JP3090794B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire,
More specifically, the present invention relates to a pneumatic tire in which the uniformity of the tire is improved by suppressing the curvature of a member generated after extruding a sidewall or a rubber chafer during the production of the pneumatic tire.

[0002]

BACKGROUND OF THE INVENTION Pneumatic tires, mainly intended to protect the Size Lee Doworu rubber layer covering the sides of the tire protection carcass main purpose, the outer circumference of the bead portion during the desorption of the rim from the wound And a rubber chafer.

In order to reduce the molding process, these sidewalls and rubber chafers are usually extruded at the same time, or extruded separately, and combined together immediately after extrusion, so-called doubling. Have been.

[0004]

However, since the extruded cross-sectional shape of the sidewall portion is asymmetrical in the left and right directions, a difference in the shearing speed at the time of extrusion causes a shrinkage difference, and after cooling, a curvature in the extrusion direction occurs.
Therefore, when such a member is cut, and the tire is molded and vulcanized, the uniformity of the product tire is reduced due to the large displacement of the joint, the vibration of the vehicle is increased, and the steering stability is reduced. It will cause a problem that intends island.

It has been empirically known that such a problem can be prevented to some extent by changing the speed at the time of extrusion and the tapered shape of the mouth portion, but the effect is completely satisfactory. Was not.

SUMMARY OF THE INVENTION It is an object of the present invention to significantly suppress the curvature that occurs after the extrusion of a sidewall or rubber chafer member of a pneumatic tire, and at the same time to reduce the temperature dependence of physical properties such as modulus after vulcanization. Accordingly, it is an object of the present invention to provide a pneumatic tire having a significantly improved uniformity.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a syndiotactic-1,2- having a specific melting point is added to a rubber component system in which isoprene-based rubber is present. Polybutadiene (hereinafter “syn-1,
2PB ") is used for the sidewall and / or rubber chafer, whereby the curving of the member after extrusion of the member is greatly suppressed, and the crystalline resin syn- but despite being added, the vulcanization of the tire
1,2PB is completely compatible with the isoprene-based rubber or partially compatible and co-vulcanized to obtain syn-1 and vulcanized syn-1
The present inventors have found that the crystallinity of 2PB is greatly reduced, the temperature dependence of the properties of the vulcanized rubber is reduced, and the above object can be achieved, and the present invention has been completed.

Namely, the pneumatic tire of the present invention, the rubber Ingredients 1 comprising natural rubber and / or isoprene rubber
A rubber composition in which 3 to 30 parts by weight of syn-1,2PB having a melting point in the range of 60 to 110 ° C is used for the sidewall and / or the rubber chafer with respect to 00 parts by weight. Is what you do.

Syn-1,2P used in the present invention
As a polymerization catalyst B, a soluble cobalt, such as cobalt octoate, cobalt 1- Nafute ne over preparative, cobalt benzoate, an organic aluminum compound, such as trimethyl aluminum, triethyl aluminum, tributyl aluminum, triphenyl aluminum, Two
Mention may be made of a catalyst system such as that consisting of a vulcanized carbon. As a specific polymerization method, the methods described in JP-B-53-39917, JP-B-54-5436 and JP-B-56-18005 can be used, but the syn-1,2PB used in the present invention is used. The polymerization method of is not particularly limited to the methods described in these.

The method of mixing the rubber composition according to the present invention is not particularly limited, and the same effect can be obtained by a wet blending method in a solvent or a dry blending method using a Banbury mixer or the like.

The rubber composition according to the present invention contains an inorganic filler such as carbon black and silica, a softener such as aroma oil and spindle oil, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanizing agent. It goes without saying that a proper amount of a compounding agent usually compounded such as an accelerating aid can be appropriately compounded.

[0012]

The present inventors have surprisingly found that the rubber composition for a sidewall and / or a rubber chafer of a pneumatic tire has a melting point of 60 to 110 ° C., preferably 100 to 100 parts by weight of a rubber component. Syn-1,2PB in the range of 60 to 100 ° C, more preferably 60 to 90 ° C
It has been found that by blending 3 to 30 parts by weight, the bending of the extruded member is largely prevented, and the uniformity of the product tire can be improved.

[0013] This is presumably because the addition of syn-1 and 2PB increases the green modulus and acts against deformation caused by shrinkage after cooling. In fact, the melting point of syn-1,2PB is 60 ° C.
If it is lower than this, no increase in green modulus was observed, and no effect of preventing the extruded member from bending was observed.

The tire has a vulcanization temperature of 140 to 1
At 80 ° C., syn-1,2 PB is completely compatible with polyisoprene rubber or partially compatible and co-vulcanized, so that the crystallinity of vulcanized syn-1,2 PB is significantly reduced. Therefore, the temperature dependence of the properties of the vulcanized rubber can be kept low. However, if the melting point of syn-1 and PB is higher than 110 ° C., the syn-
Due to the 1,2PB crystal, the temperature dependency of the modulus increases, and the material becomes unsuitable as a tire material.

The reason why the compounding amount of syn-1,2PB is defined in the above-mentioned range is that if the compounding amount is less than 3 parts by weight, the green modulus of the unvulcanized rubber is relatively low, and the extruded member This is because a sufficient effect of preventing bending of the rubber composition cannot be obtained, and the uniformity of the product tire is not sufficiently improved. On the other hand, if it is more than 30 parts by weight, the bending fatigue resistance of the rubber composition is inferior.

In the present invention, as described above, syn-
In consideration of the compatibility with 1,2PB, the presence of an isoprene-based rubber as a rubber component is essential, and it is preferable that the rubber be present in an amount of 50 parts by weight or more. However, even if a conjugated diene rubber such as butadiene rubber and / or an ethylene-α-olefin non-conjugated diene rubber is blended, the effects of the present invention are not lost.

As described above, the rubber composition for the sidewall and / or rubber chafer of the pneumatic tire of the present invention has a relatively high green modulus of the unvulcanized rubber, so that the extruded member has a curved shape. And syn-1 and 2PB are completely compatible with the polyisoprene rubber at the time of vulcanization or are partially compatible and co-vulcanized. The crystallinity of -1,2PB is greatly reduced. Therefore, according to the present invention, the uniformity of the tire can be significantly improved.

[0018]

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. First, various syn-
A 1,2PB resin was prepared. In a 2-liter autoclave in which air was replaced with nitrogen gas, dehydrated benzene 760 was added.
cc was added, and 74 g of 1,3-butadiene was dissolved. To this, cobalt octoate 1 mmol (concentration 1 mmol / cc)
Was added, and after 1 minute, 2 mmol of triethylaluminum (a benzene solution having a concentration of 1 mmol / cc) was added thereto, followed by stirring, and then 1 minute later, the amount of acetone shown in Table 1 below was added. One minute later, carbon disulfide 0.6m
mol (a benzene solution having a concentration of 0.3 mmol / cc) was added thereto, followed by stirring at 10 ° C. for 60 minutes to polymerize 1,3-butadiene.

[0019] The resulting syn-1,2 PB resin product solution was added 2,4 Jitasha butyl -p- cresol 0.75 g. Then, 1000 cc of methanol
Then, syn-1 and 2PB resin production liquid were added thereto, and syn-
The 1,2PB resin was precipitated. This syn-1,2
The PB was further washed with methanol, filtered, and then dried in vacuum. The melting points of the obtained syn-1 and 2PB are also shown in Table 1 below.

[0020]

[Table 1]

Using the above various syn-1 and 2PB, a rubber composition for a sidewall and / or a rubber chafer was prepared according to the formulation shown in Table 2 below. In addition, the rubber components in the table were adjusted to be 100 parts by weight in total.

[0022]

[Table 2] Compounding agent parts by weight butadiene rubber (BR) ¹⁾ Variable natural rubber (NR) Variable syn-1,2PB Variable Carbon black (FEF) 50 Aroma oil 15 ZnO 5 Stearic acid 2 Antioxidant (810NA) ²⁾ 3.5 Wax (Santite E) ³⁾ 2 Vulcanization accelerator (NBS) ⁴⁾ 0.4 Vulcanization accelerator (DM) ⁵⁾ 0.3 sulfur 1.5 1) BR012 manufactured by Nippon Synthetic Rubber Co., Ltd. ) 4-N-phenyl-N'-isopropyl-p-phenylenediamine 3) Microcrystalline wax manufactured by Seiko Chemical Co., Ltd. 4) N-oxydiethylene-2-benzothiazolesulfenamide 5) dibenzothiazyl disulfide

The rubber compositions shown in Table 2 were vulcanized at 165 ° C. for 15 minutes to prepare various test pieces. Further, such a rubber composition is used for a sidewall of a tire and / or a rubber chafer and has a size PSR185 / 70.
Various test tires of SR14 were prepared, and the uniformity of the tires was evaluated. In this example, various measurements were performed according to the following methods.

1) Melting point Using a differential thermal analyzer (DSC200) manufactured by Seiko Co., Ltd., the temperature was lowered from 20 ° C. to 10 ° C. at a nitrogen flow rate of 20 ml / min.
/ Min at a heating rate of / min.

2) Breaking rate due to bending fatigue After performing a demashing test for 100 hours, the breaking rate (%) of the test piece was determined by the following equation. Rupture rate (%) = ｛(fracture length of test piece after bending fatigue) /
(Length of initial test piece)｝ × 100

3 ) Modulus temperature change rate Measurement was performed according to JIS K6301, and the modulus was determined by the following equation. Modulus temperature change rate (%) = ｛(100% elongation modulus at 100 ° C.) /
(Modulus at 100% elongation at 50 ° C.)｝ × 10
0

4 ) Uniformity According to the method defined in JASO C607-74.
That is, when a load is applied to the tire on the cornering test machine and the tire is rolled while maintaining a constant radius, the load varies. This variation (total amplitude) is called radial force variation (RFV), and this RFV
The values were each measured. The difference from Comparative Example 1 was taken as the RFV value, and evaluated according to the following criteria. A: 15% or more improvement B: 10 to 15% or more improvement C: 5 to 10% or more improvement D: No effect

The results obtained are shown in Tables 3 and 4 below. Table 3 shows the rubber composition shown in Table 2 as the sidewall rubber, Table 4 (except for Example 11) shows the rubber composition in the rubber chafer, and Example 11 in Table 4 shows the rubber composition in the rubber composition. The results of applying the material to both a sidewall rubber and a rubber chafer are shown.

[0029]

[Table 3]

[0030]

[Table 4]

First, Comparative Examples 1 to 3 and Examples 1 to 3 shown in Table 3 and Comparative Examples 7 to 9 and Example 6 shown in Table 4
The following was confirmed from ８8. syn-1,2P
If the melting point of B is lower than 60 ° C., no effect is observed on the improvement of the uniformity of the tire.
When the temperature is higher than 0 ° C., although there is an effect on the improvement of the uniformity, the temperature dependency of the modulus is larger than that of Comparative Example 1, and the flex fatigue is inferior.

Next, Examples 4 and 5 and Comparative Examples 4 and 5 shown in Table 3 and Examples 9 and 10 and Comparative Example 1 shown in Table 4
From 0 and 11, syn is based on 100 parts by weight of the rubber component.
It was confirmed that there was an optimum range for the blending number of -1,2PB. That is, if the amount is less than 3 parts by weight, no effect on the improvement of uniformity is recognized, while if it exceeds 30 parts by weight, the temperature dependency of the modulus increases and the bending fatigue resistance is poor. It became a thing.

From Comparative Example 6 shown in Table 3, syn
It was confirmed that, in the case where -1,2PB was blended, the temperature dependency of the modulus tended to be significantly increased without the isoprene-based rubber.

As can be seen from Examples 1 to 5 shown in Table 3 and Examples 6 to 10 shown in Table 4, sy in the specific melting point range was used.
When a rubber composition containing a specific amount of n-1,2PB is used for either the sidewall or the rubber chafer, the uniformity is significantly improved, but as can be seen from Example 11 shown in Table 4, When the rubber composition was used for both the side wall and the rubber chafer, the effect of further improving the uniformity was obtained.

[0035]

As described above, in the pneumatic tire of the present invention, the sidewall and / or
Alternatively, as a rubber composition for a rubber chafer, a rubber component having an isoprene-based rubber is added to a rubber component having a specific melting point.
By using a rubber composition in which a specific amount of yn-1,2PB is blended, the curvature generated after the extrusion of the side wall or the member of the rubber chafer is largely suppressed, and at the same time, the temperature dependence of physical properties such as modulus after vulcanization. The effect that the uniformity of the tire is greatly improved is obtained by reducing the performance.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI C08L 9/00 C08L 9/00 (58) Field surveyed (Int.Cl. ⁷ , DB name) C08L 7/00 B29D 30/06 B29D 30/72 B60C 1/00 C08L 9/00

Claims (1)

(57) [Claims] Respect 1. A natural rubber and / or rubber component per 100 parts by weight comprising isoprene rubber, mp 60-1
A pneumatic tire, wherein a rubber composition containing 3 to 30 parts by weight of syndiotactic-1,2-polybutadiene having a temperature of 10 ° C is used for a sidewall and / or a rubber chafer.