JP3244841B2 - Rubber composition for tread - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for a tread. More specifically, the present invention relates to a rubber composition for a tread that can be suitably used for, for example, a studless tire.

[0002]

2. Description of the Related Art Conventionally, when traveling on snow or ice, for example, spike tires and studless tires have been used.

[0003] The above-mentioned spiked tire is excellent in gripping property particularly on an icy road surface, but its use is restricted because it wears the road surface when traveling on a paved road and generates dust.

Therefore, in recent years, studless tires have been spotlighted as an alternative to spike tires, and studless tires having grip properties similar to spike tires have been developed.

[0005] However, the above-mentioned studless tire exhibits performance comparable to that of a spiked tire in terms of performance on snow, but may have poor grip performance on a frozen road surface as compared with a spiked tire. ,
The improvement is required.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides a rubber composition for a tread which can be suitably used for a studless tire having an excellent grip property on a frozen or frozen road surface. It is intended to provide.

[0007]

That is, the present invention relates to a rubber composition containing 100 parts by weight of a diene rubber containing natural rubber or polyisoprene rubber and polybutadiene rubber as main components.
A rubber composition silica 30-100 parts by weight is blended, 50 wt% or more and the general formula of the silica _{(I): (C n H} 2n + 1 O) 3 Si- (CH 2) m -S _{k - (CH 2) m -Si} (C n H 2n + 1 O) 3 (I) ( wherein, m is an integer from 1 to 6, n represents an integer of 1 to 4, k is 1
Silane coupling agents represented by 6 an integer of) and the general formula _{(II): (C n H} 2n + 1 O) 3 Si- (CH 2) m -X (II) ( wherein, m and n Is the same as above, X is a mercapto group,
The present invention relates to a rubber composition for a tread in which at least one kind of a silane coupling agent represented by an amino group, an epoxy group or a vinyl group is kneaded in advance with natural rubber or polyisoprene rubber.

[0008]

Functions and Examples Factors governing the friction of tire tread rubber include (a) friction due to hysteresis,
(B) Friction due to adhesion, (c) digging up (scratching)
If friction is considered and moisture is present, (d) drainage effect is also added.

[0009] On a road surface having a small friction coefficient such as a frozen road surface, (a) there is almost no effect of friction due to hysteresis, and (b) friction due to sticking, (c) digging and raising friction, and (d) drainage effect are very important. It becomes.

The present invention focused on friction due to (b) adhesion among the factors governing friction, and studied the effects of various powders and additives on the frictional force. It has been found that the rubber has a large frictional force on a frozen road surface (on ice), and that the silica is combined with a diene rubber having excellent low-temperature properties as a rubber component to further increase the frictional force on a frozen road surface. However, when the silica is further kneaded with natural rubber or polyisoprene rubber together with a silane coupling agent, and then kneaded with polybutadiene,
It has been completed based on the fact that the increase in hardness at low temperatures is suppressed and the frictional force at low temperatures is further enhanced.

As described above, the rubber composition for a tread of the present invention contains 30 to 100 parts by weight of silica with respect to 100 parts by weight of a diene rubber containing natural rubber or polyisoprene rubber and polybutadiene rubber as main components. Wherein 50% by weight or more of the silica and a specific silane coupling agent are previously kneaded with natural rubber or polyisoprene rubber.

In the present invention, as the base rubber, a diene rubber containing natural rubber or polyisoprene rubber and polybutadiene rubber as main components is used. Here, the main component is 50 wt% in the diene rubber. %.

The compounding ratio of the above natural rubber or polyisoprene rubber and polybutadiene rubber (natural rubber or polyisoprene rubber / polybutadiene rubber: weight ratio)
If it is too small, it will not be possible to incorporate the silica required to carry out the present invention, and the amount of polybutadiene will increase, resulting in poor processability and damage such as cutting and chipping. 20 / 80-90 / 10, especially 40 / 60-70
/ 30 is preferable.

In the present invention, for example, isoprene rubber, styrene-butadiene copolymer rubber or the like may be blended with the diene rubber used in the present invention as long as the object of the present invention is not impaired.

The diene rubber contains carbon black as a filler. If the compounding amount of the carbon black is too large, the hardness increases and the performance on ice becomes inferior, and if it is too small, the cut resistance tends to decrease. It is preferably about 30 to 50 parts by weight based on 100 parts by weight of the system rubber. Preferably, the carbon black is normally selectively distributed to the polybutadiene rubber.

The silica is a component used for imparting a grip property on a frozen road surface to the obtained rubber composition for a tread, and at least 50% by weight of the silica is
Partitioned into natural or polyisoprene rubber and the remaining
Up to 50% by weight is distributed to the polybutadiene rubber. If the amount distributed to the natural rubber or the polyisoprene rubber is less than 50% by weight, the amount of silica distributed to the polybutadiene increases, so that an increase in hardness at low temperatures cannot be suppressed.

If the amount of the silica is too small, the effect of compounding the silica is not sufficiently exhibited, and if the amount is too large, the obtained rubber composition for a tread is not obtained. Since the hardness increases and the performance on a frozen road surface decreases, the amount is 30 to 130 parts by weight, preferably 40 to 70 parts by weight, per 100 parts by weight of the diene rubber.

The primary particle size of the silica is not particularly limited. However, in order to uniformly disperse it in the obtained rubber composition for a tread, it is usually 10 to 40 μm, preferably 15 to 20 μm.
It is preferably about m μm.

Further, a silane coupling agent is compounded to improve the reinforcing property of the rubber composition for a tread of the present invention.

[0020] As the silane coupling agent of the general formula _{(I): (C n H} 2n + 1 O) 3 Si- (CH 2) m -S k - (CH 2) m -Si (C n H 2n ₊₁ O) ₃ (I) (wherein, m is an integer of 1 to 6, n is an integer of 1 to 4, k is 1
Silane coupling agents represented by 6 an integer of), the general formula _{(II): (C n H} 2n + 1 O) 3 Si- (CH 2) m -X (II) ( wherein, m and n Is the same as above, X is a mercapto group,
A silane coupling agent represented by an amino group, an epoxy group or a vinyl group), and these silane coupling agents can be used alone or in combination of two or more.

The diene rubber of the silane coupling agent
If the compounding amount per 100 parts by weight is too small, the reinforcing property becomes small, the abrasion resistance and cut resistance become inferior, and if it is too large, the obtained tread rubber can be obtained. Since the hardness of the composition increases and the performance on a frozen road surface tends to decrease, 1 to 10 parts by weight,
In particular, it is preferably 3 to 8 parts by weight.

In the present invention, the silane coupling agent is previously blended with natural rubber or polyisoprene rubber. As described above, when the silane coupling agent is previously blended with natural rubber or polyisoprene rubber, the distribution of silica can be controlled, the increase in hardness at low temperatures is suppressed, and the frictional force at low temperatures is further increased.

When the amount of the silane coupling agent blended with the natural rubber or polyisoprene rubber is small, the amount of silica selectively distributed to the natural rubber or polyisoprene rubber is reduced. If the improvement in the frictional force at low temperatures is small and large,
Since the hardness of the obtained rubber composition for tread increases and the performance on a frozen road surface decreases, the rubber composition is used in an amount of 1 to 10 parts by weight, preferably 3 to 8 parts by weight based on 100 parts by weight of the diene rubber. Adjusted.

Therefore, in the present invention, a natural rubber or polyisoprene rubber is blended with a predetermined amount of a silane coupling agent. The silane coupling agent can be blended.

In the rubber composition for a tread of the present invention, it is preferable to use a cellulosic material in order to improve adhesive friction and digging-up friction.

Specific examples of the cellulosic material include rice husks, husks, cork pieces, and ground materials such as sawdust. Of these, rice husks are particularly preferred in terms of hardness.

If the average particle size of the cellulose material is too small, the digging effect is not sufficiently exhibited, and if the average particle size is too large, the surface of the tread tends to be rough after running, and The contact area with the ice surface is reduced, and the sticking effect is reduced. Therefore, the thickness is preferably 20 to 600 μm, particularly preferably 100 to 200 μm.

If the amount of the cellulose material is too small, the desired spike effect is unlikely to be sufficiently exhibited, and if it is too large,
Since the hardness of the obtained rubber composition for tread tends to be high and the adhesive effect tends to be small, the amount is preferably 3 to 20 parts by weight, more preferably 5 to 15 parts by weight, based on 100 parts by weight of the diene rubber.

The rubber composition for a tread of the present invention may contain, if necessary, a softening agent such as a naphthene-based process oil or a paraffin-based process oil, a vulcanization aid such as zinc oxide or stearic acid, a mercaptobenzothiazole ( MBT), dibenzothiazyl disulfide (MBT)
S), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2
-Additives such as vulcanization accelerators such as thiazole accelerators such as benzothiazylsulfenamide (CBS), organic fibers, and foaming agents can be blended. The amounts of these additives are appropriately adjusted within a range not to impair the object of the present invention, and are preferably added to polybutadiene.

When the temperature at which the natural rubber or polyisoprene rubber is kneaded with silica and a silane coupling agent is too low, the effect of blending the silane coupling agent is sufficiently exhibited. If the temperature is too high, and if the temperature is too high, the rubber will deteriorate, so 120-180 ° C, especially 140-
The temperature is preferably about 170 ° C.

By kneading the component mainly composed of the natural rubber or polyisoprene rubber and the component mainly composed of the polybutadiene, the rubber composition for a tread of the present invention can be obtained. The temperature at the time of kneading is not particularly limited, but may be usually about 150 to 170 ° C.

In the present invention, when the two components are kneaded, the component mainly composed of natural rubber or polyisoprene rubber is "island" or the component mainly composed of polybutadiene is "sea" due to the compatibility of the rubber. The so-called sea-island structure is formed. In such an "island", the longest length of each island portion is generally about 2 × 10 ^{−5 to} 1.5 × 10 ⁻³ mm.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited to only these examples.

Examples 1 to 5 50 parts by weight of natural rubber, silica (manufactured by Nippon Silica Industry Co., Ltd.)
50 parts by weight of Nipsil VN3) and 3 parts by weight of a silane coupling agent (Si69, manufactured by Degussa) were kneaded at 160 ° C. using an open mill to obtain a rubber component A.

Using the obtained rubber component A, various components were blended with the rubber component A so that the composition shown in Table 1 was obtained.
The mixture was kneaded using a Banbury mixer at ℃ to obtain a rubber composition for tread.

Comparative Examples 1 to 4 Various components were adjusted to have the compositions shown in Table 1 and
Was kneaded using a Banbury mixer to obtain a rubber composition for tread.

Next, Examples 1 to 3 and Comparative Examples 1 to 4
Size using the rubber composition for tread obtained
165 SR13 type studless tires were manufactured, and various physical properties were examined according to the following methods. Table 1 shows the results.
Shown in

(B) Tire ice test Test location: Hokkaido Nayoro ice surface test course Air temperature: -3 ° C Test vehicle: FF 1500cc domestic passenger car Tire: 165 SR13 steel radial tire Internal pressure: 1.9 kg / cm ² Test method: Acceleration: The time required to accelerate from a stop and travel 50 m was examined. Braking: The distance required to stop the vehicle at a speed of 30 km / h was examined. (Note) The value is shown as a relative value when the value of Comparative Example 1 (standard tire) is set to 100. The smaller the value, the better the tire performance.

(B) Rubber Hardness Hs Rubber hardness Hs (JIS-A) at 0 ° C. was measured according to the method specified in JIS K6301.

(C) Skid resistance (exponent) Portable Skid-Resistance Tester as a pendulum type skid tester
r) The skid resistance on ice at −3 ° C. was measured using a model TR-300, and expressed as a relative value when the value of Comparative Example 1 was set to 100. The higher the numerical value, the better the skid resistance.

In Table 1, each abbreviation means the following. NR: Natural rubber BR: Butadiene rubber Silica: Nipsil manufactured by Nippon Silica Industry Co., Ltd.
VN3 N220: carbon black SC: silane coupling agent (manufactured by Degussa, S
i69) PO: Procell oil (Dianaprocel PS32, manufactured by Idemitsu Kosan Co., Ltd.) SA: Stearic acid ZO: Zinc oxide NBBA: N-tert-butyl-2-benzothiazylsulfenamide DPG: 1,3-diphenylguanidine CP: Cellulose material (rice hull, average particle size: 15
0 μm)

[0042]

[Table 1]

From the results shown in Table 1, it can be seen that the rubber compositions for treads obtained in Examples 1 to 3 have a high skid resistance on ice and a good grip on the icy road surface. Understand.

[0044]

The rubber composition for a tread of the present invention exhibits excellent grip properties particularly on frozen or frozen road surfaces, and thus can be suitably used for studless tires.

Continued on the front page (72) Inventor Isamu Tsumori 41-1 Shimizu, Uozumi-cho, Akashi-shi, Hyogo Sumitomo Rubber Fish House Dormitory S602 References JP-A-50-88150 (JP, A) JP-A-2-170840 (JP, A) JP-A-2-274740 (JP, A) JP-A-2-274739 (JP, A) 2-167353 (JP, A) JP-A-5-27177 (JP, A) JP-A-6-240052 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 21/00 C08K 3/36 C08K 5/54 C08L 1/02 B60C 1/00

Claims (2)

(57) [Claims] 1. A natural rubber or polyisoprene rubber,
Diene rubber 100 composed mainly of polybutadiene rubber
Relative to the weight part, a rubber composition silica 30-100 parts by weight is blended, 50 wt% or more and the general formula of the silica _{(I): (C n H} 2n + 1 O) 3 Si- ( _{CH 2) m -S k - (} CH 2) m -Si (C n H 2n + 1 O) 3 (I) ( wherein, m is an integer from 1 to 6, n represents an integer of 1 to 4, k is 1
Silane coupling agents represented by 6 an integer of) and the general formula _{(II): (C n H} 2n + 1 O) 3 Si- (CH 2) m -X (II) ( wherein, m and n Is the same as above, X is a mercapto group,
A rubber composition for a tread, wherein at least 1 to 10 parts by weight of a silane coupling agent represented by an amino group, an epoxy group or a vinyl group is kneaded in advance with natural rubber or polyisoprene rubber. 2. The rubber composition for a tread according to claim 1, which comprises 3 to 20 parts by weight of a cellulose substance having an average particle diameter of 20 to 600 μm based on 100 parts by weight of the diene rubber.