JP4800188B2 - Rubber composition for bead apex and tire having bead apex using the same - Google Patents

Description

  The present invention relates to a rubber composition for bead apex and a tire having a bead apex using the same.

  A rubber composition used for a tire bead apex needs to have high hardness (E *), low tan δ, and excellent elongation at break (excellent driving stability, rolling resistance characteristics, and curb pinch cut performance). .

  In order to satisfy these requirements, a technique using a filler such as carbon black or silica, a phenol resin, or the like is known as a rubber composition for bead apex (see Patent Document 1). In order to satisfy high hardness, it is necessary to increase the amount of filler such as carbon black and silica, increase the amount of phenol resin, and refine the filler such as carbon black and silica. Become. However, in this case, tan δ increases and elongation at break also decreases, so there is still room for improvement.

JP 2003-72312 A

  The present invention provides a rubber composition for bead apex capable of improving steering stability, rolling resistance characteristics and curb pinch cut performance in a well-balanced manner, and a tire having a rubber composition for bead apex using the same. With the goal.

  The present invention relates to a bead apex containing 20 to 70 parts by weight of carbon black, 2 to 25 parts by weight of phenolic resin and / or modified phenolic resin, and 3 to 40 parts by weight of bituminous coal with respect to 100 parts by weight of the rubber component. The present invention relates to a rubber composition.

  The present invention also relates to a tire having a bead apex using the rubber composition for bead apex.

  According to the present invention, by containing a predetermined amount of rubber component, carbon black, phenolic resin and / or modified phenolic resin, and bituminous coal, it is possible to improve steering stability, rolling resistance characteristics, and curb pinch cut performance in a well-balanced manner. A bead apex rubber composition that can be used and a tire having a bead apex rubber composition using the same can be provided.

  The rubber composition for bead apex of the present invention contains a rubber component, carbon black, a phenol resin and / or a modified phenol resin, and bituminous coal.

  Examples of the rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), and chloroprene rubber (CR). ), Acrylonitrile butadiene rubber (NBR) and the like. These rubber components are not particularly limited, and may be used alone or in combination of two or more. Of these, NR and / or IR are preferred because of their excellent breaking performance.

  The carbon black or bituminous coal is entangled with the phenolic resin and / or modified phenolic resin to form a sphere in which the carbon black or bituminous coal is uniformly dispersed in the form of lotus root in the phenolic resin and / or modified phenolic resin particles. Further, the remaining carbon black or bituminous coal is taken into the formed sphere, the outer diameter of the sphere is increased, and sufficient hardness is obtained at the same time. In the present invention, it is possible to improve steering stability, rolling resistance characteristics, and curb pinch cut performance in a well-balanced manner by adjusting the blending amount of carbon black, phenol resin and / or modified phenol resin, and bituminous coal. If either carbon black or bituminous coal is not blended, there is a problem that the outer diameter of the sphere is not sufficient and sufficient hardness cannot be obtained.

  Carbon black has a dibutyl phthalate oil absorption (DBP) of preferably 70 ml / 100 g or more, and more preferably 80 ml / 100 g or more. When the DBP of carbon black is less than 70 ml / 100 g, the hardness tends to be small. Further, the DBP of carbon black is preferably 140 ml / 100 g or less, more preferably 130 ml / 100 g or less, and further preferably 120 ml / 100 g or less. When the DBP of carbon black exceeds 140 ml / 100 g, tan δ tends to increase.

  The compounding amount of carbon black is 20 parts by weight or more, preferably 40 parts by weight or more with respect to 100 parts by weight of the rubber component. When the blending amount of carbon black is less than 20 parts by weight, the viscosity is low, no torque is generated during kneading, the dispersion of phenol resin and / or modified phenol resin is deteriorated, and rolling resistance characteristics and curb pinch cut performance are deteriorated. To do. Moreover, the compounding quantity of carbon black is 70 weight part or less, Preferably it is 65 weight part or less. If the blending amount of carbon black exceeds 70 parts by weight, tan δ will increase.

  Although it does not necessarily restrict | limit as a phenol resin, For example, what is obtained by making phenols and aldehydes, such as formaldehyde, acetaldehyde, a furfural, react with an acid or an alkali catalyst, etc. are mention | raise | lifted.

  The modified phenolic resin is not particularly limited. For example, a phenolic resin modified with cashew oil, tall oil, linseed oil, various animal and vegetable oils, unsaturated fatty acid, rosin, alkylbenzene resin, aniline, melamine, etc. Etc.

  As the phenol resin or the modified phenol resin, a modified phenol resin is preferable and a cashew oil-modified phenol resin or a rosin-modified phenol resin is preferable because the hardness (Hs) can be improved and steering stability can be improved.

  The compounding amount of the phenol resin and / or the modified phenol resin is 5 parts by weight or more, preferably 7 parts by weight or more with respect to 100 parts by weight of the rubber component. When the blending amount of the phenol resin and / or the modified phenol resin is less than 5 parts by weight, sufficient hardness (Hs) cannot be obtained, and steering stability is deteriorated. Moreover, the compounding quantity of a phenol resin and / or a modified phenol resin is 25 weight part or less, Preferably it is 20 weight part or less, More preferably, it is 18 weight part or less. When the blending amount of the phenol resin and / or the modified phenol resin exceeds 25 parts by weight, the curb pinch cut performance is deteriorated.

  Bituminous coal includes coal in general. Examples of bituminous coal include caking coal and non-caking coal.

  The carbon content of the bituminous coal is preferably 60% by weight or more, more preferably 65% by weight or more, and further preferably 70% by weight or more. If the carbon content of the bituminous coal is less than 60% by weight, it tends to be difficult to handle because it contains a lot of moisture. The carbon content of the bituminous coal is preferably 90% by weight or less, and more preferably 80% by weight or less. If the carbon content of the bituminous coal exceeds 90% by weight, the cost tends to increase.

  The average primary particle size of the bituminous coal is preferably 0.1 μm or more, and more preferably 0.2 μm or more. If the average primary particle size of the bituminous coal is less than 0.1 μm, the cost tends to increase. The average primary particle size of bituminous coal is preferably 30 μm or less, and more preferably 25 μm or less. When the average primary particle size of the bituminous coal exceeds 30 μm, the reinforcing property tends to be lowered.

  The blending amount of bituminous coal is 3 parts by weight or more, preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component. When the amount of bituminous coal is less than 3 parts by weight, the effects of increasing hardness and reducing tan δ are small. The blending amount of bituminous coal is 40 parts by weight or less, preferably 35 parts by weight or less. When the blending amount of the bituminous coal exceeds 40 parts by weight, the content of the oil contained in the bituminous coal is excessively increased in the rubber composition, not only the dispersibility is lowered, but also sufficient hardness cannot be obtained.

  The rubber composition for bead apex of the present invention preferably further contains silica.

  Silica is not particularly limited, and those conventionally used in the rubber industry can be used.

  As for the compounding quantity of a silica, 5-10 weight part is preferable with respect to 100 weight part of rubber components. If the compounding amount of silica is less than 5 parts by weight, curb pinch cut performance tends to deteriorate, and if it exceeds 10 parts by weight, shrinkage during extrusion tends to be a problem.

  The total amount of carbon black, bituminous coal, and silica is preferably 50 parts by weight or more, more preferably 60 parts by weight or more with respect to 100 parts by weight of the rubber component. When the total amount of carbon black, bituminous coal and silica is less than 50 parts by weight, the hardness tends to be small. The total amount of carbon black, bituminous coal and silica is preferably 90 parts by weight or less, and more preferably 80 parts by weight or less. When the total blending amount of carbon black, bituminous coal and silica exceeds 90 parts by weight, tan δ is large and the fracture characteristics tend to deteriorate.

  When blending silica, it is preferable to blend a silane coupling agent with silica.

  The silane coupling agent is not particularly limited, and those conventionally used with silica can be used, and examples thereof include bis (3-triethoxysilylpropyl) tetrasulfide and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) ) Tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide Sulfide Bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4- Triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N -Dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilane Ruethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxy Sulfide series such as silylpropyl methacrylate monosulfide, mercapto series such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltriethoxysilane , Vinyl type such as vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-amino Amino) such as ethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycid Glycidoxy type such as xylpropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3 -Chloro series such as chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, and the like.

  The compounding amount of the silane coupling agent is preferably 6 parts by weight or more and more preferably 8 parts by weight or more with respect to 100 parts by weight of silica. When the amount of the silane coupling agent is less than 6 parts by weight, the silica tends to re-aggregate after kneading the rubber and tan δ tends to increase. The amount of the silane coupling agent is preferably 15 parts by weight or less, more preferably 12 parts by weight or less. When the compounding amount of the silane coupling agent exceeds 15 parts by weight, the surface area of the silica is not covered, but the silane coupling agent consumed for crosslinking between the rubbers increases, and the breaking characteristics tend to deteriorate.

  The rubber composition for bead apex of the present invention preferably further contains hexamethylenetetramine (HMT).

  The blending amount of HMT is preferably 0.5 parts by weight or more and more preferably 0.7 parts by weight or more with respect to 100 parts by weight of the rubber component. If the blending amount of HMT is less than 0.5 parts by weight, there is a tendency that the methylene groups present in the rubber composition are too few and the crosslinking of the phenol resin is insufficient. The amount of HMT is preferably 3.0 parts by weight or less, and more preferably 2.0 parts by weight or less. When the amount of HMT exceeds 3.0 parts by weight, ammonia released together with the methylene group tends to inhibit the adhesion between the adjacent case and the cord.

  In addition to the rubber component, carbon black, phenolic resin and / or modified phenolic resin, bituminous coal, silica and silane coupling agent, the rubber composition for bead apex of the present invention has been conventionally used in the rubber industry. Agents such as anti-aging agents, zinc oxide, stearic acid, tackifiers, vulcanization accelerators, sulfur, vulcanization accelerators and the like can be appropriately blended as necessary.

  The rubber composition for bead apex of the present invention is produced by a general method. In other words, the rubber composition for bead apex of the present invention can be produced by kneading the compounding agent with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing it.

  The rubber composition for a bead apex of the present invention can be suitably used as a bead apex among tire members because it can improve steering stability, rolling resistance characteristics and curb pinch cut performance in a well-balanced manner. is there.

  The tire of the present invention is produced by a usual method using the rubber composition for bead apex of the present invention. That is, if necessary, the rubber composition for bead apex of the present invention blended with the above compounding agent is extruded in accordance with the shape of the bead apex of the tire at an unvulcanized stage, and then on a tire molding machine. An unvulcanized tire is formed by molding by an ordinary method. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain the tire of the present invention.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Natural rubber (NR): RSS # 3
Carbon Black (1): Show Black N550 (DBP: 121 ml / 100 g) manufactured by Cabot Japan
Carbon Black (2): Show Black N660 (DBP: 90 ml / 100 g) manufactured by Cabot Japan
Bituminous coal: Austin black made of coal filler (carbon content: 77%, average primary particle size: 5 μm)
Silica: 115GR manufactured by Rhodia
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Modified phenolic resin: PR12686 (cashew oil-modified phenolic resin) manufactured by Sumitomo Bakelite Co., Ltd.
Hexamethylenetetramine (HMT): Noxeller H manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Zinc oxide: Mitsui Metal Mining Co., Ltd. Stearic acid: Nippon Oil & Fats Co., Ltd. Tackifier: Nippon Shokubai Co., Ltd. SP1068
Vulcanization accelerating aid: Takiroll V200 manufactured by Taoka Chemical Co., Ltd.
Insoluble sulfur: Kristex HSOT 20 (insoluble sulfur containing 80% by weight of sulfur and 20% by weight of oil) manufactured by Flexis
Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
N-cyclohexylthio-phthalamide (CTP): CTP manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(SEM observation)
A rubber composition containing carbon black, bituminous coal and modified phenolic resin was prepared and observed with a scanning electron microscope (SEM). As a result, it was found that the modified phenolic resin, carbon black and bituminous coal were taken in, and the carbon black and bituminous coal were uniformly dispersed in the modified phenolic resin particles in the form of lotus root.

Examples 1-6 and Comparative Examples 1-4
In accordance with the formulation shown in Table 1, using a Banbury mixer, a vulcanization acceleration aid, insoluble sulfur, a vulcanization accelerator and chemicals other than CTP were kneaded to obtain a kneaded product. Next, using an open roll, the obtained kneaded product was kneaded by adding a vulcanization acceleration aid, insoluble sulfur, a vulcanization accelerator, and CTP to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized for 12 minutes at 170 ° C. to prepare vulcanized rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 4.

(Viscoelasticity test)
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd., the complex elastic modulus E * (MPa) of the vulcanized rubber composition under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2%. ) And loss tangent tan δ were measured. Larger E * indicates higher rigidity and better steering stability, and smaller tan δ indicates lower rolling resistance and better resistance.

(Tensile test)
Using a No. 3 dumbbell-shaped test piece composed of the vulcanized rubber composition, a tensile test was conducted according to JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber—How to Obtain Tensile Properties”, and elongation at break EB (%) Was measured. It shows that it is excellent in curb pinch cut performance, so that EB is large.

  The evaluation results are shown in Table 1.

Claims (2)

For 100 parts by weight of rubber component,
20 to 70 parts by weight of carbon black,
2 to 25 parts by weight of phenolic resin and / or modified phenolic resin,
3-40 parts by weight of bituminous coal , and
Containing silica,
A rubber composition for bead apex, wherein the total amount of carbon black, bituminous coal and silica is 50 to 90 parts by weight . A tire having a bead apex using the rubber composition for bead apex according to claim 1.