JP6327000B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same, and more specifically, a rubber composition capable of simultaneously improving all of heat generation, hardness, bending fatigue resistance, and workability, and the same. It relates to pneumatic tires.

  2. Description of the Related Art Conventionally, as a run flat tire that enables running in a puncture state, a side reinforcing type run flat tire in which a side reinforcing layer having a crescent cross section is disposed inside a sidewall portion has been proposed (for example, see Patent Document 1). ing.

In such side-reinforced run-flat tires, it is common to use a rubber composition having a high hardness for the side reinforcing layer in order to enhance durability during run-flat running.
On the other hand, during traveling at a low internal pressure, a large load is applied to the side reinforcing layer, and large deformation is repeated, whereby the side reinforcing layer generates heat. Since heat generation promotes deterioration of the rubber and may destroy the rubber, the side reinforcing layer is required to have low heat generation properties, high hardness, and high bending fatigue resistance.
In order to obtain low heat build-up, a method of reducing the blending amount of carbon black is common, but in this case, high hardness cannot be obtained.
In order to obtain high hardness, a method of increasing the compounding amount of carbon black is known. However, in this case, the exothermic property is deteriorated, and the viscosity of the unvulcanized rubber composition is increased, thereby kneading. There is a problem that the load on the process such as extrusion and extrusion is large, workability is deteriorated, and bending fatigue resistance is also deteriorated.
In order to improve the deterioration of workability due to the increase in the amount of carbon black, there is a means for increasing the amount of oil. In this case, both the hardness and the exothermicity are deteriorated.
As described above, it is recognized that it is a difficult matter in the art to obtain a rubber composition capable of simultaneously improving all of heat generation, hardness, bending fatigue resistance, and workability.

Japanese Patent Laid-Open No. 7-3030412

  Accordingly, an object of the present invention is to provide a rubber composition capable of simultaneously improving all of heat generation, hardness, bending fatigue resistance, and workability, and a pneumatic tire using the same.

The present inventors have results of extensive research with respect to the diene rubber having a specific composition, carbon black having a modified C ₉ petroleum resin and a specific characteristic in phenolic compounds with specific properties, vulcanization It has been found that the above problem can be solved by blending the accelerator and sulfur in a specific amount, and the present invention has been completed.
That is, the present invention is as follows.

1. The weight average molecular weight Mw is 200 to 1000 and the softening point is in the range of −40 to 20 ° C. with respect to 100 parts by mass of diene rubber including 10 to 40 parts by mass of natural rubber and 60 to 90 parts by mass of butadiene rubber. 1 to 30 parts by weight of a _{C 9} petroleum resin modified with phenolic compounds, nitrogen adsorption specific surface area _(N 2 SA) of 30 to 80 parts by weight of carbon black 5~90m ² / g, the vulcanization accelerator A rubber composition comprising 1.5 to 5.0 parts by mass and 3 to 10 parts by mass of sulfur.
2. Phenolic modified C ₉ petroleum resin compound, the rubber composition according to the 1, which is a modified C ₉ petroleum resin with phenol.
3. 3. The rubber composition as described in 1 or 2 above, wherein the rubber composition after vulcanization has a hardness (hardness measured at 20 ° C. in accordance with JIS K6253) of 70 or more.
4). A pneumatic tire in which the rubber composition according to any one of 1 to 3 is disposed as a side reinforcing rubber.

According to the present invention, to the diene-based rubber having a specific composition, carbon black having a modified C ₉ petroleum resin and a specific characteristic in phenolic compounds with specific properties, vulcanization accelerators and sulfur specific Since they are blended in amounts, it is possible to provide a rubber composition capable of simultaneously improving all of heat generation, hardness, bending fatigue resistance, and workability, and a pneumatic tire using the same.

  Hereinafter, the present invention will be described in more detail.

(Diene rubber)
The diene rubber used in the present invention contains natural rubber (NR) and butadiene rubber (BR) as essential components. From the viewpoint of the effect of the present invention, the blending amounts of NR and BR are preferably 10 to 40 parts by mass and 60 to 90 parts by mass of BR, and 20 to 40 parts by mass and BR 60 when the entire diene rubber is 100 parts by mass. -80 mass parts is more preferable. Diene rubbers other than NR and BR can also be used, and examples include isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), and acrylonitrile-butadiene copolymer rubber (NBR). . These may be used alone or in combination of two or more. The molecular weight and microstructure are not particularly limited, and may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized. As the diene rubber, it is preferable to use a non-hydrogenated rubber.

(Modified C ₉ petroleum resin with a phenol compound)
_{C 9} petroleum resins modified with phenolic compounds used in the present invention has a weight average molecular weight Mw of 200 to 1000, and a softening point in the range of -40~20 ℃. Also, the C ₉ petroleum resin is a liquid at room temperature.
As is well known, the C ₉ petroleum resin is an aromatic petroleum resin obtained by (co) polymerizing a C ₉ fraction obtained by thermal decomposition of naphtha. Typical C ₉ petroleum resin, styrene, vinyl toluene, and a-methyl styrene, indene, one or more selected from methyl indene and dicyclopentadiene as monomer units.
C ₉ petroleum resins modified with phenolic compounds used in the present invention can be obtained by cationic polymerization of the C ₉ fraction in the presence of phenolic compounds. Examples of the phenolic compound include phenol, cresol, xylenol, pt-butylphenol, p-octylphenol, p-nonylphenol, and the like. Among them, phenol is preferable from the viewpoint of improving the effect of the present invention.
Here, the weight average molecular weight Mw of C ₉ petroleum resins modified with phenolic compounds is greater than 200 less than or 1000, pyrogenic, hardness, it can not improve the bending fatigue resistance, workability at the same time. Even when the softening point is lower than −40 ° C. or higher than 20 ° C., the heat generation, hardness, bending fatigue resistance, and workability cannot be improved at the same time.
The weight average molecular weight is measured by a GPC method in terms of polystyrene, and the softening point is measured by a ring and ball method defined in JIS K6220-1.
Incidentally, _{C 9} petroleum resins modified with phenolic compounds used in the present invention may be used those commercially available, for example, Rutgers Co. Nobaresu L100, Nobaresu L800, Nobaresu A1200, etc. Nobaresu LC60 is cited It is done.
By blending the modified C ₉ petroleum resin with a phenol-based compound, the crosslinking reaction between the resin and the diene rubber is promoted, it is presumed that the desired properties are expressed. In addition, since the cross-linking chain length between the resin and the diene rubber is long, it is estimated that excellent bending fatigue resistance is exhibited.

(Carbon black)
The carbon black used in the present invention needs to have a nitrogen adsorption specific surface area (N ₂ SA) of 5 to 90 m ² / g in order to improve heat generation, hardness, bending fatigue resistance, and workability at the same time. From the viewpoint of further enhancing the effect, it is preferably 10 to 80 m ² / g.
The nitrogen adsorption specific surface area (N ₂ SA) is determined according to JIS K6217-2.

(Vulcanization accelerator)
As the vulcanization accelerator used in the present invention, any conventionally known vulcanization accelerator can be used. For example, thiuram vulcanization accelerator, sulfenamide vulcanization accelerator, guanidine vulcanization accelerator, thiazole Vulcanization accelerators, and the like.

(Rubber composition ratio)
The rubber composition of the present invention, to the diene rubber 100 parts by weight, the 30 parts by mass of phenol-modified _{C 9} petroleum resin compound, the nitrogen adsorption specific surface area _(N 2 SA) 5～90M ² 30 to 80 parts by mass of carbon black / g, 1.5 to 5.0 parts by mass of a vulcanization accelerator, and 3 to 10 parts by mass of sulfur.
If the amount of the C ₉ petroleum resins modified with the phenolic compound is less than 1 part by mass, it is impossible to achieve the effect of the present invention too small, amount. Conversely, when it exceeds 30 mass parts, exothermic property and hardness will deteriorate.
When the blending amount of the carbon black is less than 30 parts by mass, the hardness is deteriorated, and when it exceeds 80 parts by mass, the heat generation, the bending fatigue resistance and the workability are deteriorated.
When the blending amount of the vulcanization accelerator is less than 1.5 parts by mass, the heat buildup and hardness are lowered, and when it exceeds 5.0 parts by mass, the bending fatigue resistance is deteriorated.
When the amount of sulfur is less than 3 parts by mass, the heat buildup and hardness are reduced, and when it exceeds 10 parts by mass, the bending fatigue resistance is deteriorated.

A further preferred amount of the C ₉ petroleum resins modified with the phenolic compound to the diene rubber 100 parts by weight, from 5 to 30 parts by weight.
A more preferable blending amount of the carbon black is 40 to 70 parts by mass with respect to 100 parts by mass of the diene rubber.
A more preferable blending amount of the vulcanization accelerator is 2 to 5 parts by mass with respect to 100 parts by mass of the diene rubber.
The more preferable compounding amount of the sulfur is 3 to 8 parts by mass with respect to 100 parts by mass of the diene rubber.

(Other ingredients)
In the rubber composition of the present invention, in addition to the above-described components, a vulcanization or crosslinking agent; a vulcanization or crosslinking accelerator; various fillers such as zinc oxide, clay, talc, calcium carbonate; an anti-aging agent; Various additives that are generally blended in rubber compositions such as additives can be blended, and these additives are kneaded by a general method into a composition and used for vulcanization or crosslinking. Can do. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

  The rubber composition of the present invention is suitable for producing a pneumatic tire according to a conventional method for producing a pneumatic tire, and the hardness of the rubber composition after vulcanization (measured at 20 ° C. according to JIS K6253). The hardness is preferably 70 or more, and is preferably applied to the side reinforcing layer of the run-flat tire from the viewpoints of exothermic property, bending fatigue resistance, and workability.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Standard Example 1, Examples 1-3 and Comparative Examples 1-8
Sample Preparation In the formulation (parts by mass) shown in Table 1, the components except the vulcanization accelerator and sulfur were kneaded for 5 minutes with a 1.7 liter closed Banbury mixer, and then added with the vulcanization accelerator and sulfur. The rubber composition was obtained by kneading. Next, the obtained rubber composition was press vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and an unvulcanized rubber composition and vulcanized rubber were tested by the following test method. The physical properties of the test piece were measured.

Exothermic property (tan δ (60 ° C.)): In accordance with JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd., elongation deformation strain rate = 10%, amplitude = ± 2%, frequency = 20 Hz, temperature Tan δ (60 ° C.) was measured under the condition of 60 ° C., and the exothermic property was evaluated with this value. The results are shown as an index with the standard example 1 being 100. A larger index indicates a lower exothermic property.
Hardness: measured at 20 ° C. according to JIS K6253.
Bending fatigue resistance: A bending crack growth test was conducted in accordance with JIS K6260. A scratch having a length of 2 mm was previously made at the center of the test piece, a displacement amount of 26% was added, and 300 times of bending was applied per minute, and the number of times of bending until the wound reached a predetermined length was measured. The result was expressed as an index with the value obtained in Standard Example 1 as 100. The larger the index, the better the bending fatigue resistance.
Mooney viscosity: The viscosity of unvulcanized rubber at 100 ° C. was measured in accordance with JIS K6300 using the rubber composition. The results were expressed as an index with the value of standard example 1 being 100. The larger the index, the lower the viscosity and the better the workability.
The results are also shown in Table 1.

* 1: NR (STR20)
* 2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.)
* 3: Carbon Black-1 (Toast Carbon Co., Ltd. Seast F, nitrogen adsorption specific surface area (N ₂ SA) = 40 m ² / g)
* 4: Carbon black-2 (Niteron Carbon Co., Ltd. Niteron # 300IH, Nitrogen adsorption specific surface area (N ₂ SA) = 115 m ² / g)
* 5: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 6: Stearic acid (beef stearic acid manufactured by NOF Corporation)
* 7: Anti-aging agent (VULKANOX manufactured by LANXESS)
* 8: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu KK)
* 9: Resin -1 (Rutgers Co. Nobaresu L800, phenol modified with _{C 9} petroleum resin, Mw = 300, softening point -40 to-30 ° C., hydroxyl value = 0.1 wt%, liquid at room temperature)
* 10: Resin-2 (Novales C90 manufactured by Rutgers, Coumarone Indene resin, Mw = 2000, softening point 20-30 ° C., hydroxyl value = 0.0 wt%, solid at room temperature)
* 11: Sulfur (fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd. (sulfur content 95.24% by mass))
* 12: Vulcanization accelerator (SANTOCURE CBS manufactured by FLEXSYS)

As is clear from the results in Table 1 above, the rubber compositions obtained in Examples 1 to 3 were C ₉ modified with a phenolic compound having specific characteristics with respect to the diene rubber having a specific composition. Since a specific amount of a petroleum petroleum resin and carbon black having specific characteristics, a vulcanization accelerator, and sulfur are blended, the exothermic property, hardness, bending fatigue resistance, and workability compared to the conventional representative standard example 1 It has been found that all of can be improved at the same time.
In contrast, Comparative Example 1, without using the C ₉ petroleum resin modified with phenolic compounds, because in case of using unmodified coumarone-indene resin to that instead, pyrogenic, flexural fatigue resistance And processability deteriorated.
Comparative Example 2, since the amount of C ₉ petroleum resins modified with phenolic compound is less than the lower limit defined in the present invention, bending fatigue resistance and processability is deteriorated.
Comparative Example 3, since the amount of denatured C ₉ petroleum resin in the phenolic compounds is greater than the upper limit defined in the present invention, heating and hardness is deteriorated.
In Comparative Example 4, since the blending amount of carbon black was less than the lower limit specified in the present invention, the hardness deteriorated.
In Comparative Example 5, since the blending amount of carbon black exceeded the upper limit defined in the present invention, the heat generation property, the bending fatigue resistance, and the workability deteriorated.
In Comparative Example 6, since the nitrogen adsorption specific surface area (N ₂ SA) of carbon black exceeded the upper limit defined in the present invention, the heat generation property, the bending fatigue resistance, and the workability deteriorated.
In Comparative Example 7, since the blending amount of the vulcanization accelerator and sulfur was less than the lower limit specified in the present invention, the heat generation and hardness were deteriorated.
In Comparative Example 8, the bending fatigue resistance deteriorated because the blending amounts of the vulcanization accelerator and sulfur exceeded the upper limit defined in the present invention.

Claims (4)

The weight average molecular weight Mw is 200 to 1000 and the softening point is in the range of −40 to 20 ° C. with respect to 100 parts by mass of diene rubber including 10 to 40 parts by mass of natural rubber and 60 to 90 parts by mass of butadiene rubber. , phenol, cresol, xylenol, modified with p-t-butylphenol, p- octylphenol or p- nonylphenol, an aromatic petroleum resin obtained by polymerizing a C ₉ fraction obtained by thermal cracking of naphtha C ₉ 1 to 30 parts by mass of a petroleum petroleum resin, 30 to 80 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 5 to 90 m ² / g, and 1.5 to 5.0 parts by mass of a vulcanization accelerator And a rubber composition for a side reinforcing layer of a run-flat tire, comprising 3 to 10 parts by mass of sulfur. The C ₉ petroleum resin is, the side reinforcing layer rubber composition of the run-flat tire according to claim 1, characterized in that the modified C ₉ petroleum resin with phenol. The side reinforcement of a run flat tire according to claim 1 or 2, wherein the rubber composition after vulcanization has a hardness (hardness measured at 20 ° C in accordance with JIS K6253) of 70 or more. Layer rubber composition. A pneumatic tire which is a run-flat tire in which the rubber composition according to any one of claims 1 to 3 is disposed as a rubber for a side reinforcing layer .