JP2675256B2 - Tire tread rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire tread rubber composition, and more particularly to a tire tread rubber composition having improved grip on a frozen road surface.

[0002]

2. Description of the Related Art In order to prevent dust pollution caused by spike tires, the ban on spike tires has been legislated, and studless tires have been used in place of spike tires in cold regions. As a result of improvements, studless tires having a grip similar to that of spike tires have been developed and are currently used.

[0003] Factors governing the friction between the tread rubber and the road surface that affect the grip of a studless tire include: Hysteresis loss friction 2. 2. Adhesive friction Although there is excavation friction, the friction due to hysteresis loss is extremely small on roads with extremely low friction coefficient, such as frozen roads, and the ratios of sticking friction and excavation friction are large.

The surface morphology of the tread pattern and tread rubber is important for increasing the excavation frictional force. Spike tires have a large digging and frictional force, but studless tires have also been devised to increase the ruggedness of the tread surface by using foamed rubber or mixing organic fibers in order to increase the digging and frictional force. The unevenness of the tread surface has an effect of eliminating a water film generated between the tread surface and the frozen road surface and increasing the adhesive friction force. However, in this method, the adhesive friction force is indirectly increased by increasing the actual contact area, and there is a limit in increasing the actual contact area, and there is a limit in increasing the adhesive friction force.

Since the rubber itself has an effect on increasing the adhesive frictional force, for example, it is also effective to soften the rubber to increase the contact area with the road surface. For this purpose, the amount of filler has been reduced, butadiene rubber or isoprene rubber, which hardens even at low temperatures, and a softener has been added. Therefore, it was not possible to make it extremely soft and was an insufficient measure.

As described above, the present studless tires have insufficient grip characteristics and exhibit performance comparable to spiked tires in terms of performance on snow. In some cases, the grip performance is inferior to that of spiked tires due to such conditions, and improvement is required.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a tread for a studless tire used in a studless tire capable of exhibiting excellent grip even on a frozen road surface. It is to provide a rubber composition.

[0008]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors in order to achieve the above object, liquid polyisoprene and polybutadiene having a hydroxyl group are used as rubber components in an amount of 3-4.
The present invention was completed by discovering that a rubber composition occupying 0% (weight%, the same applies hereinafter) and having a silylating agent added thereto acts to improve the adhesive friction force and is very effective.

That is, in the present invention, the liquid polyisoprene having a hydroxyl group and / or the liquid polybutadiene having a hydroxyl group occupy 3 to 40% of the rubber component, and the rubber component 10
The silylating agent is added in an amount of 2 to 1 with respect to 0 part (part by weight;
The present invention relates to a tire tread rubber composition containing 5 parts.

[0010]

FUNCTION AND EXAMPLE In the present invention, the silylating agent imparts an adhesive frictional force to the tire tread, which leads to an improvement in grip of the tire. Further, it is considered that the liquid rubber having a hydroxyl group, which is hydrophilic, has the function of increasing the adhesive frictional force on the frozen road surface by increasing the affinity with ice.

As the rubber component in the present invention, natural rubber, isoprene rubber or butadiene rubber having a small increase in hardness at low temperatures is preferably used in order to increase the actual contact area of the frozen road surface on ice and increase the adhesive frictional force. .
These rubbers can be used alone or in any combination.

The rubber component in the present invention contains a liquid polyisoprene or a polybutadiene having a hydroxyl group alone or in combination.

Both the above-mentioned liquid polyisoprene and liquid polybutadiene can be used, but the effect of improving the adhesive frictional force is larger with liquid polyisoprene.

As the liquid polyisoprene having a hydroxyl group, one having 2 to 10 hydroxyl groups per molecule and having a number average molecular weight of about 10,000 to 60,000 is preferable from the viewpoint of tire performance and workability. Kuraray LIR
506 (having about 10 hydroxyl groups per molecule and having a number average molecular weight of 25,000) and the like.

The liquid polybutadiene having a hydroxyl group has hydroxyl groups at both ends and has a number average molecular weight of 1500 to 1500.
About 4000 is preferable in terms of tire performance and workability, and as a commercial product, Po from Idemitsu Petrochemical Co., Ltd.
ly bd R-45 HT (number average molecular weight 270
0) and Poly bd R-15 HT (number average molecular weight is 2700).

The liquid polyisoprene and polybutadiene having a hydroxyl group comprise 3 to 40% of the rubber component in total.
%, Preferably 5 to 25%. If it is less than 3%, no improvement in grip properties on a frozen road surface is observed, and if it is more than 40%, the breaking characteristics of rubber tend to decrease, and wear resistance and cut resistance tend to decrease.

Examples of the silylating agent to be added to the rubber composition of the present invention include chlorosilane compounds, alkoxysilane compounds and silazane compounds.

Examples of the chlorosilane compound include phenyltrichlorosilane and diphenyldichlorosilane. Examples of the alkoxysilane compound include phenyltriethoxysilane, isobutyltrimethoxysilane, diphenyldimethoxysilane and the like. Examples of the silazane compound include hexamethyldisilazane.

In addition to the above, silylating agents such as N, O- (bistrimethylsilyl) acetamide, N, N-bis (trimethylsilyl) urea and tert-butyldimethylchlorosilane may be used.

The silylating agents can be used alone or in any combination.

The silylating agent is blended in an amount of 2 to 15 parts, preferably 3 to 8 parts, based on 100 parts of the rubber component. If it is less than 2 parts, the effect of increasing the adhesive frictional force is hardly obtained, and if it is more than 15 parts, the unreacted silylating agent is deposited on the surface to reduce the slip resistance, and conversely the performance on ice tends to be deteriorated. There is.

In the rubber composition of the present invention, organic fibers may be mixed in order to enhance the drainage effect and the scratching effect, and foamed rubber may be used as a rubber component.

In the tire tread rubber composition of the present invention, if necessary, a compounding agent usually used for compounding tire rubbers, such as an antioxidant, a softening agent, zinc white, stearic acid, a vulcanization accelerator, and a vulcanization agent. Agents, sulfur and the like can be appropriately mixed.

The tire tread rubber composition of the present invention can be produced by a usual method using a rubber component, carbon black, a silylating agent and the above-mentioned usual compounding agents. However, since an alkaline substance such as an antioxidant hinders the reaction of the silylating agent, the antioxidant is not added during the base kneading, that is, the kneading of the components excluding the vulcanizing agent. It is preferable to add an antioxidant together with the sulfurizing agent. An antioxidant having low reactivity may be added during kneading of the base. It is more preferable to add at the time of base kneading from the viewpoint of dispersion. Base kneading is 130-1
It is carried out at 70 ° C, preferably 140 to 160 ° C. 1
If it is lower than 30 ° C, the reaction of the silylating agent tends not to be sufficiently carried out, and if it is higher than 170 ° C, deterioration of rubber molecules tends to occur.

The tire tread rubber composition of the present invention can be applied to treads such as studless tires for passenger cars, studless tires for trucks and studless tires for buses.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Experimental Example 1-1 A vulcanizing agent (sulfur, accelerators) and an antioxidant other than the vulcanizing agent (sulfur, accelerators) were base kneaded at 150 ° C. ± 5 ° C. using the following composition, and 100
A tread rubber composition was prepared by adding a vulcanizing agent and an antioxidant and kneading at a temperature of ± 5 ° C.

Natural rubber 65 parts Butadiene rubber 30 parts Liquid polyisoprene ⁽¹⁾ 5 parts Carbon black ⁽²⁾ 50 parts Process oil ⁽³⁾ 5 parts Silylating agent ⁽⁴⁾ 3 parts Stearic acid 2 parts Zinc white 4 parts Aging Inhibitor ⁽⁵⁾ 1 part Sulfur 1.5 parts Vulcanization accelerator ⁽⁶⁾ 0.5 parts As liquid polyisoprene (1), Kuraprene LIR506 manufactured by Kuraray Co., Ltd., carbon black (2)
Is N220 manufactured by Showa Cabot Co., Ltd., process oil (3) is Diana Process PS32 manufactured by Idemitsu Kosan Co., Ltd., and silylating agent (4) is KBE-103 (Phenyltris) manufactured by Shin-Etsu Chemical Co. (Ethoxysilane), anti-aging agent (5), Nocrac 6C (N-phenyl-N '-(1,3 dimethylbutyl) -P-phenylenediamine) manufactured by Ouchi Shinko Chemical Co., Ltd., vulcanization accelerator ( 6) is Nox cellar NS manufactured by Ouchi Shinko Chemical Co., Ltd.
(N-tert-butyl-2benzothiazylsulfenamide) was used.

Experimental Examples 1-2 to 1-10 A rubber composition was prepared in the same manner as in Experimental Example 1-1, except that the composition of natural rubber, butadiene rubber, liquid polyisoprene, liquid polybutadiene, and silylating agent was changed as shown in Table 1. Prepared. In addition,
As liquid polybutadiene, P manufactured by Idemitsu Petrochemical Co., Ltd.
poly bdR-45 HT was used.

[0030]

[Table 1]

Example 2 Experimental Example 2-1 Using the tread rubber composition of Experimental Example 1-1, 165R1
No. 3 studless tires were produced. The internal pressure of this tire is 2 kgf / cm ² and the domestically produced 1500 cc FF A
The vehicle was mounted on a BS (with an anti-lock braking system) vehicle, and the acceleration time and braking stop distance on an icy road were measured under the following conditions.

Measurement location: Sumitomo Rubber Industries, Ltd. Nayoro test course ice board road Temperature: -4 ° C Ice temperature: -3 ° C [acceleration time] Measure the time required to accelerate from a stopped state and run for 50m did. The results are shown in Table 2 as indices with the measurement time of Experimental Example 2-8 using a normal tread rubber composition taken as 100. The smaller the index, the better.

[Brake stop distance] The distance required to stop at the time of running at 30 km / h was measured. The results are shown in Table 2 as an index, with the distance in Experimental Example 2-8 using a normal tread rubber composition as 100. The smaller the index, the better.

Experimental Example 2-2 Experimental Example 2-using the tread rubber composition of Experimental Example 1-2
The same tire as that of No. 1 was produced. Using these tires, the acceleration time and braking stop distance were measured in the same manner as in Experimental Example 2-1. Table 2 shows the results.

Experimental Example 2-3 Experimental Example 2-3-1 Experimental Example 2-using the tread rubber composition of Experimental Example 1-3
The same tire as that of No. 1 was produced. Using these tires, the acceleration time and braking stop distance were measured in the same manner as in Experimental Example 2-1. Table 2 shows the results.

Experimental Example 2-3-2 The tread rubber composition of Experimental Example 1-3 was mixed with 1 base kneading.
Except at 20 ° C., the tire was prepared in the same manner as in Experimental Example 1-1, and a tire was produced in the same manner as in Experimental Example 2-1. Table 2 shows the results.

Experimental Example 2-3-3 Experimental Example 1--3 except that the antioxidant and zinc white were added to the tread rubber composition of Experimental Example 1-3 during base kneading.
A tire was prepared in the same manner as in Experimental Example 2-1, and the acceleration time and the braking stop distance were measured in the same manner.
Table 2 shows the results.

Experimental Examples 2-4 to 2-10 Experimental Examples 1-4, 1-5, 1-6, 1-7, 1-8, 1-
Experimental Example 2- Using the Tread Rubber Compositions 9 and 1-10
The same tire as that of No. 1 was produced. Using these tires, the acceleration time and braking stop distance were measured in the same manner as in Experimental Example 2-1. Table 2 shows the results.

[0039]

[Table 2]

In Example 2, the tread rubber composition of the present invention (Experimental example numbers 1-1, 1-2, 1-3, 1-4,
Experimental Examples 2-1 and 2- using 1-5, 1-6 and 1-7)
2, 2-3-1, 2-3-2, 2-3-3, 2-4, 2
In -5, 2-6 and 2-7, excellent results were obtained. In Experimental Examples 2-8, excellent results were not obtained because the tread rubber composition did not contain liquid polyisoprene or liquid polybutadiene and a silylating agent. Experimental Example 2-9
Has a longer accelerating time because it contains no silylating agent.
In Experimental Example 2-10, since the tread rubber composition containing too much silylating agent was used, the acceleration time and the braking stop distance were long.

[0041]

By using the tire tread rubber composition of the present invention, it is possible to obtain a studless tire having excellent grip performance on a frozen road surface and excellent acceleration performance and braking performance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-320420 (JP, A)

Claims (3)

(57) [Claims] 1. A liquid polyisoprene having a hydroxyl group and / or a liquid polybutadiene having a hydroxyl group accounts for 3 to 40% by weight of a rubber component, and 2 to 15 parts by weight of a silylating agent is added to 100 parts by weight of the rubber component. A tire tread rubber composition comprising: 2. The tire tread rubber composition according to claim 1, wherein the silylating agent is at least one selected from the group consisting of a chlorosilane compound, an alkoxysilane compound and a silazane compound. 3. A component other than a vulcanizing agent and an antioxidant is added to 130
The tire tread rubber composition according to claim 1 or 2, obtained by kneading the base at a temperature of 170 ° C to 170 ° C, and then adding a vulcanizing agent and an antioxidant to finish kneading.