JPH0643517B2 - Rubber composition for large pneumatic tires for high speed - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention uses an improved polybutanediene rubber to provide rolling resistance and high-speed durability without impairing wear resistance and cut resistance. The present invention relates to an improved rubber composition for large pneumatic tires for high speed.

[Prior art]

Conventionally, tires for heavy-duty trucks and buses are required to have very high wear resistance and cut chipping resistance, and unlike the tires for passenger cars, fuel economy has not been a very important tire characteristic. That is, rolling resistance and skid characteristics were not very important characteristics.

However, the recent improvement of road pavement ratio, spread of highways,
Furthermore, due to the soaring gasoline prices and the tendency toward social energy saving, even in the case of large tires, in addition to the wear resistance and cut chipping resistance, it is also economical Therefore, rolling resistance has become a very important tire characteristic from the viewpoint of safety, skid resistance and high-speed durability.

In other words, as a social demand, even for large tires, there has been a demand for tires that have a low level of rolling resistance while maintaining the wear resistance of skid characteristics at a conventional level. In general,
Tires with reduced rolling resistance have been required. Generally, when the rolling resistance is lowered, the wet skid resistance is also lowered, and these two characteristics are contradictory characteristics and there is a trade-off relationship. By the way, a high vinyl type solution-polymerized styrene-butadiene copolymer rubber (hereinafter referred to as solution-polymerized SB
It has been found that the use of R for short) breaks this tradeoff (US Pat. No. 4,334,567), and the use of this high vinyl solution polymerized SBR for fuel efficient tires for passenger cars is becoming common.

However, in the case of tires for heavy-duty trucks and buses, the severity of the tires is extremely high. Therefore, when the above-mentioned high vinyl solution-polymerized SBR is used, the wear resistance is significantly deteriorated and it cannot be put to practical use. .

Therefore, the rubber composition for a fuel-efficient tire tread of a large tire is mainly composed of natural rubber, and in order to further improve rolling resistance, it is common to blend a polybutadiene rubber. However, when this polybutadiene rubber is blended, the cut resistance and the chipping resistance are significantly deteriorated, so that its use is limited. Therefore, a method of improving the tire structure has been generalized. That is, the tread has a two-layer structure of a cap tread and a base tread, the cap tread rubber is provided with rubber having excellent wear resistance, cut resistance, wet skid resistance, etc., and the base tread rubber is exothermic. There is also a technique for improving rolling resistance of the entire tread portion by arranging a rubber having a low hyphteresis, which does not significantly deteriorate other characteristics. However, this two-layer tread structure also has major drawbacks. That is, in order to reduce the hysteresis loss of the entire tread portion, it is necessary to take a large volume of the base tread portion, and then the base tread portion is exposed at the end of wear, so the wear resistance and cut resistance at the end of wear are significantly reduced. Resulting in. At times, the belt portion is damaged, so that rehabilitation property is deteriorated. On the contrary, if the volume of the base tread portion is reduced in consideration of the wear resistance at the end of wear, the rolling resistance improving effect is reduced. Further, at the current technical level, it is impossible to improve natural rubber, and JP-A-59-117548 discloses that use of synthetic polyisoprene rubber improves heat generation. , This is not very satisfying. Therefore, even now, the rolling resistance is small and the wet skid resistance is large, in addition, there is no rubber composition for a cap tread having good wear resistance, and such a rubber composition for a cap tread is used. The provision was strongly desired.

[Object of the Invention]

The present invention has been made in view of the above-mentioned circumstances, and it is preferable to use a modified (modified) polybutadiene rubber having a significantly improved heat generation property to prevent rolling resistance without impairing wear resistance and cut resistance. An object of the present invention is to provide a rubber composition for a large-sized pneumatic tire for high speed, which has improved properties and high-speed durability.

[Structure of Invention]

Therefore, the present invention has the following formula in the polymer molecular chain. Blending polybutadiene rubber having an atomic group represented by 20 to 40 parts by weight of polyisoprene rubber 60 to 80 parts by weight,
With respect to 100 parts by weight of blended rubber, which is 100 parts by weight in total,
Iodine adsorption amount is 40-150mg / g, nitrogen specific surface area is 40-150
m ² / g, DBP oil absorption 60 ~ 140ml / 100g, specific coloring power 80
A rubber composition for a large-sized pneumatic tire for high speed, which comprises 30 to 90 parts by weight of carbon black of 130 to 90 parts by weight.

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

(1) The polybutadiene rubber used in the present invention has an atomic group represented by the following formula (I) in the polymer molecular chain (hereinafter referred to as modified polybutadiene rubber).

Introduction of the atomic group represented by the above formula (I) is a bond of the following formula. It is carried out by reacting a compound having M (wherein M represents an O atom or an S atom) (hereinafter referred to as compound A) with a polybutadiene rubber.

As the compound A, N, N-dimerformamide,
N, N-diethylformamide; N, N-diethylacetamide; aminoacetamide, N, N-dimethyl-
N ', N'-dimethylaminoacetamide, N-phenyldiacetamide; N, N-dimethylacrylamide,
N, N-dimethylmethacrylamide; propionamide; N, N-dimethylpropionamide; 4-pyridylamide, N, N-dimethyl-4-pyridylamide; N,
N-dimethylbenzamide, p-aminobenzamide,
N ', N'-(p-dimethylamino) benzamide,
N, N-dimethyl-N '-(p-ethylamino) benzamide, N-acetyl-N-2-naphthylbenzamide; nicotinamide, N, N-diethylnicotinamide; succinamide, maleic amide, N, N ，
N ', N'-tetramethylmaleic acid amide; succinimide, maleimide, N-methylmaleimide, N-methylphthalimide, 1,2-cyclohexanedicarboximide, N-methyl-1,2-cyclohexanedicarboximide; oxamide, 2-flamid, N, N, N ', N'
-Tetramethyloxamide, N, N-dimethyl-2-furamide; N, N-dimethyl-8-quinolinecarboxamide; N, N-dimethyl-p-amino-benzalacetamide, N, N-dimethyl-N '. , N '-(p'-dimethylamino) cinnamylidene acetamide; N, N-dimethyl-N', N '-(2-dimethylamino) vinylamide, N'-(2-methylamino) vinylamide; urea, N , N′-dimethylurea, N, N, N ′, N′-tetramethylurea; methyl carbamate, methyl N, N-diethylcarbamate; ε-caprolactam, N-methyl-ε-caprolactam, N-acetyl- ε-caprolactam, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, 2-piperidone,
N-methyl-2-piperidone, 2-quinolone, N-methyl-2-quinolone, 2-indolinone, N-methyl-2
-Indolinones; isocyanuric acid, N, N ', N "-trimethylisocyanuric acid and the like and their corresponding sulfur-containing compounds.

As a method for producing a polybutadiene rubber introduced with the atomic group represented by the formula (I), that is, a modified polybutadiene rubber, for example, (a) an alkali metal-based catalyst and / or an alkaline earth metal-based catalyst is used. Te by polymerizing 1,3-butadiene, a method of adding a compound a in the living diene polymer of the polymerization reaction is _{complete, (b) (C 2 H} 5) 2 AlCl-Co
_{Compound, (C 2 H 5) 3} Al-BF 3 (OC 2 H 5) 2 -Ni high cis-1,4 was polymerized in compounds, - in the case of polybutadiene rubber,
It can be obtained by adding an alkali metal and / or an alkaline earth metal to the rubber in a solution in which the polybutadiene rubber is dissolved in an appropriate solvent, and subsequently adding the compound A and reacting. In the case of a living polymer, the amount of the compound A used is 0.05 per mol of the catalyst used in the polymerization.
It is -10 mol, preferably 0.2-2 mol. Further, in order to introduce the compound A into the high cis 1,4-polybutadiene, the alkali metal and / or alkaline earth metal catalyst is 0.1 to 20 mmol per 100 g of the polymer. The amount of compound A used per 1 mol of the catalyst is 0.05 to 10 mol, preferably 0.2 to 2 mol, which is the same as above.

The alkali metal-based catalyst used in the polymerization reaction and the addition reaction in this case is a metal itself such as lithium, rubidium, or cesium, or a complex with a hydrocarbon compound or a polar compound thereof (for example, n-butyl lithium). , 2-naphthyllithium, potassium-tetrahydrofuran complex, potassium-diethoxyethane complex, etc.). Further, an alkaline earth metal-based catalyst is disclosed in JP-A-51-11.
Examples thereof include catalyst systems containing a compound such as barium, strontium, calcium, etc. as a main component described in JP-A No. 5590, JP-A No. 52-9090 and JP-A No. 57-100146. Any metal-based catalyst may be used as a catalyst for ordinary solution polymerization and is not particularly limited.

Among the above-mentioned modified polybutadiene rubbers, those modified with high cis 1,4-polybutadiene rubber are most preferable in terms of rolling resistance and body abrasion resistance, and then the proportion of 1,2-vinyl bonds is 15%. The following living-polymerized low-cis polybutadiene rubbers are preferred. This modified polybutadiene rubber is used by being blended with a polyisoprene rubber. The polyisoprene rubber here is a natural rubber or a synthetic polyisoprene rubber. 20 to 40 parts by weight with respect to 60 to 80 parts by weight of rubber, and the total amount of modified polybutadiene rubber and polyisoprene rubber is 100 parts by weight.
If the amount of the modified polybutadiene rubber is less than 20 parts by weight, there is no effect of improving the rolling resistance, and if it exceeds 40 parts by weight, the rolling resistance is lowered, but the breaking strength is deteriorated, and particularly when the cut resistance is deteriorated. At the same time, the mixing workability is significantly deteriorated.

(2) The carbon black used in the present invention has an iodine adsorption amount of 40 to 150 mg / g and a nitrogen specific surface area of 40.
It must be in the range of ~ 150 m ² / g. If the iodine adsorption amount and nitrogen specific surface area are less than 40, sufficient abrasion resistance cannot be obtained. The DBP oil absorption must be in the range of 60 to 140 ml / 100 g, and if it is lower than 60 ml / 100 g, the abrasion resistance will be poor. Further, when it exceeds 140 ml / 100 g, not only the workability is deteriorated but also the rolling resistance is increased, which is not practical.
The tinting strength must be 80-130. When it is lower than 80, abrasion resistance and cut resistance are inferior, and when it exceeds 130, carbon dispersion is remarkably deteriorated.

This carbon black is a known product that is generally commercially available, and examples thereof include ISAF carbon black and N399 carbon black.

The blending amount of this carbon black is 30 to 90 parts by weight with respect to 100 parts by weight of the blend rubber. If it is less than 30 parts by weight, abrasion resistance is poor and fracture strength is low. If it exceeds 90 parts by weight, the heat generation becomes too high and the rolling resistance deteriorates even if a large particle size carbon black having low heat generation is used.

The rubber composition thus obtained may be blended with a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, an antioxidant, a filler, a softening agent and the like which are commonly used in the rubber industry. .

In terms of the structure of the tire, either a cap / base two-layer tread structure or a single-layer tread structure without a base tread may be used. Further, the type of tire is not limited to either a radial tire or a bias tire.

Examples and comparative examples are shown below.

Examples and Comparative Examples Five kinds of 1000R20 14PR in which the rubber composition for the tread was mixed and only the tread rubber was changed in accordance with the compounding formulations (parts by weight) of the compounding numbers 1 to 5 shown in Table 1 below.
A prototype all-steel radial tire was manufactured and its rolling resistance and high-speed durability were measured in an indoor test. Also, in the outdoor test,
Wet skid resistance and abrasion resistance were measured. further,
The rubber composition used for tire trial production was press-vulcanized at 150 ° C. for 30 minutes, and the physical properties of the vulcanized product were measured. The results are shown in Tables 1 and 2.

The evaluation methods are as follows.

Tensile properties: Compliant with JIS K6301.

Impact resilience: Conforms to JIS K6301.

tan δ: Measured using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho under the conditions of elongation deformation at a strain rate of 10 ± 2% and a frequency of 20 Hz.

Actual vehicle wear resistance index: It is installed on all wheels of a flat-body 10 ton vehicle, the residual is measured after running 60,000 km on general road surface, the running km per 1 mm is calculated, and the tire N
The tires of o.1 were indexed as 100. Therefore, the larger the index, the better the abrasion resistance.

High-speed durability: The load was cumulatively increased in the time steps shown in the table below, the vehicle was run at a constant speed of 55 km / HR, and an indoor durability test was conducted according to the so-called FMVSS NO119 conditions at which step the failure occurred. Is displayed as an index with the mileage of 100 as.

Therefore, the larger the index, the better the durability.

Wet skid resistance: Speed 40 at actual wet condition on wet asphalt road
Sudden braking was applied at speeds of km / h and 70 km / h, and the mileage until complete stopping was measured and indexed using the following formula.

Therefore, the larger the value, the better.

As is clear from Table 1, the tread rubber composition of the present invention has higher impact resilience and smaller loss tangent (tan δ) than the rubber compositions of Comparative Examples. In addition, the breaking property is also reduced to a lesser extent than when the high cis polybutadiene rubber is blended.

According to Table 2 showing the results of the indoor test and the outdoor actual vehicle test of the tires using the rubber compositions of the compound Nos. 1 to 5 as tires, according to the tires of the present invention of the tire Nos. 4 and 5, Compared with the tire of the comparative example, rolling resistance is low, that is, fuel economy is good, and high-speed durability is also greatly improved.
The abrasion resistance of the actual vehicle is also improved as in the case of blending the high cis polybutadiene rubber, and the reduction in wet skid resistance is clearly preferable because the blend of the modified polybutadiene rubber of the present invention is smaller than the blend of the high cis polybutadiene rubber.

〔The invention's effect〕

As described above, the rubber composition of the present invention using the modified (modified) polybutadiene rubber has a wear resistance and a wet skid resistance without any loss as compared with a usual blend of high cis polybutadiene rubber. It is suitable for large high-speed pneumatic tires because it has low rolling resistance and significantly improved high-speed durability.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shuichi Akita 5-3-3 Inamura Gasaki, Kamakura City, Kanagawa Prefecture

Claims (1)

[Claims] 1. The following formula in the polymer molecular chain: Blending polybutadiene rubber having an atomic group represented by 20 to 40 parts by weight of polyisoprene rubber 60 to 80 parts by weight,
40 to 150 mg / g of iodine adsorption and 40 nitrogen specific surface area per 100 parts by weight of blended rubber with the total amount being 100 parts by weight
~ 150m ² / g, DBP oil absorption 60 ~ 140ml / 100g, 30 ~ 90 parts by weight of carbon black having a specific coloring power of 80 ~ 130 is compounded, rubber composition for large pneumatic tires for high speed object.