JP3349806B2 - 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 rubber composition, and more particularly to a natural rubber (NR) and / or a polyisoprene rubber (IR) and a styrene-butadiene copolymer rubber (SB).
R) and / or a rubber compound comprising polybutadiene rubber (BR) and a butadiene or an AB block copolymer comprising butadiene and styrene. Low heat build-up and wear resistance without lowering grip performance. It can be used for tire treads and sidewalls, and is also useful for track belt cover materials, diaphragms, conveyor belts, etc. It relates to a rubber composition.

[0002]

2. Description of the Related Art In recent years, rubber compositions for tires of automobiles and the like have been required to improve various performances such as running stability and fuel efficiency. For example, rubber compositions for tire treads have low heat build-up. In addition, good grip performance and abrasion resistance are required, and improvement in trauma resistance and fatigue life in repeated elongation are required while reducing the weight of the rubber composition for a tire sidewall.

[0003] As a rubber composition for a cap tread for fuel-efficient tires, for example, Japanese Patent Application Laid-Open No. 61-218404 proposes blending silica as a reinforcing agent to reduce heat generation. Is problematic in abrasion resistance. Japanese Patent Application Laid-Open No. 5-1298 proposes a method of reducing heat generation by using a terminal-modified (aromatic tertiary amino group) polymer, which also has a problem of abrasion resistance. Further, Japanese Patent Application Laid-Open No. 4-356544 discloses that a low heat-generating agent (dinitrodiamino compound) is blended to reduce rolling resistance and improve low-temperature characteristics, but this is effective only for polyisoprene. In addition, there is a problem that it lacks general practicality.

Further, Japanese Patent Application Laid-Open No. 5-170973 discloses a rubber composition for a tire tread having an improved low heat build-up while retaining a high degree of abrasion resistance by blending a specific improved carbon black. Although proposed, further improvement from the polymer side is required due to the ever-increasing demand for high wear resistance and low fuel consumption.

On the other hand, as a rubber composition for a tire sidewall, a blend of natural rubber / butadiene polymer rubber has conventionally been mainly used. However, if the gauge is reduced in accordance with a demand for weight reduction, scratch resistance is reduced. There was a problem.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention eliminates the above-mentioned problems of the prior art and improves the abrasion resistance while maintaining good grip performance and low fuel consumption. The purpose is to provide things.

Another object of the present invention is to provide a rubber composition which can improve the trauma resistance and the fatigue life in repeated stretching while responding to the demand for weight reduction.

[0008]

According to the present invention, (i)
Natural rubber (NR) and / or polyisoprene rubber (I
R) and (ii) styrene-butadiene copolymer rubber (S
(BR) and / or polybutadiene rubber (BR),
i) Styrene content 0-30% by weight and butadiene content 10
A block (A) having 0 to 70% by weight and a 1,2-vinyl bond content of 5 to 40%, and a 1,2-vinyl bond content of 70% at a styrene content of 0 to 30% by weight and a butadiene content of 100 to 70% by weight. The block (B) is composed of an AB block copolymer having a weight ratio (A) / (B) of 20 to 80/80 to 20. The polymer content is the total amount of the components (i), (ii) and (iii) 1
A rubber composition is provided that is 0.5 to 20 parts by weight per 00 parts by weight.

[0009]

According to the present invention, by blending (i) NR and / or IR and (ii) SBR and / or BR blend system with (iii) a specific block copolymer (AB), Abrasion resistance can be improved without lowering heat generation and grip performance, and furthermore, fatigue resistance and trauma resistance can be improved.

[0010] N compounded in the rubber composition according to the present invention
R, IR, SBR and BR can be any polymer conventionally used as a rubber component in various rubber applications, and the blend ratio of NR / IR and SBR / BR and (i) NR and / or IR / (Ii) The blend ratio of SBR and / or BR can be selected according to the use of the rubber composition. Such selection can be appropriately made by those skilled in the art. For example, as a rubber composition for a tire tread for a passenger car, NR / SBR = 20 to 80/8.
0 to 20, NR / BR = 40 to 60/60 to 40 as a rubber composition for a tire sidewall, and NR / BR = 8 as a rubber composition for a truck or bus tire tread.
0 to 95/20 to 5 can be selected.

Next, according to the present invention, the above-mentioned blend system comprises:
The object of the present invention can be achieved by blending a specific AB type block copolymer.
If the blending amount of the mold block copolymer is too small, the desired improvement effect cannot be obtained, and if it is too large, the original rubber physical properties such as low heat build-up and grip performance are lost. From this point of view, the AB block copolymer used in the present invention is 0.5 parts by weight of the AB block copolymer based on 100 parts by weight of all polymer components (including the AB block copolymer). -20 parts by weight, preferably 1-15 parts by weight.

The AB block copolymer used in the present invention comprises styrene (ST) and butadiene. The styrene content (ST) and 1,2-vinyl bond (VN) of the block components A and B, and the A component and The weight ratio (A) / (B) of the component B is as follows. (A) ST / VN = 0 to 30% by weight / 5 to 40%, preferably ST / VN = 5 to 30% by weight / 5 to 30% (B) ST / VN = 0 to 30% by weight / 70% or more , Preferably ST / VN = 5-30% by weight / 73-80% (A) / (B) = 20-80 / 80-20, preferably 25-65 / 65-25

If the styrene content of the block component (A) is too small, the strength of the block polymer itself is reduced, and the effect of improving the abrasion resistance obtained is reduced. Conversely, if the amount is too large, the effect of the BR system or the SBR system having a low styrene content is lost, which is not preferable. If the content of the 1,2-vinyl bond in the block component (A) is too small, the production is difficult. If the content is too large, the effects such as improvement in abrasion resistance are lost.

On the other hand, if the styrene content of the block component (B) is too large, the compatibility with NR deteriorates, and the effect of improving abrasion resistance is undesirably reduced. Similarly, when the content of the 1,2-vinyl bond in the block component (B) is too small, the effect of improving the wear resistance and the like is reduced. Many are difficult to manufacture.

The AB type block copolymer used in the present invention is a known polymer. Generally, styrene and butadiene are dissolved in an organic solvent such as hexane using an organic alkali metal compound catalyst such as butyllithium. To produce a block (A), and further adding, for example, styrene and butadiene to this block in a terminal living state, to produce a block (B). The objective block copolymer can be obtained by appropriately selecting the addition of the agent, the polymerization conditions, and the like. Incidentally, such AB block copolymer is, for example, a cyclic amine,

[0016]

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The terminal-modified block may be modified with a compound having a bond, for example, an amide compound, an imide compound, a lactam compound, or a urea compound. Thereafter, it can be produced by adding an appropriate modifier in a living state.

If necessary, the rubber composition of the present invention may contain 10 to 1 carbon black per 100 parts by weight of the rubber component.
00 parts by weight, preferably 20 to 90 parts by weight, and / or 10 to 100 parts by weight of silica, preferably 20 to 90 parts by weight can be blended. For carbon black and silica, any of those generally used in conventional rubber compositions can be used.

The rubber composition of the present invention contains sulfur, a vulcanization accelerator, an antioxidant, a filler, a softener, in addition to the polymer component and, if necessary, carbon black or a silicate filler.
Various additives generally compounded in other rubber compositions for automobile tires such as plasticizers can be compounded, and such compounds can be vulcanized by a general method. The amount of these additives may be a general amount. For example, the compounding amount of sulfur is preferably at least 1.2 parts by weight, more preferably 1.5 to 3.0 parts by weight, per 100 parts by weight. Vulcanization conditions are also in a general range.

[0020]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples. In addition, the physical property measurement in the following examples was performed by the following method.

1) Rebound resilience: measured according to the method of JIS K6301.

2) Wear Lambourn: Measured using a Lambourn abrasion tester under the indicated conditions. The values of Comparative Example 4 and Comparative Example 7 were each represented by an index as 100.

3) Constant strain fatigue life index After vulcanizing the compositions of Examples and Comparative Examples at 160 ° C. for 20 minutes, a No. 3 dumbbell specified in JIS K6301 was prepared, and a constant strain of 100% was applied to the No. 3 dumbbell. The fatigue life was measured by repeatedly applying and examining the number of breaks. Each measurement was performed at n = 6, and a 50% survival probability by a normal probability distribution was obtained from each number of breaks. The result is Comparative Example 7.
The value was expressed by an index with the value of 100 as 100. Larger numbers indicate longer fatigue life.

4) Trauma resistance index The compositions of Examples and Comparative Examples were vulcanized at 160 ° C. for 20 minutes to prepare a vulcanizate sample having a thickness of about 6 cm. From the height of 2kg with a load of 2kg. The depth at which the needle touched the sample was measured. Each measurement was performed with n = 5, and the average value was obtained. The results were indicated by an index with the value of Comparative Example 7 being 100. The larger the number, the higher the trauma resistance (ie, the shallower the needle is).

Examples 1 to 16 and Comparative Examples 1 to 5 The components (parts by weight) shown in Tables 1 and 2 were blended.
After mixing the vulcanization accelerator and the raw material rubber and the compounding agent except sulfur for 5 minutes with a 1.7 liter Banbury mixer, the vulcanization accelerator and sulfur were added to this mixture for 4 minutes using an 8-inch test mill. The mixture was kneaded to obtain a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test pieces, subjected to various tests, and measured for physical properties. The physical properties of the obtained vulcanized product were as shown in Tables 1 and 2.

[0026]

[Table 1]

[0027]

[Table 2]

Examples 17 to 28 and Comparative Examples 6 to 9 The components (parts by weight) shown in Tables 3 and 4 were blended.
After mixing the vulcanization accelerator and the raw material rubber and compounding agent excluding sulfur with a 1.7 liter Banbury mixer for 5 minutes, the mixture is mixed with the vulcanization accelerator and sulfur with an 8-inch test kneading roll machine for 4 minutes. The mixture was kneaded to obtain a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test pieces, subjected to various tests, and measured for physical properties. The physical properties of the obtained vulcanized product were as shown in Tables 3 and 4.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

As described above, according to the present invention, the low heat build-up (the higher the rebound resilience at 60 ° C., the better) and the grip performance (the lower the rebound resilience at 0 ° C., the better the wet grip). It is possible to improve the wear resistance (the larger the wear resistance index in Tables 1 to 4 is, the better the wear resistance is), the better the wear resistance is, and the excellent the constant strain fatigue life and the trauma resistance are. In both 3 and 4, the higher the index is, the better) the rubber composition can be obtained.

For example, as shown in Tables 1 and 2, the formulations of Examples 1 to 12 according to the present invention (NR / SBR = 50
Comparative Example 4)
As is clear from comparison with (NR / SBR = 50/50), in the examples of the present invention, the repellency (0 ° C. and 60 ° C.) is equal to or higher than that of the block copolymer, and the abrasion resistance can be enhanced. The same is true for Comparative Example 3 with NR / SBR = 70/30 and Examples 13 and 15 and NR / SBR = 3.
The same can be said for the results of Comparative Example 5 of 0/70 and Examples 14 and 16. In addition, in the case of the natural rubber alone of Comparative Example 1, the abrasion resistance was excellent, but the rebound resilience at 0 ° C. was poor, and the SBR
In a simple case, the resilience (0 ° C. and 60 ° C.) is good, but the abrasion resistance is poor.

On the other hand, as shown in Tables 3 and 4, as is clear from the comparison between Examples 17 to 25 according to the present invention and Comparative Examples 7 and 8, the constant strain was obtained by blending the block copolymer. An excellent composition is obtained in any of the fatigue life, the trauma resistance and the abrasion resistance. Comparative Example 9 and Example 2
From the results of Nos. 6 to 28, it is clear that even in the NR / BR blend system having a large amount of BR, a rubber composition having good constant strain fatigue life, scratch resistance and abrasion resistance can be obtained by blending the block copolymer. .

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-116438 (JP, A) JP-A-62-240347 (JP, A) JP-A-1-301743 (JP, A) JP-A-4- 255733 (JP, A) JP-A-1-146938 (JP, A) JP-A-4-45137 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L ^7/ 00-21 / 00

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein (i) natural rubber and / or polyisoprene rubber and (ii) styrene-butadiene copolymer rubber and / or polybutadiene rubber have (iii) a styrene content of 0%.
Block (A) having a content of 1,2 vinyl bonds of 5 to 40% with a content of from 30 to 30% by weight and a content of butadiene of from 100 to 70% by weight.
And a styrene content of 0 to 30% by weight and a butadiene content of 1
The block (B) has a 1,2-vinyl bond content of 70% or more at a content of 70 to 70% by weight, and has a weight ratio of (A) /
(B) is obtained by blending an AB block copolymer of 20 to 80/80 to 20, and the content of the AB block copolymer is determined by the components (i), (ii) and (iii). Is from 0.5 to 20 parts by weight per 100 parts by weight of the total amount of the rubber composition. 2. A carbon black and / or silica as a reinforcing agent, wherein the total amount of the components (i), (ii) and (iii) is 1
The rubber composition according to claim 1, further comprising 20 to 100 parts by weight per 00 parts by weight.