JPH04117439A - Rubber composition and pneumatic tire produced therefrom - Google Patents

Abstract

PURPOSE:To prepare a rubber compsn. having a high surface roughness and an excellent slip resistance by compounding a rubber with a filler comprising a carbonaceous powder having a specified mean particle diameter or a chemically surface-modified carbonaceous powder. CONSTITUTION:100 pts.wt. rubber is compounded with 3-150 pts.wt. filler comprising at least one powder selected from the group consisting of a carbonaceous powder (e.g. carbonaceous mesophase minute particles) and a chemically surface- modified carbonaceous powder and having a mean particle diameter of 0.5-200mum, thus giving a rubber compsn. having a surface roughness (JIS-B0601, a mean roughness on the central line, Ra) of 2mum or higher and an excellent slit resistance. The compsn. is used as a tread material for producing a pneumatic tire improved in derivability, brakability, and controllability on an icy road.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anti-slip rubber composition and a pneumatic tire. More specifically, it relates to an anti-slip rubber composition that has significantly improved anti-slip properties, particularly the coefficient of friction on ice and snow, without impairing the excellent elasticity and durability of the rubber material, and a rubber using this rubber composition. There are various types of products, but when it comes to tires, we have all-season pneumatic tires that have significantly improved driving performance, braking performance, and maneuverability on icy and snowy roads without compromising maneuverability and durability in the summer. Regarding.

(Conventional technology) In recent years, dust caused by spiked tires has become a major social problem, and studless tires that do not use spikes or chains and have good driving, braking, and maneuverability on ice and snow have been developed and are rapidly becoming popular. However, it is still difficult to say that they have sufficient ice and snow performance compared to spiked tires.

Furthermore, so-called all-season tires that can be used in the winter as well as in the summer have the same dry grip, wet grip, handling stability, and durability in the winter as in the summer.
No fuel has been obtained that has low fuel consumption and sufficient drivability even on ice or snow.

In addition, in Japan, where we are facing an aging society, falls and fractures in elderly people are often fatal, and ensuring safety is an important issue. Shoes are in demand.

On the other hand, for the same purpose, it is desired to improve the anti-slip properties of facilities such as building floors, stairs, and roads.

In order to meet the above demands, various structural improvements have been investigated, and improvements have also been made to rubber compositions, but the current situation is that nothing with sufficient performance has yet been obtained.

Conventional methods for improving the coefficient of friction on ice and snow include using polymers with a low glass transition point and adding large amounts of softeners and plasticizers to ensure rubber elasticity at low temperatures. JP-A-55-135149, JP-A-58-199203, JP-A-60-137945
Publication No.) etc. are known.

Although the former has a moderately high coefficient of friction on ice and snow, it has the problem of insufficient physical properties and durability at room temperature, while the latter has poor abrasion resistance and poor adhesion to metals, etc., despite its effectiveness. There was a problem.

That is, although rubber compositions containing polymers with a low glass transition point or rubber compositions containing large amounts of softeners and plasticizers exhibit good frictional properties in ice and snow at relatively low temperatures of -5°C or lower, A sufficient coefficient of friction cannot be obtained on wet ice and snow at around 0°C, and it cannot be said that the performance as a rubber composition for studless tires, anti-slip shoes, etc. is satisfied.

Regarding tires in particular, although they show good performance on ice and snow in the relatively low temperature range of -5℃ or lower, so-called dry-on-ice, they do not perform well in wet conditions near 0℃.
In terms of performance on ice and snow, so-called wet on ice, a sufficient coefficient of friction cannot be obtained, and it cannot be said that driving performance, braking performance, and maneuverability have been sufficiently improved.

(Objective of the Invention) The first object of the present invention is to provide excellent anti-slip properties without sacrificing the excellent elasticity and durability of rubber materials, which can be used not only on ice and snow at low temperatures, but especially on ice and snow in wet conditions. The object of the present invention is to provide a rubber composition having a significantly improved coefficient of friction.

The second object is to provide a rubber article using such a rubber composition, particularly a studless tire or an all-season tire.

In other words, when it comes to tires among rubber products, we provide a tread rubber composition that significantly improves the coefficient of friction on ice and snow without impairing maneuverability and durability in summer (and shoes, which is one of the rubber products). We provide a rubber composition for soles that maintains appropriate rubber elasticity and abrasion resistance and has excellent anti-slip properties even on torpedoes, and has excellent anti-slip properties for roads and various flooring applications. The present invention provides a rubber composition having appropriate rubber elasticity and excellent durability.

(Means for Solving the Problem) The present inventors have discovered a method to increase the coefficient of friction on ice and snow in a wet state, which was most difficult with conventional techniques. The present invention was completed by discovering that the coefficient of friction under such conditions could be increased by incorporating the filler described above.

That is, the first aspect of the present invention is to use carbonaceous fine powder having an average particle size of 0.5 to 500 μm, more preferably 2 to 150 μm, or a carbonaceous fine powder whose surface has been chemically modified to 3 to 3 to 100 parts by weight of rubber. Surface roughness (JIS B060
1. The present invention relates to a rubber composition having a center line average roughness (Ra) of 2 μm or more.

As for the second aspect of the present invention, which is a tire as a rubber article, the rubber of the tread portion has an average particle size of 0.5 to 5.
00 μm filler to 100 parts by weight of rubber.
~150 parts by weight, more preferably 3 to 100 parts by weight, to achieve a surface roughness of 2 μm or more, and the filler is at least one selected from carbonaceous fine powder and carbonaceous fine powder whose surface has been chemically modified. A rubber composition characterized in that it is one or more types of powder, and specifically, for example, the tread portion is filled with carbonaceous menphase small spheres, and the surface roughness of the tread portion of the tread is 2 to 2. 300 μm, and in terms of formulation, the tread part has an average particle size of 0.5 to 50 μm.
The carbonaceous mesophase small spheres of 0L1m are distributed in an amount of 3 to 100 parts by weight per 100 parts by weight of rubber.

Carbonaceous fine powder suitable for the present invention includes: (1) finely pulverized coal tar pitch, petroleum pitch, pitch obtained by thermally decomposing polyvinyl chloride, and (2) those obtained by heat-treating these pitches or tar components. It is a fine powder obtained by dissolving the pitch component of the obtained carbonaceous mesophase small spheres, that is, optically anisotropic small spheres formed by heating with a solvent, and then finely pulverizing it, a pitch raw material. into bulk mesophase (for example, see Japanese Patent Publication No. 59-30887) by heat treatment, and finely pulverize it, or finely pulverize partially quality pitch, ■Thermosetting resins such as phenolic resins. Examples include so-called low-temperature-treated carbonaceous fine powders, such as those carbonized at low temperatures; Examples include carbon spheres obtained by heating a mixture of a chlorine-containing polymer such as polyvinyl chloride or polyvinylidene chloride under pressure, or finely pulverized carbon spheres thereof.

Among these, particularly suitable carbonaceous fine powders have a carbon content of 80 to 97% by weight and a carbon/hydrogen atomic ratio of 1.2 to 97% by weight.
5, carbonaceous mesophase small spheres and low temperature treated carbonaceous fine powder.

Powders obtained by chemically modifying these carbonaceous fine particles, such as by grafting a high molecular weight polymer onto the surface, are also suitably used.

The rubber composition of the present invention has a surface roughness (JIS-B0601, center line average roughness Ra) of 2 due to the blending of the filler described above.
μm or more, and the flexible rubber matrix phase and hard filler phase are moderately dispersed, which increases the interaction with ice and snow and provides great anti-slip properties (large coefficient of friction) even on wet ice and snow. Demonstrate.

The particle size distribution of the filler does not need to be particularly limited as long as it is a granule made by a normal manufacturing method, but more preferably a fine powder of 1/10 or less of the average particle size and a fine powder of 10 times or more of the average particle size. It is desirable to remove as much as possible (the total volume fraction of both is preferably 10% or less).

The rubber composition of the present invention is a composition in which the filler of the present invention is filled into a rubber composition consisting of a rubber material commonly used for various uses, a filler, an anti-aging agent, a vulcanizing agent, and a vulcanization accelerator. There are no particular limitations on the rubber composition other than the filler of the present invention.

In the filler of the present invention, the average particle size of the filler is 0.5μ
If it is less than 500 μm, particularly excellent anti-slip effect cannot be obtained.
Exceeding this is not preferable because the durability of the rubber composition decreases.

Furthermore, if the amount is less than 3 parts by weight, the effect of improving the coefficient of friction on wet water will be small, and if it exceeds 150 parts by weight, the durability of the rubber composition will be greatly reduced, which is not preferable.

Especially for tires using a single rubber composition as the tread rubber, if the surface roughness is less than 2LLm, a sufficient coefficient of friction on ice cannot be obtained;
A surface roughness exceeding 20% is undesirable because it reduces wear resistance.

The present invention has an average particle size of 0.5 parts by weight per 100 parts by weight of rubber.
Fillers of the invention, e.g.
To provide a pneumatic tire having a rubber composition in the tread portion containing ~100 parts by weight, preferably 10 to 60 parts by weight, and in this case, the particle size is 0.5 μm.
If the amount is less than 3 parts by weight, a sufficient coefficient of friction will not be obtained on icy and snowy roads, and if the particle size exceeds 500 μm or the amount exceeds 100 parts by weight, the wear resistance will decrease. , both are unfavorable.

Furthermore, the surface roughness of the tread portion refers to the microscopic area within the tread surface that substantially contacts the road surface, and refers to the roughness inside the tread block defined by the tread pattern, sipes, etc.

The rubber composition constituting the matrix part of the tread part is composed of a composition normally used as a tread for summer tires, that is, a usual rubber, a filler, an anti-aging agent, a vulcanizing agent, and a vulcanization accelerator. It's not something you do. Therefore, the handling stability, durability, and fuel efficiency required in summer are not particularly impaired by the method of the present invention.

(Example) The present invention will be explained in more detail with reference to the following example.
The present invention is not limited in any way by this example.

Examples 1 to 3, Comparative Examples 1 to 4 Table 1 shows the formulation contents and test results using the carbonaceous fine powder of the present invention.

In Example 1, a powder consisting of Menphase small spheres (average particle size 20 Im) was added to the tire tread rubber compound (Comparative Example 1).
An example was shown in which 50 parts by weight of was added, but the effect of improving the coefficient of friction on ice was remarkable, and the decrease in elongation and strength, which are related to durability, was small.

Example 2 shows an example in which 20 parts by weight of powder made of mesophase small spheres (average particle size 10 μm) was added to a different type of tire tread rubber compound, and the effect of improving the coefficient of water friction was remarkable, and the strength and It maintains a sufficient level of growth.

In Example 3, 5 carbonaceous fine powders (average particle size 20 μm) obtained by heat-treating thermosetting phenolic resin at low temperatures were added to the rubber compound for shoe soles (Comparative Example 5) with excellent cold resistance and durability.
An example in which 0 parts by weight was blended is shown. The improvement in the coefficient of friction on water is remarkable, and the strength and elongation also maintain sufficient levels.

As is clear from the comparative examples, the effects of the present invention cannot be obtained even if the blending amount is too small (comparative example 2) or if the average particle size is too small (comparative example 4). Furthermore, if the blending amount is too large (Comparative Example 3), the strength and elongation are greatly reduced and it is not suitable for practical use.The various test methods are as follows.

(11 Surface Roughness The center line roughness (Ra) described in JIS Surface Roughness (B0601) was used.

That is, using a stylus-type roughness meter (manufactured by Koita Institute), a rubber vulcanizate sample cut into a specified size (10 mm x 10 mm, thickness 5 mm) was measured with a radius R of the tip of the stylus = 2 μm, and a measuring force of 0. Under measurement conditions of .7 mN and a measurement scanning length of 2.5 mN, measurements were taken on the sample surface at 10 points at 0.5 mm intervals in the length direction of the sample and averaged.

(2) Coefficient of friction on ice The coefficient of friction on ice in a wet state near 0℃ is calculated by contacting the sample surface whose surface roughness has been measured with ice at a surface temperature of -0.5℃. It was measured using a coefficient meter.

The measurements were as follows: overcurrent 2 Kg/cm", sliding speed I Qmm/
sec and an ambient temperature of -2°C, the surface state was approximated to a mirror surface.

(3) Rubber strength (tensile strength) and elongation JIS-63
Measurements were made on samples punched out from each rubber composition sheet in accordance with 01.

Examples 4 to 7, Comparative Examples 6 to 9 Various tests were then conducted using pneumatic tires in which the rubber composition of the present invention was used in the tread portion of the tire.

Table 2 shows the formulation and properties of the rubber composition constituting the tread portion, and the performance when used as a test tire.

As is clear from this table, rubber compositions (Examples 4 to 7) in which tread rubber is filled with carbonaceous menphase microspheres
When using a normal tread rubber composition (Comparative Example 6)
It can be seen that the surface roughness of the tire tread becomes more grainy, and the coefficient of friction on ice and the tire braking performance improve accordingly.

At this time, if the filling amount of carbonaceous mesophase small spheres is not sufficient (Comparative Example 7), the surface roughness does not change much and the coefficient of friction on ice does not improve. On the other hand, when the filling amount is too large (Comparative Example 8), the wear resistance is significantly reduced. Further, when the particle size of the carbonaceous mesophase is less than 12 μm (Comparative Example 9), no improvement in the coefficient of friction on ice is observed.

In addition, it can be seen that in all Examples (4 to 7), summer tire performance is secured as compared to the comparative examples in terms of braking performance on wet road surfaces and steering stability on dry road surfaces.

(Al) Braking performance test on ice A test tire PSR (165sR13) was prepared and subjected to a test after normal running for 50Krn as a break-in run.

The same applies to the wear resistance test.

Four of each test tire was mounted on a passenger car with a displacement of 1500 cc, and the braking distance was measured on ice at an outside temperature of -5°C.

The tire of Comparative Example 6 is expressed as an index with 100 as the value, and the larger the value, the better the braking performance.

(bl Wear Test Two test tires for each test were attached to the drive shaft of a passenger car with a displacement of 1500 cc and run on the concrete road surface of a test course at a predetermined speed. The amount of change in groove depth was measured.
It is expressed as an index with 100 representing a level that is acceptable for practical use. The larger the value, the better the wear resistance performance.

(c) Wet road surface braking resistance test On a wet asphalt road surface, at a speed of 40 km/hour,
Sudden braking was applied from each speed of 70 Km/hr and 100 Km/hr, the distance traveled until it came to a complete stop was determined, and the value was expressed as an index with 100 representing a level that would be acceptable for practical use. The larger the value, the better.

(di dry road handling stability test) Lap times were measured on a clear day when driving around a circuit consisting of straight roads, curves, banks, etc., and expressed as an index with 100 representing a level that is acceptable for practical use. The higher the number, the better.

(Effects) According to the characteristic rubber formulation of the present invention, the effect of improving the coefficient of friction on ice is remarkable, and the strength and elongation related to durability are also maintained at a sufficient level.

To put these things into more concrete terms, pneumatic tire tread materials can significantly improve driving performance, braking performance, and maneuverability on icy and snowy roads without impairing handling performance and durability in the summer. It provides tires that are

As sole materials for various types of shoes and footwear, shoes and footwear with excellent safety and significantly improved anti-slip properties on ice and snow and other slippery places can be obtained, and they can also be used in various buildings, roads, and other facilities. The material can be widely applied to the field of rubber products that require high slip resistance, such as highly safe flooring materials and mats with excellent anti-slip properties.

Patent applicant: Bridgestone Corporation

Claims (4)

[Claims] (1) Surface roughness (JISB0601, center line average roughness R
In a rubber composition with excellent anti-slip properties characterized in that a) is 2 μm or more, the filler is at least one type selected from carbonaceous fine powder and carbonaceous fine powder whose surface has been chemically modified. A rubber composition with excellent anti-slip properties characterized by being a powder. (2) In a pneumatic tire equipped with a tread, the surface roughness of the tread can be improved by blending 3 to 150 parts by weight of a filler with an average particle size of 0.5 to 500 μm to 100 parts by weight of rubber. 2 μm or more, and the filler is at least one kind of powder selected from carbonaceous fine powder and surface-chemically modified carbonaceous fine powder. (3) The pneumatic tire according to claim 2, wherein the tread portion is filled with carbonaceous mesophase small spheres, and the tread surface of the tread has a surface roughness of 2 to 300 μm. (4) In the pneumatic tire, a rubber composition containing 3 to 100 parts by weight of carbonaceous mesophase microspheres with an average particle size of 0.5 to 500 μm based on 100 parts by weight of rubber is added to the tread. The pneumatic tire according to claim 2, comprising: