JP2010285536A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a rubber composition having the excellent on-ice performance; and a pneumatic tire formed using this rubber composition. <P>SOLUTION: This rubber composition comprises 100 pts.wt. of a diene-based rubber and 0.3-20 pts.wt. of a porous hydroxyapatite powder. This pneumatic tire is provided with a tread formed with the rubber composition. The powder uses a natural hydroxyapatite powder obtained from domestic-animal bones or the like, and may combine a plant granular material such as a pulverized product of walnut shell or a plant granular material whose surface is surface-treated with a resin liquid of a rubber adhesion improver. <P>COPYRIGHT: (C)2011,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 such as a studless tire or a snow tire, and an air using the rubber composition This relates to the tires inside.

  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 addition, the average particle diameter of the vegetable granular material specifically used as an Example here is 125 micrometers or more.

  Patent Document 2 below proposes blending a rubber component with a pulverized product such as bamboo charcoal having an average particle diameter of 10 to 500 μm in order to more effectively remove a water film on ice. Patent Document 3 below describes that the braking performance on ice is improved by adding a specific zeolite such as Y-type together with the above-mentioned plant granules.

  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.

  On the other hand, Patent Document 4 described below uses a natural hydroxyapatite porous body derived from natural bone as a bone filler or the like. Patent Document 5 below describes a method for efficiently producing natural hydroxyapatite from livestock bones such as cow bones, and is used to prevent food spoilage, maintain freshness, purify waste water, air, etc. It is said that it can be used.

  Natural hydroxyapatite is a kind of calcium phosphate compound based on hydroxyapatite (also referred to as “hydroxyapatite”), and is also called natural apatite for short. Natural hydroxyapatite is a multifunctional bioceramic having ion exchange properties, adsorptivity, catalytic functionality, and the like. Moreover, since it has antibacterial properties, it is used in food and medical fields as food preservatives and antibacterial materials. In addition, as a supplement for phosphoric acid components and calcium components, or as a neutralizing agent (“alkali material”) for neutralizing acidic components, nutrient enhancers (“supplements”), food additives, feed additives, soil improvers Etc. are used. In recent years, as a cosmetic material, it is used as a base for powdered products such as foundations. Furthermore, since it has excellent biocompatibility and bone affinity, it is also used for artificial tooth roots and the like. However, compounding with resin or rubber is not generally performed.

JP-A-10-007841 JP 2005-162865 A JP 2003-041058 A JP-A-5-208044 Japanese Patent No. 2534499

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a rubber composition and a pneumatic tire that can exhibit even better performance on ice.

  In view of the above problems, the present inventor has found that the performance on ice is remarkably improved by compounding porous hydroxyapatite powder while compounding various substances in the rubber composition and intensively studying them. The present invention has been completed.

  That is, the rubber composition according to the present invention is obtained by blending 0.3 to 30 parts by weight of porous hydroxyapatite powder with respect to 100 parts by weight of the 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.

In the rubber composition of the present invention, porous hydroxyapatite powder is blended. Hydroxyapatite is generally represented by a composition formula of Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ (the number of atoms of each crystal unit), has a Mohs hardness of 5, and is a white crystal when pure. The porous hydroxyapatite is preferably natural hydroxyapatite obtained through various treatments for removing other components from domestic bone or fish bone. The open porosity (apparent porosity) of natural hydroxyapatite is, for example, about 30%. Natural hydroxyapatite powder can be obtained, for example, by the method described in Patent Document 4 above. Specifically, the bones of cattle, horses, sheep and other livestock, mainly bones, are boiled in a pressure cooker at 200-400 ° C to remove gelatin, fat, protein, glue, etc. And can be obtained by firing at 900 to 1100 ° C. and pulverization. Natural hydroxyapatite powder is made by steaming grilled domestic bones or fish bones into bone char, then crushing them, adding an acid such as sodium hydroxide to the dissolved and extracted ingredients. It can also be obtained by precipitation (for example, JP-A-09-054456). That is, bone ash used as a ceramic raw material can be used. Porous hydroxyapatite can also be obtained by chemical synthesis using phosphoric acid or phosphate and calcium salts as raw materials, and even such hydroxyapatite is based on the equivalent open porosity. If they have an adsorption action, they can be used equally. The porous hydroxyapatite may contain a small amount of inorganic impurity components and unremoved carbon components. In some cases, the porous hydroxyapatite is a porous fine powder made of a calcium phosphate material other than hydroxyapatite. Even if it has appropriate adsorption property and hardness, it is also possible to use it.

  The average particle diameter of the porous hydroxyapatite powder is preferably 0.1 to 500 μm from the viewpoint of wear resistance and cut resistance, more preferably 0.5 to 50 μm, and still more preferably 0.5 to 15 μm. More preferably, the thickness is 0.5 to 5 μm, and particularly preferably 0.5 to 2 μm. That is, a particle having a particularly small average particle size is most preferable, and if the average particle size is larger than this range, the effect on improving the performance on ice is not sufficient. On the other hand, if the average particle diameter is smaller than this range, problems such as difficulty in production by pulverization and inferior handling properties during kneading may occur. 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. Measurement was performed by a dry method using an apparatus “SALD-2200”.

  The reason why the performance on ice can be greatly improved by the present invention is not necessarily clear. In particular, it is difficult to find a reasonable reason for the fact that a particularly small average particle size is most preferable. Probably, due to the unique porous structure and adsorptivity of porous hydroxyapatite such as natural hydroxyapatite, the water film on the road surface on ice is effectively absorbed and dehydrated, and based on its ion exchange action, etc. This is presumed to be due to some interaction with the. In addition, since the porous hydroxyapatite powder has high hardness, it exhibits a scratching effect on the road surface on ice, which is also presumed to contribute to the improvement of the performance on ice. In addition, when a particle having a particularly small average particle diameter is used, it is considered that there is actually a very small amount even if there is an effect of damaging the road surface.

  The porous hydroxyapatite powder 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.

  In addition to the porous hydroxyapatite powder, the rubber composition of the present invention further comprises a plant granule obtained by pulverizing seed shells or fruit nuclei and / or a pulverized product of plant porous carbide. 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, the plant-based granule is preferably used after being surface-treated with a resin solution of a rubber adhesion improving agent. 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 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 the tread portion of a studless tire, nitrogen adsorption specific surface area (N ₂ SA) (JIS K6217) is considered from the viewpoints of low temperature performance, abrasion resistance, rubber reinforcement, and the like of the rubber composition. -2) is 70 to 150 m ² / g, and the 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 30 to 80 parts by weight in the total amount 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 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 due to its unique porous structure, etc., because the porous hydroxyapatite powder 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. Moreover, the use of natural materials without causing road damage or asphalt dust does not adversely affect health and the environment even if the porous hydroxyapatite powder is 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.

・ Natural hydroxyapatite powder: “Natural apatite 1 micron” and “Natural apatite 325 mesh” (average particle size of about 3 microns) by EXELA Corporation
-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.
・ Surface-treated plant granular material: A walnut shell pulverized product (“Soft Grit # 46” manufactured by Nippon Walnut Co., Ltd.) is subjected to surface treatment with an RFL treatment liquid according to the method described in JP-A-10-7841. (The average particle diameter of the treated plant granules is 300 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 195 / 65R15, and each rubber composition was applied to the tread and manufactured by vulcanization molding according to a conventional method. Each rim used was 15 × 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.

  A result is as showing in Table 1, and it is Examples 1-4 which mix | blended the natural hydroxyapatite powder with respect to the comparative examples 2-4 which mix | blended the conventional material (bamboo charcoal ground material, vegetable granule). The braking performance on ice was greatly improved without substantially deteriorating the wear resistance. In particular, the braking performance on ice was greatly improved as compared with Comparative Example 2 using bamboo charcoal, which is also porous and is considered to be more adsorbable. Moreover, compared with the comparative example 3 which mix | blended only the weight part of vegetable granular material (walnut powder), the braking performance on ice was able to be improved significantly similarly.

  Example 1 and Example 2 differ only in the average particle size of the natural hydroxyapatite powder, but in the case of Example 1 where the average particle size is 1 μm, compared to Example 2 where the average particle size is 3 μm. Thus, both wear resistance and braking performance on ice were significantly superior. On the other hand, in Example 2, the difference in effect between Comparative Example 2 was not so clear. In order to improve the braking performance on ice, it was a completely unexpected result that a particularly excellent performance was obtained with a fine particle size that is not usually added. The reason for this is unclear, but the active surface may have more contact with the rubber material, which may have affected the micro structure and rubber properties.

  On the other hand, as known from the comparison between Example 2 and Example 4, compared to the case where only the natural hydroxyapatite powder is added for imparting the braking performance on ice, the braking on ice is carried out when the plant granular material is also blended. The performance was significantly improved. In Example 4 in which the plant granule was used in combination, when only the braking performance on ice was seen, it was higher than Example 1 and the wear resistance was not so lowered. This is presumed to suggest that the scratching effect of the natural hydroxyapatite powder is smaller than the scratching effect of the plant granules.

  In Example 3, the amount of natural hydroxyapatite powder was considerably large, although the braking performance on ice was further improved compared to Example 1 in which the amount of natural hydroxyapatite powder was a typical amount with the same average particle diameter. Abrasion was slightly inferior.

  On the other hand, compared to Example 4 in which natural hydroxyapatite powder and plant granules were added, Example 5 with bamboo charcoal was used, but although the braking performance on ice was slightly improved, the wear resistance was relatively lowered. It was big. This is a result supporting the speculation that natural hydroxyapatite powder contributes to the braking performance on ice mainly due to water absorption, similar to bamboo charcoal.

  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 30 parts by weight of a porous hydroxyapatite powder with respect to 100 parts by weight of a diene rubber.   The rubber composition according to claim 1, further comprising a plant granule obtained by pulverizing a seed shell or a fruit core, or a product obtained by treating the surface with a resin solution of a rubber adhesion improver.   A pneumatic tire provided with a tread comprising the rubber composition according to claim 1.