JP2010184991A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition having excellent on-ice performance and to provide a pneumatic tire obtained by using the rubber composition. <P>SOLUTION: The rubber composition is obtained by mixing 100 parts wt. of a diene-based rubber component with 0.3 to 20 parts wt. of granules that are composed of a fossil of a shellfish. The pneumatic tire includes a tread composed of the rubber composition. A vegetative granular body such as granules of a walnut shell and granules of vegetative porous carbonized product such as granules of bamboo charcoal may be used together with the granules of the fossil of the shellfish. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more specifically, as an example, a rubber composition that can be suitably used for a tread of a winter tire (winter tire) such as a studless tire or a snow tire, and the rubber composition The present invention relates to a pneumatic tire used.

  On snowy and snowy roads, the friction coefficient is significantly lower than that on ordinary roads, making it easier to slip. Therefore, in rubber compositions used for winter tire treads such as studless tires, the use of butadiene rubber with a low glass transition point or blending of a softening agent at low temperatures in order to improve the ground contact on the road surface on ice. The rubber hardness is kept low. In order to increase the frictional force on ice, foamed rubber is used for the tread, or hard materials such as hollow granular materials, glass fibers, and vegetable granular materials are blended.

  For example, in Patent Document 1 below, particles having a scratching effect such as plant granules obtained by pulverizing seed shells or fruit nuclei are added to a rubber component, and the friction performance on ice is improved by the scratching effect. Is disclosed. In particular, in this document, the plant granule is surface-treated with a rubber adhesion improver mainly composed of a mixture of resorcin / formalin resin initial condensate and latex, thereby chemically bonding to the tread rubber and scratching effect. The point which improves is proposed.

  In Patent Document 2 below, in order to effectively remove a water film on ice, a fly pon obtained by supporting a unit layer of fine laminated plate-like crystals of aluminosilicate metal salt fly pontoite around silica particles. It has been proposed to incorporate a tight-silica composite into a rubber component. Patent Document 3 below proposes blending bamboo charcoal with a rubber component in order to more effectively remove the water film on ice.

  In addition, in order to improve braking performance on snowy and snowy roads, shell powder (the following Patent Document 4), powder obtained by firing the shell (Patent Document 5), coral fossil, It has also been proposed to blend coral sand powder (Patent Document 6 below).

  Although these prior arts show the effect of improving the performance on ice, it cannot be said that they have reached a sufficient level to meet the increasingly demanding market demands recently.

  In addition, the following Patent Document 7 discloses that unfired scallop shell powder is blended with diene rubber, but it is not related to winter tires such as studless tires, but also uses crushed shell fossil. Not disclosed.

JP-A-10-007841 JP 2001-123017 A JP 2005-162865 A Japanese Utility Model Publication No. 06-57704 Japanese Patent Laid-Open No. 11-323024 JP-A-11-130915 JP 2004-196944 A

  This invention is made | formed in view of the above point, and it aims at providing the rubber composition which can exhibit the performance on ice better than before, and a pneumatic tire.

  In view of the above problems, the present inventors have formulated various substances in a rubber composition, and while intensively studying them, found that the performance on ice is remarkably improved by blending a crushed product of shell fossil, The present invention has been completed.

  That is, the rubber composition according to the present invention is obtained by blending 0.3 to 20 parts by weight of a crushed shell fossil with respect to 100 parts by weight of a diene rubber. Moreover, the pneumatic tire according to the present invention includes a tread made of such a rubber composition.

  According to the present invention, the performance on ice can be remarkably improved while suppressing a decrease in wear resistance.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  Examples of the diene rubber used as the rubber component in the rubber composition of the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and styrene-isoprene. Examples include various diene rubbers that are usually used in rubber compositions for tire treads such as polymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. These diene rubbers can be used alone or in a blend of two or more.

  As the rubber component, a blend of natural rubber and another diene rubber is preferably used, and a blend rubber of natural rubber (NR) and butadiene rubber (BR) is particularly preferably used. In that case, if the ratio of BR is too small, it is difficult to obtain low temperature characteristics of the rubber composition. Conversely, if the ratio is too large, the processability tends to deteriorate and the tear resistance tends to decrease, so the ratio of NR / BR is The weight ratio is preferably about 30/70 to 80/20, more preferably about 40/60 to 70/30.

  The rubber composition of the present invention contains a crushed fossil shellfish. Shell fossils consist of shells that lived in the ocean tens of millions of years ago, deposited in thick layers, and raised and fossilized by subsequent crustal movements. Shell fossil has a porous structure, and as a contained component, calcium is a main component and contains minerals such as phosphorus, potassium, and magnesium. Commercially available shell fossils take advantage of their porous structure, calcium-containing components, and weak alkalinity (pH 9 to 10) for applications such as fertilizers and soil conditioners currently required for agricultural crops. It's being used. The present invention uses a powder obtained by pulverizing such a fossil shellfish in a rubber composition, and provides a novel use of the fossil shellfish.

  The reason why the performance on ice can be greatly improved by the present invention is not necessarily clear, but the water film on the road surface on ice is effectively absorbed and removed by the porous structure peculiar to shell fossils, and its active ingredients (calcium, phosphorus This is presumed to be due to some interaction between the tread and the road surface. In addition, if it is a crushed shell fossil, it can be expected to have a scratching effect on the road surface on ice, which is presumed to contribute to the improvement of the performance on ice. In addition, as mentioned above, Patent Documents 4 to 7 include blending a shell powder, a shell fired powder, a coral fossil or coral sand powder, and an unfired scallop shell powder into the rubber composition. However, these are different from the crushed fossil shells, and the excellent effects on ice and wear resistance by combining the crushed fossil shell shells were found for the first time by the present invention. Is.

  The average particle size of the crushed fossil shellfish is not particularly limited, but for example, it is preferably 0.1 to 500 μm from the viewpoint of wear resistance and cut resistance, more preferably 0.5 to 100 μm, and further Preferably it is 0.5-50 micrometers. As a crushed product of shell fossil, it is possible to use a product classified after pulverization, but it is not always necessary to use a product whose particle size distribution is narrowed by classification, and a product with a wide particle size distribution that is not classified after pulverization is used as it is. Also good. In the present invention, the average particle diameter is a value measured by a laser diffraction / scattering method. In the following examples, a laser diffraction particle size distribution measurement manufactured by Shimadzu Corporation using a red semiconductor laser (wavelength 680 nm) as a light source is used. The measurement was performed using an apparatus “SALD-2200”.

  The crushed shell fossil can be blended within a range of 0.3 to 20 parts by weight with respect to 100 parts by weight of the diene rubber. When the blending amount is less than 0.3 parts by weight, the effect of addition is insufficient, and when it exceeds 20 parts by weight, the wear resistance is deteriorated. The blending amount is more preferably 1 to 15 parts by weight.

  The rubber composition of the present invention is further blended with a pulverized product of shell fossils, a plant granule obtained by pulverizing a seed shell or a fruit core, and / or a pulverized product of a porous carbide of a plant. May be. The performance on ice can be further improved by using these plant granules and porous carbide pulverized material in combination.

  As the plant granular material, a pulverized product obtained by pulverizing seed husks such as walnuts and persimmons or fruit nuclei such as peaches and plums by a known method can be used. Since these have a Mohs hardness of about 2 to 5 and are harder than ice, they can exhibit a scratching effect on the road surface on ice.

  In order to improve the familiarity with rubber and prevent dropping, it is preferable to use a plant granule that has been surface-treated with a rubber adhesion improver. As the rubber adhesion improver, for example, those having a mixture of resorcin / formalin resin initial condensate and latex as main components (RFL solution) can be mentioned.

  Although the average particle diameter of a vegetable granular material is not specifically limited, In order to exhibit the scratch effect and to prevent the fall off from a tread, it is preferable that it is 100-600 micrometers. The average particle diameter is a value measured by the laser diffraction / scattering method, as described above.

  The pulverized product of the porous carbide is obtained by pulverizing a porous material composed of a solid product mainly composed of carbon obtained by carbonizing a plant such as wood or bamboo. Since the pulverized product (bamboo charcoal powder) exhibits excellent adsorptivity due to its unique porosity, the water film generated on the road surface on ice can be effectively absorbed and removed.

  Bamboo materials that are used as raw materials for bamboo charcoal include various kinds of bamboo such as 孟 mune bamboo, maitake, pale bamboo, and crested bamboo, as well as bamboo such as chidori and Sendai. The bamboo charcoal pulverized product can be obtained by pulverizing bamboo charcoal obtained by steaming and baking bamboo material using a kiln into a powder using a known pulverizer (for example, a ball mill).

  Although the average particle diameter of the pulverized product of the porous carbide is not particularly limited, it is preferably 10 to 500 μm. The average particle diameter is a value measured by the laser diffraction / scattering method, as described above.

  When blending the pulverized product of these plant granules and porous carbide, the blending amount of both is preferably 0.3 to 20 parts by weight with respect to 100 parts by weight of the diene rubber. More preferably, it is 1 to 10 parts by weight.

  The rubber composition of the present invention comprises, in addition to the above-mentioned components, reinforcing agents and fillers such as carbon black and silica, process oil, zinc white, stearic acid, softener, and plasticizer that are used in ordinary rubber industry. , Anti-aging agent (amine-ketone, aromatic secondary amine, phenol, imidazole, etc.), vulcanizing agent, vulcanization accelerator (guanidine, thiazole, sulfenamide, thiuram, etc.), etc. These compounding chemicals can be appropriately blended within a normal range.

Here, as carbon black, when used in a tread portion of a studless tire, nitrogen adsorption specific surface area (N ₂ SA) (JIS K6217) is considered from the viewpoint of low temperature performance, abrasion resistance, rubber reinforcement, and the like of the rubber composition. -2) is 70 to 150 m ² / g and DBP oil absorption (JIS K6217-4) is preferably 100 to 150 ml / 100 g. Specifically, SAF, ISAF, and HAF grade carbon black are exemplified, and the blending amount is preferably in the range of about 10 to 80 parts by weight with respect to 100 parts by weight of the diene rubber.

  In addition, when silica is used, wet silica, dry silica, surface-treated silica or the like is used, and the blending amount is 50 with respect to 100 parts by weight of diene rubber from the viewpoint of balance of tan δ of rubber, reinforcing property, and electrical conductivity. The amount is preferably less than parts by weight, and is preferably about 10 to 120 parts by weight in total with carbon black. Moreover, when mix | blending a silica, it is preferable to use a silane coupling agent together.

  The rubber composition of the present invention can be prepared by kneading using a commonly used mixer such as a Banbury mixer or a kneader. The rubber composition is suitably used as a rubber composition for a tread portion of a winter tire (winter tire) such as a studless tire or a snow tire.

  The pneumatic tire of the present invention is manufactured by producing a tread portion of a tire using a rubber extruder or the like and molding an unvulcanized tire using the rubber composition, followed by a vulcanization process according to a conventional method. Can do. When applied to a studless tire having a cap base structure, the rubber composition of the present invention may be applied only to the cap tread on the ground contact surface side.

  The pneumatic tire of the present invention thus obtained has an effective water film on the road surface on ice due to its peculiar porous structure, etc., because the crushed shell fossil blended in the tread rubber is exposed on the tread surface. It is possible to improve the performance on ice by increasing the coefficient of friction between the tread rubber and the road surface. In addition, it is possible to suppress a decrease in wear resistance. Further, the use of vegetable granules such as pulverized walnut shells and porous carbide pulverized products such as bamboo charcoal pulverized products can further improve the performance on ice. In addition, the use of natural materials without causing road damage or asphalt dust does not adversely affect health and the environment even if crushed shell fossils are scattered.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, a tread rubber composition for studless tires was prepared according to the formulation shown in Table 1 below. Each component in Table 1 is as follows.

・ Natural rubber: RSS # 3,
・ Butadiene rubber: High butadiene rubber “BR01” manufactured by JSR Corporation,
Carbon black: “Seast KH” (N339, HAF) manufactured by Tokai Carbon Co., Ltd.
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
Silane coupling agent: “Si75” manufactured by Degussa
Paraffin oil: “JOMO Process P200” manufactured by Japan Energy Corporation.

-Shell fossil pulverized product: “Toyo Queen” (average particle size = 1.5 μm) manufactured by Toyo Shoji Co., Ltd.
-Bamboo charcoal pulverized material: Bamboo charcoal powder (average particle size 100 μm) obtained by crushing bamboo charcoal from Somune bamboo (“No. 1 charcoal” manufactured by Miyazaki Dogo Co., Ltd.) with a hammer mill and classifying the obtained pulverized material with a sieve.
・ Plant granules: crushed walnut shell ("Soft Grip # 46" manufactured by Japan Walnut Co., Ltd.) subjected to surface treatment with an RFL treatment solution according to the method described in JP-A-10-7841 (The average particle size of the plant granules after treatment is 300 μm),
・ Frypontite-silica composite: “Mizukanite HP” manufactured by Mizusawa Chemical Co., Ltd.
-Shell pulverized product: Hokkaido scallop shell pulverized product, strip-shaped (average particle size = 10 μm).

  In each rubber composition, 2 parts by weight of stearic acid ("Lunac S-20" manufactured by Kao Corporation) and zinc white ("Zinc Flower" manufactured by Mitsui Mining & Smelting Co., Ltd.) are used as a common compound. 1 type)) 2 parts by weight, anti-aging agent (“Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.) 2 parts by weight, wax (“OZOACE0355” manufactured by Nippon Seiki Co., Ltd.) 2 parts by weight, vulcanization accelerator (Sumitomo Chemical Co., Ltd.) 1.5 parts by weight of company "Soccinol CZ") and 2.1 parts by weight of sulfur ("powder sulfur" manufactured by Tsurumi Chemical Co., Ltd.) were blended.

  About each obtained rubber composition, hardness (23 degreeC) was measured. Also, studless tires were prepared using each rubber composition, and the wear resistance and braking performance on the road surface on ice (on-ice braking performance) were evaluated. The tire size was 185 / 65R14, and each rubber composition was applied to the tread and vulcanized and molded according to a conventional method. Each rim used was 14 × 5.5 JJ. Each measurement / evaluation method is as follows.

Hardness: Based on JIS K6253, the hardness at 23 ° C. of a sample vulcanized at 160 ° C. for 20 minutes (thickness of 12 mm or more) was measured using a type A durometer.

・ Abrasion resistance: The above tire was mounted on a 2000 cc 4WD vehicle, rotated left and right every 2500 km, and the remaining grooves after running 10,000 km (average value of remaining grooves of four tires) were measured. The value was expressed as an index with a value of 100. A larger index indicates better wear resistance.

・ Ice braking performance: The above tire is mounted on a 2000 cc 4WD vehicle, and the braking distance is measured by running ABS from 40 km / h on an ice board at -3 ± 3 ° C (average value of n = 10). Displayed as an index with the value of Example 2 as 100. The larger the index, the shorter the braking distance and the better the braking performance.

  The results are as shown in Table 1, and in Examples 1 and 2 in which a shell fossil pulverized product was blended, conventional materials (bamboo charcoal pulverized product, plant granule, fly pontoite-silica composite, shell crushed product) ), The braking performance on ice was greatly improved without substantially degrading the wear resistance. In particular, even in comparison with the fly-pontite-silica composite of Comparative Example 4 and the crushed shell of Comparative Example 5 that are common in the form of inorganic particles, it is remarkable in terms of both on-ice braking performance and wear resistance. The improvement effect was seen.

  Moreover, Example 3 which used a shell fossil pulverized material and a vegetable granule together, Example 4 which used a shell fossil pulverized material and a bamboo charcoal pulverized material together, and three of a shell fossil pulverized material, a bamboo charcoal pulverized material, and a vegetable granule. In Example 5 in which the persons were combined, a further improvement effect of the braking performance on ice was obtained.

  In Comparative Example 6 where the blending amount of the crushed shell fossil is too small, the effect of improving the braking performance on ice is insufficient, and in Comparative Example 7 where the blending amount is too large, the wear resistance is greatly deteriorated. It was.

  The rubber composition according to the present invention is required to have anti-slip properties such as shoe soles, mats, floor materials, and the like, including various pneumatic tires such as winter tires such as studless tires and snow tires, and tires for industrial vehicles. Can be widely used for rubber products.

Claims (3)

  A rubber composition comprising 0.3 to 20 parts by weight of a crushed shell fossil with respect to 100 parts by weight of a diene rubber.   The rubber composition according to claim 1, further comprising a vegetable granule obtained by pulverizing seed shells or fruit nuclei and / or a pulverized product of a porous carbon of a plant.   A pneumatic tire provided with a tread comprising the rubber composition according to claim 1.