JP5272411B2 - Diene rubber composition - Google Patents

Description

  The present invention relates to a diene rubber composition. More specifically, the present invention relates to a diene rubber composition that is suitably used as a vulcanization molding material for a studless cap tread portion of a pneumatic tire.

  Studless pneumatic tires are formulated by combining various compounding agents in order to improve the performance on ice, but in general, deterioration of heat generation and wear resistance cannot be avoided by blending the compounding agents.

For studless pneumatic tires, the surface roughness (based on JIS B0601) is determined from a rubber composition containing 3 to 150 parts by weight of carbonaceous fine powder (surface chemical modification) with an average particle size of 0.5 to 200 μm per 100 parts by weight of rubber. A tread with excellent anti-slip properties with a centerline average roughness Ra) of 2 μm or more is formed, and pneumatic tires with such treads are anti-slip without losing the excellent elasticity and durability of rubber materials. Therefore, it is said that it can be suitably used as a studless tire since the friction coefficient on ice and snow is remarkably improved. Moreover, what finely pulverized the bituminous coal is mentioned as an example as a carbonaceous fine powder used here.
Japanese Patent Laid-Open No. 4-117439

Similarly, in a pneumatic tire, a carbonaceous fine powder having an average particle size of 0.5 to 500 μm is used to improve the friction property on ice of a foamed rubber tread tire without impairing the handling stability on icy and normal road surfaces. There has also been proposed a pneumatic tire in which the body contains 3 to 100 parts by weight per 100 parts by weight of rubber and the foamed rubber having closed cells with a foaming rate of 3 to 35% is arranged on the tread, and has a cap base structure. In the foamed rubber disposed in the cap portion of the tread portion, a finely pulverized bituminous coal is exemplified as the carbonaceous fine powder.
JP-A-4-368206

In addition, various proposals have been made for blending a bituminous coal pulverized product in a diene rubber composition for forming a tread portion of a pneumatic tire, and for a solid tire, for example, a bituminous coal pulverized product is 1/20 to 20/1. Of carbon black (nitrogen adsorption specific surface area of 50 to 200 m ² / g, DBP oil absorption of 50 to 130 ml / 100 g, CTAB adsorption specific surface area of 50 to 170 m ² / g are preferred, for example, HAF, ISAF, A diene rubber composition using a combination of channel black such as SAF, furnace black, acetylene black, and thermal black) has been proposed.
JP 2007-161196 A

  However, when the cap tread portion for studless is formed from a bituminous coal pulverized material or a combination of this and carbon black in a diene rubber composition, the on-ice performance required for a studless pneumatic tire is required. Neither heat generation nor wear resistance can be satisfied.

  The object of the present invention is to provide performance on ice, heat generation when used as a vulcanization molding material for studless cap tread parts of pneumatic tires in a diene rubber composition blended in combination with a bituminous coal pulverized product and carbon black. It is to provide a material that can satisfy both the properties and the wear resistance.

  The object of the present invention is that, based on 100 parts by weight of the diene rubber, 5-30 parts by weight of a bituminous coal pulverized product, 1-10 parts by weight of diatomaceous earth, and 40-60 parts by weight of carbon black having an iodine adsorption of 80-140 g / kg. This is achieved by a diene rubber composition containing

The vulcanized product obtained by vulcanizing and molding the diene rubber composition according to the present invention has excellent on-ice performance such as braking on ice, excellent heat generation and wear resistance indicating low heat generation , that is, on ice. Since heat generation and wear resistance can be balanced without degrading performance, the diene rubber composition of the present invention should be used effectively as a vulcanization molding material for cap treads for studless caps of pneumatic tires. Can do.

  Diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), styrene butadiene rubber (SBR), etc. Or as a blend rubber, preferably NR, BR, SBR or a blend rubber thereof. As SBR, either emulsion polymerization SBR (E-SBR) or solution polymerization SBR (S-SBR) can be used.

  The bituminous coal or non-caking coal bituminous coal pulverized material is a type of coal called bituminous coal (B1, B2, C in the JIS M1002 coal classification) with average particle size (ASTM D1511 Compliant; measured with an average measuring device Microtrac SRA 150) About 0.01 to 100 μm, preferably about 0.05 to 50 μm, with a specific gravity of 1.6 or less, preferably 1.35 or less. By setting the average particle size within this range, the rolling resistance of the pneumatic tire can be sufficiently reduced, and by reducing the specific gravity, the fuel consumption of the vehicle equipped with the pneumatic tire can be sufficiently reduced. Can do.

  The bituminous coal pulverized product is used in a ratio of 5 to 30 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of the diene rubber. If the blending ratio of the bituminous coal pulverized product is less than this, any improvement in performance on ice, heat generation and wear resistance will not be achieved, and the effect of the bituminous coal pulverized product with particularly good thermal conductivity will not be exhibited. If it is used in a large proportion, the heat generation becomes large and the heat generation is not satisfied.

Diatomaceous earth is a soft rock or soil mainly composed of diatom shell, which is a unicellular organism. Pure diatomaceous earth has a chemical composition of approximately 94% SiO _{2 and} 6% H ₂ O, but natural diatomaceous earth is generally an impurity. Is included. The diatomaceous earth used in the present invention is a cylindrical or columnar porous body, the height (100 μm or less, preferably 1 to 30 μm) is L, and the L / D when the bottom diameter is D is L / D 0.2 to 3.0, preferably 0.3 to 2.0 are used. Specifically, it is a kind called Melosira Granulate Curbata, which has a uniform porous and unique honeycomb structure, and its typical chemical composition is SiO ₂ 89.2%, Al ₂ O ₃ 4.0%, Fe ₂ O ₃ 1.5%, CaO 0.5%, MgO 0.3%. Actually, unlike the flat diatomaceous earth generally used for horticultural applications, for example, a special cylindrical or columnar diatomaceous earth belonging to the genus genus, such diatomaceous earth is well known and marketed. Therefore, in the present invention, such a commercial product can be used.

  Diatomaceous earth is used in a ratio of 1 to 10 parts by weight, preferably 3 to 8 parts by weight, based on 100 parts by weight of the diene rubber. When the blending ratio of diatomaceous earth is less than this, the performance on ice is reduced as compared with the case of no blending. On the other hand, when the blending ratio is larger than this, the heat generation and wear resistance are deteriorated.

  Carbon black has an iodine adsorption amount (based on JIS K6217) of 80 to 140 g / kg, preferably 80 to 100 g / kg, and 40 to 60 parts by weight, preferably 45 parts per 100 parts by weight of diene rubber. Used in a blending ratio of ~ 55 parts by weight.

  Carbon black having such iodine adsorption amount includes S-212 (ISAF-LS-SC; 117 g / kg), N-219 (ISAF-LS; 118 g / kg), N-220 (ISAF-HM; 121 g / kg). ), N-231 (ISAF-LM; 125 g / kg), N-234 (118 g / kg), N-242 (ISAF-HS; 123 g / kg), S-315 (HAF-LS-SC; 86 g / kg) ), N-326 (HAF-LS; 82 g / kg), N-330 (HAF; 82 g / kg), N-339 (92 g / kg), N-347 (HAF-HS; 90 g / kg), N- 356 (HAF-VHS; 90 g / kg), N-358 (HAF-VHS; 84 g / kg), etc. are used. When carbon black having an iodine adsorption amount less than this is used, the wear resistance is particularly deteriorated. On the other hand, when carbon black having an iodine adsorption amount exceeding this is used, the exothermic property is deteriorated.

  These carbon blacks are used in a ratio of 40 to 60 parts by weight, preferably 45 to 55 parts by weight, per 100 parts by weight of the diene rubber. When the blending ratio of carbon black is less than this, the performance on ice and the wear resistance are inferior. On the other hand, when the blending ratio is larger than this, the heat generation becomes high and the heat generation is impaired.

  In the diene rubber composition containing the above components as essential components, a compounding agent generally used as a compounding agent for rubber, for example, a vulcanizing agent such as sulfur depending on the type of diene rubber, thiazole , Sulfenamide, guanidine, thiuram and other vulcanization accelerators, silica, talc, clay, graphite, calcium silicate and other reinforcing agents or fillers, stearic acid, paraffin wax, aroma oil and other processing aids Zinc oxide, an anti-aging agent, a plasticizer and the like are appropriately blended and used as necessary.

The compounding of silica having a reinforcing action is particularly preferable, and silica having a BET specific surface area of 30 to 200 m ² / g, preferably 50 to 150 m ² / g is generally used. These include the pyrolysis method of halogenated silicic acid or organosilicon compounds and the dry method of silica and sodium silicate pyrolysis method, which is produced by heating and reducing silica sand and air-oxidizing the evaporated SiO. Wet process silica to be produced, etc., and wet process silica is preferably used in terms of cost and performance. Actually, a commercial product marketed for the rubber industry can be used as it is. The blending ratio is 25 parts by weight or less, preferably 10 to 20 parts by weight per 100 parts by weight of the diene rubber, and low rolling resistance and wet resistance performance are sufficiently exhibited by the blending of silica. If it is used at a blending ratio higher than this, the processability deteriorates.

Thus, the properties required of silica and dispersibility with diene rubbers (silica has poor affinity with rubber polymers, and silica in rubber forms hydrogen bonds through silanol groups, and silica is incorporated into rubber. In order to increase (having the property of reducing dispersibility), a silane coupling agent is used in a proportion of 2 to 15% by weight, preferably 5 to 10% by weight, based on the weight of silica. The silane coupling agents, polysulfide silane coupling agent having a sulfur chain which reacts with the alkoxysilyl group and the polymer capable of reacting with silanol groups of the silica surface, such as bis (3-triethoxysilylpropyl) tetrasulfide, bis (2 -Triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide and the like are preferably used. If the proportion of silane coupling agent used is less than this, the properties required of silica and dispersibility with diene rubber will not be fully exhibited. On the other hand, if it is used in a proportion higher than this, processability will deteriorate. To come.

  The composition was prepared by kneading by a general method using a kneader such as a kneader, a Banbury mixer, and an open roll, and the obtained composition was a diene rubber, a vulcanizing agent, Vulcanization is carried out at a vulcanization temperature corresponding to the type of vulcanization accelerator and the blending ratio thereof to form a cap tread portion located above the base tread portion (appertain red portion). Such a cap tread portion forms a studless cap tread portion of a pneumatic tire.

  Next, the present invention will be described with reference to examples.

Standard example Natural rubber (SIR-20) 60.0 parts by weight Polybutadiene rubber (Nippon ZEON product Nipol BR 1220) 40.0 〃
Carbon Black-I (Cabot Japan Product Show Black N339; 50.0 〃
Iodine adsorption 92 [g / kg], DBP absorption 121 [ml / 100g]) [CB-I]
Silica (Degussa product Ultrasil VN3GR) 15.0 〃
Diatomaceous earth (Celaton LOS-3, product of Eagle-Picher Filtration & Minerals) 5.0 〃
Bituminous coal pulverized product (Coin Fillers Incorporated product Austin Black 325; −
(Average particle size 5.50μm, specific gravity 1.31 ± 0.03)
Zinc Hana (Zinc Oxide Product Zinc Oxide 3 types) 5.0 〃
Coupling agent (Degussa product Si69) 1.5 〃
Sulfur (Tsurumi Chemical Co., Ltd., Jinhua Indian Oil Fine Powdered Sulfur) 1.5 〃
Vulcanization accelerator (Ouchi Emerging Chemical Industry Noxeller CZ-G) 1.5 〃

  Among the above components, the components other than the vulcanization accelerator and sulfur were kneaded with a 3 L closed mixer for 5 minutes and released when the temperature reached 150 ° C. to obtain a master batch. A vulcanization accelerator and sulfur were added to this master batch and kneaded with an open roll to obtain a diene rubber composition.

The obtained diene rubber composition was vulcanized at 150 ° C. for 30 minutes to obtain a predetermined vulcanized rubber test piece. The obtained vulcanized rubber test piece was measured for the following items.
Inside test on ice: A vulcanized sheet was affixed to a flat cylindrical base rubber, and using an inside drum type on-ice friction tester, measuring temperatures -3.0 ° C and -1.5 ° C, load 0.54 MPa (5.5 kg / cm ² ), drum The friction on ice was measured at a rotational speed of 25 km / hr, and the value obtained in the standard example was shown as an index of 100 (the larger the value indicating the performance on ice, the better the braking on ice)
Exothermic property: Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, tanδ at 60 ° C was measured under the conditions of initial strain 10%, amplitude ± 2%, frequency 20Hz, and the value obtained in the standard example was set to 100 Expressed as an index (the higher this value indicating exothermicity, the better, indicating lower heat generation)
Abrasion resistance: The amount of wear was measured in accordance with JIS K-6214 using a Lambourn Abrasion Tester, and the value obtained in the standard example was shown as an index of 100. It is excellent)

Examples 1-2 and Comparative Examples 1-8
In the standard examples, natural rubber, polybutadiene rubber, silica, zinc white, coupling agent, sulfur and vulcanization accelerator were used in the same amount, and the amounts of carbon black, diatomaceous earth and bituminous coal pulverized products (parts by weight) are shown in Table 1, respectively. It was changed and used as follows. Carbon black-II [CB-II] is Mitsubishi Chemical product Diablack E (FEF; iodine adsorption amount 45 g / kg, DBP absorption amount 115 [ml / 100 g]).
Table 1
Example CB-I CB-II Diatomaceous earth bituminous coal ground material Example 1 50.0 5.0 10.0
〃 2 50.0 5.0 20.0
Comparative Example 1 50.0 5.0 20.0
〃 2 50.0 20.0 5.0
３ 3 30.0 5.0 20.0
４ 4 70.0 5.0 20.0
５ 5 50.0 0.5 20.0
６ 6 50.0 15.0 20.0
７ 7 50.0 5.0 3.0
８ 8 50.0 5.0 40.0

The results obtained in the above standard example, Examples 1-2 and Comparative Examples 1-8 are shown in the following Table 2.
Table 2
Example: Performance on ice Performance heat resistance Wear resistance standard example
Example 1 100 105 103
〃 2 100 110 108
Comparative Example 1 105 160 70
〃 2 105 95 105
３ 3 95 110 90
４ 4 105 90 110
５ 5 95 102 105
６ 6 110 95 95
７ 7 100 100 100
８ 8 105 95 105

From the above results, the following can be said.
(1) Examples 1 and 2 that satisfy the requirements of the present invention satisfy all of the performance on ice, heat generation, and wear resistance.
(2) When carbon black showing an iodine adsorption amount outside the specified range is used (Comparative Example 1), carbon black showing an iodine adsorption amount within the specified range is used, but the blending ratio is small (comparison) Example 3) When the blending ratio of diatomaceous earth is too large (Comparative Example 6), it becomes inferior in wear resistance.
(3) When not using a bituminous coal pulverized product and also using carbon black exhibiting an iodine adsorption amount outside the specified range (Comparative Example 2), carbon black exhibiting an iodine adsorption amount within the specified range is used. When the blending ratio is too high (Comparative Example 4), when the blending ratio of diatomaceous earth is too large (Comparative Example 6), or when the blending ratio of bituminous coal is too large (Comparative Example 8), it is satisfied in terms of heat generation. Disappear.
(4) When the blending ratio of diatomaceous earth is small (Comparative Example 5), the performance on ice becomes inferior.
(5) When the blending ratio of bituminous coal is small (Comparative Example 7), any improvement in performance on ice, heat generation and wear resistance is not achieved.

Claims (6)

  Diene system consisting of 5 to 30 parts by weight of bituminous coal pulverized product, 1 to 10 parts by weight of diatomaceous earth, and 40 to 60 parts by weight of carbon black having an iodine adsorption of 80 to 140 g / kg to 100 parts by weight of diene rubber Rubber composition.   The diene rubber composition according to claim 1, wherein the diatomaceous earth is a cylindrical or columnar porous body.   The diene rubber composition according to claim 2, wherein a porous body having a L / D of 0.2 to 3.0 is used, where L is the height of the cylindrical body or columnar body and D is the diameter of the bottom surface.   The diene rubber composition according to claim 1, further comprising 25 parts by weight or less of silica.   The diene rubber composition according to claim 1, 2, 3, or 4, which is used as a vulcanization molding material for a studless cap tread portion of a pneumatic tire.   A pneumatic tire having a studless cap tread portion vulcanized and molded from the diene rubber composition according to claim 5.