JP2011168719A - Rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire having greatly improved on-ice braking performance while maintaining the wear resistance of the tire. <P>SOLUTION: The rubber composition for a tire contains 0.1-20 pts.wt. of a banana fiber and 1-50 pts.wt. of a crosslinked rubber particle having an average particle size of 5-2,000 nm and a glass transition temperature of -100 to -65°C based on 100 pts.wt. of a diene-based rubber component. Preferably, the banana fiber has an average fiber width of 1-500 μm and an average fiber length of 0.1-5 mm. Further, the composition preferably contains 0.1-20 pts.wt. of a vegetable granule based on 100 pts.wt. of the diene-based rubber component. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition for tires, and more particularly to a rubber composition for tires that can achieve both tire wear resistance and ice braking performance. The rubber composition for tires according to the present invention is particularly useful as a rubber composition for studless tires.

  For automobiles that run on icy road surfaces, studless tires with a tread part made up of a block are generally used. To improve the ground contact on the icy road surface, hollow particles and glass fibers are used for the tread rubber that constitutes the tread part. Many methods of blending hard materials such as plant granules are employed. For example, the following Patent Document 1 describes a tire rubber composition containing a surface-treated vegetable granule, and the following Patent Document 2 describes a tire rubber composition compounded with a fly-pontite-silica composite. Furthermore, in Patent Document 3 below, a rubber composition for tires containing a plant porous carbide is described.

  However, even if the above hard materials are blended, it is difficult to significantly improve the braking performance on the road surface (hereinafter referred to as “ice braking performance”) while maintaining the wear resistance of the tire. There was room for improvement.

  Patent Document 4 below describes a method for reducing the electrical resistance of a tread rubber by further blending non-wood fibers in a tread rubber composition for a tire containing silica. However, this patent document does not describe or suggest a method for achieving both wear resistance and ice braking performance of a tire.

  Further, Patent Document 5 below describes a tire rubber composition obtained by blending crosslinked rubber particles and vegetable granules. In a pneumatic tire manufactured from such a rubber composition for tires by a combination of crosslinked rubber particles and vegetable granules, great improvement is seen in terms of performance on ice and performance on snow. However, further improvement in performance is required in the market, and the actual situation is that pneumatic tires having characteristics exceeding the effects of these combinations are required.

JP-A-10-7841 JP 2001-123017 A JP 2005-162865 A JP 2002-69243 A JP 2008-24792 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition for a tire that significantly improves ice braking performance while maintaining the wear resistance of the tire.

  In order to solve the above-mentioned problems, the present inventors diligently studied a method for removing a water film generated between a road surface and a tire on an on-ice road surface having a small friction coefficient. And paying attention to the banana fibers that are discarded in large quantities as industrial waste, in the vulcanized rubber of the rubber composition containing banana fibers, the porous structure of the banana fibers greatly contributes to the removal of the water film I found it. In addition, in the vulcanized rubber of the rubber composition containing crosslinked rubber particles (hereinafter also referred to as “rubber gel”) together with the banana fiber, the water film removal effect caused by the banana fiber and the road surface caused by the rubber gel It has been found that the effect of improving the adhesion frictional force of the tire exerts a synergistic effect, and the wear resistance and ice braking performance of the tire can be achieved at a high level. The present invention has been made as a result of the above-described studies, and achieves the above-described object with the following configuration.

  That is, the tire rubber composition according to the present invention has 0.1 to 20 parts by weight of banana fibers, an average particle diameter of 5 to 2000 nm, and a glass transition point of 100 parts by weight of the diene rubber component. It contains 1 to 50 parts by weight of crosslinked rubber particles having a temperature of 100 ° C to -65 ° C.

  A rubber composition containing banana fibers can be obtained by adding banana fibers to a rubber component and mixing them by ordinary kneading. The banana fiber in the rubber composition is fibrillated and has a porous structure. In the tire obtained from the rubber composition according to the present invention, banana fibers are exposed on the surface, and the porous structure of the banana fibers absorbs and removes the water film, thereby removing the water film on the road surface on ice. can do.

  Further, when the banana fiber is dropped from the tire as the vehicle travels, the dropped portion becomes a microvoid, and a water film generated between the road surface and the tire can be removed by a capillary phenomenon due to the microvoid. In addition, the scratch effect is also exhibited by the edge effect of the edge portion of the microvoid. In addition, since banana fiber is a natural product, it goes without saying that even if it drops off from a tire or scatters, it does not have a great adverse effect on the environment or the human body.

  The porous structure of banana fibers and the microvoids that occur in the areas where the banana fibers have dropped off can effectively remove the water film that is generated between the road surface and the tire and causes slipping, and exhibits an edge effect. Is done. Further, by blending the rubber gel together with the banana fiber, the ice braking performance can be greatly improved while maintaining the wear resistance of the tire due to the synergistic effect with the adhesion frictional force caused by the rubber gel.

  In the tire rubber composition, the banana fibers preferably have an average fiber width of 1 to 500 μm and an average fiber length of 0.1 to 5 mm. According to such a configuration, in the microvoid generated in the portion where the banana fiber is dropped, the water film generated between the road surface and the tire can be particularly effectively removed, and the edge effect is more effectively exhibited. .

  In the tire rubber composition, it is preferable that 0.1 to 20 parts by weight of a vegetable granule is contained with respect to 100 parts by weight of the diene rubber component. According to such a configuration, the ice braking performance can be further improved by a synergistic effect with the scratching effect of the plant granules in addition to the effect of removing the water film generated between the road surface and the tire.

  The tire obtained by vulcanizing and molding the rubber composition according to the present invention is particularly useful as a studless tire because it has both wear resistance and ice braking performance.

  Examples of the diene rubber component used in the tire rubber composition according to the present invention include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene butadiene rubber (SBR), and butyl rubber (IIR). And diene synthetic rubbers such as acrylonitrile butadiene rubber (NBR). These diene rubbers may be used singly or as a blend of two or more.

  In the present invention, for example, when used in a tread of a studless tire with a blend of NR and BR, if the ratio of BR is too small, the low temperature characteristics of the rubber composition may be deteriorated. Deterioration and tear resistance may decrease. For this reason, the ratio of NR / BR is preferably about 30/70 to 80/20, more preferably about 40/60 to 70/30.

  Banana fiber is obtained from a banana stem, and can be specifically produced by the method described in Japanese Patent No. 4125065. This banana fiber is fibrillated in the rubber composition and has a porous structure.

  In the present invention, when blended with the diene rubber component, the average fiber width of the banana fibers is preferably 1 to 500 μm, the average fiber length is preferably 0.1 to 5 mm, and the average fiber width of the banana fibers is 10 to 10 mm. More preferably, the average fiber length is 70 μm and the average fiber length is 1 to 2 mm. By adjusting within this range, the water film generated between the road surface and the tire can be particularly effectively removed by the capillary phenomenon due to the microvoids in the microvoids generated in the portion where the banana fibers are dropped. In addition, the scratch effect is also exhibited by the edge effect of the edge portion of the microvoid.

  The rubber composition for tires according to the present invention further contains crosslinked rubber particles. Especially, the ice braking performance is greatly improved by the synergistic effect of the water film removal effect and edge effect obtained by the banana fiber and the improvement effect of the adhesion friction force with the road surface obtained by the rubber gel.

  When the rubber composition according to the present invention contains the rubber gel together with the banana fiber, the vulcanized rubber can reduce the temperature dependency of the rubber hardness from the normal temperature range to the low temperature range, and the adhesion friction of the rubber The power can be improved. The rubber gel preferably has an average particle size (DVN value according to DIN 53206) of 5 to 2000 nm, more preferably 20 to 600 nm, and still more preferably 40 to 40 nm, from the viewpoint of adhesive frictional force, workability and wear resistance. 200 nm.

  As the rubber gel, those having a glass transition point (Tg) in the range of −100 to −65 ° C. are used. More preferably, it is −100 to −70 ° C. By using such a low glass transition point, the effect of improving the adhesion friction force at low temperatures can be further enhanced. That is, if the glass transition point is high, the elastic modulus of the tread in the low temperature region increases, and the ice braking performance improvement effect may not be sufficient. Here, the glass transition point is measured according to JIS K7121.

  The rubber gel is a gelled rubber obtained by crosslinking a rubber dispersion. Examples of such rubber dispersion include rubber latex produced by emulsion polymerization, natural rubber latex, rubber dispersion obtained by emulsifying solution-polymerized rubber in water, and the crosslinking agent includes Examples thereof include organic peroxides, organic azo compounds, and sulfur-based crosslinking agents. The rubber particles can also be crosslinked by copolymerization with a polyfunctional compound having a crosslinking action during the emulsion polymerization of the rubber. Specifically, the methods disclosed in Japanese Patent No. 3739198, Japanese Patent No. 3299343, Japanese Translation of PCT International Publication No. 2004-504465, Japanese Patent Publication No. 2004-506058, and the like can be used.

  Examples of the rubber constituting the rubber gel include dienes such as butadiene rubber (BR), styrene butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), nitrile rubber (NBR), and chloroprene rubber (CR). Rubber, and butadiene rubber or natural rubber, or a blend rubber of these and other diene rubbers.

  The rubber gel preferably has a toluene swelling index Qi of 1 to 15, more preferably 1 to 10. By using a material having such a toluene swelling index Qi, the effect of improving the adhesion friction force at low temperatures can be further enhanced. The rubber gel preferably has a gel content of 94% by weight or more.

  Here, the toluene swelling index and the gel content are measured by allowing rubber particles to swell in toluene and then drying. That is, 250 mg of rubber particles were swollen under shaking in 25 mL of toluene for 24 hours, centrifuged at 20000 rpm, weighed (W), then dried to a constant mass at 70 ° C. Weigh dry weight. The gel content is the weight ratio (%) of the rubber particles after drying to the rubber particles used. The toluene swelling index is obtained by Qi = (wet weight) / (dry weight).

  As the rubber gel, those containing sulfur and a C═C double bond and modified with a compound having an OH (hydroxyl) group are particularly suitable. That is, a rubber particle obtained by modifying a sulfur-crosslinked rubber particle using a diene rubber as a base rubber using a compound having an OH group as a modifier is particularly preferably used. Such modification is described in, for example, Japanese Patent Application Publication No. 2004-050658, and examples of the modifying agent include hydroxybutyl acrylate or methacrylate, hydroxyethyl acrylate or methacrylate, hydroxypropyl acrylate or methacrylate. As described above, the tire performance can be further improved by using rubber particles modified with OH groups having good affinity with plant granules.

  As the rubber gel, a rubber gel modified with a compound containing sulfur and having reactivity to C═C double bond can also be used. Examples of such a compound include compounds that can be chemically bonded to rubber particles by a sulfur-containing reactive group, such as a mercapto group, dithiocarbamate, and xanthogenate. Such modification can be performed using, for example, the method disclosed in Japanese Patent No. 3739198.

  The rubber gel is preferably blended in an amount of 1 to 50 parts by weight with respect to 100 parts by weight of the diene rubber component, from the viewpoint of increasing the performance on ice and snow more sufficiently by suppressing the increase in rubber hardness at low temperatures. The lower limit is more preferably 5 parts by weight or more, and still more preferably 10 parts by weight or more. Further, the upper limit is more preferably 30 parts by weight or less, and still more preferably 20 parts by weight or less, from the viewpoint of suppressing deterioration of wear resistance.

  The tire rubber composition according to the present invention may further contain vegetable granules. By using the plant granules together, the ice braking performance can be further improved by synergistic action with the scratching effect of the plant granules.

  The above-mentioned vegetable granular material is harder than the hardness of ice, that is, the seed shells such as walnuts and persimmons having a Mohs hardness of 2 or more or the cores of fruits such as peaches and plums are pulverized by a known method into granular materials. It protrudes from the rubber surface and exhibits an anti-slip action on the road surface on ice due to the scratching effect on the road surface. In order to ensure adhesion with rubber, it is preferably a vegetable granule that has been subjected to surface treatment for improving rubber adhesion.

  The vegetable granule preferably has a particle diameter of 100 to 600 μm after surface treatment with a rubber adhesion improver, and if it is less than 100 μm, the amount of protrusion from the rubber surface is small and the scratching effect is insufficient. Yes, if it exceeds 600μm, it is larger than the size of bubbles contained in the ice, so the action to destroy the bubbles is reduced, and the matrix rubber around the granule becomes excessively distorted, causing cracks and falling off the tire surface. It becomes easy.

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

  The above RF treatment liquid is adjusted to a solid content concentration of 5 to 25 wt% so that the adhesion rate to the plant granules is 1 to 5 wt%, or the plant granules are immersed therein, Alternatively, the above mixture is sprayed onto the plant granules and dried to obtain a plant granule having a surface treatment with improved rubber adhesion, re-ground by a known method, and sieved to a desired particle size distribution. A plant granule having a predetermined particle size range is obtained.

  When the vegetable granular material is blended in the rubber composition for tire according to the present invention, the content is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the diene rubber component. When the blending amount is less than 0.1 parts by weight, the slip resistance on the frozen road surface is inferior.

  The tire rubber composition according to the present invention may further contain a plant porous carbide. By using the porous carbide of the plant in combination, the ice braking performance can be further improved by synergistic action with the scratching effect of the porous carbide of the plant.

  Porous carbides of plants are porous substances made of solid products whose main component is carbon obtained by carbonizing plants such as wood and bamboo. Among them, bamboo charcoal is due to its unique porosity. Since it exhibits excellent adsorptivity, it is possible to effectively absorb and remove the water film generated on the road surface on ice, increase the frictional force with the road surface, and remarkably improve the on-ice performance of the rubber composition.

  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.

Bamboo charcoal, 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.

  When the plant porous carbide is blended in the tire rubber composition according to the present invention, the content is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the diene rubber component. When the blending amount is less than 0.1 parts by weight, the slip resistance on the frozen road surface is inferior.

  The rubber composition for tire according to the present invention includes sulfur, carbon black, silica, silane coupling agent, zinc white, together with the diene rubber component, banana fiber, rubber gel, vegetable granule, and plant porous carbide. Compounding agents usually used in the rubber industry, such as stearic acid, vulcanization accelerators, vulcanization accelerators, vulcanization retarders, anti-aging agents, softeners such as waxes and oils, processing aids, etc. In the range which does not impair the effect, it can mix | blend suitably and can be used.

  Sulfur should just be normal sulfur for rubber | gum, For example, powder sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur etc. can be used. The sulfur content in the tire rubber composition according to the present invention is preferably 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the rubber component.

When carbon black is used in the tread portion of a studless tire, the nitrogen adsorption specific surface area (N ₂ SA) is 70 m ² / g or more from the viewpoint of the low temperature performance of the rubber composition, wear resistance, rubber reinforcement, etc., DBP The 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 these values are low, the rubber strength If the modulus decreases and the N ₂ SA increases, the heat generation increases, 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 diene rubber component.

  As the silica, wet silica, dry silica, surface-treated silica or the like is used, and the blending amount is less than 50 parts by weight with respect to 100 parts by weight of the diene rubber component from the viewpoint of balance of tan δ of rubber, reinforcing property, and electric conductivity. Preferably, the total amount with carbon black is preferably about 10 to 120 parts by weight.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, a polyphenol-based anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture.

  The tire rubber composition of the present invention comprises the diene rubber component, banana fiber, rubber gel, vegetable granule, plant porous carbide, sulfur, carbon black, silica, silane coupling agent, if necessary. Additives usually used in the rubber industry, such as zinc white, stearic acid, vulcanization accelerator, vulcanization accelerator, vulcanization retarder, anti-aging agent, softener such as wax and oil, processing aid, It can be obtained by kneading using a kneader such as a Banbury mixer, a kneader, or a roll, which is used in a normal rubber industry.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than a vulcanizing component such as sulfur and a vulcanization accelerator is previously kneaded to obtain a master batch, and the remaining components are added and further kneaded. Any of a method of adding and kneading the components in an arbitrary order, a method of adding all of the components simultaneously and kneading may be used.

  By using the rubber composition for tires according to the present invention to produce tire tread rubber by a known facility such as a rubber extruder, after molding an unvulcanized tire, vulcanization according to a known method, Tires can be manufactured. The obtained tire is particularly useful as a studless tire because it has both wear resistance and ice braking performance.

  The rubber composition of the present invention has a JIS hardness (based on JIS K6253, measurement temperature 23 ° C.) of 30 to 60, more preferably 45 to 55, in order to maintain the low temperature performance of the rubber composition on an ice road. It is desirable to adjust to the range.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. In addition, the evaluation item in an Example etc. measured as follows.

(1) Rubber hardness The rubber composition was vulcanized at 150 ° C for 30 minutes, and the rubber hardness of the vulcanized rubber at 23 ° C or -5 ° C was measured in accordance with JIS K6253. The evaluation results are shown in Table 1.

(2) Abrasion resistance A studless tire (195 / 65R15) in which each rubber composition is arranged on a tread is manufactured and mounted on a front-wheel drive passenger car (4WD) having a displacement of 2000 cc. Every 2,500 km on a general dry road surface Rotation of the front and rear wheels was performed, and the amount of wear was determined from the average value of the remaining depth of the four tread grooves after traveling 10,000 km to evaluate wear resistance. The result of Comparative Example 1 is shown as an index with 100 as the result. The higher the value, the better the wear resistance. The evaluation results are shown in Table 1.

(3) Ice braking performance Studless tires (195 / 65R15) in which each rubber composition is arranged in a tread are manufactured and mounted on a front-wheel drive type passenger car having a displacement of 2000 cc. After preliminary running of 100 km on a general dry road surface, The braking distance was measured by operating the ABS at a speed of 40 km / h on an ice surface with an air temperature of -5 ± 3 ° C and a road surface temperature of -3 ± 3 ° C. The average value of 10 measurements was used as an evaluation of ice braking performance, and the result of Comparative Example 1 was shown as 100 in terms of an index. The larger the value, the shorter the braking distance and the better. The evaluation results are shown in Table 1.

(Preparation of rubber composition)
The rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 3 are blended with 100 parts by weight of the diene rubber component in accordance with the blending formulation of Table 1, and kneaded using a normal Banbury mixer. Adjusted. Each compounding agent described in Table 1 is shown below.

a) Diene rubber component
(1) Natural rubber (NR) RSS # 3
(2) Polybutadiene rubber (BR) (Hicis BR “BR01”, manufactured by JSR)
b) Carbon black N339 ("Seast KH", manufactured by Tokai Carbon Co., Ltd.)
c) Silica ("Nip Seal AQ", manufactured by Nippon Silica)
d) Silane coupling agent (“Si75”, manufactured by Degussa)
e) Paraffin oil ("Process P200", manufactured by JOMO)
f) Banana fiber What was obtained by cutting a commercially available product by a known method Average fiber width of 10 to 70 μm, Average fiber length of 1 to 2 mm
g) Plant granule A commercially available walnut shell ("Soft Grid # 46", manufactured by Japan Walnut Co., Ltd.) crushed and surface-treated with an RF treatment solution (average diameter 300 μm)
h) Crosslinked rubber particles (rubber gel) Rubber gel based on butadiene rubber, average particle size 130 nm, toluene swelling index Qi = 5.9, gel content 97 wt%, Tg = −80 ° C., modified with hydroxybutyl methacrylate ("Micromorph 30B", manufactured by Rhein Chemie)
i) Stearic acid ("Lunac S-20", manufactured by Kao Corporation)
j) Zinc Hana (“Zinc Hana 1”, manufactured by Mitsui Kinzoku)
k) Anti-aging agent ("Antigen 6C", manufactured by Sumitomo Chemical Co., Ltd.)
l) Wax ("OZOACE0355", manufactured by Nippon Seiwa Co., Ltd.)
m) Vulcanization accelerator ("Soccinol CZ", manufactured by Sumitomo Chemical Co., Ltd.)
n) Sulfur Powdered sulfur (manufactured by Tsurumi Chemical Co., Ltd.)

  From the results of Table 1, the studless tires obtained from the tire rubber compositions of Examples 1 to 5 are more resistant to wear and ice braking than the studless tires obtained from the tire rubber composition of Comparative Example 1. It turns out that performance is compatible. On the other hand, it can be seen that the studless tire of Comparative Example 2 contains a large amount of banana fiber, so that the wear resistance deteriorates. Moreover, since the studless tire of Comparative Example 3 contains a large amount of rubber gel, it can be seen that the wear resistance is also deteriorated.

Claims (3)

  Crosslinked rubber particles having 0.1 to 20 parts by weight of banana fibers, an average particle diameter of 5 to 2000 nm, and a glass transition point of -100 ° C to -65 ° C with respect to 100 parts by weight of the diene rubber component 1 to 50 parts by weight of a rubber composition for tires.   The tire rubber composition according to claim 1, wherein the banana fibers have an average fiber width of 1 to 500 µm and an average fiber length of 0.1 to 5 mm.   Furthermore, the rubber composition for tires of Claim 1 or 2 which contains 0.1-20 weight part of plant-like granular materials with respect to 100 weight part of diene-type rubber components.