JPH11302458A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition with improved heat resistance and a tire with improved durability using the same by incorporating a compound having plural ester groups in the molecule and controlling the variation in the dynamic storage modulus of elasticity within a specific temperature range below a specific value. SOLUTION: This composition comprises 100 pts.wt. of a rubber component such as natural rubber, styrene-butadiene rubber or the like, 0.1-20 pts.wt. of at least one compound having at least two ester groups in one molecule selected from di(tetramethylolmethane)pentamethacrylate, di(tetramethylolmethane) trimethacrylate, trimethylolpropane trimethacrylate and the like as a deterioration inhibitor and proper quantities of crosslinking agents, crosslinking accelerators, softening agents, reinforcing fillers or the like, and has a variation in the dynamic storage modulus of elasticity of 3.0 MPa or lower at 170-200 deg.C. This deterioration inhibitor is incorporated into a rubber composition for a rubber reinforcing layer of a side wall portion of a tire or for a bead filler and is effective to improve durability of the side wall portion in particular.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition and a pneumatic tire, and more particularly to a rubber composition having improved heat resistance and a pneumatic tire using the rubber composition.

[0002]

2. Description of the Related Art Conventionally, a reinforcing layer of a rubber composition alone or a composite of a rubber composition and a fiber is provided to increase the rigidity of a sidewall portion. However, the rubber compositions used in these, especially, running under reduced internal pressure due to tire puncture, so-called run-flat running, when the temperature reaches 200 ℃ or more, vulcanization, etc. There is a tendency that the crosslinked portion obtained by the above or the polymer itself constituting the rubber component is cut. As a result, the elastic modulus decreases, so that the flexure of the tire increases and heat generation proceeds, or the breaking limit of the rubber decreases, and as a result, the tire will fail relatively early.

[0003] As one of means for delaying the failure as much as possible, the elastic modulus of the rubber composition to be used is increased as much as possible by changing the compounding, or its tan δ
There is a method to reduce the heat generation of the rubber composition itself by setting as small as possible, but there is a limit to the approach from the compounding side, and in order to secure a certain durable distance, a rubber reinforcing layer and a bead filler are required. At present, there is no other way but to increase the weight, which leads to worse riding comfort, lower noise level, and higher weight during normal driving.

[0004]

Accordingly, an object of the present invention is to provide a rubber composition having improved heat resistance, and to provide the rubber composition with a pneumatic tire, particularly for reinforcing a sidewall portion. An object of the present invention is to provide a pneumatic tire with improved durability by using the rubber composition of the present invention or the rubber composition of a bead filler.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on various compounding chemicals in order to increase the heat resistance of a rubber composition. As a result, the heat resistance of the rubber composition was greatly increased by compounding a specific compound. And found that the present invention was completed.

That is, the present invention has the following configuration. (1) A rubber composition characterized in that the dynamic storage modulus has a fluctuation of 170 MPa or less from 170 ° C to 200 ° C. (2) The rubber composition according to (1), wherein a compound having two or more ester groups in one molecule is blended. (3) The rubber composition according to (2), wherein the compound having two or more ester groups in one molecule is acrylate or methacrylate. (4) The compound according to (2), wherein the compound having two or more ester groups in one molecule is a polyvalent ester of a polyhydric alcohol and acrylic acid or methacrylic acid.
Or, the rubber composition according to (3). (5) The polyhydric alcohol constituting the compound having two or more ester groups in one molecule is at least one selected from the group consisting of tetramethylolmethane, trimethylolpropane, and a multimer thereof. The rubber composition according to any one of the above (2) to (4), wherein (6) The rubber composition according to any one of (2) to (5), wherein the polyhydric alcohol is a dimer of tetramethylolmethane or trimethylolpropane. (7) The compound according to (2), wherein the compounding amount of the compound having two or more ester groups in one molecule is 0.5 to 20 parts by weight based on 100 parts by weight of the rubber component.
The rubber composition according to any one of (1) to (6). (8) A pneumatic tire using any one of the rubber compositions according to (1) to (7) as a bead filler rubber. (9) In a tire in which a sidewall portion is reinforced by a rubber reinforcing layer, the rubber composition of the rubber reinforcing layer includes the rubber composition described in any one of (1) to (7). Pneumatic tires. (10) The pneumatic tire according to any one of (8) and (9), wherein the tire is a safety tire.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention must have a dynamic storage modulus in a temperature range from 170 ° C. to 200 ° C. of 3.0 MPa or less. If this variation exceeds 3.0 MPa, the temperature dependence of the elastic modulus of the rubber composition becomes high, and the physical properties at high temperatures are inevitably reduced.

In the present invention, a compound having two or more ester groups in one molecule is preferably compounded in the rubber composition as a deterioration inhibitor.

The compound having two or more ester groups in one molecule is not particularly limited, but may be acrylate or methacrylate, especially a polyhydric ester of polyhydric alcohol and acrylic acid or methacrylic acid. preferable.

Examples of polyhydric alcohols include alkylene glycols such as methylene glycol, ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol and the like and multimers thereof, and further, methylol-substituted products thereof and ketoroses such as erythritol. Compounds containing a polyalkylene oxide group such as polyalkoxyphenylpropane, polyesters having two or more alcoholic hydroxyl groups, or oligoesters, and among them, particularly preferred are methylol-substituted alkylene glycols, And its multimers.

Specific examples of the compound having two or more ester groups in one molecule include 1,3-butylene glycol diacrylate, 1,5-pentanediol diacrylate, neopentyl glycol diacrylate, 1,6
-Hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate polyethylene glycol diacrylate, polypropylene glycol diacrylate, bis (4-acryloxy) polyethoxyphenylpropane oligoester diacrylate, pentaerythritol triacrylate , Trimethylolpropane triacrylate, tetramethylol methane tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, oligoester polyacrylate, dipropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, dimethyl Examples thereof include (tetramethylolmethane) pentamethacrylate and di (tetramethylolmethane) trimethacrylate. Among them, particularly preferable are di (tetramethylolmethane) pentamethacrylate, di (tetramethylolmethane) trimethacrylate, and trimethylol. It is propane trimethacrylate. These compounds may be used alone or in combination of two or more.

The compounding amount of the compound having two or more ester groups in one molecule is preferably 0.5 to 20 parts by weight, more preferably 1.0 to 15 parts by weight. If the amount is less than 0.5 part by weight, the effect of the present invention cannot be sufficiently obtained, and even if the amount exceeds 20 parts by weight, the effect corresponding to the amount cannot be obtained.

The degradation inhibitor preferably used in the present invention is 17
Below 0 ° C., it is substantially inert to vulcanization, and therefore does not participate in crosslinking at the vulcanization temperature (usually around 160 ° C.), and the elastic modulus does not increase more than the design target. On the other hand, when the temperature of the rubber composition is 170 ° C. or higher, the deterioration of the rubber starts, and the cross-linking points and the breaking of the polymer chain start to occur.
On the other hand, re-crosslinking of the polymer by the deterioration inhibitor proceeds, so that a decrease in elastic modulus is suppressed, and as a result, heat generation is suppressed even at high temperatures.

The rubber component used in the present invention is not particularly limited and can be selected from those usually used, such as natural rubber (NR), synthetic polyisoprene (IR), polybutadiene (BR), and the like. Styrene-butadiene copolymer (SBR), butyl rubber (IIR),
Ethylene-propylene-diene terpolymer (EPD
M) and the like. These may be used alone or as a mixture of two or more.

The rubber composition of the present invention may contain, in addition to the above components, compounding agents such as a crosslinking agent, a crosslinking accelerator, an antioxidant, a softening agent, a reinforcing filler, and an inorganic filler, which are generally used in the rubber industry. They can be appropriately blended. Further, the rubber composition of the present invention may be a composite with particles, fibers, cloths and the like of various materials.

The pneumatic tire of the present invention is preferably
It is necessary that the bead filler rubber or the rubber reinforcing layer provided on the side wall portion contains the above rubber composition.

At the time of running the tire, particularly at the time of run-flat running, the deformation of the tire due to the load becomes very large, and particularly, the heat generated by the deformation at the sidewall portion is large.
Failure of the sidewall portion is a major problem.

As described above, the rubber composition of the present invention can maintain the elastic modulus according to the design target at a low temperature, so that the riding comfort and noise due to the increase in the elastic modulus during normal driving can be maintained. Substantially no level degradation occurs. On the other hand, even if the temperature of the rubber composition becomes 170 ° C. or higher, a decrease in the elastic modulus is suppressed due to a large deformation due to a puncture of the tire, so that heat generation at a high temperature is suppressed, and the durability of the tire is improved. be able to.

Therefore, such a compound is added to a tire,
Preferably, by being compounded with the rubber composition of the rubber reinforcing layer or bead filler of the sidewall portion of the tire,
In particular, the durability of the tire sidewall portion can be improved, and as a result, for example, the run flat running distance can be significantly increased.

[0020]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited thereto without departing from the gist of the present invention. Parts and% in Examples are based on weight unless otherwise specified. Various measurements were made according to the following methods.

(1) The viscoelasticity of the rubber composition was determined by measuring the dynamic storage elastic modulus (E ') of a 5 mm wide and 20 mm long sample cut from a 2 mm thick slab sheet which had been vulcanized at 160 ° C. for 12 minutes. And loss tangent (tan δ) to Toyo Seiki Co., Ltd.
Using a spectrometer manufactured at 20 ° C. to 25 ° C. under measurement conditions of an initial load of 160 g, a dynamic strain of 1%, and a frequency of 52 Hz.
The measurement was performed at a temperature rising rate of 3 ° C./sec in a temperature range of 0 ° C.
When tan δ is large, the heat generation of the rubber composition is large.

Tire run flat durability Rim assembly at an internal pressure of 3.0 kg / cm ² , left at room temperature of 38 ° C. for 24 hours, then unplugged the valve core and reduced the internal pressure to 0 kg / cm ²
in the cm ^2, load 570kg, speed of 89km / hr
s, a drum running test was performed under the conditions of a room temperature of 38 ° C. The running distance until the occurrence of a failure at this time was defined as run flat durability, and was represented by an index with the control being 100. The larger the index, the better the run flat durability.

According to the basic formulation in Table 1, the compounds in Table 2 were blended to prepare a rubber composition, and the dynamic storage modulus E 'and tan δ at the initial stage and after heat aging were measured. Table 2 shows the results.

[0024]

[Table 1]

[0025]

[Table 2] Deterioration inhibitor 1: Trimethylolpropane trimethacrylate 2: KARAYAD D310 manufactured by Nippon Kayaku Co., Ltd. 3: KAYARAD D330 manufactured by Nippon Kayaku Co., Ltd. 4: KAYARAD DPHA manufactured by Nippon Kayaku Co., Ltd.

As can be seen from Table 2, the rubber composition of the present invention containing a deterioration inhibitor has a dynamic storage modulus of 170 ° C.
Less temperature dependence at 200 ° C.

Further, a radial tire for passenger cars of size 225 / 60R16 was manufactured by a conventional method using each rubber composition as the rubber composition of the rubber reinforcing layer, and a durability test was conducted. Table 3 shows the results.

[0029]

[Table 3]

As can be seen from Table 3, it can be seen that the use of the rubber composition of the present invention for the rubber reinforcing layer on the sidewall portion of the pneumatic tire can improve the run flat durability.

Next, each rubber composition was used not only for the rubber reinforcing layer but also for the bead filler rubber to obtain a tire having a size of 22%.
A 5 / 60R16 radial tire for a passenger car was manufactured by a standard method and subjected to a durability test. Table 4 shows the results.

[0032]

[Table 4]

As can be seen from Table 4, the use of the rubber composition of the present invention as a bead filler further improves the run flat durability regardless of the type of each rubber composition.

[0034]

[Effect] 170 ° C. to 20 of dynamic storage modulus of the rubber composition
By suppressing the fluctuation at 0 ° C. within 3.0 MPa, the temperature dependency of the physical properties of the rubber composition can be reduced, and the rubber composition can be used as a rubber reinforcing layer in a pneumatic tire, particularly, in a sidewall portion. By using it as a bead filler, the durability of the tire can be significantly improved.

Claims (10)

[Claims] 1. A dynamic storage modulus of 170 ° C. to 200 ° C.
The rubber composition, wherein the variation up to 3.0 MPa is 3.0 MPa or less. 2. The rubber composition according to claim 1, wherein a compound having two or more ester groups in one molecule is compounded. 3. The rubber composition according to claim 2, wherein the compound having two or more ester groups in one molecule is acrylate or methacrylate. 4. The compound according to claim 2, wherein the compound having two or more ester groups in one molecule is a polyhydric ester of a polyhydric alcohol and acrylic acid or methacrylic acid. The rubber composition as described in the above. 5. The polyhydric alcohol constituting the compound having two or more ester groups in one molecule is at least one selected from the group consisting of tetramethylolmethane, trimethylolpropane, and a multimer thereof. The rubber composition according to any one of claims 2 to 4, wherein the rubber composition is provided. 6. The rubber composition according to claim 2, wherein the polyhydric alcohol is a dimer of tetramethylolmethane or trimethylolpropane. 7. The compound according to claim 1, wherein the compounding amount of the compound having two or more ester groups in one molecule is 0.5 to 20 parts by weight based on 100 parts by weight of the rubber component. 7. The rubber composition according to any one of items 2 to 6. 8. A pneumatic tire using the rubber composition according to any one of claims 1 to 7 for a bead filler rubber. 9. A tire whose sidewall portion is reinforced by a rubber reinforcing layer, wherein the rubber composition of the rubber reinforcing layer contains the rubber composition according to any one of claims 1 to 7. A pneumatic tire characterized by the following. 10. The pneumatic tire according to claim 8, wherein the tire is a safety tire.