JP2001247722A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition having an increased hysteresis loss at a temp. of 0-40 deg.C with regard to a rubber composition containing a diene- based synthetic rubber and besides, excellent in strength and abrasion resistance. SOLUTION: The invention discloses a rubber composition comprising (i) 50-95 wt.% of at least one kind of a rubber elastomer, (ii) 5-50 wt.% of at least one kind of a triblock elastomer having over 50,000 of weight-average molecular weight, comprising a terminal polystyrene hard segment A and a mid isobutene-based elastomer soft segment B and having a general arrangement of A-B-A, and (iii) a reinforcing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having improved hysteresis loss at 0.degree. C. to 40.degree. C. without lowering toughness, and more particularly to a rubber composition for tire tread while improving abrasion resistance. The present invention relates to a rubber composition which maintains a high wet road surface gripping property required for a rubber composition and a rubber composition having a vibration damping performance required in the field of construction and capable of increasing rigidity.

[0002]

2. Description of the Related Art JP-A-11-199714 discloses that
A high damping rubber composition containing a styrene-isoprene-styrene triblock polymer is described. Japanese Patent Application Laid-Open No. 10-101847 discloses styrene-
A silica reinforced rubber composition containing a diene-styrene triblock polymer is described. However, such a composition has problems that a sufficient hysteresis loss cannot be obtained at room temperature and the strength is low.

JP-A-11-315171 discloses a rubber composition containing a copolymer obtained by cationic copolymerization using a Lewis acid catalyst as an initiator and a pneumatic tire using the same. ing. However, this method is used as a softener, and when used as a rubber substitute, sufficient strength cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention provides a tan δ of 0 to 40 ° C., which is a measure of hysteresis loss, which can be advantageously used as a high damping rubber composition for a tread of a pneumatic rubber tire or a building material. An object of the present invention is to provide a rubber composition containing natural rubber and / or a diene-based synthetic rubber, which is high in strength and abrasion resistance.

[0005]

According to the present invention, (i)
50-95 parts by weight of at least one rubber elastomer (ii) having a weight average molecular weight of more than 50,000 and comprising a terminal polystyrene hard segment A and an internal isobutene elastomer / soft segment B
There is provided a rubber composition comprising 5 to 50 parts by weight of at least one triblock elastomer having a general configuration of B-A and (iii) a reinforcing agent.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted studies to increase the tan δ of 0 to 40 ° C. and obtain excellent toughness of a rubber composition containing a rubber elastomer such as natural rubber and / or a diene-based synthetic rubber. As a result, a rubber composition comprising a rubber elastomer containing a diene rubber and an ABA type thermoplastic triblock elastomer such as a diene styrene-isobutene-styrene block copolymer and a conventional rubber compounding agent are added. And achieved the present invention.

The rubber elastomer used as the component (i) in the composition of the present invention can be any rubber conventionally used generally in the field of tires and construction. For example, natural rubber (NR) , Polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR),
Acrylonitrile-butadiene copolymer rubber (NB
R), diene rubbers such as butyl rubber (IIR) can be used alone or as an arbitrary blend. Of these, butyl rubber has a small temperature dependence of tan δ,
It is preferable because a high hysteresis loss can be obtained at room temperature.

In the ABA triblock used as component (ii) in the present invention, the segment B is 50 to 90% by weight of the triblock elastomer, and A has a weight average molecular weight of more than 2500, more preferably. Is 300
0-30000 polystyrene hard blocks,
B is an isobutene elastomer having a weight average molecular weight of more than 25,000, more preferably 26,000 to 108,000, more than 50,000 in total, and more preferably 5 to 5
2000 to 120,000, specifically, for example, the structure: St-IB-St (where St is a styrene block,
B represents an isobutene block).

Such a triblock elastomer is
For example, as described in JP-A-11-349648, it is a known block polymer which can be produced by polymerization using a Lewis acid catalyst as an initiator.

In the rubber composition according to the present invention, the compounding ratio of the rubber elastomer of the component (i) and the ABA triblock elastomer of the component (ii) is expressed by weight ratio:
(I): (ii) = 50-95: 5-50 (total amount 10
0), preferably (i) :( ii) = 70-90: 10
30 (total amount 100). If the amount of component (i) is too small, sufficient elongation and strength cannot be obtained as a rubbery composition, which is not preferable. Conversely, if the amount is too large, a desired high hysteresis loss cannot be obtained at room temperature.

Examples of the reinforcing agent to be blended as the component (ii) in the rubber composition of the present invention include carbon black, silica and the like, and the rubber 10 of the components (i) and (ii) can be used.
40 parts by weight or more, preferably 50 to 1 part by weight with respect to 0 parts by weight.
20 parts by weight are blended. If the amount is too small, the reinforcing properties required for the rubber composition cannot be obtained, which is not preferable.

In the rubber composition according to the present invention, in addition to the above-mentioned essential components, tires such as a softener such as various oils, a vulcanizing or crosslinking agent, a vulcanizing or crosslinking accelerator, an antioxidant, and a plasticizer. And other additives commonly used for general rubbers can be compounded, and such additives can be used in usual amounts as long as the object of the present invention is not impaired.

When the rubber composition of the present invention is obtained, it is preferred that ABA triblock elastomer (ii) and 30 to 70% by weight of the filler are mixed in advance and then mixed with other components. By mixing in advance, AB-
The fraction of the filler in the triblock elastomer A (ii) is promoted, and a high hysteresis loss with high reinforcement is obtained.

[0014]

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.

Preparation of Samples of Standard Example 1, Comparative Example 1 and Examples 1 to 4 In the composition (parts by weight) shown in Table I, the components other than the vulcanization accelerator and sulfur were mixed in a 1.8-liter closed mixer. ~ 5
Kneaded for about 1 minute and released when the temperature reaches 165 ± 5 ° C.
The mixture was kneaded at a temperature of 3 ° C. for 3 minutes to obtain a rubber composition. Next, the composition was placed in a 15 × 15 × 0.2 cm mold at 160 ° C. for 20 minutes.
The sample was vulcanized for 5 minutes to prepare a target test piece (rubber sheet). Physical properties were evaluated as follows. The results are shown in Table I.

Evaluation method of physical properties Scorch time (min): 12 based on JIS-K6300
Time at which Mooney viscosity increases by 5 points at 5 ° C. JIS hardness (20 ° C): measured at room temperature based on JIS-K6253. Tensile stress at 300% elongation (MPa): JIS-K6253
Measured with dumbbell shape No. 3 based on tan δ (0 ° C., 20 ° C. and 40 ° C.): Measured at each temperature at an amplitude of ± 2%, a frequency of 20 Hz, and a static strain of 10% using a viscoelastic spectrometer manufactured by Toyo Seiki Seisaku-sho, Ltd. Abrasion resistance: Loss on wear was measured using a Lambourn abrasion tester under the conditions of a load of 5 kg, a slip ratio of 25%, a time of 4 minutes and room temperature. Larger numbers indicate better wear resistance.

[0017]

[Table 1]

Table I Footnotes SIBS: Styrene-isobutene-styrene / triblock elastomer manufactured by Kanegafuchi Chemical Co., Ltd. (weight average molecular weight 1)
00,000 isobutylene content of 70 wt%) SIBS masterbatch Component Parts by weight SIBS 100 N339 Carbon Black 50

Brominated butyl rubber: POL manufactured by Bayer AG
YSAR BROMOBUTYLX2 SBR 1502: Nippon Zeon styrene butadiene copolymer (Nipol 1502) N339: Tokai Carbon Carbon Black Seast KH

Anti-aging agent (6C): N-phenyl-N '
-(1,3-dimethylbutyl) -p-phenylenediamine powdered sulfur: 5% oil-extended powdered sulfur Vulcanization accelerator (CBS): N-cyclohexyl-2-benzothiazole sulfenamide

[0021]

As described below, diene-based synthetic rubber (SB)
When a styrene-isobutene-styrene block copolymer is blended with R), a rubber having high tan δ, high wear resistance and high hardness can be obtained, and the wear resistance can be improved by using the rubber together with butyl rubber. .

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 53/02 C08L 53/02 101/12 101/12 // B60C 1/00 B60C 1/00 A F term (reference) 4F070 AA05 AA06 AA08 AA12 AB08 AB22 AC04 AC23 AE01 FA04 FA17 FB03 FB06 FB07 FC03 4J002 AC01W AC02W AC06W AC07W AC08W BB18W BC05W BG10W BP01X DA036 DJ016 FD016 GN01

Claims (4)

[Claims] (1) 50 to 95 parts by weight of at least one rubber elastomer (ii) a weight average molecular weight of 50,000
5 to 50 parts by weight of at least one triblock elastomer having a general configuration of ABA, comprising a terminal polystyrene hard segment A and an internal isobutene-based elastomer / soft segment B, and (iii) A rubber composition comprising a reinforcing agent. 2. The rubber composition according to claim 1, wherein the segment B of the ABA triblock elastomer (ii) accounts for 50 to 90% by weight of the triblock elastomer. 3. The rubber composition according to claim 1, wherein the rubber elastomer (i) contains butyl rubber. 4. A method according to claim 1, wherein the ABA triblock elastomer (ii) and 30 to 70% by weight of the filler are mixed in advance in an internal mixer and then mixed with other components. 4. The rubber composition according to 3.