JP2002114868A - Rubber composition for studless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for studless tires capable of markedly improving the on-ice grip performance of the tires made therefrom. SOLUTION: This rubber composition for studless tires is characterized by comprising 100 pts.wt. of natural rubber and/or a diene-based synthetic rubber, 2-20 pts.wt. of staple fiber, 3-15 pts.wt. of a powder processed product containing cellulose matter and 5-30 pts.wt. of silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a studless tire, and more particularly to a tread rubber composition for a studless tire having improved grip performance on ice and snow road surfaces.

[0002]

2. Description of the Related Art In recent years, as tires for traveling on icy and snowy roads,
Studless tires are widespread. For studless tires, various studies have been made to improve the sticking friction and the excavation friction, which are factors that govern the friction between rubber and a road surface, for the purpose of improving the performance on ice.

As one of the methods, a method has been proposed in which a part of a filler (carbon black) is made of silica and a silane coupling agent is used in combination to lower the elastic modulus (modulus) at a low temperature to improve the adhesive friction. (JP-A-8-73657).

[0004] Further, a powdered product of a cellulosic substance is blended into a rubber composition, and the ice surface of the powdered product is scratched,
A method has been proposed in which a spike effect is exhibited, and the friction with the ice surface is increased by the unevenness and edges of the dropout holes generated when the powder processed product falls due to the progress of wear, thereby improving the grip performance on ice ( JP-A-2-1673
No. 53).

[0005] In addition, there has been proposed a method of blending short fibers and orienting the short fibers perpendicular to the tread surface, digging and raising friction, and improving grip performance on ice (Japanese Patent Laid-Open No. 2000-168315). ).

[0006] These methods have improved the grip performance on ice of studless tires, but have not yet reached the performance of spiked tires.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for a studless tire capable of significantly improving the grip performance on ice.

[0008]

According to the present invention, there is provided a powdered product 3 containing 2 to 20 parts by weight of short fibers and a cellulose substance per 100 parts by weight of natural rubber and / or diene synthetic rubber.
A rubber composition for a studless tire, comprising 5 to 30 parts by weight of silica and 5 to 30 parts by weight of silica, and a short fiber having a diameter of 5 to 100 μm and a length of 0.2 to 5.0 mm.
0.4 to 3.0 parts by weight of the rubber composition for a studless tire described above, the rubber composition for a studless tire having an average particle diameter of a powder processed product of 20 to 600 μm, and further a silane coupling agent. And a rubber composition for a studless tire.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition for a studless tire of the present invention contains a rubber component, short fibers, a powder processed product containing a cellulose substance, and silica.

[0010] The rubber component used in the rubber composition of the present invention is a natural rubber (NR) and / or a diene-based synthetic rubber.

The diene-based synthetic rubber is not particularly limited. For example, styrene-butadiene rubber (SB
R), butadiene rubber (BR), isoprene rubber (I
R), ethylene-propylene-diene rubber (EPD)
M), chloroprene rubber (CR), acrylonitrile-
Butadiene rubber (NBR) and the like. These may be used alone or in combination of two or more. Above all, from the point of improving performance on ice and snow, NR
And BR are preferably used, and in this case, the obtained rubber is soft even at a low temperature, and the tread's grounding properties can be secured.

The short fibers used in the present invention are blended into a rubber composition and oriented in an extrusion step.

In Japanese Patent Application Laid-Open No. 2000-168315,
It is a proposal to orient the short fibers in a direction perpendicular to the tread surface to improve digging and raising friction.For example, when forming a tread for a studless tire using the rubber composition of the present invention, the short fibers are oriented in the tire circumferential direction. It is preferable to orientate.

[0014] The short fibers oriented in the circumferential direction of the tire fall off by running, and fine slits (micro elongated grooves) are formed on the tread block surface. The falling holes remove the water film (water draining effect), and the edges improve the friction on ice, thereby greatly improving the grip performance on ice of the studless tire.

[0015] The content of the short fibers is 2 to 20 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the rubber component. If the content of the short fibers is less than 2 parts by weight, the intended effect of removing a water film cannot be sufficiently exhibited. Conversely, if the amount exceeds 20 parts by weight, the reinforcing property is poor and the abrasion resistance is adversely affected, the tread surface is easily roughened after running, and the contact area of the rubber itself with the ice surface is reduced, so that the adhesive effect (grip on ice) Performance) tends to decrease. Furthermore, from the viewpoint of balancing the reinforcing property and the grip performance on ice, it is 5 to 10
It is particularly preferred that the amount be parts by weight.

The short fibers used in the present invention include, for example, glass fibers, aluminum whiskers,
Polyester fiber, nylon fiber, polyvinyl formal fiber, aromatic polyamide fiber and the like can be employed. Of these, inorganic short fibers having a specific gravity of 2.0 or more, such as glass fibers and aluminum whiskers, which are excellent in scattering during kneading, optimum shape by kneading, and orientation, are preferred.

The diameter of the short fibers is preferably 5 to 100 μm.
m, particularly preferably from 20 to 80 μm. If the diameter of the short fiber is less than 5 μm, the dropout hole (micro elongated groove) of the short fiber is too small, and the effect of removing the water film between the target tread rubber and the road surface tends to be insufficient. is there. On the other hand, if the diameter of the short fibers exceeds 100 μm, the reinforcing properties are poor and the abrasion resistance is adversely affected, the tread surface is easily roughened after running, and the contact area between the rubber itself and the ice surface is reduced. Grip performance) tends to decrease. Further, it is particularly preferable that the thickness is 35 to 65 μm from the viewpoint of achieving a balance between the reinforcing property and the grip performance on ice.

The length of the short fibers is preferably from 0.2 to 5.
0 mm, and more preferably 1.4 to 2.6 mm.
If the length of the short fiber is less than 0.2 mm, the effect of removing the water film between the tread rubber and the road surface tends to be insufficient, and if it exceeds 5.0 mm, the adhesive effect tends to decrease.

The content of the powdered product containing the cellulose material is 3 to 15 parts by weight, preferably 5 to 10 parts by weight, based on 100 parts by weight of the rubber component. If the content of the powder processed product is less than 3 parts by weight, the desired spike effect cannot be sufficiently exhibited. Conversely, if the amount exceeds 15 parts by weight, the whole rubber becomes high hardness, the powder processed product itself is installed on the road surface, and the contact area of the base rubber itself with the ice surface is reduced, so that the adhesive effect tends to decrease. , And the abrasion resistance performance becomes insufficient.

The cellulosic substance in the powdered product containing the cellulosic substance used in the present invention is disclosed in
It is the same as the cellulosic substance described in Japanese Patent No. 167353, and refers to rice hulls, wheat hulls, cork pieces, sawdust and the like. Further, the powder processed product may contain silica, clay, wood element, fatty acid, water, and the like as components other than the cellulose substance. Cellulose material is present in powdered products in 20
Preferably, it is contained in an amount of up to 40% by weight, more preferably 25 to 35% by weight. If the content of the cellulose substance is less than 20% by weight, the dispersion during kneading tends to be poor, and if it exceeds 40% by weight, the hardness tends to be low, and the spike effect tends to decrease.

The above-mentioned powdered product contains a cellulose substance in its component, so that it is compatible with rubber, that is, it is easily dispersed during kneading, and loosely bonds with rubber to form a powdered product. Although it easily falls off due to the progress of abrasion, it is difficult to reduce the tearing strength and, for example, it is difficult to generate a groove bottom crack.

Also, unlike the case where a cellulosic substance having a high hardness such as a metal is blended, there is no problem of abrasion of the pavement road surface or a decrease in the adhesion effect with the iced road surface due to an increase in hardness of the rubber as a whole. . On the other hand, if the hardness is lower than that of the cellulose material, a sufficient spike effect cannot be exhibited. In this regard, the hardness of the crushed plant material such as the rice hulls, wheat hulls, cork pieces and sawdust is optimal. Especially, the hardness of rice hulls is optimal. In addition, since the rice husk, which is a natural product, is a powder with irregularities, it has good compatibility with rubber, does not reduce tearing strength, and has performance such as not reducing groove bottom crack resistance. .

The average particle size of the powder processed product is preferably 2
0 to 600 μm, particularly preferably 100 to 200 μm
It is. If the average particle diameter of the powder processed product is less than 20 μm, the intended spike effect tends to be insufficient. On the other hand, if the average particle diameter exceeds 600 μm, the reinforcing property is poor and the wear resistance is adversely affected, the tread surface is easily roughened after running, and the contact area between the rubber itself and the ice surface is reduced. Grip performance on ice) tends to decrease. Further, the thickness is particularly preferably from 100 to 120 μm from the viewpoint of achieving a balance between the reinforcing property and the grip performance on ice.

The amount of silica in the present invention is 5 to 30 parts by weight based on 100 parts by weight of the rubber component.
If the compounding amount of silica is less than 5 parts by weight, the adhesive effect between the tread and the road surface decreases, and the performance on ice and snow tends to deteriorate,
If the amount exceeds 30 parts by weight, the abrasion resistance tends to deteriorate. In terms of balance between performance on ice and snow and wear resistance,
Further, it is preferably 5 to 25 parts by weight, particularly preferably 5 to 15 parts by weight.

The silica used in the present invention is not particularly limited as long as it has been conventionally used in the field of tires. Examples of commercially available silicas include Ultrasil VN3 (manufactured by Degussa) and Nipsil VN3 (Nippon Silica Co., Ltd.).
Manufactured by Tokusil USR (manufactured by Tokuyama Corporation), Z17
5Gr (Rhodia), Z165Gr (Rhodia), Z115Gr (Rhodia) and the like.

It is preferable that the rubber composition of the present invention further contains a silane coupling agent. The compounding amount of the silane coupling agent in the present invention is 100% of the rubber component.
It is preferably from 0.4 to 3 parts by weight, more preferably from 0.4 to 2.5 parts by weight, based on parts by weight. If the blending amount of the silane coupling agent is less than 0.4 parts by weight, the effect of adhesion between the tread and the road surface is reduced, and the performance on ice and snow tends to be deteriorated. , The costs tend to be higher.

The amount of the silane coupling agent is as follows:
Silica 8
It is preferably from 10 to 10% by weight.

The silane coupling agent used in the present invention is not particularly limited as long as it is a conventional one. For example, bis (3-triethoxysilylpropyl) tetrasulfen, α-mercaptopropyltrimethoxysilane, 3-silane Thiocyanatepropyltriethoxysilane, bis (3-triethoxysilylpropyl) disulfen and the like can be mentioned.

The rubber composition of the present invention includes, in addition to the rubber component, short fibers, and powder processed products, vulcanizing agents such as carbon black and sulfur commonly used in the rubber industry, and various vulcanizing agents. Additives such as accelerators, various softeners, various anti-aging agents, zinc oxide and stearic acid can be blended.

[0030]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but these do not limit the present invention.

Examples 1 to 11 and Comparative Examples 1 to 7 [Raw materials] Natural rubber: RSS # 3 (manufactured by Thailand) BR: Ubepol BR150B manufactured by Ube Industries, Ltd. Glass fiber A: manufactured by Nippon Sheet Glass (diameter) 10μ
glass fiber B: Nippon Sheet Glass Co., Ltd. (50 μm in diameter)
m, length 2.0 mm) Glass fiber C: Nippon Sheet Glass Co., Ltd. (4 μm in diameter)
m, length 0.15 mm) Glass fiber D: manufactured by Nippon Sheet Glass Co., Ltd. (diameter 120
Powdered product A containing cellulose: rice husk, rice hull, CELLON FIBER A manufactured by SARONFIBER
Type (SERONFIBER A TYPE) (average particle size 100 to 120)
μm) Powdered processed product containing cellulose B: Rice husk, rice hull, CELLON fiber A manufactured by SARONFIBER
Type (SERONFIBER A TYPE) (Average particle size 400 to 600
μm) Powdered product containing cellulose C: rice husk, rice husk, CELLON fiber A manufactured by SARONFIBER
Type (SERONFIBER A TYPE) (average particle diameter 40-60μ)
m) Silica: Degussa Ultrasil VN3 (Ultrasil VN3)
VN3) Carbon black: Show Black N220 manufactured by Showa Cabot Co., Ltd. Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa Process oil: Diana Process manufactured by Idemitsu Kosan Co., Ltd. PA32 Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant: Nocrack 6 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
C Stearic acid: Camellia stearic acid manufactured by NOF Corporation Zinc oxide: Two kinds of zinc oxide manufactured by Mitsui Kinzoku Kogyo Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator: Ouchi Shinko Chemical Industry Noxeller N manufactured by Co., Ltd.
S

[Vulcanized rubber] According to the compounding contents shown in Table 1, kneading was carried out by a conventional method using a Banbury mixer to obtain various rubber compositions. The obtained rubber composition was
Press vulcanization was performed at 50 ° C. for 45 minutes to obtain a vulcanized rubber.

[Tire] A studless tire for a truck bus having a tread made of the rubber composition was prepared by a conventional method.

[Breaking Performance on Ice] The tire was mounted on the front wheel of a 10-ton truck, and when traveling at a speed of 30 km / h, the stopping distance on ice required to stop was measured. The evaluation was shown as an index with the stopping distance of Comparative Example 1 being 100. The higher the index, the better the braking performance on ice. (Ice skid index) = (braking stop distance of Comparative Example 1)
÷ (braking stop distance of each compound) x 100

[Maneuverability on Ice and Snow] A tire was mounted on the front wheel of a 10-ton truck, and the running time of a figure eight-circle circuit having a total length of several hundred meters was measured on ice and snow. The evaluation was indicated by an index with the time of Comparative Example 1 taken as 100. The larger the index, the better the steering performance. (Ice grip index) = (Running time of Comparative Example 1) ÷
(Running time of each formulation) x 100

[Abrasion Resistance] Using a Lambourn abrasion tester, the amount of abrasion of the vulcanized rubber was measured at a temperature of 20 ° C., a slip ratio of 25%, and a test time of 3 minutes, and the volume loss of each compound was determined. Calculated. The volume loss of Comparative Example 1 was set to 100, and an index was expressed by the following equation. The larger the value, the better the wear resistance performance. Table 1 shows the results. (Lambourn abrasion index) = (Volume loss of Comparative Example 1) ÷
(Volume loss of each formulation) x 100

[0037]

[Table 1]

Examples 2, 3 and 4 and Comparative Examples 2 and 5
Comparing the evaluation results, short fibers (glass fibers)
It can be seen that when the blending amount is 2 to 20 parts by weight, the performance on ice and snow and the abrasion resistance are balanced.

Examples 2, 7 and 9 and Comparative Examples 3 and 6
Comparing the evaluation results, the compounded amount of the powder processed product is 3 to 1
It can be seen that at 5 parts by weight, the performance on ice and snow and the abrasion resistance are balanced.

Comparing the evaluation results of Examples 2 and 8 with Comparative Examples 4 and 7, it was found that the performance on ice and snow and the wear resistance were balanced when the amount of silica was 5 to 30 parts by weight. I understand.

In Comparative Examples 1 and 5 in which the powdered product and silica were blended, the performance on ice and snow was improved. In Examples 1 to 11 in which short fibers were further blended, the performance on ice and snow was significantly improved. I understand.

Comparing the evaluation results of Examples 1, 2, 10 and 11, it was found that when short fibers (glass fibers) having a diameter of 5 to 100 μm were mixed, the performance on ice and snow and the wear resistance were balanced. It turns out that there is.

Comparing the evaluation results of Examples 2, 5 and 6, it can be seen that Example 2 in which a powder processed product having an average particle diameter of 100 to 120 μm is blended has a good balance between performance on ice and snow and wear resistance. It turns out that there is.

[0044]

As is evident from the above results, the rubber composition of the present invention comprising short fibers, a powder processed product containing a cellulose substance, silica and a rubber component is used when used as a tread of a studless tire or the like. In addition, the drainage effect of the short fibers, the improvement of the excavated friction by the powdered product, and the improvement of the adhesive friction by the silica can greatly improve the grip performance on ice.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 9/00 C08L 9/00 // (C08L 7/00 (C08L 7/00 1:00) 1:00 (C08L 9/00 (C08L 9/00 1:00) 1:00) 1:00) (72) Inventor Takeshi Ota 3-6-9, Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo F-term (Sumitomo Rubber Industries, Ltd.) 4J002 AB013 AC01W AC02X AC03X AC06X AC07X AC08X AC09X BB15X BE064 CF004 CL004 DA096 DJ017 DL006 EX038 EX088 FA044 FA046 FA066 FA083 FD010 FD017 FD140 GN01

Claims (4)

[Claims] 1. 100 parts by weight of natural rubber and / or diene-based synthetic rubber contain 2 to 20 parts by weight of short fibers, 3 to 15 parts by weight of a powdered product containing a cellulose substance, and 5 to 30 parts by weight of silica. A rubber composition for a studless tire. 2. The rubber composition for a studless tire according to claim 1, wherein the short fibers have a diameter of 5 to 100 μm and a length of 0.2 to 5.0 mm. 3. The powder product has an average particle size of 20 to 600.
The rubber composition for a studless tire according to claim 1, wherein the rubber composition has a particle size of μm. 4. The method according to claim 1, wherein the silane coupling agent is added in an amount of 0.4 to
The rubber composition for a studless tire according to claim 1, which contains 3.0 parts by weight.