JP2005162865A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition that effectively removes a water film on the frozen road surface, raises frictional force on ice, significantly improves ice performance and does not reduce various properties such as abrasion resistance, etc. <P>SOLUTION: The rubber composition is obtained by mixing 100 parts wt. of a diene-based rubber component with 1-20 parts wt. of granules that are composed of a porous carbonized product of plant and have 10-500 μm average particle diameter. The porous carbonized product is preferably bamboo charcoal. The rubber composition is further mixed with vegetative granules such as ground walnut husk. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition. More specifically, the present invention is excellent in anti-slip performance on icy and snowy road surfaces without deteriorating various properties such as wear resistance, and in particular, increases frictional force on icy road surfaces to increase braking and driving performance of tires. The present invention relates to a rubber composition suitable for a tread portion of a studless tire that improves the tire performance, and a pneumatic tire using the rubber composition for the tread portion.

  Studless tires with a tread block pattern are generally used for automobiles that run on snowy and snowy roads. The rubber composition used for this is improved in driving and braking performance on iced roads, Many studies have been made on rubber compositions that do not deteriorate various properties such as wearability, handling stability, and low rolling resistance.

  As a rubber composition that increases the frictional force on the road surface on ice, for example, a technology that maintains low rubber hardness at low temperatures by using a butadiene rubber having a low glass transition temperature or a softener and improves the ground contact property, filling A part of the carbon black of the agent is replaced with silica to maintain low modulus at low temperature and improve adhesive friction, foam rubber is used for the tread, hollow granular material, gas-filled resin etc. are blended in the tread grounding part Improves water removal effect and scratching effect by providing micro uneven parts on the surface, and blends hard granular materials such as organic polymer substances and inorganic substances, vegetable granules such as short fibers and walnut shells to obtain a scratching effect And many techniques which combined these are proposed (refer patent documents 1-3).

  However, the rubber compositions according to each of the above technologies have a problem that wear resistance and steering stability tend to decrease because the strength and block rigidity of the rubber composition are all decreased, and a large amount of silica is blended. In some cases, it is not sufficient to satisfy any of the methods, such as a decrease in the mixing property and a problem of conductivity, and a compound containing hollow particles has a problem in processability that the particles are destroyed during mixing. The actual situation is not.

Therefore, the present applicant has formulated a hydrophilic porous adsorbent such as flypontite-silica composite to further increase the frictional force on ice, and the innumerable micropores formed on the tread surface are road surfaces on ice. Adsorbs and removes the water film generated by contact pressure and frictional heat between the tread and the tread, and further improves the on-ice performance by increasing the on-ice frictional force by using in combination with the above plant granule combination. I proposed that earlier. (Patent Document 4).
JP-A-11-21381 JP 2000-158907 A JP-A-10-7841 JP 2001-123017 A

  However, the rubber composition blended with the above-mentioned fly-pontite-silica composite adsorbs the water film on the road surface on ice and exhibits good grounding properties, but the water film due to the water absorption and water removal effects of the rubber composition. The removal performance does not always reach a satisfactory level, and there is still room for improvement.

  The present invention effectively removes the water film on the surface of the ice due to the water absorption and dewatering action of the rubber composition to increase the frictional force on the ice, greatly improving the performance on ice, and reducing various properties such as wear resistance. It is an object of the present invention to provide a rubber composition that is not allowed to occur, and a pneumatic tire using the rubber composition in a tread portion.

  As a result of intensive studies on the removal of a water film generated between the road surface and the tread rubber on the road surface on ice with a small coefficient of friction, the present inventors have determined that the porous property comprising a solid product mainly composed of specific carbon. Paying attention to the adsorption performance of the substance, if a specific amount of the granular material is blended with the rubber composition, it will absorb water and remove water without reducing the wear resistance, effectively removing the water film on the ice surface. The inventors have found that the performance is improved and have completed the present invention.

  That is, the present invention is a rubber comprising 1 to 20 parts by weight of granules having an average particle size of 10 to 500 μm made of a plant porous carbide based on 100 parts by weight of a diene rubber component. It is a composition, and the porous carbide is preferably bamboo charcoal.

  The rubber composition of the present invention includes porous carbide granules that are easily and inexpensively obtained by carbonizing plants such as wood and bamboo, and are excellent in adsorptivity. The water film generated on the road surface on ice due to the porous property absorbs and removes water, effectively removing the water film that causes slippage between the road surface and the rubber composition to increase the frictional force, and the rubber composition on the ice. The performance can be significantly improved.

  The granular material preferably has an average particle size in the range of 10 to 500 μm, and if it is less than 10 μm, the water absorption and dehydration actions are insufficient, and if it exceeds 500 μm, the abrasion resistance starts to be adversely affected. Moreover, the compounding quantity to a rubber composition of a granular material is 1-20 weight part with respect to 100 weight part of rubber components, and if it is less than 1 weight part, water absorption and dehydration are inadequate, and 20 weight part is reduced. If it exceeds, the wear resistance tends to decrease.

  Furthermore, in the rubber composition of the present invention, it is preferable that a vegetable granule such as pulverized walnut shell is further blended. Thereby, in addition to the water film removal effect of a road surface, on-ice performance can be further improved by the synergistic effect by the scratch effect by a plant granular material.

  The pneumatic tire of the present invention is characterized in that the rubber composition is used in a tread portion, and a studless tire capable of improving on-ice performance without deteriorating tire characteristics such as wear resistance and steering stability. The granular material does not damage the road surface or generate asphalt dust, and even if the natural bamboo charcoal or plant granular material is scattered, it does not cause health problems or environmental pollution.

  According to the rubber composition of the present invention, the water film generated on the road surface on ice is absorbed and removed, and the water film causing the slip between the road surface and the tread rubber is effectively removed to greatly increase the frictional force. , Significantly improve the performance on ice. In addition, the pneumatic tire of the present invention is suitable for a studless tire that improves performance on ice without deteriorating tire characteristics such as wear resistance and steering stability.

  The rubber component used in the rubber composition of the present invention includes natural rubber (NR), various butadiene rubbers (BR), various styrene butadiene rubbers (SBR), and diene-based synthetic rubbers such as isoprene rubber (IR). These diene rubbers can be used singly or as a blend of two or more.

  In the present invention, when the rubber component is used in a blend, for example, in the case of using a blend of NR and BR for a tread of a studless tire, if the ratio of BR is too small, it becomes difficult to obtain the low temperature characteristics of the rubber composition. If the amount is too large, the workability tends to deteriorate and the tear resistance tends to decrease. Therefore, the ratio of NR / BR is about 30/70 to 80/20, more preferably about 40/60 to 70/30. preferable.

  The plant porous carbide used in the present invention is a porous substance composed of a solid product mainly composed of carbon obtained by carbonizing a plant such as wood or bamboo, and bamboo charcoal is particularly preferable. Because it exhibits excellent adsorptivity due to its unique porosity, it effectively absorbs and removes water film generated on the road surface on ice, increasing the frictional force with the road surface, and significantly improving the performance of the rubber composition on ice. Can do.

  As the bamboo material, various bamboos such as Soso bamboo, maitake, light bamboo, crested bamboo, etc. can be used as the material, and its production method carbonizes the bamboo material in the same manner as Bincho charcoal. For example, it is described in JP-A-9-324180. As in the method for producing bamboo charcoal, the one obtained by steaming bamboo material using a kiln and carbonizing is used.

The charcoal is iodine adsorption method (JIS K6217) specific surface area measured by the 150 meters ² / g or more, preferably 200 meters ² / g or more, further, it is desirable at 250 meters ² / g or more. The larger the specific surface area, the more porous and the water absorption speed, and the upper limit is not particularly limited as long as the form of the bamboo charcoal particles is not impaired. In addition, the specific surface area of commercially available Bincho charcoal is about 100 to 130 m ² / g.

  Bamboo charcoal granules used in the present invention are, for example, commercially available bamboo charcoal made of Soso bamboo, pulverized into granules using a known pulverizer (for example, a ball mill), classified into a predetermined particle size range, and classified. For example, a granular material screened to a predetermined particle size by a standard sieve described in JIS Z8801 can be used.

  The average particle diameter of the granular material is preferably 10 to 500 μm, and if it is less than 10 μm, even if the specific surface area is large, the absolute water absorption amount of the granular material is reduced, resulting in insufficient water absorption and dewatering effects, exceeding 500 μm. In addition, the wear resistance deteriorates due to a decrease in dispersibility and processability in rubber and the fracture characteristics of rubber, and the granular material tends to fall off early due to friction with the road surface.

  In addition, the shape of bamboo charcoal is not particularly limited, and various shapes such as a substantially spherical shape, a substantially cubic shape, a substantially columnar shape, a needle-like shape, or a mixture thereof can be used.

  In the rubber composition of the present invention, the blending amount of bamboo charcoal is 1 to 20 parts by weight with respect to 100 parts by weight of the diene rubber component, and if it is less than 1 part by weight, the water absorption and water removal effects are insufficient and the performance on ice is sufficient. If the amount exceeds 20 parts by weight, the processability of the rubber deteriorates, the hardness of the rubber increases, the fracture property decreases due to the decrease in elastic modulus, and the wear resistance deteriorates. Improvement is also a limit.

  In addition, since the bamboo charcoal used for this invention is a natural material, even if it falls out of a rubber composition and scatters by abrasion of a tread, of course, it does not have a bad influence on an environment or health.

  Further, the porous carbide of the plant of the present invention can be obtained from the above-mentioned bamboo charcoal, natural materials such as wood, grass, etc. as a material, and a porous material exhibiting adsorption performance easily and inexpensively by the above carbonization method or the like. Therefore, it is advantageous as a material for the rubber composition in terms of cost.

  In the rubber composition of the present invention, vegetable granules such as pulverized walnut shells can be further blended and used. By using the plant granules together, the water film removal effect of bamboo charcoal and the plant granules can be used. The on-ice performance can be further improved by the synergistic effect of the body scratching effect.

  The above-mentioned vegetable granular material is harder than the hardness of ice, that is, has a Morse hardness of 2 or more, seed shells such as walnuts and strawberries, or fruit nuclei such as peaches and plums are pulverized by a known method into granular materials. This is a granule that protrudes from the rubber surface and exhibits an anti-slip action on the road surface on ice due to the hooking effect on the road surface, and has been subjected to surface treatment for improving rubber adhesion to ensure adhesion with rubber. It is preferable that

  The vegetable granule preferably has a particle size of 100 to 600 μm after surface treatment with a rubber adhesion improver. If the particle size is less than 100 μm, the amount of protrusion from the rubber surface is small and the hooking effect is not good. If it exceeds 600 μm, it is larger than the diameter of the bubbles contained in the ice, so the action of destroying the bubbles becomes small, and the distortion of the matrix rubber around the granular material becomes excessive, causing cracks and falling off the tread. It becomes easy.

  As a surface treatment agent for improving the rubber adhesion of plant granules, for example, a mixture (RFL treatment liquid) of resorcin / formalin resin initial condensate and natural rubber latex or diene synthetic rubber latex can be used.

  In the RFL, the solid content concentration is adjusted to 5 to 25% by weight so that the adhesion rate to the plant granular material is 1 to 5% by weight, and the plant granular material is immersed therein, or the plant The above mixture is sprayed and dried to obtain a vegetable granule that has been subjected to a surface treatment with improved rubber adhesion, reground by a known method, sieved to a desired particle size distribution, A vegetable granule having a particle size range is obtained.

  The blending amount of the plant granule subjected to the rubber adhesion improving surface treatment is preferably 1 to 30 parts with respect to 100 parts by weight of the diene rubber. When the amount is less than 1 part, the slip resistance on the frozen road surface is inferior, and when it exceeds 30 parts, the wear resistance is lowered.

  Furthermore, in the rubber composition of this invention, you may mix | blend 1.5-10 parts of the vegetable granular material about 30-250 micrometers in particle size with which the rubber-adhesion improvement surface treatment is not given. In this case, the hole formed by dropping the plant granular material that has not been surface-treated during the running of the tire from the tread surface, along with bamboo charcoal, has the effect of water absorption and dewatering, and the plant property that has been subjected to the rubber adhesion improvement treatment A synergistic effect with the hooking effect produced by the granular material is exhibited.

  The rubber composition of the present invention includes reinforcing agents and fillers such as carbon black and silica used in normal rubber industry, process oil, zinc oxide, in addition to the above rubber components, bamboo charcoal granules, and vegetable granules. , Stearic acid, softener, plasticizer, anti-aging agent (amine-ketone, aromatic secondary amine, phenol, imidazole, etc.), vulcanizer, vulcanization accelerator (guanidine, thiazole, sulfur Formulated chemicals such as phenamides and thiurams are appropriately blended and used within a normal range.

Here, as carbon black, when used in the tread portion of a studless tire, the nitrogen adsorption specific surface area (N ₂ SA) is 70 m ² / from the viewpoint of low temperature performance of the rubber composition, wear resistance, rubber reinforcement, and the like. g, the DBP oil absorption is preferably 105 ml / 100 g or more, more preferably N ₂ SA is 80 to 200 m ² / g, and the DBP oil absorption is 110 to 150 ml / 100 g. When it is low, the rubber strength and modulus are lowered, and conversely, when N ₂ SA is high, heat generation is increased, which is not preferable. Specifically, SAF, ISAF, and HAF grade carbon black are exemplified, and the blending amount is in the range of about 10 to 80 parts by weight with respect to 100 parts by weight of the rubber component.

  In addition, when silica is used, wet silica, dry silica, surface-treated silica or the like is used, and the blending amount is 50% by weight with respect to 100 parts by weight of the rubber component from the viewpoint of balance of tan δ of rubber, reinforcing property, and electrical conductivity. The total amount with carbon black is preferably about 10 to 120 parts by weight.

  The rubber composition of the present invention has a JIS hardness (based on JIS K7215, measurement temperature 23 ° C.) of 30 to 60, more preferably 40 to 50, in order to maintain the low temperature performance of the rubber composition on icy and snowy roads. It is desirable to adjust to the range.

  The rubber composition can be prepared by kneading according to a conventional method using a rubber mixer such as an ordinary Banbury mixer or kneader.

  The pneumatic tire of the present invention is a product tire manufactured through a vulcanization process according to a conventional method after forming a tread portion of a tire by a rubber extruder using the rubber composition and molding an unvulcanized tire. The 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.

  Therefore, in the pneumatic tire of the present invention, the bamboo charcoal particles of the tread rubber are exposed on the tread surface and innumerable holes are formed on the surface, and the water film on the road surface on ice is exhibited with excellent water absorption and water removal effects. The tire performance on ice and dry road surfaces is improved by improving the coefficient of friction between the tread rubber and the road surface, improving the performance on ice and maintaining the steering stability and rolling resistance without reducing the wear resistance. Can be achieved. Moreover, the further performance on ice can be implement | achieved by using together a vegetable granule. In addition, the use of natural materials without causing road damage and asphalt dust does not adversely affect health and the environment due to the scattering of bamboo charcoal and plant granules.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this.

  The rubber composition which mix | blended the bamboo charcoal of each Example of Table 2 and Table 3, and a comparative example, Bincho charcoal, a vegetable granule, and a fly-pontite-silica composite, the compounding component of Table 1, compounding amount Each rubber composition was obtained by blending a predetermined amount into the basic blending and kneading using a Banbury mixer with a normal capacity of 20 liters. The obtained rubber compositions of Examples and Comparative Examples were vulcanized at 150 ° C. for 30 minutes, and the hardness of the vulcanized rubber was measured according to JIS K7215 (23 ° C.). Further, a studless tire (size 185 / 65R15 88Q) using each rubber composition as a cap tread was prototyped, mounted on a vehicle, and performance on ice and wear resistance were evaluated according to the following methods. The results are shown in Tables 2 and 3.

Bamboo charcoal, Bincho charcoal, vegetable granules and frypontite-silica composites listed in Tables 2 and 3 are as follows.
* 1: charcoal 1 ... bamboo charcoal of specific surface area 315m ² / g, average particle diameter 300μm
* 2: Bamboo Charcoal 2 ... Bunso bamboo bamboo charcoal, specific surface area 315m ² / g, average particle size 1μm
* 3: Bamboo charcoal 3 ... Bamboo charcoal of Somune bamboo, specific surface area 315m ² / g, average particle size 1000μm
* 4: Bincho charcoal (flooded rice cake): specific surface area 125 m ² / g, average particle size 300 μm
* 5: Plant granular material (ground walnut shell, surface-treated with RFL treatment solution) ... Nippon Walnut, soft grid # 46, average particle size 300 μm
* 6: Fly-pontite-silica composite: Mizusawa Chemical Industries, Mizukanite HP

[Abrasion resistance]
Mount four test tires on a front-wheel drive passenger car with a displacement of 2000 cc, rotate the front and rear wheels every 2,500 km on a general dry road surface, and average the remaining tread groove depth after running 10,000 km The amount of wear was determined from the value and evaluated as wear resistance. The results are shown in index notation with Comparative Example 2 as 100. The higher the value, the better the wear resistance.

[Performance on ice]
Four test tires were mounted on a front-wheel drive passenger car with a displacement of 2000 cc, and after a preliminary run of 100 km on a dry asphalt road, The braking distance was measured by operating the ABS at a speed of 40 km / h. The average value of 10 measurements was used as an evaluation of the performance on ice, and the result was shown as an index with Comparative Example 2 taken as 100. The larger the value, the shorter the braking distance and the better.

  As is apparent from the results shown in the table, all examples in which a predetermined amount of bamboo charcoal 1 according to the present invention is blended can significantly improve the performance on ice while maintaining the wear resistance within a practical range. it can. However, when the blending amount is less than 1 part by weight, only a slight improvement in performance on ice can be obtained (Comparative Example 5), and when it exceeds 20 parts by weight, the wear resistance is remarkably deteriorated (Comparative Example 6). . Furthermore, Example 4, 5 which used the vegetable granule together can improve a performance on ice dramatically without impairing abrasion resistance by a synergistic effect of both.

  On the other hand, Comparative Example 3 blended with bamboo charcoal 2 having a small average particle size has little effect on improving the performance on ice, and even if this amount is increased, the expectation of improving the performance on ice as in Examples is not obtained, and the wear resistance is greatly increased. Decline is expected. In Comparative Example 4 in which bamboo charcoal 3 having an average particle size that is too large is blended, the wear resistance is greatly reduced for the improvement in performance on ice. In addition, the performance on ice of Comparative Examples 2 and 7 in which the fly-pontite-silica composite and Bincho charcoal were blended did not reach the examples of the present invention, and the porous characteristics of bamboo charcoal greatly contributed to the improvement of the performance on ice. I understand.

As described above, according to the present invention, a rubber composition having improved frictional force against the road surface on ice without practically lowering the wear resistance is obtained, and shoes including pneumatic tires such as studless tires and industrial vehicle tires are used. It can be widely used for rubber products that require anti-slip properties such as bottoms, mats, and flooring.

Claims (4)

A rubber composition comprising 1 to 20 parts by weight of a granular material having an average particle diameter of 10 to 500 μm made of a plant porous carbide based on 100 parts by weight of a diene rubber component. The rubber composition according to claim 1, wherein the porous carbide is bamboo charcoal. The rubber composition according to claim 1 or 2, further comprising a vegetable granule such as pulverized walnut shell. A pneumatic tire using the rubber composition according to claim 1 for a tread portion.