JP2005029708A - Studless tire rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a studless tire rubber composition capable of effectively removing a water screen of on-ice road surface and satisfying both of the removing property of the water screen and the wear resistance. <P>SOLUTION: The studless tire rubber composition comprises 100 pts.wt. rubber component composed of a diene-based rubber and 2-30 pts.wt. cellulosic fine powder having ≤100 μm average particle diameter and preferably has 1-20 ratio (D1/D2) of a long diameter (D1) of the cellulosic fine powder to a short diameter (D2) of the cellulosic fine powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a studless tire rubber composition, and relates to a studless tire rubber composition having improved performance on ice without lowering the wear resistance.

  Pneumatic tires used in winter in cold regions are increasingly used as studless tires instead of spiked tires, and the development of a studless tire rubber composition that improves driving, braking performance and handling stability on icy road surfaces has been developed. Although many have been made, these rubber compositions are not satisfactory in tire performance such as wear resistance and handling stability on dry road surfaces, and are required to satisfy both tire performances on both road surfaces.

  Examples of measures for improving the rubber composition that improves the frictional force between the tread rubber and the road surface on ice include the use of butadiene rubber having a low glass transition temperature and the addition of a softening agent to improve hysteresis friction that maintains low hardness even at low temperatures. Some of the filler carbon black is replaced with silica to maintain low-temperature elastic modulus to improve adhesive friction, and foam rubber is used in the tread to increase irregularities on the tread surface. There are materials that improve the friction by digging up (scratching) by blending high-molecular substances, inorganic substances, plant pulverized materials, hard substance particles such as metal powder, and hollow particles.

It is also effective to remove the water film between the tread rubber generated by the contact pressure of the tread and frictional heat and the road surface on ice to improve the friction coefficient. For example, a powder processed product containing short fibers and a cellulose substance A technique is disclosed that improves the grip on ice by the effect of removing the water film by the slit from which the short fibers have been dropped and the spike effect by the cellulose substance, using a combination of silica and silica (Patent Document 1).
JP 2002-114868 A

  The above-mentioned adhesion friction, digging friction, and water film removal effects are important on the road surface on ice with a small coefficient of friction, but tread rubber containing a large amount of silica improves on-ice performance but has lower reinforcement than carbon black. However, the abrasion resistance is inferior, there is a problem of rubber kneadability and conductivity lowering, and those blended with foamed rubber or hard substance granules have the disadvantage that the abrasion resistance is lowered in the drying path.

  Further, the rubber composition for studless tires of Patent Document 1 can improve braking performance and steering stability on the road surface on ice. However, since the orientation of short fibers and the particle size of the cellulose substance are relatively large, It does not fully satisfy both performance and wear resistance.

  The present invention improves the performance on ice by removing the water film between the tread rubber and the road surface on ice while maintaining the wear resistance, and blends cellulose particles excellent in water absorption performance and compatibility with the rubber. Thus, an object of the present invention is to provide a studless tire rubber composition having excellent on-ice performance suitable for a tread of a studless tire, which can effectively remove a water film and achieve both wear resistance.

  The present invention focuses on the fact that the cellulose material can absorb water on the ice effectively without using the cellulose material as a foreign substance in the rubber composition by using a cellulose material having water absorption as a fine powder. It reached.

  That is, the present invention is a studless tire rubber composition comprising 2 to 30 parts by weight of a cellulose fine powder having an average particle size of 100 μm or less with respect to 100 parts by weight of a rubber component made of a diene rubber.

  In this case, it is preferable that the ratio D1 / D2 of the major axis (D1) and the minor axis (D2) of the fine cellulose powder is 1 to 20.

  According to the studless tire rubber composition of the present invention, the fine cellulose powder (powder) having an average particle size of 100 μm or less exhibits excellent water absorption, instantly absorbs water on ice, removes the water film, and removes the water film. Can improve the on-ice performance of studless tires by improving the adhesion effect and friction coefficient between the tire and the road surface on the ice, and has a good physical compatibility with the polymer and compounding agent in the rubber composition, and foreign matter in the rubber. The strength and hardness of the rubber can be maintained.

  The smaller the particle size, the smaller the particle size, the larger the surface area of the particle, the better the water absorption ability and the better the compatibility with rubber. Reduce. Moreover, when the value of D1 / D2 becomes large, the form of the cellulose particles becomes long, the rubber hardness is increased, and the wear resistance is lowered. In addition, the blending amount of the cellulose fine powder exhibits a water absorption effect from about 2 parts by weight with respect to 100 parts by weight of the rubber component, and if it exceeds 30 parts by weight, the wear resistance decreases with an increase in rubber hardness, which is not preferable. .

  This cellulose fine powder is prepared based on natural fiber, and has excellent physical compatibility with polymers and compounding agents in rubber compositions, similar to carbon black and other fillers. In addition, it does not become a foreign substance in the rubber, and the rubber characteristics can be secured without lowering the rubber strength and elasticity. In addition, even if the treads are scattered with the wear of the tread, there is no adverse effect on the human body or environmental pollution.

  In the studless tire rubber composition according to the present invention, the fine cellulose powder exhibits excellent water absorption, effectively removes the water film on the road surface on ice, and at the same time suppresses the increase in hardness of the rubber composition and maintains the wear resistance. it can. Therefore, the studless tire to which this studless tire rubber composition is applied improves the adhesion performance and friction coefficient on the ice road surface and improves the ice performance while maintaining the tire performance such as wear resistance and strength, and on the snow and snow road surface and the dry road surface. Both tire performance can be achieved.

  Embodiments of the studless tire rubber composition according to the present invention will be described below.

  The studless tire rubber composition of the present invention contains 2 to 30 parts by weight of a cellulose fine powder having an average particle diameter of 100 μm or less with respect to 100 parts by weight of a rubber component made of a diene rubber.

  As a rubber component used for this invention, the diene rubber generally used for the tread of a studless tire can be used individually or two or more types of blends can be used.

  As the diene rubber, natural rubber, various butadiene rubbers, various styrene butadiene rubbers and isoprene rubbers are preferably used from the viewpoints of low temperature characteristics, abrasion resistance, steering stability, etc. required for studless tires, and in particular, glass transition. It is preferable to use a blend of butadiene rubber and natural rubber having a temperature of −50 ° C. or lower as the main rubber component.

  When the butadiene rubber and natural rubber are used in a blend, if the ratio of the butadiene rubber is too small, it is difficult to obtain low temperature characteristics of the rubber composition, and conversely, if it is increased, the processability deteriorates and the cut resistance and the chipping tendency tend to decrease. Therefore, the ratio of natural rubber / butadiene rubber is preferably 20/80 to 90/10, more preferably 40/60 to 70/30.

  The cellulose fine powder used in the present invention includes natural cellulose composed of fiber of plant fibers, such as cotton, hemp, rice hulls and rice hulls, rice husks, walnut hulls and peach nuts, and peanut hulls. Pulverized pulverized material such as ginko shells, cork, and softened pulp and hardwood plant fibers treated with sodium hydroxide, sodium bisulfite, sodium hypochlorite, etc. It may be a regenerated cellulose such as rayon, or a pulverized product of a cellulose derivative such as alkyl cellulose derived from cellulose.

  Among these, a pulverized pulp is preferable in terms of water absorption performance, ease of particle size adjustment, availability of raw materials, price, and the like. Also, recycled paper such as newspapers, magazines and cardboard other than refined pulp can be recycled.

  This cellulose fine powder is excellent in physical compatibility with polymers and compounding agents in the rubber composition, so that it does not become a foreign substance in rubber like other reinforcing agents such as carbon black and silica. By using it, it is possible to obtain stable rubber properties such as strength, elastic modulus and hardness without deteriorating rubber reinforcement.

  The average particle size of the cellulose fine powder is preferably 100 μm or less, and the smaller the particle size, the larger the surface area of the particles, the better the water absorption capacity and the excellent water absorption, and the better the water absorption between the rubber composition and the road surface on ice. The water film generated in the water can be absorbed instantly to remove the water film, and the adhesion effect between the tread rubber and the road surface on ice and the coefficient of friction can be increased to improve the on-ice performance of the studless tire.

  As the particle size of the cellulose fine powder increases, the water absorption ability decreases and the desired performance on ice cannot be exhibited. Cellulose granules also become a foreign substance, impairing the reinforcing property of the rubber composition, and increasing the rubber hardness. Reduces wear resistance.

  However, if the particle size is too small, it becomes difficult to adjust the particle size and handleability, and it is not possible to expect an improvement in water absorption capacity as the particle size is reduced. Therefore, the lower limit of the average particle size is considered to be about 10 μm.

  Moreover, it is preferable that ratio D1 / D2 of the major axis (D1) and minor axis (D2) of a cellulose fine powder is D1 / D2 = 1-20, More preferably, it is 1-10. When D1 / D2 exceeds 20, the shape of the cellulose particles becomes long, that is, it becomes a long and slender fibrous shape, and the cellulose is entangled in the rubber. Abrasion is reduced, and kneadability and dispersibility are also deteriorated. Accordingly, D1 / D2 is preferably close to 1 from the viewpoint of water absorption performance, rubber properties, kneading properties and the like.

  As the cellulose fine powder, a fine powder obtained by pulverizing a cellulose substance using a pulverizer such as a ball mill, and then sieving it with a sieve to select an average particle size can be used. The sieve can be sieved to a predetermined particle size by a standard sieve described in JIS Z8801, for example.

  Further, D1 and D2 of the cellulose fine powder are average values of the long side length and the short side length of the fine powder measured using an electron microscope.

  The blending amount of the cellulose fine powder is preferably 2 to 30 parts by weight with respect to 100 parts by weight of the rubber component.

  The cellulose fine powder exhibits a water-absorbing effect from a blending amount of about 2 parts by weight, and if it is less than 2 parts by weight, significant water absorption performance cannot be exhibited. If it exceeds 30 parts by weight, the rubber hardness increases and the wear resistance tends to decrease, which is not preferable.

  In addition, this cellulose fine powder is adjusted based on natural fiber, has excellent chemical stability, does not adversely affect other compounding agents, and maintains stable rubber properties such as rubber strength and elasticity. Even if it is scattered in the air due to the wear of the tread of the studless tire, it does not cause adverse effects on the human body or environmental pollution.

  In addition to the above rubber components, the studless tire rubber composition of the present invention includes reinforcing agents such as carbon black and silica, fillers, softeners, plasticizers, vulcanizing agents, and vulcanization accelerators that are used in the normal rubber industry. Compounding chemicals such as agents and anti-aging agents can be appropriately blended and used within a normal range.

Carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 70 m ² / g or more and a DBP oil absorption of 105 ml / 100 g from the viewpoint of the low temperature performance of the tread rubber of the studless tire, wear resistance and rubber reinforcement. More preferably, N ₂ SA is 80 to 200 m ² / g, DBP oil absorption is 110 to 150 ml / 100 g, and more preferably 20 to 100 parts by weight of rubber component. It is preferably used in the range of 100 parts by weight, and specific examples include SAF, ISAF, and HAF grade carbon black.

  After the rubber composition is kneaded by a rubber mixer such as a normal Banbury mixer or kneader, the tread portion of the tire is formed by a rubber extruder or the like, and an unvulcanized tire is created by normal tire molding, A vulcanized product tire is produced according to conventional methods.

  Therefore, in the studless tire in which the studless tire rubber composition of the present invention is applied to the tread rubber, the cellulose fine powder of the tread rubber exhibits excellent water absorption, and the water film between the tread and the road surface on ice is effectively removed. In addition, the adhesion effect between the tread rubber and the road surface on ice and the coefficient of friction are increased to improve the on-ice performance of the studless tire, while maintaining the tire performance such as wear resistance and strength, and to achieve both tire performance on the snowy and dry road surface. it can.

  Examples of the studless tire rubber composition of the present invention will be described below.

  Carbon black, oil, and cellulose fine powders A to D and the following common compounding agents are blended with 100 parts by weight of a rubber component of 50 parts by weight of natural rubber (NR) and 50 parts by weight of butadiene rubber (BR) ( Parts by weight) and kneaded using a normal 20 liter Banbury mixer to prepare studless tire rubber compositions of the examples and comparative examples.

  The average particle size of the cellulose fine powders A to D is as follows.

[Cellulose fine powder]
Cellulose fine powder A: Average particle size = 80 μm
Cellulose fine powder B: Average particle size = 50 μm
Cellulose fine powder C: Average particle size = 20 μm
Cellulose fine powder D: Average particle size = 130 μm

  Cellulose fine powders A to D are obtained by pulverizing pulp using a ball mill and then sieving using a sieve to select fine powders having a predetermined average particle diameter. The fine powder is mixed.

  The raw rubber compounded in each example and comparative example, common various compounding agents, and compounding amount (parts by weight) are as shown below.

[Raw rubber and common compounding agents]
・ Natural rubber (NR): RSS # 3 (50 parts by weight)
-Butadiene rubber (BR): BR01 (50 parts by weight) manufactured by JSR Corporation
Carbon black (CB): Showa Cabot Co., Ltd. Show Black N339 (50 parts by weight)
・ Oil: Aromatic process oil (20 parts by weight)
・ Zinc flower: No. 3 zinc flower (2 parts by weight)
・ Stearic acid: Industrial stearic acid (2 parts by weight)
・ Wax: Microcrystalline wax (2 parts by weight)
・ Anti-aging agent: Nouchi 6C (2 parts by weight) manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Sulfur: 5% oil-treated sulfur (1.5 parts by weight)
・ Vulcanization accelerator CZ: Nouchira CZ (1 part by weight) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  A cap tread was prepared by using an extruder for each of the studless tire rubber compositions of Examples and Comparative Examples, and a test studless tire having a general structure in which the cap tread was applied and having a size of 185 / 70R14 was manufactured. Abrasion and performance on ice were evaluated by the following methods. The results are shown in Table 1.

[Abrasion resistance]
Four test tires were mounted on a 1800 cc front-wheel drive domestic passenger car, traveled on a general dry road for 10,000 km, the amount of wear was determined from the tread remaining groove depth after traveling, and Comparative Example 1 was taken as 100. Indicated by an index. The larger the value, the better.

[Performance on ice]
Four test tires were mounted on a 1800 cc front-wheel drive domestic passenger car, and the tires were fully locked at a speed of 40 km / h on an icy road surface at an icing temperature of -5 ° C., and the braking distance was measured. It was shown as an index with Comparative Example 1 as 100. The larger the value, the better.

  As shown in Table 1, each of Examples 1 to 4 blended with cellulose fine powders A, B, and C having an average particle size of 100 μm or less has the same wear resistance as that of the conventional (Comparative Example 1) performance level. Maintain and improve performance on ice. Here, Example 2 in which the blending amount of the fine powder was increased from 5 parts by weight to 15 parts by weight, and Examples 3 and 4 in which the particle diameter was reduced greatly improved the performance on ice. It can be seen that the blending amount and the average particle size are greatly affected, and in particular, the effect of improving the water absorption capability by increasing the surface area by reducing the diameter is large. Further, in Example 4 in which ultrafine particles were formed, improvement in performance on ice was not observed, and it is considered that a sufficient effect can be obtained with an average particle diameter of about 20 μm.

  In Comparative Example 2 in which 40 parts by weight of cellulose fine powder A was blended, as in the case of increasing the amount of filler, Comparative Example 3 in which rubber hardness was increased and abrasion resistance was decreased, and cellulose fine powder D having a large particle size was blended. In the rubber composition, celluloses are entangled with each other or anisotropy is generated in the rubber to increase the hardness and greatly reduce the wear resistance.

  Therefore, the studless tire using the studless tire rubber composition of the present invention containing a predetermined amount of cellulose fine powder having an average particle size of 100 μm or less as the tread maintains the wear resistance at the same level as the conventional tire, and the tread rubber and ice It is possible to effectively remove the water film from the road surface and improve the performance on ice.

  The studless tire rubber composition of the present invention can be used in combination with other means for improving the performance on ice, for example, use of foamed rubber, blending of organic and inorganic fine particles, blending of silica and the like. .

  As described above, the studless tire rubber composition according to the present invention increases the adhesion effect and friction coefficient with the road surface on ice, improves the performance on ice, and maintains the tire performance such as wear resistance and strength. It can be used for various anti-slip rubber products such as shoe soles, mats, flooring, as well as treads of studless tires for passenger cars, trucks and buses.

Claims (2)

For 100 parts by weight of the rubber component made of diene rubber,
A studless tire rubber composition comprising 2 to 30 parts by weight of fine cellulose powder having an average particle size of 100 μm or less. The studless tire rubber composition according to claim 1, wherein a ratio D1 / D2 of a major axis (D1) and a minor axis (D2) of the cellulose fine powder is 1 to 20.