JPH0643525B2 - Rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition having excellent cut resistance and chipping resistance.

(Prior Art) As a method for improving the cut resistance of a tire, there is a method in which a large amount of a reinforcing filler such as carbon black, silica, clay, or calcium carbonate is added to a rubber composition. There is a drawback in that self-heating is large at the time of intended use and blowout destruction may occur, or chipping destruction may occur due to impact, and workability at the time of mixed molding is poor. There is also a method of compounding a rubber composition with a reactive resin such as resorcin resin / hexamine, but the Mooney viscosity of the mixed rubber is high and the scorch is fast.
There is a problem in terms of processability.

In addition, styrene-butadiene rubber (SB
There is also a method of using a large amount of R), but in this case, self-heating during dynamic use is large, which is problematic in use under high temperature dynamic conditions in combination with deterioration of fracture properties of such a compound at high temperature. There is. On the other hand, when a non-reactive resin such as a _C5-9 petroleum resin is blended with a rubber composition, it is said to be useful for cut resistance from the viewpoint of breaking energy and breaking elongation at high temperature. However, the self-heating is large and the processability is improved, but the improvement of the cut resistance is small for the improvement. If process oil is added as a softening agent to improve processability, the cut resistance is largely impaired for the original purpose.

(Problems to be Solved by the Invention) In the present invention, when Mooney viscosity of a rubber composition is increased by blending tung oil with a carbon black having a small particle size for increasing cut resistance and chipping resistance, and silica. It has been found that it has the effect of preventing and further improving the cutting resistance and chipping resistance.The purpose is to improve the cutting resistance and chipping resistance under dynamic use conditions without impairing other performance. To provide a rubber composition having excellent properties.

(Means for Solving Problems) The present invention relates to 100 parts by weight of rubber, 35 to 50 parts by weight of carbon black having an arithmetic average particle diameter of 20 nm or less by an electron microscope, 5 to 20 parts by weight of rubber-reinforcing highly active silica. And tung oil 1 to
The present invention relates to a rubber composition having improved cut resistance and chipping resistance, which is characterized by containing 15 parts by weight.

In the present invention, as the rubber component, one type or two or more types of natural rubber (NR) and synthetic rubber are used. Examples of synthetic rubber include polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SB
R), isoprene / isobutylene rubber (IIR), ethylene / propylene / diene rubber (EPDM), modified products thereof, blended products thereof and the like can all be used.

In the present invention, 35 to 50 parts of carbon black having an arithmetic mean particle size of 20 nm or less by an electron microscope is used for 100 parts of rubber (parts by weight, the same applies hereinafter). Here, the arithmetic mean particle size (dn) by an electron microscope means that a carbon black sample is dispersed in chloroform by an ultrasonic cleaning method (dispersion conditions include, for example, ultrasonic cleaning at a frequency of 28 kHz for 30 minutes) and then dispersion. The sample is fixed on a carbon support film, and the sample is directly magnified by an electron microscope at a magnification of 40,000 and overall magnification of 160,000 to 20
The diameter of 1,000 carbon black particles was measured from the obtained electron micrograph taken at a magnification of 0,000, and the average particle diameter (dn) nm was calculated by arithmetic mean from the histogram of 1 nm section.
I asked. If the particle size exceeds 20 nm, improvement in cut resistance and chipping resistance is insufficient. The amount of carbon black blended is preferably 35 to 50 parts per 100 parts of rubber.
The amount of highly active silica compounded is preferably 5 to 20 parts per 100 parts of rubber. Generally, the smaller the average particle diameter of the carbon black to be blended, the better the chipping resistance and cut resistance of the rubber composition, but the higher the Mooney viscosity of the rubber composition before vulcanization. Silica also has a higher Mooney viscosity than carbon black. Average particle size is 20 nm
The rubber composition containing the above-mentioned carbon black having a small particle diameter and silica has a high Mooney viscosity, which is poor in processability and poor in practical use. Therefore, a softener is added to lower the Mooney viscosity. Usually, petroleum-based process oil is blended as a softening agent, but tung oil is used because process oil has a great adverse effect on cut resistance and chipping resistance. Tung oil is liquid at room temperature, and about 80% of the constituent fatty acids are eleostearic acid. Compared to linseed oil, it has high viscosity, high refractive index, and high degree of unsaturation, and has good drying properties. Eleostearic acid has a double bond as a conjugated double bond. When heated with a metal compound such as cobalt or zinc as a catalyst, it polymerizes to become a solid, and when oxygen is present, the polymerization reaction is accelerated. When mixed with rubber, it acts as a softening agent in the process,
In the vulcanization process of a rubber product, zinc white, which is an essential component of the rubber composition, is used as a catalyst to carry out a polymerization reaction, and when it becomes a rubber product, a further polymerization reaction is carried out on the surface part that comes into contact with oxygen in the air. Becomes solid. Since softening agents such as process oil are liquid even after vulcanization, they act as plasticizers to weaken the cohesive force of rubber and reduce cut resistance, chipping resistance, abrasion resistance, etc. Since it is solid, the cut resistance, chipping resistance, wear resistance and the like are not deteriorated. The amount of paulownia oil is 1 for 100 parts of rubber
The content is preferably up to 15 parts. Within this range, tung oil acts as a softening agent to improve processability and cut resistance and chipping resistance.

In the present invention, in addition to the above components, known vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, vulcanization retarders, organic peroxides, antioxidants, tackifiers, colorants, etc. can be added. Of course.

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

(Effects of the Invention) In the present invention, the rubber composition obtained by blending the rubber composition with carbon black having a specific particle diameter, highly active silica and tung oil has a processability, a cut resistance and a chipping resistance. Is excellent in.

(Example) Below, an example and a comparative example are given and demonstrated. Incidentally, "parts" means "parts by weight".

Examples 1-8 and Comparative Examples 1-8 100 parts of natural rubber, 3 parts of zinc white, 1.5 parts of stearic acid, antioxidant (6C, 1,3-dimethylbutyl-phenyl-p-
2 parts phenylenediamine), 2 parts sulfur, accelerator (CB
S) 1 part and carbon black, silica, process oil or tung oil described in Table 1 were kneaded with a Banbury mixer to obtain a rubber composition.

The Mooney viscosity of the obtained rubber composition was measured as ML _{1 + 4} according to JIS K6300.

Also, using the obtained rubber composition, tire size 6.50R16
Was used for the tread portion of the tire, and the cut resistance was evaluated from the reciprocal of the sum of the product of the length and number of cut scratches per unit area of the tread surface after running on a rough road for 20,000 km.
Is displayed as an index. The larger the value, the better.

Also, the chipping resistance is the force (kg) when the JIS K6301 tear sample A type sample is broken at a deformation speed of 5 m / sec.
f / cm) was indexed with Example 1 being 100. The larger the value, the better. The results are shown in Table 1.

Claims (1)

[Claims] 1. 100 to 100 parts by weight of rubber, 35 to 50 parts by weight of carbon black having an arithmetic mean particle size of 20 nm or less by an electron microscope, 5 to 20 parts by weight of rubber-reinforcing highly active silica, and at least 80 parts of eleostearic acid. % Of a tung oil containing 1% by weight of a tung oil, the rubber composition having improved cut resistance and chipping resistance.