JPH02235945A - Rubber composition - Google Patents

Abstract

PURPOSE: To obtain vulcanized rubber having high hardness, excellent in processability and destruction characteristics, improved in abrasion resistance and thermal deterioration resistance and low in heat build-up by compounding natural rubber or synthetic rubber with the proper amt. of specific carbon fibril aggregate.

CONSTITUTION: Carbon fibrils (containing 50% or more of aggregate with the longest diameter of 0.25 mm or less and a diameter of 0.10-0.25 mm formed by the entanglement of carbon fibrils with a diameter of 3.5-70 nm and a length about 10² times or more the diameter) in an amount of 5-90 pts.wt. and 100 pts.wt. of natural rubber and/or synthetic rubber (B) are compounded to obtain a rubber compsn. Further, 1-30 pts. of the above mentioned carbon fibrils and the 5-60 pts. of carbon black are blended with 100 pts. of a rubber containing at least 50 wt.% of natural rubber to obtain the another rubber compsn. Furthermore, 1-30 pts. of the above mentioned carbon fibrils and 100 pts. of oil-resistant rubber are blended to obtain a rubber compsn. for an oil seal.

COPYRIGHT: (C)1990,JPO

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a novel rubber composition having excellent fracture properties, abrasion resistance, heat deterioration resistance, low heat build-up, etc. By blending with rubber, a rubber composition with excellent hardness, processability, breaking properties, etc. can be obtained in a small amount, and furthermore, by combining the above-mentioned specific carbon fibrils and carbon black with a rubber mainly composed of natural rubber. Thai A
The present invention relates to a rubber composition suitable for the tread of No. 7, and further to a rubber composition suitable for an oil seal, in which the specific carbon fibrils are blended with an oil-resistant rubber.

[Prior Art] High-hardness rubber compositions have been widely used not only in the field of vehicles such as automobile parts and tire parts, but also in the field of industrial parts such as rubber rolls, rolling blocks, and pads, and the need for them has been increasing in recent years. At the same time, the required performance has become stricter, and in particular, it is desired that the product performance can be used stably with little change over a long period of time.

The conventional method for obtaining high hardness rubber is to mix large amounts of fillers such as carbon black and whey 1 to carbon, and reduce the amount of oils such as extender oil and plasticizers. It is to be. Furthermore, in order to obtain high-hardness rubber, the concentration of crosslinked networks in the rubber must be increased at the same time, but for this purpose, it is essential to increase the amount of sulfur added in the vulcanization system.

On the other hand, tires used on humanoid vehicles such as trucks and buses, especially radial tires for trucks and buses (abbreviated as TBRI-red), have recently become larger and heavier. As vehicles are now running at higher speeds, there is a strong need for improved performance.

In particular, we have improved wear resistance and reduced heat generation under high loads and high-speed driving, and improved fracture strength to prevent group cuts caused by the tendency to deepen tire treads to ensure handling stability at high speeds. Improving tear properties is an urgent need.

The conventional method for obtaining TBR1~red materials is to use natural rubber, which has excellent breaking and tearing properties and low heat generation properties, and uses highly reinforced material that is effective in improving reinforcement properties, especially abrasion resistance. This method meets the performance requirements of conventional TBR treads, but the performance is insufficient to keep up with recent changes in usage conditions such as high loads and high speed running. There is a strong need to develop new materials.

Furthermore, in rubber compounds for oil seals, solid lubricants such as graphite, molybdenum disulfide, and polytetrafluoroethylene are usually added to the compound in order to reduce the frictional resistance between the lip and shaft of the oil seal. There is. However, these lubricants have poor affinity with rubber, have no reinforcing effect on rubber, and are unfavorable in terms of mechanical strength.

Furthermore, a hard material is required for the oil seal, and for this reason, increasing the amount of reinforcing agent will further reduce the mechanical strength. For this reason, new materials are required.

[Problems to be Solved by the Invention] High hardness rubber can be obtained by conventional methods, but the processability is significantly deteriorated due to the large amount of filler added and the reduced amount of oil added. Furthermore, since the ratio occupied by rubber during the total compounding process is greatly reduced, the rubber elasticity is impaired, resulting in a decrease in fracture properties and abrasion resistance, and a high heat build-up. Furthermore, incorporating a large amount of sulfur inevitably reduces heat deterioration resistance.

In this way, rubber products manufactured by conventional methods are
There are problems such as increased manufacturing cost due to poor processability during manufacturing, low level of physical properties of the product, and short product life, so improvements in this area are strongly desired.

Natural rubber, which is used as the main raw material rubber for TBR treads, exhibits excellent breaking and tearing properties, and these properties are thought to be influenced by the stretch crystallinity specific to natural rubber. On the other hand, the extensional crystallinity decreases with the addition of carbon black, and the degree of the decrease becomes more significant as the reinforcing properties of the carbon black increase and as the amount of carbon black added increases. Furthermore, as the amount of highly reinforcing carbon black increases, the heat generation property of the rubber increases. However, when the amount of carbon black blended is small, the abrasion resistance of the rubber becomes insufficient and elongated crystals do not occur. Also 3
At a low elongation rate of 0.00% or less, the stress is low and it becomes difficult to reach the hardness required for the tread. In other words, with conventional methods, it is almost impossible to balance the higher abrasion resistance, low heat generation, tear resistance, and rupture properties required for recent TBRt-Red materials. There was a strong desire for the invention of

In order to solve the above-mentioned problems regarding the TBRI-Red material, it is necessary to increase the elongation in the low elongation range without impairing the elongation crystallinity of the natural rubber used as the base rubber as much as possible. There is a need to find formulations to replace carbon black that are able to maintain stress and hardness at the required levels and still provide the material with good wear resistance.

Furthermore, for oil seals, it is required to lower the frictional resistance of the rubber surface without impairing mechanical strength.

[Means for Solving the Problems] In order to solve the above problems, the present inventors conducted intensive research and found that if a specific carbon fibril is blended into rubber, it has a remarkable effect of increasing hardness with a small amount. discovered. As a result of further intensive studies, it was surprisingly discovered that equivalent or higher hardness could be obtained with a compounding amount of 172 of commonly used highly reinforcing carbon black (for example, I-IAF grade).

Therefore, the present inventors conducted research to apply this study result industrially, and found that by blending an appropriate amount of the specific carbon fibrils of the present invention into all commercially available rubbers, either alone or in combination, high hardness can be achieved. It has been discovered that a vulcanized rubber with excellent processability and fracture properties, improved abrasion resistance and heat deterioration resistance, and low heat build-up can be obtained.

That is, the present invention has a diameter of about 3.5 to 70 nm,
An aggregate formed by entwining carbon fibrils with a length of about 102 times or more than the diameter, the longest diameter of the aggregate is Ot25# or less, and the diameter is 0.10 to 0.
A rubber characterized in that 5 to 90 parts by weight of carbon fibrils having a content of 25 mm aggregates of 50% or more are mixed into 100 parts by weight of a rubber component made of natural rubber, synthetic rubber, or a combination thereof. The present invention relates to a composition.

On the other hand, the present inventors conducted intensive research to develop a new TBR tread material and found that if the same specific carbon fibrils as mentioned above were blended into rubber, the hardness and lowering of the rubber could be improved with a small amount. We discovered that the effect of increasing the stress in rubber during stretching is remarkable. As a result of repeated studies, we surprisingly found that when a part of the commonly used highly reinforcing carbon black is replaced with carbon fibrils, the degree of identification is 172 to 1/4 that of carbon black. It was also discovered that the hardness and low tensile stress of the rubber can be maintained.

Therefore, the present inventors conducted research to apply this study result industrially, and as a result, the present inventors identified a method of the present invention in which a portion of the carbon black to be blended into rubber whose main component is natural rubber is reduced to a smaller amount. By substituting carbon fibrils, compared to the rubber obtained from a formulation without substitution, it maintains the same hardness and low tensile stress, has excellent breaking strength, tear properties, and abrasion resistance, and has a low specific gravity and It was confirmed that vulcanized rubber with low heat generation could be obtained, and the present invention was completed.

That is, the present invention relates to an aggregate formed by entwining carbon fibrils having a diameter of about 35 to 70 nm and a length of about 102 times or more than the diameter, and the longest diameter of the aggregate is 0.5 nm. 25ffi#I or less, and the diameter is 0.
10Ira~0. The content of aggregates that is 25 m is 50
% or more of carbon fibrils and carbon black based on natural rubber, preferably at least 50%.
For the rubber 100 weight part containing % by weight of natural rubber,
1 to 30 parts by weight of carbon fibrils, preferably 5 to 25 parts by weight
The invention also relates to a rubber composition characterized in that it contains 5 to 60 parts by weight, preferably 10 to 45 parts by weight, of carbon black.

Furthermore, we conducted intensive research to develop a new material for oil seals, and found that 1 to 30 parts by weight, preferably 5 to 20 parts by weight, of the same specific carbon fibrils as above were mixed with 100 parts by weight of oil-resistant rubber. It has been found that a rubber composition characterized by the following characteristics has low frictional resistance on the rubber surface without impairing mechanical strength.

The above-mentioned oil-resistant rubbers include rubbers that do not swell when in contact with lubricating oil, such as fluororubber, acrylic rubber, hydrin rubber, silicone rubber, acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-acrylic acid 1
Examples include stell rubber, chlorosulfonated polyethylene, chloroprene rubber, and preferred examples include fluororubber, acrylic rubber, and NBR.

[Function] The carbon fibrils used in the present invention have the following properties, as described in, for example, Japanese Patent Publication No. Sho 62-500943 d3 and U.S. Patent No. 4,663.230.
Suitable metal-containing particles (e.g., iron-, cobalt-, or nickel-containing particles supported on alumina) and a suitable gaseous carbon-containing compound (e.g., carbon monoxide) are heated at a temperature of about 850°C to 1
Contacting at a temperature in the range of 200° C. under a suitable pressure (e.g. 0.1 to 10 atmospheres) for a suitable time (e.g. 10 seconds to 180 minutes), the dry weight ratio of carbon-containing compound to metal-containing particles is at least about 100. : Obtained by the manufacturing method (vapor phase method).

The carbon fibrils obtained by the above manufacturing method have a diameter of approximately 3
．． 5 to 70 nm, preferably 3.5 to 40 nm, and the length is about 1×10 2 times or more the diameter. The carbon fibrils of the present invention preferably have an outer region consisting of a substantially continuous multilayer of regularly arranged carbon atoms and a hollow or less regular arrangement of carbon atoms in the outer region. The fibril is an essentially cylindrical heptad fibril having an inner core region containing carbon atoms, with each layer and core disposed substantially concentrically about the fibril's cylindrical axis.

Further, the regularly arranged carbon atoms in the outer region are graphitic, and the inner core region has a diameter of about 2 nll.
More preferably, it is larger than l.

Furthermore, the interplanar spacing of the carbon fibrils of the present invention measured by wide-angle X-ray diffraction is 3.38 to 3.50, and the diffraction angle trace is 25.5 to 2.
6.3 deg is preferable.

The carbon fibrils of the present invention specified above are described in Japanese Patent Publication No. 1983-500943 and U.S. Patent No. 4,
No. 663,230, the contents of which are incorporated herein by reference.

The carbon fibrils of the present invention are entangled to form an aggregate, and must have a specific diameter. On the one hand, in order to make the vulcanized rubber highly hard and maintain sufficient breaking strength, on the other hand, in order to make the vulcanized rubber highly hard and maintain sufficient breaking strength, on the other hand, a portion of the carbon black that should be blended into the vulcanized rubber was replaced with a smaller amount of carbon neubril. In order not to reduce the hardness and low tensile stress of the vulcanized rubber, it is essential that the carbon fibrils of the present invention exist as entangled aggregates. In order to prevent the aggregate from becoming easily untangled, the carbon fibrils must be as thin and long as possible, and the shape of the carbon fibrils according to the present invention fully satisfies this condition. In addition, carbon fibrils are
Those whose surface has been previously treated with ozone, nitric acid, heptamer, etc. can also be suitably used.

The dimensions of the aggregates contained in the carbon fibrils obtained by the above-mentioned production method are irregular, and the carbon fibrils contain a considerable amount of aggregates with a diameter of 0.25 mm or more. The longest diameter of aggregates in carbon fibrils is 0.25s or less, and the diameter is 010#~
To obtain carbon fibrils with a content of 0.25 m aggregates of 50% or more, use a vibrating ball mill, for example, and place steel balls with a diameter of 12.8 mm in an 800 cc stainless steel container with 5009 and untreated carbon fibrils. 5 fibrils
This can be achieved by adding 0.09 and processing at 1720 ppm for 35 minutes. This processing method is only an example and is not limited thereto.

In an aggregate of carbon fibrils, the diameter is 0.25 m.
If more than m is present, carbon fibrils in the rubber will be poorly dispersed in the final kneading process for producing a rubber composition, resulting in a decrease in the fracture strength of the vulcanized rubber. The aggregate of carbon fibrils has a diameter of 0.1 to 0. 25
If the content within the range of m is less than 50%, the hardness of the vulcanized rubber cannot be high, it is not possible to maintain a low tensile stress level, and the fracture strength is also high. l].

When obtaining a high hardness rubber composition, the amount of carbon fibrils mixed with 100 parts by weight of the rubber component is 5 to 90 parts by weight, but if it is less than 5 parts by weight, the hardness, breaking strength, and abrasion resistance of the vulcanized rubber sex does not improve. If the amount exceeds 90 parts by weight, it will be difficult to incorporate the carbon fibrils into the rubber, leading to poor dispersion, and the breaking strength of the vulcanized rubber will drop significantly.

In the rubber composition used to obtain the new TBR1 to Red material, the amount of carbon fibrils mixed in is 1 to 30 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the rubber component. If the mixing amount is less than 1 part by weight, no substantial mixing effect will be exhibited. Furthermore, if the amount exceeds 30 parts by weight, the hardness and low elongation stress will increase too much, and the elongation at break will decrease, resulting in a decrease in the strength at break.

Carbon black is not particularly limited, but preferably has a particle size of 401n! J or less, and the amount of iodine adsorption is 60q
/g or more, and DBP absorption 1 is 0.95cc/g or more.
Use highly reinforcing carbon black with a strength of at least g. It can also be used in combination with other carbon blacks and/or other carbon fibrils as required.

The amount of carbon black mixed into 100 parts by weight of the rubber component is 5 to 60 parts by weight, preferably 10 to 45 parts by weight. If the amount incorporated is less than 5 parts by weight, no substantial effect will be observed, and the necessary levels of hardness and low tensile stress cannot be maintained. Furthermore, if the amount exceeds 60 parts by weight, the stretch crystallinity of the natural rubber that is the base rubber is significantly impaired, resulting in a decrease in high tensile stress and breaking strength.

Although the rubber components used to obtain the high hardness rubber composition are not particularly limited, natural rubber is optimal as the base rubber used in the rubber composition suitable as the new TBR l-red material. When a blend of natural rubber and synthetic rubber is used as the base rubber, as the amount of synthetic rubber increases, the elongation crystallinity of the vulcanized rubber decreases, resulting in a decrease in high elongation resistance and breaking strength.

For oil seals, the amount of carbon fibrils of the present invention mixed with 100 parts by weight of the rubber component is 1 to 30 parts by weight, preferably 5 to 20 parts by weight; less than 1 part by weight may not provide sufficient frictional resistance improvement effect. If the amount exceeds 30 parts by weight, the viscosity tends to increase and processability tends to deteriorate.

Synthetic rubbers used in the present invention include emulsion polymerized styrene butadiene rubber, solution polymerized styrene butadiene rubber, polybutadiene rubber, polyisoprene rubber, ethylene propylene rubber, acrylonitrile butadiene, butyl rubber, polychloroprene rubber, acrylic rubber, fluororubber,
Chlorinated polyethylene, chlorosulfonated polyethylene,
Examples include shrimp chlorohydrin rubber and silicone rubber. These synthetic rubbers can also be used in combination with natural rubber in natural rubber-based rubber compositions for TBRI-Red materials.

In the composition of the present invention, vulcanizing agents, vulcanization accelerators, vulcanization accelerators, antiaging agents, softeners and fillers commonly used in the rubber industry are appropriately blended. These compounds are kneaded using a commonly used kneading machine such as a roll machine or a Banbury mixer, and then molded and vulcanized under normal vulcanized rubber production conditions.

Note that the carbon fibrils and rubber of the present invention can also be mixed by a wet masterbatch method.

[Example] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the Examples.

The diameter of carbon fibril aggregates was measured as follows.

After gluing the sample onto double-sided tape and coating the surface with gold coat, observe 12 fields of view at 50x magnification using a Hitachi model 3-510 SEM. And the area occupied by each aggregate was measured. Diameter 0.10~0.
The content of 25 m aggregates was determined by the following formula, and the average value of three sheets was used.

Area occupied by total aggregates Examples ■, ■ and comparative examples, ■ The following formulation: Formula JSR 111502 Carbon fibril zinc oxide 1) Stearic acid 2) Vulcanization accelerator Noxela-D3) Noxela DH4) Sulfur 5) 1) Manufactured by Sakai Chemical Industry No. 1 JIS K14102) Flower stone (manufactured by Pun JIS K33413) Manufactured by Ouchi Shinko Diphenylguanidine 4) Dibenzothiadyl disulfide 5) Karuizawa Smelting and Refining Labo Plastomill and roll according to powdered sulfur After kneading, the mixture was vulcanized at 145° C. for 30 minutes to obtain a rubber sheet with a thickness of about 2#. JIS. A test was conducted according to the tensile test method for vulcanized rubber specified in K6301, and the data on hardness (Hs) and breaking strength (TB) shown in Table 1 were obtained.

As seen in Example ①, the carbon fibrils related to the present invention were mixed in a small amount of 40 parts by weight, and the hardness (Hs) was 8.
A high hardness of 0 is obtained, and the breaking strength TB is also 290 K9
It is close to the highest level for SBR 111502 in flc&. On the other hand, as seen in the comparative example, the longest diameter of the aggregates was 0. If more than 25 m is contained, l-1 s tends to increase, but TB decreases markedly.

By comparing Example (2) and Comparative Example (2), it was found that the diameter was o. i
It is clear that when a large amount of aggregates below os is contained, HS remains at a normal level and TB decreases.

Example (1) and Comparative Examples (2) to (V) Table 2 shows examples in which the effects of the present invention were confirmed using more rubber physical property evaluation items. The formulation was as shown in Table 2, and the kneading and molding and vulcanization methods were the same as in Table 1.

As shown in Table 2, the test method was conducted in accordance with JIS and ASTM standards. Further, roll processability, which is not specified in the standards, was determined by winding the unvulcanized rubber compound around a 10-inch roll machine and observing its behavior.

Comparing Example ■ and Comparative Example V, we found that 11s (Comparative Example ■), a vulcanized rubber containing 90 parts by weight of commonly used carbon black (N 330), and a vulcanized rubber containing 45 parts by weight of carbon fibrils. The Hs (Example ■) of both rubbers showed high hardness of 90. From this,
It can be seen that the carbon fibrils of the present invention cannot produce a vulcanized rubber with sufficiently high hardness even when mixed with half the amount of carbon black. Furthermore, when comparing the physical properties of the two, the examples of the present invention have higher TB and abrasion resistance, and the amount of carbon fibrils added as a filler is only half that of carbon black, so the vulcanized rubber has sufficient elasticity. Yes, this is tan6
This can also be determined from the low value at 25°C. This also indicates that it has low heat generation. In addition, when high hardness is required as mentioned above, if carbon fibrils are used, the amount of sulfur blended at the normal level is sufficient, so it has better heat resistance than vulcanized rubber with a conventional blend that contains a large amount of sulfur. It is clear that it has an advantage in terms of deterioration resistance.

Comparative Example (3) shows a case where the amount of carbon fibrils blended is small, and l-1s, TB and abrasion resistance are significantly reduced.

Comparative Example (3) is an example in which a large amount of carbon fibrils was blended.

Although high hardness can be obtained, it is expected that workability is poor, TB and wear resistance are low, tan625° C. value is large, and heat generation is large.

Examples ■, ■ and Comparative Examples ■, ■ Table 3 EPDH (Nippon Gosei Com @ JSR E
P21) and fluororubber (Japan Synthetic Rubber JSR Afras 150P), carbon fibrils of the present invention and commonly used carbon black (N-330 or N-99)
The comparison with 0) was made smaller.

Example ILV has higher hardness and higher tensile strength than Comparative Examples (1) and VI, respectively.

Tables Examples ① to ① and Comparative Examples ① to XI Tables 4 and 5 are examples in which the effects of the present invention for obtaining novel TBR tread materials and sidewall materials were confirmed. The blending recipe was as shown in Tables 4 and 5, and the kneading method was the same as in Table 2. As the highly aromatic oil, Fucol AROHAXl3 manufactured by Fuji Kosan was used, and as the carbon black N220, Asahi #80 manufactured by Asahi Carbon was used.

The test method was performed as shown in Table 2. DIN-abrasion was carried out according to DIN-53516. All other compounded chemicals were the same as in Table 2.

Comparing Example ■ and Comparative Example ■, we found that compared to Comparative Example ■, in which 50 parts of the commonly used carbon black (N 220) were mixed, 2 parts of carbon black (N 220) were added.
Example 2, in which 5 parts by weight of the carbon fibrils according to the present invention was reduced by 0 parts by weight, had the same hardness (Hs), improved breaking strength (TB.-i) and wear resistance, and lower It can be seen that heat generation (small tan δ) and low specific gravity can be obtained.

Comparative Example IX shows a case where the carbon fibrils are small, and it can be seen that sufficient effects are not exhibited in fracture properties (TB.TR), wear resistance, and low heat generation properties.

Comparative example X shows a case where there are many carbon fibrils,
It can be seen that the hardness has increased significantly and the TB has decreased.

Example ■ and Comparative Example XI in Table 5 are natural rubber (NR
) with polybutadiene rubber (BR) NR/B R =
It shows the effect of adding the carbon fibrils when the ratio is 70/30, and Example Vl has better fracture properties and better fracture properties than Comparative Example XI.
It can be seen that the wear resistance and heat generation properties are improved, and the specific gravity is lower.

Table *I N-Cyclohexyl-2-benzot
hiazyl-sulfenamide (intrahuman emerging NO.
CCELEII CZ) *2 Using DIN abrasion tester manufactured by Toyo Seiki, index with Example ■ as 100 *3 Using RDS7700 manufactured by Rheometwax Far East FM,
Measured at i5t+z* Comparative Example XI is Example ■100
Examples ■ to XI and comparative examples XI to Xv Examples The formulation shown in Table 6 was kneaded using a 6-inch roll.

Carbon fibril A used in Examples (1) to (XI) had a diameter of 30 nm and a length of 30 μs as observed by electron microscopy, and the diameter and content of carbon fibril aggregates were as follows.

Aggregate diameter 0.11 ~ 0.25mm 75% by weight 0
11~0.10mm 25% by weight Vulcanization is 170℃ x 10 minutes press vulcanization, then 200℃ x 4
Oven vulcanization was performed for an hour.

Table 5 shows the measurement results of physical properties.

Comparative example χN is carbon fibril (B) diameter 0.2
The material was kneaded and molded in the same manner as in Example 2, except that a material containing 10 weight percent of aggregates of 6 to 0.50 mm was used. Tensile strength and elongation are inferior to Examples.

Comparative Examples ■ to Xv use graphite (Comparative Example ■) and molybdenum disulfide (
COMPARATIVE EXAMPLE

Kneading, molding and vulcanization were carried out in the same manner as in Examples (1) to (X). The results are shown in Table 7.

Comparative Examples (1) to (Xv) are all inferior in tensile strength and elongation compared to the Examples.

[Effect of the invention 1 As described above, the rubber composition of the present invention has high hardness, excellent fracture properties, abrasion resistance, and heat deterioration resistance,
Vulcanized rubber with low heat build-up can be provided.

By effectively utilizing these characteristics, it is possible to easily obtain rubber parts or rubber products that have excellent properties that have not been previously available.

Examples include treads, sidewalls and bead fillers for large and passenger tires, electrical wires, hoses,
There are weather strips, packings, sealing materials, high hardness rubber rolls, glass runs for passenger cars, rubber soles for shoes, various high hardness bells, high hardness anti-vibration rubber, etc., but the present invention is not limited to these specific examples. isn't it.

Furthermore, by substituting a part of the carbon black contained in a rubber composition mainly composed of natural rubber with the specific carbon fibrils of the present invention, it can withstand the harsh operating conditions of high loads and high speed running of TBR treads. A rubber composition that can withstand carbon black satisfactorily is obtained.
With a blending amount of , it is possible to further improve properties such as breaking strength, tear properties, and abrasion resistance while maintaining the same rubber hardness and low tensile stress.

Claims (3)

[Claims] (1) An aggregate formed by entwining carbon fibrils with a diameter of about 3.5 to 70 nm and a length of about 10^2 or more times the diameter, and the longest diameter of the aggregate is 0. 2
8 mm or less and a diameter of 0.10 to 0.25 mm
Carbon fibrils 5 in which the content of aggregates is 50% or more
A rubber composition containing ~90 parts by weight and 100 parts by weight of natural rubber and/or synthetic rubber. (2) An aggregate formed by intertwining carbon fibrils with a diameter of about 3.5 to 70 nm and a length of about 10^2 or more times the diameter, and the longest diameter of the aggregate is 0. 2
5 mm or less, and the diameter is 0.10 mm to 0.25
Rubber 10 containing 1 to 30 parts by weight of carbon fibrils with a content of 50% or more of mm aggregates, 5 to 60 parts by weight of carbon black, and at least 50% by weight of natural rubber.
A rubber composition containing 0 parts by weight. (3) An aggregate formed by intertwining carbon fibrils with a diameter of about 3.5 to 70 nm and a length of about 10^2 or more times the diameter, and the longest diameter of the aggregate is 0.5 nm to 70 nm. 2
5 mm or less, and the diameter is 0.10 mm to 0.25
A rubber composition for an oil seal, comprising 1 to 30 parts by weight of carbon fibrils having a content of 50% or more of aggregates of mm, and 100 parts by weight of oil-resistant rubber.