)

[Scope of Claims] A pneumatic tire in which the tread portion is composed of at least two layers, an outer surface rubber layer and an inner surface rubber layer, wherein the outer surface rubber layer is made of (1) natural rubber and/or synthetic polyisoprene rubber. 80~60 parts by weight, polybutadiene rubber 20~
40 parts by weight, the total rubber content is 100 parts by weight, and at least 10 parts by weight of the polybutadiene rubber has the following formula ( (wherein R1 and R2 represent hydrogen or a substituent, m
and n represents an integer) is bonded to the molecular chain through a carbon-carbon bond, ■, 2
- Polybutadiene rubber with a vinyl alloy alloy content of ~50% by weight, and (2) an iodine adsorption amount of ~50% as a reinforcing agent.
1.28 f/9 carbon blank to raw rubber 10
Contains 40 to 60 parts by weight relative to 0 parts by weight, (3
) The loss tangent (-δ) at 100° C. of the rubber after vulcanization of the outer surface rubber layer is less than 0.25, and (4) the ratio of the outer surface rubber layer to the entire tread portion is 0.6 to 0.9 and
Furthermore, a large-sized pneumatic tire for high speeds in which the loss tangent (-δ) at 100° C. after vulcanization of the inner side rubber layer is less than 015.