JPH1129660A - Rubber composition for tire - Google Patents

Abstract

(57) [Problem] To develop a rubber composition for a tire capable of improving abrasion resistance and chipping resistance while maintaining characteristics such as low fuel consumption and wet braking. SOLUTION: (1) An immiscible polymer blend system comprising at least two kinds of rubbers selected from NR, IR, BR and SBR to form two polymer phases A and B,
(2) having two or more blocks, each of which blocks a and b are incompatible with each other, block a is compatible with polymer phase A, incompatible with polymer phase B, and block b is polymer phase It is compatible with B and incompatible with the polymer phase A, and the amount of 1,4 bonds contained in the blocks a and b is 50,000 or more in terms of weight average molecular weight, and further contained in the blocks a and b. The ratio a / b of the 1,4 bond amount is 0.67
A rubber composition for a tire, comprising 0.1 to 20 parts by weight of a block copolymer comprising a monomer selected from the group consisting of isoprene, butadiene and styrene, which is from 1.50 to 1.50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition for a tire. More specifically, the present invention relates to natural rubber (N
R), polyisoprene rubber (IR), polybutadiene rubber (BR) and styrene-butadiene copolymer rubber (S
(BR) comprising two polymer phases A and B comprising an incompatible polymer blend system and a block copolymer consisting of blocks a and b having a specific relationship. The present invention relates to a rubber composition for a tire having excellent breaking characteristics such as tensile strength and abrasion resistance without changing characteristics such as low fuel consumption and wet braking performance.

[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, since rubber products such as tires include a special process of vulcanization, the molecular design of block copolymers for controlling the phase structure as performed in ordinary rubber / resin and resin / resin systems Cannot be applied as it is. Therefore, the problem of the phase separation interface of the rubber / rubber blend has not been sufficiently studied, and no solution to this problem has been found.

Hitherto, reduction of the breaking strength based on the incompatibility of a polymer blend by blending a block copolymer has not been sufficiently studied, and a polybutadiene (NR) / polybutadiene rubber (BR) blend system has B
R) and a small amount of a block copolymer of polyisoprene (IR) are described in J. Am. Apply. Polym. S
ci. , 49 (1993) and RCT. 66 (199
It is only slightly described in 3). However, the compositions of the block copolymers used in these documents have insufficient compatibility with BR, so that their performance is not satisfactory for use. In addition,
Attempts have been made to add cis-BR to the BR / SBR incompatible polymer blend system in order to improve abrasion resistance, but there is a limit to the amount of cis-BR added because wet braking performance is reduced, There was a problem in practicality.

In view of the above situation, the present inventors have previously proposed a tire tread composition containing an AB block copolymer (JP-A-7-188510 and JP-A-8-188510). 134267).

[0005]

Accordingly, the present invention eliminates the above-mentioned problems of the prior art and improves the wear resistance and chipping resistance without impairing the characteristics such as low fuel consumption and wet braking. It is an object of the present invention to provide a rubber composition that can be used.

[0006]

According to the present invention, (1)
It consists of at least two kinds of rubbers selected from natural rubber (NR), synthetic isoprene rubber (IR), polybutadiene rubber (BR) and styrene butadiene rubber (SBR), and forms two polymer phases A and B. The incompatible polymer blend system has (2) at least two blocks, each block a and b of which is incompatible with each other, and block a is compatible with polymer phase A and polymer phase B
And the block b is compatible with the polymer phase B and incompatible with the polymer phase A, and the amount of 1,4 bonds contained in the blocks a and b is 50,000 when converted to the weight average molecular weight. And a block copolymer comprising a monomer selected from isoprene, butadiene and styrene, wherein the ratio a / b of 1,4 bonds contained in the blocks a and b is 0.67 to 1.50, A rubber composition for a tire is provided which is compounded in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the total rubber component.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that the addition of an appropriate block copolymer during kneading of a phase-separated polymer blend system allows the block copolymer to act as a compatibilizing agent, thereby making the phase structure finer and improving the phase separation interface. However, if cross-linking between each block of the block copolymer and the polymer forming each matrix does not occur effectively during vulcanization, the phase structure and the reinforcement that have been refined due to deformation during vulcanization will be reduced. It has been found that the damaged interface returns to its original state, and the effect of improving the breaking strength is reduced. As a result of intensive studies on preventing such a decrease in the effect of improving the breaking strength, 1,4 contained in each block of the block copolymer was found.
It has been found that the above problem can be solved by specifying the amount of binding and the ratio so that the cross-linking reaction between each block and each matrix is performed at almost the same speed.

[0008] The rubber composition for a tire according to the present invention comprises:
(1) Two polymer phases A and B composed of at least two types of incompatible rubbers of NR, IR, BR and SBR (preferable A / B weight ratio is 5/95 to 95/5, more preferably 10/90) To 90/10) the incompatible polymer blend system has (2) at least two blocks made of a monomer selected from isoprene, butadiene, and styrene, and each block a and b is incompatible with each other, a is compatible with the polymer phase A and is incompatible with the polymer phase B, and the block b is compatible with the polymer phase B and is incompatible with the polymer phase A, and the 1,4 contained in the blocks a and b. A block copolymer having a bond amount of 50,000 or more in terms of weight average molecular weight, and a ratio a / b of 1,4 bond amounts (in terms of molecular weight) contained in blocks a and b of 0.67 to 1.50. 0.1 to 20 parts by weight with respect to 100 parts by weight of the total rubber component mer containing a block copolymer, preferably by blending 0.3 to 18 parts by weight.

The blocks a and b of the block copolymer used in the present invention cannot sufficiently enter the matrix phases A and B unless the blocks a and b are incompatible with each other, so that the desired effect of improving the fracture characteristics can be obtained. Absent. Further, in the present invention, the block a must be compatible with the polymer phase A and incompatible with the polymer phase B, and the block b must be compatible with the polymer phase B and incompatible with the polymer phase A. If this relationship is not maintained, the block copolymer cannot coordinate at the A and B phase separation interfaces, so that the phase separation interface is not reinforced and a sufficient effect of improving the breaking strength cannot be obtained, which is not preferable.

The amount of 1,4 bonds contained in the blocks a and b of the block copolymer used in the present invention is 50,000 or more, preferably 5.5, in terms of weight average molecular weight.
If it is not more than 10,000, sufficient co-crosslinking property with the polymer component forming the matrix cannot be obtained, so that the phase separation interface cannot be sufficiently reinforced as in the case described above, and the desired effect of improving the breaking strength cannot be obtained. Not preferred.

The ratio a / b of the 1,4 bond content (in terms of molecular weight) contained in the blocks a and b of the block copolymer used in the present invention is 0.67 to 1.50, preferably 0.70 to 1.40. It is. If the ratio a / b deviates from this range, each block a of the block copolymer during the vulcanization reaction
And b and the progress of the co-crosslinking of each of the matrix phases A and B occur, and the phase separation structure refined in the kneading process reaggregates and enlarges, so that the desired effect of improving the breaking strength is obtained. Not so desirable.

The calculation method of the 1,4 bond amount (in terms of molecular weight) is as follows. The styrene content (% by weight) of the block measured in the block copolymer polymerization process is represented by St, and the content of vinyl polymerized unit in the conjugated diene polymer portion is represented by St. Amount (total amount of 1,2 vinyl content (mol%) and 3,4 vinyl content (mol%))
Is Vn, and the weight average molecular weight of the entire block copolymer is M
Assuming that the weight ratio of w and block i is Wi, the 1,4 bond amount (in terms of molecular weight) of block i is calculated by the following equation.

[0013]

(Equation 1)

The method for producing the block copolymer (i) of the present invention is not particularly limited. For example, an organic active metal is used as an initiator in a hydrocarbon solvent, and isoprene, butadiene, styrene, etc. Can be carried out by a method of polymerizing and producing the above monomer. Examples of the organic active metal include an organic active metal capable of anion polymerization such as an organic alkali metal compound, an organic alkaline earth metal compound, and an organic lanthanoid-based rare earth metal compound. Among these, organic alkali metal compounds are particularly preferred.

According to the present invention, 0.1 to 20 parts by weight, preferably 0.3 to 18 parts by weight of the block copolymer is blended with respect to 100 parts by weight of the total amount of the incompatible polymer blend and the block copolymer. If the blending amount of the block copolymer exceeds 20 parts by weight, the viscoelastic properties of the block copolymer are affected, and the balance between wet braking performance and rolling resistance originally intended is changed, which is not preferable.

The immiscible polymer blend comprising polymer phases A and B used in the present invention is NR, IR, BR and SB.
There is no particular limitation as long as two or more types are selected from R to form the two incompatible polymer phases A and B. The block copolymer comprising blocks a and b used in the present invention can be any polymer satisfying the above conditions, for example, BR block, SBR block, IR block, SIR (styrene isoprene rubber) block, BI block
R (butadiene isoprene) block, SBIR (styrene butadiene isoprene) block and the like can be used in appropriate combination.

Specific examples of the combination of such an incompatible polymer and a block copolymer are as follows. The polymer phase A is composed of polybutadiene (BR) having a cis content of 80% by weight or more, preferably 85 to 100% by weight, and the polymer phase B is composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). a and b have the following composition: a: St = 0 to 35% by weight (preferably 5 to 35% by weight), Vn = 5 to 80% by mole (preferably 8 to 80% by mole), and Vn ≦ 2St + 30 b: A composition which is SBR or BR having St = 0 to 30% by weight (preferably 5 to 30% by weight), and Vn> 2St + 30, wherein St represents a styrene content and Vn represents a vinyl content of a butadiene portion.

The polymer phase A is composed of styrene butadiene rubber (SBR) and / or polybutadiene rubber (BR), the polymer phase B is composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). A rubber composition, wherein the block b is a polyisoprene (IR) having the following composition: a: St = 0 to 50% by weight (preferably 5 to 50% by weight), Vn = 5 to 70% by mole (preferably 8 to 70% by weight), and Vn ≦ 2St + 30 b: 1,4 bond amount ≧ 70% by weight % (Preferably 72 to 10
(In the formula, St indicates a styrene content, and Vn indicates a vinyl content.)

The polymer phase A is composed of polybutadiene (BR) having a cis content of 80% by weight or more (preferably 85 to 100% by weight), and the polymer phase B is composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). Block a of the copolymer is SBR or BR having the following composition, and block b is polyisoprene (I
A composition which is R). a: St = 0 to 35% by weight (preferably 5 to 35% by weight), Vn = 5 to 80% by mole (preferably 8 to 80% by mole), and Vn ≦ 2St + 30 b: 1,4 bond amount ≧ 70% by weight % (Preferably 72 to 10
(In the formula, St indicates a styrene content, and Vn indicates a vinyl content.)

The polymer phase A is a polybutadiene rubber (BR) having a cis content of 80% by weight or more, and the polymer phase B is St = 5.
-60% by weight and Vn = 5-35 mol%, St = 5-6
0% by weight and Vn = 65-85 mol%, and St = 35
Styrene butadiene rubber (SBR) or polybutadiene rubber (BR), wherein at least one styrene butadiene rubber (SBR) selected from the group consisting of styrene butadiene rubber (SBR) selected from the group consisting of: ) And block b is a styrene butadiene rubber (SBR) having the following composition: a: St = 0 to 35% by weight, Vn = 5 to 80% by mole b: St = 5 to 60% by weight and Vn = 5 to 35 mol%,
St = 5-60% by weight and Vn = 65-85 mol%, and St = 35-60% by weight and Vn = 35-65 mol%
(Wherein St = styrene content, and Vn represents the vinyl content of the butadiene portion.)

The rubber composition for a tire of the present invention contains 30 parts by weight or more, preferably 40 to 150 parts by weight, of a generally used reinforcing filler such as carbon black and / or silica with respect to 100 parts by weight of the rubber component. Mix parts. For carbon black and silica, any of those generally used in conventional rubber compositions can be used. In addition, a softener, an antioxidant, a vulcanization aid, a wax, a resin, and a vulcanization-based compounding agent which are usually used in the rubber industry can be used as appropriate. Further, foaming agents, low-moisture plasticizers, short fibers, and the like conventionally used for studless tires and the like can be used.

In blending the rubber composition for a tire according to the present invention, first, a rubber (matrix rubber and block copolymer) and other compounding agents except for a reinforcing filler and a vulcanizing compound are mixed by a conventional method. And then blending the vulcanizing compounding agent. Of course,
It goes without saying that, even if some of these components are separately added, they will fall within the technical scope of the present invention as long as the object of the present invention is not impaired. Also, the blending means can be conventional.

The compound relating to the rubber composition for a tire of the present invention can be vulcanized by a general method. The compounding amount of the above-mentioned additives can also be a general amount. For example, the amount of sulfur is preferably 0.5 parts by weight or more, more preferably 1.0 to 5.0 parts by weight, per 100 parts by weight of the rubber component. The vulcanization conditions of the rubber composition for a tire of the present invention may be general conditions.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, Standard Examples and Comparative Examples, but it is needless to say 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 property (tan δ): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, static strain = 10%,
It was measured at dynamic strain = ± 2% and frequency = 20 Hz (sample width 5 mm, temperature 0 ° C. and 60 ° C.). 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 were shown as an index (wear resistance index) with the formulation of the standard example being 100. Larger numbers indicate better wear resistance. The tensile test was performed according to JIS K6301.

Incompatible (whether or not a polymer phase is formed)
Determination 1) incompatible polymer phase A and B of the polymer blends by vulcanizing the polymer blend or), after creating the ultra-thin section specimen by freezing, air for about 15 hours at room temperature osmium tetroxide benzene solution Phase stain. By observing this with a transmission electron microscope at about 5,000 to 10,000 times, the presence or absence of a phase separation structure is observed. 2) The incompatibility of the blocks a and b of the block copolymer can be determined by observing the block copolymer in an unvulcanized state at a magnification of about 60,000 using a transmission electron microscope after preparing a sample similar to the above. Observe. 3) The incompatibility between each block of the block copolymer and each polymer phase of the polymer blend is determined by separately polymerizing and forming a polymer corresponding to the polymer constituting each block, kneading and vulcanizing with each matrix polymer. A sample for electron microscope observation was prepared in the same manner as in
Observe at 10,000 times to observe the presence or absence of the phase separation structure. In addition, the determination of compatibility or incompatibility is based on a method of determining whether or not the peak is bimodal based on the temperature dispersion curve of tan δ, and whether or not a plurality of glass transition temperatures of the blended polymer are observed by DSC measurement. A judgment method may be used, and when the phase separation structure reaches several tens of microns, it can be judged by an optical microscope. Among these methods, the direct observation using an electron microscope is the method having the highest sensitivity, but the measurement is troublesome.

Standard Examples 1 to 15, Examples 1 to 22 and Comparison
Examples 1 to 21 Using the block copolymers 1 to 16 having the properties shown in Table I, the components of the formulations (parts by weight) in Tables II to VI were mixed for 5 minutes in a 1.7-liter Banbury mixer by the following mixing method. Thereafter, the mixture was kneaded with a vulcanization accelerator and sulfur for 4 minutes using an 8-inch test kneading roll machine 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 vulcanizates were as shown in Tables II to VI.

Mixing method All of the examples and comparative examples were mixed according to the following mixing specifications.・ Rotor rotation speed: 60 rpm ・ Temperature adjustment: 50 ° C. ・ Input specification: 0 ′: rubber component (matrix rubber, block copolymer) 1 ′: half of carbon black, zinc white, stearic acid 2′30 ″: half of carbon black, aging Inhibitor, wax, aroma oil 3'30 "... ram up and down (ram part, clean) 4'00" ... release

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

[Table 7]

[0036]

[Table 8]

[0037]

[Table 9]

[0038]

[Table 10]

[0039]

As described above, according to the present invention, a rubber composition for a tire having excellent tensile properties, viscoelastic properties and abrasion resistance can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masao Nakamura 1-2-1 Nightlight, Kawasaki-ku, Kawasaki-shi, Kanagawa Japan Zeon Co., Ltd. (72) Inventor Takeshi Karatoshi Takeru, Kawasaki-ku, Kawasaki-shi, Kanagawa 1-2-1 Inside the Zeon Corporation General Development Center

Claims (6)

[Claims] 1. (1) At least two kinds of rubber selected from natural rubber (NR), synthetic isoprene rubber (IR), polybutadiene rubber (BR) and styrene butadiene rubber (SBR), and two polymer phases The incompatible polymer blend system forming A and B has (2) at least two blocks, each block a and b
Are incompatible with each other, block a is compatible with polymer phase A and incompatible with polymer phase B, block b is compatible with polymer phase B and incompatible with polymer phase A, and block a And the amount of 1,4 bonds contained in b and b is 50,000 or more when converted into a weight average molecular weight, and
And the ratio a / b of the amount of 1,4 bonds contained in b is 0.67 to
1.50 isoprene, butadiene and a block copolymer comprising a monomer selected from the styrene group,
A rubber composition for a tire, comprising 0.1 to 20 parts by weight per 100 parts by weight of all rubber components including a block copolymer. 2. The polymer phase A is composed of polybutadiene (BR) having a cis content of 80% by weight or more, and the polymer phase B is composed of at least one of natural rubber (NR) and synthetic isoprene rubber (IR). b has the following composition: a: (St) = 0 to 35% by weight, (Vn) = 5 to 80% by mole, and Vn ≦ 2St + 30 b: St = 0 to 30% by weight, Vn> 2St + 30 The rubber composition for a tire according to claim 1, wherein SBR or BR has a styrene content and Vn represents a vinyl content of a butadiene portion. 3. The polymer phase A comprises at least one of styrene butadiene rubber (SBR) and polybutadiene rubber (BR), and the polymer phase B comprises at least one of natural rubber (NR) and synthetic isoprene rubber (IR). The block a has the following composition:
BR or BR, and the block b is a polyisoprene (IR) having the following composition: a: St = 0 to 50% by weight, Vn = 5 to 70 mol%, and Vn ≦ 2St + 30 b: cis 1,4 bond amount The rubber composition for a tire according to claim 1, wherein ≧ 70% by weight (where St represents a styrene content and Vn represents a vinyl content of a butadiene portion). 4. The polymer phase A is composed of polybutadiene (BR) having a cis content of 80% by weight or more, the polymer phase B is composed of at least one of natural rubber (NR) and synthetic isoprene rubber (IR). A: St = 0 to 35% by weight, Vn = 5 to 80% by mole, and Vn ≦ 2St + 30 b: cis 1 The block b is a polyisoprene (IR) having the following composition. The rubber composition for a tire according to claim 1, wherein the binding amount is 70% by weight or more, wherein St represents a styrene content and Vn represents a vinyl content of a butadiene portion. 5. The polymer phase A is a polybutadiene rubber (BR) having a cis content of 80% by weight or more, and the polymer phase B is St =
5-60% by weight, Vn = 5-35 mol%, St = 5-
60% by weight and Vn = 65-85 mol%, and St = 3
At least one styrene-butadiene rubber (SBR) selected from 5 to 60% by weight and Vn = 35 to 65 mol%
Wherein the block a of the block copolymer is styrene butadiene rubber (SBR) or polybutadiene rubber (BR) having the following composition, and the block b is styrene butadiene rubber (SBR) having the following composition: a: St = 0 to 35% by weight, Vn = 5 to 80% by mole b: St = 5 to 60% by weight and Vn = 5 to 35% by mole,
St = 5-60% by weight and Vn = 65-85 mol%, and St = 35-60% by weight and Vn = 35-65 mol%
The rubber composition for a tire according to claim 1, wherein at least one selected from the group consisting of: wherein St = styrene content, and Vn represents a vinyl content of a butadiene portion. 6. An iodine adsorption amount of 65 g / 100 parts by weight of the polymer phase A in 5 to 70 parts by weight, the polymer phase B in 30 to 95 parts by weight, and the total rubber content including the block copolymer.
above kg, tire rubber composition according to claim 5 obtained by blending 40 to 150 parts by DBP oil absorption of 70cm ^3/100 g or more carbon black.