JPH03281547A - Rubber blend composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition for tires excellent in processability with high reinforcing properties and abrasion resistance by blending rubber with a specific carbon black having a small half-value width of aggregate particle diameter distribution. CONSTITUTION:The objective rubber composition obtained by blending (A) 100 pts.wt. natural rubber or diene-based synthetic rubber with (B) 30-80 pts.wt. carbon black having <=52nm half-value width of aggregate particle diameter distribution of primary particles and numerical values in measurement units of colloidal characteristics satisfying 140<=N2SA(m<2>/g)<=160, N2SA-IA<=5 and N2SA-CTAB<=5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubber composition for tires that has high reinforcing properties, high wear resistance, and excellent processability.

(Prior Art) In recent years, the competition for wear resistance in truck and bus tires has become more intense, and the conventional S AF (N 110) carbon is no longer able to obtain superior wear resistance.

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 use 5AFa (Super Abr) in descending order of specific surface area.
asion Furnaee), T S A F class (
EntersediaLe SuperA br
asion Furnace), HAF class (High
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. The tread of tires for
I (A Fa carbon black) was used for AF grade tires for passenger cars that place emphasis on road grip.

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

SAF grade carbon black has a small specific surface area and high surface activity, so the primary particles of carbon black are #
It has a strong action of gathering to form #aggregates, and #aggregates are less likely to be destroyed during mixing into rubber.

On the other hand, carbon black dispersed in the rubber in the state of primary particles adsorbs rubber molecules and has a large effect of increasing the viscosity of the rubber during mixing by -L, so the mixing workability decreases and the carbon black in the state of primary particles adsorbs rubber molecules and increases the viscosity of the rubber during mixing. Difficult to disperse in rubber. Due to the combination of the difficulty of breaking the aggregates and the reduction in mixing workability, the aggregates were dispersed in the rubber and appeared as if they had been blended with large-sized carbon black. In this case, the viscosity of the rubber during mixing can be adjusted so that a large shearing force acts on it, but on the other hand, if the rubber viscosity becomes high, a phenomenon occurs in which aggregates are compacted. Therefore, conventional SAF grade carbon black 4 was used to widen the particle size distribution of the aggregates, and at the beginning of the mixing process, the rubber viscosity was increased by the small particle aggregates to increase the aggregate breaking effect, and the aggregates were broken. As the rubber viscosity increases, the viscosity of the rubber decreases without rising rapidly, and the shearing action gradually becomes thicker, thereby breaking the aggregates and dispersing them into primary particles. However, with this method, the large 4
The Il aggregate remained in a compacted and hardened state, and it was difficult to uniformly disperse it in the state of primary particles.

Furthermore, as the particle size becomes smaller, attempts are being made to widen the aggregate distribution width in order to improve dispersibility and heat generation properties. 5! In terms of construction technology, this method is still far from perfect.

(Problems to be Solved by the Invention) The purpose of the present invention is to use a specific carbon platter that has not been thought of in the past, in order to solve the conventional problems mentioned above, and to achieve a carbon platter that has reinforcing properties and wear resistance. Furthermore, it is our aim to provide a rubber composition for tires with excellent processability.71'
s (Means for Solving the Problems) The above object of the present invention is to provide at least one of natural rubber and tsene-based synthetic rubber with a half-width of aggregate particle size distribution of primary particles of 5.
This is achieved by blending carbon black with a particle size of 2 nm or less and a coroiglue characteristic measured in the following relationship.

(A) 14G≦N2SA (unit mackerel 2/8)≦160 (B
) N2SA (unit m'/g) ~ IA (unit m)! ,/g
)≦5(C)N2SA (unit so'/s) -CTAB(
Unit -2Og)≦5 (D)1.00≦24M4riBP (11th place spear f/100
g)≦120 The present invention reduces the chemically active sites such as quinine groups on the surface of carbon black particles, weakens the cohesive force of primary particles, and widens the distribution of aggregate particle size to improve dispersibility. On the other hand, since aggregates with large particle diameters remain in the rubber without being broken down, it is possible to reduce the content of aggregates with large particle diameters in the rubber. This is a rubber composition with good abrasion resistance that uses carbon black with improved dispersibility.

In the present invention, the nitrogen adsorption specific surface area is abbreviated as N25A, which is measured in accordance with ASTM D3037, and its unit is 11127g, and the iodine adsorption amount is abbreviated as HA.
It is measured in accordance with JIS K6221, and the unit is floor) 1//pi. Cetyltrimethylammo; lamb bromide adsorption specific surface area value is abbreviated as CT
P indicates stock child key, A S T M D
3493, the 11th place is m/710
It is 0g. For the aggregate distribution, use Novois Lable's Disc Sentry 7U 11, JR/-R 20%.
Add carbon black to the aqueous solution to give a concentration of 50 m1i/l and disperse well, and use this as a sample. 80 discs
00 rpm, spin solution (2% glycerin solution > 10-10-2O) was injected into the disk center opening [1 part, then 1 injected buffer 7-Ill (ethanol/-・L aqueous solution), and then Inject 0.5 ml of the sample and measure.The Stokes mode diameter (Dst) measured here
The distribution of ΔDs+ is shown in a graph as shown in FIG. 1, and the half-width shown in the figure is abbreviated as ΔDs+, and its unit is n-.

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

(A) 140≦N2SA≦16ON2SA is 14
If it is less than 0, the wear resistance and strength will be poor, and if it is more than 160, the specific surface area will be large and the cohesive force will be too large, resulting in poor dispersibility and workability, resulting in low wear resistance.

(B) N2SA-■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 the processability. be. 5
If it is larger, the balance between heat generation and workability will be disrupted, and workability will deteriorate.

(C) N2SA-CTAB≦5, im in :: represents the presence or absence of microscopic pores in carbon black; the larger the number, the more pores there are; This tends to cause dels, leading to deterioration in workability.

(D) 1.00≦24M 4 D B P≦12010
If it is less than 0, sufficient wearability cannot be obtained, and if it is greater than 120, the rigidity is too high and the toughness decreases, causing problems such as chipping.

(E) ΔDst≦52 If it is larger than 52, the dispersion is as poor as that of general carbon, so the wear resistance is not improved. The smaller △Dst 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 citric synthetic rubber is used, and examples of the citric synthetic rubber include 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 rubber of inbrene-isobutylene rubber (ITR) or ethylene propylene rubber (EPDM).

In the present invention, the carbon black is usually used in an amount of 30 to 80 parts by weight, preferably 40 to 70 parts by weight, per 1 part by weight of the rubber component. Sufficient wear resistance cannot be obtained with less than 30 layers, and 80 layers! If the amount exceeds 50%, the viscosity of the unvulcanized rubber increases too much, making it difficult to process, and the heat generation property of the vulcanized rubber also deteriorates.

In the present invention, in addition to the above components, known vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, vulcanization slow grave agents, reinforcing agents, fillers, anti-aging agents, tackifiers, etc. can be added. Of course.

The rubber composition of the present invention can be obtained by kneading the above-mentioned components using a conventional processing device such as a roll, a Banbury mixer, or a Nigu.

(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 lIk aggregate diameter as much as possible, we can increase dispersibility and greatly improve wear resistance, reduce the relatively poor processability and dispersibility, reduce surface activity as much as possible, and improve surface fineness. There are also fewer pores (this improves greatly.

(Example) Examples and comparative examples will be described below. Note that parts simply indicate parts by weight.

Examples and Comparative Examples Each part 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, anti-aging 232 parts of agent (N-(1,3-nomethylphthyl)-N-phenyl-p-phenylenediamine, vulcanization accelerator (C
BS) and 1.8 parts of sulfur were kneaded for 4 minutes using a Pan Bali mixer to obtain a rubber composition.

The Mooney viscosity of the obtained rubber composition was determined according to JISK 63Q.
It was measured in accordance with I, and expressed as an index with Blend No. 1 as 100. The smaller the value, the better.

In addition, wear resistance was measured using the above rubber composition as tread rubber.
A tire of 000R20 was prepared by a conventional method, evaluated on a commercial vehicle, and expressed as an index with compound No. 1 set as 100. The larger the value, the better. The results are also listed in Table 1.

Table 1 No. 1 Decay (continued 8) Blend Nos. 1 to 5 are comparative examples, but 1.2 is a conventional Nll0. It is N220. No. 013 has a too small particle radius and is unbalanced, and No. 4 has too large a surface activity. Blend No. 5 also had an appropriate particle size, but the surface activity was unbalanced. In this manner, it can be seen that the balance between Mooney viscosity and abrasion resistance is very poor in the comparative examples. On the other hand, it can be seen that the examples have relatively low Mooney viscosity and good wear resistance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the distribution of carbon black aggregates. (Above) Applicant: Toyo Rubber Industries, Ltd.

Claims (1)

[Claims] (1) At least one of natural rubber and citric synthetic rubber is blended with carbon black whose half-value width of the aggregate particle size distribution of primary particles is 52 nm or less and whose colloidal characteristics have the following relationship in measurement unit. A rubber compound composition characterized by: (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)-CT
AB (unit m^2/g)≦5 (D)100≦24M4DBP (unit ml/100g)
≦120