JPH03281551A - Tire - Google Patents

Abstract

PURPOSE:To obtain an abrasion-resistant pneumatic tire excellent in durability by using a rubber composition prepared by blending natural rubber and diene- based synthetic rubber with specific carbon black and using the resultant rubber composition in a cap part of tread rubber. CONSTITUTION:The objective tire, having a tread rubber composed of a two- layer structure of cap rubber in the tread surface part and a base rubber in a part contacting a belt and obtained by blending (A) natural and diene-based synthetic rubber such as polyisoprene or butadiene rubber with (B) carbon black having <=52nm half-value width of aggregate particle diameter distribution of primary particles and numerical values in measuring units of colloidal characteristics in the following relationships (R) and using the resultant rubber composition as a rubber composition in the aforementioned cap part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a tire with high wear resistance and excellent durability.

(Prior Art) In recent years, competition in wear resistance has become more intense in truck and bus tires, and it has become impossible to obtain better wear resistance with conventional S AF (N 110>carbon).

Therefore, attempts have been made to improve the abrasion properties by (1) using carbon with an even smaller particle size, (2) increasing the blending amount, and (2) not blending oil or plasticizer.

The reinforcing properties of carbon black are correlated with the specific surface area per unit weight. Carbon black with a small primary particle diameter and a large specific surface area has a large interaction between the carbon black surface and rubber molecules, and carbon black with a small specific surface area Rubber composition containing black has better wear resistance, tensile strength,
Hardness tends to increase, and carbon blacks for rubber are ranked in order of increasing specific surface area, SAF grade (Super A).
brasionFurnaee), I SAF
Class (I nLerwediate Super
Abrasion Furnace), HAF class (High Abrasion Furnaee)
It was used as a guideline for selecting carbon black types.

However, conventional rubber compositions containing SAF grade carbon black do not have the expected wear resistance due to their large specific surface area, and have poor processability. l5 on the tread of bus tires
HAF grade carbon black was used for AFi & heavy duty passenger tires that place emphasis on road grip.

The reason why SAF grade carbon black has low wear resistance despite its large specific surface area is thought to be as follows.

Since SAF grade carbon black has a large specific surface area, it also has a large surface activity, and therefore has a large effect of agglomerating the primary particles of carbon black to form aggregates, and the aggregates are difficult to break during mixing into rubber.

On the other hand, car pump hooks dispersed in the rubber in the state of primary particles adsorb rubber molecules and have a large effect of increasing the viscosity of the rubber during mixing, reducing the mixing workability and leaving the rubber in the state of primary particles. Difficult to disperse within. Destruction of aggregates M! Due to the combination of difficulty in mixing and poor mixing workability, the rubber was dispersed in the form of aggregates, making it appear as if large particle size carbon black had been blended.

In order to destroy the aggregates, the viscosity of the rubber being mixed can be increased so that a large shearing force is applied. On the other hand, when the rubber viscosity becomes low, the aggregates become compacted.

Therefore, the particle size distribution of conventional SAF grade carbon black aggregates is widened, and at the beginning of the mixing process, the rubber viscosity is increased by small particle size aggregates to increase the aggregate breaking effect.
As the aggregates are destroyed, the rubber viscosity increases without a sudden rise, and the shearing action gradually increases, thereby destroying the aggregates and dispersing them into primary particles. However, with this method, large aggregates remain in a compacted and hardened state, making it difficult to uniformly disperse them in the form of primary particles.

In addition, as the particle size becomes smaller, attempts have been made to widen the aggregate distribution width in order to improve dispersibility and heat generation properties, but current manufacturing techniques are still far from sufficient.

The purpose of the present invention is to solve the above-mentioned conventional problems by creating a tire with high reinforcing properties and high wear resistance by using a specific carbon black that has not been considered in the past. To provide a pneumatic tire with excellent durability by using a rubber composition for a cap part of a tire tread part having a cap base structure.

(Means for Solving Problem 11) The above object of the present invention is to provide a radial tire in which the tread rubber has a two-layer structure of cap rubber on the tread surface portion and base rubber on the portion in contact with the belt, and to provide a rubber composition for the cap portion. As a result, the half-width of the aggregate particle size distribution of primary particles is 52
This can be achieved by using a rubber composition blended with carbon black whose colloidal properties have a measurement unit of nm or less and have the following relationship.

(A) 140≦N, SA (unit m'/g)≦160 (B
) N, SA (unit: so'/g) - IA (unit: mg/g) ≦
5(C)N, SA (unit horse mackerel 2/g) - CT A B (
Unit m2/g)≦5 (Di00≦24M4DBP (unit -1/100g)≦
120 The present invention eliminates the need to reduce chemically active sites such as quinone groups on the surface of carbon black particles to weaken the cohesive force of primary particles and widen the distribution of aggregate particle sizes to improve dispersibility. On the other hand, aggregates with large particle diameters remain in the rubber without being destroyed even if the surface activity is lowered, so we used carbon black that had a lower content of aggregates with large particle diameters and improved dispersibility in the rubber. This tire has a tread with a two-layer structure in which the cap rubber is made of a rubber composition with good wear resistance and the base rubber is made of a low heat generation rubber composition.

In the present invention, the nitrogen adsorption specific surface area is abbreviated as N2SA, and is measured in accordance with ASTM D3037, and its unit is w2/g, and the iodine adsorption amount is abbreviated as IA, J
It is measured according to IS K6221 and its units are sog/g. Cetyltrimethylammonium promyr adsorption specific surface area value is abbreviated as CTAB, ASTM
D3765, the units are 1/1. It's oog. The aggregate distribution of 4 is Noyois.
Using Lable's Disc Cent U 7 Nino,
Add carbon black to a 20% ethanol aqueous solution to a concentration of 50 mg/l and disperse well, and use this as a sample.

The disk was rotated at 8000 rpm and the spin solution (2
% glycerin solution) into the central opening of the disc, then 1-r of buffer solution (ethanol aqueous solution) is injected, and then 0.5a+f of the sample is injected and measured. Stokes mode diameter (D
The distribution of st) is shown in a graph as shown in Fig. 1, and the half-width shown in the figure is abbreviated as ΔDst, and its unit is nm.
It is.

In the present invention, the above-mentioned specific carbon blacks are used and will be explained below.

(A) 140≦N, SA≦16O N 2 S If A is less than 140, wear resistance and strength will be poor, and if it is greater than 160, the specific surface area will be large and the cohesive force will be too large, resulting in poor dispersibility and workability. becomes worse.

(B) N, SA-I A≦5 This index represents the surface activity of carbon black, and the higher the index, the better the bond with rubber and the improvement in heat generation, but the greater the cohesive force and the worse processability. There is a tendency. 5
If it is larger, the balance between heat generation and workability will be disrupted, and workability will deteriorate.

(C)N, 5A-CTAB≦5 This index indicates the presence or absence of microscopic pores in carbon black. The larger the index, the more pores there are, but if it is larger than 5, there are too many micropores, which may combine with rubber molecules and form a gel. This causes deterioration in workability.

(If D100≦24M4DBP≦120,100, sufficient abrasion resistance cannot be obtained, and if it is larger than 120, the rigidity is too large, the toughness decreases, and problems such as chipping occur.

(E), A, Dsi≦52 If it is larger than 52, the abrasion resistance will not be improved because the dispersion is as poor as that of general carbon. The smaller ΔDsL is, the
Although it is good in the present invention, the current limit is about 30th place.

In the present invention, as the rubber component, at least one selected from natural rubber and diene-based synthetic rubber is used, and as the diene-based synthetic rubber, for example, polyisoprene rubber (IR
), polybutadiene rubber (BR), and styrene-butanoene rubber (SBR), and modified products thereof, blends thereof, etc. can be used. It is also possible to use a blend of a small amount of modified isoprene-ibbutylene rubber (TTR) or ethylene propylene diene rubber (EPDM).

In the present invention, the above carbon black is usually used in an amount of 30 to 80 parts by weight, preferably 4 parts by weight, per 100 parts by weight of the rubber component.
Use 0 to 70 parts by weight. If it is less than 30 parts by weight, sufficient abrasion resistance cannot be obtained, and if it is more than 80 parts by weight, the viscosity of the unvulcanized rubber increases too much, making processing difficult, and the heat generation property of the vulcanized rubber also deteriorates.

In the tire of the present invention, the above-mentioned components are processed using conventional processing equipment, such as a
It can be manufactured by a conventional method using a rubber composition obtained by kneading with a rubber mixer, a Banbury mixer, a Nigu, etc. for the cap tread part. In addition to the above-mentioned components, it is of course possible to add known vulcanizing agents, vulcanization accelerators, vulcanization accelerators, vulcanization retarders, reinforcing agents, plasticizers, anti-aging agents, tackifiers and the like.

The tire can be produced by any known method except for using the above-mentioned rubber composition as the rubber for the captres. Base rubber compositions with particularly low heat generation include natural rubber (NR), butanoene rubber (BR), styrene-butanoene rubber (SBR), inbrene rubber (IR,
) etc., it is preferable to use a rubber composition containing a relatively large amount of highly reinforcing carbon black of HAF or higher and a relatively small amount of oil.

The thickness of the cap rubber is such that the cap rubber has good wear resistance, at least until the tread wears and the grooves of the tread pattern almost disappear. Since the cap rubber has a lower modulus than the base rubber, a step in rigidity occurs at the interface between the cap rubber and the base rubber, and shear stress concentrates.On the other hand, shear stress due to the shape concentrates at the bottom of the groove, so both In order to prevent cracks at the groove bottom due to the interaction of shear stress, the interface between both rubbers should be 0.0
．． Preferably, 5 to 5 rings are separated.

(Effect of the invention) The carbon black of the present invention is opposite to the conventional improvement method,
By reducing the half-width of the aggregate diameter as much as possible, we increased dispersibility and significantly improved wear resistance. On the other hand, processability,
A rubber composition containing carbon black with a large specific surface area and greatly improved dispersibility has a relatively high heat generation property, so in the present invention, by using this in the cap part of a tire with a cap base structure, the rubber composition has a relatively high heat generation property. durability,
Significantly improved wear resistance.

(Example) Examples and comparative examples will be explained below. In addition, "part" simply indicates the weight of the part.

Examples and Comparative Examples 100 parts of the rubber component listed in Table 1, each part of carbon black having the properties listed in Table 1, 3 parts of zinc white,
1.5 parts of stearic acid, 1 part of paraffin wax, 1 part of oil, anti-aging agent [Santoflex 13, N
-(1,3-dimethylbutyl)-N-phenyl-p-phenylenenoamine) 2%, 7Xl sulfur accelerator (CBS) 1
and 11.8 parts of sulfur were kneaded in a Banbury mixer for 4 minutes to obtain a rubber composition for a cap tread.

Abrasion resistance was evaluated using a 1000 R20 tire using the above-mentioned rubber composition as a cap tread rubber prepared by a conventional method on an actual vehicle, and expressed as an index with formulation No. 11 set as 100. The larger the value, the better. The results are also listed in Table 1.

In addition, durability is determined by running the above tire in a bench durability test (drum) until it breaks down, and calculating the mileage by compounding N.
, o, 1 was set as 100 and expressed as an index.

The larger the size, the better the durability.

In addition, as a base rubber composition, NR, (100 parts),
TSAF carbon black 30 parts, 70 gusset oil 1 part, zinc white 3 parts, stearin #1.5 parts, anti-aging agent (Santoflex 13) 1 part, paraffin wax 1 part, vulcanization accelerator (CBS)] and 1.8 parts of sulfur were mixed in a Banbury mixer for 4 minutes.

Table 1 Decay (Continued) Blends Nos. 1 to 5 are comparative examples, while Nos. 1 and 2 are conventional Nll0. It is N220. Blend No.

Based on No. 1, Blending No. 12 has poor abrasion resistance, and Blending No. 083 has too small particle size and is poor in both abrasion resistance and durability. Formulation No. 4 has high surface activity and poor dispersion, and although the durability is improved by making it a cap base,
Poor wear resistance. Compound No. 005 has poor durability because it is not based on Toyatsubu.

On the other hand, in the example, by adopting a cap-based structure, the durability can be dramatically improved without deteriorating the good abrasion resistance6.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the distribution of carbon black aggregates. (Above) Consultant, Toyo Rubber Industries Co., Ltd. Representative Patent Attorney 1) Iwao Mura

Claims (1)

[Claims] (1) In a radial tire in which the tread rubber has a two-layer structure of cap rubber on the tread surface and base rubber on the part in contact with the belt, the rubber composition of the cap part is at least one of natural rubber and diene-based synthetic rubber. A tire with a cap-based structure characterized by using a rubber composition blended with carbon black in which the half-value width of the aggregate particle size distribution of primary particles is 52 nm or less and the numerical values in the measurement unit of colloidal characteristics are in the following relationship. . (A) 140≦N_2SA (unit m^2/g)≦160 (B) N_2SA (unit m^2/g) - IA (unit mg
/g)≦5 (C)N_2SA (unit: m^2/g) - CTAB (unit: m^2/g)≦5 (D)100≦24M4DBP (unit: ml/100g)
≦120