JP3349854B2 - 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 rubber comprising natural rubber (NR) and / or polyisoprene rubber (IR) and high cis polybutadiene (BR), butadiene or butadiene and styrene. And an AB block copolymer comprising isoprene, and can improve abrasion resistance without changing viscoelastic properties and the like, for example, a TBS cap,
The present invention relates to a rubber composition useful for a side tread, a cap tread for a studless tire, and the like.

[0002]

2. Description of the Related Art In recent years, there has been a demand for improvements in various properties of rubber compositions for tires of automobiles and the like. However, when these polymers are incompatible with each other, a phase separation interface exists. In many cases, this interface is considered to be a starting point of fracture, which has an adverse effect on tensile strength, tear strength, wear resistance, and the like. However, conventionally, the problem of the phase separation interface of rubber / rubber blend in rubber products such as tires has not been sufficiently studied, and no solution to this problem has been found.

Hitherto, reduction of fracture characteristics due to incompatibility of a polymer blend by blending a block polymer has not been sufficiently studied, and a polybutadiene (NR) / polybutadiene rubber (BR) blend system has BR)
A small amount of a block copolymer of polyisoprene (IR) and polyisoprene (IR) can be blended. Apply. Polym. Sc
i. , 49 (1993) and RCT. 66 (1993)
It is only described in. However, in these documents, SBR having a greater industrial importance and a high degree of freedom are considered only by limitedly examining the above block polymers.
Unified examination up to polymers with blocks,
No views are given.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention eliminates the above-mentioned problems of the prior art and provides a rubber composition capable of enhancing abrasion resistance without impairing properties such as viscoelastic properties. The purpose is to do.

[0005]

According to the present invention, (i)
Natural rubber and / or polyisoprene rubber, (ii) high cis polybutadiene and (iii) (a) styrene content (S
t) A 1,2-vinyl bond content (Vn) of 5 to 80% at 35% by weight or less and a butadiene content (Bd) of 65% by weight or more.
Poly (styrene-butadiene) block (A) or (b) 1,2- which satisfies the relationship Vn ≦ 2St + 30
It comprises a polybutadiene block (A) having a vinyl bond content (Vn) of more than 10% and 30% or less, and a polyisoprene block (B) having a cis content of 70% by weight or more. An AB block copolymer of 20 to 80/80 to 20 is blended, and the content of the AB block copolymer is 1 in total of the components (i), (ii) and (iii).
A rubber composition is provided which is 2 to 20 parts by weight per 00 parts by weight.

[0006]

According to the present invention, grip performance is obtained by blending (iii) a specific block copolymer (AB) with a blend system of (i) NR and / or IR and (ii) high cis BR. In addition, the wear resistance can be improved without lowering the viscoelastic properties such as low fuel consumption performance, and the fatigue resistance and trauma resistance can be further improved.

[0007] N compounded in the rubber composition according to the present invention
R, IR and high cis BR can be any polymer conventionally used as a rubber component in various rubber applications, and the NR / IR blend ratio and (i) NR
And / or the blend ratio of IR / (ii) high cis BR can be selected according to the use of the rubber composition. Such selection can be appropriately made by those skilled in the art, but preferably the NR / IR ratio can be set to 100/0 to 50/50, and (i) NR and / or IR / (ii) high cis BR
The ratio is preferably 20-95 / 80-5 (parts by weight), more preferably 25-90 / 75-10 (parts by weight).
The cis content of the high cis BR used in the present invention is preferably 80% by weight or more, more preferably 90 to 100% by weight.
It is.

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 amount of the block copolymer is too small, the desired improvement effect cannot be obtained, and if the amount is too large, the viscoelastic properties of the block polymer itself appear. This is not preferable because viscoelastic properties such as grip performance and fuel economy performance are lost. From this viewpoint, the AB block copolymer used in the present invention is composed of all polymer components (including the AB block copolymer) 10
The AB block copolymer is 2-2 to 0 parts by weight.
0 parts by weight, preferably 5 to 18 parts by weight.

The AB block copolymer used in the present invention comprises styrene (St) and butadiene (Bd) copolymer or butadiene (Bd) polymer, and isoprene,
Styrene content (St) of block components A and B, 1,2
-Vinyl bond (Vn) and cis isoprene content and A
The weight ratio (A) / (B) of the component and the component B is as follows.

Block A (a) Styrene content 35% by weight or less, preferably 1-3
5% by weight, more preferably 5 to 30% by weight (the remainder is butadiene content), 1,2-vinyl bond content (Vn) of the butadiene portion: 5 to 80% by mole, preferably 10 to 70% by mole and Vn ≦ 2St + 30 (St: styrene content)
(B) Polybutadiene having a 1,2-vinyl bond content of more than 10 mol% and 80 mol% or less, preferably 12 to 30 mol%

Polyisoprene having a block B cis content of 70% by weight or more, preferably 75% by weight or more

(A) / (B) = 20-80 / 80-20
(Parts by weight), preferably 30 to 70/70 to 30 (parts by weight)

If the styrene content of the block components (A) and (a) is too high, the desired effect cannot be obtained because the styrene content is incompatible with the high cis BR, so that the 1,2-vinyl bond content is out of the above range. In this case, the compatibility with the high cis BR becomes poor, so that the desired effect cannot be obtained. A
If the blending amount of the B-type block copolymer is less than 2 parts by weight, the function as a compatibilizer is not sufficient, and the physical properties such as abrasion resistance are not improved. It is not preferable because its own viscoelastic properties appear and affect other physical properties. If the (A) / (B) ratio is out of the above range, the desired effect cannot be obtained, probably because entanglement with the matrix rubber (NR, BR) is reduced or co-crosslinking property is reduced.

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. Or butadiene is polymerized to produce a block (A), and isoprene is further added to this block in a living terminal state to produce a block (B). The desired block copolymer can be obtained by appropriately selecting the addition of the agent and the polymerization conditions. Further, the AB block polymers may be coupled with, for example, tin tetrachloride, silicon tetrachloride, or the like. Alternatively, it can also be produced by producing blocks A and B in accordance with a conventional method, and coupling them with a coupling agent such as tin tetrachloride or silicon tetrachloride. . Incidentally, such AB block copolymer is, for example, a cyclic amine,

[0015]

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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.

The molecular weight of the AB type block copolymer blended in the present invention is not particularly limited, but the weight average molecular weight may be reduced in consideration of the entanglement with the matrix rubber (NR, high cis BR) or co-crosslinkability. It is preferably at least 30,000, more preferably from 50,000 to 800,000.

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.

Viscoelastic properties: Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, static strain = 10%, dynamic strain = ±
2%, frequency = 20 Hz (sample width 5 mm, -20
℃, 0 ℃, 60 ℃)

Abrasion resistance test: Measured using a Lambourn abrasion tester under the conditions of a slip ratio of 25% and a load of 5 kg. The results are shown as an index (wear resistance index) with the rubber of the standard example of Comparative Example 3 being 100, and the larger the number, the better the wear resistance.

Examples 1 to 10 and Comparative Examples 1 to 9 The components (parts by weight) shown in Table I were blended, and a vulcanization accelerator, a raw rubber excluding sulfur, and a compounding agent were mixed in 1.7 liter Bamba. After mixing with a remixer for 5 minutes, the mixture was mixed with a vulcanization accelerator and sulfur with an 8-inch test mill roll.
After kneading for a minute, a rubber composition was obtained. 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. Physical properties of the obtained vulcanized product were as shown in Table I.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

As described above, according to the present invention, the grip performance (the higher the tan δ at 0 ° C., the better the wet grip), the low fuel consumption performance (the lower the tan δ at 60 ° C., the better), and the low temperature Flexibility (-20 ° C
A rubber composition having excellent abrasion resistance (the larger the abrasion resistance index in Table I is better) without lowering the E ′ in Table 1, the better (in Table I, the higher the index is, the better). Obtainable.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 53:02) (56) References JP-A-57-200439 (JP, A) JP-A-64-81811 (JP, A) JP-A-58-122945 (JP, A) JP-A-4-45137 (JP, A) JP-A-1-146939 (JP, A) JP-A-7-188510 (JP, A) JP-A-1-301734 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L ^7/ 00-21/00

Claims (2)

(57) [Claims] (1) natural rubber and / or polyisoprene rubber, (ii) high cis polybutadiene and (iii)
(A) Poly (styrene) having a styrene content (St) of 35% by weight or less, a butadiene content (Bd) of 65% by weight or more, a 1,2-vinyl bond content (Vn) of 5 to 80%, and satisfying a relationship of Vn ≦ 2St + 30 -Butadiene) block (A) or (b) 1,2-vinyl bond content (Vn) is 1
A polybutadiene block (A) of more than 0% and 30% or less;
It comprises a polyisoprene block (B) having a cis content of 70% by weight or more, and (A) / (B) is 20 to 8 in weight ratio.
A / B type block copolymer of 0/80 to 20 is blended, and the content of the AB type block copolymer is the component (i),
A rubber composition which is 2 to 20 parts by weight per 100 parts by weight of the total of (ii) and (iii). 2. An AB type block copolymer having a molecular weight of 3
The rubber composition according to claim 1, which is not less than 000.