JP2002012708A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which provides low fuel consumption and exhibits a marked improvement in workability, without detriment to physical properties such as tensile modulus and hardness at a 300% elongation and a pneumatic tire produced by using the same. SOLUTION: This rubber composition is prepared by compounding a rubber component comprising at least one rubber selected from among natural and synthetic rubbers with a polyolefin having a Vicat softening point (under 1 kg load) of 110 deg.C or lower and a Mooney viscosity (ML1+4, at 100 deg.C) of 15 or lower, a polyolefin having a heat of crystal fusion (with a differential scanning calorimeter) of 20 J/g or lower, or a polyolefin having a ring-and-ball softening pint of 100-140 deg.C. The pneumatic tire is produced by using the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition and a pneumatic tire using the same. For more information,
According to the present invention, the workability of the unvulcanized rubber composition is remarkably improved by blending a specific polyolefin having low crystallinity into the rubber component, while maintaining other good performances such as low heat generation (low fuel consumption). The present invention relates to an improved rubber composition and a pneumatic tire using the rubber composition.

[0002]

2. Description of the Related Art In recent years, demands for lower fuel consumption of automobiles have become more severe with social demands for energy saving and increased interest in environmental issues. In order to respond to such a demand, a reduction in rolling resistance has also been required for tire performance. As a method of reducing the rolling resistance of a tire, although a method by optimizing the tire structure has been studied, the most general method is to use a rubber composition having a lower heat generation as a tread rubber layer. ing. It is known that hardening the tread rubber is advantageous for obtaining the rubber composition having a low heat build-up because it reduces energy loss.
However, in general, when the rubber composition is hardened, the productivity in the extrusion of the unvulcanized rubber is deteriorated, and the workability is adversely affected, such as the shrinkage of the extruded sheet increases.

[0003] On the other hand, in recent years, with increasing interest in the safety of automobiles, there has been an increasing demand for not only low fuel consumption performance but also performance on wet road surfaces (hereinafter referred to as wet performance), particularly braking performance. For this reason, the performance requirements for the rubber composition of the tire tread are not limited to simply reducing the rolling resistance, and those that highly satisfy both wet performance and low fuel consumption performance are required. As a method of obtaining such a rubber composition which simultaneously provides good fuel economy and good wet performance to a tire, a hydrated silica is used as a reinforcing filler instead of carbon black which has been generally used so far. A method using silica such as an acid has already been performed. However, even in this case, if the rubber is hardened to obtain a high level of low fuel consumption performance, on the other hand, workability is deteriorated.

[0004] In order to improve the above workability, several means can be considered from the viewpoint of rubber compounding. For example, if the amount of process oil is increased, workability is improved.
At 0% elongation, the tensile stress decreases and the fuel economy deteriorates. Further, when compounding liquid isoprene, liquid polybutadiene, or the like, the vulcanizing agent is consumed extra, and weighing at the time of compounding becomes difficult due to the viscous material. When liquid polybutene is blended, it is easy to bleed out due to its low molecular weight, and weighing is difficult. In any case, when a liquid polymer is used, improvement in fuel economy cannot be achieved. When blending resins such as petroleum resin and coumarone indene resin,
Since the glass transition temperature of the resin is high, the fuel economy may be deteriorated, and the tackiness may be increased, resulting in poor workability. Further, recently, attempts have been made to blend olefins such as polyethylene into rubber. However, conventionally used polyethylene has a high degree of crystallinity and a large molecular weight, so that tensile stress and hardness at 300% elongation are low. There was no tendency to increase the Mooney viscosity and no improvement in workability was observed because the Mooney viscosity did not decrease. For this reason, it has been difficult to obtain a rubber in which both the fuel efficiency and the workability are improved at a high level by any of the above conventional methods.

[0005]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is to maintain good fuel economy and to achieve a 300%
An object of the present invention is to provide a rubber composition having significantly improved workability without adversely affecting other rubber properties such as tensile stress and hardness during elongation, and a pneumatic tire using the rubber composition. Things.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, a rubber obtained by compounding a non-crystalline or low-crystalline specific polyolefin with a rubber component. It has been found that the composition can be adapted for that purpose. That is, the present invention provides a rubber component comprising at least one of natural rubber and synthetic rubber, wherein the Vicat softening temperature measured under a load of 1 kg is 110 ° C or less,
And a Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of 15
The present invention provides a rubber composition containing the following polyolefin. The present invention also provides a rubber composition characterized in that a rubber component comprising at least one of natural rubber and synthetic rubber is mixed with a polyolefin having a heat of crystal fusion of 20 J / g or less as measured by a differential scanning calorimeter (DSC). It provides things. Further, the present invention provides a rubber component comprising at least one of a natural rubber and a synthetic rubber having a ring and ball softening temperature of 100 to 140.
It is intended to provide a rubber composition containing a polyolefin having a temperature of ° C. The present invention also provides a pneumatic tire using the above rubber composition, particularly a pneumatic tire used for tread rubber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The first rubber composition of the present invention has a rubber component having a Vicat softening temperature measured under a load of 1 kg of 110 ° C. or less and a Mooney viscosity (ML _{1 + 4) at} 100 ° C. ) Is 15 or less. Vicat softening temperature of 11
If the temperature exceeds 0 ° C., the workability of the unvulcanized rubber composition is not improved. Here, the Vicat softening temperature is 1
The weight is measured according to JIS K7206-1982 when the weight is kg. If the Mooney viscosity (ML _{1 + 4} ) at 100 ° C. exceeds 15, the compatibility with rubber may be poor. The second rubber composition of the present invention is obtained by compounding a rubber component with a polyolefin having a heat of crystal fusion of 20 J / g or less as measured by a differential scanning calorimeter (DSC). Heat of crystal fusion is 20 J / g
If the ratio exceeds 1, the workability of the rubber composition is not improved.
Further, the third rubber composition of the present invention is obtained by blending a rubber component with a polyolefin having a ring and ball softening temperature of 100 to 140 ° C. Ring and ball softening temperature is 1
At temperatures other than 00 to 140 ° C, the workability of the rubber composition is not improved. Here, the ring and ball softening temperature is JIS K 220
7-1996.

[0008] Such polyolefins are not particularly limited and various ones can be used. For example, polyethylenes, polypropylenes, and higher polyolefins such as polybutenes, polypentenes, polyhexenes (having 4 or more carbon atoms). And a copolymer of different kinds of olefin monomers. Among them, poly α-olefin,
Alternatively, a homopolymer or copolymer obtained by polymerizing one or two or more olefin monomers having 2 to 8 carbon atoms is preferable. Here, as the α-olefin monomer used for the polymerization of the poly α-olefin, propylene, 1-butene, 4-
Methyl-1-pentene, 1-hexene, 1-octene,
Examples thereof include 1-decene, 1-dodecene, 1-tetradecene, and 1-octadecene. Examples of the olefin monomer having 2 to 8 carbon atoms include ethylene, propylene, butene, and octene.

As the polyolefin in the present invention, a homopolymer or a copolymer obtained by polymerizing one or more of these olefin monomers is used. Among these, a homopolymer of propylene or a copolymer of propylene and another α-olefin is particularly preferred. Examples of the copolymer include a propylene-ethylene copolymer and a copolymer of propylene and 1-butene. The polyolefins may be used alone or in combination of two or more. The amount of the polyolefin used in the present invention is not particularly limited, but is usually 0.5 to 50 parts by weight, preferably 2 to 10 parts by weight based on 100 parts by weight of the total rubber. Is done. If the amount is less than 0.5 part by weight, the Mooney viscosity (M
L _{1 + 4} , 130 ° C.) may not be obtained, and if it exceeds 50 parts by weight, the fracture resistance may be deteriorated.

Next, the rubber component is applied to both natural rubber and synthetic rubber. Examples of the synthetic rubber include isoprene rubber (IR) and butadiene rubber (B
R), 1,2-polybutadiene (1,2-BR), styrene-butadiene rubber (SBR), nitrile rubber (NB
R), chloroprene rubber (CR) butyl rubber (II
R), chlorinated butyl rubber, brominated butyl rubber, ethylene-propylene rubber (EPM) and ethylene-propylene-diene copolymer (EPDM). These rubbers may be used alone or in combination of two or more. In the rubber composition of the present invention, carbon black, a reinforcing inorganic filler such as silica or alumina, which has been conventionally used, can be used as a reinforcing filler. In the present invention, the rubber reinforcing filler is blended in an amount of 30 to 150 parts by weight based on 100 parts by weight of the rubber component. When the amount is less than 30 parts by weight, the effect of improving reinforcing properties and other physical properties is not sufficiently exhibited.
If the amount is more than the weight part, the workability and the like deteriorate. In consideration of reinforcing properties, other physical properties and workability, the amount of this component is preferably in the range of 40 to 120 parts by weight. Further, the total amount of the reinforcing inorganic filler is preferably from 70 to 80 parts by weight.

The rubber composition of the present invention may optionally contain a silane coupling agent. The silane coupling agent is not particularly limited, and a known silane coupling agent which has been conventionally used for a rubber composition can be used. The silane coupling agent is usually selected in the range of 1 to 20% by weight based on the reinforcing inorganic filler such as silica. If the amount is less than 1% by weight, the effect as a coupling agent is not sufficiently exhibited, and if it exceeds 20% by weight, gelation of a rubber component may be caused. From the viewpoints of the effect as a coupling agent and the prevention of gelation, the preferable amount of the silane coupling agent is in the range of 5 to 15% by weight. In the rubber composition of the present invention, other than the above-mentioned compounding agents, various chemicals usually used in the rubber industry, for example, vulcanizing agents, vulcanization accelerators, and the like, as long as the object of the present invention is not impaired. Process oil, anti-aging agent, anti-scorch agent, zinc white, stearic acid, etc. can be contained.

As described above, the polyolefin having a specific property blended in the rubber composition of the present invention has a relatively low molecular weight and low crystallinity, so that it has good compatibility with rubber. Since it does not contain a double bond, the vulcanizing agent is not consumed excessively and is chemically stable. Furthermore, the rubber composition of the present invention has significantly reduced compound Mooney, while suppressing deterioration in physical properties such as hardness and tan δ. In addition, since the polyolefin is in a solid form at room temperature, it is excellent in handleability and does not cause a problem of bleed-out in a molding process. Therefore, the rubber composition of the present invention can achieve both good workability and low fuel consumption.The rubber composition of the present invention is kneaded using a kneader such as a roll or an internal mixer. It is obtained by molding and vulcanization after forming, and is used for tire tread, undertread, carcass, side wall, bead part, etc., as well as for applications such as anti-vibration rubber, belt, hose and other industrial products. It can be used, and is particularly suitably used as a tread rubber for passenger car tires and bus / truck tires. The pneumatic tire of the present invention using the above rubber composition can be manufactured by a usual method.

[0013]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The evaluation of various physical properties of the unvulcanized rubber and the vulcanized rubber was measured by the following methods. (1) Mooney viscosity Mooney viscosity of the unvulcanized rubber composition [ML _{1 +} 4/130
° C] is based on JIS K6300-1994.
It was measured at 0 ° C. The Mooney viscosity [ML _{1 +} 4/100 ° C.] of the polyolefin was measured at 100 ° C. (2) Evaluation of processability 200 g of the unvulcanized rubber composition was applied using a 3 inch roll,
The winding property on a roll was observed under the conditions of a gauge of 2 mm and a temperature of 50 ° C., and evaluated by the following indexes. ◎ It wraps neatly ○ It rises slightly △ It wraps around but it often rises × It hardly winds up

(3) Tensile Properties and Hardness At room temperature, the tensile stress (M ₃₀₀ ) at 300% elongation, the strength at cutting (Tb) and the hardness are measured according to JIS K6301-199.
Measured according to 5. (5) Wear Resistance Using a Lambourn type abrasion tester, the amount of wear at a slip rate of 25% at room temperature was measured. In Tables 1 and 3, the wear resistance of Comparative Example 1 was set to 100, and in Table 2, In Table 4, the abrasion resistance of Comparative Example 3 was set to 100, and in Table 4, the abrasion resistance of Comparative Example 5 was set to 100. The larger the index, the better. (6) Dynamic characteristics Using a viscoelasticity measuring device, temperature 50 ° C, frequency 15H
It was measured at tan δ as z, shear strain 10%. tan
The smaller the δ, the lower the heat generation.

Examples 1 and 2 and Comparative Examples 1 and 2 SBR0120 [trademark, oil-extended rubber of styrene-butadiene copolymer rubber manufactured by JSR Corporation (100 parts by weight of rubber component, 37.5 parts by weight of aroma oil) 137.5)
In terms of parts by weight, the types and amounts of polyolefin and carbon black [manufactured by Tokai Carbon Co., Ltd., trademark:
Seast KH (N339)] 10 parts by weight, silica [manufactured by Nippon Silica Industry Co., Ltd., trademark: Nipsil AQ] 60 parts by weight, silane coupling agent [manufactured by Degussa, trademark: Si6
9, bis (3-triethoxysilylpropyl) tetrasulfide] 5 parts by weight, stearic acid 2 parts by weight, antioxidant 6C [N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine] 1 part by weight was blended to prepare a master batch, and 3 parts by weight of zinc white, 1.0 part by weight of a vulcanization accelerator DPG (diphenylguanidine), 1 part by weight of a vulcanization accelerator DM (dibenzothiazyl disulfide), A rubber composition was prepared by blending 1 part by weight of a vulcanization accelerator NS (Nt-butyl-2-benzothiazylsulfenamide) and 1.5 parts by weight of sulfur. In Comparative Example 1, no polyolefin was blended. The Mooney viscosity of the rubber composition was measured and vulcanized at 160 ° C. for 15 minutes, and the physical properties of the vulcanized rubber were measured. Table 1 shows the results.

[0016]

[Table 1]

(Note) * 1) PP: polypropylene, manufactured by Nippon Polychem Co., Ltd.
Trademark “Novatech PP-MG05BS” (heat of crystal fusion is 85 J / g, Mooney viscosity [ML _{1 +} 4/100 ° C.] cannot be measured at 200 or more) * 2) APAO-1: propylene / 1-butene = 62 /
38 random copolymer, manufactured by Ube Industries, Ltd., trademark “U
T2780 "(ring and ball softening temperature is 110 ° C, heat of crystal fusion is 7 J / g, Mooney viscosity [ML _{1 +} 4/100 ° C] is 0) Examples 3 and 4 and Comparative Examples 3 and 4 SBR0120 (supra) 137 37 parts by weight of carbon black (described above), 37 parts by weight of silica (described above), and silane coupling agent "Si69" (described above) with respect to 0.5 parts by weight.
5 parts by weight, 1 part by weight of stearic acid, and 1 part by weight of an antioxidant 6C (described above) are blended to prepare a master batch. Further, 3 parts by weight of zinc white and vulcanization accelerator DPG (described above) are 1.0. Parts by weight, vulcanization accelerator DM (described above) 1 part by weight, vulcanization accelerator NS
A rubber composition was prepared by blending 1 part by weight (described above) and 2 parts by weight of sulfur. Comparative Example 3 did not contain a polyolefin. While measuring the Mooney viscosity of the rubber composition,
Vulcanization was performed at 160 ° C. for 15 minutes, and the physical properties of the vulcanized rubber were measured. Table 2 shows the results.

[0018]

[Table 2]

Examples 5 to 7 In Example 2, the type of polyolefin was changed to
Except for using the polyolefins shown in the table,
Performed in the same manner as in Example 2. The results are shown in Table 3. Example 6 was completely the same as Example 2.

[0020]

[Table 3]

(Note) * 3) APAO-2: Propylene homopolymer (ring and ball softening temperature: 138 ° C., heat of crystal fusion: 20 J / g, Mooney viscosity [ML _{1 +} 4/100 ° C.]: 8) * 4 ) APAO-3: propylene / ethylene = 85/1
5 random copolymer, manufactured by Nippon Polychem Co., Ltd., trade name “UT2535” (ring and ball softening temperature is 129 ° C., heat of crystal fusion is 10 J / g, Mooney viscosity [ML _{1 +} 4/100]
° C] is 2)

Examples 8 and 9 and Comparative Examples 5 and 6 BR01 (Cis-1,4-manufactured by JSR Corporation)
For 100 parts by weight of a rubber component consisting of 70 parts by weight of polybutadiene) and 30 parts by weight of natural rubber, polyolefin and carbon black (described above) of the kind and amount shown in Table 1 were used.
0 parts by weight, 40 parts by weight of silica (described above), 4 parts by weight of silane coupling agent "Si69" (described above), aroma oil 2
6.25 parts by weight, stearic acid 2 parts by weight, antioxidant 6C
(See above) 1 part by weight is blended to prepare a master batch,
Further, 3 parts by weight of zinc white, vulcanization accelerator DPG (described above) 0.8
A rubber composition was prepared by mixing 1 part by weight of a vulcanization accelerator DM (described above), 1 part by weight of a vulcanization accelerator NS (described above), and 1.5 parts by weight of sulfur. The Mooney viscosity of the rubber composition was measured and vulcanized at 160 ° C. for 15 minutes, and the physical properties of the vulcanized rubber were measured. Table 4 shows the results.

[0023]

[Table 4]

The above results indicate that the rubber composition of Example 1 in which the specific polyolefin according to the present invention was blended exhibited a large decrease in Mooney viscosity as compared with Comparative Example 1, and despite that, the rubber composition was 300 % Modulus, hardness, tan
As for δ (low fuel consumption), it can be seen that good performance is maintained in all cases.

[0025]

According to the present invention, a rubber composition in which both low heat generation and workability are improved at a high level without increasing the modulus or hardness by 300% by blending a polyolefin having a specific property. This is particularly preferably used for a tire member, particularly for a tire tread rubber.

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Claims (7)

[Claims] 1. A rubber component comprising at least one of natural rubber and synthetic rubber has a Vicat softening temperature measured under a load of 1 kg of 110 ° C. or less and a Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of 15 or less. A rubber composition comprising the following polyolefin. 2. A rubber composition comprising a rubber component comprising at least one of natural rubber and synthetic rubber, and a polyolefin having a heat of crystal fusion of 20 J / g or less as measured by a differential scanning calorimeter (DSC). object. 3. A rubber component comprising at least one of natural rubber and synthetic rubber, having a ring and ball softening temperature of 100 to 140.
A rubber composition comprising a polyolefin having a temperature of ° C. 4. The rubber composition according to claim 1, wherein the polyolefin is a poly-α-olefin. 5. The rubber composition according to claim 1, wherein the polyolefin is obtained by polymerizing one or two or more olefin monomers having 2 to 8 carbon atoms. 6. A pneumatic tire using the rubber composition according to any one of claims 1 to 5. 7. A pneumatic tire using the rubber composition according to claim 1 for a tread rubber.